Synthesis, structure, characterization and spectroscopic properties of Cu+ complexes with extended π⋯π interactions

Abstract

A series of Cu(I) complexes, [Cu2(pfan)2(4,4′-bipyridine)(PPh3)2](BF4)2 (1), [Cu2(4,4′-bipyridine)(2,2′-bipyridine)2(PPh3)2](BF4)2 (2), [Cu2(bpe)(2,2′-bipyridine)2(PPh3)2](BF4)2 (3), [Cu2(bpe)(phen)(PPh3)2](BF4)2 (4), [Cu2(bpe)(pfan)2(PPh3)2](BF4)2 (5) (phen=1,10-phenanthroline, bpe=1,2-bis(4-pyridyl)ethylene, pfan=((pyridin-2-yl)formylidene)anilin), have been synthesized and characterized by IR, 1H NMR, 31P NMR, UV–Vis spectrum and X-ray crystal structure analysis. The structural analysis displays that each Cu+ in the complexes is four coordinate N3P, and adopts a distorted-tetrahedral geometry, and 1D chain of 1–5 is formed by four tapes of‘π⋯π interactions between chelating ligands except that 5 is built by π⋯π interaction of phenylene rings from PPh3. All these reveal that the change of chelating or bridging ligand might be the key of construction of 1D π-stacking chain. UV–Vis spectra and DFT studied indicate the absorption spectrum of 4, compared to 3, is red shift. In addition, the emission spectrum of complexes 2, 3 and 4 in acetonitrile are also observed.