Rainer Glaser

Associate Professor

Diplom, Eberhard-Karls Universität, Tübingen, F.R. Germany, 1984
PhD, University of California-Berkeley, 1987
Postdoctorate, Yale University, 1987-89

Research areas: Theoretical and physical organic chemistry; deamination reactions; phosphorus chemistry; topological molecular orbital theory

(573) 882-0331; chemrg@showme.missouri.edu

Basic Philosophy: Fruitful Interplay Between Theory & Experimentation. We are studying topics in organic, organometallic, and bio-organic chemistry with modern theoretical methods in combination with laboratory experimentation. Several projects are pursued in collaboration with groups elsewhere in the US and in Europe creating opportunities for student exchanges. The interdisciplinary approach to pertinent problems exposes students to a broad spectrum of diverse techniques and provides a unique preparation for careers in modern research areas positioned at the interphases between the classical disciplines.

Development & Application of Theoretical Methods. We emphasize Cartesian space electron and spin density analysis to study bonding and most of our developmental efforts are dedicated to advancements in this area. We focus on ab initio methods achieving high accuracy with perturbational approaches (MP, G1, G2), density functional theory (DFT), and CI methods (CASSCF, QCISD). Semi-empirical formalisms and molecular mechanics are used sporadically as well. Current developments focuses on density based electrostatic methods for the study of DNA stacking and intercalation. Our recently developed density analysis methods for radicals are now being employed to investigations of radical reaction mechanisms and novel materials, to atmospheric radical chemistry, and to ESR spectroscopy. Our interest in fundamental bonding theory concerns aspects of dative bonding and analyses of energy distributions in molecules via fragment transfer energy analysis.

Deamination Chemistry: Nucleic Acid Alkylation & Cross-Linking. We have been interested in two types of deaminations and their relation to modifications of DNA bases. The first type relates to the deamination of amines (and derivatives) and their role in the alkylation of DNA. The other relates to the deamination of amino groups in DNA bases. Both of these processes have important biological consequences. In this context, we have been studying decomposition pathways "from the bottom up" beginning with diazonium ions. We proposed a new bonding model and established crucial links between theory and experiment. Current studies of diazonium ions focus on the mechanisms of their SN chemistry and studies of the diazonium ions of DNA bases. To address questions as to the consequences of alkylation on DNA and RNA structure and properties, our initial studies have focused on studies of base pairing.

Non-Synergistic Bonding & Thymine Dimerization. Our analysis of H-bonded Adenine-Thymine, A=T, suggests that A is stabilized in A=T while T is significantly destabilized. The notion of such "non-synergistic bonding", that is, the destabilization of a molecule by non-covalent association with another molecule without charge transfer, offers exciting prospects for catalysis. Current research focuses on detailed analyses of the origins for non-synergetic bonding. Experimental tests of this theoretical result focus on physical organic studies of the thymine dimerization, a process that also is of significance in the context of UV damage to DNA.

N-Perturbed Extended pi-Systems in Azines: Crisscross Reactions & Nonlinear Optical Materials. The stereochemistry and stereoelectronics are studied of push-push, pull-pull, and push-pull azines X-Ph-(R'C=CR")n-CR=N-N=CR-(R"C=CR') n-Ph-Y. These azines are important to advancing crisscross reaction chemistry, that is, the tandem 1,3-dipolar cycloaddition of azines with dienophiles and they show promise as novel nonlinear optical materials. In particular, we have found that one of these azines is highly dipole parallel-aligned in the crystal and indeed the such a degree of ferroelectric alignment is unprecedented and was thought to be impossible to achieve. The lattice architecture of the prototype is now being studied in great detail in collaboration with mathematicians.

New Electron-Deficient Materials: Diphosphonium Ions & Polycharged High-Multiplicity Ions. Our work suggests that the P analogues of RNN+ might exist. The experimental approach to diphosphonium ions primarily focuses on the Lewis-acid assisted ionization of polar diphosphenes. In collaboration with inorganic chemists, we are studying the oxidation of group VIb stabilized carbenium ions to polycharged radicals [C(XR)3]y+ (X = S, Se, Te, y = 1-3). State-of-the-art theory (QCISD(T) PES) indicates novel and unexpected properties which are now being explored more fully.

Selected Publications:

(1) "Spin Polarization versus Spin Delocalization." R. Glaser and G. S.-C. Choy J. Chem. Phys. 1994, 98, 11379-11393, and our publications cited there.

(2) (a) "Benzenediazonium Ion. Generality, Consistency, and Preferability of the Electron Density Based Dative Bonding Model." Glaser, R. and Horan C. J. J. Org. Chem. 1995, 60, 7518-7528. (b) "Importance of the Anisotropy of Atoms in Molecules." R. Glaser & G. S.-C. Choy J. Am. Chem. Soc. 1993, 115, 2340-2347.

(3) (a) "Crystal Structure of Fe(CO)3(PPh3)2 and ab Initio Study of the Bonding" R. Glaser, Y.-H.Yoo, G. S. Chen, and C. L. Barnes Organometallics 1994, 13, 2578-2586. (b) "Electron Density Distribution of beta,beta-Dichlorovinyldiazonium Ion." G. S. Chen, R. Glaser, and C. L. Barnes J. Chem. Soc., Chem. Commun. 1993, 1530-1532.

(4) (a) "Push-Pull Substitution versus Intrinsic or Packing Related N-N Gauche Preferences in Azines. Synthesis, Crystal Structures and Packing of Asymmetrical Acetophenone Azines." G. S. Chen, J. K. Wilbur, C. L. Barnes, and R. Glaser J. Chem. Soc., Perkin Trans. 2, 1995, 2311-2317. (b) "Polymorphism and Conformational C=N-N=C Bond Isomers of Azines." G. S. Chen, M. Anthamatten, C. L. Barnes, and R. Glaser Angew. Chem. Int. Ed. Engl. 1994, 33, 1081-1083.

(5) (a)"Tris(chalogeno)carbenium-Ionen C(XR)3+ (X = O, S, Se, Te)." D. Ohlmann, C. M. Marchand, H. Grützmacher, G. S. Chen, D Farmer, R. Glaser, A. Currao, R. Nesper, and H. Pritzkow Angew. Chem. Int. Ed. Engl. 1996, 35, 300-303. (b) "Phosphorus Analogues of Diazonium Ions." R. Glaser, C. Horan, and P. Haney J. Phys. Chem. 1993, 97, 1835-1844.