New pyridine-2,3,5,6-tetracarboxylato (H_4pdtc) complexes: Synthesis, crystal structures and magnetic properties of K_2[Mn(H _2O)(pdtc)]·3H_2O 1, Na_2[M _3(H_2O)_6(pdtc)_2]·6H _2O (M=Mn 2, Co 3)

摘要

Three new pyridine-2,3,5,6-tetracarboxylato (H_4pdtc) complexes K_2[Mn(H_2O)(pdtc)]·3H_2O 1, Na _2[M_3(H_2O)_6(pdtc)_2] ·6H_2O (M=Mn 2, Co 3) were obtained and characterized by single-crystal X-ray diffraction methods and magnetic measurements. The characteristic building blocks of 1-3 are the pdtc bridged stair-like chains 1{[M(H_2O)](pdtc)_(3/3)}~(2-), which results from the six-coordinated transition metal atoms bridged by pdtc~(4-) ligands. The infinite chains in 1 are assembled by hydrogen bonds into 2D supramolecular networks, which are held together by (4·8~2) topological K ~+-H_2O networks to complete 3D architecture. While the stair-like chains in 2 and 3 are interconnected by trans-[M(H_2O) _4]~(2+) moieties to 2D polymeric layers, which are bridged by dimeric [Na_2(μ-H_2O)_2(H_2O) _2]~(2+) moieties to build up 3D framework. The magnetic properties of 1-3 were analyzed on the basis of (i) linear trinuclear M _3 models and (ii) the free Mn~(2+) and Co~(2+) ions with the zero-field splitting effect and spin-orbit coupling effect, respectively.