Near-infrared emitting copper(I) complexes with a pyrazolylpyrimidine ligand: exploring relaxation pathways.

Mononuclear copper(I) complexes [CuL]I (1), [CuL][CuI]·2MeCN (2) and [CuL]PF (3) with a new chelating pyrazolylpyrimidine ligand, 2-(3,5-dimethyl-1-pyrazol-1-yl)-4,6-diphenylpyrimidine (L), were synthesized. In the structures of complex cations [CuL], Cu ions coordinate two L molecules (,-chelating coordination). Extended π-systems of the L molecules in [CuL] favor the formation of paired π-π stacking intramolecular interactions between the pyrimidine and phenyl rings leading to significant distortions of tetrahedral coordination cores, CuN.