Photophysics and Bonding in Neutral Gold(I) Organometallic Complexes with an Extended Aurophilic Supramolecular Structure

Abstract

This work represents a synergistic experimental/computational study of the molecular spectroscopy and bonding in Au(CO)Cl in solution and the solid state. The luminescence behavior for crystalline solids is similar for Au(CO)Cl and related (RNC)AuCl complexes that likewise stack in infinite chains, and both exhibit orange-red unstructured phosphorescence bands with extremely large Stokes shifts ((15−20) × 103 cm-1). The long aurophilic distances computed for the ground state (∼3.2 Å) are contracted in the phosphorescent excited state (∼2.6 Å), demonstrating excimeric Au−Au covalent bonds. The spectral data suggest phosphorescent species in which the excimeric Au−Au bonding is extended beyond two adjacent molecules in the solid state. Controlling the concentration in frozen solutions attains phosphorescent bands due to dimeric species for which the emission energies are higher (in the blue region) than those for crystalline solids and are reproduced by ab initio calculations. The spectral findings herein suggest that predictive information about the supramolecular structure may be obtained by the luminescnce behavior. This is exemplified by crystals of (1,1,3,3-Me4BuNC)AuCl, whose red-orange luminsecence anticipated an extended-chain supramolecular structure, which was later verified crystallographically, as the molecules were found to pack in zigzag chains with alternating short (3.418 Å) and long (4.433 Å) aurophilic distances. Solutions of Au(CO)Cl exhibit negative deviation from Beer's law for, higher-energy monomer bands with the appearance of lower-energy bands at high concentrations due to the dimerization of molecules. Time-dependent density-functional theory (TD-DFT) calculations for monomer and dimer models show good agreement with the experimental spectra and account for the major absorption bands. Ab initio calculations (CCSD(T)/cc-pVTZ) show a blue shift of ∼23 cm-1 in the νC ⋮ O frequency upon complexation, thus providing the first computational evidence of this anomalous blue shift known experimentally for Au(CO)Cl.

Mono- and Di-Gold(I) Naphthalenes and Pyrenes: Syntheses, Crystal Structures, and Photophysics

“…76,77 The optimized parameters are similar to those stated elsewhere for (phosphine)gold(I) and organogold(I) complexes. [78][79][80][81][82][83][84] Figure 6 depicts a frontier-orbital energy level diagram for digold model complex 6 0 in C 2h symmetry. Plots of selected orbitals appear at right.…”

Gold(I) Complexes Bearing P∩N-Ligands: An Unprecedented Twelve-membered Ring Structure Stabilized by Aurophilic Interactions

“…This interpretation was confirmed by Omary and co-workers, who investigated the luminescence of RNC-Au-Cl complexes in the solid state. The covalent Au-Au bonding in the excited state and the weak aurophilic Au ··· Au contact in the ground state explain the large excitedstate distortion [4]. This means that the emissive state is an Au-Au bonded excited state formed upon photoexcitation, similar to organic excimers.…”

“…If bidentate ligands are involved, the formation of rings (instead of polymers) is also possible, and aurophilic contacts can determine 0932-0776 / 09 / 1200-1513 $ 06.00 c 2009 Verlag der Zeitschrift für Naturforschung, Tübingen · http://znaturforsch.com the favored structure. Furthermore, these aurophilic interactions frequently give rise to phosphorescence in the solid state [3,4] and in special cases also in solution. Still, there is no clear relationship established between the luminescence properties and the crystallographic Au ··· Au distances [5].…”

“…Still, there is no clear relationship established between the luminescence properties and the crystallographic Au ··· Au distances [5]. Recently, Omary et al pointed out that the solid-state phosphorescence energy is more determined by the supramolecular arrangement of the Au(I) complexes than by the shortest Au ··· Au distances [4]. Some of these highly emissive Au(I) complexes havew been used for the fabrication of organic light-emitting devices (OLEDs) [6,7].…”

Arylgold(I) Complexes from Base-Assisted Transmetalation: Structures, NMR Properties, and Density-Functional Theory Calculations

“…Yield: 71 mg (88%). 1 IPrAu(mesityl) (11). A flask was loaded with IPrAuBr (63 mg, 0.095 mmol), mesitylboronic acid (57 mg, 0.35 mmol), and Cs 2 CO 3 (108 mg, 0.35 mmol).…”