Novel copper(I) complexes with extended π⋯π interactions: Synthesis, structure, characterization and spectroscopic properties

Based on ligand N,N′-bis(pyridin-2-ylmethylene)biphenyl-4,4′-diamine (pmbb), two compounds of [Cu2(pmbb)(CH3CN)2(PPh3)2](ClO4)2·2DMF (1) and [Cu2(pmbb) (PPh3)2(Cl)2] (2) have been synthesized and structurally characterized by IR, 1H NMR, 31P NMR and X-ray crystal structure analysis. Structural analysis reveals that both of these complexes contain the 1D embrace arrays, with different variations in π-stacking patterns and intermolecular C–H⋯π interactions. Crystal structure of 1 contains 1D tape-like arrays constructed by C–H⋯π and π⋯π interactions, and the ordered-layer-lattice DMF and ClO4− are located between one-dimensional arrays. For 2, π-stacking interactions lead to the construction of 1D arrays and 2D sheet. The UV–Vis absorption spectra of complexes 1 and 2 reveal that π-stacking types may play an important role in optical absorption. DFT studies indicate the stability may be 2 > 1. In addition, the emission spectrum of complex 1 in acetonitrile solvent and thermogravimetric analysis of 2 are also observed.