Synthesis, structures, theoretical studies and luminescent properties of copper(I) complexes with C-Cl⋯π interactions

Abstract

Based on 2-(6-methylpyridin-2-yl)-1H-phenanthro[9,10-d]imidazole (PyPhen), two new copper(I) complexes, [Cu(PPh₃)₂(PyPhen)]BF₄ · CHCl₃ (1) and [Cu(DPEphos)(PyPhen)] BF₄ · 2CHCl₃(2) (PPh₃=triphenylphosphine, DPEphos= bis(2-diphenylphosphinophenyl)ether) have been prepared and characterized by IR, ¹H NMR, ³¹P NMR, SEM and X-ray crystal structure analysis. Structural analysis indicate that each Cu⁺ in 1 and 2 contains a distorted-tetrahedral [Cu(NN)(PP)]⁺moiety, and except inter/intra-molecular CH^…π and π⋯π weak interactions being found in crystal structures, the CCl⋯π interactions between the Cl atoms from CHCl₃ and the adjacent phenyl ring from phosphine ligand (PPh₃ or DPEphos) are observed with the Cl^…π distances of 3.526, 3.721 Å for 1 and 3.399, 3.545 Å for 2. DFT studies demonstrate that the HOMOs in 1 and 2 are mainly composed of copper d-orbital and phosphine ligand, while the LUMOs are primarily related to PyPhen, and the cations of complexes 1 and 2 at methanol, pyridine, dichloromethane and nitrobenzene would have some variation in the HOMO/ LUMO energies, HOMO → LUMO energy gap, Mülliken atomic charges and dipole moments. In addition, the solid-state luminescent properties of complexes 1 and 2 show that the maximum emission decay time and quantum yield reach 193 μs and 2.20 %, respectively.