CORRECTION TO NMR PARAMETERS VIA AVERAGING OVER THE MOLECULAR MOTION

Vladimír Sychrovský and Vladimír Špirko

Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10 Praha

NMR parameters are calculated usually for the optimal geometry of given molecule. This point-like geometry however need not necessarily correspond to the statistically significant distribution of atoms/nuclei in the space during the acquisition of NMR signal. When any NMR property involves large variation with respect to local geometry and the amplitudes of respective molecular motions are remarkable, the averaged NMR parameter can differ notably from the parameter calculated for the point-like geometry. Computational approach including anharmonic vibrational corrections is presented on three examples. Vibrational correction of NMR shifts and spin-spin couplings in LAlanine-LAlanine zwiteranion [1], vibrational corrections of Cross-correlated relaxation rates across the glycosidic bond in DNA nucleotides [2] and corrections of the NMR spin-spin couplings with respect to rotation in silylated phenols [3].

[1] Bouř, Buděšínský, Špirko, Kapitán, Šebestík, Sychrovský, JACS 127 17079-17089, 2005

[2] Sychrovský, Muller, Schneider, Smercki, Špirko, Šponer, Trantírek, 127 14663-14667 2005

[3] Sychrovský, Špirko, Prokop, Schraml, in preparation