Acetylenic scaffolding with subphthalocyanines - synthetic scope and elucidation of electronic interactions in dimeric structures.

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Received 00th January 20xx, Accepted 00th January 20xx DOI: 10.1039/x0xx00000x www.rsc.org/

Acetylenic scaffolding with subphthalocyanines – synthetic scope and elucidation of electronic interactions in dimeric structures a

a

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Henrik Gotfredsen, Line Broløs, Thomas Holmstrøm, Jacob Sørensen, Alberto Viñas Muñoz, a a a a Martin Drøhse Kilde, Anders B. Skov , Marco Santella, Ole Hammerich and Mogens Brøndsted a, Nielsen * Boron subphthalocyanines (SubPcs) are powerful chromophoric heterocycles that can be synthetically modified at both axial and peripheral positions. Acetylenic scaffolding offers the possibility of building large, unsaturated carbon-‐rich frameworks that can exhibit excellent electron-‐accepting properties, and when combined with SubPcs it poses a convenient way of preparing interesting chromophore-‐acceptor architectures. Here we present synthetic methodologies for post-‐functionalization of the relatively sensitive SubPc chromophore via acetylenic coupling reactions. By gentle AlCl3-‐ mediated alkynylation at the axial boron position, we managed to anchor two SubPcs to the geminal positions of a tetraethynylethene (TEE) acceptor. Convenient conditions that allow for stepwise desilylations of trimethylsilyl (TMS) and triisopropylsilyl (TIPS) protected SubPc-‐decorated acetylenes using silver(I) fluoride were developed. The resulting terminal alkynes were successfully used as coupling partners in metal-‐catalyzed couplings, providing access to larger acetylenic SubPc scaffolds and multiple chromophore systems. Moreover, conditions allowing for conversion of a terminal alkyne into an iodoalkyne in the presence of SubPc were developed, and the product was subjected to cross-‐coupling reactions affording unsymmetrical 1,3-‐butadiynes. The degree of interactions between two SubPc units as a function of the acetylenic bridge was studied by UV-‐Vis absorption spectroscopy and cyclic voltammetry. A TEE bridging unit was found to strongly influence the reductions and oxidations of the two SubPc units, while a more flexible bridge had no influence.

Introduction Boron subphthalocyanines (SubPcs) are 14π-‐electron aromatic heterocycles made up from three isoindole units fused 3 together by aza-‐bridges around a central sp -‐hybridized boron atom (Fig. 1a). The result of this arrangement is a characteristic bowl-‐like geometry giving SubPcs both a concave 1 and a convex surface. Since their discovery in 1972 by Meller 2 and Ossko, the interest in this class of dyes has increased significantly over the years due to their potential applications within areas such as photovoltaics, artificial photosynthesis 1 and photodynamic therapy. The properties of SubPcs are tunable via both axial and peripheral modifications, and development of suitable synthetic methodologies have been of 3-‐7 paramount importance to the advancement of the field. However, SubPcs are also known for their tendency to decompose in the presence of strong nucleophiles, rendering the conditions for many desirable transformations 1 troublesome or incompatible with this class of dyes.

a)

Axial Cl N N

N B

N

Peripheral

N

R

N SubPc-Cl b)

D hv

C A

E.T.

C*

C A

A

c)

D

D

C60

H

H

H

H TEE

Fig. 1 a) Boron subphthalocyanine chloride (SubPc-‐Cl); b) Principle of photoinduced electron transfer in donor (D) -‐ chromophore (C) -‐ acceptor (A) systems; c) Two electron-‐accepting units: C60 and tetraethynylethene (TEE).

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Multi-‐component systems combining SubPcs with suitable redox-‐active donors and acceptors have been prepared and studied for their ability to undergo photoinduced charge-‐ 8-‐13 separation (Fig. 1b). As acceptor unit, Buckminsterfullerene, 8,11-‐13 C60, is a popular choice. Another intriguing acceptor moiety for donor-‐chromophore-‐acceptor conjugates could be based on unsaturated carbon-‐rich frameworks constructed via acetylenic scaffolding. The tetraethynylethene (TEE; Fig. 1c) unit has been used as a versatile building block to access many large, unsaturated macrocycles like expanded radialenes or radiaannulenes that electrochemically have been 14,15 demonstrated to behave as potent electron acceptors. We recently initiated a pursuit on how to combine SubPc 6,16 chemistry and acetylenic scaffolding. This combination is challenging due to the sensitivity of the SubPc core. Here we present strategies for stepwise acetylenic coupling reactions along the peripheral and axial positions. We also demonstrate how electronic interactions between two SubPc units strongly depend on the acetylenic bridge separating them.

Results and discussion Our first objective was to explore the possibility of incorporating two SubPcs at a TEE scaffold by employing our 6 recently reported AlCl3-‐mediated protocol for alkynylation at the axial boron position. Thus, we carried out a double 17 2 alkynylation with the known TEE derivative 1 and SubPc-‐Cl furnishing the valuable SubPc-‐TEE-‐SubPc building block 2 (Scheme 1). Only reactions at the trimethylsilyl (TMS) end-‐ capped alkyne units were achieved, while no reactions occurred at the triisopropylsilyl (TIPS) sites. SubPc-Cl (2.3 equiv.)

TIPS

TIPS AlCl3

o-DCB, rt TMS

N N

TMS

1

N B

TIPS

TIPS

N

N

N

N

N

N B

N N

N 2 (63%)

Scheme 1 Synthesis of building block 2. o-‐DCB = ortho-‐dichlorobenzene.

The molecular structure of 2 was confirmed by X-‐ray crystallography, as suitable crystals were obtained from a 1:2 mixture of CH2Cl2 and MeOH (Fig. 2). The structure clearly shows the cone shape of each SubPc unit. The distance between the two boron atoms is 6.16 Å. While the C-‐C≡C-‐Si moieties are close to linear, the C-‐C≡C-‐B moieties deviate o significantly from linearity with C-‐C≡C angles of 171 . Despite the apparent crowdedness at the geminal TEE positions, the product 2 was isolated in a good yield of 63% under the gentle reaction conditions.

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DOI: 10.1039/C7OB01907F

Fig. 2 Molecular structure of 2; hydrogen atoms were omitted in the optimization (CCDC 1550013).

With 2 in hand, we wanted to demonstrate its possible use for incorporating SubPcs into larger acetylenic scaffolds via 18 19,20 either Sonogashira or modified Cadiot-‐Chodkiewicz coupling reactions. Initially, the TIPS-‐desilylation of 2 was attempted using tetrabutylammonium fluoride (TBAF), which, however, led to decomposition of the SubPc unit. Then, acidic conditions combining TBAF and acetic acid were attempted and later the use of potassium fluoride as another fluoride source. In these cases, decomposition did not occur but neither did desilylations. Finally, with inspiration from a 21 method by Kim et al. we successfully achieved complete desilylation of 2 using silver fluoride and acetic acid in a mixture of acetonitrile/dichloromethane followed by protonation with aqueous hydrochloric acid. Presumably, the deprotection proceeds via the double silver acetylide of 2 obtained from displacement of both TIPS groups by Ag(I). Attempts of isolating the doubly deprotected, terminal alkyne of 2 were unsuccessful, but it is known from literature that the TEE unit can become unstable when the silyl protection groups 17 are removed. For that reason, we decided to follow up the desilylation of 2 directly by Sonogashira couplings with 4-‐ iodonitrobenzene and 1,2-‐diiodo-‐4,5-‐bis(octyloxy)benzene, providing scaffolds 3 and 4, respectively (Scheme 2). The latter product may be further elaborated synthetically via the aryl iodides to extend the conjugation. For other Sonogashira 16 reactions with SubPc derivatives we have previously experienced improvements in reaction time and yields by employing Pd2dba3/AsPh3 rather than more commonly used catalysts such as Pd(PPh3)4 or PdCl2(PPh3)2. Gratifyingly, compound 2 also turned out to be a suitable precursor for modified Cadiot-‐Chodkiewicz couplings under Pd catalysis for achieving asymmetrical alkyne-‐alkyne couplings. When the product of the desilylation was subjected directly to the 22 iodoalkyne coupling partners 1-‐(iodoethynyl)-‐4-‐nitrobenzene 23 and 1-‐(iodoethynyl)-‐4-‐cyanobenzene , the SubPc-‐scaffolds 5 and 6 were formed, respectively (Scheme 2). It should be noted that the purification of the TEE scaffolds was somewhat tedious; analytically pure samples required repeated chromatographic purifications and recrystallizations.

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Scheme 2 Functionalization of 2 via AgF-‐mediated desilylation followed by either Sonogashira or modified Cadiot-‐Chodkiewicz couplings. Reaction conditions: a: 1) desilylation: AgF and AcOH in CH2Cl2/MeCN followed by HCl (aq), 2) 4-‐ iodonitrobenzene, Pd2dba3, AsPh3 and CuI in Et3N/toluene; b: 1) desilylation as in a, 2) 1,2-‐diiodo-‐4,5-‐bis(octyloxy)benzene, Pd2dba3, AsPh3 and CuI in Et3N/toluene; c: 1) desilylation as in a, 2) 1-‐ethynyl-‐4-‐nitrobenzene, Pd(PPh3)2Cl2 and CuI in Et3N/toluene; d: 1) desilylation as in a, 2) 1-‐ethynyl-‐4-‐cyanobenzene, Pd2dba3, AsPh3 and CuI in Et3N/toluene.

