Structural and thermal properties of three cyano-substituted azoderivatives of β-diketones

Abstract

3-(2-Cyanophenylhydrazo)pentane-2,4-dione (HL 1), 3-(4-cyanophenylhydrazo)pentane-2,4-dione (HL 2) and 1-ethoxy-2-(4-cyanophenylhydrazo)butane-1,3-dione (HL 3), and the Pd(II) complex [Pd(L 2) 2] were synthesized and characterized by IR, 1H and 13C NMR spectroscopies, ESI-MS, elemental and X-ray diffraction analyses (for HL 1). HL 3 derived from the unsymmetric 1-ethoxybutane-1,3-dione exists in solution as a mixture of the enol-azo and hydrazo tautomeric forms and a decrease of the solvent polarity shifts the tautomeric balance to the hydrazo form, while for HL 1 and HL 2, derived from the symmetric pentane-2,4-dione, the hydrazo form is dominating under all the studied conditions. HL 1–3 and [Pd(L 2) 2] show a high thermal stability with well-defined peaks of phase transition at 438 (HL 1), 462 (HL 2), 392 (HL 3) and 404 K ([Pd(L 2) 2]).