engleski

Influence of intramolecular hydrogen bonding on structures and thermal stability of Cu(II) and Zn(II) β-diketonate adducts

In order to study the effect of intramolecular hydrogen bond on the stability of adducts of nitrogen bases with coordinatively unsaturated metal complexes, a series of Cu(II) and Zn(II) β-diketonates were crystallised from three solvents (pyridine, morpholine and 2-amino-3- picoline) which can act as additional ligands, but differ in their potential for forming an intramolecular hydrogen bond. From the solutions in 2-amino-3-picoline, 7 metal diketonate adducts crystallised, while crystallisation from pyridine and morpholine yielded only 3 and 2 adducts respectively. Overall, twelve Cu(II) and Zn(II) β-diketonate adducts with general formula [M(dkt)2(L)n] (n = 1, 2) have been prepared, and their crystal structures were determined. Metal centers in the prepared compounds are penta- or hexacoordinated with octahedral, square- pyramidal and trigonal-bipyramidal geometries. In all 2-amino-3-picoline adducts there is an intramolecular hydrogen bonding between the amino group and diketonato oxygen atoms. In adducts with morpholine the hydrogen bond donor and acceptor sites are in an unfavorable relative position to each other, which prevents formation of a strong and stabilizing intramolecular interaction. Consequently, it has been shown that adducts with 2-amino-3- picoline are easily prepared and more stable than adducts with morpholine or pyridine.

Hydrogen bonding, metal complexes, complex stability

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