Acetylenic scaffolding in two directions can be made possible via SubPc building blocks having both axial and peripheral handles that allow for further transformations. 24,25 Torres and co-‐workers have shown that iodo-‐ functionalized SubPcs can be alkynylated at the peripheral positions via Sonogashira reactions, and we have recently shown that having an axially positioned alkyne works well for 16 coupling reactions along this direction. As peripheral handles we decided on aryl iodides and bromides. Starting from phthalonitrile and either 4-‐iodophthalonitrile 7 or the 4-‐(4-‐ bromophenyl) extended phthalonitrile 8, three bifunctional building blocks 9, 10 and 11 were synthesized (Scheme 3). Activation of the formed SubPc chlorides was achieved using 3 AgOTf according to the protocol by Guilleme et al. Building blocks 9 and 11 having unprotected terminal alkynes could 26 both be dimerized when subjected to oxidative Glaser-‐Hay coupling conditions to afford the SubPc dimers 12 and 13 with peripheral aryl iodide and bromide, respectively (Scheme 4).

X O N N

N B

N N

I

N

I

9 (15%, X = H) 10 (3%, X = TMS)

1) 7, BCl 3,o-DCB, reflux 2) AgOTf X HO NEt(i-Pr)2, PhMe

CN CN

7

CN

(excess) CN

Br

1) 8, BCl 3, o-DCB, reflux 2) AgOTf H HO NEt(i-Pr)2, PhMe

CN

8

CN

H O

N N

N B N

N

11 (3%)

N

Br

Scheme 3 Synthesis of building blocks 9, 10 and 11 in a two-‐step sequence consisting of a mixed phthalonitrile cyclotrimerization followed by axial functionalization.


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R

O N N

N B

N N

N 9 or 11

CuCl, Et 3N CH 2Cl 2, 40 !C

2

O N N

N B

N

13: R =

N

O

N

Br (43%)

R TMS Pd 2dba3, AsPh3, CuI Et 3N/PhMe 1:3, rt

R=I

N

12: R = I (55%)

N

N B

2

N

Scheme 5 Synthesis of SubPc scaffold 15 and selective TMS-‐desilylation to

N

provide 16.

N

14 (70%)

potential building block for stepwise coupling reactions of the View Article Online DOI: 10.1039/C7OB01907F two alkynes. 10 TIPS 92% Pd 2dba3, AsPh3, CuI Et 3N/PhMe 1:3, rt TMS O N N N B N N TIPS N 15 1) AgF, MeCN/PhMe 55% 2) HCl (aq) O N N N B N N TIPS N 16

TMS

Scheme 4 Synthesis of SubPc dimers 12-‐14 (mixture of diastereoisomers; peripheral substituent groups at meta positions). TMEDA = N,N,N’,N’-‐ tetramethylethylenediamine.

Peripheral functionalization of SubPc dimer 12 was next accomplished by a two-‐fold Sonogashira coupling with TMS-‐ acetylene, again employing the Pd2dba3/AsPh3 catalyst system. This afforded the extended SubPc dimer 14 in good yield. When SubPc dimer 13 with peripheral arylbromides was subjected to similar conditions, however, no reaction occurred. This coupling was also attempted using P(t-‐Bu)3 as ligand, known for enabling Sonogashira couplings to aryl 27 bromides at room temperature, but still no couplings were accomplished. Finally when elevated temperatures (40–60 °C) were tried to promote the couplings, unfortunately, decomposition of the SubPc moiety took place. The axially protected building block 10 could be reacted directly in a Sonogashira reaction with TIPS-‐acetylene to give the SubPc 15 in excellent yield (Scheme 5). Having found suitable conditions for the desilylation of SubPc derivatives, we wanted to explore whether these could be used to chemoselectively remove only the TMS group of 15, leaving the sterically hindered TIPS group unreacted. Indeed, this turned out to be possible in a spot-‐to-‐spot conversion on TLC. When only one equivalent of silver fluoride was used, 15 was selectively deprotected to give 16 with a terminal alkyne at the axial position (Scheme 5). Compound 15 thus presents a

The Cadiot-‐Chodkiewicz reaction allows synthesis of unsymmetrical 1,3-‐butadiynes from 1-‐haloalkynes and terminal acetylenes and thereby constitutes an important strategy for constructing acetylenic scaffolds. Therefore we decided to explore the possibility of preparing 1-‐haloalkyne derivatives of SubPc. After several attempts, we found two methods compatible with the SubPc moiety (Scheme 6). Relying on the hypervalent iodine source PhI(OAc)2 and a 28 16 procedure by Yan et al., we managed to convert the known alkyne 17 into the iodo-‐alkyne 18, albeit only in 20% yield (Method A). Significantly better yielding conditions (Method B; 76%) were achieved by initial formation of the silver acetylide, which was then iodinated using N-‐iodosuccinimide (NIS). Typically, 1-‐iodo-‐ and 1-‐bromoalkynes can be prepared from either the alkyne or the corresponding TMS-‐protected alkyne 29 using AgNO3 and NIS or N-‐bromosuccinimide, respectively. However, when terminal alkyne 17 was subjected to such conditions, the SubPc moiety decomposed immediately upon addition of AgNO3. Preparation of a 1-‐chloroalkyne derivative was attempted as well using trichloroisocyanuric acid 30 according to the method by Vilhelmsen et al. Unfortunately, these conditions only resulted in decomposition of the SubPc. Having prepared the iodoalkyne 18, we turned our attention to explore its potential as a coupling partner in cross-‐ coupling reactions (Scheme 7). First, 18 was coupled with TMS-‐ acetylene, providing the desired 1,3-‐butadiyne product 19 in decent yield. We then tried to carry out the coupling with the 16 more complex alkyne 20 incorporating the electron acceptor C60, and also in this case the desired asymmetrical product, 21, was obtained.

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X O

N

N B

17 (X = H)

N

Method A or B

N

(A: 20%; B: 76%)

N

CH2Cl2/CH3CN; Method B: 1) AgOTf and Et(i-‐Pr)2N in CH2Cl2, 2) NIS.

10

5

TMS O N B

N

0

N

N

20, Pd 2dba3 CuI, Et 3N, PhMe, rt

N

N B

O

O

N

N

N

N

N

O

Fig. 4 SubPc dimer with flexible bridge.

N

N

N

21

n-C8H17 O

20

Scheme 7 Pd-‐catalyzed Cadiot-‐Chodkiewicz couplings of iodoalkyne 18.

Optical properties The UV-‐Vis absorption spectra of selected compounds, 9, 12, and 2 (recorded in chloroform) are shown in Fig. 3. The compounds exhibit a longest-‐wavelength absorption maximum at 567 nm (9), 573 nm (12), and 568 nm (2) characteristic for the SubPc chromophore and close to that of the previously 16 reported dimer 22 (563 nm) . This absorption is about twice as intense for 12 and 2 as that for 9 in accord with the two SubPc units present in 12 and 2. The two SubPc units in the dimers seem to function as independent chromophores in both dimers. We shall see, however, that the nature of the bridge plays a significant role for the electrochemical properties. Introducing p-‐nitrophenyl substituents at the TEE core (compound 3) does not alter the longest-‐wavelength absorption (570 nm; see ESI). The SubPc absorptions in the 16 SubPc-‐C60 dyad 21 (previously studied) are not strongly influenced either by the presence of the C60 unit, and it exhibits a longest-‐wavelength absorption at 563 nm.

N B

N N

N

22

n-C8H17 O N B

600

chloroform.

18

N

500

Fig. 3 UV-‐Vis absorption spectra of 9 (dotted), 12 (solid), and 2 (dashed) in

TMS Pd 2dba3, CuI, AsPh3 Et 3N, PhMe, rt

20%

400

Wavelength (nm)

N

N 19

42%

300

N

The fluorescence properties depend on the other hand strongly on the bridging unit or the presence of C60. The fluorescence spectra of dimers 2 and 22 in chloroform are shown in Fig. 5, while that of the SubPc-‐C60 dyad 21, only exhibiting very low emission, is shown in the ESI. They exhibit emission maxima at about the same wavelength; 572 nm (2), 574 nm (21), and 573 nm (22), while the emission intensities vary significantly. Compound 22 exhibits the highest fluorescence quantum yield of 39%. It is well known that C60 1 quenches the SubPc fluorescence in SubPc-‐C60 conjugates, and, indeed, we determine the quantum yield of 21 to only ca. 1%. Compound 2 exhibits a quantum yield of 29%; the TEE core thus reduces the fluorescence relative to that of 22. The fluorescence lifetimes were determined to 1.8 ns and 1.9 ns for 2 and 22, respectively. 14

12

10 8 6 4

2

0

Normalized Emission (a.u.)

