Luminescent triply-bridged dicopper(I) complex possessing 3,5-bis{6-(2,2′-dipyridyl)}pyrazole as a bis-chelating ligand

Abstract

A new triply-bridged dicopper(I) complex, [Cu2(μ-dppm)2(μ-HL)](NO3)2 (1), has been prepared via successive treatment of cupric nitrate trihydrate with bis(diphenylphosphino)methane (dppm) and 3,5-bis{6-(2,2′-dipyridyl)}pyrazole (HL) in 2 : 4 : 1 molar ratio in dichloromethane. X-ray diffraction analysis of 1 reveals that the two Cu(I)s are in highly distorted tetrahedral environments with a distance of 4.2775(10) Å, triply bridged by two dppm ligands and one HL chelate as a bis-bidentate bridging ligand through two bipyridyl moieties. Intermolecular N···H–C hydrogen bonding and π···H–C interactions assemble the [Cu2(μ-dppm)2(μ-HL)]2+ cations into a 3-D supramolecular architecture with extended channels along the b-axis, filled with methanol and anions. Complex 1 shows weak low-energy absorptions at 350–425 nm, tentatively ascribed to Cu(I) to HL metal-to-ligand charge-transfer (MLCT) transition, probably mixed with some ILCT character inside HL. The emission is observed at ambient temperature for 1, both in solution and in the solid state, originating from the MLCT excited states.