Synthesis, structural variation, photophysical, electrochemical and DFT studies of CuX (X = I, Br and Cl) mixed ligand complexes of an azino-pyridyl ligand and triphenylphosphine

Abstract

Three new copper(I) coordination oligomers [Cu2(L)2(µ-I)2)(PPh3)2]2 (1), [Cu2(µ-L) (µ-Br)2(PPh3)2·CH2Cl2]∞ (2. CH2Cl2) and [Cu2(µ-L)(µ-Cl)2(PPh3)2]∞ (3) have been synthesized by reactions of equimolar CuX (X=I, Br and Cl), PPh3 and the polydentate azino-pyridyl ligand L. These complexes have been characterized by elemental analyses, IR, UV–Vis and NMR spectroscopy. The crystal structures of the complexes 1 and 2. CH2Cl2 have been determined by single-crystal X-ray analysis and it has been found that complex 1 is a dimer with -{CuI-(µ-I2)-CuI}- rhomboid core whereas complex 2. CH2Cl2 is a 1-D co-ordination polymer containing bridged Br−1 ion as well as the ligand L. Matching of X-ray powder pattern of 3 with the simulated powder data obtained from the single crystal of 2. CH2Cl2, and DFT studies reveal that the complex 3 is also a 1-D co-ordination polymer like complex 2. CH2Cl2. At room temperature in dichloromethane the ligand L is non-emissive whereas the complexes 1, 2 and 3 are photoluminescent. The E1/2 values of the CuI-CuII couple of 1, 2 and 3 are 1.06V, 0.85V and 0.81V (vs. Ag/AgCl in 1MKCl, scan rate 100mVs−1) respectively. DFT and Hirshfeld surfaces computational studies have also been performed for 1, 2 and 3.