Ag(i) complex design affording intense phosphorescence with a landmark lifetime of over 100 milliseconds

A highly emissive Ag(i) complex comprising 2,9-dimethyl-1,10-phenanthroline (dmp) and bis[(2-diphenylphosphino)phenyl] ether (dpep) ligands was synthesized, characterized and investigated for its photophysical properties both experimentally and theoretically. The material exhibits intense phosphorescence from the triplet state of ligand centered (3LC) character featuring an unprecedented long lifetime of τ = 110 ms and a quantum yield of ΦPL = 50%, as measured for a doped PMMA matrix under ambient conditions. This is an efficient yet exceptionally slow emission decay, breaking the previous record by several orders of magnitude. Such properties are attributed to two factors: (i) the Ag(i) ion introduces weak spin-orbit coupling and efficient population of the emitting triplet state; (ii) the rigid molecular design combined with a matrix-based rigidity largely suppresses non-radiative relaxations.