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Study of the molecular and crystalline structure of two nitrogen- sulphur pro-ligands by x-ray powder diffraction and DFTB

Edward E. Ávila 1Asiloé J. Mora 1Andy Fitch 2Michela Brunelli 3Gerzon E. Delgado 1Ricardo R. Contreras 4Luis C. Rincón 5

1. Universidad de Los Andes, Facultad de Ciencias, Laboratorio de Cristalografía, Merida 5101, Venezuela
2. European Synchrotron Radiation Facility (ESRF), Grenoble 38043, France
3. Europen Synchrotron Radiation Facility (ESRF), 6, Jules Horowitz, Grenoble 38000, France
4. Universidad de Los Andes, Facultad de Ciencias, Laboratorio de Organometálicos, Merida 5101, Venezuela
5. Universidad de Los Andes, Facultad de Ciencias, Grupo de Procesos Dinámicos en Química, Merida 5101, Venezuela


In the last decades, inorganic chemist has faced the need to mimic the properties of metal sites in metalloproteins to synthesize new catalytic materials with advantageous properties [1].  However, one of the mayor difficulties in the synthesis of these materials has been to prepare pro-ligands with structural conformations and chemical properties close enough to the ligands around the metal in the protein to avoid problems associated with molecular recognition in the catalytic process. In this work, we have attempted to study the molecular and crystalline structure by means of X-ray powder diffraction and theoretical calculations using density functional tight-binding methods (DFTB) of two new pro-ligands  of the type [NS] bidentate and [N2S2] tetradentate: iso-butyl 2,4-bis(cyclohexane)dispiro-[1,2,3,4,4a,5,6,7]-octahydro-(1H,3H)quinazoline-8-carboxydithioate (compound I)  and methyl N,N'-buthyl-bis(2-amino-1-cyclopentendi-thiocarboxidithioate (compound II) [2-4]. Powder diffraction experiments were carried out in the diffractometer of beam line ID31, ESRF, France. DFTB calculations were carried out using the computer facilities of the Theoretical Chemistry Group: Dynamical Processes, ULA, Venezuela. The structural solution was achieved using the program FOX. The Rietveld refinement of the models used the program GSAS. The molecular conformation for both compounds, which are subjected to internal hydrogen bonds and electron charge delocalization in the carboxydithioate group, and the crystal packing of the compounds are thoroughly discussed here. Finally, the molecular structures obtained by X-ray powder diffraction are compared with the ones optimized by DFTB calculations.

Acknowledgement: This study was supported by the CDCHT-ULA, FONACIT-Venezuela (Lab-97000821, Subvention-200500703) and beam line ID31, ESRF (France).


  1. Solomon, E. I., Szilagyi, R. K., DeBeer, G. S. & Basumallick, L., 2004, Chem. Rev. 104, 419-458.
  2. Avila, E.E., Mora, A.J., Delgado, G.E., Contreras, R.R., Fitch, A.N. & Brunelli, M. 2008, Acta Crystal. B64, 217-222.
  3. Contreras, R. R., Fontal, B., Romero. I., Briceño, A. & Atencio, R., 2006, Acta Cryst. E62, o205-o208.
  4. Contreras, R. R., Fontal, B., Bahsas, A., Reyes, M., Suárez, T. & Bellandi, F. 2001, J. Heterocycles Chem. 38, 1223-1225.

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Submitted: 2008-05-01 01:37
Revised:   2009-06-07 00:48