DOI: 10.1002/chem.201402328
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& Porphyrinoids
Cross-Conjugated Hexaphyrins and Their Bis-Rhodium Complexes Koji Naoda,[a] Young Mo Sung,[b] Jong Min Lim,[b] Dongho Kim,*[b] and Atsuhiro Osuka*[a]
ing upon the reaction conditions. Both 12 and 13 are planar owing to bis-rhodium metalation. Although complex 12 bears two meso-OCH groups at the long sides and is quinonoidal and nonaromatic in nature, complex 13 bears 3,5-ditert-butyl-4-hydroxyphenyl and OCH groups and exhibits a moderate diatropic ring current despite its cross-conjugated electronic circuit. The diatropic ring current increases upon increasing the solvent polarity, most likely due to an increased contribution of an aromatic zwitterionic resonance hybrid.
Abstract: A cross-conjugated hexaphyrin that carries two meso-oxacyclohexadienylidenyl (OCH) groups 9 was synthesized from the condensation of 5,10-bis(pentafluorophenyl)tripyrrane with 3,5-di-tert-butyl-4-hydroxybenzaldehyde. The reduction of 9 with NaBH4 afforded the Mçbius aromatic [28]hexaphyrin 10. Bis-rhodium complex 11, prepared from the reaction of 10 with [{RhCl(CO)2}2], displays strong Hckel antiaromatic character because of the 28 p electrons that occupy the conjugated circuit on the enforced planar structure. The oxidation of 11 with 2,3-dichloro-5,6-dicyano-1,4benzoquinone (DDQ) yielded complexes 12 and 13 depend-
Introduction Meso-alkenylidenyl-substituted porphyrins have attracted considerable attention in view of their unique electronic and structural properties that arise from their quinonoidal cross-conjugated networks.[1] Representative examples include oxacyclohexadienylidene(OCH)-substituted porphyrins, dicyanomethylidenyl-substituted porphyrins,[1a–c] dithiomethylidenyl substituted porphyrins,[1d,e] and core-modified diethoxycarbonylmethylidenyl-substituted porphyrins.[2a,c] Tetrakis-OCH-substituted porphyrin 1 demonstrates solvatochromism,[3a] anion binding,[3a–c] O2 reduction capability,[3d,e] and reversible redox interconversions.[3b,f] Further recent reports on the application of 1 and related porphyrins include sensors for trace water[4a] or acid–base equilibria[4b] and hosts for chiral guest molecules.[4c] These latest reports highlight the great promise that such porphyrinoids show for acting as nanoarchitectonic sensors with a diverse range of physical-detection modes.[5] We also reported a tris(3,5-di-tert-butyl-4-hydroxyphenyl)-substituted subporphyrin and its oxidized subporphyrin 2 as the first examples of meso-OCH-substituted subporphyrins (Scheme 1),[6] which showed interesting deprotonation behavScheme 1. 3,5-Di-tert-butyl-4-hydroxyphenyl-substituted quinonoidal porphyrin 1 and subporphyrin 2. Redox interconversions of 1) [26]- and [28]hexaphyrins 3 and 4 and 2) bis-rhodium complexes 5 and 6.
[a] K. Naoda, Prof. A. Osuka Department of Chemistry Graduate School of Science, Kyoto University Sakyo-ku, Kyoto 606-8502 (Japan) E-mail: [email protected]
ior. Interestingly, upon deprotonation, 2 changed from dark green to vivid blue, with the deprotonated form exhibiting a planar extended structure with almost C3 symmetry. In contrast, meso-alkenylidene-substituted expanded porphyrins have been scarcely studied, except for core-modified analogues.[2b–e] In recent years, expanded porphyrins have emerged as a new class of porphyrinoid that possess larger conjugated
[b] Y. M. Sung, J. M. Lim, Prof. Dr. D. Kim Spectroscopy Laboratory for Functional p-Electronic Systems and Department of Chemistry Yonsei University, Seoul 120-749 (Korea) E-mail: [email protected] Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201402328. Chem. Eur. J. 2014, 20, 1 – 9
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Full Paper networks.[7] Although expanded porphyrins allow the realization of various p-conjugated electronic systems, such as Hckel aromatic and antiaromatic, Mçbius aromatic and antiaromatic, and stable-radical molecules,[8] the potential of expanded porphyrins has not been fully exploited and the search for expanded porphyrins with novel electronic states continues. Different from porphyrins, expanded porphyrins are structurally and electronically flexible. As a prime example, [26]hexaphyrin Scheme 2. Synthesis of hexaphyrins 9 and 10. MSA = methanesulfonic acid. 3, a typical Hckel aromatic molecule with a rectangular shape, is reduced upon treatment with NaBH4 to afford the twisted Mçbius aromatic [28]hexaphyrin 4 accompanied by large structural changes.[8c] In contrast, the corresponding rhodium complexes 5 and 6 are structurally rigid and display Hckel aromatic and antiaromatic characteristics, respectively, thus simply reflecting the numbers of p electrons that occupy their planar conformations (Scheme 1).[9] Herein, we report the synthesis of OCH-substituted hexaphyrins and demonstrate how the incorporation of meso-alkenylidene motifs into the hexaphyrin framework alters and influences the electronic properties. Cross-conjugated quinonoidal hexaphyrin 9 that bears two OCH groups has been shown to be reduced to the Mçbius aromatic [28]hexaphyrin 10 with two 3,5-di-tert-butyl-4-hydroxyphenyl groups. In addition, bis-rhodium metalation was accomplished for this quinonoidal hexaphyrin system, thus allowing the formation of three planar bis-rhodium complexes 11– 13, which bear zero, two, and one OCH groups, respectively. Bis-rhodium complex 13 exhibits a moderate diatropic ring current despite its cross-conjugated electronic circuit. Figure 1. X-ray crystal structure of 9. Top: perspective view. Bottom: side view. The thermal ellipsoids have been scaled to the 50 % probability level. Hydrogen atoms, except for NH, have been omitted for clarity. Dashed lines represent hydrogen bonds.
Results and Discussion With the goal of synthesizing bis(3,5-di-tert-butyl-4-hydroxyphenyl)-substituted [26]hexaphyrin in mind, condensation of tripyrromethane 7 with 3,5-di-tert-butyl-4-hydroxybenzaldehyde (8) was attempted in the presence of a catalytic amount of methanesulfonic acid at 0 8C followed by oxidation with 2,3dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in situ. The crude material was subjected to chromatography on silica gel to yield the quinonoidal hexaphyrin 9 in 17 % yield (Scheme 2). High-resolution electrospray-ionization time-of-flight (HR-ESITOF) mass-spectrometric measurement showed the parent-ion peak of 9 at m/z 1535.4026 (m/z calcd for [M + H] + : 1535.4062). The 1H NMR spectrum of 9 displays three doublet signals due to the outer b-protons in a range of d = 6.46–7.02 ppm and a singlet signal at d = 14.1 ppm due to the inner-NH proton, thus suggesting a nonaromatic nature. The electronic absorption spectrum of 9 in CH2Cl2 shows a band at l = 359 nm, but neither a Soret-like nor Q-like band is observed (Figure 4). The &
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structure of 9 has been revealed by X-ray diffraction studies to be a dumbbell shape stabilized by intramolecular hydrogen bonds (Figure 1). The average C=O bond length of the 3,5-ditert-butyl-4-hydroxyphenyl group is 1.234 , which is in line with a quinonoidal-type structure. Reduction of 9 with NaBH4 proceeded quantitatively to afford [28]hexaphyrin 10 (Scheme 2). The 1H and 19F NMR spectra of 10 are too broad for structural assignment at room temperature but become relatively sharp at low temperature so that signals owing to the pyrrolic b-protons and the inner bprotons are displayed in the approximate ranges of d = 6.0–9.0 and d = 1.0–0.0 ppm, respectively, thus implying an aromatic character. The 19F NMR spectrum of 10 indicates the presence of several conformers, thus suggesting the existence of a dynamic equilibrium (see the Supporting Information). The ab2
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Full Paper sorption spectrum of 10 is very typical of aromatic porphyrinoids[8] and exhibits a Soret-like band at l = 617 nm and Q-like bands at l = 783 and 887 nm (Figure 4). On the basis of this data, [28]hexaphyrin 10 has been assigned as a twisted Mçbius aromatic molecule, although we could not obtain a single crystal. Rhodium metalation of 10 Figure 2. Bis-rhodium complexes 11–13. was examined to rigidify the hexaphyrin framework. By stirring 10 in CH2Cl2 in the presence of [{RhCl(CO)2}2] (5 equiv) and NaOAc (10 equiv), the bis-rhodium [28]hexaphyrin complex 11 was yielded in 73 % (Figure 2). X-ray diffraction studies revealed that 11 adopts a bent-rectangular structure with a dihedral angle of 131.48, in which the {Rh(CO)2} groups are bound to the convex side and the 3,5-di-tert-butyl-4-hydroxyphenyl groups are tilted with respect to the hexaphyrin framework with dihedral angles of 54.7 and 56.18 (Figure 3). The 1H NMR spectrum of 11 displays four doublets due to the outer pyrrolic b-protons in the range of d = 3.23–4.55 ppm, a singlet due to the outer NH-protons at d = 2.92 ppm, and two doublets due to the inner b-protons at d = 18.65 and 18.68 ppm, thus indicating a strong paratropic ring current that arises from Hckel antiaromaticity. The chemical-shift difference, defined as the difference between the chemical shifts of the most shielded and deshielded protons, is Dd = 15.76 ppm and is slightly larger than that of 6 (i.e., Dd = 13.83 ppm). Oxidation of complex 11 with an excess amount of DDQ gave the quinonoidal rhodium hexaphyrin complex 12 quantitatively (Figure 2). X-ray diffraction studies revealed that the structure of 12 is bent with a dihedral angle of 103.28, in which the two OCH groups are located at the long sides and held in a nearly coplanar manner to the hexaphyrin frame with a dihedral angle of 3.058 and the C=O bond length is 1.254 (Figure 3; see the Supporting Information). In accord with the quinonoidal, cross-conjugated electronic network, the 1H NMR spectrum of 13 shows signals due to the pyrrolic b-protons in Figure 3. X-ray crystal structures of a) 11, b) 12, and c) 13. Left: top view; the range of d = 6.56–7.90 ppm, thus indicating its nonaromatright: side view. The thermal ellipsoids have been scaled to the 40 % probaic nature. bility level for 11 and 12 and 30 % probability level for 13. The solvent moleIn addition, we found that careful oxidation of 11 cules have been omitted for clarity. with one equivalent of DDQ furnished complex 13 almost quantitatively. Interestingly, 13 has both 3,5di-tert-butyl-4-hydroxyphenyl and OCH groups on the long side of the hexaphyrin framework, which is a rare case (Scheme 3). The structure of 13 was confirmed by X-ray diffraction studies to be roughly planar but bent with a dihedral angle of 133.18. The 3,5-di-tert-butyl-4-hydroxyphenyl group is tilted with respect to the hexaphyrin framework with a dihedral angle of 63.488, but the OCH group is nearly coplanar with a dihedral angle of 3.168. The C=O and C O bond lengths are 1.216 and 1.372 , respectively. The Scheme 3. Possible resonance of 13. Bold line represents a 26 p aromatic circuit of hexapresence of one OCH group causes disruption of the phyrin. Chem. Eur. J. 2014, 20, 1 – 9
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Full Paper To investigate the photophysical properties, the excitedstate dynamics of the rhodium complexes 11–13 in toluene were examined by transient absorption measurement. In the case of 11 and 13, within an initial time delay of 2 ps, the excited-state absorption (ESA) signals shift to the higher energy region, which generally represent energy-relaxation processes from the higher excited state to the lowest excited state. In other words, the ultrafast lifetime components (~ 1 ps) could have originated from the vibrational relaxation process in the excited states. The slow excited-state lifetime components of 400 and 600 ps for 11 and 13, respectively, could be assigned to the triplet-state lifetime because the fluorescence of 11 and 13 were not observed. The difference in the lifetimes between 11 and 13 is consistent with their aromatic features, that is, the antiaromaticity and aromaticity of 11 and 13, respectively.[10] Interestingly, 13 reveals more fast decay profiles than the previous rhodium complex of [26]hexaphyrin 5, which has a well-defined 26 p electronic circuit (see Figure S26 in the Supporting Information).[9] Furthermore, the triplet-state lifetime of 13 increases in DMSO (1300 ps) (Figure 5). Because the molecules that have well-defined p-conjugation show a long excited-state lifetime, these results also support a contribution of an aromatic zwitterionic resonance hybrid that encompasses a 26 p electronic circuit.
