EPR of Cu(II)-doped seven-coordinate inclusion compounds, M(stpy)(3)(NO3)(2)center dot 1/2stgy (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 Wern er-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 g(33) = 2.298, g(22) = 2.108, g(11) = 2.066, A(33) = 107.3, A(22) = 54.4 and A(11) = 23.1 x 10(-4) cm(-1) for 1 and g(33) = 2.292, g(22) = 2.111, g(11) = 2.0 67, A(33) = 107.5, A(22) = 54.7 and A(11) = 22.9 x 10(-4) cm(-1) for 2. Ang ular variation studies for both 1 and 2 suggest that the Cu(II) ions are su bstitutionally incorporated in the host lattices. The magnitude of Cu(II) h yperfine coupling constant (A(33)) 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 larg e reductions in Cu(II) hyperfine coupling are explicable in terms of a mixe d d(x2 - y2)/d(z2) ground state and delocalised of unpaired spin density on to the ligands. (C) 2001 Elsevier Science B.V. All rights reserved.