Layered and self-penetrated cadmium isophthalate and 5-methylisophthalate coordination polymers containing bis(4-pyridylformyl)piperazine or bis(4-pyridylmethyl)homopiperazine ligands

Hydrothermal synthesis has afforded divalent cadmium coordination polymers containing isophthalate (ip) or 5-methylisophthalate (mip) dicarboxylate ligands and bis(4-pyridylformyl) piperazine (4-bpfp) or bis(4-pyridylmethyl) homopiperazine (4-bpmh) tethers. {[Cd-2(ip)(2)(H2O)(2)(4-bpfp)]center dot 7H(2)O}(n) (1) displays a (4,4) grid topology based on {Cd2O2} dimeric clusters, along with infinite'' water molecule tapes with rare T4(0)A(1) classification. {[Cd(mip)(H2O)(4-bpfp)]center dot 3H(2)O}(n) (2) also exhibits (4,4) grid layers but with 2D + 2D -> 3D mutual inclined interpenetration instead of parallel stacking. [Cd-4(ip)(4)(4-bpmh)(2)](n) (3) has tetrameric {Cd4(ip) 4} cluster units linked by ip and 4-bpmh ligands into a unique self-penetrated 3,5,5,5-connected tetranodal net with (4.8(2))(4(3)6(2)8(5))(4(4)6(4)8(2))(4.5(6)4(8)) topology. {[Cd-2(mip)(2)(H2O)(2)(4-bpmh)]center dot 2H(2)O}(n) (4) possesses a structure similar to that of 1, without the aggregated water molecule tapes. All four materials emit visible light upon ultraviolet excitation, ascribed to ligand-based electronic transitions. (C) 2011 Elsevier B. V. All rights reserved.