Bidentate and Tetradentate β-Aminovinyl Trifluoromethylated Ketones and Their Copper(II) Complexes: Synthesis, Characterization and Redox Chemistry

Graphical Abstract

Structural variation of the trifluoromethylated enaminone building block gave rise to new bidentate and tetradentate ligands that bear redox-active units (anthracene, azobenzene and tetrathiafulvalene). Their coordination chemistry with copper(II), structural characterization, redox chemistry and UV/Vis properties of the ligands and complexes have been investigated.

Abstract

New polyfunctional bidentate and tetradentate trifluoromethylated enaminone ligands that bear redox-active and photosensitive moieties were synthesized in moderate to good yields and their coordination chemistry with copper(II) was examined. The crystal structures revealed the formation of mononuclear Cu^II complexes with all ligands, where the metal ion is located in almost perfect to distorted square planar environments. The deviation from an ideal square plane influences the redox potentials of the metal centre within the complex as demonstrated by cyclic voltammetry. For all the complexes, a stable Cu^I species was evidenced by a quasireversible reduction step at potentials from –0.48 to –1.08 V (potential standards E⁰), but the most stable Cu^I species originated from the Cu^II complex with the tetradentate ligand. UV/Vis absorption spectra revealed no major differences between the ligands and their Cu^II complexes.