Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1410427 | Journal of Molecular Structure | 2009 | 6 Pages |
Abstract
Hydrogen bonding in salicylaldehyde-4-phenylthiosemicarbazone (1) has been studied by using experimental (NMR, Raman and UV spectroscopies) and quantum chemical (DFT) methods. It has been demonstrated that 1 adopted the hydroxy-thione tautomeric form in solution as found also in the solid state and previously indicated by secondary deuterium isotope effects. Apart from the intra-molecular hydrogen bonds new interactions between 1 and solvent molecules were formed as well. Changes in NMR chemical shifts and calculations have pointed towards a formation of inter-molecular three-centered hydrogen bonds in each of the studied complexes involving OH and NH groups of 1 and associated solvent molecules. Stabilization energies of intra-molecular hydrogen bonds were found to decrease with the increase of the solvent polarity. Two-dimensional NOESY spectra indicated conformational changes in solution with respect to the structure observed in the solid state. These were accounted for by a relatively low barrier of the rotation of the NN single bond thus enabling a molecule to posses a higher conformational flexibility in solution with portions of skewed conformations. The results presented here can help in a better understanding of the role hydrogen bonds can play in bioactivity of related thiosemicarbazone derivatives and their metal complexes.
Related Topics
Physical Sciences and Engineering
Chemistry
Organic Chemistry
Authors
Predrag Novak, Katarina PiÄuljan, Tomica Hrenar, Tomislav Biljan, Zlatko MeiÄ,