Exchange coupling mediated by N-H···Cl hydrogen bonds: experimental and theoretical study of the frustrated magnetic system in bis(o-phenylenediamine)nickel(II) chloride.

The title compound crystallizes in the monoclinic P2(1)/c space group with a = 11.2470(3) Å, b = 5.9034(2) Å, c = 12.0886(3) Å, β = 115.143(1)°, and V = 726.58(4) Å(3) and consists of discrete monomeric NiCl(2)(o-phenylendiamine)(2) molecules. Each o-phen ligand coordinates in a bidentate mode with the chloride ions occupying trans positions in the resulting tetragonally distorted octahedral coordination sphere. Two discrete sets of N-H···Cl hydrogen bonds link the octahedral molecules into a two-dimensional network, with type 1 interactions linking adjacent monomers along the c axis and type 2 interactions linking monomers along the diagonals in the bc plane. Analysis of the magnetic data reveals the existence of weak antiferromagnetic coupling within the layers via these hydrogen bonds, in addition to the presence of zero field splitting, with the best fit obtained for a 1d antiferromagnetic model with g = 2.0917(7), J/k = -2.11(4) K [J = -1.47(3) cm(-1)], and D = 1.05(3) cm(-1) [β = D/|J| = 0.72(6)] for the model with D > 0 and g = 2.0911(6), J/k = -2.26(1) K [J = -1.57(1) cm(-1)], and D = -0.86(1) cm(-1) [β = D/|J| = 0.55(6)] for the model with D < 0. Theoretical calculations of the exchange coupling confirm the experimental results, yielding values of J(1) = -1.39 cm(-1) for the type 1 hydrogen bonds and J(2)/k = -0.56 cm(-1) for the type 2 hydrogen bonds.