Luminescent Characterization of Solution Oligomerization Process Mediated Gold−Gold Interactions. DFT Calculations on [Au₂Ag₂R₄L₂]_nMoieties

Abstract

The optical properties of [Au 2 Ag 2 (C 6 F 5 ) 4 (OCMe 2 ) 2 ] n (1) have been studied in the solid state at room temperature and at 77 K and in acetone solution (5 × 10 -4 M). The crystal structure of 1, analyzed by X-ray diffraction, consists of polymeric chains formed by repetition of Au 2 Ag 2 moieties linked through short gold-gold interactions. The emission profile observed for 1 in dilute acetone solution (5 × 10 -4 M) is assignable to pentafluorophenyl localized ππ* excited states or from π-MMCT transitions, and in the solid-state arises from metal-centered (dσ*) 1 (pσ) 1 or (dδ*) 1 (pσ) 1 excited states. When the absorption and emission spectra of compound 1 in acetone are registered at different concentrations, they display a band that does not obey the Lambert-Beer law. This deviation is consistent with molecular aggregation in solution through gold-gold interactions, and a clear correlation between the emission wavelength and the structure of 1 in the solid state and in solution is shown. DFT calculations accord with the observed experimental behavior and show the nature of the orbitals involved in each transition.

Synthesis and Characterization of a Series of New Luminescent NHC‐Coordinated AuI–AgI Tetra‐ and Polymetallic Complexes Containing Benzoate‐Bridged Ag2 Dimers

“…Fernández et al [3] very thoroughly examined the origin of the photophysical properties of Au 2 (C 6 F 5 ) 4 Ag 2 (OCMe 2 ) 2 . At high concentrations and in the solid state the emission of this species originates from the aurophilic Au···Au intermolecular interactions; however, in dilute solution, the emission appears to arise from either ππ* or π-MMLCT excited state.…”

“…It is well established [1][2][3] that closed-shell, d 10 metal ions often exhibit attractive interactions. These interactions, although weaker than ionic bonds, are stronger than simple van der Waals interactions.…”

“…[15] One such species is derived from the precursor 1-methyl-3-(2-pyridinyl)-1H-imidazolium hexafluorophosphate, [H(CH 3 impy)]PF 6 . It was observed [15b] (Scheme 1) before that the Au complex of this ligand, when treated with AgBF 4 in presence of a nitrile solvent such as CH 3 CN, produced polymeric species {[AuAg(CH 3 impy) 2 (S)](BF 4 ) 2 } n , where S stands for solvent. In these mixed-metal, one-dimensional polymers, the Au I centers are bonded to two carbene moieties, and the Ag I centers are coordinated to two alternating pyridyl groups and a solvent molecule.…”

Luminescence in Polymetallic Gold‐Heteronuclear Derivatives

“…For example, the reaction between NBu 4 [Au(C 6 F 5 ) 2 ] and AgClO 4 in acetone leads to a heterometallic extended linear chain of formula [Au 2 Ag 2 (C 6 F 5 ) 4 (Me 2 CO) 2 ] n . 38 Its crystal structure consists of an extended polymeric chain of tetranuclear Au 2 Ag 2 units formed through short gold-gold contacts of 3.1674(11) Å (Fig. 6).…”

“…9). 38,41 Although, the anionic nature of this gold precursor could be the origin of its donor characteristics, our research group has found that the presence of only one perhaplophenyl group in the gold precursor produces similar potential in their reactions with silver salts. For instance, the neutral species [AuR(tht)] (R 5 C 6 F 5 , 3,5-C 6 Cl 2 F 3 , C 6 Cl 5 ) have been investigated in their reactions with silver trifluoroacetate.…”