Theoretical study of self-assembled hydrogen-bonded azodibenzoic acid tapes and rosettes

A theoretical study of hydrogen-bonded supramolecular systems is described. Vibrational properties, hydrogen-bond lengths, molecular orbital wavefunctions, and density matrix analysis are used to explain the thermodynamics of the self-assembly process. The PM3 enthalpies and Gibbs free energies of formation for each optimized trans-1 and cis-2 hydrogen-bonded oligomers show that trans-azodibenzoic acid favours self-assembly into linear tapes, while cis-azodibenzoic acid should form cyclic tetramers. Electronic properties evaluate the relative stabilities of these hydrogen-bonded structures, providing a useful approach to study supramolecular structures.