PHYSICAL ORGANIC & COMPUTATIONAL CHEMISTRY

First row (left to right, seated): Valentin Monev, Nadya Tabakova, I. Pojarlieff, Milena Spassova, Stefan Stanchev

Second row: Assen Koedjikov, Jose Kaneti, Martin Gotsev, Martin Kotev, Petko M. Ivanov

kinetics, ab initio MO calculations, molecular mechanics, conformational analysis, reactivity, mechanisms, molecular design

Laboratory founder: Ivan G. Pojarlieff, Professor Emeritus, Dr.Sci., BAS Corr. member

Laboratory members

• Dr. Petko M. Ivanov, Res. professor
• Dr. Jose Kaneti, Res. professor
• Dr. Snezhana Bakalova, Assoc. professor
• Dr. Assen Koedjikov, Assoc. professor
• Dr. Valentin Monev, Assoc. professor
• Dr. Milena Spassova, Assoc. professor
• Dr. Nadezhda Tabakova, res. fellow
• Mr. Martin Gotsev, PhD student
• Mr. Martin Kotev, PhD student
• Mr. Stefan P. Stanchev

Main Research Topics

• Kinetics and thermodynamics of reactions in solution, general acid-base catalysis.
• Mechanism of organic reactions, sterically strained models of biorganic reactions
• Quantitative correlation of reactivity, steric effects in particular.
• Organic synthesis
• Reactions in organized media
• Ab initio MO and DFT studies of molecular structure, reactivity and reaction mechanisms, molecular design
• Computational conformational analysis, modelling structure and dynamics of organic molecules

Main Results

• One of the main research projects of the laboratory has centered on bioorganic models particularly of biotin mediated acyl transfers. Sterically strained substrates by means of the gem-dimethyl effect bring about rate enhancements up to six powers of ten thus allowing model reactions to be studied under mild conditions where biologically relevant mechanisms such as general acid-base catalysis can be studied. One early result showed the importance in the transition state of proton transfer to the carbonyl oxygen in N-acylation of urea by carboxylate. Recent work has unraveled the intricate interactions of the gem-dimethyl effect and steric hindrance to proton transfer which cause unexpected changes of mechanism and reactivity in cyclizations of hydantoic esters and amides.
• The above studies have been expanded to micellar systems providing understanding of the effect of microenvironment. Micelles with reactive counterions are of particular interest, in identifying specific effects of buffer concentration in micellar media. General base catalysis at the micellar interface is favoured by about two orders of magnitude over the specific base catalysis. A rigorous pseudophase treatment has been proposed for the water-promoted reaction of bromine and 1-octene in reverse micelles.
• Another direction of research is computational conformational analysis: new parameterizations for molecular mechanics force fields have been developed for modeling dicarboxylic anhydrides, cyclopropanes, compounds with phenyl groups on neighbouring carbon atoms. MM study of the gem-dimethyl effect and steric effects in acyl transfers involving stereoelectronic effects should be mentioned. Computational protocols have been tested for the modeling and the MD simulation of the inclusion processes of small organic molecules with macrocycles. Algorithms and software have been developed for the molecular mechanics modeling of molecular crystals with full geometry optimization of the reference molecule.
• DFT and ab initio MO, including multiconfiguration and multireference, studies of molecular structure, spectra, ground and excited states, and reaction mechanisms: transition metals, concerted cycloadditions, e.g. of anhydrides to Schiff bases, Diels - Alder stereoselectivity and catalysis; phosphorus reaction mechanisms. Enzyme and supramolecular modelling. Computational design of drugs, fluorescent dyes and other optoelectronic materials.

