SYNTHESIS AND CHARACTERIZATION OF Co(II,) Ni(II) AND Cu(II) COMPLEXES WITH 1-HYDRAZINOPHTHALAZINE BASED LIGAND

Abstract

1-Hydrazinophthalazine (hydralazine) has been used over 50 years as an arterial vasodilatator. Despite of this long period, the coordination ability of hydralazines to transition metals is poorly investigated. Accordingly, our aim was to synthesize a new polydentate hydralazine-type ligand and to test its reactivity toward transition metal ions. With carbonyl compounds 1-hydrazinophthalazine reacts readily giving Schiff bases. Its reaction with 2,6-diacetylpyridine results in bis(phthalazine-1-hydrazone)-2,6-diacetyl-pyridine dihydrochloride. The new ligand with Co(II,) Ni(II) or Cu(II) acetate forms dark brown crystalline compounds. The crystal and molecular structure of the complexes was determined by single crystal X-ray diffraction. It was found that the ligand is coordinated to the central atoms in its monodeprotonated form, in a tetradentate NNNN fashion. Cobalt(III) and nickel(II) crystallizes with one methanol molecule. In the neutral octahedral Co(III) complex the hydralazine ligand occupies the equatorial plane while the chlorido ligands are in the axial positions. The ligand with Ni(II) gives complex cation of a square planar geometry. The electroneutrality of the complex is completed with a chloride contraion. In the reaction with Cu(II) a square pyramidal neutral complex is formed with a chlorido ligand in the apical position. This compound does not contain enclathrated solvent molecules. The complexes were characterized also by IR spectrometry, conductometric measurements and thermal analysis.