D. B. Amabilino, P. Iavicoli,H. Xu, L. N. Feldborg, M. Linares, M. Paradinas, S. Stafström, C. Ocal, B. Nieto-Ortega, J. Casado, J. T. López Navarrete, R. Lazzaroni and S. De Feyter
J. AM. CHEM. SOC. 2010, 132, 9350–9362 (2010) | DOI: 10.1021/ja101533j
A synthetic strategy was developed for the preparation of porphyrins containing between one and four stereogenic centers. The low-dimensional nanoscale aggregates of these compounds reveal the profound effects of this varying molecular chirality on their supramolecular structure and optical activity. A scanning tunneling microscopy study of monolayers on graphite shows that the degree of structural chirality with respect to the surface increases almost linearly with the number of stereogenic centers. In solution, four hydrogen bonds induce the formation of an H-aggregate, and circular dichroism measurements and theoretical studies indicate that the compounds self-assemble into helical structures. Both the chirality and stability of the aggregates depend critically on the number of stereocenters.