Crystallographic and Computational Studies of Luminescent, Binuclear Gold(I) Complexes, AuI2(Ph2P(CH2)nPPh2)2I2 (n = 3–6)

Molecular Flexibility in Solvated Crystals of the Dimer, Au2(μ-1,2-bis(diphenylphosphino)ethane)2I2, with Three-Coordinate Gold(I)

We report the ability to trap the dimer Au2(μ-dppe)2I2 (dppe is 1,2-bis(diphenylphosphino)ethane) with different separations between the three-coordinate gold ions in crystalline solvates. All of these solvates ((Au2(μ-dppe)2I2·4(CH2Cl2) (1), Au2(μ-dppe)2I2·2(CH2Cl2) (2), the polymorphs α-Au2(μ-dppe)2I2·2(HC(O)NMe2) (3) and β-Au2(μ-dppe)2I2·2(HC(O)NMe2) (4), and Au2(μ-dppe)2I2·4(CHCl3) (5)) along with polymeric {Au(μ-dppe)I}n·n(CHCl3) (6)) originated from the same reaction, only the solvent system used for crystallization differed. In the different solvates of Au2(μ-dppe)2I2, the Au···Au separation varied from 3.192(1) to 3.7866(3) Å. Computational studies undertaken to understand the flexible nature of these dimers indicated that the structural differences were primarily a result of crystal packing effects with aurophillic interactions having a minimal effect.

Structure and Luminescence Studies of Salts of the Helical Dication, [Au2(μ-bis(diphenylphosphine)ethane)2]2+ and Comparison with Salts of [Au2(μ-bis(diphenylphosphine)propane)2]2

Six salts ([Au2(μ-dppe)2](BF4)2·CHCl3, [Au2(μ-dppe)2](BF4)2·1,2-Cl2C2H4, [Au2(μ-dppe)2](PF6)2·CHCl3, [Au2(μ-dppe)2](PF6)2, [Au2(μ-dppe)2](SbF6)2, and [Au2(μ-dppe)2](OTf)2·2CHCl3), (dppe is bis(diphenylphosphine)ethane) containing the dication, [Au2(μ-dppe)2]2+, have been prepared and structurally characterized by single-crystal X-ray crystallography. Unlike the three-coordinate dppe-bridged dimers, Au2X2(μ-dppe)2 (X = Br, I), which show considerable variation in the distance between the gold(I) ions over the range 3.0995(10) to 3.8479(3) Å in various solvates, the structure of the helical dication, [Au2(μ-dppe)2], in the new salts is remarkably consistent with the Au···Au separation falling in the narrow range 2.8787(9) to 2.9593(5) Å. In the solid state, the six crystals display a green luminescence both at room temperature and at 77 K, which has been assigned as phosphorescence. However, solutions of the dication are not luminescent. Salts containing the analogous dication [Au2(μ-dppp)2](PF6)2 (dppp is bis(diphenylphosphine)propane) have been prepared to determine whether the longer bridging ligand might also twist into a helical shape. These salts include [Au2(μ-dppp)2](OTf)2 (OTf is triflate) and three crystalline forms of [Au2(μ-dppp)2](PF6)2: the solvate [Au2(μ-dppp)2](PF6)2·(CHCl3) and two polymorphs of the unsolvated salt. None of these crystals are luminescent, but all contain a similar dication, [Au2(μ-dppp)2]2+, that contains two nearly parallel, linear P-Au-P groups and a long separation between the gold ions that varies from 5.3409(4) to 5.6613(6)Å.

Aurophilic Interactions of Dimeric Bisphosphine Gold(I) Complexes Pre-Organized by the Structure of the 1,5-Diaza-3,7-Diphosphacyclooctanes

The dimeric gold(I) chloride and gold(I) iodide complexes ([L2Au]Cl2 and L2AuI2) on the scaffold of the cyclic bisphosphine, namely 1,5-diaza-3,7-diphosphacyclooctane containing α-phenylbenzyl (benzhydryl) substituents at the nitrogen atoms, were synthesized. The obtained complexes were isolated as white crystalline powders. The single crystal XRD of the obtained complexes revealed the strong aurophilic interactions between two gold(I) atoms with the Au…Au distance values of 2.9977(6) and 3.1680(5) Å. The comparison of the gold complexes, based on the N,N-diaryl- and N,N-dibenzhydryl substituted 1,5-diaza-3,7-diphosphacyclooctanes, allowed to reveal the strong impact of the initial heterocycle conformation on the realization of the aurophilic interactions, where the geometry of N,N-dibenzhydryl substituted 1,5-diaza-3,7-diphosphacyclooctane, is pre-organized for the intramolecular aurophilic interactions of the complexes. The obtained complexes exhibit a bluish-green phosphorescence (λem 505 (-Cl) and 530(-I)) in the solid state at room temperature, originated by the metal-halide centered transitions, which was confirmed by the TDDFT calculations. It was found that the aurophilic interactions are realized in the ground and in the triplet excited states of the complexes. The slighter change of the geometry of the N,N-dibenzhydryl substituted gold(I) iodide complexes, under the transition from the ground state to the excited state, in comparison with their N,N-diaryl substituted analogues, results in the reduced values of the Stokes shift of luminescence (ca. 150 nm vs. 175 nm).

