Radical Elaboration of a Ligand-to-Ligand Charge Transfer Chromophore Yields Emissive Excited State Decay

Spectroscopic and photophysical properties of a radical-substituted ligand-to-ligand charge transfer complex (1-NN) are presented and compared to the parent, diamagnetic complex, 1. Although 1-NN and 1 have identical emission quantum yields, the photoluminescence lifetime of 1-NN is reduced to ∼60% of that observed for 1. This is nominally due to the contribution of additional NN vibrational modes in 1-NN that enhance the competitive nonradiative decay process relative to 1. The observation of photoluminescence in radical-substituted chromophores such as 1-NN points to their potential as highly tunable platforms for the development of new molecular color centers for quantum information science applications.