Complexing Properties of 2-Hydroxy-5-Ethylphenylphosphonic Acid (H3L). Crystal Structure and Analgesic Activity of [Cu(H2L)2(Н2О)2]

Complex [Cu(H 2 L) 2 (Н 2 О) 2 ] has been obtained by the reaction of copper(II) with 2-hydroxy-5-ethylphenylphosphonic acid (H 3 L), and its structure was studied by X-ray diffraction. Protonation constants of acid H 3 L and stability constants of its complexes with Cu 2+ in water have been determined by potentiometric titration. Complex [Cu(H 2 L) 2 (Н 2 О) 2 ] has been found to show low toxicity and high analgesic activity.