Porphyrin, chiral memory

Lauceri, R., Raudino, A., Scolaro, L. M Mical, N., and Purrello, R. (2002). From achiral porphyrins to template-imprinted chiral aggregates and further self-replication of chiral memory from scratch. / Am. Chem. Soc., 124, 894-5. 

Keywords Hierarchy Memory Porphyrin Supramolecular chirality Transfer... 

Chiral Induction and Memory Porphyrin (Hetero-) Self-Assemblies in the Presence of Poly-Glutamate... 

On the other hand, all the other couples of porphyrins bearing opposite charges H2T4-H2TPPS, H2T4-CuTPPS and CuT4-CuTPPS lead to the formation of supra-molecular species for which the chiral memory phenomenon occurs. All the three... 

The behaviour of the systems presented above is, however, even more complex and richer than what we have shown until now. In particular, a deeper study of the tetra-anionic porphyrin Ru-complexes system has revealed that, using proper experimental conditions, not only the porphyrin J-aggregates show the chiral memory phenomenon, but also that the chiral information can be cyclically erased and rewritten, switching on and off the porphyrin ICD signal by pH variations [51]. 

Onouchi H, Miyagawa T, Morino K et al (2006) Assisted formation of chiral porphyrin homoaggregates by an induced helical poly(phenylacetylene) template and their chiral memory. Angew Chem Int Ed Engl 45 2381-2384... 

Purrello R, Raudino A, Monsu Scolaro L et al (2000) Ternary porphyrin aggregates and their chiral memory. J Phys Chem B 104 10900-10908... 

Mammana A, De Napoli M, Lauceri R et al (2005) Induction and memory of chirality in porphyrin hetero-aggregates the role of the central metal ion. Bioorg Med Chem 13 ... 

Lauceri R, Purrello R (2005) Transfer, memory and amplification of chirality in porphyrin aggregates. Supramol Chem 17 61-66... 

Lauceri R, D urso A, Mammana A et al (2008) Chiral memory induction, amplification, and switching in porphyrin assemblies. Chirality 20 411 —419... 

Lauceri R, Fasciglione GF, D Urso A et al (2008) Kinetic investigation of porphyrin interaction with chiral templates reveals unexpected features of the induction and self-propagation mechanism of chiral memory. J Am Chem Soc 130 10476—10477... 

Randazzo R, Mammana A, D Urso A et al (2008) Reversible chiral memory in ruthenium tris(phenanthroline)-anionic porphyrin complexes. Angew Chem Int Ed Engl 47 9879-9882... 

Mizuno.Y., Aida,T.,Yamaguchi, K., Chirality-Memory Molecule Crystallographic and Spectroscopic Studies on Dynamic Molecular Recognition Events by Fully Substituted Chiral Porphyrins,... 

Furusho, Y., Kimurat, T., Mizuno, Y. and Ada, T. (1997) Chirality-memory molecule a D2-symmetric fully substituted porphyrin as a conceptually new chirality sensor. J. Am. Chem. Soc. 119 5267-5268. 

Memory of chirality is demonstrated by a simple experiment addition of an excess of A-[Ru(phen)3]2+ (15 pM) to J aggregates preformed in the presence of A-[Ru(phen)3]2+ (10 pM) does not cause inversion of the CD bands in the visible region (where the absorption features of porphyrins dominate) but only in the UV region (the spectroscopic region where absorption of the inorganic complex occurs). This straightforward experiment (Fig. 26) shows that this type of J aggregates remembers the chirality imprinted at the very onset of their formation [51]. 

Finally, we feel it is worthwhile to stress one more time the importance of the kinetic inertia in the (reversible) chiral transfer and memory processes of our porphyrin systems. Inertia provides evidence that the system is trapped in an energy minimum. In the above examples the minimum is local the real minimum is that reached from the achiral system whose formation involves the same enthalpic contribution of the chiral one but a more favourable entropic contribution. In particular, the network of electrostatic interactions ensures a quite deep local energy minimum (that is a high value of EA). 

Fig. 4.32. Chiral recognition and induction of molecular memory in Ce(IV) complexes with a substituted porphyrin. Redrawn from S. Shinkai et al., J. Chem. Soc., Perkin Trans. I 3259, 1999.

Fig. 28.3 A D2 symmetric octaalkyl substituted porphyrin as chirality sensor and memory. (Reproduced with permission from Chemical and Engineering News, 1997.)...

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