Iminosemiquinone complexes of copper have been prepared by treating Cu metal with 2,4,6,8-tetra-tert-butylphenoxazin-1-one (PhenoxBQ). Reactions carried out with PPh3 gave CuI(PPh3)2(PhenoxSQ). Crystallographic characterization of crystals obtained as the acetonitrile solvate (triclinic, P1, a = 11.414(2) Å, b = 15.431(2) Å, c = 17.999(3) Å, α = 92.88(1)°, β = 94.21(1)°, γ = 109.84(1)°, V = 2964.4(8) Å3, Z = 2, R = 0.064) has shown that the coordination geometry is tetrahedral, EPR spectra indicate that the unpaired electron is ligand-based, and electrochemical properties consist of one-electron oxidation and reduction reactions at the iminoquinone ligand. Reactions carried out in the absence of coligand or in the presence of a nitrogen-donor coligand gave CuII(PhenoxSQ)2. Crystallographic characterization of crystals obtained as the dichloromethane solvate (monoclinic, C2/c, 28.40(2) Å, 12.946(4) Å, a = 20.552(12) Å, β = 129.32(4)°, V = 5846(6) Å3, R = 0.070) has shown that the molecule has a distorted tetrahedral structure. Electrochemical characterization has indicated that the complex undergoes two one-electron oxidations and two one-electron reductions, all occurring at the iminoquinone ligands. EPR spectra and variable-temperature magnetic measurements indicate that exchange between PhenoxSQ ligands is ferromagnetic, while Cu-PhenoxSQ exchange is antiferromagnetic. At low temperature, the complex has a ligand-based S = 1/2 magnetic ground state.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry