Dalton Transactions View Article Online

Published on 24 September 2014. Downloaded by Iowa State University on 18/10/2014 04:31:13.

PAPER

Cite this: Dalton Trans., 2014, 43, 16486

View Journal | View Issue

Copper(I)-assisted red-shifted phosphorescence in Au(I)⋯Cu(I) heteropolynuclear complexes† Vincent J. Catalano,*a José M. López-de-Luzuriaga,*b Miguel Monge,b M. Elena Olmosb and David Pascualb Reactions between [Au(C6Cl2F3)(tht)] and P,N-donor bridging ligands of the type PPh2py and (PPh2)2phen lead to the homonuclear gold complexes [Au(C6Cl2F3)(PPh2py)] (1) and [Au2(C6Cl2F3)2{(PPh2)2phen}] (2). Subsequent addition of [Cu(CH3CN)4](BF4) leads to the formation of the corresponding gold–copper heterometallic complexes [Au2Cu(C6Cl2F3)2(PPh2py)2](BF4) (3) and [Au2Cu(C6Cl2F3)2{(PPh2)2phen)}(CH3CN)](BF4) (4). The four complexes have been structurally characterized and are luminescent. The

Received 16th July 2014, Accepted 29th August 2014

gold precursors show emissions arising from metal-perturbed intraligand transitions. The heterometallic complexes show a red shift of the emissions that is proposed to arise from an admixture of IL (intraligand)

DOI: 10.1039/c4dt02154a

and MLCT (metal-to-ligand-charge-transfer) transitions. DFT and TD-DFT calculations agree well with

www.rsc.org/dalton

these results.

Introduction The chemistry of polynuclear complexes bearing Au(I)⋯M (metallophilic) closed-shell interactions is an area that, in addition to the primary structural and synthetic objectives, has evolved towards interdisciplinary interests spreading over several areas such as supramolecular chemistry,1 theoretical investigations,2 photophysical properties3 or potential applications.4 From a structural perspective, it is well known that metallophilic interactions are strong enough to produce different multimetallic geometric arrangements including clusters or polymeric species.1 It is also known that many of these complexes display fascinating luminescence properties that are closely related to the presence and strength of metallophilic interactions.3 For instance, in assemblies with metalbased transitions, short metallophilic interactions decrease the HOMO–LUMO gap producing low energy emissions relative to their monometallic counterparts. Conversely, in the same complexes, charge transfer to high lying ligand based orbitals provokes the opposite effect, which leads to high energy emissions. Careful control of these two factors allows

a Department of Chemistry, University of Nevada, Reno, NV 89557, USA. E-mail: [email protected] b Departamento de Química, Universidad de La Rioja, Centro de Investigación en Síntesis Química (CISQ), Complejo Científico-Tecnológico, 26004-Logroño, Spain. E-mail: [email protected] † Electronic supplementary information (ESI) available. CCDC 1011349–1011352. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4dt02154a

16486 | Dalton Trans., 2014, 43, 16486–16497

for a more precise tuning of the photoluminescence, which is a promising property for practical applications. Usually, heavy metals, where relativistic effects strengthen the metal–metal attraction, are used in “closed-shell complexes” with gold(I).5 Lighter elements such as Ag(I) or Cu(I) also produce metallophilic interactions with Au(I) but to a lesser degree.6 With copper(I) ions, the interactions found with gold(I) are due mainly to an ionic effect, enhanced by a small yet non-negligible electronic correlation term that ranges from 25 to 51 kJ mol−1, depending on the charge distribution.7 The study of mixed-metal Au(I)–Cu(I) complexes is interesting because, in addition to the interesting intrinsic features associated with Au(I), the added Cu(I) center can provide additional bonding and optical properties. From a photophysical viewpoint, Cu(I) complexes typically possess longer emission lifetimes (μs) than its heavy metal congeners. This coupled with its other desirable features make Cu(I) complexes attractive targets for the development of MOLEDs.8 Additionally, photoactive copper(I) complexes have been reported to act as spectroscopic reporter probes of DNA conformation due to the high affinity of these nuclei for N-donor centers.9 The synthesis of Au(I)–Cu(I) complexes has followed three main strategies: those utilizing the Lewis acidic characteristics of Cu(I) precursors with Lewis bases, mainly bis( perhalophenyl)gold(I) complexes in the presence of N-donor ligands which leads to unsupported Au(I)–Cu(I) interactions;10 the use of alkynyl metal clusters;11 or using polyfunctional P- and N-donor bridging ligands where the different binding affinities of gold(I) and copper(I) can be exploited to selectively coordinate both metal centers, allowing self-assembly into polynuclear aggregates.12 Depending on the rigidity of the

This journal is © The Royal Society of Chemistry 2014

View Article Online

Published on 24 September 2014. Downloaded by Iowa State University on 18/10/2014 04:31:13.

Dalton Transactions

molecular skeleton, the metal–metal interactions can, in principle, be maintained in solution, which is important because these metal–metal interactions are often responsible for the unique optical properties observed in the solid state. Nevertheless, in spite of the apparent simplicity of the reactions using polyfunctional P-, N-donor ligands, there are only a few examples reported starting from the first pioneering work of Schmidbaur et al. in 1997,13 where the existence of the Au(I)–Cu(I) interaction is undoubtedly established by means of X-ray diffraction studies. Therefore, taking into account the above comments, in this paper we present the coordinative properties of two P- and N-donor polyfunctional ligands, PPh2py and (PPh2)2phen, with gold(I) and copper(I) precursors where selective coordination to phosphorus and nitrogen is produced. The different rigidity of the ligand scaffold leads to distinctive geometries that influence the optical properties of the resulting complexes.

Results and discussion Synthesis and characterization The complexes [Au(C6Cl2F3)(PPh2py)] (1) (PPh2py = 2-(diphenylphosphino)pyridine) and [Au2(C6Cl2F3)2{(PPh2)2phen}] (2) ((PPh2)2phen = 2,9-bis(diphenyl-phosphino)-1,10-phenanthroline) were prepared by reaction of the corresponding ligand PPh2py (1) or (PPh2)2phen (2) with one equivalent of [Au(C6Cl2F3)(tht)] (tht = tetrahydrothiophene) (1), or with two equivalents (2) in dichloromethane. After 30 min, evaporation of the solvent and addition of n-hexane (20 mL) led to the isolation of complexes 1 and 2. Treatment of the aforementioned colourless gold(I) compounds with one equivalent of [Cu(CH3CN)4](BF4) in dichloromethane as a solvent produces

Scheme 1

Paper

the yellow mixed-metal salts, [Au2Cu(C6Cl2F3)2(PPh2py)2](BF4) (3) and [Au2Cu(C6Cl2F3)2{(PPh2)2phen)}(CH3CN)](BF4) (4), respectively (see Scheme 1). The NMR spectra of 1 and 3 were acquired using CDCl3 as a solvent; however, due to the low solubility of 2 in this solvent, d8-THF was used for NMR experiments of 2 and 4. The 19F NMR spectra of complexes 1–4 display the signals associated with the C6Cl2F3 ligands coordinated to gold centers. The observed chemical shifts for the gold (1) and gold–copper (3) complexes are different. Thus, the signal of the fluorine atoms in the ortho position appears at −90.0 for 1 and −86.7 ppm for 3. This signal shift probably arises from the copper(I) coordination to the N-atoms of the PPh2py ligand and from the fact that the metallophilic interactions would remain in solution. In addition, another signal centered at −152.1 ppm is observed in the 19F NMR spectrum of 3 that corresponds with the tetrafluoroborate anion. A similar behaviour is observed in the 1 H NMR spectra of these compounds in which the signals of the protons of the pyridine rings of the heterometallic complex 3 appear slightly shielded (see the Experimental section). However, the 31P{1H} NMR spectrum shows in both cases a very similar chemical shift, i.e. 41.0 (1) and 40.8 ppm (3). Complexes 2 and 4 also display distinct 19F NMR spectra with signals corresponding to the C6Cl2F3 groups bonded to Au(I) at −86.6 (Fo) and −114.0 ppm (Fp) in 2 and −93.2 (Fo) and −120.3 ppm (Fp) for the heterometallic complex 4. Additionally, in the spectrum of complex 4 a signal at −157.2 ppm due to the presence of the BF4− anion also appears. The 31P{1H} NMR spectra of 2 and 4 display one singlet at 40.0 or 43.0 ppm, respectively. As in the former complexes, the differences found in the 19F and 31P{1H} NMR spectra for complexes 2 and 4 suggest that the Au(I)⋯Cu(I) interactions are main-

Synthesis of complexes 1–4.

