Fujito Nemoto

Spectroscopic studies on copper(II) complexes of chiral cyclens: [CuN4Cl] chromophores varying from square pyramidal to trigonal bipyramidal stereochemistry

A series of five copper(II) complexes with four geometrically isomeric ligands of 1,4,7,10-tetrabenzyl-2,5,8,11-tetraethyl-1,4,7,10-tetraazacyclododecane and with (2R,5R,8R,11R)-2,5,8,11-tetraethyl-1,4,7,10-tetraazacyclododecane has been investigated by means of ESR, CD and MCD in solution. X-ray studies reported separately had shown that the [CuN4Cl] chromophores were distorted to varying extents from square pyramidal to trigonal bipyramidal geometry. The stability and rigidity of the molecular structure have enabled us to carry out a complementary study of the crystalline state and solution chemistry. The ground state Kramers doublets varied from 3dx2−y2 to 3dz2 type with increasing distortion around the copper ion. The orbital sequence of the 3d1 positive hole, dx2−y2<dz2<dyz,xz<dxy, has been obtained for the C4v complexes. The 3dxy orbital is also the highest in energy for the complex with the 3dz2 type ground state doublet. This complex exhibited superhyperfine splitting in the gz region due to the chlorine nucleus, which implies the principal z axis of the g tensor is along the CuCl bond. The sign of the copper hyperfine tensors was determined by means of Swalens treatment. The changing values of the orbital coefficients decreasing for the 3dx2−z2 and increasing for the 3dz2, 3dxz and 3dyz in the ground state doublets have been attributed to concomitant elongation of the in-plane CuN bond and reduction of the out-of-plane CuCl bond length with the increasing distortion around the copper ions.

Transannular electron delocalization in the 1,8-diphenylnaphthalene radical anion studied by endor

Abstract ENDOR spectra were observed for the radical anion of 1.8-diphenylnaphthalene (I), with related radical anions of 1,8- dideuteriophenylnaphthalene and 1.8-bis( p -tolyl)-naphthalene. Observed hyperfine coupling constants were interpreted in terms of transannular interaction between π systems belonging to the two benzene rings of anion I.

Endor spectrum and heat of dissociation of the 9,10-dipropylanthracene dimer cation

Abstract The ENDOR spectrum or the 9,10-dipropylanthracene (DPA) cation, generated by oxidation of DPA in CH2Cl2 containing ≈ 10% CF3COOH and ≈5% (CF3CO)2O, exhibits clearly the existence of the dimer and monomer cation species. The heat of dissociation of the dimer cation in CH2C2 is estimated to be 22.3 kj mol−1.