Tetrahedral copper(I) complexes of novel N,N-bidentate ligands and photophysical properties

A series of copper(I) complexes [Cu(L)(PPh3)(2)]NO3 (1-5) of bidentate ligands 2-pyridin 2 yl quinoline (L1), 4-phenyl-2-pyridin-2-yl quinoline (L2) 2-pyridin-2-yl quinoxaline (L3), 6,7-dimethyl-2-(pyridin-2-yl)quinoxaline (L4), and 4-phenyl-2-pyridin-2-yl-quinazoline (L5) have been synthesized and characterized by elemental analysis, absorption, emission, IR, H-1, C-13, P-31 NMR spectroscopies and redox method. Of these complexes [Cu(L1) (PPh3)(2)]NO3 (1), [Cu(L3)(PPh3)(2)]NO3 (3), and [Cu(L4)(PPh3)(2)]NO3 (4) are structurally characterized by single-crystal X-ray analysis. They exhibited distorted tetrahedral coordination geometries around the copper(I) center with tau(4) values of 0.77-0.86. In the solid-state, all these complexes have exhibited emission in the range of 450-750 nm and their excited-state lifetimes were measured as of 1.9-8.9 mu s. However, all the complexes were found to be weak emissive in solution due to the excited state structural rearrangement. Further, Time-dependent density-functional theory (TDDFT) calculations showed that the charge transfers are mainly caused by the contribution of HOMO-2 -> LUMO, HOMO-1 -> LUMO and HOMO -> LUMO orbitals.

Automated summary

A series of copper(I) complexes have been synthesized and characterized, with some of them structurally analyzed using single-crystal X-ray analysis. These complexes exhibit emission properties in the solid-state, but weak emission in solution. Time-dependent density-functional theory calculations indicate charge transfers mainly occur between specific orbitals.