Tautomerizations of 2-, 3-, and 4-formylpyridine semicarbazone conformers in gas and aqueous phases

The search for possible conformations of 2-formylpyridine (H2FoPyS), 3-formylpyridine (H3FoPyS), and 4-formylpyridine (H4FoPyS) semicarbazones was carried out using potential energy surface method at the B3LYP/6-31G(d) level of theory. Thermodynamic quantities of amino-imino tautomerizations of the most stable conformers for H2FoPyS (o-Atctcc), H3FoPyS (m-Acttcc), and H4FoPyS (p-Atttcc) determined via the transition states with and without water-assisted proton transfers, derived from the frequencies calculations at the B3LYP/6-311++G(d,p) level in gas and aqueous phases are reported.     

A DFT investigation on molecular structures of semicarbazone complexes with Co(II), Ni(II) and Zn(II) and reaction energies of their complexation

The structure optimizations of 2-formylpyridine (H2FoPyS), 3-formylpyridine (H3FoPyS), and 4-formylpyridine (H4FoPyS) semicarbazone complexes with Co(II), Ni(II), and Zn(II) were carried out using DFT calculations at the B3LYP/LANL2DZ level of theory. The B3LYP/LANL2DZ-optimized geometry parameters for the H2FoPyS and H3FoPyS complexes show good agreement with their corresponding X-ray crystallographic data. Due to the X-ray crystallographic structures of the [Zn(H3FoPyS)₂]²⁺ complex and the H4FoPyS complexes with Co(II), Ni(II), and Zn(II) and have not yet been observed, their B3LYP/LANL2DZ-optimized structures are therefore theoretically proposed. The reaction energies and thermodynamic properties of complexation for these complexes computed at the same level of theory are reported.