Synthesis, structural characterization and photophysical studies of luminescent Cu(I) heteroleptic complexes based on dipyridylamine

Neutral mononuclear Cu(I) complexes based on 2,2′-dipyridylamine (dpa), formulated as [Cu(dpa)X(PPh3)] (X = Cl (A4), Br (A5), I (A6)), monocationic mononuclear Cu(I) complexes with counterion BF4-, i.e. [Cu(dpa)(PPh3)2](BF4) (A1), Cu(dpa)(DPEphos)(BF4) (A2) and [Cu(dpa)(Binap)](BF4) (A3), where DPEphos = bis [2-(diphenylphosphino) phenyl] ether, Binap = 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl, have been prepared and characterized by1H NMR, mass spectroscopy and single-crystal X-ray analyses. Their photophysical properties in both CH2Cl2solution and PMMA (poly(methyl methacrylate)) film have been investigated. All the complexes display a typical metal-to-ligand charge transfer absorption band in the region of 350-400 nm, and a broad and featureless luminescence at room temperature. Specifically, their emission maxima vary from 494 to 562 nm in the PMMA films due to the different electronic characteristics of the auxiliary ligands. Additionally, the thermogravimetric analysis shows that those complexes chelated with diphosphine ligands have a higher thermal stability than those with triphenylphosphine or halides ligands.