N

ε (104 M-1cm-1)


18 (X = I)

Scheme 6 Synthesis of iodoalkyne 18. Method A: KI, CuI, PhI(OAc)2, Et3N in

DOI: 10.1039/C7OB01907F

300

400

500

600

700

Wavelength (nm) Fig. 5 UV-‐Vis absorption spectra (full line) and normalized emission spectra (dashed line) of compound 2 (black), 22 (red) and 21 (blue) in chloroform. The emission spectrum of 21 is not shown as its fluorescence is very weak (but included in the ESI).


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Redox properties and HOMO-‐LUMO calculations The redox properties of selected SubPc derivatives were investigated by cyclic voltammetry (in CH2Cl2 with 0.1 M Bu4NPF6 as supporting electrolyte). The cyclic voltammograms of 17, 22, 2 and 3 are shown in Figures 6 and 7. The formal o potentials, E ’, are reported for reversible electron transfers with reverse current being observed during the back scan. When follow-‐up reactions are so fast that reverse currents are not clearly observed, and the potentials for that reason do not necessarily have a thermodynamic significance, we report in the following instead the peak potential, Ep. All potentials are + given in V vs Fc/Fc . The reduction of 17 takes place in two steps. First, a reversible one-‐electron transfer to the radical anion is o observed at E ’ = -‐1.60 V and this is followed by further o reduction at E ’ = -‐2.11 V to a reactive dianion for which reverse current is barely seen during the backward scan. Instead one major oxidation peak with Ep = -‐0.94 V and three minor oxidation peaks corresponding to the oxidation of intermediate anions formed by bond cleavage and/or protonation by residual water of the dianion are observed. One-‐electron oxidation of 17 to a reactive radical cation is o observed at E ’ = 0.54 V and a small peak corresponding to the reduction of one or more cations formed by the follow-‐up reaction of the radical cation is observed at Ep = -‐0.02 V during the backward scan. The concentration-‐normalized peak currents, ip/c, observed for the first reduction and oxidation –1 peaks were found to be 19.7 and 20.8 μA mM , respectively, –1 and in the following the average, ~20 μA mM , will serve as the expectation value for a simple one-‐electron process for related compounds with comparable diffusion coefficients, D. The behavior of 22 is similar. The potentials for the two o o reductions are observed at E ’ = -‐1.57 V and E ’ = -‐2.08 V, respectively, and the potential for oxidation at Ep = 0.54 V. Product peaks of a similar origin as those resulting from 17 are observed at Ep = -‐0.93 V and Ep = -‐0.12 V. By comparison of the results obtained for 17 and 22 it is seen that the two compounds are reduced and oxidized at nearly the same potentials. The small difference, ~30 mV, in favor of 22 for the reversible reduction agrees well with the statistical factor, 31 (RT/F)ln4 = 35.6 mV at T=298 K, caused by the difference in •-‐ 2-‐ symmetry between 22 (unsymmetrical) and 22 and 22 (symmetrical). Thus, there seems to be only negligible electronic interaction between the two halves of 22 as also expected considering that the two SubPc units in 22 are linked by the partly saturated -‐O-‐CH2CH2-‐C≡C-‐C≡C-‐CH2CH2-‐O-‐ bridge. This is further substantiated by the results of a series of DFT calculations (B3LYP/cc-‐pVDZ) demonstrating that 22 is indeed a degenerate system with two independent SubPc units as illustrated by the HOMO-‐LUMO pictures in Fig. 8.

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Fig. 6 Cyclic voltammograms of 17 and 22 recorded in CH2Cl2 (0.1 M Bu4NPF6) at a -‐1 glassy carbon electrode (d = 3 mm) at a scan rate of 0.1 V s .

Fig. 7 Cyclic voltammograms of 2 and 3 recorded in CH2Cl2 (0.1 M Bu4NPF6) at a glassy -‐1 carbon electrode (d = 3 mm) at a scan rate of 0.1 V s .

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Fig. 8 Degenerate HOMOs (bottom) and LUMOs (top) of 22.

The values of ip/c for the first reduction and oxidation –1 peaks for 22 are 29.8 and 26.2 μA mM , respectively, values that are larger than those observed for the monomer, 17, but still less than twice those for 17. This reflects that the diffusion coefficients for 22, and its ions, are significantly smaller than those for 17, and its ions, owing to the much larger structure of 22. The reductions of 2 and 3 proceed similarly to those for 17 and 22, but with one notable exception. For 2 a reversible o two-‐electron process is observed at E ’ = -‐1.57 V, whereas for 3 the reduction appears as two closely spaced one-‐electron o o transfers at E ’ = -‐1.42 and E ’ = -‐1.54 V. It should be noticed o also that the reduction peak for 2 at E ’ = -‐1.57 V is unusually sharp indicating that the two-‐electron process may include potential inversion, that is, the reduction proceeds as an eCe process with the chemical step, C, being an internal reorganization of the structure resulting in a radical anion that is easier to reduce than the substrate, 2. It is tempting to suggest that the reorganization is caused by the steric requirements exerted by the two TIPS groups that result in a calculated B-‐B distance of only 6.42 Å (only a little larger than the one found by crystallography; 6.16 Å) as shown in Fig. 9. Also, it is clearly seen that the C-‐C≡C-‐B moiety is non-‐linear. For comparison the B-‐B distance of the relaxed structure 3, 7.07 Å, is significantly larger and in addition the C-‐C≡C-‐B moiety is perfectly linear. Potential inversions caused by the release of steric repulsion have been reported in many cases 32 including, e.g., the reduction of aromatic dinitro compounds 33 and the oxidation of an extended tetrathiafulvalene . This aspect of the reduction of 2 is now under investigation. Further reduction of 2 takes place at Ep = -‐2.15 V. According to -‐1 the peak height, ~20 μA mM , this appears to be a one-‐ electron process generating a reactive radical trianion with, as before for 17 and 22, an oxidation peak resulting from an •3-‐ anion produced by reaction of 2 being observed at Ep = -‐0.93 V.

Fig. 9 Structures of 2 (top) and 3 (bottom) resulting from B3LYP/cc-‐pVDZ calculations.

The reduction of 3 is noticeably different in the sense that the reduction proceeds as two closely spaced one electron – processes; the value of ip/c for the combined peak is 31.7 mM 1 , which is only slightly smaller than that for 2. Here it is of interest to compare the HOMOs and LUMOs for the two compounds (Fig. 10). Compound 2, that owing to the compression of the two SubPc units caused by the TIPS groups is not completely symmetrical, has a set of nearly degenerate HOMOs and a LUMO that encompass both SubPc units and the TEE spacer. Compound 3, that is perfectly symmetrical, has a set of degenerate HOMOs, but in contrast to 2 a LUMO that is almost entirely centered on the two electron-‐withdrawing p-‐ nitrophenyl groups and the acetylenic spacer and only marginally on the SubPc units. This may explain why 3 is reduced ~150 mV more easily than 2. The oxidations of 2 and 3 are complicated processes, indicating interactions between the two SubPc units, and appear as double peaks of low intensity, for 2 at Ep = 0.54 V and 0.65 V and for 3 at Ep = 0.58 V and 0.66 V. The value of ip/c for 3, for example, is as low as 18 –1 μA mM . This cannot possibly be related to diffusion coefficient differences and the origin is presently unknown. However, further research into this behavior was deemed to be beyond the scope of this study.


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when the TEE contains geminally substituted p-‐nitrophenyl View Article Online DOI: 10.1039/C7OB01907F groups. With the more flexible 1,8-‐di( λ1-‐oxidanyl)octa-‐3,5-‐ diyne linker the two SubPc units instead behaved as independent redox centers, both in regard to oxidations and reductions. Fluorescence studies revealed that the TEE linker reduces the SubPc fluorescence, but not to the same degree as a C60 unit that strongly quenches it.


Experimental Section General procedures

Fig. 10. Frontier orbital pictures of a) 2 (top: LUMO; bottom: nearly degenerate HOMOs); b) 3 (top: LUMO; bottom: degenerate HOMOs).

