Kinetic Control of the Supramolecular Chirality of Porphyrin J-Aggregates

• Published in: Chemistry : a European journal Vol. 18; no. 28; pp. 8820 - 8826
• Main Authors: Sorrenti, Alessandro, El-Hachemi, Zoubir, Arteaga, Oriol, Canillas, Adolf, Crusats, Joaquim, Ribo, Josep M.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 09.07.2012; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Agglomeration; Aggregates; Bands; Chemistry; chirality; circular dichroism; Diffusion; Formations; Nucleation; Nuclei; Polymerization; porphyrinoids; Porphyrins; self-assembly; supramolecular chemistry
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201200881

The aggregation of achiral sulfonatophenyl‐ and phenyl‐meso‐substituted diprotonated porphyrins to chiral J‐aggregates is a hierarchical noncovalent polymerization process preceded by a critical nucleation stage. This allows significant enantiomeric excesses by the formation of a few primary nuclei and the control of their growth by the effect that flows (imperfect mixing) have on the secondary nucleation of the J‐aggregate particles. In addition, the results strongly suggest that when only one species of aggregate predominates, the CD signals of the three excitonic bands in the visible region (around 420, 490, and 700 nm) show the same sign. Thus, differences on their relative sign would be due to the presence of different species. How to avoid the racemic: The aggregation of achiral sulfonatophenyl‐ and phenyl‐meso‐substituted diprotonated porphyrins is a noncovalent polymerization process preceded by a critical nucleation stage that yields chiral J‐aggregates. Significant enantiomeric excesses are obtained by the formation of a few first nuclei and the control of their growth by the effect of flows (imperfect mixing) on the diffusion of clusters and J‐aggregate particles (see figure).