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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

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journal contribution
posted on 07.05.2012, 00:00 by Roger D. Willett, Carlos J. Gómez-García, Brendan Twamley, Silvia Gómez-Coca, Eliseo Ruiz
The title compound crystallizes in the monoclinic P21/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) Å3 and consists of discrete monomeric NiCl2(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 J1 = −1.39 cm–1 for the type 1 hydrogen bonds and J2/k = −0.56 cm–1 for the type 2 hydrogen bonds.

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