Conclusions To summarize, we have successfully synthesized several new acetylenic scaffolds containing SubPcs by employing reaction conditions compatible with this sensitive chromophore. Protodesilylation of silyl-‐protected alkynes turned out particularly challenging in the presence of the SubPc unit, but we found that desilylation of both TMS-‐ and TIPS-‐protected scaffolds could be accomplished using AgF followed by aqueous HCl. Moreover, the more labile TMS group could be removed selectively in the presence of the TIPS group. This result is particularly important for the ability to perform stepwise acetylenic scaffolding along for example the axial and peripheral positions. Protocols for iodination of alkynes in the presence of the SubPc unit were also developed. Thus, we managed to achieve this conversion by the action of either AgOTf/Hünig’s base/NIS or PhI(OAc)2/KI/CuI/Et3N, the former method being highest yielding. The resulting SubPc – iodoalkyne was then subjected to cross-‐couplings to yield unsymmetrical 1,3-‐butadiyne SubPc derivatives. While no interactions between the two SubPc units in the dimeric structures were evidenced by UV-‐Vis absorption spectroscopy, electrochemical studies revealed that a short TEE linker has a strong influence on the redox properties. The SubPc oxidations occur stepwise, and so do the reductions

All reagents and solvents were obtained from commercial suppliers and used as received unless otherwise stated. The following compounds were prepared according to reported 2,16 17 literature procedures: SubPc-‐Cl, 1, 1-‐(bromoethynyl)-‐4-‐ 22 23 nitrobenzene, 4-‐(iodoethynyl)benzonitrile, 1,2-‐ 34 16 16 dioctyloxybenzene, 20, and 17. Anhydrous THF was obtained by distillation from a Na/benzophenone couple. Anhydrous pyridine was obtained from storage over KOH. Purification by column chromatography was carried out on silica gel (SiO2, 60 Å, 40−63 μm). Thin-‐layer chromatography (TLC) was carried out using commercially available aluminum sheets precoated with silica gel with fluorescence indicator 1 13 and visualized under UV light at 254 or 360 nm. H and C NMR spectra were recorded on a 500 MHz instrument at 500 11 MHz and 126 MHz, respectively. B NMR spectra were recorded on a 500 MHz instrument equipped with a broad-‐ band probe. Chemical shift values are quoted in ppm and 1 13 coupling constants (J) in Hz. H and C NMR spectra are referenced against the residual solvent peak (CDCl3 δH = 7.26 ppm, δC = 77.16 ppm; C6D6 δH = 7.16 ppm, δC = 128.06 ppm). 11 B NMR spectra are referenced against an external standard of BF3 diethyl etherate (BF3·∙(OC2H5)2; δB = 0 ppm). HRMS MALDI spectra were recorded on an ESP-‐MALDI-‐FT-‐ICR instrument equipped with a 7T magnet (prior to the experiments, the instrument was calibrated using NaTFA cluster ions). Crystallographic analysis: Bruker D8-‐venture diffractometer using Kα (M0) radiation. Data reduced with 35 Apex and solved with OLEX2. Cyclic voltammetry was carried out at room temperature in CH2Cl2 containing Bu4NPF6 (0.1 M) as the supporting electrolyte using an Autolab PGSTAT12 instrument driven by the Nova 1.11 software. The working electrode was a circular glassy carbon disk (d = 3 mm), the counter electrode was a platinum wire and the reference electrode was a silver wire immersed in the solvent-‐supporting electrolyte mixture and physically separated from the solution containing the substrate by a ceramic frit. The potential of the reference electrode was determined vs the + ferrocene/ferrocenium (Fc/Fc ) redox system in separate -‐1 experiments. The voltage sweep rate was 0.1 Vs . iR-‐ Compensation was used in all experiments. Solutions were purged with argon saturated with CH2Cl2 for at least ten min before the measurements were made after which a stream of argon was maintained over the solutions. UV−Vis absorption measurements were performed in a 1 cm path-‐length cuvette, and the neat solvent was used as baseline; sh = shoulder. All

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fluorescence quantum yields were measured using a Lambda 1050 (PerkinElmer) instrument for absorption measurements and a Fluotime 300 (PicoQuant) instrument for fluorescence measurements. For all quantum yield determinations, cresyl violet perchlorate in absolute ethanol was used as reference 36 dye. All melting points are uncorrected. The computations were carried out at the DFT B3LYP/cc-‐pVDZ level of theory using either a local HP ML350 workstation or computers hosted by the High Performance Computing Center at the University of Copenhagen. The Gaussian G09 suite of programs 37 (Revs. B.01 or E.01) were used throughout. The initial structures were generated by GaussView 5.0 except for 2 for which the X-‐ray structure was used as input in order to have the same orientation and conformation of the TIPS groups. True minima resulted in all cases as evidenced by the absence of negative frequencies. 1,2-‐Diiodo-‐4,5-‐bis(octyloxy)benzene. 1,2-‐Dioctyloxybenzene (22.3 g, 63.7 mmol), iodine (15.2 g, 59.9 mmol) and periodic acid (5.95 g, 26.1 mmol) were dissolved in a mixture of AcOH (250 mL), H2O (50 mL) and 95% H2SO4 (8 mL), and the reaction mixture was heated to 80 °C for 18 h, whereupon the color of the reaction mixture changed from purple to dark red. After cooling to rt the reaction mixture was quenched with a sat. aq. solution of Na2S2O3 (200 mL) giving a white slurry with a brown precipitate. The brown solids were filtered off, and the filter was washed with CH2Cl2 (500 mL). The organic phase was separated and the aq. phase washed with CH2Cl2 (3 x 100 mL). The combined organics were washed with water (500 mL) and brine (500 mL), dried with MgSO4, filtered, and the solvents were removed in vacuo. Purification by flash column chromatography (SiO2, 10% CH2Cl2/heptanes) gave the title compound (29.4 g, 79%) as a white solid. Rf = 0.40 (10% 1 CH2Cl2/heptanes). M.p. 47-‐48 °C. H NMR (500 MHz, CDCl3) δ 7.25 (s, 2H), 3.92 (t, J = 6.6 Hz, 4H), 1.82-‐1.74 (m, 4H), 1.47-‐ 13 1.41 (m, 4H), 1.38-‐1.23 (m, 16H), 0.88 (m, 6H) ppm. C NMR (126 MHz, CDCl3) δ 149.92, 123.94, 96.11, 69.63, 31.94, 29.43, 29.38, 29.19, 26.06, 22.81, 14.24 ppm. HRMS (MALDI+): m/z • + • + [M ] calcd for [C22H36I2O2 ] 586.0799, found 586.0754. Compound 2. SubPc-‐Cl (775 mg, 1.80 mmol, 2.3 equiv.) and 1 (455 mg, 0.78 mmol) were suspended in o-‐dichlorobenzene (4 mL) and stirred at rt for 1.5 h, after which AlCl3 (379 mg, 2.84 mmol, 3.6 equiv.) was added, and the reaction mixture was stirred for an additional 2.5 h. The reaction mixture was quenched with pyridine (0.5 mL) and filtered through a plug of neutral Brockman I Al2O3 (0–100% EtOAc/toluene), and the filtrate was concentrated in vacuo. Purification by flash column chromatography (SiO2, 5–50% EtOAc/toluene) gave compound 2 as pink, metallic crystals (600 mg, 63%). Rf = 0.59 (30% ◦ EtOAc/toluene). Mp. >230 C. Crystals suitable for X-‐ray 1 crystallography were grown from CH2Cl2/MeOH 1:2. H NMR (500 MHz, CDCl3) δ 8.61 (dd, J = 6.0, 3.0 Hz, 12H), 7.56 (dd, J = 13 6.0, 3.0 Hz, 12H), 0.82 (s, 42H) ppm. C NMR (126 MHz, CDCl3) δ 150.54, 130.73, 129.44, 122.06, 117.63, 115.43, 103.12, 101.27, 18.64, 11.03 ppm (two signals missing due to overlap). 11 B NMR (160 MHz, CDCl3) δ -‐21.0 ppm. HRMS (MALDI+): m/z

+

+

[M+H] calcd for [C76H67B2N12Si2] 1225.5331, View Articlefound Online 4 -‐1 -‐1 1225.5403. UV-‐vis (CHCl3): λ [nm] (ε [10 DOI: M 10.1039/C7OB01907F cm ]) 568 (14.6), 520sh, 341sh, 307 (11.5), 270 (7.3). Compound 3. Compound 2 (76 mg, 0.062 mmol) was dissolved in CH2Cl2 (5 mL) using sonication for 15 min, and the suspension was flushed with Ar. After addition of AcOH (0.5 mL, 0.7 M in CH2Cl2), AgF (80 mg, 0.63 mmol, 10 equiv.) and MeCN (2 mL), the mixture was stirred at rt for 14 h under an Ar atm. The solution was washed with 0.05 M HCl (200 mL) and subjected to numerous extractions with CH2Cl2 (a total volume of 500 mL), dried over MgSO4, and concentrated to near dryness under reduced pressure. Toluene (20 mL) was added, and residual CH2Cl2 was removed in vacuo. To the solution were added 4-‐iodonitrobenzene (158 mg, 0.70 mmol, 11 equiv.), CuI (6.1 mg, 0.032 mmol, 52 mol%), Pd2dba3 (18 mg, 0.020 mmol, 32 mol%) and AsPh3 (47 mg, 0.15 mmol, 2.7 equiv.). The mixture was flushed with Ar for 30 min, after which Et3N (0.5 mL) was added and the resulting reaction mixture was stirred vigorously at room temperature for 22 h. The reaction mixture was filtered through a plug of silica (1. CH2Cl2 (500 mL), 2. EtOAc (300 mL)), and the purple filtrate was collected and purified by flash column chromatography (SiO2, 10–20% EtOAc/toluene). Concentration under reduced pressure resulted in compound 3 as a purple solid (22 mg, ◦ 1 33%). Rf = 0.44 (20% EtOAc/toluene). M.p. >230 C. H NMR (500 MHz, CDCl3) δ 8.66 (dd, J = 6.0, 3.0 Hz, 12H), 7.92 (d, J = 9.1 Hz, 4H), 7.73 (dd, J = 6.0, 3.0 Hz, 12H), 7.11 (d, J = 9.1 Hz, 13 4H) ppm. C NMR (126 MHz, CDCl3) δ 150.31, 147.17, 132.20, 130.50, 129.69, 128.49, 123.42, 122.01, 119.36, 115.76, 95.78, 11 90.03 ppm (two signals missing due to overlap). B NMR (160 + MHz, CDCl3) δ -‐21.0 ppm. HRMS (MALDI+): m/z [M+H] calcd + for [C70H32B2N14O4] 1155.2990, found 1155.2959. Compound 4. Compound 2 (39.9 mg, 0.032 mmol) was dissolved in CH2Cl2 (5 mL) using sonication for 35 min after which AcOH (0.5 mL, 0.7 M in CH2Cl2), AgF (44 mg, 0.35 mmol, 11 equiv.) and MeCN (2 mL) were added, and the reaction mixture was stirred for 13 h at rt. The solution was washed with 0.1 M HCl (100 mL) and subjected to numerous extractions with CH2Cl2 (a total volume of 300 mL), dried over MgSO4 and concentrated to near dryness under reduced pressure. Toluene (5 mL) was added and residual CH2Cl2 removed in vacuo. The solution was added dropwise to an Ar-‐ purged solution of 1,2-‐diiodo-‐4,5-‐bis(octyloxy)benzene (142.4, 0.24 mmol, 7.6 equiv.), Pd2dba3 (9.1 mg, 0.009 mmol, 30 mol%), CuI (5.2 mg, 0.027 mmol, 90 mol%) and AsPh3 (17.6 mg, 0.057 mmol, 180 mol%) in toluene (1 mL) and Et3N (0.7 mL) during the course of 20 min, and the mixture was stirred at rt for 2 h. The reaction mixture was washed with water (100 mL), extracted with CH2Cl2, dried over MgSO4, and concentrated in vacuo. Purification by flash column chromatography (SiO2, 10% EtOAc/toluene) yielded the title compound 4 as a dark pink solid (17 mg, 29%). Rf = 0.36 (20% CH2Cl2/toluene). M.p. >230 ◦ 1 C. H NMR (500 MHz, CDCl3) δ 8.50 (dd, J = 5.9, 3.1 Hz, 12H), 7.44 (dd, J = 5.9, 3.1 Hz, 12H), 7.11 (s, 2H), 6.80 (s, 2H), 4.15 (t, J = 6.6 Hz, 4H), 4.02 (t, J = 6.6 Hz, 4H), 1.98-‐1.10 (m, 48H), 1.01-‐


