Conformational analysis of chiral supramolecular aggregates: modeling the subtle difference between hydrogen and deuterium.

A detailed analysis of the conformational states of self-assembled, stereoselectively deuterated benzene-1,3,5-tricarboxamides ((S,S,S)-D-BTAs) reveals four different conformers for the supramolecular polymers. The relative amount of the conformers depends on the solvent structure and the temperature. With the help of a model, the thermodynamic parameters that characterize the different conformational states were quantified as well as the amount of the species that occur at different stages of the polymerization process. The results show that small changes in the stability between different types of conformers formed by (S,S,S)-D-BTAs—in the order of a few J mol(–1)—arise from the combination of interactions between the solvent/supramolecular aggregate, temperature, and solvent structure. While the introduction of a deuterium label allows to sensitively probe the solvophobic effects in the supramolecular aggregation, a rationalization of the observed effects on a molecular level is not yet straightforward but is proposed to result from subtle effects in the vibrational enthalpy and entropy terms of the isotope effect.