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 1 and [Co3(btx)3(btc)2(H2O)2]n 2, (btx = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene; H2bdc = 1,4-terephthalate acid; H3btc = 1,3,5-benzenetricarboxylate 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 Co2 units (1) and Co3 (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.