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

Abstract

Phosphine)-and (N-heterocyclic carbene)gold(I) derivatives of naphthalene and pyrene are reported, containing one or two gold atoms per hydrocarbon. The new complexes are prepared by arylation of gold(I) substrates by arylboronic acids or aryl pinacolboronate esters in the presence of cesium carbonate. Isolated yields range from 52% to 98%. The boron precursors themselves derive from the parent hydrocarbon, where boron is installed in an iridium-catalyzed reaction, or from the aromatic bromides, which are borylated with palladium catalysis. Most of the new gold(I) complexes are air-and moisture-stable colorless solids; they are characterized by multinuclear NMR and optical spectroscopy, combustion analysis, and high-resolution mass spectrometry. X-ray diffraction crystal structures are reported for seven. Gold binding red-shifts optical absorption profiles, which are characteristic of the aromatic skeleton. All compounds show triplet-state luminescence, and dual singlet and triplet emission occurs in some instances. Phosphorescence persists for milliseconds at 77 K and for hundreds of microseconds at room temperature. The compounds' photophysical characteristics, along with time-dependent density-functional theory calculations, suggest emission from ππ* states of the aromatic core. Triplet-state geometry optimization finds minimal geometric rearrangement upon one-electron promotion from the (singlet) ground state.

Synthesis and Characterization of Gold(I) and Gold(III) Complexes Derived from Benzimidazolin‐2‐ylidene Ligands

“…This development supports the recent resurgence of interest in gold catalyzed reactions [11], which in turn has initiated a search for new gold NHC complexes [12]. Today gold NHC complexes are used as pharmaceuticals [13], in photophysical devices [14], and as catalysts for selected transformations in homogeneous catalysis [15].…”

Constrained Digold(I) Diaryls: Syntheses, Crystal Structures, and Photophysics

“…An earlier study [17] of aurated naphthalenes and pyrenes found that structural differences between optimized triplet (excited state) and singlet (ground state) geometries are minuscule. For 1' and 8', the lowest triplet states consist of intraA C H T U N G T R E N N U N G liA C H T U N G T R E N N U N G gand transitions within the naphthyls.…”

“…[14,15] Our previous work has shown triplet-state emission from naphthyl-and pyrenylgold(I) complexes. [16][17][18] Higher concentrations, both of 1-naphthyl and 1-pyrenyl complexes, enhance triplet luminescence. The long-lived triplet emission shows sharp vibronic structure, instead of the featureless emission often associated with excimers.…”

Synthesis, Characterization and Luminescence of Gold Complexes Bearing an NHC Ligand Based on the Imidazo[1,5‐a]quinolinol Scaffold

“…[7,17,30,31] Despite the high atomic number of gold, the spin-orbit coupling promoted by the gold atom is comparably low and leads to relatively long phosphorescence lifetimes at 77 K, but it is high enough to allow for efficient S 1 -T 1 intersystem crossing. This behaviour can be traced back to the low-lying d orbitals, which are not involved in low-energy electronic transitions.…”