Cu(II), Ni(II) and Co(II) co-ordination properties and tautomerism of 1,8-bis-phenylazo-2,7-dihydroxy naphthalene. A spectroscopic and semiempirical AM1/PM3 study

Abstract

As a continuation of a study on the prototropic properties of aromatic α,α′-dihydroxy-bis-azocompounds, 1,8-bis-phenylazo-2,7-dihydroxynaphthalene (PHADN) has been studied through 1H and 13C nuclear magnetic resonance experiments, electronic absorption and semiempirical molecular orbital methods. In addition, the metal binding properties of this compound were evaluated and related with its tautomeric forms. The equilibrium constants for Cu(II), Ni(II) and Co(II)–PHADN complexes were spectrophotometrically determined in dioxane–water 50% v/v solutions. The structures of the evaluated chelates were proposed on the basis of spectral analysis and PM3 semiempirical calculations.