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0.72 (m, 12H). C NMR (126 MHz, CDCl3) δ 150.37, 148.93, 130.57, 129.24, 122.81, 121.93, 121.11, 117.86, 117.33, 114.49, 100.19, 91.08, 87.86, 69.71, 69.45, 32.00, 29.86, 29.64, 29.54, 29.51, 29.46, 29.32, 26.34, 26.21, 22.84, 14.27 (six + signals missing due to overlap). HRMS (MALDI+): m/z [M+H] + calcd for [C102H99B2I2N12O4] 1830.6059, found 1830.6026. Compound 5. Compound 2 (69.6 mg, 0.053 mmol) was dissolved in CH2Cl2 (5 mL) using sonication for 10 min after which AcOH (0.5 mL, 0.7 M in CH2Cl2), AgF (71.1 mg, 0.56 mmol, 11 equiv.) and MeCN (2 mL) were added under stirring, and the mixture was stirred for 15 h at rt. The solution was washed with 0.05 M HCl (200 mL) and subjected to numerous extractions with CH2Cl2 (a total volume of 500 mL), dried over MgSO4, and concentrated to near dryness under reduced pressure. Toluene (3.5 mL) was added and residual CH2Cl2 was removed in vacuo. The solution was purged with Ar after which 1-‐ethynyl-‐4-‐nitrobenzene (36.5 mg, 0.16 mmol, 3 equiv.), Pd2dba3 (10 mg, 0.011 mmol, 21 mol%) and CuI (8.6 mg, 0.045 mmol, 85 mol%) were added, and the solution was stirred for 7 h at rt under an Ar atm. The reaction mixture was washed with water (200 mL), extracted with CH2Cl2 (500 mL), dried over MgSO4 and concentrated under reduced pressure. Purification by repeated flash column chromatography (SiO2, 1. column: 10–20% EtOAc/toluene, 2. column: 20–100% EtOAc/heptane) gave compound 5 as a pink solid (11.9 mg, 1 19%). Rf = 0.31 (20% EtOAc/toluene). M.p. >230 °C. H NMR (500 MHz, CDCl3) δ 8.69 (dd, J = 5.9, 3.1 Hz, 12H), 8.33 (d, J = 13 9.0 Hz, 4H), 7.80-‐7.72 (m, 16H) ppm. C NMR (126 MHz, CDCl3) δ 150.42, 133.74, 130.84, 129.74, 123.82, 122.16 ppm (ten signals missing, 5 was only slightly soluble in the NMR + solvent). HRMS (MALDI+): m/z [M+H] calcd for + [C74H33B2N14O4] 1203.2990, found 1203.2935. Compound 6. Compound 2 (70 mg, 0.057 mmol) was dissolved in CH2Cl2 (5 mL) using sonication for 20 min after which AcOH (0.5 mL, 0.7 M in CH2Cl2) and AgF (83 mg, 0.65 mmol, 11.4 equiv.) were added under stirring. After 5 min, MeCN (2 mL) was added, and the reaction mixture was stirred for 13 h at rt. The solution was washed with 0.01 M HCl (100 mL) and subjected to numerous extractions with CH2Cl2 (a total volume of 300 mL), dried over MgSO4, and concentrated to near dryness under reduced pressure. Toluene (5 mL) was added, and residual CH2Cl2 was removed in vacuo. 4-‐ (iodoethynyl)benzonitrile (50 mg, 0.20 mmol, 3.5 equiv.), Pd2dba3 (13 mg, 0.014 mmol, 25 mol%), CuI (6.0 mg, 0.035 mmol, 60 mol%) and AsPh3 (38 mg, 0.13 mmol, 220 mol%) were added, and the solution was degassed with Ar for 30 min before addition of Et3N (0.5 mL) under stirring. The reaction mixture was vigorously stirred at rt for 3 h, after which the crude mixture was washed with water (100 mL), extracted with CH2Cl2 (500 mL), dried over MgSO4 and concentrated under reduced pressure. The resulting dark solid was purified by repeated flash column chromatography (SiO2, 1. column: 10–20% EtOAc/toluene, 2. column: 50% EtOAc/heptanes) yielding the title compound as purple crystals (11 mg, 17%). Rf ◦ 1 = 0.26 (50% EtOAc/heptane). M.p. >230 C. H NMR (500 MHz,

CDCl3) δ 8.53 (dd, J = 5.9, 3.1 Hz, 12H), 7.68 (d, J = 8.5 Hz, 4H), View Article Online 13 10.1039/C7OB01907F 7.64 (d, J = 8.5 Hz, 4H), 7.57 (dd, J = 5.9, DOI: 3.1 H z, 12H). C NMR (126 MHz, CDCl3) δ 150.39, 133.43, 132.23, 130.80, 129.67, 126.83, 123.30, 122.11, 118.48, 115.11, 112.82, 83.89, 82.07, 78.42 (three signals missing due to overlap). HRMS (MALDI+): + + m/z [M+H] calcd for [C76H33B2N14] 1163.3121, found 1163.3207. Compound 9 (racemic mixture). To a mixture of 4-‐ iodophthalonitrile (1.52 g, 6.00 mmol) and phthalonitrile (3.84 g, 30.0 mmol, 5 equiv.) in dry o-‐dichlorobenzene (200 mL) in a three-‐necked flask under a nitrogen atmosphere was slowly added BCl3 (100 mL, 1 M in hexane, 100 mmol). A color change from white-‐yellow to dark red was observed. The suspension was heated to reflux temperature (64 °C) for 0.5 h, whereafter the hexane was removed by distillation. The reaction mixture was heated to reflux temperature again (180 °C) for 2 h, after which time no more of the starting materials could be detected by TLC. The reaction mixture was transferred to a one-‐necked flask and concentrated to dryness under reduced pressure to yield a dark purple solid (8.21 g). A fraction of this solid (3.99 g) was washed with methanol (200 mL) using a Soxhlet extraction apparatus for 22 h, and the remains were dried in vacuo to yield a purple solid mixture (1.72 g). The mixture (1.62 g) and AgOTf (527 mg, 2.05 mmol) were transferred to a dry 250 mL round-‐bottomed flask fitted with an argon balloon. Dry toluene (70 mL) was added and the mixture was stirred for 1 h at rt. Additional AgOTf (264 mg, 1.03 mmol) was added as residual starting material could be detected by TLC. Stirring was continued for 1 h, after which time all starting material was consumed judged from TLC. After an additional 1 h of stirring, NEt(i-‐Pr)2 (0.85 mL, 4.9 mmol) and 3-‐butyn-‐1-‐ol (1.7 mL, 23 mmol) were added, and the reaction mixture was stirred for 20 h at room temperature. The reaction mixture was passed through a short plug of silica, eluting with EtOAc (300 mL), and the filtrate was concentrated to dryness under reduced pressure to yield a dark purple oil (1.96 g) with a golden shiny surface. The oil was dissolved in toluene (10 mL) and subjected to flash column chromatography (gradient elution: 10–50% EtOAc/toluene) to obtain 9 (254 mg, 16%; based on the fractions carried on in the synthesis) as a thin purple film with a golden shiny surface. Rf = 1 0.5 (10% EtOAc/toluene). M.p. >230 °C. H NMR (CDCl3, 500 MHz) δ 9.21 (d, J = 1.0 Hz, 1H), 8.80–8.86 (m, 4H), 8.57 (d, J = 8.4 Hz, 1H), 8.16 (dd, J = 8.4, 1.0 Hz, 1H), 7.89-‐7.94 (m, 4H), 1.59 (t, J = 7.7 Hz, 2H), 1.56 (t, J = 2.7 Hz, 1H), 1.36 (td, J = 7.7, 13 2.7 Hz, 2H) ppm. C NMR (CDCl3, 126 MHz) δ 152.62, 152.42, 151.94, 151.75, 150.62, 149.48, 138.26, 132.27, 131.33, 131.29, 131.18, 131.12, 130.20, 130.10, 130.08, 129.80, 123.46, 122.39, 122.38, 122.31, 122.27, 95.53, 80.98, 68.94, 11 57.92, 20.97 ppm (two signals missing due to overlap). B NMR (CDCl3, 160 MHz) δ -‐15.1 ppm. HRMS (MALDI+): m/z • + • + [M ] calcd for [C28H16BIN6O ] 590.0518, found 590.0525. UV-‐ 4 -‐1 -‐1 vis (CHCl3): λ [nm] (ε [10 M cm ]) 567 (8.9), 530sh, 514sh, 307 (4.4), 270 (4.2).

