Coordination polymers of the conformation-flexible 1,2,4,5-cyclohexanetetracarboxylate: synthesis, structures and transforming mechanism studies?

CrystEngComm Pub Date: 2010-07-26 DOI: 10.1039/C003764H

Abstract

Four new cobalt coordination polymers based on cyclohexane-1e,2a,4a,5e-tetracarboxylic acid (2e+2a, H4LI), [Co4(μ4-LI)2(4,4′-bpy)3(H2O)6]·2H2O (1), [Co4(μ5-LI)2(4,4′-bpy)3(H2O)4]·3H2O (2), [Co2(μ4-LIV)(2,2′-bpy)2(H2O)2] (3) and [Co2(μ4-LIV)(1,10-phen)2(H2O)2]·4H2O (4), were synthesized in hydrothermal reactions with some auxiliary ligands to study the conformations and coordination chemistry of H4L. The structural analysis revealed a new conformation, cyclohexane-1e,2e,4e,5e-tetracarboxylic acid (4e, H4LIV), for the flexible ligand H4L trapped in compounds 3 and 4, which were synthesized in the presence of different chelating ligands whereas in the compounds of 1 and 2, the ligands adapt the same conformation (2e+2a, H4LI) as found in the solid state when the linear bridging 4,4′-bpy was added as auxiliary ligand. The conformational transformation originated from the removal of α-protons of H4L, which has been confirmed via the production of [CuI(4,4′-bpy)(H2O)]2(ip)·2H2O (5) (H2ip = isophthalic acid) from the reaction of Cu2+ ions, H4LI ligand and 4,4′-bpy under hydrothermal conditions. The magnetic properties of 2 and 3 were investigated‥

Graphical abstract: Coordination polymers of the conformation-flexible 1,2,4,5-cyclohexanetetracarboxylate: synthesis, structures and transforming mechanism studies
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