Substrate-Binding Reactions of the3[dσ*pσ] Excited State of Binuclear Gold(I) Complexes with Bridging Bis(dicyclohexylphosphino)methane Ligands: Emission and Time-Resolved Absorption Spectroscopic Studies

Abstract

The complexes [Au2(dcpm)2]-Y2 (dcpm = bis(dicyclohexylphosphino)methane; Y=ClO4 (1), PF6- (2), CF3SO3- (3), Au(CN)2- (4), Cl- (5), SCN (6) and I- (7)) were prepared, and the structures of 1 and 4-7 were determined by X-ray crystallography. Complexes 1-4 display intense phosphorescence with lambdamax at 360-368 nm in the solid state at room temperature as well as in glassy solutions at 77 K. The solid-state emission quantum yields of the powdered samples are 0.37 (1), 0.74 (2), 0.53 (3) and 0.12 (4). Crystalline solid 5 displays both high-energy UV (lambdamax = 366 nm) and low-energy visible emissions (lambdamax = 505 nm) at room temperature, whereas either 6 or 7 shows only an intense emission with lambdamax at 465 or 473 nm, respectively. All the complexes in degassed acetonitrile solutions exhibit an intense phosphorescence with lambdamax ranging from 490 to 530 nm. The high-energy UV emission is assigned to the intrinsic emission of the 3[dsigma*psigma] excited state of [Au2(dcpm)2]2+, whereas the visible emission is attributed to the adduct formation of the triplet excited state with the solvent/counterion. The quenching rate constants of the visible emission of [Au2(dcpm)2]2+ in acetonitrile by various anions are 6.08 x 10(5) (ClO4-), 9.18 x l0(5) (PF6 ), 1.55 x 10(7) (Cl-) and 4.06 x 10(9) (I-) mol(-1) dm3s(-1). The triplet-state difference absorption spectra of 1-4 in acetonitrile show an absorption band with lambdamax at 350 nm and a shoulder/absorption maxima at 395-420 nm; their relative intensities are dependent upon the halide ion present in solution. Substrate binding reactions of the 3[dsigma*psigma] excited state with halide (X-) to give [Au2(dcpm)2X]+* would account for the lower energy absorption maxima in the triplet-state difference absorption spectra. With iodide as the counterion, complex 7 undergoes a photoinduced electron-transfer reaction with I- to give the radical anion I2-.

Theoretical studies on metal–metal interaction and luminescence of a dinuclear [AuS2PH2]2 complex

“…s(Au) (metal-centered charge transfer, MCCT) accompanied by d(P) ? s(Au) (ligand to metal charge transfer, LMCT), which agrees with the assignment of the lowest-energy absorptions for the dinuclear Au complexes in theory and experiment [22,46].…”

“…d à r (Au) transition. Our calculated emissions agree well with the experimental observations [22,46] for dinuclear Au complexes and provide more detailed information about the transition properties of phosphorescent emissions. Table 1 Optimized geometry parameters of [AuS 2 PH 2 ] 2 using the MP2 method for the X 1 A g ground state structure and the CIS method for the A 3 A u lowest-energy triplet excited-state structure.…”

Hexa‐ and Octagold Chains from Flexible Tetragold Molecular Units Supported by Linear Tetraphosphine Ligands

“…The former energy is appreciably lower than the d σ* →p σ transition reported for digold(I) complexes with dppm and dcpm (ca. 270–300 nm) 5b,h. A solution of complex 2 c in CH 2 Cl 2 is luminescent with emission band maxima at 509 and 437 nm, which are assigned to the emission from the 3 [ d σ*σ*σ* p σσσ ] and 3 [ d σ*σσ* p σσ*σ ] states respectively,5g based on the MO analysis.…”

A Review of Luminescent Anionic Nano System: d10 Metallocyanide Excimers and Exciplexes in Alkali Halide Hosts

“…Closed-shell heavy metals used to be considered as repelling each other due to the fully occupied valence orbitals. However, in the study of inorganic and organometallic compounds, experimental results have presented evidence of interaction between closed-shell metals [16,17,18,19,20,21,22,23,24,25]. The strength of these bonds is weaker than ionic (700–4000 kJ/mol) and covalent bonds (200–1000 kJ/mol) but stronger than a van der Waals bond (<5 kJ/mol), and they are about the energy of hydrogen bonds (10–40 kJ/mol) [26].…”