Zusammenfassung
Three new coordination compounds of Cu(II), Co(II), and Zn(II) based on
different dicarboxylic acids formulated as
(AcrH)Cu(pydc)(pydcH)center dot 5H(2)O (1)
(2a-4mpyH)(2)M(pyzdc)(2)(H(2)O)(2)center dot 6H(2)O; M = Co(II) (2)
and Zn(II) (3) have been synthesized and structurally characterized by
elemental analyses, IR spectroscopy, and single crystal X-ray
diffraction (where pydcH(2) = pyridine-2,6- dicarboxylic acid; Acr =
acridine; 2a-4mpy = 2amino- 4-methyl pyridine; pyzdcH(2) =
1,4-pyrazin-2, 3-dicarboxylic acid). In all cases, the metal centers
have distorted octahedral coordination geometries. Through hydrogen
bonding (such as O-H center dot center dot center dot O and N-H center
dot center dot center dot O) and/or slipped or offset p-p stacking
interactions, 3D supramolecular networks are constructed in these
complexes. In the crystalline network, O-H center dot center dot center
dot O hydrogen bonding create (H(2)O)(n) water clusters, so the hydrogen
bond interactions play an important role in sustaining of the
supramolecular solid-state architectures in compounds 1-3. The species
in the solution media were studied by potentiometric method. The
protonation constants of 2a-4mpy, 2-apy = 2-aminopyridine, pydc and
pyzdc in aqueous solution, pydc and Acr in a 50\% dioxane-50\% water
(v/v) solvent, as well as the equilibrium constants for three
proton-transfer systems, pyzdc-2a-4mpy, pydc-2-apy, and pydc-Acr were
calculated using potentiometrical method. The stoichiometry and
stability of complexation during the first proton-transfer system with
Cu(2+), Co(2+), and Zn(2+) ions and also the second proton-transfer
system with Fe(3+) and Cr(3+) ions in aqueous solution were investigated
by potentiometric pH titration method, from point of comparison view of
their behaviors in the solution state. The stoichiometry and stability
of complexation of third system with Cu(2+) and Zn(2+), metal ions in
50\% dioxane-50\% water (v/v) solvent were also investigated by the
cited method. The stoichiometry of the most complex species in solution
were compared with corresponding crystalline metal ion complexes.
Furthermore, DFT calculations have been carried out on the Cu(II) and
Zn(II) complexes in the presence of pydcH(2) and pyzdcH(2) in order to
better understanding of their molecular orbital structures of HOMO and
LUMO.
Nutzer