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. {[Cd2(ip)2(H2O)2(4-bpfp)]·7H2O}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)]·3H2O}n (2) also exhibits (4,4) grid layers but with 2D + 2D → 3D mutual inclined interpenetration instead of parallel stacking. [Cd4(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 (4.82)(436285)(446482)(4.5648) topology. {[Cd2(mip)2(H2O)2(4-bpmh)]·2H2O}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.