Sky-blue thermally activated delayed fluorescence (TADF) based on Ag(i) complexes: strong solvation-induced emission enhancement

A new Ag(I) complex based on tris(2-pyridyl)phosphine (Py3P), [Ag-2(Py3P)(3)(SCN)(2)], has been synthesized and chemically characterized. Theoretical calculations and photophysical investigations reveal thermally activated delayed fluorescence (TADF) coupled with outstanding solvato- and vapor-luminescent behavior. The parent complex [Ag-2(Py3P)(3)(SCN)(2)] shows sky-blue TADF (lambda(max) = 469 nm) at ambient temperature with a quantum yield of Phi(PL) = 16% and an emission decay time of 2.2 mu s. Upon exposing the complex to CH2Cl2 or CHCl3 vapors, [Ag-2(Py3P)(3)(SCN)(2)]center dot 0.66CH(2)Cl(2) and [Ag-2(Py3P)(3)(SCN)(2)]center dot CHCl3 solvates are formed. This process is accompanied by a strong enhancement of the luminescence intensity. Both solvates also emit sky-blue TADF (lambda(max) = 478-483 nm), but the emission quantum yield reaches Phi(PL) approximate to 70% at an emission decay time of 9-12 mu s, depending on the solvent. According to DFT/TD-DFT computations, the observed TADF originates from a (1)(M + X)LCT excited state. The experimentally determined Delta E(S-1 - T-1) gap for [Ag-2(Py3P)(3)(SCN)(2)]center dot 0.66CH(2)Cl(2) is relatively large and amounts to 1040 cm(-1) (approximate to 129 meV)