Abstract
The photophysical properties of a series of T‐shaped coinage d 10 metal complexes, supported by a bis(mesoionic carbene)carbazolide (CNC) pincer ligand, are explored. The series includes a rare new example of a tridentate T‐shaped AgI complex. Post‐complexation modification of the AuI complex provides access to a linear cationic AuI complex following ligand alkylation, or the first example of a cationic square planar AuIII−F complex from electrophilic attack on the metal centre. Emissions ranging from blue (CuI) to orange (AgI) are obtained, with variable contributions of thermally‐dependent fluorescence and phosphorescence to the observed photoluminescence. Green emissions are observed for all three gold complexes (neutral T‐shaped AuI, cationic linear AuI and square planar cationic AuIII). The higher quantum yield and longer decay lifetime of the linear gold(I) complex are indicative of increased phosphorescence contribution.
Highlights
The photophysical properties of a series of Tshaped coinage d10 metal complexes, supported by a bis(mesoionic carbene)carbazolide (CNC) pincer ligand, are explored
One of the more successful design strategies on this front employs the linear bonding geometry of carbene-metal-amides (CMAs), in which all three d10 metals (CuI, AgI and AuI), have accomplished excellent external quantum efficiencies (EQE) performance and/or high brightness organic light emitting devices (OLEDs) operation, notably employing carbazolide derivatives as the donor amide partners with the acceptor carbenes.[5]. These CMAs can display short emission lifetimes in thermally assisted delayed fluorescence (TADF), based on the rapid triplet-to-singlet intersystem crossing (ISC), unlike the heavy atom phosphorescent emitters relying on spinorbit coupling.[1b,6]
The dependency of photoluminescence on the coordination geometry of d10 coinage metal complexes is well-known,[7] for example, 3-coordinate trigonal planar copper(I) complexes showed tunable behavior from pure phosphorescence to TADF depending on the carbene-metal-amine dihedral angles.[7c]. Extending 3-coordinate systems beyond trigonal planar geometries to a ground state Jahn Teller-distorted T-shape has been an early theoretical target for photophysical tuning of the singlet-triplet gap.[8]
Summary
The photophysical properties of a series of Tshaped coinage d10 metal complexes, supported by a bis(mesoionic carbene)carbazolide (CNC) pincer ligand, are explored. The potential for the AuI/III couple was determined to be E0 = À0.39 V, and at least quasi-reversible with EpaÀEpc = 97 mV to confirm viability of mild chemical oxidation, in line with quantum theoretical studies.[17] 5 was prepared by in situ deprotonation of [H3CNC]PF6·Cl and metalation to yield, after purification and isolation, complex 3 (Scheme 1).
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