Computation Chemistry and Structure of Boranes
Contact person: D. Hnyk
Computational chemistry and molecular structure determinations of boranes, heteroboranes and metallaboranes are carried out on a few levels. The most important approach is based on computing various quantum-chemical observables, molecular geometries and shielding tensors prevailing. The latter forms building block for getting 11B chemical shifts computationally. Conceivably, 11B NMR spectroscopy is the structural method of choice for obtaining knowledge about architectures of this class of materials. Experimental 11B chemical shifts are confronted with this kind of chemical shifts derived computationally. Comparison of theoretical and calculated data subsequently indicates the correctness of a particular geometry in solution.
On the basis of cooperation with Institute of Organic Chemistry and Biochemistry of the ASCR, v.v.i. interactions of boranes, metallaboranes play the decisive role, with biomolecules, e.g. with HIV protease. Figure on left hand side illustrates such a mechanism of the interaction of metalacarbaboranes with peptides, the so called H…H hydrogen bond appearing to be responsible for such contacts. The understanding of this interaction is essential for designing pharmacological properties of boranes as a whole.
Experimental structural methods are based on very productive liaisons with the universities in Edinburgh and Oslo. Electron scattering experiments on gaseous boranes and heteroboranes, i.e. employing the technique of gas-phase electron diffraction, are run at Edinburgh and the data obtained are analysed at Rez. A few examples of such experimental structures are depicted in figure below. Moreover, comparison between the experimental and theoretical internal coordinates allows to test reliability of various computational protocols. Application of microwave spectroscopy, the second technique for determining the structures of free molecules, is done at Oslo. Both experimental approaches also utilize results from the aforementioned computations.
Selected papers include:
1. Bühl, M., Schleyer, P.v.R., Havlas, Z., Hnyk, D. and Heřmánek, S.: ON THE ORIGIN OF THE ANTIPODAL EFFECT IN CLOSO-HETEROBORANES, Inorg. Chem., 1991, 30, 3107 - 3111.
2. Brain, P.T., Cowie, J., Donohoe, D.J., Hnyk, D., Rankin, D.W.H., Reed, D., Reid, B.D., Robertson, H.E. and Welch, A.J.: 1-PHENYL-1,2-DICARBA-CLOSO-DODECABORANE, 1-Ph-1,2-CLOSO-C2B10H11. SYNTHESIS, CHARACTERIZATION, AND STRUCTURE AS DETERMINED IN THE GAS PHASE BY ELECTRON DIFFRACTION, IN THE CRYSTALLINE PHASE AT 199 K BY X-RAY DIFFRACTION, AND BY AB INITIO COMPUTATIONS, Inorg. Chem., 1996, 35, 1701 - 1708.
3. Štíbr, B., Tok, O.L., Milius, W., Bakardjiev, M., Holub, J. Hnyk, D. and Wrackmeyer, B.: THE [CLOSO-2-CB6H7]- ANION, THE FIRST REPRESENTATIVE OF THE SEVEN-VERTEX MONOCARBABORANE SERIES. ANOTHER STABLE CANDIDATE FOR WEAKLY COORDINATING ANION CHEMISTRY, Angew. Chem. Intl. Ed. Engl . 2002, 41, 2126-2128.
4. Bühl, M., Hnyk D. and Macháček J.: COMPUTATIONAL STUDY OF STRUCTURES AND PROPERTIES OF METALLABORANES: COBALT BIS(DICARBOLLIDE), Chem. Eur. J., 2005, 11, 4109-4120.
5. Bakardjiev, M., Holub, J., Hnyk, D., Císařová, I., Londesborough, M., Perekalin, D.S. and Štíbr, B.: STRUCTURAL DUALISM IN THE ZWITTERIONIC 7-RR’NH-NIDO-7,8,9-C3B8H10TRICARBOLLIDE SERIES: AN EXAMPLE OF ABSOLUTE TAUTOMERISM, Angew. Chem. Int. Ed., 2005, 44, 6222-6226.
6. Fanfrlík, J., Hnyk, D., Lepšík, M. and Hobza, P.: INTERACTION OF HETEROBORANES WITH BIOMOLECULES. PART 2. THE EFFECT OF VARIOUS METAL VERTICES AND EXO-SUBSTITUTIONS, Phys. Chem. Chem. Phys., 2007, 9, 2085-2093.
7. Pennanen, T.O., Macháček, J., Taubert, S., Vaara, J. and Hnyk, D.: FERROCENE-LIKE IRON BIS(DICARBOLLIDE), [3-FeIII-(1,2-C2B9H11)2]-. THE FIRST EXPERIMENTAL AND THEORETICAL REFINEMENT OF A PARAMAGNETIC 11B NMR SPECTRUM, Phys. Chem. Chem. Phys. 2010, 12, 7018-7025.
8. Hnyk, D., Wann, D., Holub, J., Samdal, S. and Rankin, D.W.H.: WHY IS THE ANTIPODAL EFFECT IN CLOSO-1-SB9H9 SO LARGE? A POSSIBLE EXPLANATION BASED ON THE GEOMETRY FROM THE CONCERTED USE OF GAS ELECTRON DIFFRACTION AND COMPUTATIONAL METHODS, Dalton Trans., 2011, 40, 5734-5737.
9. Hnyk, D. and Jayasree E.G.: CATIONIC CLOSO-CARBORANES 2. DO COMPUTED 11B AND 13C NMR CHEMICAL SHIFTS SUPPORT THEIR EXPERIMENTAL AVAILABILITY? J. Comput. Chem., 2013, 34, 656 – 661.