Syntheses, structures and properties of nickel(II) and manganese(II) coordination polymers based on V-shaped bis-imidazole and aromatic carboxylate ligands

Using V-shaped mixed ligands bis-imidazole and aromatic carboxylic acids, five new coordination polymers namely, {[Ni(B-im)(Br-a)Cl].H2O}(n) (1), {[Ni(B-im)(I-a)(H2O)(2)].0.5H(2)O}(n) (2), [Ni(B-im)(I-a)(H2O)2](n) (3), [Ni(B-im)(M-a)(H2O)(2)](n) (4) and {[Mn-2(B-im)(2)(1-a)(2)].2H(2)O}(n) (5) [B-im = 1,1'-(5-methyl-1,3-phenylene)bis(1H-imidazole), Br-a = 5-bromonicotinic acid, I-a = isophthalic acid and M-a = 5-methylisophthalic acid] were solvothermally synthesized and fully characterized by IR spectra, element analyses, X-ray powder and single-crystal diffractions, and thermogravimetric analyses. Complexes 1 and 2 feature polymeric macrocyclic chain structures containing interesting nanotubular channels, which are constructed by bridging 30-membered macrocyclic [Ni3(B-im)(3)] subunits with Br-a ligands and by bridging folded 20-membered macrocyclic [Ni-2(B-im)(2)] subunits with I-a ligands, respectively. Isomorphic complexes 3 and 4 represent double-chain structures containing folded 18-membered macrocyclic [Ni2(B-im)(I-a)] subunits and [Ni2(B-im)(M-a)] subunits, respectively. Complex 5 is a 2D porous coordination polymer containing novel chiral four-stranded Mn(II) chains consisting of two (B-im)-bridged aspiral chiral chains and two (I-a)-bridged heterochiral coaxial 2(1)-helical chains. The results of thermal gravimetric analyses suggest that the dehydrated frameworks of 1-5 are stable up to 320 degrees C. Additionally, the magnetism of complexes 3 and 5 were also investigated. (C) 2016 Elsevier Ltd. All rights reserved.