Diamine substitution reactions of tetrahydrate succinato nickel, cobalt, and zinc coordination polymers

Investigation on the substitution reactions of tetrahydrate succinato metal coordination polymers with diamine ligands results in the isolations of four new coordination polymers, [M(suc)(bpy)(H2O)(2)](n).nH(2)O (M = Ni, 2; M = Co, 2a), [Ni(suc)(phen)(H2O)](n) (3), and [Zn(suc)(bpy)](n).2nH(2)O (4) (H(2)suc = succinic acid, bpy = 2,2'-bipyridine, and phen = 1,10-phenanthroline). In the isomorphous compounds of 2 and 2a, the metal(II) ions are linked by a bridging succinate ligand to form 1D helix chains in bis-monodentate mode. In compounds 3 and 4, the succinate ligand connects adjacent nickel/zinc(II) atoms through three oxygen atoms from two carboxyl groups, forming an infinite zipper like chain along the a axis. The nickel compound 3 forms a double helix chain through strong hydrogen bonding. Notably, the double-stranded ribbons in compound 4 formed through moderately strong face-to-face pi-pi stacking segregated an unprecedented water chain constructed from dimeric water molecules.