Brightly phosphorescent tetranuclear copper(i) pyrazolates.

Described herein is the synthesis and photophysics of two tetranuclear copper complexes, {[3,5-(Pr-i)(2),4-(Br)Pz]Cu}(4) and {[3-(CF3),5-(Bu-t)Pz]Cu}(4) tailor-designed by manipulating the pyrazolyl ring substituents. Unlike their trinuclear analogues, the luminescence of the tetranuclear species is molecular (not supramolecular) in nature with extremely high solid-state quantum yields of similar to 80% at room temperature.