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 p H values of the reaction mixtures has been explored. Three Mn 2+ , Cd 2+ ion coordination polymers with the fully deprotonated cis, cis, cis-1,2,3,4-cyclopentanetetracarboxylic acid ( H 4 L ) ligand were synthesized and characterized, sometimes incorporating different auxiliary ligand: {[Mn(H 2 O) 6 ][Mn 3 (L) 2 (H 2 O) 2 ]}·3H 2 O ( 1 ), [Cd 2 L(H 2 O) 4 ] ( 2 ) and [Cd 2 Lphen) 2 (H 2 O) 2 ]·3H 2 O ( 3 ) (phen = 1,10-phenanthroline). With an initial of p H 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 Mn 2+ ions (Mn1 and Mn2) form a negatively charged coordination polymeric chain, which contains a centrosymmetrically linear trinuclear Mn 2+ cluster (Mn 3 L 2 ) subunit; another crystallographically independent Mn 2+ ions (Mn3) coordinated by six water molecules act as counter ions to link the neighboring coordination polymeric chains via intermolecular H-bond interactions. The Mn 2+ ions in 1 were completely replaced by Cd 2+ ions to give 2 and 3 , respectively. Complex 2 shows 3D distributions of Cd 2+ 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 Mn 2+ ions. Graphical abstract