Syntheses, Crystal Structures and Magnetic Properties of Heterodinuclear Nickel(II)-Manganese(II)-Based One- and Two-Dimensional Coordination Polymers: Magnetostructural Correlation

This investigation deals with the syntheses, crystal structures and magnetic properties of three diphenoxo-bridged dinuclear (NiMnII)-Mn-II based coordination polymers of composition [(NiLMnII)-L-II-Mn-1(mu(1,5)-dca)(2)](n) (1), [(NiLMnII)-L-II-Mn-2(mu(1,5)-dca)(2)](n) (2) and [Ni-II(MeOH)(2)(LMnII)-Mn-1(mu-Htma)](n)center dot nDMF (3), where H2L1=N,N-bis(3-methoxysalicylidene)-1,3-propanediamine and H2L2=N,N-bis(3-methoxysalicylidene)-1,4-butanediamine and H(3)tma=trimesic acid. The N(imine)(2)O(phenoxo)(2) and O(phenoxo)(2)O(methoxy)(2) compartments of [L-1](2-)/[L-2](2-) in 1-3 are occupied by, respectively, Ni-II and Mn-II ions. Dicyanamide ligands link the dinuclear units to form different types of coordination polymers in 1 and 2; two-dimensional in the former but one-dimensional in the latter. The Mn-II center in 3 is coordinated to two oxygen atoms of two carboxylate groups of two Htma, forming a zigzag one-dimensional structure. Variable-temperature (2-300K) magnetic susceptibility data of 1-3 reveal weak antiferromagnetic interaction in the dinuclear core. Taking H=-2JS(1)S(2) as the Hamiltonian for magnetic exchange, the data were nicely simulated with J=-2.80cm(-1) and zJ=-0.04cm(-1) for 1, J=-3.71cm(-1) and zJ=0.08cm(-1) for 2 and J=-3.41cm(-1) for 3, revealing weak antiferromagnetic interaction in the dinuclear core and very weak antiferromagnetic or ferromagnetic interaction among the dinuclear cores. A J versus Ni-O(phenoxo)-Mn angle magneto-structural correlation is proposed.