Construction of coordination polymers based on methylenebis(3,5-dimethylpyrazole) and varied aromatic carboxylic acids

Abstract

Six new coordination polymers, namely, [Co(Cl-BDC)(H₂MDP)]·0.5H₂O (1), [Cd(Cl-BDC)(H₂MDP)] (2), [Cd(OH-ip)(H₂MDP)₂]·H₂O (3), [Mn(NO₂-ip)(H₂MDP)(H₂O)] (4), [Cu(BTEC)_1/2(H₂MDP)] (5), and [Co(BTEC)_1/2(H₂MDP)]·H₂O (6) (H₂MDP = methylenebis(3,5-dimethylpyrazole), Cl-H₂BDC = 2,5-dichloroterephthalic acid, OH-H₂ip = 5-hydroxy-1,3-benzenedicarboxylic acid, NO₂-H₂ip = 5-nitro-1,3-benzenedicarboxylic acid, H₄BTEC = 1,2,4,5-benzenetetracarboxylic acid) have been hydrothermally synthesized by using H₂MDP as the main ligand and varying aromatic acids as auxiliary ligands, and characterized by single-crystal X-ray structure determination, FT-IR, elemental analysis, and powder X-ray diffraction. It was found that in complexes 2, 3, 4, and 6 the H₂MDP ligands adopt a cis-conformation and tend to form M₂L₂-type metallocyclic units (SBU-1). These metallocyclic units further serve as linkers to connect the {metal–aromatic carboxylate}_n chains to form two-dimensional frameworks with different structural features and topologies, i.e. 2D 6³-hcb network for 2, (4,4) net for 3, undulated 6³-hcb layered framework for 4, and dual (3,4)-connected net for 6 with point (Schläfli) symbol of (4·6²)₂(4²·6²·8²). In complexes 1 and 5, the H₂MDP ligands adopt a trans-conformation, and tend to link {metal–aromatic carboxylate}_n chains into a higher dimensional framework, i.e. 3D triply interpenetrated dia network for 1 and dual (4,4)-connected double-layered structure for 5 with point (Schläfli) symbol of (5⁴·6²)(5⁵·8¹)₂. Moreover, the magnetic properties of complexes 1 and 6, and photoluminescent properties of 3 have also been investigated.