| Abstract: | ![]()
The reaction of the proton‐transfer compound piperazine‐1,4‐diium pyrazine‐2,3‐dicarboxylate 4.5‐hydrate, C4H12N22+·C6H2N2O42−·4.5H2O or (pipzH2)(pyzdc)·4.5H2O (pyzdcH2 is pyrazine‐2,3‐dicarboxylic acid and pipz is piperazine), (I), with Zn(NO3)2·6H2O and CoCl2·6H2O results in the formation of bis(piperazine‐1,4‐diium) bis(μ‐pyrazine‐2,3‐dicarboxylato)‐κ3N1,O2:O3;κ3O3:N1,O2‐bis[aqua(pyrazine‐2,3‐dicarboxylato‐κ2N1,O2)zinc(II)] decahydrate, (C4H12N2)2[Zn2(C6H2N2O4)4(H2O)2]·10H2O or (pipzH2)2[Zn(pyzdc)2(H2O)]2·10H2O, (II), and catena‐poly[piperazine‐1,4‐diium [cobalt(II)‐bis(μ‐pyrazine‐2,3‐dicarboxylato)‐κ3N1,O2:O3;κ3O3:N1,O2] hexahydrate], {(C4H12N2)[Co(C6H2N2O4)2]·6H2O}n or {(pipzH2)[Co(pyzdc)2]·6H2O}n, (III), respectively. In (I), pyzdcH2 is doubly deprotonated on reaction with piperazine as a base. Compound (II) crystallizes as a dimer, whereas compound (III) exists as a one‐dimensional coordination polymer. In (II), two pyzdc2− groups chelate to each of the two ZnII atoms through a ring N atom and an O atom of the 2‐carboxylate group. In one ligand, the adjacent 3‐carboxylate group bridges to a neighbouring metal atom. A water molecule ligates in the sixth coordination site. The structure of (II) can be described as a commensurate superlattice due to an ordering in the hydrogen‐bonded network. In (III), no water is coordinated to the metal atom and the coordination sphere is comprised of two N,O‐chelates plus two bridging O atoms. A large number of hydrogen bonds are observed in all three compounds. These interactions, as well as π–π and C=O...π stacking interactions, play important structural roles. |
