Electronic Mechanisms of Intra and Intermolecular J Couplings in Systems with C-H•••O Interactions

GIRIBET, CLAUDIA G.; RUIZ DE AZUA, MARTIN C.; VIZIOLI, CELIA V.; CAVASOTTO, CLAUDIO N.

INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES

MOLECULAR DIVERSITY PRESERVATION INTERNATIONAL-MDPI

Año: 2003 vol. 4 p. 203 - 217

1422-0067

Correlation effects on the change of 1J(CH) couplings in model systems I:NCH...H2O and II:CH4...H2O as a function of the H...O distance are discussed. RPA and SOPPA results follow a similar trend in system II. In system I RPA values decrease monotonously as the H...O distance decreases, while SOPPA ones exhibit flat maximum near equilibrium. Such different behavior is ascribed to the sigma-transmitted component. Intermolecular couplings at the equilibrium geometry of I are analyzed by means of the CLOPPA approach. The larger absolute value of 2hJ(CO) compared to 1hJ(HO) is found to arise from contributions involving a vacant LMO localized in the C-H...O moiety.