Sensitization of Naphthalene Monomer Phosphorescence in a Sandwich Adduct with an Electron-Poor Trinuclear Silver(I) Pyrazolate Complex

Facial complexation of naphthalene to {[3,5-(CF3)2Pz]Ag}3 (Ag3) gives rise to a stacked binary adduct (1) that exhibits phosphorescence corresponding to T1 monomer emission of naphthalene. Crystals and powders of 1 exhibit bright-green phosphorescence at room temperature with a 830 μs lifetime, whereas cooling to cryogenic temperatures increases the intensity, lifetime, and vibronic resolution. The binary adduct exhibits a drastically shorter phosphorescence lifetime of 6.7 ms versus free naphthalene (2.4 s) in a frozen dichloromethane matrix, which results from the external heavy-atom effect of silver. Adduct 1 represents a new class of phosphors containing lighter but more benign silver than mercury atoms in trinuclear d10 π-acid complexes as arene triplet sensitizers.