This journal is © The Royal Society of Chemistry 2014

Dalton Trans., 2014, 43, 16486–16497 | 16487

View Article Online

Published on 24 September 2014. Downloaded by Iowa State University on 18/10/2014 04:31:13.

Paper

Dalton Transactions

tained in solution. In addition, 19F NMR experiments at different concentrations (10, 40 and 70 mM) of complexes 3 and 4 show the signals corresponding to the C6Cl2F3 ligands at similar chemical shifts. This fact suggests that the copper(I) remains coordinated in solution even at low concentrations. The IR spectra of 1–4 in Nujol mulls show absorptions arising from Au(C6Cl2F3) groups at 1572, 1562, 1042 and 772 cm−1 (see the Experimental section). Furthermore, complex 4 shows one absorption at 2326 cm−1, assigned to the ν(CuN) stretching vibration of the acetonitrile ligand coordinated to the Cu(I) center in the solid state. In addition, the ν(CvN) stretching vibration of the phenanthroline moiety of the diphosphine ligand consists of two bands at 1592 and 1571 cm−1. X-Ray structural determination ˉ with Compound 1 crystallizes in the triclinic space group P1 two molecules in the asymmetric unit. As shown in Fig. 1, each gold center is two-coordinate and nearly linear with P1– Au1–C1 and P2–Au2–C24 angles of 174.55(11) and 173.35(11)°, respectively. The Au1–C1 and Au2–C24 separations at 2.052(4) and 2.053(4) Å are typical of gold–aryl coordination. Likewise, the phosphine–gold distances (Au1–P1 = 2.2803(10), Au2–P2 = 2.2775(10) Å) are not unusual. The two P–Au–C units orient themselves closer to orthogonal than colinear with a P–Au– Au–P torsion angle of 66.72° and a long Au1–Au2 separation (4.246 Å). The aryl–aryl separation is shorter with a centroid– centroid separation of 3.629 Å. It is likely that this interaction rather than the Au–Au interaction dictates the intermolecular packing.

Fig. 1 X-ray crystal structure drawing (50% thermal ellipsoids) of 1 showing both independent molecules of the asymmetric unit. Hydrogen atoms are omitted for clarity. Selected bond distances (Å) and angles (°): Au1–C1 2.052(4), Au1–P1 2.2803(10), Au2–C24 2.053(4), Au2–P 2.2775 (10), P1–Au1–C1 174.55(11), P2–Au2–C24 173.35(11).

16488 | Dalton Trans., 2014, 43, 16486–16497

Fig. 2 Thermal ellipsoid plot of 2. Hydrogen atoms are omitted for clarity. Only the asymmetric unit is numbered. The remaining atoms are generated by reflection through a mirror plane. Selected bond distances (Å) and angles (°): Au1–C1 2.054(3), Au1–P1 2.2750(8), P1–Au1–C1 174.87(9).

Compound 2 crystallizes in the monoclinic space group C2/c with one-half of the molecule in the asymmetric unit. The remainder is generated by a two-fold rotation operation. A thermal ellipsoid plot is presented in Fig. 2. Not unexpectedly, the coordination environment of 2 is similar to that of 1. The gold centers adopt a linear, two-coordinate geometry with similar metrical parameters. The Au1–C1 and Au1–P1 separations measure 2.054(3) and 2.2750(8) Å, respectively, and the P1–Au1–C1 angle is close to linear at 174.87(9)°. The Au centers are oriented away from each other such that the intramolecular Au–Au separation is very long at 11.7 Å. Absent are any intermolecular aurophilic attractions. In the extended lattice the perhaloaryl rings are positioned over the central ring of a neighboring phenanthroline moiety with a centroid– centroid separation of 3.637 Å. The multimetallic complex 3 crystallizes in the triclinic ˉ. The cationic portion is shown in Fig. 3. The spacegroup P1 cation consists of a triangular Au2Cu core comprised of two (PPh2py)Au(C6Cl2F3) subunits oriented in a head to tail fashion rotated ca. 52° from colinearity and coordinated to the copper center via the two pyridyl groups. Excluding intermetallic contacts, all three metals adopt slightly bent two-coordinate geometries with P1–Au1–C1, P2–Au2–C24, and N1–Cu1–C2 angles of 167.99(12), 172.24(12), and 166.92(16)°, respectively with each metal slightly puckered towards the center of the Au2Cu core. The rigidity of the PPh2py ligand and the triangular nature of this trimetallic core prevent a coplanar arrangement of the pyridyl rings which are oriented with a dihedral angle of ca. 82.5°. The Au1–Au2 separation at 3.0689(2) Å is only slightly longer than the heterometallic Au1–Cu1 and Au2– Cu1 separations at 2.9647(6) and 2.8403(5) Å, respectively. Likewise, the intermetallic angles are similar and close to the 60° ideal of an equilateral triangle (Au1–Cu1–Au2 = 63.788(12),

This journal is © The Royal Society of Chemistry 2014

View Article Online

Published on 24 September 2014. Downloaded by Iowa State University on 18/10/2014 04:31:13.

Dalton Transactions

Fig. 3 X-ray structural drawing (50% thermal ellipsoids) of the core of the cationic portion of 3. All but the ipso atoms of the phenyl rings and the hydrogen atoms are omitted for clarity. Selected bond distances (Å) and angles (°): Au1–C1 2.056(4), Au1–P1 2.2916(11), Au2–C24 2.068(4), Au2–P 2.2988(10), Cu1–N1 1.908(3), Cu1–N2 1.907(4), Au1–Au2 3.0689(2), Au1–Cu1 2.9647(6), Au2–Cu1 2.8403(5), Au1–Cu1–Cu2 63.788(12), Cu1–Au1–Au2 56.134(11), Au1–Au2–Cu1 60.079(12), N1–Cu1–N2 166.92(16), P1–Au1–C1 167.99(12), P2–Au2–C24 172.24(12).

Au1–Au2–Cu1 = 60.079(12), Cu1–Au1–Au2 = 56.134(11)°). These parameters are not too dissimilar to those reported for the closely related chloro-species, Au2CuCl2(PPh2py)2;12d however, the Au–Cu separations in 3 are longer than the 2.71–2.73 Å distances found in the three-coordinate [AuCu(PPh2py)3]2+ species.12c Finally, coordination of copper to the pyridyl rings induces a slight lengthening of the gold–ligand bonds relative to those in compounds 1 and 2. In 3 the Au1–P1 and Au2–P2 distances measure 2.2916(11) and 2.2988(10) Å while the Au1–C1 and Au2–C24 bonds are slightly lengthened to 2.056(4) and 2.068(4) Å. ˉ with Complex 4 crystallizes in the triclinic spacegroup P1 one-half of a dichloromethane solvate. A drawing of the cationic portion is presented in Fig. 4. The trimetallic complex consists of two nearly colinear P–Au–C6Cl2F3 subunits oriented toward the same face of the (PPh2)2phen ligand straddling the three-coordinate Cu(I) center which is bound to the nitrogen atoms of the phenanthroline ligand and to one acetonitrile molecule. The fairly rigid geometry of the (PPh2)2phen ligand prevents close association of the Au(I) centers with the cuprous ion. The Au1–Cu1 separation measures 3.969 Å while the Au2– Cu1 separation is slightly shorter at 3.537 Å. The Au1–Cu1–Au2 angle is bent at 104.26°. Both gold centers are two coordinate and nearly linear with P1–Au1–C1 and P2–Au2–C19 angles of 176.56(5) and 173.39(5)°, respectively. The copper center resides in a distorted trigonal planar environment. The