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Compound 10. A solution of BCl3 in hexane (1.0 M, 120 mL, 120 mmol) was added to a stirring mixture of 4-‐ iodophthalonitrile (2.16 g, 8.50 mmol) and phthalonitrile (5.45 g, 42.5 mmol, 5 equiv.) in dry o-‐dichlorobenzene (150 mL), and o the resulting suspension was heated to reflux (ca. 68 C) for 30 min. Hexane was removed by distillation and the reaction o mixture was heated to reflux once more (ca. 180 C) for 2 h. Residual BCl3 was removed by a stream of N2 and the reaction mixture concentrated in vacuo. The crude residue was transferred to a thimble and washed with MeOH using a Soxhlet extraction apparatus for 48 h and dried in vacuo to yield a purple solid residue (984 mg). The residue was dissolved in dry toluene (50 mL), and AgOTf (584 mg, 2.27 mmol) was added before the reaction mixture was stirred at rt for 1 h under argon. Trimethylsilyl-‐3-‐butyn-‐1-‐ol (1.1 mL, 0.97 g, 6.8 mmol, 3.0 equiv.) and NEt(i-‐Pr)2 (0.50 mL, 0.37 g, 2.9 mmol, 1.3 equiv.) were added, and the reaction mixture was stirred at rt for 48 h after which it was passed through a short plug of SiO2 eluting with EtOAc/toluene (1:1). The filtrate was concentrated to dryness and subjected to flash column chromatography (SiO2, 5% EtOAc/toluene) followed by size-‐ exclusion chromatography (Biobeads SX-‐3, CH2Cl2) to yield a purple residue. The residue was dried by a stream for N2 for 20 h at 75 °C and subjected to flash column chromatography (SiO2, 5% EtOAc/toluene) to yield the title compound (161 mg, 3% over two steps) as a purple solid. M.p. >230 °C. Rf = 0.45 1 (5% EtOAc/toluene). H NMR (CDCl3, 500 MHz) δ 9.21 (d, J = 1.0 Hz, 1H), 8.86-‐8.83 (m, 4H), 8.56 (d, J = 8.5 Hz, 1H), 8.16 (dd, J = 1.5, 8.5 Hz, 1H), 7.93-‐7.89 (m, 4H), 1.56 (t, J = 7.4 Hz, 13 2H) 1.40 (t, J = 7.4 Hz, 1H) ppm. C NMR (CDCl3, 126 MHz) δ 152.65, 152.45, 151.96, 151.78, 150.64, 149.50, 138.25, 133.72, 133.23, 132.25, 131.31, 131.17, 131.10, 130.20, 130.10, 130.08, 129.79, 123.47, 122.55, 122.40, 122.39, 122.32, 122.28, 103.11, 95.52, 85.36, 57.87, 22.28, 0.11 ppm. + + HRMS (MALDI+): m/z [M+H] calcd for [C31H25BIN6Si] 663.0991, found 663.0993.

Compound 11 (racemic mixture). To a stirring solution of View Article Online DOI: 10.1039/C7OB01907F phthalonitrile (3.16 g, 24.7 mmol) and 8 (1.40 g, 4.93 mmol) in dry 1,2-‐dichlorobenzene (200 mL) was added BCl3 (100 mL, 100 mmol, 1 M in hexane), and the reaction mixture was heated to reflux point (ca. 64 °C) for 30 min. The hexane was distilled off, and the reaction mixture was once more heated to reflux (180 °C). After 1.5 h, the reaction mixture was allowed to cool to rt and concentrated under reduced pressure. The remaining brown solids were transferred to a thimble and washed continuously with MeOH using a Soxhlet extraction apparatus for 30 h. The Soxhlet retentate was washed with diethylether and dried in vacuo to give a brown powder (1.4 g) consisting of different subphthalocyanine chlorides. To an Ar-‐purged round-‐bottomed flask charged with this mixture and AgOTf (767 mg, 2.99 mmol) was added toluene (70 mL), and the reaction mixture was stirred for 2 h. Hünig’s base (0.53 mL, 3.0 mmol) and 3-‐butyn-‐1-‐ol (1.1 mL, 14 mmol) were added, and a color change from purple to dark red immediately took place. After 20 h, the reaction mixture was filtered through a plug of SiO2 (EtOAc) and concentrated in vacuo. Purification by flash column chromatography (SiO2, 1. column: 5% EtOAc/toluene, 2. column: 25% EtOAc/heptane) afforded the title compound (105 mg, 3%) as a purple solid. Rf 1 = 0.38 (30% EtOAc/heptane). M.p. 169-‐170 °C. H NMR (500 MHz, CDCl3) δ 9.04 (dd, J = 1.6, 0.7 Hz, 1H), 8.89 (dd, J = 8.2, 0.7 Hz, 1H), 8.87-‐8.82 (m, 4H), 8.09 (dd, J = 8.2, 1.6 Hz, 1H), 7.94-‐7.86 (m, 4H), 7.73 (d, J = 8.6 Hz, 2H), 7.68 (d, J = 8.6 Hz, 2H), 1.62 (t, J = 7.1 Hz, 2H), 1.57 (t, J = 2.7 Hz, 1H), 1.38 (td, J = 13 7.1, 2.7 Hz, 2H) ppm. C NMR (126 MHz, CDCl3) δ 152.01, 151.91, 151.87, 151.63, 151.43, 151.23, 141.81, 139.62, 132.38, 131.84, 131.23, 131.19, 131.18, 131.14, 130.02, 130.00, 130.00, 129.96, 129.42, 128.71, 122.72, 122.67, 122.33, 122.29, 122.24, 120.38, 81.02, 68.94, 57.94, 21.00 + ppm (two signals missing). HRMS (MALDI+): m/z [M+H] calcd + for [C34H20BBrN6O] 619.1050, found 619.1048. Compound 12 (mixture of diastereoisomers). CuCl (10 mg, Compound 8. To a mixture of degassed toluene (80 mL) and 0.10 mmol, 3 equiv.) and TMEDA (0.05 mL, 0.3 mmol, 9 equiv.) aqueous 0.32 M Na2CO3 (30 mL) were added 4-‐ were added to CH2Cl2 (4 mL) in an open flask. Compound 9 (20 bromophenylboronic acid (2.4 g, 11.8 mmol), 4-‐ mg, 0.03 mmol) was added and the reaction mixture was iodophthalonitrile (2.3 g, 9.1 mmol) and Pd(PPh3)4 (523 mg, stirred vigorously for 3 h at 40 °C. Additional CH2Cl2 was added 0.45 mmol), and the reaction mixture was heated to 80 °C to the flask during the course of the reaction due to under Ar. The reaction mixture was allowed to cool to rt and evaporation. The reaction mixture was passed through a small concentrated under reduced pressure. The remaining solid was plug of SiO2 eluting with EtOAc. The filtrate was concentrated dissolved in EtOAc (150 mL), washed with aqueous 2 M Na2CO3 in vacuo and subjected to flash column chromatography (SiO2, (3 x 90 mL), dried over MgSO4, filtered and concentrated under 20% EtOAc/toluene) to yield 12 as a purple solid (11 mg, 55%). 1 reduced pressure. Purification by flash column Rf = 0.3 (15% EtOAc/toluene). M.p. >230 °C. H NMR (CDCl3, chromatography (SiO2, 1% EtOAc/toluene) afforded the title 500 MHz) δ 9.20 (d, J = 1.0 Hz, 2H), 8.80-‐8.85 (m, 8H), 8.55 (d, J compound (1.14 g, 45%) as a white powder. Rf = 0.36 (1% = 8.4 Hz, 2H), 8.13 (dd, J = 8.4, 1.0 Hz, 2H), 7.86-‐7.90 (m, 8H), 13 1 EtOAc/toluene). M.p. 200-‐201 °C. H NMR (500 MHz, CDCl3) δ 1.51 (t, J = 7.0 Hz, 4H), 1.35 (t, J = 7.0 Hz, 4H) ppm. C NMR 7.98 (dd, J = 1.6, 0.8 Hz, 1H), 7.90 (dd, J = 8.2, 1.6 Hz, 1H), 7.88 (CDCl3, 126 MHz) δ 152.58, 152.38, 151.91, 151.73, 150.61, (dd, J = 8.2, 0.8 Hz, 1H), 7.67 (d, J = 8.8 Hz, 2H), 7.45 (d, J = 8.8 149.47, 138.21, 132.27, 131.32, 131.29, 131.17, 131.11, 13 Hz, 2H) ppm. C NMR (126 MHz, CDCl3) δ 145.27, 135.82, 130.16, 130.07, 130.04, 129.80, 123.50, 122.42, 122.41, 134.09, 132.77, 131.75, 131.20, 128.70, 124.57, 116.73, 122.34, 122.31, 95.51, 73.69, 65.57, 57.71, 21.76 ppm (two + 115.30, 115.22, 114.41 ppm. HRMS (ESI+): m/z [M+H] calcd signals missing due to overlap – assuming that the + diastereoisomers have overlapping signals). HRMS (MALDI+): for [C14H8BrN2] 282.9865, found 282.9868. + + m/z [M+Na] calcd for [C56H30B2I2N12O2Na] 1201.0782, found


