Synthesis and characterization of two new hydroxamic acids derivatives and their metal complexes. An investigation on the keto/enol, E/Z and hydroxamate/hydroximate forms

2-phenylbenzimidazole-N-acetohydroxamic acid ( HL 1 ), 2-phenylbenzimidazole-N-butanohydroxamic acid ( HL 2 ) and Ni(II), Cu(II), Zn(II) and Cd(II) metal complexes have been synthesized and characterized by elemental analyses, 1 H NMR, 13 C NMR, FT-IR spectrometry, LC-MS (ESI + ) and thermal analyses. The results of NMR spectra and theoretical calculations showed that the hydroxamic acids were in the keto-E and keto-Z conformations. The elemental analysis and thermal analysis indicated that M:L ratio of the complexes are 1:1 and the spectral analysis confirmed that hydroxamate groups are keto form in the Ni(II) and Zn(II) complexes of 2-phenylbenzimidazole-N-butanohydroxamic acid and enol form in the other complexes.