title: Effect of Geometrical Distortion on the Electronic Structure: Synthesis and Characterization of Monoradical-Coordinated Mononuclear Cu(II) Complexes.
abstract: Ligand H3Sami(Mixed(tBu)) was composed of two different compartments, a redox-active 2-aminophenol and a salen salicylidene. Both compartments were linked via a benzyl linker. The ligand reacted with CuCl2·2H2O under air in the presence of Et3N and provided the corresponding monoradical-coordinated mononuclear Cu(II) complex (1). Complex 1, in solution, reacted with air and provided complex 2 via ligand-centered oxygenation at the benzyl-CH2 position. Both complexes were characterized via IR, mass spectrometry, X-ray single-crystal diffraction, variable-temperature magnetic susceptibility, cyclic voltammograms (CVs), and UV-vis/NIR spectroscopic techniques. X-ray crystallographic analyses clearly showed almost equally distorted square planar geometry around the Cu(II) atom in both complexes. However, the bending of the radical-containing C6 ring compared to the N1-Cu1-O1 plane was different in both complexes. While complex 1 was paramagnetic and showed a ferromagnetic coupling between the d(x(2)-y(2)) magnetic orbital of Cu(II) ion and the p(z) orbital of coordinated π-radical, complex 2 was diamagnetic by experiencing a strong antiferromagnetic coupling between the two magnetic orbitals. UV-vis/NIR spectra of the complexes were dominated by charge-transfer transitions. CVs of the complexes showed two reversible one-electron oxidations and one reversible one-electron reduction. E(1/2)(ox2) and E(1/2)(red1) potentials were different in both complexes, while E(1/2)(ox1) values were almost the same and the process corresponded to the formation of phenoxyl radical. Theoretical studies were also performed to understand the magnetic coupling phenomena, and TD-DFT calculations were employed for the assignment of charge-transfer absorption bands.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati, 781039 Assam, India.
authors.forename: Samir
authors.initials: S
authors.lastname: Ghorai
authors.affiliation: Department of Chemistry, Birla Institute of Technology and Science (BITS) , Pilani, 333031 Rajasthan, India.
authors.forename: Amrit
authors.initials: A
authors.lastname: Sarmah
authors.affiliation: Department of Chemistry, Birla Institute of Technology and Science (BITS) , Pilani, 333031 Rajasthan, India.
authors.forename: Ram Kinkar
authors.initials: RK
authors.lastname: Roy
authors.affiliation: Department of Physics, School of Physical Sciences, Sikkim University , Gangtok 737102 Sikkim, India.
authors.forename: Archana
authors.initials: A
authors.lastname: Tiwari
authors.affiliation: Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati, 781039 Assam, India.
authors.forename: Chandan
authors.initials: C
authors.lastname: Mukherjee