This journal is © The Royal Society of Chemistry 2014

Paper

Fig. 4 X-ray structural drawing (50% thermal ellipsoids) of the core of the cationic portion of 4. All but the ipso atoms of the phenyl rings and the hydrogen atoms are omitted for clarity. Selected bond distances (Å) and angles (°): Au1–C1 2.0528(17), Au1–P1 2.2772(4), Au2–C19 2.0551(16), Au2–P 2.2835(4), Cu1–N1 2.1330(14), Cu1–N2 1.9823(13), Cu1–N3 1.8586(15), P1–Au1–C1 176.56(5), P2–Au2–C19 173.39(5), N1–Cu1–N2 82.27(6), N1–Cu1–N3 126.54(6), N2–Cu1–N3 151.12(6), Au1⋯Cu1 3.969, Au2⋯Cu1 3.537, Au1–Cu1–Au2 104.26, Cu1–N3–C49 170.84(15).

constrained bite of the phenanthroline ligand limits the N1– Cu1–N2 angle to 82.27(6)°. The N1–Cu1–N3 angle at 126.54(6) is close to the ideal trigonal planar angle of 120°; however, the remaining N2–Cu1–N3 angle is greatly expanded to 151.12(6)°. These angles sum to 359.93 demonstrating that the Cu center is within experimental error of being in a rigorously planar environment. The acetonitrile molecule coordinates slightly bent with a Cu1–N3–C49 angle of 170.84(15)° and a Cu1–N3 separation of 1.8586(15) Å. This distance is shorter than Cu– phenanthroline bond lengths where Cu1–N1 and Cu1–N2 are 2.1330(14) and 1.9823(13) Å, respectively. Although the perhalophenyl rings appear oriented towards each other in a favorable intramolecular π–π stacking arrangement, their centroid–centroid separation is long at 4.355 Å. In the extended lattice these rings form close intermolecular associations with neighboring complexes with shorter centroid– centroid separations of 3.535 and 3.773 Å. Photophysical properties As expected for polynuclear closed-shell systems, 1–4 exhibit interesting photophysical properties related to their structural characteristics. The UV-Vis spectra in dichloromethane of the ligands show similar features. Both show three absorptions with similar relative intensities at 231, 261 and 293 nm and at 240, 269 and 336 nm for PPh2py and (PPh2)2phen, respectively.

Dalton Trans., 2014, 43, 16486–16497 | 16489

View Article Online

Published on 24 September 2014. Downloaded by Iowa State University on 18/10/2014 04:31:13.

Paper

Previous studies have suggested that the lowest energy absorption of arylphosphines is due to an n→π* (also called l→aπ) transition, i.e. a transition involving the promotion from the lone pair of the phosphine to an antibonding π* orbital of the arene. This band is not always detectable because it is often masked by more intense π→π* transitions.14,15 For the PPh2py species, the band at 293 nm disappears upon coordination of the ligand to the metal. This is interpreted as a shift to higher energy because of the transformation of the initial l→aπ to a σ → aπ transition by stabilization of the electron pair by coordination of the gold atoms. In the case of complexes 1 and 3 this band is probably masked by the more intense π→π* bands. In the case of the heteronuclear [Au2Cu(C6Cl2F3)2(PPh2py)2](BF4) (3) complex, the spectrum shows a band of very low intensity at ca. 360 nm that is not present either in the gold precursor or in the ligand. This new, low energy feature is assigned to a transition between orbitals that appears as a consequence of the interaction between the metal centers (see Fig. 10 in the DFT calculations section). Note that the excitation energy in the solid state of this complex appears roughly at the same energy (see below). By contrast, in the case of the (PPh2)2phen complexes, 2 and 4, the assignment of the transitions is not clear since the area with the band at 336 nm (assigned to the l→aπ transition in the free ligand) overlaps with the low energy tails in the complexes. Therefore, the disappearance or shift of this band is not apparent. Nevertheless, distinct, new absorption appears at 293 and 299 nm for complexes 2 and 4, respectively. These are not present in the free ligand and probably correspond to the σ→aπ transitions. In the heteronuclear complex 4, we cannot detect a transition due to the interactions of the metal centers, although the low energy absorption tail would probably mask it. Complexes 1–4 show interesting emissive properties, which can be related to their structure and metal composition. Under UV illumination, all the complexes are luminescent in the solid state at room temperature. The monometallic gold complex 1 displays an emission centered at 465 nm (Exc. 310 nm), which shifts to 425 nm when the temperature is decreased to 77 K. The ligand PPh2py shows an emission at 483 nm, which shifts to 474 nm (Exc. 320 nm) at low temperature. The latter emission shows a vibrational structure with a spacing of ca. 650 cm−1 between peaks, which is in accordance with an in-plane ring deformation of the pyridyl ring.16 Consequently, the emission is assigned to arise from orbitals of the pyridyl ring. The close proximity between the bands of the ligand and gold complex 1 suggests a similar origin, although perhaps slightly perturbed by the presence of the C6Cl2F3Au moiety. Therefore, the emission of 1 is likely to arise from a metal-perturbed, intraligand (IL) transition. A similar situation appears with complex 2 and the free ligand (PPh2)2phen. The free ligand displays a broad emission centered at 472 nm, which is shifted to 530 nm (exc. 365 nm) at 77 K. At low temperature the emission is slightly structured with a spacing of ca. 700 cm−1, assigned similarly to a vibrational mode in the phenanthroline rings. In complex 2, the spectra show a broad and structured emission band with a

16490 | Dalton Trans., 2014, 43, 16486–16497

Dalton Transactions

larger spacing (ca. 1400 cm−1), centered at 535 nm (Exc. 360 nm), suggesting a different vibrational mode of the phenanthroline ligand or one that arises from the perhalophenyl rings. In fact, vibrations between 1100–1020 and 1250–1100 cm−1 are expected for C–Cl and C–F containing aryl systems.17 Likely the emission in complex 2 is intraligand (IL) in nature, probably arising from orbitals of the phenanthroline or perhalophenyl ligands. A very different situation appears when copper is introduced in the complexes. In both complexes 3 and 4 the emissions are considerably red shifted from those of their precursor gold complexes. In the spectra of [Au2Cu(C6Cl2F3)2(PPh2py)2](BF4) (3), the emission appears at 542 nm (Exc. 390 nm) at room temperature and at 522 nm (Exc. 375 nm) at 77 K. For [Au2Cu(C6Cl2F3)2{(PPh2)2phen}(CH3CN)](BF4) (4), the shift is even bigger showing an emission at 615 nm (Exc. 455 nm) at room temperature and 623 nm (Exc. 386 nm) at 77 K. In both cases, the emission bands are broad and asymmetric. Also, both have lifetimes in the microsecond range (see Table 2 and Fig. 5). These values, together with the large Stokes-shift (ca. 7100 and 5750 cm−1) between maxima of excitation and emission peaks for complexes 3 and 4, respectively, suggest phosphorescent emissions. Thus, it is likely that these emissive states arise as a consequence of the interaction between copper and the gold centers with a contribution of the perhalophenyl and phosphino-pyridine or -phenanthroline ligands. Therefore, the emissions can be described as arising from an admixture of metal(Au2Cu)-centered (MC) and intraligand (IL) transitions, although an admixture of IL and MLCT (metal (Au2Cu) to ligand charge transfer) transitions is also possible. In previous examples of mixed-metal gold–copper complexes bearing nitrogen donor ligands, the emissions were ascribed to arise from transitions between Au( perhalophenyl)Cu moieties and N-donor ligands of the type: nitriles or pyrimidine.10c–e Therefore, a similar assignment in this case cannot be ruled out. Interestingly, while the PPh2py molecule and complexes 1 and 3 are not luminescent in solution, (PPh2)2phen and its derivatives display structured emissions in tetrahydrofuran solutions at room temperature. All display identical emissions centered at 436 nm (Exc. 373 nm) (Fig. 6). The structure observed and the fact that the emissions appear at the same energy suggest that the emissions arise from intraligand transitions. As we have mentioned above, all of the complexes are emissive in the solid state. Complex 2 and, to a greater degree, 4 have solid state emissions considerably red-shifted relative to their solution state spectra. The loss of the solid state emissions upon dissolution has been repeatedly proposed as a consequence of the rupture of the interactions promoted by the solvent molecules.3c Nevertheless, in this case, the C6Cl2F3Au moieties seem to remain bonded to the phosphorus centers and the 31P NMR data indicate that the phosphorus centers are deshielded with respect to the positions of the free ligand (−3.9 ppm for (PPh2)2phen; 40.0 ppm for [Au2(C6Cl2F3)2{(PPh2)2phen}] (2); 43.0 ppm for [Au2Cu(C6Cl2-

This journal is © The Royal Society of Chemistry 2014

View Article Online

Dalton Transactions

Published on 24 September 2014. Downloaded by Iowa State University on 18/10/2014 04:31:13.

