1-D and 2-D coordination polymers of cerium(III) with pyridine-2,4,6-tricarboxylic acid: synthesis and structural, spectroscopic, and thermal properties

Two new Ce(III) complexes of pyridine-2,4,6-tricarboxylate (ptc), [Ce-2(H2O)(2)(C8H3NO6)(4) (C2O4)Na-2(H2O)(5)](n)(H2O)(4) (1) and [Ce(H2O)(3)(C8H2NO6)](n)(H2O) (2), were crystallized in the triclinic space group P-1 and the monoclinic space group P2(1)/c, respectively. These polymers were also characterized by elemental analysis, FTIR spectroscopy, and thermogravimetric analysis. The latter shows high thermal stability for 1. Each Ce(III) is ten-coordinate with two nitrogen atoms from two pyridine rings, five oxygen atoms from five carboxylic groups, two oxygen atoms from oxalate and one oxygen from water. Oxygen at the 2,6-position of ptc is a bridge to construct a 1-D polymer for 1. Each Ce(III) is nine-coordinate with five oxygen atoms and one nitrogen from ptc and three water molecules, giving a tricapped trigonal prism for 2. Each ptc bridges three Ce(III) ions with the formation of 2-D polymeric chains, and each carboxylic acid group at the 2,6-position of ptc is only bound to one Ce(III). The other carboxylate at the 6-position is bound to another Ce(III), and the carboxylates at the four-position adopt a chelating mode. Molecules are linked principally by OH center dot center dot center dot O hydrogen bonds involving water and carboxylate, forming R-1(2) (6), R-3(3) (14), and R-4(4) (27) rings, which link to give a 3-D network.