New pyridine-2,3,5,6-tetracarboxylato (H4pdtc) complexes: Synthesis, crystal structures and magnetic properties of K2[Mn(H2O)(pdtc)]·3H2O 1, Na2[M3(H2O)6(pdtc)2]·6H2O (M=Mn 2, Co 3)

Three new pyridine-2,3,5,6-tetracarboxylato (H4pdtc) complexes K2[Mn(H2O)(pdtc)]·3H2O 1, Na2[M3(H2O)6(pdtc)2]·6H2O (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 View the MathML source∞1{[M(H2O)](pdtc)3/3}2–, which results from the six-coordinated transition metal atoms bridged by pdtc4− ligands. The infinite chains in 1 are assembled by hydrogen bonds into 2D supramolecular networks, which are held together by (4·82) topological K+–H2O networks to complete 3D architecture. While the stair-like chains in 2 and 3 are interconnected by trans-[M(H2O)4]2+ moieties to 2D polymeric layers, which are bridged by dimeric [Na2(μ-H2O)2(H2O)2]2+ moieties to build up 3D framework. The magnetic properties of 1–3 were analyzed on the basis of (i) linear trinuclear M3 models and (ii) the free Mn2+ and Co2+ ions with the zero-field splitting effect and spin–orbit coupling effect, respectively.