Table 1

Paper

X-ray crystallographic data for 1–4

Compound

1

2

3

4·0.5CH2Cl2

Formula M Crystal system Space group a/Å b/Å c/Å α/° β/° γ/° V/Å3 T/K Z ρ/Mg m−3 μ/mm−1 F(000) θ range/° No. data collected No. unique data Rint R1, wR2 a [I > 2σ(I)] R1, wR2 a (all data) GOF (F2)b CCDC number

C46H28Au2Cl4F6N2P2 1320.38 Triclinic ˉ P1 12.1417(4) 14.0807(4) 14.7208(4) 112.334(1) 106.426(1) 93.741(1) 2190.20(11) 100(1) 2 2.002 1.070 1256 1.586–27.499 46 019 10 052 0.0592 0.0286, 0.0513 0.0416, 0.0540 1.003 1011349

C48H26Au2Cl4F6N2P2 1342.38 Monoclinic C2/c 24.6243(7) 12.2228(4) 17.6926(9) 90 123.7960(6) 90 4425.3(3) 100(1) 4 2.015 7.001 2552 1.941–29.997 40 972 6470 0.0664 0.0279, 0.0470 0.0457, 0.0500 1.007 1011350

C46H28Au2BCl4CuF10N2P2 1470.73 Triclinic ˉ P1 10.3133(3) 13.8966(5) 16.5360(6) 90.076(1) 95.019(1) 104.846(1) 2281.35(13) 100(1) 2 2.141 7.261 1396 1.516–31.500 49 768 15 057 0.0423 0.0372, 0.0808 0.0547, 0.0850 1.081 1011351

C50.5H29Au2BCl5Cu F10N3P2 1575.24 Triclinic ˉ P1 8.6930(3) 14.8328(5) 20.3022(6) 80.559(1) 86.516(1) 88.464(1) 2577.19(15) 100(1) 2 2.030 6.485 1500 1.392–30.508 65 604 15 695 0.0214 0.0159, 0.0362 0.0190, 0.0369 1.028 1011352

R1(F) = ∑||Fo| − |Fc||/∑|Fo|. wR(F2) = [∑{w(Fo2 − Fc2)2}/∑{w(Fo2)2}]0.5; w−1 = σ2(Fo2) + (aP)2 + bP, where P = [Fo2 + 2Fc2]/3 and a and b are constants adjusted by the program. b GOF(F2) = [∑{w(Fo2 − Fc2)2}/(n − p)]0.5, where n is the number of data and p the number of parameters.

a

Table 2

Photophysical properties of ligands PPh2py and (PPh2)2phen and complexes 1–4

Complex

Medium (T [K])

λabs [nm] (ε [M−1 cm−1])

PPh2py

CH2Cl2 (RT) Solid (RT) Solid (77 K) THF (RT) Solid (RT) Solid (77 K) CH2Cl2 (RT) Solid (RT) Solid (77 K) THF (RT) Solid (RT) Solid (77 K) CH2Cl2 (RT) Solid (RT) Solid (77 K) THF (RT) Solid (RT) Solid (77 K)

231 (8600), 261 (6500), 293 (1100)

(PPh2)2phen [Au(C6Cl2F3)(PPh2py)] (1) [Au2(C6Cl2F3)2{(PPh2)2phen}] (2) [Au2Cu(C6Cl2F3)2(PPh2py)2](BF4) (3) [Au2Cu(C6Cl2F3)2{(PPh2)2phen}](BF4) (4)

F3)2{(PPh2)2phen}(CH3CN)](BF4) (4)). Therefore, we propose that the geometry of the complex 4 remains in solution, although the emission from the triplet excited state is probably quenched by solvent molecules and a singlet-to-singlet transition is more likely as it happens in the free ligand. DFT and TD-DFT calculations In view of the interesting photophysical properties displayed by the heterometallic Au–Cu compounds we have carried out DFT calculations on different trimetallic model systems by optimizing the ground (S0) and the lowest triplet excited state (T1). The main goal of these calculations is to describe the T1

This journal is © The Royal Society of Chemistry 2014

λem (λexc) [nm]/τ [μs]/Φ (%)

240 (25 000), 269 (15 000), 336 (5400)

483(400) 474 (320) 436 (373) 472 (370) 530 (365)

236 (11 875), 259 (5250), 276 (1875) 465(310)/1.15/3 425(320) 436 (373) 535 (360)/0.17, 1.02/18 529 (345)

241 (32 000), 293 (12 333) 230 (11 250), 272 (5687), 360 (800) 241 (30 667), 299 (11 667)

542 (390)/2.82/14 522 (375) 436 (373) 615 (455)/2.71, 0.71/8 623(386)

excited state structural distortions with respect to the ground state, since these modifications rely interesting information about the possible origin of the phosphorescent emissions observed experimentally for complexes [Au2Cu(C6Cl2F3)2(PPh2py)2](BF4) (3) and [Au2Cu(C6Cl2F3)2{(PPh2)2phen}(CH3CN)](BF4) (4). We have chosen as model systems the trinuclear cationic molecules 3a and 4a (see Fig. 7) without any symmetry constraint or model simplifications with respect to the X-ray experimental structure, since our objective is to account for the role played by the interacting metals and also by the perhalophenyl and/or the diphosphine ligands in the photophysical properties.

Dalton Trans., 2014, 43, 16486–16497 | 16491

View Article Online

Published on 24 September 2014. Downloaded by Iowa State University on 18/10/2014 04:31:13.

Paper

Dalton Transactions

Fig. 5 Excitation (red) and emission (black) spectra for complexes 3 (dashed line) and 4 (solid line) in the solid state at 77 K.

Fig. 7 Theoretical model systems [Au2Cu(C6Cl2F3)2(PPh2py)2]+ (3a) and [Au2Cu(C6Cl2F3)2{(PPh2)2phen}(CH3CN)]+ (4a).

Table 3 Selected experimental and theoretical distances (Å) and angles (°) for complex 3 and model 3a in the ground (S0) and excited (T1) states

Fig. 6 Excitation (red) and emission (black) spectra for complex 4 in THF solution.