cyclic conjugated network (cross-conjugation). Despite this situation, the 1H NMR spectrum of 13 in CDCl3 indicates a substantial diatropic ring current by displaying four doublets due to the inner b-protons in a high-field range of d = 4.36– 4.80 ppm, eight doublets due to the outer b-protons in a lowfield range of d = 6.89–7.38 ppm, thus leading to determination of Dd = 3.02 ppm. This data may imply a contribution of an aromatic zwitterionic resonance hybrid that encompasses a 26 p electronic circuit (Scheme 3). In line with this hypothesis, the Dd value becomes larger upon increasing the polarity of the surrounding medium, that is, d = 3.30, 3.99, and 4.68 ppm in benzene, acetone, and dimethyl sulfoxide (DMSO), respectively. The absorption spectra of 11–13 are superimposed in Figure 4. The absorption spectrum of 11 does not have Q-like
Conclusion A hexaphyrin carrying two meso-OCH groups 9 has been prepared as the first example of a cross-conjugated hexaphyrin. Although quinonoidal hexaphyrin 9 is nonaromatic, its reduction product 10 displays Mçbius aromatic character. Bis-rhodium hexaphyrin complexes 11–13 were also synthesized and structurally well characterized. Complexes 11 and 12 were assigned as a Hckel antiaromatic molecule and a nonaromatic molecule, respectively. Unexpectedly, complex 13 exhibits a moderate diatropic ring current despite its cross-conjugated electronic network. The diatropic ring current of 13 increases upon increasing the polarity of the surrounding medium, thus suggesting a contribution from an aromatic zwitterionic resonance hybrid. Efforts are now devoted to the exploration of novel cross-conjugated porphyrinoids that possess larger pelectronic systems, which will be reported in due course.
Figure 4. UV/Vis/NIR absorption spectra of compounds 9–13 in CH2Cl2.
bands and that of 12 is more ill-defined, in line with their respective antiaromatic and nonaromatic natures. On the other hand, the absorption spectrum of 13 shows Soret-like bands at l = 519 and 628 nm and Q-like bands at l = 858 and 1033 nm with relatively strong intensities, thus probably reflecting partially forgiven HOMO–LUMO transitions that arise from an aromatic zwitterionic resonance contribution. Electrochemical studies were performed by using cyclic voltammetry (see the Supporting Information). The quinonoidal hexaphyrins 9 and 12 exhibited four and five reversible reduction waves, thus indicating multiple electron-accepting abilities. The electrochemical HOMO–LUMO gaps of 9 and 12 are 1.45 and 1.44 eV, respectively, thus reflecting their disrupted cyclic conjugation. Hexaphyrins 10 and 11 showed two reduction waves and four and three oxidation waves. The electrochemical HOMO–LUMO gaps of 10 and 11 are distinctly smaller (i.e., 1.10 and 0.86 eV, respectively), which are in line with the aromatic and antiaromatic natures. The nonsymmetric hexaphyrin bis-rhodium complex 13 displayed four reduction waves and three oxidation waves. More importantly, the HOMO–LUMO gap of 13 is relative small (0.99 eV), thus suggesting that the cyclic conjugative network is somewhat effective in 13. &
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Experimental Section Instrumentation and materials All the reagents were of the commercial reagent grade and were used without further purification, except where noted. Column chromatography on silica gel was performed on Wakogel C-200, C300, or C-400. TLC analysis was carried out on aluminum sheets coated with silica gel 60 F254 (Merck 5554). UV/Vis spectra were recorded on a Shimadzu UV-3600PC spectrometer. 1H and 19F NMR spectra were recorded on a JEOL ECA-600 spectrometer (operating at 600.17 and 564.73 MHz for 1H and 19F, respectively) with the residual solvent as the internal reference for 1H (d = 7.26 ppm in CDCl3) and hexafluorobenzene as the external reference for 19F (d = 162.9 ppm). High-resolution electrospray-ionization time-of-
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Full Paper atmosphere, and the reaction mixture was stirred for 1 h. DDQ (1.2 g, 3 equiv) was added to the mixture, which was stirred for 30 min at room temperature. The resulting solution was passed through a short column of basic alumina with CH2Cl2/AcOEt (10:1) as the eluent. The solvent was removed under reduced pressure and the product was separated by column chromatography on silica gel with CH2Cl2/hexane (1:1) as the eluent. A brown fraction was collected and evaporated to dryness. Recrystallization of the product from CH2Cl2/hexane afforded 9 (231 mg, 17 %). 1H NMR (CDCl3, 600.17 MHz): d = 14.12 (s, 2 H; inner NH), 8.23 (s, 4 H; vinylH), 7.02 (d, J = 4.6 Hz, 4 H; outer-b H), 6.82 (d, J = 4.6 Hz, 4 H; outerb H), 6.46 ppm (d, J = 1.8 Hz, 4 H; outer-b H); 19F NMR (CDCl3, 564.73 MHz): d = 134.8 (d, J = 23.0 Hz, 4 F; ortho-F), 137.5 (d, J = 28.0 Hz, 4 F; ortho-F), 150.1 (t, J = 23.0 Hz, 4 F; para-F), 160.1 ppm (m, 8 F; meta-F); HR-ESI-MS: m/z calcd for 12 C821H5414N616O219F20 : 1535.4062 [M + H] + ; found: 1535.4026; UV/Vis/ NIR absorption spectrum in CH2Cl2 : lmax (e) = 359 (87 300), 711 nm (11 700 m 1 cm 1); single crystals suitable for X-ray diffraction studies were obtained by recrystallization from chlorobenzene/nonane.
Crystal data for 9 C82H54F20N6O2, Mw = 1535.31, monoclinic, space group: P21/n (No. 14), a = 9.0726(2), b = 21.7060(4), c = 18.0976(4) , b = 103.7954(8)8, V = 3461.15(13) 3, Z = 2, T = 93(2) K, Dcalcd = 1.473 g cm 3, R1 = 0.0428 [I > 2s(I)], Rw = 0.1557 (all data), GOF = 1.045.
[28]Hexaphyrin 10 NaBH4 was added slowly to a solution of 9 in CH2Cl2/MeOH (10:1) at 0 8C. After consumption of the starting material was confirmed by TLC analysis, the reaction mixture was quenched with H2O and saturated NH4Cl solution. The product was extracted with CH2Cl2. The organic layer was collected, dried over anhydrous Na2SO4, and concentrated to a clear blue solid. Recrystallization from CH2Cl2/ hexane gave 10 in almost quantitative yield. 1H NMR (CDCl3, 600.17 MHz, room temperature): d = 8.20 (br), 7.78 (d, J = 4.1 Hz; outer-b H), 7.59 (br), 7.17 (br), 5.42 (s), 1.32 ppm (s); 19F NMR (CDCl3, 564.73 MHz, room temperature): d = 137.2 (br, 4 F; orthoF), 137.8 (s, 4 F; ortho-F), 152.6 (t, J = 17.3 Hz, 4 F; para-F), 153.9 (br, 2 F; para-F), 160.9 (br, 4 F; meta-F), 161.8 ppm (t, J = 17.3 Hz, 4 F; meta-F); 1H NMR (CDCl3, 600.17 MHz, 60 8C): d = 10.60 (br), 8.01 (br), 7.88 (br), 7.83 (br), 7.79 (s), 7.52 (br), 7.45 (br), 7.43 (s), 5.63 (s), 1.40 (s), 0.60 (br), 1.50 ppm (br); 19F NMR (CDCl3, 564.73 MHz, 60 8C): d = 136.8 (br; ortho-F), 137.3 (s; ortho-F), 137.5 (s; ortho-F), 151.5 (br; para-F), 152.8 (s; para-F), 153.1 (br; para-F), 159.5 (br; meta-F), 160.9 ppm (s; meta-F); 1 H NMR ([D8]THF, 600.17 MHz, room temperature): d = 11.80 (br), 10.80 (s), 10.52 (s), 10.48 (s), 10.30 (s), 10.12 (s), 9.52 (s), 9.45 (br), 7.92 (s), 7.75 (d, J = 4.6 Hz; outer-b H), 7.64 (br), 7.47 (br), 7,32 (s), 7.01 (d, J = 4.1 Hz; outer-b H), 6.92 (s), 6.82 (s), 6.73 (d, J = 17.9 Hz), 6.63 (s), 6.60 (d, J = 4.6 Hz; outer-b H), 6.52 (s), 6.37 (s), 6.28 (s), 5.79 (s), 5.49 (s), 1.40 ppm (s); 19F NMR ([D8]THF, 564.73 MHz, room temperature): d = 139.22 (s; ortho-F), 140.1 (s; ortho-F), 140.7 (br; ortho-F), 141.2 (br; ortho-F), 142.5 (br; ortho-F), 157.2 (m; para-F), 157.6 (t, J = 21.7 Hz; para-F), 157.8 (t, J = 21.7 Hz; paraF), 158.6 (t, J = 21.7 Hz; para-F), 163.6 (br; meta-F), 164.0 (m; meta-F), 164.5 (t, J = 17.3 Hz; meta-F), 164.6 ppm (t, J = 17.3 Hz; meta-F); 1H NMR ([D8]THF, 600.17 MHz, 20 8C): d = 12.03 (br), 11.01 (s), 10.70 (s), 10.46 (s), 10.40 (s), 10.19 (s), 9.93 (s), 9.75 (s), 7.92 (s), 8.24 (s), 7.98–8.11 (br), 7.89 (s), 7.81 (d, J = 3.9 Hz; outer-b H), 7.73 (s), 7.71 (s), 7.50–7.66 (br), 7.43 (s), 7.24–7.36 (br), 7.04 (d, J = 4.1 Hz), 7.00 (s), 6.90–6.96 (br), 6.90 (s), 6.84 (s), 6.75 (d, J = 3.7 Hz), 6.71 (s), 6.66 (t, J = 5.0 Hz; outer-b H), 6.47 (s), 6.43 (s), 6.35 (d, J =
Figure 5. Femtosecond (fs) transient absorption spectra (top) and decay profiles (bottom) of 13 in toluene (a) and DMSO (b).
flight mass spectroscopy (HR-ESI-TOF-MS) was recorded on a BRUKER microTOF model with positive and negative modes for solutions of samples in acetonitrile. Redox potentials were measured by cyclic voltammetry on an ALS electrochemical analyzer model 660. Crystallographic data were collected on a Rigaku RAXIS-RAPID and XtaLAB P200 apparatus at 180 8C with graphitemonochromated CuKa radiation (l = 1.54187 ). The structures were solved by direct method SIR- 97 and refined by means of the SHELXL-97 program.
Quinoidal hexaphyrin 9 MSA (2.5 m diluted with CH2Cl2, 45 mL, 12.5 mol %) was added to a solution of 5,10-bis(pentafluorophenyl)tripyrrane (7; 1.0 g, 1.8 mmol) and 3,5-di-tert-butyl-4-hydroxybenzaldehyde (8; 420 mg, 1.8 mmol, 1 equiv) in CH2Cl2 (180 mL) at 0 8C under nitrogen Chem. Eur. J. 2014, 20, 1 – 9
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Full Paper 18.400(10) , a = 105.315(15), b = 110.704(14), g = 91.784(4)8, V = 4637(3) 3, Z = 2, T = 93(2) K, Dcalcd = 1.494 g cm 3, R1 = 0.0887 [I > 2s(I)], Rw = 0.2742 (all data), GOF = 1.053.
