J. Iran. Chem. Soc., Vol. 6, No. 3 September 2009, pp.620~637.

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Synthesis and Crystal Structure of Mn(II) and Hg(II) Compounds and Solution Studies of Mn(II), Zn(II), Cd(II) and Hg(II) Compounds Based on Piperazinediium Pyridine-2,3-dicarboxylate

H. Aghabozorga,*, S. Daneshvarb, E. Motyeianc, F. Manteghia, R. Khadivid, M. Ghadermazie, A. Shokrollahif, M. Ghaedif, S. Derkif and M. Shamsipurg

aFaculty of Chemistry, Tarbiat Moallem University, Tehran, Iran
bDepartment of Chemistry, Islamic Azad University, Ardabil Branch, Ardabil, Iran
cDepartment of Chemistry, Faculty of Science, Payame Noor University, Qom Center, Qom, Iran
dDepartment of Chemistry, Islamic Azad University, North Tehran Branch, Tehran, Iran
eDepartment of Chemistry, Faculty of Science, University of Kurdistan, Sanandaj, Iran
fDepartment of Chemistry, Yasouj University, Yasouj, Iran
gDepartment of Chemistry, Razi University, Kermanshah, Iran

Novel metal organic frameworks including {(pipzH2)[Mn(py-2,3-dc)2]·7.75H2O}n, 1, {(pipzH2)[Zn(py-2,3-dc)2]·4H2O}n, 2, [Cd(py-2,3-dc)(H2O)3]n, 3 and {(pipzH2)[Hg4Cl10]}n, 4, in which pipz is piperazine and py-2,3-dcH2 is pyridine-2,3-dicarboxylic acid were synthesized applying a proton transfer ion pair i.e.(pipzH2)(py-2,3-dcH)2 and corresponding metallic salts and studied by IR, 1H NMR, 13C NMR spectroscopy and single crystal X-ray diffractometry. The space group of compounds 1 and 4 are P21/c and C2/c of monoclinic system, respectively. The crystal dimensions are a = 20.108(2) Å, b = 19.910(2) Å, c = 12.997(1) Å, β = 94.354(2)š for 1 and a = 15.940(1) Å, b = 11.2690(9) Å, c = 11.1307(9) Å, β = 90.685(2)š for 4. The crystal structures of 2 and 3 have been reported previously. However, their solution studies are discussed here. The compounds had all polymeric structures. Although ZnII, CdII and HgII were elements of the same group, their behavior against the ion pair was essentially different. Various supramolecular interactions mainly hydrogen bonds of the type O-H···O, N-H···O, C-H···O, N-H···Cl and C-H···Cl were observed in the structures. There was an unusual and huge water cluster in the structure of compound 1. The solution states of compounds 1-4 were studied and reported. The protonation constants of pipz and py-2,3-dc, the py-2,3-dc/pipz proton transfer equilibrium constants and stoichiometry and stability of the system with Mn2+, Zn2+, Cd2+ and Hg2+ ions in aqueous solution were investigated by potentiometric pH titrations.

Keywords: : Metal complexes, Crystal structure, Solution study, Supramolecular chemistry, Water cluster

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