Molecular electrostatics for probing lone pair-pi interactions

An electrostatics-based approach has been proposed for probing the weak interactions between lone pair containing molecules and pi deficient molecular systems. For electron-rich molecules, the negative minima in molecular electrostatic potential (MESP) topography give the location of electron localization and the MESP value at the minimum (V-min) quantifies the electron-rich character of that region. Interactive behavior of a lone pair bearing molecule with electron deficient p-systems, such as hexafluorobenzene, 1,3,5-trinitrobenzene, 2,4,6-trifluoro-1,3,5-triazine and 1,2,4,5-tetracyanobenzene explored within DFT brings out good correlation of the lone pair-pi interaction energy (E-int) with the V-min value of the electron-rich system. Such interaction is found to be portrayed well with the Electrostatic Potential for Intermolecular Complexation (EPIC) model. On the basis of the precise location of MESP minimum, a prediction for the orientation of a lone pair bearing molecule with an electron deficient pi-system is possible in the majority of the cases studied.