Probing molecular environments with a Fictitious isotopic dipole

Abstract

A HD-like isotopic dipole moment is proposed as a sensible probe for molecular environments, in particular for electrostatic fields and polarizable (reactive) sites of molecules. Fictitious nuclear masses are chosen in order to yield a rigid dipole with appropriate magnitude. Upon subtracting the Born-Oppenheimer energy, the interaction is reduced to the Field-dipole-like and the dipole-polarizability-like terms, the last one being particularly informative since connected to potentially reactive sites. The Field strength and orientation are easily obtained by identifying the minimum Field-dipole energy configuration and flipping the dipole from it. In this case the method appears to have a superior accuracy in comparison with ab initio approaches. In tests with hydrogen, water, benzene and chlorobenzene molecules and with a frustrated Lewis pair, the potential of the method is assessed.