### Current and Past Research Projects at CATCO in Short

#### Method Development

**Density Functional Theory for Multi-Reference Systems**

Broken-Symmetry UDFT, Restricted Open-Shell Singley (ROSS)-DFT, Restricted Ensemble Kohn-Sham (REKS)-DFT, Complete Active Space (CAS)-DFT; Investigation of the problem of double counting of correlation effects.**Self-Interaction Corrected (SIC) DFT**

Investigation of the self-interaction error; SIC-DFT for small and large molecules; correct description of odd-electron bonds; investigation of the XC hole; intraelectronic and interelectronic exchange effect.**DFT Calculation of Magnetic Properties**

DFT methods for calculating magnetic shieldings and magnetizabilities; DFT methods for calculating spin-spin coupling constants; relativistic corrections for magnetic shieldings and spin-spin coupling constants.**Investigation of the Spin-Spin Coupling Mechanism**

Development of the J-OC-PSP method (decomposition of J into orbital contributions using orbital currents and partial spin polarization); investigation of Fermi contact coupling, spin dipole coupling, paramagnetic and diamagnetic spin-orbit coupling; influence of p-electrons on the coupling mechanism; graphical representation techniques of Ramsey spin densities and energy densities.**Relativistic Theory**

Development of quasirelativistic methods to be used for DFT, MBPT, and Coupled Cluster theory; gauge-independent ZORA and IORA; IORAmm; relativistic calculation of geometries, electric properties, magnetic shielding ESR-hyperfine spin coupling constants and NMR spin-spin coupling constants using analytical energy derivatives.**Many Body Perturbation Theory - Highly Correlated WFT Methods**

MP5 and MP6, approximate MP6, Convergence of the MPn series, quasi-degenerate perturbation theory, GVB-MP, gradient techniques, scaling methods.**Coupled Cluster Methods - Highly Correlated WFT Methods**

Role of T and Q effects (CCSDT, CCSDTQ), size-extensive QCISDT, QCISDTQ; CC methods correct in sixth order; spin-projected CC.**Methods for Analytical Gradients**

MP gradients and CC gradients, gradients for GVB-MP; gradients for relativistic methods.**Development of QM/MM methods**

Problem of the dangling bonds; force fields for specific molecules; inclusion of methods developed under 1.1 and 1.5.**Methods for Analyzing and Correlating Vibrational Spectra**

Development of methods to determine local adiabatic modes; adiabatic mode analysis; methods for the correlation of vibrational spectra; and CNM (characterization of normal mode) methods.**Methods for Calculating Conformational Changes**

Ring puckering coordinates; coordinates for describing bond pseudorotation; development of potential functions for puckered rings, geminal double rotors, etc.; DORCO: determination of ring conformations via NMR spin-spin coupling constants in an automated way; derivation of generalized Karplus curves.**Methods for Investigation of the Dynamics of a Chemical Reaction**

Extension of the Reaction Path Hamiltonian and the reaction valley approach; analysis of the reaction path curvature and mode coupling; direct reaction dynamics; URVA: united reaction valley approach.

#### Molecular Properties

**Calculation of Molecular Geometry and Conformation**

Using correlation corrected WFT methods or DFT; investigation of pseudorotating rings.**Calculation of Energetic Properties**

Using correlation corrected WFT methods or DFT; investigation of potential energy surfaces of small molecules; determination of thermochemical properties.**Calculation of Electron Density Distributions**

Using correlation corrected WFT methods or DFT; topological analysis and virial partitioning; investigation of energy density distribution and Laplace concentration.**Calculation of Properties of the Vibrating Molecule**

Using correlation corrected WFT methods or DFT; calculation of harmonic vibrational frequencies and infrared intensities; isotope effects; local mode analysis.**Calculation of Magnetic Properties**

Calculation of magnetic shieldings and chemical shifts using HF-IGLO, DFT-IGLO, GIAO or GIAO-MP methods; calculation of magnetic susceptibilities and susceptibility exaltations; CC and DFT calculation of spin-spin coupling constants.