A neutral vicinal silylene/phosphane supported six-membered C2PSiAu2 ring and a silver(i) complex

We report on the hybrid bidentate silylene and phosphane ligand (1) stabilized Au which are capable of forming a gold containing six-membered ring (2). 2 exhibits an intramolecular aurophilic interaction, which is supported by DFT calculations.

Selective formation of a supramolecular coordination complex in the nanometre scale with a ferrocene-based phospholane ligand

A straightforward synthesis of the tetradentate phospholane ligand 1 is reported. The 2 : 1 [M : L] reaction of 1 with [AuCl(tht)] (tht = tetrahydrothiophene) resulted in the 4 : 2 [M : L] supramolecular coordination complex 2 where two ligands 1 are bridging four gold(I) cations. The formation of 2 can be rationalised via a geometrical analysis of the ligand. The coordination mode of the gold atoms was evaluated based on a CSD search, revealing the geometrical changes for a transition from linear to trigonal planar coordination environment.

Utilization of a Nonemissive Triphosphine Ligand to Construct a Luminescent Gold(I)-Box That Undergoes Mechanochromic Collapse into a Helical Complex

Luminescent gold(I) complexes ([Au₆(Triphos)₄Cl](PF₆)₅·2(CH₃C₆H₅), [Au₆(Triphos)₄Cl](AsF₆)₅·8(CH₃C₆H₅), and [Au₆(Triphos)₄Cl](SbF₆)₅·7(CH₃C₆H₅) where Triphos = bis(2-diphenylphosphinoethyl)phenylphosphine) with a boxlike architecture have been prepared and crystallographically characterized. A chloride ion resides at the center of the box with two of the six gold(I) ions nearby. Mechanical grinding of blue luminescent crystals containing the cation, [Au₆(Triphos)₄Cl]⁵⁺, results in their conversion into amorphous solids with green emission that contain the bridged helicate cation, [μ-Cl{Au₃(Triphos)₂}₂]⁵⁺. A mechanism of the mechanochromic transformation is proposed. The structures of the blue-emitting helicate, [Au₃(Triphos)₂](CF₃SO₃)₃·4(CH₃C₆H₅)·H₂O, and the green-emitting bridged-helicate, [μ-Cl{Au₃(Triphos)₂}₂](PF₆)₅·3CH₃OH have been determined by single crystal X-ray diffraction.

Photoinduced single-crystal-to-single-crystal phase transition and photosalient effect of a gold(i) isocyanide complex with shortening of intermolecular aurophilic bonds

We report the first photoinduced single-crystal-to-single-crystal (SCSC) phase transition of a gold complex that involves the shortening of intermolecular aurophilic bonds. This is also the first solid state photochromism of a gold complex. Upon UV irradiation, the blue-emitting crystals of the gold(i) isocyanide complex 1 (1B) transform into the weakly yellow-emitting polymorph 1Y. X-ray diffraction analyses reveal that this phase transition proceeds in an SCSC manner. After phase transition from 1B to 1Y, the intermolecular Au···Au separation decreases from 3.5041(14) to 3.2955(6) Å, resulting in a red-shifted emission. The photoinduced shortening of the aurophilic bond in the excited state initiates the change in the crystal structure from 1B to 1Y. Moreover, the crystal 1B showed a photosalient effect: the 1B crystals jump upon irradiation with strong UV light owing to the phase transition into 1Y. The aurophilic bond formation in the crystal generates the mechanical movement of the crystal.

Selective formation of gold(I) bis-phospholane macrocycles, polymeric chains, and nanotubes

A series of highly flexible bis-phospholane ligands 3a-g with 5-11 methylene groups in the backbone was synthesized and fully characterized by mass spectrometry and NMR ((1)H, (13)C, (31)P) and IR spectroscopy. Gold bis-phospholane macrocycles containing 16 ([Au2Cl2(μ-3a)2], 4), 20 ([Au2Cl2(μ-3c)2], 5), 24 ([Au2Cl(μ-3e)2]Cl, 6), and 28 ([Au2Cl2(μ-3g)2], 7) atoms in the ring were obtained in one step from [AuCl(tht)] (tht = tetrahydrothiophene) and 3a,c,e,g in excellent yield. In addition, three polymers resulting from aurophilic interactions, i.e., zigzag chains in [Au2Cl2(μ-3b)]x (8) and nanotubes in [Au2Cl2(μ-3d)]x (9) and [Au2Cl2(μ-3f)]x (10), with Au···Au distances of 309.41(2), 330.24(6), and 335.82(3) pm, respectively, were obtained. Halide abstraction of 4-7 with AgBF4 led to macrocycles [Au2(μ-3a)2](BF4)2 (11), [Au2(μ-3c)2](BF4)2 (12), [Au2(μ-3e)2](BF4)2 (13), and [Au2(μ-3g)2](BF4)2 (14). In 12, the monomers are connected by strong aurophilic interactions (Au···Au 296.57(1) pm) in the solid state with formation of a polymeric chain. All complexes were fully characterized by NMR ((1)H, (13)C, (31)P) and IR spectroscopy, mass spectrometry, and X-ray diffraction.