Synthesis,spectroscopic and electrochemical characterization of copper(I) complexes with functionalized pyrazino[2,3-f]-1,10-phenanthroline

The present work reports the synthesis and spectroscopic and electrochemical characterization of homoleptic copper(I) complexes with substituted pirazino 2,3-f]-1,10-phenanthroline, RpplR′, (R = H, Me, COOH or COOMe, and R′ = H, Me) as ligand. The ligand ppl works as an acceptor of electronic density, which is delocalized mainly in the quinoxaline part of its structure. The UV–Vis spectra show that all the complexes display bands in the range 400–650 nm, which are MLCT in character. The λ_max and extinction coefficients of the MLCT band at 450 nm and the LC band do not change significatively when varying the R substituent. Nevertheless, the intensity of the shoulder around 500 nm does change; this absorption has been related to either a static or dynamic flattening distortion of the complex D_2d → D₂ symmetry. The cyclic voltammetry of the complexes shows irreversible redox processes with E_p values that do not follow the tendency expected from the donor/acceptor character of the substituents on the ligand. All the complexes studied showed no emission both in acetonitrile and dichloromethane as solvent at room temperature and under argon atmosphere.