Selected publications from the laboratory

1. Quantitatiive evaluation of the gem-dimethyl effect on the succinic acid - anhydride equilibria. Conformations of the acids and anhydrides by empirical force-field calculations. P. M. Ivanov and I. G. Pojarlieff, J. Chem. Soc., Perkin Trans., 2, (1984) 245.
2. Intramolecular nucleophilic attack on carboxylate by ureide anion. General acid-base catalysis of the alkaline cyclization of 2,2,3,5-tetramethylhydantoic acid. I. B. Blagoeva, I. G. Pojarlieff and A. J. Kirby, J. Chem. Soc., Perkin Trans., 2, (1984) 745
3. Leffler relationship of the gem-dimethyl effect. I. B. Blagoeva and I. G. Pojarlieff and V. T. Rachina, J. Chem. Soc., Chem. Comm., (1986) 946.
4. General Acid-Base Catalysed Cyclisation Reactions of a Strained omega-Phenylhydantoic Acid. I. Blagoeva, J.Chem.Soc. Perkin Trans. 2, (1987), 127-134.
5. Pseudophase Model for Reactivity in Reverse Micelles. The Case of the Water Promoted Reaction between Two Lipophilic Reagents, Bromine and 1-Octene, in AOT Microemulsions. I.B.Blagoeva, P.Gray, M.F.Ruasse, J.Phys.Chem., 100 (1996), 12638.
6. Computational Study on the Ring Distortions of 1,4-Dicyanobenzene in the Gas Phase and in the Crystal, P. M. Ivanov, J. Mol. Struct., 440 (1998) 237-246.
7. 1H NMR Spectra and Structure of Safranines. Hindered Rotation of the Dialkylamino Group in Azo Derivatives, L.I. Proevska and I.G. Pojarlieff, Dyes and Pigments, 36 (1998) 177-190.
8. On the disappearance of the gem-dimethyl effect in the base-catalysed cyclization of ethyl hydantoates. Ergun Atay, Iva B. Blagoeva, Anthony J. Kirby and Ivan G. Pojarlieff, J. Chem. Soc., Perkin Trans. 2, (1998) 2289-2297.
9. A CAS SCF Study of the Reaction Mechanism of the Alpha-Alkynone Rearrangement, J. Kaneti, Helv. Chim. Acta 2000, 83/4, 836-842.
10. Fluorinated Alcohols Enable Olefin Epoxidation by H2O2: Template Catalysis, S. P. de Visser, Jose Kaneti, R. Neumann, S. Shaik: J. Org. Chem. 2003, 68(7), 2903-2912.
11. Schiff Base Addition to Cyclic Carboxylic Anhydrides - an Unusual Concerted Reaction. A MO and DFT Theoretical Study: J. Kaneti, S. Bakalova, and I. Pojarlieff, J. Org. Chem., 2003, 68(17), pp. 6824-6827.
12. Electronic Absorption and Emission Spectra and Computational Studies of Some 2-Aryl, 2-Styryl, and 2-(4.-Aryl)Butadienyl Quinazolin-4-ones: S. Bakalova, A. Gil Santos, I. Timcheva, J. Kaneti, I. Filipova, G. Dobrikov, and V. D. Dimitrov, J. Mol. Struct. THEOCHEM 2004, 710(1-3), 229-234.
13. Phenylacetyl arylamides as probes for the stereoselectivity of penicillin acylase from E.coli. Kinetic studies and molecular modelling: Maya Guncheva, Ivaylo Ivanov, Boris Galunsky, Nicolina Stambolieva,* and Jose Kaneti,* Eur. J. Biochem. 2004, 271(11), 2272-2279.
14. Origins of Stereoselectivity in the Diels-Alder Addition of Chiral Hydroxyalkyl Vinyl Ketones to Cyclopentadiene: A Quantitative Computational Study, Snezhana M. Bakalova and Jose Kaneti, J. Phys. Chem. A, 2008, 112(50), 13006-13016.
15. Design and Photophysical Properties of a New Molecule with a N-B-N Linked Chromophore: Snezhana Bakalova, Francisco Mendicuti, Obis Castano, and Jose Kaneti, Chemical Physics Letters 2009, 478, 206.210.
16. M. K. Georgieva, F. J. S. Duarte, S. M. Bakalova, A. Gil Santos, 1,5-Disubstituted Pyrrolidines as Chiral Auxiliaries in Radical Reactions: A Theoretical Approach, European Journal of Organic Chemistry 2010, 4841-4850
17. F. J. S. Duarte, S. M. Bakalova, E. J. Cabrita, A. Gil Santos, Lewis Acid Catalyzed Reactions of Chiral Imidazolidinones and Oxazolidinones: Insights on the Role of the Catalyst, Journal of Organic Chemistry 2011, 76(17), 6997 . 7004
18. S. M. Bakalova, A. G. Santos, Diels-Alder Reactions of Chiral Isoimidium Salts: A Computational Study, J. Org. Chem. 2014, 79, 8202-8211.
19. S. Nenon, B. Champagne, M. I. Spassova, Assessing long-range corrected functionals with physically-adjusted range-separated parameters for calculating the polarizability and the second hyperpolarizability of polydiacetylene and polybutatriene chains. Phys. Chem. Chem. Phys. 2014, 16, 7083-7088.

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Last updated Oct. 01, 2014