Supramolecular Synthons : Validation and Ranking of Intermolecular Interaction Energies

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