5.5 Hz; outer-b H), 6.32 (d, J = 5.0 Hz; outer-b H), 6.17 (d, J = 3.7 Hz; outer-b H), 5.71 (s), 5.26 (s), 1.39 (s), 1.31 (s), 1.25 (s), 1.23 (s), 1.17 ppm (s); 19F NMR ([D8]THF, 564.73 MHz, 20 8C): d = 138.9 (br; ortho-F), 139.4 (s; ortho-F), 139.8 (br; ortho-F), 140.1 (br; ortho-F), 140.3 (d, J = 26.0 Hz; ortho-F), 140.6 (d, J = 26.0 Hz; ortho-F), 141.0 (br; ortho-F), 141.3 (d, J = 21.7 Hz; ortho-F), 141.6 (br; ortho-F), 141.8 (br; ortho-F), 142.5 (d, J = 17.3 Hz; ortho-F), 157.0 (br; para-F), 157.4 (t, J = 16.8 Hz; para-F), 157.6 (t, J = 16.8 Hz; para-F), 157.8 (br; para-F), 157.9 (m; para-F), 158.0 (t, J = 21.7 Hz; para-F), 157.6 (t, J = 16.8 Hz; para-F), 159.1 (t, J = 21.7 Hz; para-F), 163.7 (t, J = 21.6 Hz; meta-F), 163.9 (t, J = 17.3 Hz; meta-F), 164.1 (t, J = 21.6 Hz; meta-F), 164.3 (t, J = 17.3 Hz; meta-F), 164.5(s; meta-F), 164.7 ppm (s; meta-F); 1H NMR ([D8]THF, 600.17 MHz, 100 8C): d = 12.72 (s), 12.45 (s), 11.63 (s), 11.05 (s), 10.67 (s), 10.11(s), 8.88 (s), 8.50 (s), 8.46 (s), 8.30 (s), 8.25 (s), 8.07 (s), 8,03 (s), 7.93 (s), 7.87 (s), 7.79 (s), 7.76 (s), 7.63 (s), 7.60 (s), 7.54 (s), 7.51 (s), 7.45 (s), 7,40 (s), 7.08 (s), 7.07 (s), 7.02 (s), 7.00 (d, J = 5.0 Hz; outer-b H), 6.94 (s), 6.88 (d, J = 5.0 Hz; outer-b H), 6.83 (s), 6.79 (s), 6.60 (s), 6.51 (d, J = 5.0 Hz; outer-b H), 6.46 (d, J = 4.6 Hz; outer-b H), 6.42 (s), 6.26 (s), 6.15 (s), 5.55 (s), 4.97 (s), 4.88 (s), 4.79 (s), 1.00–1.50 (br), 0.77 ppm (s); 19F NMR ([D8]THF, 564.73 MHz, 100 8C): d = 138.4 (s; ortho-F), 138.6 (s; ortho-F), 138.9 (s; ortho-F), 139.3 (s; ortho-F), 139.5 (s; ortho-F), 139.9 (s; ortho-F), 140.3 (s; ortho-F), 140.6 (s; ortho-F), 140.9 (s; ortho-F), 141.0 - 141.5 (br; ortho-F), 142.1 (s; ortho-F), 142.7 (s; ortho-F), 157.6 (s; para-F), 158.0 (s; para-F), 158.0 - 159.0 (br; para-F), 159.7 (s; para-F), 163.5 (s; meta-F), 163.8 (s; metaF), 164.2 (s; meta-F), 164.6 (s; meta-F), 165.1 ppm (s; meta-F); HR-ESI-MS: m/z calcd for 12C821H5814N616O219F20 : 1539.4375 [M + H] + ; found: 1539.4412; UV/Vis/NIR absorption spectrum in CH2Cl2 : lmax (e) = 309 (24 600), 408 (37 800), 617 (146 300), 783 (10 600), 887 nm (7000 m 1 cm 1).
Rhodium complex of quinoidal hexaphyrin 12 DDQ (excess) was added to a solution of hexaphyrin 11 in CH2Cl2 at room temperature in air, and the reaction mixture was stirred for 5 min. The resulting solution was passed through a short column of basic alumina with CH2Cl2 as the eluent. The solvent was removed under reduced pressure. Recrystallization from CH2Cl2/hexane gave 12 as a dark-green solid in almost quantitative yield. 1H NMR (CDCl3, 600.17 MHz): d = 9.19 (d, J = 2.8 Hz, 2 H; vinyl H), 8.05 (d, J = 4.6 Hz, 2 H; inner-b H), 7.90 (d, J = 4.6 Hz, 2 H; innerb H), 6.87 (d, J = 2.8 Hz, 2 H; vinyl H), 6.77 (m, 4 H; outer-b H), 6.71 (d, J = 4.6 Hz, 2 H; outer-b H), 6.56 (d, J = 4.6 Hz, 2 H; outer-b H), 1.19 (s, 18 H; tBu), 0.98 ppm (s, 18 H; tBu); 19F NMR (CDCl3, 564.73 MHz): d = 134.1 (d, J = 21.6 Hz, 2 F; ortho-F), 136.1 (d, J = 21.7 Hz, 2 F; ortho-F), 137.6 (d, J = 21.7 Hz, 2 F; ortho-F), 138.0 (d, J = 21.7 Hz, 2 F; ortho-F), 150.4 (t, J = 21.6 Hz, 2 F; para-F), 150.7 (t, J = 21.7 Hz, 2 F; para-F), 159.5 (dt, J = 8.6, 21.6 Hz, 2 F; meta-F), 159.8 (dt, J = 8.5, 21.7 Hz, 2 F; meta-F), 161.3 (dt, J = 8.6, 21.6 Hz, 2 F; meta-F), 162.0 ppm (dt, J = 8.6, 21.6 Hz, 2 F; meta-F); HR-ESI-MS: m/z calcd for 12C861H5214N616O619F20102Rh2 : 1851.1812 [M + H] + ; found: 1851.1792; UV/Vis/NIR absorption spectrum in CH2Cl2 : lmax (e) = 344 (40 000), 422 (48 500), 513 (36 600), 610 (38 900), 735 nm (42 000 m 1 cm 1); single crystals suitable for X-ray diffraction studies were obtained by recrystallization from CHCl3/MeOH.
Crystal data for 12 C86H52F20N6O6Rh2, Mw = 925.58, orthorhombic, space group: F d d 2 (No. 43), a = 42.24(5), b = 55.30(6), c = 6.440(7) , V = 15 043(29) 3, Z = 16, T = 93(2) K, Dcalcd = 1.635 g cm 3, R1 = 0.1232 [I > 2s(I)], Rw = 0.3558 (all data), GOF = 1.057.
Rhodium complex of hexaphyrin 11 NaOAc (20 mg, 10 equiv) and [{RhCl(CO)2}2] (60 mg, 6 equiv) were added to a solution of hexaphyrin 10 (40 mg, 26 mmol) in CH2Cl2 (20 mL) at room temperature in a nitrogen atmosphere, and the reaction mixture was stirred for 1 h. The solvent was removed under reduced pressure, and the crude mixture was separated by column chromatography on silica gel with CH2Cl2/hexane (1:1) as the eluent. The first violet fraction was collected and evaporated to dryness. Recrystallization from CH2Cl2/hexane afforded 11 (35 mg, 73 %) as a dark-reddish solid. 1H NMR (CDCl3, 600.17 MHz): d = 18.68 (d, J = 5.0 Hz, 2 H; inner-b H), 18.65 (d, J = 5.5 Hz, 4 H; innerb H), 6.03 (s, 4 H; Ar-H), 5.06 (s, 2 H; OH), 4.55 (d, J = 4.6 Hz, 2 H; outer-b H), 4.39 (d, J = 4.6 Hz, 2 H; outer-b H), 3.32 (d, J = 4.0 Hz, 2 H; outer-b H), 3.23 (d, J = 4.6 Hz, 2 H; outer-b H), 2.92 (s, 2 H; outer NH), 1.13 ppm (s, 36 H; tBu); 19F NMR (CDCl3, 564.73 MHz): d = 132.2 (s, 2 F; ortho-F), 137.9 (s, 2 F; ortho-F), 139.3 (d, J = 21.7 Hz, 2 F; ortho-F), 140.1 (d, J = 17.3 Hz, 2 F; ortho-F), 153.4 (t, J = 17.3 Hz, 2 F; para-F), 153.7 (t, J = 21.7 Hz, 2 F; para-F), 158.3 (s, 2 F; meta-F), 158.7 (s, 2 F; meta-F), 160.2 (dt, J = 8.7, 21.7 Hz, 2 F; meta-F), 160.2 ppm (dt, J = 8.7, 21.7 Hz, 2 F; meta-F); HR-ESIMS: m/z calcd for 12C861H5614N616O619F20102Rh2 : 1854.2047 [M] + ; found: 1854.2042; UV/Vis/NIR absorption spectrum in CH2Cl2 : lmax (e) = 369 (31100), 539 (108 600), 584 (98 400), 692 nm (23 800 m 1 cm 1); single crystals suitable for X-ray diffraction studies were obtained by recrystallization from CHCl3/heptane.
Rhodium complex of quinoidal hexaphyrin 13 DDQ (1 equiv) was added to a solution of hexaphyrin 11 in CH2Cl2 at room temperature in air, and the reaction mixture was stirred for 5 min. The resulting solution was passed through a short column of basic alumina with CH2Cl2/AcOEt (10:1) as the eluent. The solvent was removed under reduced pressure. The product can be further purified by chromatography on silica gel 60N (spherical, neutral) if needed. Recrystallization from CHCl3/octane afforded 13 as a blue solid in almost quantitative yield.1H NMR ([D6]benzene, 600.17 MHz): d = 10.01 (d, J = 2.3 Hz, 1 H; vinyl-H), 8.81 (s, 1 H; NH), 7.74 (s, 2 H; Ar-H), 7.40 (d, J = 4.6 Hz, 1 H; outerb H), 7.18 (d, J = 4.6 Hz, 4 H; outer-b H), 7.14 (d, J = 4.6 Hz, 1 H; outer-b H), 7.08 (m, 2 H; outer-b H), 7.05 (d, J = 4.1 Hz, 1 H; outerb H), 6.99 (d, J = 2.3 Hz, 1 H; vinyl-H), 6.87 (d, J = 4.1 Hz, 1 H; outerb H), 6.76 (d, J = 4.1 Hz, 1 H; outer-b H), 5.31 (s, 1 H; OH), 4.65 (dd, J = 1.8, 5.0 Hz, 1 H; inner-b H), 4.63 (d, J = 4.6 Hz, 1 H; inner-b H), 4.46 (d, J = 4.6 Hz, 1 H; inner-b H), 4.10 (dd, J = 1.8, 5.0 Hz, 1 H; inner-b H), 1.47 (s, 9 H; tBu), 1.36–1.41 (br, 18 H; tBu), 1.38 ppm (s, 9 H; tBu); 19F NMR ([D6]benzene, 564.73 MHz): d = 134.4 (d, J = 21.7 Hz, 1 F; ortho-F), 135.6 (d, J = 21.6 Hz, 1 F; ortho-F), 137.1 (d, J = 21.6 Hz, 1 F; ortho-F), 138.1 (d, J = 21.7 Hz, 1 F; ortho-F), 138.5 (d, J = 21.6 Hz, 2 F; ortho-F), 139.3 (d, J = 26.0 Hz, 1 F; ortho-F), 139.5 (d, J = 21.7 Hz, 1 F; ortho-F), 150.3 (t, J = 21.7 Hz, 1 F; para-F), 150.9 (t, J = 21.7 Hz, 1 F; para-F), 151.4 (m, 2 F; para-F), 156.6 (t, J = 17.3 Hz, 1 F; meta-F), 158.6 (t, J = 21.6 Hz, 1 F; meta-F), 160.0 (dt, J = 8.6, 21.7 Hz, 1 F; meta-F), 160.1 (dt,
Crystal data for 11 (C86H56F20N6O6Rh2)2·(C24H56)0.35·(CHCl3)2.6·(O)2, Mw = 2086.69, triclinic, space group: P-1 (No. 2), a = 15.615(6), b = 18.062 (6), c =
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Full Paper 1033 nm (10 900 m 1 cm 1); single crystals suitable for X-ray diffraction studies were obtained by recrystallization from CHCl3/octane.
