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Keywords:

  • Copper;
  • N ligands;
  • Electronic structure;
  • Structure elucidation

Abstract

A group of bis(aryl)acenaphthenequinonediimine (Ar-BIAN) ligands were synthesized through a modified procedure, which bypasses the need for absolutely dry conditions during the initial template synthesis. The molecular and electronic structure of the corresponding homoleptic [Cu(Ar-BIAN)2]BF4 complexes were probed by means of a variety of spectroscopic methods. In accord with solution 13C NMR spectra, X-ray crystallography reveals D2 or approximate D2 symmetry for the [Cu(p-Cl-BIAN)2]+ and [Cu(p-Me-BIAN)2]+ cations and noncrystallographic C2 symmetry for the [Cu(o-Ph-BIAN)2]+ cation. The structures of the p-Cl-, p-Me, and o-Ph-BIAN complexes agree with the presence of ligands in their neutral form according to the lengths of the relevant C–C and C=N bonds of the organic skeleton. The concerted stereo–electronic effects of the substituents on the aryl rings affect the electron donor/acceptor capacities of the ligands and the structures of the complexes, as the study of the visible absorption spectra of the complexes indicates. The spectra of the complexes are dominated by intense and broad metal-to-ligand charge transfer (MLCT) bands that enter the near-infrared (NIR) region. Additionally, electrochemical studies undertaken reveal several successive electron capture and release processes, which further manifest the redox versatility of the ligands.