Paramagnetic species on catalytic surfaces—DFT investigations into structure sensitivity of the hyperfine coupling constants

Abstract

Structure sensitivity of the hyperfine coupling constants was investigated by means of DFT calculations for selected surface paramagnetic species. A CH 2OH 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 5O 8H 10] cluster, whereas the zeolite hosting sites were epitomized by [Si 4AlO 5(OH) 10] − cluster. Three different coordination modes of the CH 2OH radical were considered and the isotropic 13 C and 1 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 η 1-N{CuNO} 11 and η 1-O{CuNO} 11 linkage isomers were calculated at the BPW91/LanL2DZ and 6-311G(df) level. For the most stable η 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 contributions.