Tytuł pozycji:
Paramagnetic species on catalytic surfaces : DFT investigations into structure sensitivity of the hyperfine coupling constants
Structure sensitivity of the hyperfine coupling constants was investigated by means of DFT calculations for selected surface paramagnetic species. $A\cdot CH_{2}OH$ radical trapped on silica and intrazeolite copper nitrosyl adducts encaged in ZSM-5 were taken as the examples. The surface of amorphous silica was modeled with a $[Si_{5}O_{8}H_{10}]$ cluster, whereas the zeolite hosting sites were epitomized by $[Si_{4}S=AlO_{5}(OH)_{10}]^{-}$ cluster. Three different coordination modes of the $\cdot CH_{2}OH$ radical were considered and the isotropic $^{13}\textrm{C}$ and $^{1}\textrm{H}$ hyperfine constants of the resultant van der Waals complexes, calculated with B3LYP/6-311G(d), were discussed in terms of the angular deformations caused by hydrogen bonds with the cluster. The magnetic parameters of the $\eta^{1}-N(CuNO)^{11}$ and $\eta^{1}-O(CuNO)^{11}$ linkage isomers were calculated at the BPW91/LanL2DZ and 6-311G(df) level. For the most stable $\eta^{1}-N$ adduct a clear dependence of the spin density distribution within the Cu-NO moiety on changes in the Cu-N-O angle and the Cu-N bond distance was observed and accounted for by varying spin polarization and delocalization.