J = 8.6, 21.7 Hz, 1 F; meta-F), 160.5 (dt, J = 8.6, 21.7 Hz, 1 F; metaF), 160.7 (dt, J = 8.6, 21.7 Hz, 1 F; meta-F), 161.6 (t, J = 17.3 Hz, 1 F; meta-F), 162.6 ppm (t, J = 21.7 Hz, 1 F; meta-F); 1H NMR (CDCl3, 600.17 MHz): d = 9.52 (d, J = 2.3 Hz, 1 H; vinyl-H), 8.78 (s, 1 H; NH), 7.45 (s, 2 H; Ar-H), 7.38 (d, J = 4.6 Hz, 1 H; outer-b H), 7.35 (d, J = 4.6 Hz, 4 H; outer-b H), 7.32 (d, J = 4.1 Hz, 1 H; outer-b H), 7.28 (d, J = 4.6 Hz, 1 H; outer-b H), 7.21 (d, J = 4.6 Hz, 1 H; outerb H), 7.19 (d, J = 4.6 Hz, 1 H; outer-b H), 6.97 (d, J = 4.6 Hz, 1 H; outer-b H), 6.89 (d, J = 4.6 Hz, 1 H; outer-b H), 6.71 (d, J = 2.7 Hz, 1 H; vinyl-H), 5.60 (s, 1 H; OH), 4.80 (dd, J = 1.9, 5.0 Hz, 1 H; innerb H), 4.64 (d, J = 4.1 Hz, 1 H; inner-b H), 4.49 (dd, J = 1.8, 5.0 Hz, 1 H; inner-b H), 4.36 (d, J = 4.6 Hz, 1 H; inner-b H), 1.51 (s, 18 H; tBu), 1.22 (s, 9 H; tBu), 1.04 ppm (s, 9 H; tBu); 19F NMR (CDCl3, 564.73 MHz): d = 134.2 (d, J = 21.7 Hz, 1 F; ortho-F), 135.4 (d, J = 21.6 Hz, 1 F; ortho-F), 136.4 (d, J = 21.6 Hz, 1 F; ortho-F), 136.5 (d, J = 26.0 Hz, 1 F; ortho-F), 137.1 (d, J = 21.6 Hz, 1 F; ortho-F), 138.1 (d, J = 21.7 Hz, 1 F; ortho-F), 138.2 (d, J = 21.7 Hz, 1 F; ortho-F), 138.6 (d, J = 21.6 Hz, 1 F; ortho-F), 150.4 (t, J = 21.7 Hz, 1 F; para-F), 151.4 (t, J = 21.7 Hz, 1 F; para-F), 151.6 (t, J = 21.7 Hz, 1 F; para-F), 152.1 (t, J = 21.7 Hz, 1 F; para-F), 157.3 (t, J = 17.3 Hz, 1 F; meta-F), 158.2 (t, J = 17.3 Hz, 1 F; meta-F), 160.3 (t, J = 17.3 Hz, 1 F; meta-F), 160.5 (t, J = 17.3 Hz, 1 F; meta-F), 160.6 (t, J = 17.3 Hz, 1 F; meta-F), 160.8 (t, J = 17.3 Hz, 1 F; metaF), 161.8 (t, J = 17.3 Hz, 1 F; meta-F), 162.6 ppm (t, J = 17.3 Hz, 1 F; meta-F); 1H NMR ([D6]acetone, 600.17 MHz): d = 12.13 (s, 1 H; NH), 9.71 (d, J = 2.3 Hz, 1 H; vinyl-H), 7.87 (d, J = 4.6 Hz, 1 H; outerb H), 7.82 (d, J = 4.1 Hz, 1 H; outer-b H), 7.80 (d, J = 5.0 Hz, 1 H; outer-b H), 7.68 (d, J = 5.0 Hz, 1 H; outer-b H), 7.67 (d, J = 5.0 Hz, 1 H; outer-b H), 7.60 (d, J = 4.1 Hz, 1 H; outer-b H), 7.49 (d, J = 4.6 Hz, 1 H; outer-b H), 7.90–7.40 (br, 2 H; Ar-H), 7.18 (d, J = 5.0 Hz, 1 H; outer-b H), 6.87 (d, J = 2.3 Hz, 1 H; vinyl-H), 6.59 (s, 1 H; OH), 4.37 (d, J = 5.0 Hz, 1 H; inner-b H), 4.18 (d, J = 4.6 Hz, 1 H; innerb H), 3.98 (d, J = 5.0 Hz, 1 H; inner-b H), 3.88 (d, J = 4.6 Hz, 1 H; inner-b H), 1.48–1.60 (br, 18 H; tBu), 1.23 (s, 9 H; tBu), 1.05 ppm (s, 9 H; tBu); 19F NMR ([D6]acetone, 564.73 MHz): d = 137.0 (d, J = 21.7 Hz, 1 F; ortho-F), 139.1 (d, J = 21.7 Hz, 1 F; ortho-F), 140.2 (m, 2 F; ortho-F), 141.2 (d, J = 21.7 Hz, 1 F; ortho-F), 141.4 (d, J = 17.3 Hz, 1 F; ortho-F), 141.8 (d, J = 21.7 Hz, 1 F; ortho-F), 155.3 (t, J = 21.7 Hz, 1 F; para-F), 155.6 (t, J = 21.6 Hz, 1 F; para-F), 156.2 (t, J = 17.3 Hz, 1 F; para-F), 163.6 (m, 2 F; meta-F), 163.7 (t, J = 21.7 Hz, 1 F; meta-F), 163.9 (dt, J = 8.6, 21.6 Hz, 1 F; meta-F), 164.5 (t, J = 21.7 Hz, 1 F; meta-F), 164.7 (t, J = 21.7 Hz, 1 F; metaF), 165.2 ppm (dt, J = 8.6, 21.6 Hz, 1 F; meta-F); 1H NMR ([D6]DMSO, 600.17 MHz): d = 12.95 (s, 1 H; NH), 9.62 (s, 1 H; vinyl-H), 8.02 (d, J = 4.5 Hz, 1 H; outer-b H), 7.88 (d, J = 3.7 Hz, 1 H; outerb H), 7.85 (m, 1 H; outer-b H), 7.80 (d, J = 3.7 Hz, 1 H; outer-b H), 7.78 (d, J = 3.7 Hz, 1 H; outer-b H), 7.70 (d, J = 3.4 Hz, 1 H; outerb H), 7.61 (d, J = 3.7 Hz, 1 H; outer-b H), 7.58 (s, 2 H; Ar-H), 7.18 (d, J = 4.8 Hz, 1 H; outer-b H), 6.76 (s, 1 H; vinyl-H), 5.77 (s, 1 H; OH), 3.82 (s, 1 H; inner-b H), 3.73 (s; inner-b H), 3.41 (s, 1 H; inner-b H), 3.34 (s, 1 H; inner-b H), 1.23 (s, 9 H; tBu), 1.18 (s, 18 H; tBu), 0.97 ppm (s, 9 H; tBu); 19F NMR ([D6]DMSO, 564.73 MHz): d = 136.2 (d, J = 21.6 Hz, 1 F; ortho-F), 138.3 (d, J = 21.6 Hz, 1 F; ortho-F), 139.6 (d, J = 21.8 Hz, 1 F; ortho-F), 139.7 (d, J = 26.8 Hz, 1 F; ortho-F), 140.2 (d, J = 25.8 Hz, 1 F; ortho-F), 140.4 (d, J = 21.8 Hz, 1 F; ortho-F), 140.7 (d, J = 21.8 Hz, 1 F; ortho-F), 140.9 (d, J = 20.8 Hz, 1 F; ortho-F), 154.0 - 153.7 (m, 3 F; para-F), 155.8 (t, J = 21.5 Hz, 1 F; para-F), 159.4 (t, J = 21.6 Hz, 1 F; meta-F), 161.7 (m, 2 F; meta-F), 162.0 (t, J = 21.0 Hz, 1 F; meta-F), 162.2 (t, J = 21.0 Hz, 1 F; meta-F), 162.9 (t, J = 17.7 Hz, 1 F; meta-F), 163.8 (t, J = 21.0 Hz, 1 F; meta-F), 163.9 ppm (t, J = 22.1 Hz, 1 F; meta-F); HR-ESI-MS: m/z calcd for 12C861H5414N616O619F20102Rh2 : 1853.1968 [M + H] + ; found: 1853.1951; UV/Vis/NIR absorption spectrum in CH2Cl2 : lmax (e) = 350 (32 900), 519 (61100), 628 (79 400), 858 (13 800), Chem. Eur. J. 2014, 20, 1 – 9
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Crystal data for 13 C86H54F20N6O6Rh2·(C8H18)2·(CHCl3)0.36·(O)0.64, Mw = 2135.09, triclinic, space group: P-1 (No. 2), a = 15.703(12), b = 17.917(12), c = 20.081(12) , a = 107.82, b = 101.202(12), g = 106.29(2)8, V = 4914(6) 3, Z = 2, T = 93(2) K, Dcalcd = 1.443 g cm 3, R1 = 0.0918 [I > 2s(I)], Rw = 0.2877 (all data), GOF = 1.026. CCDC-988116 (9), 988117 (11), 988118 (12) and 988119 (13) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgements The work at Kyoto was supported by Grant-in-Aid (No. 25220802 (S)) for Scientific Research from MEXT of Japan. The work at Yonsei was supported by the Global Frontier R&D Program of the Center for Multiscale Energy System (2012–8– 2081) of National Research Foundation (NRF) grant funded by MEST of Korea, and AFSOR/AOARD grant (No. FA2386–09– 4092). This collaborative work is supported by the Global Research Laboratory Program (2013–8–1472) funded by the Ministry of Education, Science and Technology (MEST). Keywords: aromaticity · cross conjugation porphyrins · hexaphyrin · porphyrinoids
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Z. S. Yoon, J.-Y. Shin, J. M. Lim, Y. Matsuzaki, O. Matsushita, A. Muranaka, N. Kobayashi, D. Kim, A. Osuka, J. Am. Chem. Soc. 2008, 130, 13568; d) Z. S. Yoon, A. Osuka, D. Kim, Nat. Chem. 2009, 1, 113; e) M. Ste˛pien´, B. Szyszko, L. Latos-Graz˙yn´ski, J. Am. Chem. Soc. 2010, 132, 3140; f) M. Ste˛pien´, N. Sprutta, L. Latos-Graz˙yn´ski, Angew. Chem. 2011, 123, 4376; Angew. Chem. Int. Ed. 2011, 50, 4288. [9] a) H. Rath, N. Aratani, J. M. Lim, J. S. Lee, D. Kim, H. Shinokubo, A. Osuka, Chem. Commun. 2009, 3762; b) T. Tanaka, N. Aratani, A. Osuka, Chem. Asian J. 2012, 7, 889. [10] a) S. Cho, Z. S. Yoon, K. S. Kim, M.-C. Yoon, D.-G. Cho, J. L. Sessler, D. Kim, J. Phys. Chem. Lett. 2010, 1, 895; b) M.-C. Yoon, S. Cho, M. Szuzuki, A. Osuka, D. Kim, J. Am. Chem. Soc. 2009, 131, 7360.
