Harnessing Fluorescence versus Phosphorescence Branching Ratio in (Phenyl)_n-Bridged (n = 0–5) Bimetallic Au(I) Complexes

Abstract

We have designed and synthesized a series of Au(I) complexes bearing either an alkynyl−(phenylene) n −diphosphine (A-0−A-3) or a (phenylene) n −diphosphine (B-1−B-5) bridge, among which the effective distance between Au(I) and the center of the emitting ππ* chromophore can be fine-tuned via the insertion of various numbers of phenylene spacers. We then demonstrated for the first time in a systematic manner the decrease of rate constant for S 1 → T 1 intersystem crossing (ISC) k isc as the increase of the effective distance. The results also unambiguously showed that the phosphorescence could be harvested via higher S 0 → S n (n > 1) electronic excitation, followed by fast S n → T m ISC and then the population at T 1 state, bypassing the relatively slow S 1 → T 1 ISC. The results unify a recent report on higher excited-state relaxation dynamics for the late transition metal complexes (J. Am. Chem. Soc. 2012, 134, 7715−7724). The dual, far separated fluorescence and phosphorescence of the titled complexes make feasible the white light generation in a single molecule unit, as successfully demonstrated using complex B-3 as a dopant to fabricate organic light emitting diodes.

Vapochromic Gold(I)–Silver(I) Cluster Protected by Alkynyl and Phosphine Ligands

“…Note that only one of the two nitrogen atoms of the pyrazinyl group were occupied, thus tridentate ligand mdppz only functions as bidentate ligand in 1 . The Au 5 Ag 6 motifs exhibit honeycomb‐like geometry, which is similar to structures previously reported by Koshevoy and Blanco et al In each motif, acetylides adopt the µ 3 bonding mode. Six PhC≡C – groups are connected to the central gold atoms via σ bonds, thus forming three linear PhC≡C–Au–C≡CPh substructures, which are further coordinated to six silver atoms through π bonding (Figure b).…”

“…In some cases, phosphine ligands are also introduced to act as peripheral protecting ligands and to enhance the stability of the structures. By using diphosphine ligands, Koshevoy and co‐workers synthesized a series of heterometallic coinage metal clusters, which have a general structure of an alkynyl–metal core wrapped by a [Au(PPh 2 (C 6 H 4 ) n PPh 2 )] 3 “belt” . Blanco et al reported a series of honeycomb‐like gold–silver aggregates, in which alkynyl ligand PhC≡C – , phosphine ligand PPh 3 , anion CF 3 SO 3 – , and solvent pyridine were found to co‐stabilize the clusters …”

Semi-quantitative assessment of the intersystem crossing rate: an extension of the El-Sayed rule to the emissive transition metal complexes

“…28,29 On this basis, we suspect that the Os-2, Au-1 and Au-2 complexes, which we find to have negligible SOC integrals between S 1 and triplet states, although not previously reported, shall also show excitation-dependent phosphorescence quantum yield. Similar to Os-1 and Os-2, Os-6 to Os-9 complexes all exhibit a dominant pp* character in S 1 , giving rise to almost zero SOC integrals with triplet excited states and therefore a slow ISC.…”

“…29 Our results and formulism thus serve as a prototype to access the photophysics of TM complexes in a way analogous to El-Sayed's rule for the classic organic systems, which should be of great benefit to the chemistry and material researchers in the field relevant to optoelectronics. The results also echo the recent experimental progress in that S n -T m ISC can be facilitated in the higher excited states once the above criteria are critically matched so that the rate of ISC can even compete with the rate of internal conversion in the condensed phase.…”

Solvatochromic dual luminescence of Eu–Au dyads decorated with chromophore phosphines

“…27b,d One possible nonradiative process might be a partial population of the triplet state T 1 via relatively slow intersystem crossing (S 1 → T 1 ) due to a heavy atom effect induced by a gold ion. 5e, 35 The absence of phosphorescence under ambient conditions can be explained by weak spin-orbit coupling in the excited state, insufficient for promoting the T 1 → S 0 radiative relaxation.…”