Luminescentμ-Ethynediyl andμ-Butadiynediyl Binuclear Gold(I) Complexes:  Observation of³(ππ*) Emissions from Bridging C_n^2-Units

Abstract

The synthesis and X-ray structural and spectroscopic characterization for LAuC triple bond CAuL x 4CHCl(3) and LAuC triple bond C--C triple bond CAuL x 2CH(2)Cl(2) (1 x 4CHCl(3) and 2 x 2CH(2)Cl(2), respectively; L = PCy(3), tricyclohexylphosphine) are reported. The bridging C(n)(2-) units are structurally characterized as acetylene or diacetylene units, with C triple bond C distances of 1.19(1) and 1.199(8) A for 1 x 4CHCl(3) and 2 x 2CH(2)Cl(2), respectively. An important consequence of bonding to Au(I) for the C(n)(2-) moieties is that the lowest-energy electronic excited states, which are essentially acetylenic (3)(pi pi*) in nature, acquire sufficient allowedness via Au spin-orbit coupling to appear prominently in both electronic absorption and emission spectra. The origin lines for both complexes are well-defined and are observed at 331 and 413 nm for 1 and 2, respectively. Sharp vibronic progressions corresponding to v(C triple bond C) are observed in both emission and absorption spectra. The acetylenic (3)(pi pi) excited state of 2 has a long lifetime (tau(0) = 10.8 mus) in dichloromethane at room temperature and is a powerful reductant (E degrees [Au(2)(+)/Au(2)] < or = -1.85 V vs SSCE).

The influence of counter ion and ligandmethyl substitution on the solid-state structures and photophysical properties of mercury(ii) complexes with (E)-N-(pyridin-2-ylmethylidene)arylamines

“…In this context, the luminescent and electroluminescent properties of alkynylmercury complexes and mercury bipyridine complexes have been examined. [24][25][26][27][28] Weak intermolecular d 10 ···d 10 interactions such as Au···Au and Hg···Hg contacts can play an important role in materials science and crystal engineering, [29][30][31][32][33][34][35][36] as their strength is comparable with those exhibited by hydrogen bonds and they are often responsible for the observed optical properties. [37][38][39] The formation of metal···metal and aryl···aryl interactions in the solid-state can cause a red shift in the emission band compared with that in solution phase.…”

Effects of Chain Length and Au Spin‐Orbit Coupling on 3(ππ*) Emission from Bridging Cn2− Units: Theoretical Characterization of Spin‐Forbidden Radiative Transitions in Metal‐Capped One‐Dimensional Carbon Chains [H3PAu(CC)nAuPH3]

“…It should be noted that the X-ray structures of the digold(i) compound indicate a small distortion of the 3.66, and 3.85 eV, respectively, and they reasonably agree with the experimental bands at 331 nm (3.74 eV), 315 nm (3.93 eV), and 303 nm (4.09 eV). [13] As Figure 2 shows, there is an excellent correlation relationship between TD-DFT transition energies and observed bands for the electron excitation to the lowest triplet excited state 3 A 2u , that is, Equation (3) holds in which A = 0.11432 eV, B = 1.0354.…”

“…[13] To estimate the limit of the lowest energy 3 (pp*) adsorption of (CC) / 2À , an exponential-decay curve fitting has been examined on the basis of calculated vertical singlet±triplet transition energies (T e in eV). The exponential-decay fitting gives Equation (4):…”

“…[2] Most recently, the [Cy 3 PAu(CC) n AuPCy 3 ] (n = 1±4) complexes have been synthesized by Che and co-workers. [13] These dinuclear gold(i) complexes bridged by C n 2À show significant spectroscopic features of the triplet 3 (pp*) excited (pp*) emission and adsorption from bridging C n 2À units are assumed to become sufficiently allowed through Au spin-orbit coupling to appear prominently. Such a heavy atom effect has been observed in unsaturated organic species.…”

“…[14] In contrast to the spin-allowed p±p* excitation to the 1 (pp*) excited state, the singlet±triplet excitation energy in the dinuclear gold(i) complexes follows linear relationship between l 2 and n (n = number of alkynyl units), instead of linear dependence of l on 1/n responsible for the singlet±singlet p±p* transition in rhenium-capped polyynediyls. [13] Although it is known that the presence of heavy atoms can enhance the lifetime and emission quantum yield of intraligand triplet-excited states, knowledge of the geometrical and electronic structures of these states as well as fundamental aspects of the spin-orbit coupling is still sparse for such metal-capped wirelike polyynediyl chains. In order to understand the 3 (pp*) emission from C n 2À units, equilibrium geometries of these binuclear gold(i) complexes in their ground states and selected 3 (pp*) excited states have been determined by density functional theory and ab initio electron correlation calculations, respectively.…”