Co(II)/Zn(II) Coordination Polymers with Angular Dicarboxylate and Flexible N-Donor Struts: Structural and Photoluminescence Studies

Four mixed ligand coordination polymers [Co(BrIP)(4-BPMP)(1.5)center dot H2O](n) (1), [{Zn-2(BrIP)(2) (HBrIP)-(H3-BPMP)}center dot 4H(2)O](n) (2), [{Co(SDB)(3-BPMP)}center dot(C4H8O)center dot H2O](n) (3) and [{Co(SDB)(4-BPMP)}center dot 2H(2)O](n) (4) (where 4-BPMP = 1,4-bis(4-pyridylmethyl)piperazine, 3-BPMP = 1,4-bis(3-pyridylmethyl)piperazine, H2BrIP = 5-bromoisophthalic acid, and H2SDB = 4,4'-sulfonyldibenzoic acid) have been synthesized by solvothermal methods. Crystal structure of 1 revealed that 4-BPMP ligands (present in different conformations) in conjunction with BrIP and metal nodes engender an interpenetrated two-dimensional (2D) grid-type network. Compound 2 comprises of one-dimensional metal organic ladder patterns with pendent carboxylic acid sites on HBrIP moieties. Coordination polymers 3 and 4 exhibit [Co-2(SDB)(2)](n) double chain loops containing "paddle-wheel" secondary building units tethered by 3-BPMP and 4-BPMP respectively, generating (4,4) grid-type 2D nets. Comprehensive characterization, structural analysis, and photoluminescence behavior of 1-4 are discussed.