Tables 3 and 4 depict the most important structural parameters found for complexes 3 and 4 through X-ray diffraction studies and their comparison with the fully optimized molecules at the DFT/PBE level of theory for models 3a and 4a in the S0 and T1 states. The results for the optimized model systems in the ground state agree well with the experimental data. In the case of model 3a the measured intermetallic Au– Au distance is larger than the theoretically predicted one 3.46 Å vs. 3.07 Å; meanwhile the Au–Cu distances are quite similar, i.e. 2.96 and 2.84 Å experimental vs. 2.84 Å theoretical. In the case of the model system 4a, the intermetallic Au–Cu distances of 3.35 and 3.88 Å are slightly shorter than the experimental ones of 3.97 and 3.54 Å. The strength of the metallophilic interactions is not easy to determine since the metals are supported by the presence of the bridging phosphine ligands. However, in model 3a the interactions are short, and hence, they are probably stronger while in model 4a the long Au–Cu distances observed both experimentally

16492 | Dalton Trans., 2014, 43, 16486–16497

Au–Au Au1–Cu Au2–Cu Au1–P Au2–P Cu–N5 Cu–N7 Au–Cu–Au N–Cu–N P–Au1–C P–Au2–C

Exp. in 3

S0 in 3a

T1 in 3a

3.07 2.96 2.84 2.29 2.30 1.90 1.90 63.80 166.90 172.30 167.96

3.46 2.84 2.84 2.33 2.33 1.94 1.94 75.2 168.2 169.1 168.9

3.93 2.64 2.64 2.34 2.34 1.90 1.93 96.2 159.9 171.5 170.0

Table 4 Selected experimental and theoretical distances (Å) and angles (°) for complex 4 and model 4a in the ground (S0) and excited (T1) states

Au1–Cu Au2–Cu Cu–N12 Cu–N16 Cu–N20 Au–Cu–Au N12–Cu–N20 N16–Cu–N20 P–Au1–C P–Au2–C

Exp. in 4

S0 in 4a

T1 in 4a

3.97 3.54 2.13 1.98 1.85 104.26 126.63 151.00 173.35 176.55

3.88 3.35 2.16 2.02 1.88 101.4 129.8 149.1 174.5 176.1

4.30 2.69 2.04 1.90 1.93 104.1 110.2 160.1 171.5 176.3

This journal is © The Royal Society of Chemistry 2014

View Article Online

Published on 24 September 2014. Downloaded by Iowa State University on 18/10/2014 04:31:13.

Dalton Transactions

and theoretically preclude any strong closed-shell interactions. The rest of the structural parameters compared between the experimental data and the S0 structures for 3a and 4a are similar. When the structural parameters obtained for models 3a and 4a in the optimization of the lowest triplet excited state T1 are analysed, clear differences that mostly affect the Au(I) and Cu(I) environments are observed. Comparing the results obtained for model system [Au2Cu(C6Cl2F3)2(PPh2py)2]+ 3a in the T1 state to the optimized structure in the S0 ground state we note significant changes including a shortening of the Au1–Cu and Au2–Cu metallophilic distances from 2.84 Å (S0) to 2.64 Å (T1). In contrast, an increase of the Au1–Au2 distance to 3.93 Å is observed in the T1 state relative the ground state (S0) distance of 3.46 Å. The rest of the bonds around the metals or the more rigid C–N bonds in the pyridyl rings in the model suffer only slight changes (less than 0.05 Å). Also, the angle formed by Au1–Cu–Au2 opens to 96.2° (T1) from the acute angle of 75.2° found in the ground state (S0). Model 4a shows an asymmetrical behaviour in the T1 excited state with respect to the metallophilic interactions. The Au1–Cu distance elongates from 3.88 Å (S0) to 4.30 Å (T1), thereby losing the metal–metal contact while the Au2–Cu distance shortens from 3.35 (S0) to 2.69 Å (T1) leading to a very short metal–metal interaction. The coordination environment around the copper also suffers a distortion as evidenced by the changes in the N12–Cu–N20 and N16–Cu–N20 angles from 129.8° and 149.1° in the ground state to 110.2° and 160.1° in the T1 state, respectively. In the model 4a the degree of distortion of the Cu–N bonds is more pronounced than in model 3a leading to a clear shortening of the Cu–N distance with respect to the nitrogen atoms of the phenanthroline moiety (2.16 and 2.02 Å in the S0 state vs. 2.04 and 1.90 Å in the T1 state, respectively). Based on the calculated T1 excited state structures for models 3a and 4a it is apparent that the phosphorescent properties of these complexes should be related to transitions involving the metals and the N-donor moieties, because as can be seen in Tables 3 and 4, the intermetallic and Cu–N distances are the most distorted structural parameters of the molecules in the excited state. We have computed the electronic structure of models 3a and 4a in the S0 state, and we have carried out TD-DFT calculations in order to predict both the energy and the primary MO contributions to the lowest singlet–triplet theoretical excitations, which can be directly related to the origin of the phosphorescent behaviour of complexes 3 and 4. We have further explored the shape and the population analysis of the frontier molecular orbitals for both model systems. Some of these MOs are involved in the calculated triplet excitations (see Fig. 8 and 9 and Tables 5 and 6). For model 3a the highest occupied MOs are almost exclusively located on the C6Cl2F3 rings (HOMO and HOMO−1) or on these rings with some contribution from the metal centers as demonstrated in HOMO−2 (22% from Cu and 10% from Au) and HOMO−4 (33% from Cu and 13% from Au). The latter

This journal is © The Royal Society of Chemistry 2014

Paper

Fig. 8 Frontier orbitals involved in the lowest singlet–triplet transition for the model [Au2Cu(C6Cl2F3)2(PPh2py)2]+ (3a).

Fig. 9 Frontier orbitals involved in the lowest singlet–triplet transition for the model [Au2Cu(C6Cl2F3)2{(PPh2)2phen}(CH3CN)]+ (4a).

Dalton Trans., 2014, 43, 16486–16497 | 16493

View Article Online

Paper

Dalton Transactions

Published on 24 September 2014. Downloaded by Iowa State University on 18/10/2014 04:31:13.

Table 5 Population analysis for the model system [Au2Cu(C6Cl2F3)2(PPh2py)2]+ (3a). Contribution (%) from each part of the molecule to the occupied orbitals

3a

Cu

Au1

Au2

RAu1

RAu2

PPh2

Py

LUMO+1 LUMO HOMO HOMO−1 HOMO−2 HOMO−4

2 3 0 1 22 33

2 3 0 0 4 13

2 1 0 0 6 7

1 1 1 97 23 20

1 1 98 1 38 15

8 10 0 0 1 5

84 78 0 0 6 6

Table 6 Population analysis for the model system [Au2Cu(C6Cl2F3)2{(PPh2)2phen}(CH3CN)]+ (4a). Contribution (%) from each part of the molecule to the occupied orbitals

4a

Cu

Au1

Au2

RAu1

RAu2

PPh2

Phen

LUMO+1 LUMO HOMO HOMO−1 HOMO−2 HOMO−3 HOMO−4 HOMO−7 HOMO−12 HOMO−20

0 3 0 0 0 1 56 4 12 37

0 1 0 1 4 2 0 3 2 1

1 2 0 0 2 4 15 2 0 2

0 0 83 16 59 34 0 9 0 1

0 0 17 83 34 57 6 6 0 0

7 4 0 0 0 0 3 59 54 25

90 90 0 0 0 0 15 19 30 33

Table 7 TD-DFT first singlet–triplet excitation calculation for model systems 3a and 4a

Model

λcalc (nm)

Contributions (%)

3a

401.3

4a

511.2

HOMO−2 → LUMO (70) HOMO−4 → LUMO (30) HOMO−4 → LUMO (6.7) HOMO−7 → LUMO+1 (32.5) HOMO−12 → LUMO+1 (33.6) HOMO−12 → LUMO (5.3) HOMO−20 → LUMO+1 (21.9)

two orbitals are involved in the triplet excited state (vide infra). In contrast, the empty orbitals LUMO and LUMO+1 are mainly placed at the pyridyl rings of the P,N-donor ligand with a 78% and 85% contribution, respectively. The population analysis of model 4a produces similar results. The occupied orbitals, HOMO to HOMO−3, are mainly located at the perhalophenyl rings, whereas in the orbitals ranging from HOMO−4 to HOMO−20 the participation of the metals is larger, and these orbitals are mostly involved in the excited states giving rise to the emissions (vide infra). The empty orbitals, LUMO and LUMO+1, are located at the N-donor phenanthroline moiety. The TD-DFT calculations of the lowest singlet–triplet excitation also show similar results for both models (see Table 7). As can be observed the main MO contributions to this excited state arise from orbitals mostly located on the metals and the perhalophenyl rings in the case of model 3a and on the metals

16494 | Dalton Trans., 2014, 43, 16486–16497

Fig. 10 Absorption in CH2Cl2 (green line) and excitation in the solid state at RT (black line) spectra for complex 3 and theoretical singlet– triplet excitation for model 3a.

and the (PPh2)2phen ligand in the case of model 4a. The accepting orbitals involved in the theoretical excitations are almost exclusively placed on the N-donor units of the diphosphine ligands, pyridine and phenanthroline, respectively. It is worth noting that the singlet–triplet transition calculated for model 4a is more mixed than the one predicted for model 3a. The predicted energy values for the lowest singlet–triplet excitations are 401.3 and 511.2 nm, for models 3a and 4a, respectively (see Fig. 10 for comparison between theoretical and experimental data for complex 3). Therefore, from a theoretical viewpoint, we assign the phosphorescent emissions of 3 as an admixture of MLCT (metal (CuAu2)-to-ligand charge transfer) and LLCT (interligand charge transfer from C6Cl2F3 to py) whereas for 4 we assign the phosphorescent emissions as an admixture of IL (intraligand) and MLCT transitions.

