EPR of Cu(II)-doped seven-coordinate inclusion compounds, M(stpy)<inf>3</inf>(NO<inf>3</inf>)<inf>2</inf>·1/2stpy (M = Cd(II) and Zn(II), stpy = trans-4-styrylpyridine): Low symmetry effects in admixture of ground states

Single crystal EPR of Cu(II)-doped low symmetry pentagonal bipyramidal Werner-type clathrate inclusion complexes of Cd(stpy)3(NO3)2·1/2stpy(1) and Zn(stpy)3(NO3)2·1/2stpy(2) (stpy = trans-4-styrylpyridine) is reported. The spin Hamiltonian parameters are found to be orthorhombic with g33 = 2.298, g22 = 2.108, g11 = 2.066, A33 = 107.3, A22 = 54.4 and A11 = 23.1×10-4 cm-1 for 1 and g33 = 2.292, g22 = 2.111, g11 = 2.067, A33 = 107.5, A22 = 54.7 and A11 = 22.9×10-4 cm-1 for 2. Angular variation studies for both 1 and 2 suggest that the Cu(II) ions are substitutionally incorporated in the host lattices. The magnitude of Cu(II) hyperfine coupling constant (A33) in both 1 and 2 are found to be low, in comparison to those of the pure Cu(II) complex, indicative of low symmetry for the substitutional sites in accordance with the crystal data. Such large reductions in Cu(II) hyperfine coupling are explicable in terms of a mixed dx(2)-y(2)/dz(2) ground state and delocalization of unpaired spin density onto the ligands.