One-Dimensional Manganese Coordination Polymers Composed of Polynuclear Cluster Blocks and Polypyridyl Linkers: Structures and Properties

The synthesis, crystal structures and magnetic properties of five new manganese compounds are reported. These include a linear trinuclear cluster [Mn(II)(3)(O2CCHMe2)(6)(dpa)(2)]center dot 2MeCN (1) (dpa = 2,2'-dipyridylamine), a tetranuclear cluster [Mn(II)(2)Mn(III)(2)O-2(O2CCMe3)(6)(bpy)(2)] (3) (bpy = 2,2'-bipyridine), and chain coordination polymers composed of cluster blocks such as Mn-3, Mn3O, and Mn4O2 bridged by 2,2'-bipyrimidine (bpm) or hexamethylentetramine (hmta) ligands to give ([Mn(II)(2)Mn(III)(2)O-2(O2CCMe3)(6)(bpm)]center dot 2EtOH)(n) (2), [Mn(II)(2)Mn(III)(2)O-2(O2CCHMe2)(6)(bpm)(EtOH)(4)](n) (4), and (([Mn(II)(2)Mn(III)(2)O-2(O2CCMe3)(6)(hmta)(2)]center dot EtOH)(n) (5). The magnetic analysis of the compounds was achieved using a combination of vector coupling and full-matrix diagonalization methods. Susceptibility data for compound 1 was fitted using a vector coupling model to give g = 2.02(1) and 2J/k(B) = -5.38(2) K. To model the trimer chain, we used vector coupling for initial values of J(1) and then diagonalization techniques to estimate J(2) to give g = 1.98(1), 2J(1)/kB = -3.3(1) K and 2J(2)/k(B) = -1.0(1) K by approximating the system to a dimer of trimers. The analysis of 3 was made difficult by the mixture of polymorphs and the difficulties of a three-J model, while for 4 an analysis was not possible because of the size of the computation and the relative magnitudes of the three couplings. Compound 5 was modeled using the same techniques as 2 to give g = 1.99(1), 2J(1)/k(B) = +32.5(2) K, 2J(2)/k(B) = -16.8(1) K, and 2J(3)/k(B) = +0.4(1) K. The combination of techniques has worked well for compounds 2 and 5 and thus opens up a method of modeling complex chains.