Bi- and trinuclear cobalt based coordination polymers constructed from aromatic polycarboxylic acids and 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene: Crystal structure and magnetic properties

Two new metal-organic frameworks (MOFs) [Co(btx)(bdc)(H2O)](n) and [Co-3(btx)(3)(btc)(2)(H2O)(2)](n) 2, (btx = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene; H(2)bdc = 1,4-terephthalate acid; H(3)btc = 1,3,5-benzene-tricarboxylate acid) have been synthesized and characterized by single-crystal X-ray diffraction studies and low temperature magnetic measurements. Compounds 1 and 2 are three-dimensional compounds whose structures can be described as layers of Co-2 units (1) and Co-3 (2) units with the carboxylate groups acting as mono or bidentate ligand, which are further connected through the flexible bis(triazole) ligand. The study of the magnetic properties of 1 and 2 in the temperature range 2-300 K shows the occurrence of weak ferromagnetic interactions in 1 due to the anti-syn carboxylate bridge and weak antiferromagnetic interactions in 2 between the high-spin Co(II) ions. (C) 2010 Elsevier B.V. All rights reserved.