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

• A series of new Cu(I) complexes, namely [Cu(dpa)X(PPh3)] and [Cu(dpa)(PPh3)2](BF4) were prepared and characterized.
• Crystal structures of the Cu(I) heteroleptic complexes were presented.
• The Cu(I) complexes are luminescence-tunable depending on the electronic characteristics of the corresponding auxiliary ligands.

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 by 1H NMR, mass spectroscopy and single-crystal X-ray analyses. Their photophysical properties in both CH2Cl2 solution 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.