Abstract
The synthesis, thermogravimetric and X-ray structure analysis of a highly unusual copper compound prepared from a chiral tridentate Schiff base ligand is reported. The title compound [CuL(H(2)O(2)]. CuL(H(2)O(3)].H(2)O crystallizes in the orthorhombic crystal system in space group P2(1)2(1)2(1) with Z = 4. Two independent CuL(H(2)O)(n) complexes are present in the same unit cell, one five- and the other six- coordinate. The five-coordinate copper(II) centre occupies a distorted square-pyramidal geometry whereas the six-coordinate copper(II) centre has a distorted octahedral geometry. The independent copper complexes and the uncoordinated water molecule are joined together with intermolecular hydrogen bonds in a two-dimensional supramolecular network which lies parallel to the ab plane.
Highlights
Copper complexes of tridentate Schiff base ligands derived from amino acids and aromatic aldehydes have received considerable attention as a result of their inherent catalytic,[1,2,3] and biological activity and their potential similarity to enzymes.[4,5,6,7,8,9,10,11,12]
Different structures are often adopted, it can reasonably be assumed that these properties are partly due to the availability of sites of coordinative unsaturation at the metal centre and the presence of amino acid residues
For copper(II) complexes containing only solvent molecules in addition to a tridentate ONO Schiff base ligand, a 4-coordinate square planar geometry is possible,[15] in the majority of cases the Cu(II) ion adopts a 5-coordinate square pyramidal geometry where the fourth and fifth coordination sites are occupied by solvent or bridging ligands
Summary
Copper complexes of tridentate Schiff base ligands derived from amino acids and aromatic aldehydes have received considerable attention as a result of their inherent catalytic,[1,2,3] and biological activity and their potential similarity to enzymes.[4,5,6,7,8,9,10,11,12] different structures are often adopted, it can reasonably be assumed that these properties are partly due to the availability of sites of coordinative unsaturation at the metal centre and the presence of amino acid residues. A defining property of Cu(II) ions is that, unless a tridentate ligand is flexible enough to complement its distorted coordination sphere,[13] Cu(II) will preferably bind only one ligand.[14] for copper(II) complexes containing only solvent molecules in addition to a tridentate ONO Schiff base ligand, a 4-coordinate square planar geometry is possible,[15] in the majority of cases the Cu(II) ion adopts a 5-coordinate square pyramidal geometry where the fourth and fifth coordination sites are occupied by solvent or bridging ligands. A square pyramidal/octahedral arrangement has previously been observed with the highly flexible dipicolylamine ligand,[25] this example is perhaps more striking as the different geometries are created by a differing degree of solvent associaton We consider this to be a clear demonstration of the versatility of Cu(II) and its ability to coordinate and uncoordinate solvent or substrate molecules which is believed to be a fundamental and necessary property of copper-based enzymes.[12]. Barut et al.: Synthesis, X-ray Structural and Thermal Analysis
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