Conclusions The use of asymmetric bidentate ligands allows the synthesis of heterometallic gold(I)–copper(I) complexes with intermetallic closed-shell interactions. The introduction of a copper(I) center into the gold(I) precursor complexes leads to a large redshift of the emissions in the solid state. The emissive states change from mostly intraligand transitions for the gold(I) precursors 1 and 2 to transitions involving the metals and the N-donor moieties in the heterometallic gold–copper complexes 3 and 4. Theoretical calculations confirm the nature of the emissive states for the heteronuclear compounds.

Experimental General The compounds [Au(C6Cl2F3)(tht)],18 PPh2py,19 and (PPh2)2phen20 were synthesized according to published procedures. Solvents (spectroscopic grade) used in the spectroscopic studies were degassed prior to use.

This journal is © The Royal Society of Chemistry 2014

View Article Online

Dalton Transactions

Published on 24 September 2014. Downloaded by Iowa State University on 18/10/2014 04:31:13.

Instrumentation Infrared spectra were recorded in the 4000–200 cm−1 range on a Nicolet Nexus FTIR using Nujol mulls between polyethylene sheets. Elemental analysis was performed on a Perkin–Elmer 240C microanalyzer. 31P{1H}, 1H, and 19F NMR spectra were recorded on a Bruker Avance 400 in CDCl3 or d8-THF; chemical shifts are quoted relative to 85% H3PO4 (31P), SiMe4 (1H), or CFCl3 (19F) as an external reference. Mass spectra were recorded on a HP-5989B Mass Spectrometer API-Electrospray with the interface 59987A. Absorption spectra in solution were registered on a Hewlett Packard 8453 Diode Array UV-visible spectrophotometer. Excitation and emission spectra were recorded on a Jobin–Yvon Horiba Fluorolog 3–22 Tau-3 spectrofluorimeter. Lifetime measurements were recorded on a Datastation HUB-B with a nanoLED controller and the DAS6 software. The lifetime data were fitted using the Jobin–Yvon software package. Synthesis Preparation of [Au(C6Cl2F3)2(PPh2py)] (1). To a solution of [Au(C6Cl2F3)2(tht)] (0.200 g, 0.34 mmol) in CH2Cl2 (35 mL) PPh2py ligand was added (0.090 g, 0.34 mmol) and the mixture was stirred for 30 min at RT. Evaporation of the solvent under vacuum and the addition of n-hexane gave rise to complex 1 as a white solid. Yield: 76%. Elemental analysis (%) calcd for 1 (C23H14AuCl2F3NP): C 41.84; H 2.14; N 2.12; found: C 41.80; H 2.16; N 2.15; 1H (CDCl3): 8.82 (s, 1H, py), 7.99 (s, 1H, py), 7.39–7.78 ppm (m, aromatic Hs); 19F NMR (CDCl3): −90.0 (t, 4JF–P = 7 Hz, 2F, Fo), −116.0 ppm (s, 1F, Fp); 31 P NMR (CDCl3): 41.0 ppm (t, 4JP–F = 7 Hz, 1P); MS (ES+): m/z 659.9886 [1 + H]+, 6 819 691 [1 + Na]+; FT-IR (Nujol mulls): ν 1575, 1563, 1041 and 778 cm−1 [Au(C6Cl2F3)]. Preparation of [Au2(C6Cl2F3)2{(PPh2)2phen}] (2). To a dichloromethane solution (35 mL) of [Au(C6Cl2F3)2(tht)] (0.200 g, 0.34 mmol) was added (PPh2)2phen (0.093 g, 0.17 mmol). A white suspension rapidly appears, and after stirring the mixture for 1 hour complex 2 was isolated by filtration as a white solid. Yield: 85%. Elemental analysis (%) calcd for 2 (C48H26Au2Cl4F6N2P2): C 42.95; H 1.95; N 2.09; found: C 42.94; H 1.96; N 2.11; 1H (d8-THF): 8.64 (m, 2H, phen), 8.52 (m, 2H, phen), 8.12 (s, 2H, phen), 8.05 (m, 8H, aromatic Hs), 7.38–7.49 ppm (m, 12H, aromatic Hs); 19F NMR (d8-THF): −86.6 (s, 4F, Fo), −114.0 ppm (s, 2F, Fp); 31P NMR (d8-THF): 40.0 ppm (t, 4JP–F = 7 Hz, 2P); MS (ES+): m/z 13 649 423 [2 + Na]+, FT-IR (Nujol mulls): ν 1572, 1503, 1044 and 775 cm−1 [Au(C6Cl2F3)]. Preparation of [Au2Cu(C6Cl2F3)2(PPh2py)2][BF4] (3). To a solution of [Au(C6Cl2F3)(PPh2py)] (1) (0.100 g, 0.15 mmol) in CH2Cl2 (35 mL) [Cu(CH3CN)4][BF4] was added (0.048 g, 0.075 mmol) and the mixture was stirred for 30 min at RT. Evaporation of the solvent under vacuum and the addition of n-hexane gave rise to complex 3 as a yellow solid. Yield: 81%. Elemental analysis (%) calcd for 3 (C46H28Au2BCl4CuF10N2P2): C 37.57; H 1.92; N 1.90; found: C 37.60; H 1.90; N 1.91; 1H (CDCl3): 8.26 (s, 1H, py), 7.87 (s, 1H, py), 7.48–7.63 ppm (m,

