The Mixed Complex of Tetracycline-Metal Chelates. III. Chlorotetracycline-Metal Chelates with Isoniazid

Abstract

Isoniazid (INAH) was studied on the formation of mixed complexes with chloro tetracycline (CT)-metal chelates with Th⁴⁺, Fe³⁺, Cu²⁺, and Co²⁺ in acid medium. INAH-metal compounds were also studied. INAH-Cu (II) chelate, and INAH-Co (II) complex and its chelate were isolated as crystalline powder showing 1 : 1, 2 : 1, and 1 : 1 ratio of INAH to metal, respectively, from hydrous methanol. Molar ratio of the compounds in aqueous solution was measured by the continuous variation method. Iron(III) ion decomposed INAH to isonicotinic acid, but the mixed complex of CT-Fe (III) chelate with INAH was formed without decomposition. The mixed complex of CT-CO (II) with INAH gave different compositions in accordance with the acidity of the preparation. CT-Co (II) chelate formed a mixed complex, but not CT-Th(IV) chelate. The molar ratio of the mixed complexes was mostly 1 : 1 : 1 (CT : metal : INAH). These mixed complexes were isolated in crystalline powder form and were soluble in methanol and hot water. Remarkable changes in color due to the formation of a mixed complex were not observed. Reaction between INAH-metal and CT-HCl was also studied.