#### Chemical Substance Classes

**Investigation of Carbocations**

NMR chemical shifts in gas phase and solution, stability, structure, reactivity; aromatic and homoaromatic carbocations; application of NMR/ab initio/chemical shift methods.**Investigation of Silyl Cation**

Structure and stability, calculation of^{29}Si chemical shifts, silylium cations, investigation of silylium cations in solution (interactions with solvents), bonding in silylium cation-solvent complexes.**Investigation of Peroxides and Polyoxides**

Investigation of the ozonolysis of alkenes and alkines; ozonides, organic and inorganic peroxides, carbonyl oxides and dioxiranes; carbene-oxygen reactions.**Investigation of Strained Molecules**

Three-membered rings in particular cyclopropyl derivatives; anti-Bredt compounds; theory of ring strain; steric repulsion and steric attraction (cis-effect).**Investigation of Biradicals**

Structure and stability of dehydrobenzenes; products of the Myers cyclization; dioxymethanes; oxythiamethanes.**Investigation of Tin Compounds**

Structure and stability of stannanes and stannyl cations; calculation of d119Sn chemical shifts; free stannylium cations in solution.**Investigation of van der Waals Complexes**

Structure and stability of Ar-complexes with aromatic molecules; oxygen and ozone complexes with alkenes and aromatic molecules; electron density description.**Investigation of Frozen Transition States**

Stabilization of transition states by substituents; homoaromatic carbocations; substituted semibullvalenes.

#### Drug Design and Biochemically Relevant Topics

**Investigation of Naturally Occurring Enediynes**

Structure and stability of triggered and un-triggered dynemicin; stereoisomers of calicheamicin; investigation of its aglycone.**Development of a New Antitumor Drug**

Development of a drug design strategy; new warheads for enediynes; pH-dependence of the triggering of the warhead; construction of the real drug; favorable docking modes; calculation of binding energies; determination of DNA cleavage sites.**Susceptibility of Proteins to Enediyne Ligands**

Protein damage as an alternative to DNA cleavage; design of proteinophilic enediynes.**Generation of Acrylamid in Food**

Condition, mechanism, genotoxicity, carcinogenicity and adduct formation, investigation of the Maillard reaction.**Investigation of the Nerve Gases Sarin and Soman**

Structure, stability and toxicity; detection by NMR spectroscopy.**Toxin Ricin - One of the Most Toxic Compounds**

Investigation of the possibility to use this compound as new anticancer drug.**Virtual Screening**

Encoding of chemical information in bit strings.**Investigation of the Anti-Malarial Drug Artemisinin**

Stability and conformation; lability of the peroxidic group; reactions with Fe ions; reaction with the heme group.

#### Heuristic Models and Concepts

**Theory of the Chemical Bond**

Electron Density Analysis, Investigation of Laplace concentrations and energy density distributions; derivation of bond properties from vibrational frequencies and infrared intensities.**Concept of Aromaticity and Homoaromaticity**

Problem of selecting references; description with geometric, energetic and magnetic properties of molecules; electron density description; s-aromaticity.**Concept of Molecular Strain**

Calculation of molecular geometries for gas and solution phases; calculation of infrared and NMR signals based on ab initio and DFT optimized geometries.

#### Chemical Disciplines

**Structure Elucidation of Molecules**

Calculation of molecular geometries for gas and solution phases; calculation of infrared and NMR signals based on ab initio and DFT optimized geometries.**Stability Analysis of Molecules**

Rationalization of molecular stability by conjugation, hyperconjugation, anomeric effect, homoconjugation, etc. using MO models and electron density distribution.**Elucidation of Reaction Mechanism**

Pericyclic reactions in particular [2+2] and [4+2] cycloadditions; valence isomerization, substitution reactions, solvent effects; energy transfer and energy dissipation; Bergman and Myers cyclization; ozonolysis reaction and other oxidation reactions.**Solvation and Solvent Effects**

Geometries, energies and magnetic properties of molecules in solution; interactions of carbocations and silylium cations with various solvents.**NMR Spectroscopy**

NMR chemical shifts by IGLO, GIAO, SOS-DFT, magnetic susceptibilities, NMR/ab initio/Chemical Shift methods for the determination of molecular geometries in solution, correlation between spin-spin coupling constants and molecular geometry; Karplus curves.**Infrared Spectroscopy, in particular Matrix Isolation Spectroscopy**

IR determination of labile compounds, reaction mechanism, adiabatic analysis.**Microwave Spectroscopy**

Investigation of argon van der Waals complexes; investigation of ozone complexes.**Inorganic Chemistry**

Investigation of tin compounds: stannanes, stannylium cations; investigation of sulfur compounds: sulfanes, organo sulfur compounds; investigation of Ti compounds.**Biochemistry**

Anticancer drugs, reaction mechanism enediyne cytostatica and antibiotics; Bergmann and Myers cyclizations; structure and stability of biradicals that attack DNA.**Reaction Dynamics**

Reaction Path Hamiltonian, Direct dynamics, RRKM calculations; adiabatic mode analysis, electron density analysis; investigation of substitution reactions; investigation of pericyclic reactions.**Atmospheric Chemistry**

OH production, Ozonolysis, Carbonyl oxides, reaction mechanism, dioxirane reactions.