Abstract
A copper(II) complex with 6-hydroxypicolinic acid (6-OHpicH) and 3-picoline (3-pic), [Cu(6- OHpic)2(3-pic)2] (1), was prepared by recrystallization of [Cu(6-OHpic)2(H2O)2] from 3- picoline and characterized by IR spectroscopy and thermal methods (TGA/DTA and DSC). The molecular and crystal structure of 1 was determined by single-crystal X-ray structural analysis. The copper(II) ion in 1 has a tetragonally compressed octahedral coordination environment, achieved by two N, O-bidentate 6-hydroxypicolinate ligands and by two 3-picoline molecules in trans positions. The crystal structure of 1 exhibits one strong intermolecular O–H...O hydrogen bond, one weak intermolecular C–H...O hydrogen bond and one C– H...π interaction. Molecules of 1 are assembled into a 2D network in the (1 0 -1) plane, giving rise to C11(8) graph-set motif. These 2D networks are further assembled into 3D architecture only by weak Van der Waals interactions. A thermogravimetric study showed the initial loss of two coordinated 3-picoline molecules in 1, followed by a complete decomposition of the compound.
Highlights
Metal complexes of pyridine-2-carboxylic acid have been widely studied as well as those of its derivatives with electron-withdrawing substituents, such as hydroxyl groups or halogen atoms, due to their great coordination flexibility and wide variety of physiological properties, especially insulinomimetic activity.[1,2,3,4,5,6,7] Until now, there are only few reports regarding insulinomimetic properties of picolinate complexes bearing electron-donating groups such as a methyl group.[3, 8]Picolinate ligands favor the formation of mononuclear or polynuclear complexes due to their inherent tendency to form a chelate ring
The complex was characterized by IR spectroscopy and thermal methods (TGA/DTA, DSC) and its molecular and crystal structure was determined by single-crystal X-ray structural analysis
Complex 1 decomposes by prolonged standing in air due to release of coordinated 3-picoline molecules. It is soluble in solvents with pronounced donor properties, such as N,N-dimethyl-formamide, dimethylsulfoxide, pyridine and 3-picoline
Summary
Metal complexes of pyridine-2-carboxylic acid (picolinic acid, picH) have been widely studied as well as those of its derivatives with electron-withdrawing substituents, such as hydroxyl groups or halogen atoms, due to their great coordination flexibility and wide variety of physiological properties, especially insulinomimetic activity.[1,2,3,4,5,6,7] Until now, there are only few reports regarding insulinomimetic properties of picolinate complexes bearing electron-donating groups such as a methyl group.[3, 8]Picolinate ligands favor the formation of mononuclear or polynuclear complexes due to their inherent tendency to form a chelate ring. A lot of copper(II) complexes with picolinic acid derivatives and N-donor ligands (pyridine, 4-picoline, 3-picoline) are known from the literature. The complex was characterized by IR spectroscopy and thermal methods (TGA/DTA, DSC) and its molecular and crystal structure was determined by single-crystal X-ray structural analysis.
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