Mechanistic Study of the Solvent‐Dependent Formation of Extended and Stacked Supramolecular Polymers Composed of Bis(imidazolylporphyrinatozinc) Molecules

Abstract

Bis(imidazolylporphyrinatozinc) molecules linked through a1 ,3-butadiynylene moiety respond to the solvents they are dissolved in to afford exclusively extended (E) or stacked (S) supramolecular polymers. This system is expected to be as olvation/desolvation indicator. However, the principles underlying the solvent-dependent formation of the two types of polymers and the mechanism of the transformation between them are unclear.T he formation of the polymers is considered to depend on the two types of complementaryc oordination bonds that can be formed and the p-p interactions between the porphyrins. In this study,t he contributionsa nd solventd ependence of both the coordination bonds and the p-p interactions have been investigated. The results clearly indicate that the coordination bonds are weaklyo rl ittle solvent-dependent, and that the p-p interactions functione ffectively only in the inner porphyrins of the S-polymer and are strongly solvent-dependent. Thermodynamic analysis revealed that the formation of the E-or Spolymer in solution is determined by the total energiesa nd the typeo fs olventu sed. Thet ransformation of the E-to Spolymer wasi nvestigated by gel permeation chromatography.T he kinetics of the transformationw ere also determined.T he role of the terminal imidazolylporphyrinatozinc moietiesw as also investigated:T he results indicatet hat the transformation from the E-to S-polymer occurs by an exchange mechanism between the polymers, induced by attack of terminal free imidazolyl groups on ap olymer to zinc porphyrins on other polymers.Supporting information and the ORCID identification number(s) for the author(s) of this articlecan be found under: https://doi.

Ionic supramolecular polymerization of water-soluble porphyrins: balancing ionic attraction and steric repulsion to govern stacking

“…Thus, changing of polarity or composition of the solvent, or varying the temperature, can trigger the self-assembly of porphyrins and allow control over polymerization processes. [12][13][14][15] Despite an abundance of porphyrin structures, relatively little attention has been paid to their use in other categories of polymerization-for example, by exploiting their ionic interactions, as in the widespread practical preparation of covalent polymers. Any comprehensive means of applying such approaches would be highly attractive for the production of new families of supramolecular polymers through simple acid/base reactions.…”

Porphyrin-based supramolecular polymers

“…22–50 Similarly, nitrogen-bearing aromatic groups such as pyridyl, imidazole, and triazole groups can be incorporated into the meso -position. 51–61 Such nitrogen-bearing aromatic groups can provide metal coordination sites.…”

“…The coordination of axial ligands onto metalloporphyrin becomes a driving force for supramolecular polymer growth. 51–61…”

Measurement of Solvation Ability of Solvents by Porphyrin-Based Solvation/Desolvation Indicators

“…Here, we report a new method for measuring the SA of solvents by using the solvation/desolvation indicators 1Zn 2 and 2Zn 2 (Figure 1) that we developed previously. 32,33…”

“…Although solvent-dependent Δ G values have been reported for several dynamic systems, they are considered inadequate in terms of the numbers and types of solvents assessed to study solvent dependencies on π–π interactions systematically. Here, we report a new method for measuring the SA of solvents by using the solvation/desolvation indicators 1Zn 2 and 2Zn 2 (Figure ) that we developed previously. , …”