Luminescent agostic Cu(I) complexes containing both trigonal planar and tetrahedral coordination modes

Abstract

Reaction of [Cu(MeCN)4]ClO4 with 1H-imidazo[4,5-f][1,10]phenanthroline derivatives (L1, L2 and L3) and the bulky, rigid chelating diphosphine ligand 9,9-dimethyl-4,5-bis(diphenylphosphino)-9H-xanthene (xantphos) under alkaline conditions in different ratios afforded a series of luminescent binuclear [Cu2(L–H)(xantphos)2]ClO4 (L=L1, 1a; L2, 2a; L3, 3a) and trinuclear [Cu3(L–2H)(xantphos)3]ClO4 (L=L1, 1b; L2, 2b; L3, 3b) complexes. Both trigonal planar and tetrahedral coordination modes of Cu(I) centers were observed for complexes 1a and 1b, and they exhibit obvious CH⋯Cu agostic or anagostic interaction for the trigonal planar Cu(I) centers. The 31P NMR, electronic absorption and emission spectra are discussed. All the complexes exhibit weak luminescence at room temperature in the solid state and in the solution.