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·H2O]n (1), [{Zn2(BrIP)2 (HBrIP)­(H3-BPMP)}·4H2O]n (2), [{Co­(SDB)­(3-BPMP)}·(C4H8O)·H2O]n (3) and [{Co­(SDB)­(4-BPMP)}·2H2O]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 [Co2(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.