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FULL PAPER & Porphyrinoids
A good circuit: A cross-conjugated hexaphyrin that carries two meso-oxacyclohexadienyl (OCH) groups was prepared and reduced to a Mçbius aromatic [28]hexaphyrin. Bis-rhodium complexes of this system can take three different electronic states, one of which bears both a phenol and an OCH group, thus displaying a moderate diatropic ring current and probably reflecting a significant contribution of an aromatic zwitterionic resonance hybrid (see figure).
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K. Naoda, Y. M. Sung, J. M. Lim, D. Kim,* A. Osuka* && – && Cross-Conjugated Hexaphyrins and Their Bis-Rhodium Complexes
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Cross-Conjugated Hexaphyrins and Their Bis-Rhodium Complexes Koji Naoda,[a] Young Mo Sung,[b] Jong Min Lim,[b] Dongho Kim,*[b] and Atsuhiro Osuka*[a]
ing upon the reaction conditions. Both 12 and 13 are planar owing to bis-rhodium metalation. Although complex 12 bears two meso-OCH groups at the long sides and is quinonoidal and nonaromatic in nature, complex 13 bears 3,5-ditert-butyl-4-hydroxyphenyl and OCH groups and exhibits a moderate diatropic ring current despite its cross-conjugated electronic circuit. The diatropic ring current increases upon increasing the solvent polarity, most likely due to an increased contribution of an aromatic zwitterionic resonance hybrid.
Abstract: A cross-conjugated hexaphyrin that carries two meso-oxacyclohexadienylidenyl (OCH) groups 9 was synthesized from the condensation of 5,10-bis(pentafluorophenyl)tripyrrane with 3,5-di-tert-butyl-4-hydroxybenzaldehyde. The reduction of 9 with NaBH4 afforded the Mçbius aromatic [28]hexaphyrin 10. Bis-rhodium complex 11, prepared from the reaction of 10 with [{RhCl(CO)2}2], displays strong Hckel antiaromatic character because of the 28 p electrons that occupy the conjugated circuit on the enforced planar structure. The oxidation of 11 with 2,3-dichloro-5,6-dicyano-1,4benzoquinone (DDQ) yielded complexes 12 and 13 depend-
Introduction Meso-alkenylidenyl-substituted porphyrins have attracted considerable attention in view of their unique electronic and structural properties that arise from their quinonoidal cross-conjugated networks.[1] Representative examples include oxacyclohexadienylidene(OCH)-substituted porphyrins, dicyanomethylidenyl-substituted porphyrins,[1a–c] dithiomethylidenyl substituted porphyrins,[1d,e] and core-modified diethoxycarbonylmethylidenyl-substituted porphyrins.[2a,c] Tetrakis-OCH-substituted porphyrin 1 demonstrates solvatochromism,[3a] anion binding,[3a–c] O2 reduction capability,[3d,e] and reversible redox interconversions.[3b,f] Further recent reports on the application of 1 and related porphyrins include sensors for trace water[4a] or acid–base equilibria[4b] and hosts for chiral guest molecules.[4c] These latest reports highlight the great promise that such porphyrinoids show for acting as nanoarchitectonic sensors with a diverse range of physical-detection modes.[5] We also reported a tris(3,5-di-tert-butyl-4-hydroxyphenyl)-substituted subporphyrin and its oxidized subporphyrin 2 as the first examples of meso-OCH-substituted subporphyrins (Scheme 1),[6] which showed interesting deprotonation behavScheme 1. 3,5-Di-tert-butyl-4-hydroxyphenyl-substituted quinonoidal porphyrin 1 and subporphyrin 2. Redox interconversions of 1) [26]- and [28]hexaphyrins 3 and 4 and 2) bis-rhodium complexes 5 and 6.
[a] K. Naoda, Prof. A. Osuka Department of Chemistry Graduate School of Science, Kyoto University Sakyo-ku, Kyoto 606-8502 (Japan) E-mail: [email protected]
ior. Interestingly, upon deprotonation, 2 changed from dark green to vivid blue, with the deprotonated form exhibiting a planar extended structure with almost C3 symmetry. In contrast, meso-alkenylidene-substituted expanded porphyrins have been scarcely studied, except for core-modified analogues.[2b–e] In recent years, expanded porphyrins have emerged as a new class of porphyrinoid that possess larger conjugated
[b] Y. M. Sung, J. M. Lim, Prof. Dr. D. Kim Spectroscopy Laboratory for Functional p-Electronic Systems and Department of Chemistry Yonsei University, Seoul 120-749 (Korea) E-mail: [email protected] Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201402328. Chem. Eur. J. 2014, 20, 1 – 9
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Full Paper networks.[7] Although expanded porphyrins allow the realization of various p-conjugated electronic systems, such as Hckel aromatic and antiaromatic, Mçbius aromatic and antiaromatic, and stable-radical molecules,[8] the potential of expanded porphyrins has not been fully exploited and the search for expanded porphyrins with novel electronic states continues. Different from porphyrins, expanded porphyrins are structurally and electronically flexible. As a prime example, [26]hexaphyrin Scheme 2. Synthesis of hexaphyrins 9 and 10. MSA = methanesulfonic acid. 3, a typical Hckel aromatic molecule with a rectangular shape, is reduced upon treatment with NaBH4 to afford the twisted Mçbius aromatic [28]hexaphyrin 4 accompanied by large structural changes.[8c] In contrast, the corresponding rhodium complexes 5 and 6 are structurally rigid and display Hckel aromatic and antiaromatic characteristics, respectively, thus simply reflecting the numbers of p electrons that occupy their planar conformations (Scheme 1).[9] Herein, we report the synthesis of OCH-substituted hexaphyrins and demonstrate how the incorporation of meso-alkenylidene motifs into the hexaphyrin framework alters and influences the electronic properties. Cross-conjugated quinonoidal hexaphyrin 9 that bears two OCH groups has been shown to be reduced to the Mçbius aromatic [28]hexaphyrin 10 with two 3,5-di-tert-butyl-4-hydroxyphenyl groups. In addition, bis-rhodium metalation was accomplished for this quinonoidal hexaphyrin system, thus allowing the formation of three planar bis-rhodium complexes 11– 13, which bear zero, two, and one OCH groups, respectively. Bis-rhodium complex 13 exhibits a moderate diatropic ring current despite its cross-conjugated electronic circuit. Figure 1. X-ray crystal structure of 9. Top: perspective view. Bottom: side view. The thermal ellipsoids have been scaled to the 50 % probability level. Hydrogen atoms, except for NH, have been omitted for clarity. Dashed lines represent hydrogen bonds.
Results and Discussion With the goal of synthesizing bis(3,5-di-tert-butyl-4-hydroxyphenyl)-substituted [26]hexaphyrin in mind, condensation of tripyrromethane 7 with 3,5-di-tert-butyl-4-hydroxybenzaldehyde (8) was attempted in the presence of a catalytic amount of methanesulfonic acid at 0 8C followed by oxidation with 2,3dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in situ. The crude material was subjected to chromatography on silica gel to yield the quinonoidal hexaphyrin 9 in 17 % yield (Scheme 2). High-resolution electrospray-ionization time-of-flight (HR-ESITOF) mass-spectrometric measurement showed the parent-ion peak of 9 at m/z 1535.4026 (m/z calcd for [M + H] + : 1535.4062). The 1H NMR spectrum of 9 displays three doublet signals due to the outer b-protons in a range of d = 6.46–7.02 ppm and a singlet signal at d = 14.1 ppm due to the inner-NH proton, thus suggesting a nonaromatic nature. The electronic absorption spectrum of 9 in CH2Cl2 shows a band at l = 359 nm, but neither a Soret-like nor Q-like band is observed (Figure 4). The &
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structure of 9 has been revealed by X-ray diffraction studies to be a dumbbell shape stabilized by intramolecular hydrogen bonds (Figure 1). The average C=O bond length of the 3,5-ditert-butyl-4-hydroxyphenyl group is 1.234 , which is in line with a quinonoidal-type structure. Reduction of 9 with NaBH4 proceeded quantitatively to afford [28]hexaphyrin 10 (Scheme 2). The 1H and 19F NMR spectra of 10 are too broad for structural assignment at room temperature but become relatively sharp at low temperature so that signals owing to the pyrrolic b-protons and the inner bprotons are displayed in the approximate ranges of d = 6.0–9.0 and d = 1.0–0.0 ppm, respectively, thus implying an aromatic character. The 19F NMR spectrum of 10 indicates the presence of several conformers, thus suggesting the existence of a dynamic equilibrium (see the Supporting Information). The ab2
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Full Paper sorption spectrum of 10 is very typical of aromatic porphyrinoids[8] and exhibits a Soret-like band at l = 617 nm and Q-like bands at l = 783 and 887 nm (Figure 4). On the basis of this data, [28]hexaphyrin 10 has been assigned as a twisted Mçbius aromatic molecule, although we could not obtain a single crystal. Rhodium metalation of 10 Figure 2. Bis-rhodium complexes 11–13. was examined to rigidify the hexaphyrin framework. By stirring 10 in CH2Cl2 in the presence of [{RhCl(CO)2}2] (5 equiv) and NaOAc (10 equiv), the bis-rhodium [28]hexaphyrin complex 11 was yielded in 73 % (Figure 2). X-ray diffraction studies revealed that 11 adopts a bent-rectangular structure with a dihedral angle of 131.48, in which the {Rh(CO)2} groups are bound to the convex side and the 3,5-di-tert-butyl-4-hydroxyphenyl groups are tilted with respect to the hexaphyrin framework with dihedral angles of 54.7 and 56.18 (Figure 3). The 1H NMR spectrum of 11 displays four doublets due to the outer pyrrolic b-protons in the range of d = 3.23–4.55 ppm, a singlet due to the outer NH-protons at d = 2.92 ppm, and two doublets due to the inner b-protons at d = 18.65 and 18.68 ppm, thus indicating a strong paratropic ring current that arises from Hckel antiaromaticity. The chemical-shift difference, defined as the difference between the chemical shifts of the most shielded and deshielded protons, is Dd = 15.76 ppm and is slightly larger than that of 6 (i.e., Dd = 13.83 ppm). Oxidation of complex 11 with an excess amount of DDQ gave the quinonoidal rhodium hexaphyrin complex 12 quantitatively (Figure 2). X-ray diffraction studies revealed that the structure of 12 is bent with a dihedral angle of 103.28, in which the two OCH groups are located at the long sides and held in a nearly coplanar manner to the hexaphyrin frame with a dihedral angle of 3.058 and the C=O bond length is 1.254 (Figure 3; see the Supporting Information). In accord with the quinonoidal, cross-conjugated electronic network, the 1H NMR spectrum of 13 shows signals due to the pyrrolic b-protons in Figure 3. X-ray crystal structures of a) 11, b) 12, and c) 13. Left: top view; the range of d = 6.56–7.90 ppm, thus indicating its nonaromatright: side view. The thermal ellipsoids have been scaled to the 40 % probaic nature. bility level for 11 and 12 and 30 % probability level for 13. The solvent moleIn addition, we found that careful oxidation of 11 cules have been omitted for clarity. with one equivalent of DDQ furnished complex 13 almost quantitatively. Interestingly, 13 has both 3,5di-tert-butyl-4-hydroxyphenyl and OCH groups on the long side of the hexaphyrin framework, which is a rare case (Scheme 3). The structure of 13 was confirmed by X-ray diffraction studies to be roughly planar but bent with a dihedral angle of 133.18. The 3,5-di-tert-butyl-4-hydroxyphenyl group is tilted with respect to the hexaphyrin framework with a dihedral angle of 63.488, but the OCH group is nearly coplanar with a dihedral angle of 3.168. The C=O and C O bond lengths are 1.216 and 1.372 , respectively. The Scheme 3. Possible resonance of 13. Bold line represents a 26 p aromatic circuit of hexapresence of one OCH group causes disruption of the phyrin. Chem. Eur. J. 2014, 20, 1 – 9
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Full Paper To investigate the photophysical properties, the excitedstate dynamics of the rhodium complexes 11–13 in toluene were examined by transient absorption measurement. In the case of 11 and 13, within an initial time delay of 2 ps, the excited-state absorption (ESA) signals shift to the higher energy region, which generally represent energy-relaxation processes from the higher excited state to the lowest excited state. In other words, the ultrafast lifetime components (~ 1 ps) could have originated from the vibrational relaxation process in the excited states. The slow excited-state lifetime components of 400 and 600 ps for 11 and 13, respectively, could be assigned to the triplet-state lifetime because the fluorescence of 11 and 13 were not observed. The difference in the lifetimes between 11 and 13 is consistent with their aromatic features, that is, the antiaromaticity and aromaticity of 11 and 13, respectively.[10] Interestingly, 13 reveals more fast decay profiles than the previous rhodium complex of [26]hexaphyrin 5, which has a well-defined 26 p electronic circuit (see Figure S26 in the Supporting Information).[9] Furthermore, the triplet-state lifetime of 13 increases in DMSO (1300 ps) (Figure 5). Because the molecules that have well-defined p-conjugation show a long excited-state lifetime, these results also support a contribution of an aromatic zwitterionic resonance hybrid that encompasses a 26 p electronic circuit.
