Supramolecular Synthons: Validation and Ranking of Intermolecular Interaction Energies

Building upon Desiraju's concept of a supramolecular synthon, we have calculated cohesive energies and thermal stabilities of molecular systems related to the proposed synthons. The method employed is PIXEL, which allows reliable and extensive mapping of intermolecular surfaces. Comparisons with accurate ab initio calculations are included. Stability is judged in terms of calculated binding energies and stretching vibrational amplitudes around room temperature. The list of systems treated includes carboxylic acids, amides, alcohols, N-H center dot center dot center dot N hydrogen bonds, as well as benzene stacking and several types of C-H center dot center dot center dot O interactions. Cl center dot center dot center dot Cl synthons are compared with C-H center dot center dot center dot Cl synthons. The result is a working table of absolute and relative strengths that could serve as a guideline for crystal engineering.