This journal is © The Royal Society of Chemistry 2014

Paper

aromatic Hs); 19F NMR (CDCl3): −86.7 (s, 4F, Fo), −115.3 (s, 2F, Fp), −152.1 ppm (s, 4F, BF4−); 31P NMR (CDCl3): 40.8 ppm (s, 2P); MS (ES+): m/z 13 829 102 [Au2Cu(C6Cl2F3)2(PPh2py)2]+; FT-IR (Nujol mulls): ν 1572, 1562, 1042 and 772 cm−1 [Au(C6Cl2F3)]. Preparation of [Au2Cu(C6Cl2F3)2{(PPh2)2phen}(CH3CN)][BF4] (4). To a suspension of complex 2 (0.100 g, 0.075 mmol) in 35 mL of dichloromethane was added [Cu(CH3CN)4][BF4] (0.048 g, 0.075 mmol). The reaction mixture was stirred for 1 h and the solution was concentrated to ca. 2 mL. The addition of n-hexane gave rise to the precipitation of complex 4 as a pale yellow solid. Yield: 89%. Elemental analysis (%) calcd for 4 (C50H29Au2BCl4Cu1F10N3P2): C 39.15; H 1.91; N 2.74; found: C 39.21; H 1.96; N 2.74; 1H (d8-THF): 8.86 (m, 2H, phen), 8.30 (s, 2H, phen), 7.78 (m, 8H, aromatic Hs), 7.64 (m, 2H, phen), 7.43–7.58 ppm (m, 12H, aromatic Hs); 19F NMR (d8-THF): −93.2 (s, 4F, Fo), −120.3 (s, 2F, Fp), −157.2 ppm (s, 4F, BF4−); 31 P NMR (d8-THF): 43.0 ppm (t, 4JP–F = 7 Hz, 2P); MS (ES+): m/z 14 048 939 [Au2Cu(C6Cl2F3)2{(PPh2)2phen}]+, FT-IR (Nujol mulls): ν 1575, 1508, 1041 and 771 cm−1 [Au(C6Cl2F3)], ν 2326 cm−1 (CuN), ν 1592–1571 cm−1 (CvN). Crystallography Crystals were grown via slow diffusion of n-hexane into dichloromethane solutions for complexes 1 and 3 and diethyl ether into dichloromethane solutions for complexes 2 and 4 at room temperature. Single-crystal intensity measurements were collected at 100(1) K with a Bruker Smart APEX II CCD area detector using graphite monochromated Mo Kα radiation (λ = 0.71073 Å). All data sets were reduced using Bruker SAINT21 and corrected for absorption using SADABS.22 All structures were solved by direct methods with SHELXS, and refined by full-matrix least-squares based on F2 with SHELXL. Graphics were prepared with Olex2.23 Crystal data are given in Table 1. The pyridyl rings of the diphenylphosphinopyridine ligands in 1 appear to be positionally disordered with the phenyl rings, and the nitrogen atom could not be reliably distinguished based on the Fourier difference maps. The final assignment was based on small differences in C–N bond distances. Additional crystallographic data and refinement details are available in CIF format in the ESI.† Computational details All calculations were carried out using the Gaussian 09 program package.24 DFT and time-dependent DFT calculations were carried out using the PBE functional.25 The following basis set combinations were employed for the metals Au and Cu: the 19-VE pseudopotentials from Stuttgart and the corresponding basis sets26 augmented with two f polarization functions were used,27 respectively. The rest of the atoms were treated by Stuttgart pseudopotentials,28 including only the valence electrons for each atom. For these atoms double-zeta basis sets of ref. 28 were used, augmented by d-type polarization functions.29 For the H atom, a double-zeta plus a p-type polarization function was used.30

Dalton Trans., 2014, 43, 16486–16497 | 16495

View Article Online

Paper

Acknowledgements

Published on 24 September 2014. Downloaded by Iowa State University on 18/10/2014 04:31:13.

D.G.I. (MEC)/FEDER ( project number CTQ2013-48635-C2-2-P) is acknowledged for the funding of our research. The Centro de Supercomputación de Galicia (CESGA) is acknowledged for computational resources. D. Pascual thanks the CAR for a grant.

Notes and references 1 Modern Supramolecular Gold Chemistry, ed. A. Laguna, Wiley-VCH, Weinheim, 2008. 2 (a) P. Pyykkö, Chem. Rev., 1997, 97, 597; (b) P. Pyykkö, Angew. Chem., Int. Ed., 2004, 43, 4412; (c) P. Pyykkö, Inorg. Chim. Acta, 2005, 358, 4113; (d) P. Pyykkö, Chem. Soc. Rev., 2008, 37, 1967. 3 (a) E. J. Fernández, A. Laguna and J. M. López-deLuzuriaga, Dalton Trans., 2007, 1969; (b) J. M. Forward, J. P. Fackler Jr. and Z. Assefa, in Optoelectronic Properties of Inorganic Compounds, ed. D. M. Roundhill and J. P. Fackler Jr., Plenum, New York, 1999, pp. 195–226; (c) J. M. Lópezde-Luzuriaga, in Modern Supramolecular Gold Chemistry, ed. A. Laguna, Wiley-VCH, Weinheim, 2008, p. 347; (d) A. Laguna and J. M. López-de-Luzuriaga, in Macromolecules Containing Metal and Metal-like Elements, vol. 10: Photophysics and Photochemistry of Metal-Containing Polymers, ed. A. S. Abd-El Aziz, C. E. Carraher Jr., C. U. Pittman Jr. and M. Zeldin, John Wiley & Sons, 2010, p. 326; (e) W. Y. Wong, Coord. Chem. Rev., 2007, 251, 2400; (f ) P. Y. Li, B. Ahrens, K.-H. Choi, M. S. Khan, P. R. Raithby, P. J. Wilson and W.-Y. Wong, CrystEngComm, 2002, 4, 405; (g) W.-Y. Wong, K.-H. Choi, G.-L. Lu and Z. Lin, Organometallics, 2002, 21, 4475; (h) L. Liu, S.-Y. Poon and W.-Y. Wong, J. Organomet. Chem., 2005, 690, 5036; (i) W.-Y. Wong, L. Liu and J.-X. Shi, Angew. Chem., Int. Ed., 2003, 42, 4064. 4 (a) I. O. Koshevoy, Y. C. Chang, A. J. Karttunen, M. Haukka, T. Pakkanen and P. T. Chou, J. Am. Chem. Soc., 2012, 134, 6564; (b) Y. Jiang, Y. T. Wang, Z. G. Ma, Z. H. Li, Q. H. Wei and G. N. Chen, Organometallics, 2013, 32, 4919; (c) J. R. Shakirova, E. U. Grachova, A. S. Melnikov, V. V. Gurzhiy, S. P. Tunki, M. Haukka, T. A. Pakkanen and I. O. Koshevoy, Organometallics, 2013, 32, 4061; (d) E. J. Fernández, A. Laguna, J. M. López-de-Luzuriaga and M. Monge, Spanish Patent P200001391, 2003; (e) E. J. Fernández, J. M. López-de-Luzuriaga, M. Monge, M. E. Olmos, J. Pérez, A. Laguna, A. A. Mohammed and J. P. Fackler Jr., J. Am. Chem. Soc., 2003, 125, 2022; (f ) E. J. Fernández, J. M. López-de-Luzuriaga, M. Monge, M. E. Olmos, R. C. Puelles, A. Laguna, A. A. Mohamed and J. P. Fackler Jr., Inorg. Chem., 2008, 47, 8069; (g) A. Laguna, T. Lasanta, J. M. López-de-Luzuriaga, M. Monge, P. Naumov and M. E. Olmos, J. Am. Chem. Soc., 2010, 132, 456; (h) T. Lasanta, M. E. Olmos, A. Laguna, J. M. López-deLuzuriaga and P. Naumov, J. Am. Chem. Soc., 2011, 133, 16358.

