Akademik Veri Yönetim Sistemi
POLYHEDRON, cilt.29, sa.11, ss.2345-2351, 2010 (SCI-Expanded)
A new homonuclear and heterodinuclear pyridine-2,6-dicarboxylate complexes, formulated as (enH(2))[Cu(dipic)(2)]center dot 2.5H(2)O (1) and [Cu(mu-dipic)(2)Zn(H2O)(5)]center dot 2H(2)O (2) (en = ethylenediamine, dipic = pyridine-2,6-dicarboxylate) were synthesized according the reactions between the three species of copper(II) and zinc(II) nitrate, ethylenediamine and pyridine-2,6-dicarboxylic acid. Complexes have been characterized by the methods of elemental, spectroscopic (IR and UV-Vis), thermal (TG/DTG, DTA) analysis, magnetic measurement and single crystal X-ray diffraction. Correlation coefficient, activation energies, E*; pre-exponential factor, A; entropies, S*; enthalpies, H* and Gibbs free energies, G* of the thermal decomposition reactions have been calculated under the derivations from thermogravimetric (TG) and differential thermogravimetric (DTG) curves, using the Coats-Redfern and Horowitz-Metzger methods. Complex 1 belonged to a six-coordinate behavior with a distorted octahedral geometry around Cu(II), that the structure contains two pyridine-2,6-dicarboxylate species as a tridentate ligands and ethylenediaminium cation as a counter ion as well as 2.5 uncoordinated water molecules. On the other hand complex 2 contains six-coordinated Cu(II) and Zn(II) ions, which are linked by two O atoms of the same carboxyl group from dipicolinic acid. The dipicolinate dianions again behave as tridentate ligands in 2. Two uncoordinated water molecules are also present in the structure. The structure units of 1 and 2 are mutually held by the hydrogen bonds and pi center dot center dot center dot pi interactions. There is also a C-O center dot center dot center dot pi IT interaction in 2. The Cu(II) complexes are connected to one another via O-H center dot center dot center dot O hydrogen bonds, forming water clusters, which play an important role in the stabilization of the crystal structure. In the water clusters, the water molecules are trapped by the cooperative association of coordination interactions as well as hydrogen bonds. (C) 2010 Elsevier Ltd. All rights reserved.