Chiral memory: Induction, amplification, and switching in porphyrin assemblies

Abstract

The interaction between the tetra-anionic porphyrin H2TPPS and its copper derivative, CuTPPS, with the tetra-cationic porphyrin H2T4 and its copper derivative, CuT4, leads, in aqueous solution, to the formation of remarkably stable and kinetically inert heteroaggregates. The aggregation process is under hierarchic control and, in the presence of a suitable chiral mold, leads to the formation of chiral porphyrin heteroassemblies as stable and inert as the achiral ones. Because of these properties, the chirality of the porphyrin "imprinted" heteroaggregates not only survives the disruption of the template, but also to its complete removal from the solution. Notably, the template-free chiral porphyrin system is an excellent mold for its own self-replication. The relevant characteristics of these chiral heteroaggregates together with the knowledge of the forces that guide the aggregation processes permitted us to design a new but similar system. This system not only is able to store chiral information, but also is capable to release and restore it reversibly, in a cyclic manner. This has been achieved by modulating the charges carried by one of the two coupled porphyrins through protonation under various pH conditions. The role of the central metal ion and the template-free chiral structure of the CuT4-H2TPPS heteroaggregate, determined through EDXD analysis, are also presented.

Aggregation behavior of tetraphenylporphyrin in aqueous surfactant solutions: Chiral premicellar J-aggregate formation

“…The most accepted one is a chiral template hypothesis considering the role of the external chiral agents (including the trace admixtures) in the asymmetric assembly of the porphyrin monomers [29][30][31][32][33][34]. Another point of view deals with a hydrodynamically-induced symmetry breaking which occurs due to a preferable arrangement of the porphyrin building blocks under the hydrodynamic forces [35][36][37].…”

Chiral Induction, Memory, and Amplification in Porphyrin Homoaggregates Based on Electrostatic Interactions

“…[23][24][25][26][27][28][29][30] Understanding the mechanism of transfer of chirality from individual molecules through different hierarchical levels in artificial systems is of great significance in understanding chiral amplification in biologically relevant phenomena and aggregation processes, whereas control of chirality transfer in dynamic systems offers ample opportunities towards future smart materials with predictable properties and behavior. [4,9,31] Porphyrins are very important and excellent building blocks for the assembly of supramolecular nanoarchitectures. The chiral memory of heteroaggregated porphyrins with opposite charges has been achieved by Purrello and colleagues, but the oppositely charged heteroaggregation process and the central metal ion were considered to be essential for the chiral memory and further self-replication.…”

Tuning the Electrochemistry of Free‐Base Porphyrins in Acidic Nonaqueous Media: Influence of Solvent, Supporting Electrolyte, and Ring Substituents

“…These compounds are then represented as H 4 P(X) 2 , where X=F − , Cl − , Br − , I − , or PF 6 − . Previous studies on interactions of diprotonated porphyrins with anions have focused largely on structural aspects, the relationships between hydrogen‐bond formation and the photophysical properties of the ion‐paired diprotonated compounds, or the assembly properties of the compounds for applications in smart soft nanomaterials for data storage and processing, chiral sensing, optobioelectronics, chiroptical devices, and catalysis . However, to the best of our knowledge, there have been no systematic investigations that have focused on the interacting effects of anions, solvent, and porphyrin structures on the protonation, electrochemistry, and spectroscopic properties of the diprotonic free‐base porphyrins during or after electroreduction in nonaqueous media.…”

“…[12,[19][20][21][22] Previous studies on interactions of diprotonated porphyrins with anions have focused largely on structurala spects, [12,19] the relationships between hydrogen-bond formation and the photophysical properties of the ion-paired diprotonated compounds, [23,24] or the assembly properties of the compounds for applications in smart soft nanomaterials for data storagea nd processing, chiral sensing, optobioelectronics, chiroptical devices, and catalysis. [17,[25][26][27][28][29][30] However,t ot he best of our knowledge,t here have been no systematic investigations that have focused on the interacting effects of anions, solvent, and porphyrin structures on the protonation, electrochemistry,a nd spectroscopicp roperties of the diprotonic free-Ad etailed study of reduction potentials, electroreduction mechanisms, and acid-base chemistry was carried out on two series of free-base porphyrinsi nn onaqueous media. Thef irst series is represented by four b-pyrrole-substituted tetraphenylporphyrin (TPP) derivatives, two of which are planar andt wo of which are nonplanar in their nonprotonated form.…”