Study of complexation between Cu2+ ions and ortho-azidobenzoic acid

An aqua complex of copper(II) o-azidobenzoate, [Cu(OH)ABA⋅2H2O]2 (ABA is o-azidobenzoic acid), was synthesized in an aqueous solution and identified by IR and electronic absorption spectroscopy. In the complex, the azido group is not coordinated by Cu2+. When dissolved in dry organic solvents (DMF, DMSO, dioxane, and methanol), the complex undergoes dehydration to give a chelate complex (CC) containing the Cu2+-coordinated azido group as a result of the electron density redistribution at its N atoms. The IR spectrum of the chelate complex contains no absorption band at 2135 cm−1 corresponding to the stretching vibrations of the azido group. The resulting CC is unstable in solutions and spontaneously decomposes with a release of molecular nitrogen. The interaction of a Cu2+ ion with o-azidobenzoic acid in dry organic solvents affords a CC similar to the complex obtained on the dissolution of [Cu(OH)ABA⋅2H2O]2 in dry solvents.