cyclic conjugated network (cross-conjugation). Despite this situation, the 1H NMR spectrum of 13 in CDCl3 indicates a substantial diatropic ring current by displaying four doublets due to the inner b-protons in a high-field range of d = 4.36– 4.80 ppm, eight doublets due to the outer b-protons in a lowfield range of d = 6.89–7.38 ppm, thus leading to determination of Dd = 3.02 ppm. This data may imply a contribution of an aromatic zwitterionic resonance hybrid that encompasses a 26 p electronic circuit (Scheme 3). In line with this hypothesis, the Dd value becomes larger upon increasing the polarity of the surrounding medium, that is, d = 3.30, 3.99, and 4.68 ppm in benzene, acetone, and dimethyl sulfoxide (DMSO), respectively. The absorption spectra of 11–13 are superimposed in Figure 4. The absorption spectrum of 11 does not have Q-like
Conclusion A hexaphyrin carrying two meso-OCH groups 9 has been prepared as the first example of a cross-conjugated hexaphyrin. Although quinonoidal hexaphyrin 9 is nonaromatic, its reduction product 10 displays Mçbius aromatic character. Bis-rhodium hexaphyrin complexes 11–13 were also synthesized and structurally well characterized. Complexes 11 and 12 were assigned as a Hckel antiaromatic molecule and a nonaromatic molecule, respectively. Unexpectedly, complex 13 exhibits a moderate diatropic ring current despite its cross-conjugated electronic network. The diatropic ring current of 13 increases upon increasing the polarity of the surrounding medium, thus suggesting a contribution from an aromatic zwitterionic resonance hybrid. Efforts are now devoted to the exploration of novel cross-conjugated porphyrinoids that possess larger pelectronic systems, which will be reported in due course.
Figure 4. UV/Vis/NIR absorption spectra of compounds 9–13 in CH2Cl2.
bands and that of 12 is more ill-defined, in line with their respective antiaromatic and nonaromatic natures. On the other hand, the absorption spectrum of 13 shows Soret-like bands at l = 519 and 628 nm and Q-like bands at l = 858 and 1033 nm with relatively strong intensities, thus probably reflecting partially forgiven HOMO–LUMO transitions that arise from an aromatic zwitterionic resonance contribution. Electrochemical studies were performed by using cyclic voltammetry (see the Supporting Information). The quinonoidal hexaphyrins 9 and 12 exhibited four and five reversible reduction waves, thus indicating multiple electron-accepting abilities. The electrochemical HOMO–LUMO gaps of 9 and 12 are 1.45 and 1.44 eV, respectively, thus reflecting their disrupted cyclic conjugation. Hexaphyrins 10 and 11 showed two reduction waves and four and three oxidation waves. The electrochemical HOMO–LUMO gaps of 10 and 11 are distinctly smaller (i.e., 1.10 and 0.86 eV, respectively), which are in line with the aromatic and antiaromatic natures. The nonsymmetric hexaphyrin bis-rhodium complex 13 displayed four reduction waves and three oxidation waves. More importantly, the HOMO–LUMO gap of 13 is relative small (0.99 eV), thus suggesting that the cyclic conjugative network is somewhat effective in 13. &
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Experimental Section Instrumentation and materials All the reagents were of the commercial reagent grade and were used without further purification, except where noted. Column chromatography on silica gel was performed on Wakogel C-200, C300, or C-400. TLC analysis was carried out on aluminum sheets coated with silica gel 60 F254 (Merck 5554). UV/Vis spectra were recorded on a Shimadzu UV-3600PC spectrometer. 1H and 19F NMR spectra were recorded on a JEOL ECA-600 spectrometer (operating at 600.17 and 564.73 MHz for 1H and 19F, respectively) with the residual solvent as the internal reference for 1H (d = 7.26 ppm in CDCl3) and hexafluorobenzene as the external reference for 19F (d = 162.9 ppm). High-resolution electrospray-ionization time-of-
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Full Paper atmosphere, and the reaction mixture was stirred for 1 h. DDQ (1.2 g, 3 equiv) was added to the mixture, which was stirred for 30 min at room temperature. The resulting solution was passed through a short column of basic alumina with CH2Cl2/AcOEt (10:1) as the eluent. The solvent was removed under reduced pressure and the product was separated by column chromatography on silica gel with CH2Cl2/hexane (1:1) as the eluent. A brown fraction was collected and evaporated to dryness. Recrystallization of the product from CH2Cl2/hexane afforded 9 (231 mg, 17 %). 1H NMR (CDCl3, 600.17 MHz): d = 14.12 (s, 2 H; inner NH), 8.23 (s, 4 H; vinylH), 7.02 (d, J = 4.6 Hz, 4 H; outer-b H), 6.82 (d, J = 4.6 Hz, 4 H; outerb H), 6.46 ppm (d, J = 1.8 Hz, 4 H; outer-b H); 19F NMR (CDCl3, 564.73 MHz): d = 134.8 (d, J = 23.0 Hz, 4 F; ortho-F), 137.5 (d, J = 28.0 Hz, 4 F; ortho-F), 150.1 (t, J = 23.0 Hz, 4 F; para-F), 160.1 ppm (m, 8 F; meta-F); HR-ESI-MS: m/z calcd for 12 C821H5414N616O219F20 : 1535.4062 [M + H] + ; found: 1535.4026; UV/Vis/ NIR absorption spectrum in CH2Cl2 : lmax (e) = 359 (87 300), 711 nm (11 700 m 1 cm 1); single crystals suitable for X-ray diffraction studies were obtained by recrystallization from chlorobenzene/nonane.
Crystal data for 9 C82H54F20N6O2, Mw = 1535.31, monoclinic, space group: P21/n (No. 14), a = 9.0726(2), b = 21.7060(4), c = 18.0976(4) , b = 103.7954(8)8, V = 3461.15(13) 3, Z = 2, T = 93(2) K, Dcalcd = 1.473 g cm 3, R1 = 0.0428 [I > 2s(I)], Rw = 0.1557 (all data), GOF = 1.045.
[28]Hexaphyrin 10 NaBH4 was added slowly to a solution of 9 in CH2Cl2/MeOH (10:1) at 0 8C. After consumption of the starting material was confirmed by TLC analysis, the reaction mixture was quenched with H2O and saturated NH4Cl solution. The product was extracted with CH2Cl2. The organic layer was collected, dried over anhydrous Na2SO4, and concentrated to a clear blue solid. Recrystallization from CH2Cl2/ hexane gave 10 in almost quantitative yield. 1H NMR (CDCl3, 600.17 MHz, room temperature): d = 8.20 (br), 7.78 (d, J = 4.1 Hz; outer-b H), 7.59 (br), 7.17 (br), 5.42 (s), 1.32 ppm (s); 19F NMR (CDCl3, 564.73 MHz, room temperature): d = 137.2 (br, 4 F; orthoF), 137.8 (s, 4 F; ortho-F), 152.6 (t, J = 17.3 Hz, 4 F; para-F), 153.9 (br, 2 F; para-F), 160.9 (br, 4 F; meta-F), 161.8 ppm (t, J = 17.3 Hz, 4 F; meta-F); 1H NMR (CDCl3, 600.17 MHz, 60 8C): d = 10.60 (br), 8.01 (br), 7.88 (br), 7.83 (br), 7.79 (s), 7.52 (br), 7.45 (br), 7.43 (s), 5.63 (s), 1.40 (s), 0.60 (br), 1.50 ppm (br); 19F NMR (CDCl3, 564.73 MHz, 60 8C): d = 136.8 (br; ortho-F), 137.3 (s; ortho-F), 137.5 (s; ortho-F), 151.5 (br; para-F), 152.8 (s; para-F), 153.1 (br; para-F), 159.5 (br; meta-F), 160.9 ppm (s; meta-F); 1 H NMR ([D8]THF, 600.17 MHz, room temperature): d = 11.80 (br), 10.80 (s), 10.52 (s), 10.48 (s), 10.30 (s), 10.12 (s), 9.52 (s), 9.45 (br), 7.92 (s), 7.75 (d, J = 4.6 Hz; outer-b H), 7.64 (br), 7.47 (br), 7,32 (s), 7.01 (d, J = 4.1 Hz; outer-b H), 6.92 (s), 6.82 (s), 6.73 (d, J = 17.9 Hz), 6.63 (s), 6.60 (d, J = 4.6 Hz; outer-b H), 6.52 (s), 6.37 (s), 6.28 (s), 5.79 (s), 5.49 (s), 1.40 ppm (s); 19F NMR ([D8]THF, 564.73 MHz, room temperature): d = 139.22 (s; ortho-F), 140.1 (s; ortho-F), 140.7 (br; ortho-F), 141.2 (br; ortho-F), 142.5 (br; ortho-F), 157.2 (m; para-F), 157.6 (t, J = 21.7 Hz; para-F), 157.8 (t, J = 21.7 Hz; paraF), 158.6 (t, J = 21.7 Hz; para-F), 163.6 (br; meta-F), 164.0 (m; meta-F), 164.5 (t, J = 17.3 Hz; meta-F), 164.6 ppm (t, J = 17.3 Hz; meta-F); 1H NMR ([D8]THF, 600.17 MHz, 20 8C): d = 12.03 (br), 11.01 (s), 10.70 (s), 10.46 (s), 10.40 (s), 10.19 (s), 9.93 (s), 9.75 (s), 7.92 (s), 8.24 (s), 7.98–8.11 (br), 7.89 (s), 7.81 (d, J = 3.9 Hz; outer-b H), 7.73 (s), 7.71 (s), 7.50–7.66 (br), 7.43 (s), 7.24–7.36 (br), 7.04 (d, J = 4.1 Hz), 7.00 (s), 6.90–6.96 (br), 6.90 (s), 6.84 (s), 6.75 (d, J = 3.7 Hz), 6.71 (s), 6.66 (t, J = 5.0 Hz; outer-b H), 6.47 (s), 6.43 (s), 6.35 (d, J =
Figure 5. Femtosecond (fs) transient absorption spectra (top) and decay profiles (bottom) of 13 in toluene (a) and DMSO (b).
flight mass spectroscopy (HR-ESI-TOF-MS) was recorded on a BRUKER microTOF model with positive and negative modes for solutions of samples in acetonitrile. Redox potentials were measured by cyclic voltammetry on an ALS electrochemical analyzer model 660. Crystallographic data were collected on a Rigaku RAXIS-RAPID and XtaLAB P200 apparatus at 180 8C with graphitemonochromated CuKa radiation (l = 1.54187 ). The structures were solved by direct method SIR- 97 and refined by means of the SHELXL-97 program.
