Syntheses and crystal structures of copper and silver complexes with new imine ligands - Air-stable, photoluminescent Cu^IN₄ chromophores

A series of new imine ligands [1 [C₁₂H₁₂N₂S₂), 2 (C₁₂H₁₂N₂S₂), 3 (C₂₄H₁₈N₄S₂), and 5 (C₃₀H₂₇N₇) have been synthesized (1 and 2 are structural isomers). Cu^I and Ag^I complexes of the nonconjugated dithiophene-diimine ligands 1, 2 and the tripodal imine-amine ligand 5 have also been prepared and thoroughly characterized by spectroscopic techniques as well as by X-ray diffraction. In cyclic voltammetry at a glassy carbon milli electrode in anhydrous dichloromethane under dry N2, the corresponding Cu^I complexes [6(2C₁₂H₁₂N₂S₂ ·CuCLO₄), 7 (2C₁₂H₁₂N₂S₂ ·CuCLO₄), and 12 (C₃₀H₂₇N₇·CuCLO₄)] show quasi-reversible Cu^II/I couples with high redox potentials (1.001 V for 6, 0.958 V for 7, and 0.692 V for 12, vs. Ag/AgCl). This indicates that the π-acid ligands 1, 2, and 5 preferentially stabilize copper(I) over copper(II). The Cu^IN₄ chromophores in the complexes 6, 7, and 12 display photoluminescence in dichloromethane at room temperature. The related silver complexes of the same three ligands 10 (2C₁₂H₁₂N₂S₂ ·AgCLO₄), 11 (2C₁₂H₁₂N₂S₂ ·AgCLO₄), and 13 [C₃₀H₂₇N₇·Ag (CH₃CN)CLO₄] reveal similar structural features but lack specific photophysical properties,