Group XIII.
CIRCULAR
DICHROISM SPECTROSCOPY IN STRUCTURE DETERMINATION
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Head of the group Prof. Jadwiga Frelek e-mail: frelek@icho.edu.pl |
1978 – Ph. D.; Department of Chemistry, University of Warsaw 1981 – 1983 – Post-doc., Ruhr-University Bochum, Germany 2000 – Habilitation, Institute of Organic Chemistry PAS 1976, 1980, 1988, 1989 – Awards of the Rector of Warsaw University |
Staff:
Patrycja Kowalska, Ph.D. student, Magdalena Woźnica, Ph.D. student, Marcin Górecki, graduate student, Agata Suszczyńska, M. Sc.
Research activities:
Our current research is directed towards three dimensional molecular structures elucidation of selected organic compounds in the solution or solid state by means of chiroptical methods, circular dichroism (CD) in particular. Currently we are focusing on the structure-chiroptical properties’ relationship of classical and non-classical β-lactam analogues, with an emphasis on carba-analogues of penicillin’s and cephalosporin’s.
Special attention is devoted to the stereostructure determination of transparent molecules. To fulfill the requirements of circular dichroism spectroscopy a chiral, nonracemic but transparent substance has to be transform into a chromophoric derivative. For this purpose, we developed a methodology which uses various complexes with two transition metal atoms linked together by a single or multiple bond of general formula M2(OCOR)4, with M = Mo, Rh, Ru or Re. These achiral complexes act as auxiliary chromophores. After the exchange of achiral ligands of the stock complex for different types of chiral ligands, e.g., amino acids, glycols, aminols, diamines, alcohols, amines, etc., optically active complexes are formed. CD of these complexes can easily be measured and used for the correlation between signs of Cotton effects (CEs) obtained and the structure of investigated compounds.
We also focused on the application of the solid state CD spectroscopy to structural studies. In the solid state, achiral molecules with some degree of restricted freedom, such as rotation and orientation about chemical bonds, may become optically active and thus can be studied by means of CD.
The experimental measurements as far as possible are combined with corresponding quantum mechanical predictions to establish the absolute configuration and/or determine the predominant conformations of chiral molecules in the solution phase.
Selected publications:
1. J. Frelek, W.J. Szczepek, S. Neubrecht, B. Schultheis, J. Brechtel, H.-G. Kuball – "Chiroptical properties of cisoid enones from CD and ACD spectroscopy" - Chemistry – Eur. J. 2002, 8, 1899-1907.
2. R. Łysek, K. Borsuk, M. Chmielewski, Z. Kałuża, Z. Urbańczyk-Lipkowska, A. Klimek, J. Frelek – "5-Dethia-5-Oxacephams: Towards Correlation of Absolute Configuration and Chiroptical Properties" - J. Org. Chem, 2002, 67(5), 1472-1479.
3. U. Siemeling, I. Scheppelmann, B. Neumann, A. Stammler, H.-G. Stammler, J. Frelek – "Spontaneous chiral resolution of a coordination polymer with distorted helical structure consisting of a achiral building blocks" – Chem. Commun. 2003, 2236-2337.
4. J. Frelek, A. Klimek, P. Ruśkowska - "Dinuclear Transition Metal Complexes as Auxiliary Chromophores in Chiroptical Studies on Bioactive Compounds" – Curr. Org. Chem. 2003, 7, 1081-1104.
5. J. Frelek, J. Jaźwiński, P. Ruśkowska, R. Szmigielski, M. Masnyk - "Dirhodium Tetraacetate as an Auxiliary Chromophore in the Circular Dichroic Assignment of the Absolute Configuration to vic-Amino Alcohols" – Tetrahedron: Asym. 2005, 16, 2437-2448.
6. J. Frelek, M. Górecki, J. Jaźwiński, P. Ruśkowska, R. Szmigielski, M. Masnyk - "Configurational Assignment of vic-Amino Alcohols from Their Circular Dichroism Spectra with Dirhodium Tetracetate as an Auxiliary Chromophore" – Tetrahedron: Asymmetry 2005, 19, 3188-3197.
7. K. Tanaka, T. Iwamoto, S.-I. Wada, J. Frelek, M.R. Caira - "Spontaneous resolution of 2,3-bis-fluoren-9-ylidenesuccinic acid induced by achiral guest inclusion" – Chirality, 2006, 18, 483-488.
8. J. Frelek, M. Górecki, A. Suszczyńska, Z. Maier - "Dimolybdenum tetraacetate as an auxiliary chromophore in absolute configuration determination of amino acids from their circular dichroism spectra – foundations and developments" – Mini Review Org. Chem. 2006, 3, 282-290.
9. M.Górecki, A. Kamińska, P. Ruśkowska, A. Suszczyńska, J. Frelek - "Dimolybdenum method for determination of the absolute configuration of vic-diols – Foundations and Developments" - Pol. J. Chem. 2006, 80, 523-534.