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1201.0721. UV-‐vis (CHCl3): λ [nm] (ε [10 M cm ]) 573 (16.1), 535sh, 517sh, 307 (8.2), 272 (9.9). Compound 13 (mixture of diastereoisomers). Et3N (0.5 mL) was added to a suspension of 11 (75 mg, 0.12 mmol) and CuCl (14 mg, 0.14 mmol, 1.2 equiv.) in CH2Cl2 (3 mL), and the reaction mixture was stirred vigorously in an open vessel. Additional CuCl (51 mg, 0.51 mmol, 4.3 equiv.) was added portion-‐wise during the course of the reaction. After 7 h, the reaction mixture was diluted with EtOAc (2 mL) and filtered through a plug of SiO2 (EtOAc/CH2Cl2 1:1). The filtrate was concentrated in vacuo, redissolved in a small volume of CH2Cl2 and subjected to flash column chromatography (SiO2, 5–10% EtOAc/CH2Cl2) to afford the title compound (32 mg, 43%) as a golden-‐brown solid. Rf = 0.38 (5% EtOAc/CH2Cl2). M.p. >230 °C. 1 H NMR (500 MHz, CDCl3) δ 9.05-‐8.99 (m, 2H), 8.89-‐8.77 (m, 10H), 8.05 (dd, J = 8.2, 1.6 Hz, 2H), 7.89-‐7.81 (m, 8H), 7.71 (d, J = 8.6 Hz, 4H), 7.66 (d, J = 8.6 Hz, 4H), 1.54 (t, J = 7.0 Hz, 4H), 13 1.35 (t, J = 7.0 Hz, 4H) ppm. C NMR (126 MHz, CDCl3) δ 151.81, 151.70, 151.66, 151.43, 151.23, 151.03, 141.58, 139.46, 132.21, 131.67, 131.05, 131.01, 130.99, 130.95, 129.86, 129.80, 129.78, 129.77, 129.74, 129.25, 128.50, 122.59, 122.49, 122.18, 122.15, 122.09, 120.25, 73.57, 65.48, 57.56, 21.61 ppm (one signal missing – assuming that the 11 diastereomers have overlapping signals). B NMR (160 MHz, • + CDCl3) δ -‐15.2 ppm. HRMS (MALDI+): m/z [M ] calcd for • + [C68H38B2Br2N12O2 ] 1234.1790, found 1234.1791. Compound 14 (mixture of diastereoisomers). To a degassed solution of Et3N/toluene 1:3 (3 mL) was added TMS-‐acetylene (60 mg, 0.085 mL, 0.61 mmol, 40 equiv.), and the mixture was degassed for 1 min. The mixture was transferred to an argon-‐ purged flask containing 12 (18 mg, 0.015 mmol), Pd2dba2 (3.4 mg, 0.0037 mmol, 25 mol%), CuI (0.7 mg, 0.004 mmol, 25 mol%), and AsPh3 (9.3 mg, 0.031 mmol, 2 equiv.). The suspension was stirred for 3 h at rt after which the reaction mixture was diluted with EtOAc (3 mL) and passed through a short plug of silica eluting with EtOAc/toluene 1:1. The filtrate was concentrated to dryness, redissolved in CH2Cl2, and subjected to flash column chromatography (SiO2, 10% EtOAc/toluene) to yield 14 as a brown shiny solid (12 mg, 1 70%). Rf = 0.3 (10% EtOAc/toluene). M.p. >230 °C. H NMR (CDCl3, 500 MHz) δ 8.95 (br s, 2H), 8.84-‐7.78 (m, 8H), 8.74 (dd, J = 8.2, 0.7 Hz, 2H), 7.91 (dd, J = 8.3, 1.5 Hz, 2H), 7.90-‐7.86 (m, 8H), 1.51 (t, J = 7.0 Hz, 4H), 1.30 (t, J = 7.0 Hz, 4H), 0.30 (s, 18H) 13 ppm. C NMR (CDCl3, 126 MHz) δ 152.27, 152.26, 151.76, 150.77, 150.75, 132.82, 131.29, 131.26, 131.15, 131.11, 130.80, 130.04, 130.03, 129.95, 126.12, 124.52, 122.36, 122.31, 122.31, 122.27, 122.01, 105.07, 97.28, 73.70, 65.58, 57.70, 21.75, 0.11 ppm (three signals missing due to overlap – assuming that the diastereoisomers have overlapping signals). 11 B NMR (CDCl3, 160 MHz) δ -‐15.1 ppm. HRMS (MALDI+): m/z • + • + [M ] calcd for [C66H48B2N12O2Si2 ] 1118.3742, found 1118.3663. Compound 15 (racemic mixture). To an argon-‐flushed mixture of Et3N/toluene (1:3) was added TIPS-‐acetylene (0.50 mL, 2.3

mmol, 40 equiv.), and the resulting mixture was View flushed with Article Online DOI: 10.1039/C7OB01907F argon under sonication for 1 min. The mixture was added to an argon-‐purged flask containing 10 (38 mg, 0.05 mmol), Pd2dba3 (13 mg, 0.01 mmol, 25 mol%), CuI (2.7 mg, 0.01 mmol, 25 mol%) and AsPh3 (35 mg, 0.11 mmol, 200 mol%). The reaction mixture was stirred for 30 min after which the mixture was passed through a small plug of SiO2 eluting with EtOAc/toluene (1:1), concentrated in vacuo and subjected to flash column chromatography (SiO2, 10% EtOAc/toluene) followed by size-‐ exclusion chromatography (Biobeads SX-‐3, CH2Cl2) to yield 15 (38 mg, 92%) as a purple solid. Rf = 0.4 (5% EtOAc/toluene). 1 M.p. >230 °C. H NMR (CDCl3, 500 MHz) δ 8.96 (s, 1H), 8.86-‐ 8.83 (m, 4H), 8.75 (d, J = 8.3 Hz, 1H), 7.95 (dd, J = 1.4, 8.3 Hz, 1H), 7.91 (dd, J = 5.9, 3.0 Hz, 4H), 1.57 (t, J = 7.4 Hz, 2H), 1.40 13 (t, J = 7.4 Hz, 2H), 1.20 (s, 21H), -‐0.01 (s, 9H) ppm. C NMR (CDCl3, 126 MHz) δ 152.26, 152.22, 151.82, 151.74, 150.81, 150.76, 133.07, 131.29, 131.22, 131.17, 131.11, 130.82, 130.08, 130.01, 129.86, 125.99, 124.99, 122.35, 122.35, 122.97, 121.97, 107.01, 103.12, 93.98, 85.34, 57.88, 22.29, 18.90, 11.54, 0.11 ppm (three signals missing due to overlap). + + HRMS (MALDI+): m/z [M+H] calcd for [C42H44BN6OSi2] 717.3359, found 717.3353. Compound 16 (racemic mixture). AgF (5.3 mg, 0.008 mmol, 1 equiv.) was added to a solution of 15 (28 mg, 0.008 mmol) in MeCN/toluene 1:1 (1 mL), and the reaction mixture was stirred for 30 min, after which the reaction mixture was washed with 0.1 M HCl (3 x 20 mL). The organic phase was dried over MgSO4, concentrated in vacuo, and subjected to flash column chromatography (SiO2, 10% EtOAc/toluene) to afford 11 (14 mg, 55%) as a purple solid. Rf = 0.3 (5% EtOAc/toluene). M.p. 1 >230 °C. H NMR (CDCl3, 500 MHz) δ 8.96 (s, 1H), 8.86-‐8.84 (m, 4H), 8.75 (d, J = 8.2 Hz, 1H), 7.95 (dd, J = 1.4, 8.2 Hz, 1H), 7.92-‐ 7.90 (m, 4H), 1.60 (t, J = 7.0 Hz, 2H), 1.56 (t, J = 2.7 Hz, 1H), 13 1.36 (td, J = 7.0, 2.7 Hz, 2H), 1.20 (m, 21H) ppm. C NMR (CDCl3, 126 MHz) δ 152.25, 152.21, 151.82, 151.73, 150.81, 150.75, 133.08, 131.31, 131.25, 131.21, 131.14, 130.85, 130.09, 130.02, 129.89, 129.86, 127.14, 125.99, 125.00, 123.66, 122.36, 122.34 122.31, 121.97, 107.01, 94.00, 81.00, 68.93, 57.94, 20.99, 18.90, 11.55 ppm. HRMS (MALDI+): m/z + + [M+H] calcd for [C42H44BN6OSi2] 717.3359, found 717.3353. Compound 18. Method A: To an argon-‐flushed mixture of MeCN/CH2Cl2 1:1 (5 mL) were added 17 (100 mg, 0.215 mmol), PhI(OAc)2 (208 mg, 0.646 mmol, 3 equiv.), KI (358 mg, 2.15 mmol, 10 equiv.), CuI (8.2 mg, 0.04 mmol, 0.20 equiv.), and Et3N (2.5 mL). The reaction mixture was stirred for 2 h at rt after which it was partitioned between CH2Cl2 (20 mL) and H2O (20 mL). The aqueous phase was extracted with CH2Cl2 (2 x 20 mL). The combined organic phases were dried over MgSO4, concentrated to dryness, and subjected to flash column chromatography (SiO2, 5% EtOAc/toluene) to yield 18 as a purple solid (24 mg, 20%). Method B: To a stirring solution of 17 (50 mg, 0.11 mmol) and Et(i-‐Pr)2N (0.10 mL) in dry CH2Cl2 (2.5 mL) was added AgOTf (49 mg, 0.19 mmol), whereupon an immediate color change from red to dark purple took place. After 20 min, N-‐iodosuccinimide (37 mg, 0.16 mmol) was