Quinoidal hexaphyrin 9 MSA (2.5 m diluted with CH2Cl2, 45 mL, 12.5 mol %) was added to a solution of 5,10-bis(pentafluorophenyl)tripyrrane (7; 1.0 g, 1.8 mmol) and 3,5-di-tert-butyl-4-hydroxybenzaldehyde (8; 420 mg, 1.8 mmol, 1 equiv) in CH2Cl2 (180 mL) at 0 8C under nitrogen Chem. Eur. J. 2014, 20, 1 – 9
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5.5 Hz; outer-b H), 6.32 (d, J = 5.0 Hz; outer-b H), 6.17 (d, J = 3.7 Hz; outer-b H), 5.71 (s), 5.26 (s), 1.39 (s), 1.31 (s), 1.25 (s), 1.23 (s), 1.17 ppm (s); 19F NMR ([D8]THF, 564.73 MHz, 20 8C): d = 138.9 (br; ortho-F), 139.4 (s; ortho-F), 139.8 (br; ortho-F), 140.1 (br; ortho-F), 140.3 (d, J = 26.0 Hz; ortho-F), 140.6 (d, J = 26.0 Hz; ortho-F), 141.0 (br; ortho-F), 141.3 (d, J = 21.7 Hz; ortho-F), 141.6 (br; ortho-F), 141.8 (br; ortho-F), 142.5 (d, J = 17.3 Hz; ortho-F), 157.0 (br; para-F), 157.4 (t, J = 16.8 Hz; para-F), 157.6 (t, J = 16.8 Hz; para-F), 157.8 (br; para-F), 157.9 (m; para-F), 158.0 (t, J = 21.7 Hz; para-F), 157.6 (t, J = 16.8 Hz; para-F), 159.1 (t, J = 21.7 Hz; para-F), 163.7 (t, J = 21.6 Hz; meta-F), 163.9 (t, J = 17.3 Hz; meta-F), 164.1 (t, J = 21.6 Hz; meta-F), 164.3 (t, J = 17.3 Hz; meta-F), 164.5(s; meta-F), 164.7 ppm (s; meta-F); 1H NMR ([D8]THF, 600.17 MHz, 100 8C): d = 12.72 (s), 12.45 (s), 11.63 (s), 11.05 (s), 10.67 (s), 10.11(s), 8.88 (s), 8.50 (s), 8.46 (s), 8.30 (s), 8.25 (s), 8.07 (s), 8,03 (s), 7.93 (s), 7.87 (s), 7.79 (s), 7.76 (s), 7.63 (s), 7.60 (s), 7.54 (s), 7.51 (s), 7.45 (s), 7,40 (s), 7.08 (s), 7.07 (s), 7.02 (s), 7.00 (d, J = 5.0 Hz; outer-b H), 6.94 (s), 6.88 (d, J = 5.0 Hz; outer-b H), 6.83 (s), 6.79 (s), 6.60 (s), 6.51 (d, J = 5.0 Hz; outer-b H), 6.46 (d, J = 4.6 Hz; outer-b H), 6.42 (s), 6.26 (s), 6.15 (s), 5.55 (s), 4.97 (s), 4.88 (s), 4.79 (s), 1.00–1.50 (br), 0.77 ppm (s); 19F NMR ([D8]THF, 564.73 MHz, 100 8C): d = 138.4 (s; ortho-F), 138.6 (s; ortho-F), 138.9 (s; ortho-F), 139.3 (s; ortho-F), 139.5 (s; ortho-F), 139.9 (s; ortho-F), 140.3 (s; ortho-F), 140.6 (s; ortho-F), 140.9 (s; ortho-F), 141.0 - 141.5 (br; ortho-F), 142.1 (s; ortho-F), 142.7 (s; ortho-F), 157.6 (s; para-F), 158.0 (s; para-F), 158.0 - 159.0 (br; para-F), 159.7 (s; para-F), 163.5 (s; meta-F), 163.8 (s; metaF), 164.2 (s; meta-F), 164.6 (s; meta-F), 165.1 ppm (s; meta-F); HR-ESI-MS: m/z calcd for 12C821H5814N616O219F20 : 1539.4375 [M + H] + ; found: 1539.4412; UV/Vis/NIR absorption spectrum in CH2Cl2 : lmax (e) = 309 (24 600), 408 (37 800), 617 (146 300), 783 (10 600), 887 nm (7000 m 1 cm 1).
Rhodium complex of quinoidal hexaphyrin 12 DDQ (excess) was added to a solution of hexaphyrin 11 in CH2Cl2 at room temperature in air, and the reaction mixture was stirred for 5 min. The resulting solution was passed through a short column of basic alumina with CH2Cl2 as the eluent. The solvent was removed under reduced pressure. Recrystallization from CH2Cl2/hexane gave 12 as a dark-green solid in almost quantitative yield. 1H NMR (CDCl3, 600.17 MHz): d = 9.19 (d, J = 2.8 Hz, 2 H; vinyl H), 8.05 (d, J = 4.6 Hz, 2 H; inner-b H), 7.90 (d, J = 4.6 Hz, 2 H; innerb H), 6.87 (d, J = 2.8 Hz, 2 H; vinyl H), 6.77 (m, 4 H; outer-b H), 6.71 (d, J = 4.6 Hz, 2 H; outer-b H), 6.56 (d, J = 4.6 Hz, 2 H; outer-b H), 1.19 (s, 18 H; tBu), 0.98 ppm (s, 18 H; tBu); 19F NMR (CDCl3, 564.73 MHz): d = 134.1 (d, J = 21.6 Hz, 2 F; ortho-F), 136.1 (d, J = 21.7 Hz, 2 F; ortho-F), 137.6 (d, J = 21.7 Hz, 2 F; ortho-F), 138.0 (d, J = 21.7 Hz, 2 F; ortho-F), 150.4 (t, J = 21.6 Hz, 2 F; para-F), 150.7 (t, J = 21.7 Hz, 2 F; para-F), 159.5 (dt, J = 8.6, 21.6 Hz, 2 F; meta-F), 159.8 (dt, J = 8.5, 21.7 Hz, 2 F; meta-F), 161.3 (dt, J = 8.6, 21.6 Hz, 2 F; meta-F), 162.0 ppm (dt, J = 8.6, 21.6 Hz, 2 F; meta-F); HR-ESI-MS: m/z calcd for 12C861H5214N616O619F20102Rh2 : 1851.1812 [M + H] + ; found: 1851.1792; UV/Vis/NIR absorption spectrum in CH2Cl2 : lmax (e) = 344 (40 000), 422 (48 500), 513 (36 600), 610 (38 900), 735 nm (42 000 m 1 cm 1); single crystals suitable for X-ray diffraction studies were obtained by recrystallization from CHCl3/MeOH.
Crystal data for 12 C86H52F20N6O6Rh2, Mw = 925.58, orthorhombic, space group: F d d 2 (No. 43), a = 42.24(5), b = 55.30(6), c = 6.440(7) , V = 15 043(29) 3, Z = 16, T = 93(2) K, Dcalcd = 1.635 g cm 3, R1 = 0.1232 [I > 2s(I)], Rw = 0.3558 (all data), GOF = 1.057.
Rhodium complex of hexaphyrin 11 NaOAc (20 mg, 10 equiv) and [{RhCl(CO)2}2] (60 mg, 6 equiv) were added to a solution of hexaphyrin 10 (40 mg, 26 mmol) in CH2Cl2 (20 mL) at room temperature in a nitrogen atmosphere, and the reaction mixture was stirred for 1 h. The solvent was removed under reduced pressure, and the crude mixture was separated by column chromatography on silica gel with CH2Cl2/hexane (1:1) as the eluent. The first violet fraction was collected and evaporated to dryness. Recrystallization from CH2Cl2/hexane afforded 11 (35 mg, 73 %) as a dark-reddish solid. 1H NMR (CDCl3, 600.17 MHz): d = 18.68 (d, J = 5.0 Hz, 2 H; inner-b H), 18.65 (d, J = 5.5 Hz, 4 H; innerb H), 6.03 (s, 4 H; Ar-H), 5.06 (s, 2 H; OH), 4.55 (d, J = 4.6 Hz, 2 H; outer-b H), 4.39 (d, J = 4.6 Hz, 2 H; outer-b H), 3.32 (d, J = 4.0 Hz, 2 H; outer-b H), 3.23 (d, J = 4.6 Hz, 2 H; outer-b H), 2.92 (s, 2 H; outer NH), 1.13 ppm (s, 36 H; tBu); 19F NMR (CDCl3, 564.73 MHz): d = 132.2 (s, 2 F; ortho-F), 137.9 (s, 2 F; ortho-F), 139.3 (d, J = 21.7 Hz, 2 F; ortho-F), 140.1 (d, J = 17.3 Hz, 2 F; ortho-F), 153.4 (t, J = 17.3 Hz, 2 F; para-F), 153.7 (t, J = 21.7 Hz, 2 F; para-F), 158.3 (s, 2 F; meta-F), 158.7 (s, 2 F; meta-F), 160.2 (dt, J = 8.7, 21.7 Hz, 2 F; meta-F), 160.2 ppm (dt, J = 8.7, 21.7 Hz, 2 F; meta-F); HR-ESIMS: m/z calcd for 12C861H5614N616O619F20102Rh2 : 1854.2047 [M] + ; found: 1854.2042; UV/Vis/NIR absorption spectrum in CH2Cl2 : lmax (e) = 369 (31100), 539 (108 600), 584 (98 400), 692 nm (23 800 m 1 cm 1); single crystals suitable for X-ray diffraction studies were obtained by recrystallization from CHCl3/heptane.
Rhodium complex of quinoidal hexaphyrin 13 DDQ (1 equiv) was added to a solution of hexaphyrin 11 in CH2Cl2 at room temperature in air, and the reaction mixture was stirred for 5 min. The resulting solution was passed through a short column of basic alumina with CH2Cl2/AcOEt (10:1) as the eluent. The solvent was removed under reduced pressure. The product can be further purified by chromatography on silica gel 60N (spherical, neutral) if needed. Recrystallization from CHCl3/octane afforded 13 as a blue solid in almost quantitative yield.1H NMR ([D6]benzene, 600.17 MHz): d = 10.01 (d, J = 2.3 Hz, 1 H; vinyl-H), 8.81 (s, 1 H; NH), 7.74 (s, 2 H; Ar-H), 7.40 (d, J = 4.6 Hz, 1 H; outerb H), 7.18 (d, J = 4.6 Hz, 4 H; outer-b H), 7.14 (d, J = 4.6 Hz, 1 H; outer-b H), 7.08 (m, 2 H; outer-b H), 7.05 (d, J = 4.1 Hz, 1 H; outerb H), 6.99 (d, J = 2.3 Hz, 1 H; vinyl-H), 6.87 (d, J = 4.1 Hz, 1 H; outerb H), 6.76 (d, J = 4.1 Hz, 1 H; outer-b H), 5.31 (s, 1 H; OH), 4.65 (dd, J = 1.8, 5.0 Hz, 1 H; inner-b H), 4.63 (d, J = 4.6 Hz, 1 H; inner-b H), 4.46 (d, J = 4.6 Hz, 1 H; inner-b H), 4.10 (dd, J = 1.8, 5.0 Hz, 1 H; inner-b H), 1.47 (s, 9 H; tBu), 1.36–1.41 (br, 18 H; tBu), 1.38 ppm (s, 9 H; tBu); 19F NMR ([D6]benzene, 564.73 MHz): d = 134.4 (d, J = 21.7 Hz, 1 F; ortho-F), 135.6 (d, J = 21.6 Hz, 1 F; ortho-F), 137.1 (d, J = 21.6 Hz, 1 F; ortho-F), 138.1 (d, J = 21.7 Hz, 1 F; ortho-F), 138.5 (d, J = 21.6 Hz, 2 F; ortho-F), 139.3 (d, J = 26.0 Hz, 1 F; ortho-F), 139.5 (d, J = 21.7 Hz, 1 F; ortho-F), 150.3 (t, J = 21.7 Hz, 1 F; para-F), 150.9 (t, J = 21.7 Hz, 1 F; para-F), 151.4 (m, 2 F; para-F), 156.6 (t, J = 17.3 Hz, 1 F; meta-F), 158.6 (t, J = 21.6 Hz, 1 F; meta-F), 160.0 (dt, J = 8.6, 21.7 Hz, 1 F; meta-F), 160.1 (dt,
Crystal data for 11 (C86H56F20N6O6Rh2)2·(C24H56)0.35·(CHCl3)2.6·(O)2, Mw = 2086.69, triclinic, space group: P-1 (No. 2), a = 15.615(6), b = 18.062 (6), c =
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Full Paper 1033 nm (10 900 m 1 cm 1); single crystals suitable for X-ray diffraction studies were obtained by recrystallization from CHCl3/octane.
