The performance of hybrid density functional theory for the calculation of indirect nuclear spin-spin coupling constants in substituted hydrocarbons.

Density functional theory, in particular, with the Becke-3-parameter-Lee-Yang-Parr (B3LYP) hybrid functional, has been shown to be a promising method for the calculation of indirect nuclear spin-spin coupling constants. However, no systematic investigation has so far been undertaken to evaluate the capability of B3LYP to calculate these coupling constants accurately, taking properly into account the vibrational contributions. In this work, vibrationally corrected indirect spin-spin coupling constants were calculated using the B3LYP functional for 10 rigid unsubstituted and substituted hydrocarbons: ethyne, ethene, allene, cyclopropene, cyclopropane, cyclobutene, pyrrole, furan, thiophene and benzene. The resulting spin-spin constants were compared with the available experimental values. The basis sets in these calculations give indirect nuclear spin-spin coupling constants of ethyne that are almost converged to the basis-set limit, making the intrinsic error of the computational method and the error in equilibrium geometry the main sources of error. On average, the B3LYP functional overestimates the indirect nuclear spin-spin coupling constants in hydrocarbons by 10%. Copyright 2004 John Wiley & Sons, Ltd.