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added, and stirring was continued for 1 h. The reaction mixture was diluted with EtOAc (3 mL), filtered through a short plug of SiO2 (EtOAc/CH2Cl2 1:1), and concentrated under reduced pressure. The remaining purple solid was repeatedly washed with MeOH, dried, redissolved in CH2Cl2, filtered and concentrated in vacuo to afford the title compound as a golden-‐brown crystalline solid (48 mg, 76%). Characterization 1 of 18: Rf (10% EtOAc/toluene) = 0.4. M.p. >230 °C. H-‐NMR (C6D6, 500 MHz) δ 8.77 (dd, J = 5.8, 3.0 Hz, 6H), 7.40 (dd, J = 5.8, 3.0 Hz, 6H), 1.46 (t, J = 7.0 Hz, 2H), 1.29 (t, J = 7.0 Hz, 2H) 13 ppm. C NMR (C6D6, 126 MHz) δ 151.65, 131.90, 129.63, 122.30, 91.53, 57.88, 23.46, -‐5.48 ppm. HRMS (MALDI+): m/z + + [M+H] calcd for [C28H17BIN6O] 591.0596, found 591.0586. Compound 19. An argon-‐flushed solution of Et3N in toluene 1:4 (8 mL) was added to an argon-‐purged flask containing 18 (20 mg, 0.03 mmol), TMS-‐acetylene (0.14 mL, 1.0 mmol, 30 equiv.), CuI (1.3 mg, 0.007 mmol, 20 mol%), Pd2dba3 (7.8 mg, 0.008 mmol, 25 mol%) and AsPh3 (10 mg, 0.03 mmol, 100 mol%). The reaction mixture was stirred for 1 h, passed through a short plug of silica eluting with EtOAc, concentrated in vacuo and subjected to flash column chromatography (SiO2, 10% EtOAc/toluene) to yield 19 as a purple solid (8 mg, 42%). 1 Rf = 0.3 (8% EtOAc/toluene). M.p. >230 °C. H NMR (CDCl3, 500 MHz) δ 8.84 (dd, J = 5.9, 3.0 Hz, 6H), 7.89 (dd, J = 5.9, 3.0 Hz, 6H), 1.58 (t, J = 7.3 Hz, 2H) 1.44 (t, J = 7.3 Hz, 2H), 0.14 (s, 9H) 13 ppm. C NMR (CDCl3, 126 MHz) δ 151.63, 131.10, 129.88, 11 122.27, 88.12, 83.49, 76.20, 66.13, 57.45, 21.76, -‐0.22 ppm. B NMR (CDCl3, 160 MHz) δ -‐15.2 ppm. HRMS (MALDI+): m/z + + [M+Na] calcd for [C33H25BN6OSiNa] 583.1844, found 583.1849. Compound 21. An argon-‐flushed solution of Et3N in toluene 1:4 (8 mL) was added to an argon-‐purged flask containing 18 (25 mg, 0.04 mmol), 20 (45 mg, 0.05 mmol, 1.2 equiv.), CuI (1.6 mg, 0.008 mmol, 20 mol%) and Pd2dba3 (9.7 mg, 0.01 mmol, 25 mol%). The reaction mixture was stirred for 48 h, passed through a short plug of silica eluting with CS2, concentrated and subjected to flash column chromatography (SiO2, 10% EtOAc/toluene) to yield 21 as a purple solid (11 mg, 20%). Rf = 1 0.3 (5% EtOAc/toluene). M.p. >230 °C. H NMR (CDCl3, 500 MHz) δ 8.84 (dd, J = 5.9, 3.0 Hz, 6H), 7.88 (dd, J = 5.9, 3.0 Hz, 6H), 5.18 (s, 2H), 3.91 (t, J = 6.5 Hz, 2H), 1.79-‐1.74 (m, 4H) 1.66 (t, J = 6.2 Hz, 2H), 1.40 (p, J = 6.5 Hz, 2H), 1.37-‐1.25 (m, 8H), 13 0.84 (t, J = 7.0 Hz, 3H) ppm. C NMR (CDCl3, 126 MHz) δ 153.07, 151.95, 151.68, 147.65, 147.47, 146.54, 146.22, 146.08, 146.01, 145.89, 145.53, 145.34, 145.27, 145.22, 145.06, 144.83, 144.66, 144.47, 143.99, 143.90, 142.66, 142.45, 142.05, 141.60, 141.46, 141.42, 141.26, 140.73, 139.59, 135.21, 134.21, 131.24, 130.05, 122.44, 78.75, 78.18, 74.77, 72.51, 68.93, 66.72, 65.89, 57.53, 31.97, 29.86, 29.60, 29.44, 26.45, 22.85, 22.22, 14.32 ppm (one signal missing due + to overlap). HRMS (MALDI+): m/z [M+H] calcd for + [C99H36BN6O2] 1351.2987, found 1351.2932.

We thank University of Copenhagen for financial sView upport. Article Online DOI: 10.1039/C7OB01907F

Notes and references 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Acknowledgements

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14 | J. Name., 2012, 00, 1-‐3

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DOI: 10.1039/C7OB01907F



ARTICLE

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Interactions between tetrathiafulvalene units in dimeric structures - the influence of cyclic cores.

Cobalt-Catalyzed [2π + 2π] Cycloadditions of Alkenes: Scope, Mechanism, and Elucidation of Electronic Structure of Catalytic Intermediates.

Electronic Interactions of Michler's Ketone with DNA Bases in Synthetic Hairpins.

Structures of closed and open conformations of dimeric human ATM.

Dimeric pyrrole-imidazole alkaloids: synthetic approaches and biosynthetic hypotheses.

SARAH Domain-Mediated MST2-RASSF Dimeric Interactions.

Protein: nucleic acid interactions. I. Electronic structures of cytosine, indole, and guanine complexes.

The Wide and Unpredictable Scope of Synthetic Cannabinoids Toxicity.

Proteoglycans: structures and interactions.

Elucidation of the primary structures of proteins by mass spectrometry.

Geographic scope and accessibility of a centralized, electronic consult program for patients with recent fracture.

Dimeric interactions and complex formation using direct coevolutionary couplings.

Elucidation of operon structures across closely related bacterial genomes.

Interactions of triazine herbicides with biochar: Steric and electronic effects.

SAXS studies of RNA: structures, dynamics, and interactions with partners.

Structurally-modified subphthalocyanines: molecular design towards realization of expected properties from the electronic structure and structural features of subphthalocyanine.

Electronic structures of defects and magnetic impurities in MoS2 monolayers.

Electronic Structures of LNA Phosphorothioate Oligonucleotides.

Morphine-like peptides in mammalian brain: isolation, structure elucidation, and interactions with the opiate receptor.

Understanding the dynamics of monomeric, dimeric, and tetrameric α-synuclein structures in water.

Synthetic "interface" peptides alter dimeric assembly of the HIV 1 and 2 proteases.

Interactions of 4', 6-diamidine-2-phenylindole with synthetic polynucleotides.

Conformations and electronic structures of oxidized and reduced isoalloxazine.

Exciton interactions in synthetic porphyrin dimers.