16496 | Dalton Trans., 2014, 43, 16486–16497

Dalton Transactions

5 See for example: C. Silvestru, in Modern Supramolecular Gold Chemistry, ed. A. Laguna, Wiley-VCH, Weinheim, 2008, p. 181 and references therein. 6 E. J. Fernández, J. M. López-de-Luzuriaga, M. Monge, M. A. Rodríguez, O. Crespo, M. C. Gimeno, A. Laguna and P. G. Jones, Chem. – Eur. J., 2000, 6, 636. 7 M. Rodríguez-Castillo, M. Monge, J. M. López-de-Luzuriaga, M. E. Olmos, A. Laguna and F. Mendizabal, Comput. Theor. Chem., 2011, 965, 163. 8 (a) L.-Y. Zou, Y.-X. Cheng, Y. Li, H. Li, H.-X. Zhang and A.-M. Ren, Dalton Trans., 2014, 43, 11252–11259; (b) D. M. Zink, M. Bächle, T. Baumann, M. Nieger, M. Kühn, C. Wang, W. Klopper, U. Monkowius, T. Hofbeck, H. Yersin and S. Bräse, Inorg. Chem., 2013, 52, 2292–2305; (c) J. C. Deaton, S. C. Switalski, D. Y. Kondakov, R. H. Young, T. D. Pawlik, D. J. Giesen, S. B. Harkins, A. J. M. Miller, S. F. Mickenberg and J. C. Peters, J. Am. Chem. Soc., 2010, 132, 9499–9508; (d) H. V. R. Dias, H. V. K. Diyabalanage, M. G. Eldabaja, O. Elbjeirami, M. A. Rawashdeh-Omary and M. A. Omary, J. Am. Chem. Soc., 2005, 127, 7489. 9 (a) P. C. Ford, E. Cariati and J. Bourassa, Chem. Rev., 1999, 99, 3625; (b) D. R. McMillin and K. M. McNett, Chem. Rev., 1998, 98, 1201. 10 (a) E. J. Fernández, A. Laguna, J. M. López-de-Luzuriaga, M. Monge, M. Montiel and M. E. Olmos, Inorg. Chem., 2005, 44, 1163; (b) E. J. Fernández, A. Laguna, J. M. Lópezde-Luzuriaga, M. Monge, M. Montiel, M. E. Olmos and M. Rodríguez-Castillo, Organometallics, 2006, 26, 3639; (c) E. J. Fernández, A. Laguna, J. M. López-de-Luzuriaga, M. Monge, M. Montiel, M. E. Olmos and M. RodríguezCastillo, Dalton Trans., 2009, 7509; (d) J. M. López-deLuzuriaga, M. Monge, M. E. Olmos, D. Pascual and M. Rodríguez-Castillo, Inorg. Chem., 2011, 50, 6910; (e) J. M. López-de-Luzuriaga, M. Monge, M. E. Olmos, D. Pascual and M. Rodríguez-Castillo, Organometallics, 2012, 31, 3720. 11 (a) I. O. Koshevoi, L. Koskinen, M. Haukka, S. P. Tunik, P. Y. Serdobintsev, A. S. Melnikov and T. A. Pakkanen, Angew. Chem., Int. Ed., 2008, 47, 3942; (b) I. O. Koshevoi, Y.-C. Lin, A. J. Karttunen, P.-T. Chou, P. Vainiotalo, S. P. Tunik, M. Haukka and T. A. Pakkanen, Inorg. Chem., 2009, 48, 2094; (c) I. O. Koshevoi, C.-L. Lin, A. J. Karttunen, J. Jänis, M. Haukka, S. P. Tunik, P.-T. Chou and T. A. Pakkanen, Chem. – Eur. J., 2011, 17, 11456; (d) I. S. Krytchankou, D. V. Krupenya, A. J. Karttunen, S. P. Tunik, T. A. Pakkanen, P.-T. Chou and I. O. Koshevoy, Dalton Trans., 2014, 43, 3383; (e) I. O. Koshevoy, Y.-C. Chang, A. J. Karttunen, J. R. Shakirova, J. Jänis, M. Haukka, T. Pakkanen and P.-T. Chou, Chem. – Eur. J., 2013, 19, 5104; (f) J. R. Shakirova, E. V. Grachova, V. V. Gurzhiy, I. O. Koshevoy, A. S. Melnikov, O. V. Sizova, S. P. Tunik and A. Laguna, Dalton Trans., 2012, 41, 2941; (g) J. R. Shakirova, E. V. Grachova, A. A. Melekhova, D. V. Krupenya, V. V. Gurzhiy, A. J. Karttunen, I. O. Koshevoy, A. S. Melnikov and S. P. Tunik, Eur. J. Inorg.

This journal is © The Royal Society of Chemistry 2014

View Article Online

Published on 24 September 2014. Downloaded by Iowa State University on 18/10/2014 04:31:13.

Dalton Transactions

12

13 14 15 16

Chem., 2012, 4048; (h) G. F. Manbeck, W. W. Brennessel, R. A. Stockland Jr. and R. Eisenberg, J. Am. Chem. Soc., 2010, 132, 12307; (i) I. O. Koshevoy, A. J. Karttunen, S. P. Tunik, M. Haukka, S. I. Selivanov, A. S. Melnikov, P. Yu. Serdobintsev, M. A. Khodorkovskiy and T. A. Pakkanen, Inorg. Chem., 2008, 47, 9478; ( j) I. O. Koshevoy, E. S. Smirnova, A. Domenech, A. J. Karttunen, M. Haukka, S. P. Tunik and T. A. Pakkanen, Dalton Trans., 2009, 8392; (k) I. O. Koshevoy, A. J. Karttunen, S. P. Tunik, J. Jaenis, M. Haukka, A. S. Melnikov, P. Yu. Serdobintsev and T. A. Pakkanen, Dalton Trans., 2010, 39, 2676; (l) X. He, N. Zhu and V. W.-W. Yam, Dalton Trans., 2011, 40, 9703; (m) P. Yu. Dereza, I. S. Krytchankou, D. V. Krupenya, V. V. Gurzhiy, I. O. Koshevoy, A. S. Melnikov and S. P. Tunik, Z. Anorg. Allg. Chem., 2013, 639, 398; (n) I. S. Krytchankou, D. V. Krupenya, V. V. Gurzhiy, A. A. Belyaev, A. J. Karttunen, I. O. Koshevoy, A. S. Melnikov and S. P. Tunik, J. Organomet. Chem., 2013, 723, 65. (a) C. E. Strasser and V. J. Catalano, J. Am. Chem. Soc., 2010, 132, 10009; (b) C. E. Strasser and V. J. Catalano, Inorg. Chem., 2011, 50, 11228; (c) K. Chen, C. E. Strasser, J. C. Schmitt, J. Shearer and V. J. Catalano, Inorg. Chem., 2012, 51, 1207; (d) M. J. Calhorda, C. Ceamanos, O. Crespo, M. C. Gimeno, A. Laguna, C. Larraz, P. D. Vaz and M. D. Villacampa, Inorg. Chem., 2010, 49, 8255; (e) O. Crespo, M. C. Gimeno, A. Laguna, C. Larraz and M. D. Villacampa, Chem. – Eur. J., 2007, 13, 235; (f) I. O. Koshevoy, J. R. Shakirova, A. S. Melnikov, M. Haukka, S. P. Tunik and T. A. Pakkanen, Dalton Trans., 2011, 40, 7927; (g) J.-H. Jia, J.-X. Liang, Z. Lei, Z.-X. Cao and Q.-M. Wang, Chem. Commun., 2011, 47, 4739. M. E. Olmos, A. Schier and H. Schmidbaur, Z. Naturforsch., B: Chem. Sci., 1997, 52, 203. D. J. Fife, K. W. Morse and W. M. Moore, J. Photochem., 1984, 24, 249. C. Kutal, Coord. Chem. Rev., 1990, 99, 213. K. Nakamoto, in Infrared and Raman Spectra of Inorganic and Coordination Compounds, John Wiley & Sons, New York, 1986, p. 206.

This journal is © The Royal Society of Chemistry 2014

Paper

17 R. M. Silverstein, F. X. Webster and D. J. Kiemle, in Spectrometric Identification of Organic Compounds, John Wiley & Sons, New York, 7th edn, 2005, p. 107. 18 A. L. Casado and P. Espinet, Organometallics, 1998, 17, 3677. 19 G. R. Newcome and D. C. Hager, J. Org. Chem., 1978, 43, 947. 20 R. Ziessel, Tetrahedron Lett., 1989, 30, 463. 21 SAINT, Bruker AXS Inc., Madison, WI, 2009. 22 G. M. Sheldrick, SADABS, SHELXS-2013, SHELXL-2013, University of Göttingen, Germany, 2013. 23 O. V. Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howard and H. Puschmann, J. Appl. Crystallogr., 2009, 42, 339–341. 24 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, N. J. Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö. Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski and D. J. Fox, Gaussian 09, Revision A.1, Gaussian, Inc., Wallingford CT, 2009. 25 C. Adamo and V. Barone, J. Chem. Phys., 1999, 110, 6158. 26 D. Andrae, U. Haeussermann, M. Dolg, H. Stoll and H. Preuss, Theor. Chim. Acta, 1990, 77, 123. 27 P. Pyykkö, N. Runeberg and F. Mendizabal, Chem. – Eur. J., 1997, 3, 1451. 28 A. Bergner, M. Dolg, W. Küchle, H. Stoll and H. Preuss, Mol. Phys., 1993, 80, 1431. 29 S. Huzinaga, Gaussian Basis Sets for Molecular Calculations, Elsevier, Amsterdam, 1984, p. 16. 30 S. Huzinaga, J. Chem. Phys., 1965, 42, 1293.

Dalton Trans., 2014, 43, 16486–16497 | 16497