Three coordination polymers of manganese(II), cadmium(II) with a flexible ligand of cis, cis, cis-1,2,3,4-cyclopentanetetracarboxylic acid: crystal structures, thermal decomposition mechanisms and magnetic properties.

The synthesized condition by means of controlling pH values of the reaction mixtures has been explored. Three Mn2+, Cd2+ ion coordination polymers with the fully deprotonated cis, cis, cis-1,2,3,4-cyclopentanetetracarboxylic acid (H4L) ligand were synthesized and characterized, sometimes incorporating different auxiliary ligand: {[Mn(H2O)6][Mn3(L)2(H2O)2]}·3H2O (1), [Cd2L(H2O)4] (2) and [Cd2Lphen)2(H2O)2]·3H2O (3) (phen = 1,10-phenanthroline). With an initial of pH values of 6.0, 4.0 and 9.0 of the reaction mixtures, we get the compounds 1, 2 and 3, respectively. In crystal of 1, two crystallographic different Mn2+ ions (Mn1 and Mn2) form a negatively charged coordination polymeric chain, which contains a centrosymmetrically linear trinuclear Mn2+ cluster (Mn3L2) subunit; another crystallographically independent Mn2+ ions (Mn3) coordinated by six water molecules act as counter ions to link the neighboring coordination polymeric chains via intermolecular H-bond interactions. The Mn2+ ions in 1 were completely replaced by Cd2+ ions to give 2 and 3, respectively. Complex 2 shows 3D distributions of Cd2+ ions while Complex 3 displays 2D networks contributed by intermolecular H-bond interactions. Three complexes exhibit distinct thermal decomposition mechanisms, and the deprotonated cis, cis, cis-1,2,3,4-cyclopentan-etetracarboxylic acid ligands decompose in 420–700 °C to give the residue MnO + C in 1 and CdO in 2 and in 3. Complex 1 shows a complicated magnetic behavior of coexistence of antiferromagnetic exchange interactions between neighboring Mn2+ ions. [ABSTRACT FROM AUTHOR]