J = 8.6, 21.7 Hz, 1 F; meta-F), 160.5 (dt, J = 8.6, 21.7 Hz, 1 F; metaF), 160.7 (dt, J = 8.6, 21.7 Hz, 1 F; meta-F), 161.6 (t, J = 17.3 Hz, 1 F; meta-F), 162.6 ppm (t, J = 21.7 Hz, 1 F; meta-F); 1H NMR (CDCl3, 600.17 MHz): d = 9.52 (d, J = 2.3 Hz, 1 H; vinyl-H), 8.78 (s, 1 H; NH), 7.45 (s, 2 H; Ar-H), 7.38 (d, J = 4.6 Hz, 1 H; outer-b H), 7.35 (d, J = 4.6 Hz, 4 H; outer-b H), 7.32 (d, J = 4.1 Hz, 1 H; outer-b H), 7.28 (d, J = 4.6 Hz, 1 H; outer-b H), 7.21 (d, J = 4.6 Hz, 1 H; outerb H), 7.19 (d, J = 4.6 Hz, 1 H; outer-b H), 6.97 (d, J = 4.6 Hz, 1 H; outer-b H), 6.89 (d, J = 4.6 Hz, 1 H; outer-b H), 6.71 (d, J = 2.7 Hz, 1 H; vinyl-H), 5.60 (s, 1 H; OH), 4.80 (dd, J = 1.9, 5.0 Hz, 1 H; innerb H), 4.64 (d, J = 4.1 Hz, 1 H; inner-b H), 4.49 (dd, J = 1.8, 5.0 Hz, 1 H; inner-b H), 4.36 (d, J = 4.6 Hz, 1 H; inner-b H), 1.51 (s, 18 H; tBu), 1.22 (s, 9 H; tBu), 1.04 ppm (s, 9 H; tBu); 19F NMR (CDCl3, 564.73 MHz): d = 134.2 (d, J = 21.7 Hz, 1 F; ortho-F), 135.4 (d, J = 21.6 Hz, 1 F; ortho-F), 136.4 (d, J = 21.6 Hz, 1 F; ortho-F), 136.5 (d, J = 26.0 Hz, 1 F; ortho-F), 137.1 (d, J = 21.6 Hz, 1 F; ortho-F), 138.1 (d, J = 21.7 Hz, 1 F; ortho-F), 138.2 (d, J = 21.7 Hz, 1 F; ortho-F), 138.6 (d, J = 21.6 Hz, 1 F; ortho-F), 150.4 (t, J = 21.7 Hz, 1 F; para-F), 151.4 (t, J = 21.7 Hz, 1 F; para-F), 151.6 (t, J = 21.7 Hz, 1 F; para-F), 152.1 (t, J = 21.7 Hz, 1 F; para-F), 157.3 (t, J = 17.3 Hz, 1 F; meta-F), 158.2 (t, J = 17.3 Hz, 1 F; meta-F), 160.3 (t, J = 17.3 Hz, 1 F; meta-F), 160.5 (t, J = 17.3 Hz, 1 F; meta-F), 160.6 (t, J = 17.3 Hz, 1 F; meta-F), 160.8 (t, J = 17.3 Hz, 1 F; metaF), 161.8 (t, J = 17.3 Hz, 1 F; meta-F), 162.6 ppm (t, J = 17.3 Hz, 1 F; meta-F); 1H NMR ([D6]acetone, 600.17 MHz): d = 12.13 (s, 1 H; NH), 9.71 (d, J = 2.3 Hz, 1 H; vinyl-H), 7.87 (d, J = 4.6 Hz, 1 H; outerb H), 7.82 (d, J = 4.1 Hz, 1 H; outer-b H), 7.80 (d, J = 5.0 Hz, 1 H; outer-b H), 7.68 (d, J = 5.0 Hz, 1 H; outer-b H), 7.67 (d, J = 5.0 Hz, 1 H; outer-b H), 7.60 (d, J = 4.1 Hz, 1 H; outer-b H), 7.49 (d, J = 4.6 Hz, 1 H; outer-b H), 7.90–7.40 (br, 2 H; Ar-H), 7.18 (d, J = 5.0 Hz, 1 H; outer-b H), 6.87 (d, J = 2.3 Hz, 1 H; vinyl-H), 6.59 (s, 1 H; OH), 4.37 (d, J = 5.0 Hz, 1 H; inner-b H), 4.18 (d, J = 4.6 Hz, 1 H; innerb H), 3.98 (d, J = 5.0 Hz, 1 H; inner-b H), 3.88 (d, J = 4.6 Hz, 1 H; inner-b H), 1.48–1.60 (br, 18 H; tBu), 1.23 (s, 9 H; tBu), 1.05 ppm (s, 9 H; tBu); 19F NMR ([D6]acetone, 564.73 MHz): d = 137.0 (d, J = 21.7 Hz, 1 F; ortho-F), 139.1 (d, J = 21.7 Hz, 1 F; ortho-F), 140.2 (m, 2 F; ortho-F), 141.2 (d, J = 21.7 Hz, 1 F; ortho-F), 141.4 (d, J = 17.3 Hz, 1 F; ortho-F), 141.8 (d, J = 21.7 Hz, 1 F; ortho-F), 155.3 (t, J = 21.7 Hz, 1 F; para-F), 155.6 (t, J = 21.6 Hz, 1 F; para-F), 156.2 (t, J = 17.3 Hz, 1 F; para-F), 163.6 (m, 2 F; meta-F), 163.7 (t, J = 21.7 Hz, 1 F; meta-F), 163.9 (dt, J = 8.6, 21.6 Hz, 1 F; meta-F), 164.5 (t, J = 21.7 Hz, 1 F; meta-F), 164.7 (t, J = 21.7 Hz, 1 F; metaF), 165.2 ppm (dt, J = 8.6, 21.6 Hz, 1 F; meta-F); 1H NMR ([D6]DMSO, 600.17 MHz): d = 12.95 (s, 1 H; NH), 9.62 (s, 1 H; vinyl-H), 8.02 (d, J = 4.5 Hz, 1 H; outer-b H), 7.88 (d, J = 3.7 Hz, 1 H; outerb H), 7.85 (m, 1 H; outer-b H), 7.80 (d, J = 3.7 Hz, 1 H; outer-b H), 7.78 (d, J = 3.7 Hz, 1 H; outer-b H), 7.70 (d, J = 3.4 Hz, 1 H; outerb H), 7.61 (d, J = 3.7 Hz, 1 H; outer-b H), 7.58 (s, 2 H; Ar-H), 7.18 (d, J = 4.8 Hz, 1 H; outer-b H), 6.76 (s, 1 H; vinyl-H), 5.77 (s, 1 H; OH), 3.82 (s, 1 H; inner-b H), 3.73 (s; inner-b H), 3.41 (s, 1 H; inner-b H), 3.34 (s, 1 H; inner-b H), 1.23 (s, 9 H; tBu), 1.18 (s, 18 H; tBu), 0.97 ppm (s, 9 H; tBu); 19F NMR ([D6]DMSO, 564.73 MHz): d = 136.2 (d, J = 21.6 Hz, 1 F; ortho-F), 138.3 (d, J = 21.6 Hz, 1 F; ortho-F), 139.6 (d, J = 21.8 Hz, 1 F; ortho-F), 139.7 (d, J = 26.8 Hz, 1 F; ortho-F), 140.2 (d, J = 25.8 Hz, 1 F; ortho-F), 140.4 (d, J = 21.8 Hz, 1 F; ortho-F), 140.7 (d, J = 21.8 Hz, 1 F; ortho-F), 140.9 (d, J = 20.8 Hz, 1 F; ortho-F), 154.0 - 153.7 (m, 3 F; para-F), 155.8 (t, J = 21.5 Hz, 1 F; para-F), 159.4 (t, J = 21.6 Hz, 1 F; meta-F), 161.7 (m, 2 F; meta-F), 162.0 (t, J = 21.0 Hz, 1 F; meta-F), 162.2 (t, J = 21.0 Hz, 1 F; meta-F), 162.9 (t, J = 17.7 Hz, 1 F; meta-F), 163.8 (t, J = 21.0 Hz, 1 F; meta-F), 163.9 ppm (t, J = 22.1 Hz, 1 F; meta-F); HR-ESI-MS: m/z calcd for 12C861H5414N616O619F20102Rh2 : 1853.1968 [M + H] + ; found: 1853.1951; UV/Vis/NIR absorption spectrum in CH2Cl2 : lmax (e) = 350 (32 900), 519 (61100), 628 (79 400), 858 (13 800), Chem. Eur. J. 2014, 20, 1 – 9
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Crystal data for 13 C86H54F20N6O6Rh2·(C8H18)2·(CHCl3)0.36·(O)0.64, Mw = 2135.09, triclinic, space group: P-1 (No. 2), a = 15.703(12), b = 17.917(12), c = 20.081(12) , a = 107.82, b = 101.202(12), g = 106.29(2)8, V = 4914(6) 3, Z = 2, T = 93(2) K, Dcalcd = 1.443 g cm 3, R1 = 0.0918 [I > 2s(I)], Rw = 0.2877 (all data), GOF = 1.026. CCDC-988116 (9), 988117 (11), 988118 (12) and 988119 (13) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgements The work at Kyoto was supported by Grant-in-Aid (No. 25220802 (S)) for Scientific Research from MEXT of Japan. The work at Yonsei was supported by the Global Frontier R&D Program of the Center for Multiscale Energy System (2012–8– 2081) of National Research Foundation (NRF) grant funded by MEST of Korea, and AFSOR/AOARD grant (No. FA2386–09– 4092). This collaborative work is supported by the Global Research Laboratory Program (2013–8–1472) funded by the Ministry of Education, Science and Technology (MEST). Keywords: aromaticity · cross conjugation porphyrins · hexaphyrin · porphyrinoids
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Received: February 23, 2014 Published online on && &&, 0000
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2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!
Full Paper
FULL PAPER & Porphyrinoids
A good circuit: A cross-conjugated hexaphyrin that carries two meso-oxacyclohexadienyl (OCH) groups was prepared and reduced to a Mçbius aromatic [28]hexaphyrin. Bis-rhodium complexes of this system can take three different electronic states, one of which bears both a phenol and an OCH group, thus displaying a moderate diatropic ring current and probably reflecting a significant contribution of an aromatic zwitterionic resonance hybrid (see figure).
Chem. Eur. J. 2014, 20, 1 – 9
www.chemeurj.org
These are not the final page numbers! ÞÞ
K. Naoda, Y. M. Sung, J. M. Lim, D. Kim,* A. Osuka* && – && Cross-Conjugated Hexaphyrins and Their Bis-Rhodium Complexes
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2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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![Diprotonated [28]hexaphyrins(1.1.1.1.1.1): triangular antiaromatic macrocycles.](/assets/img/hold.png)
