Abstract
Results on the theoretical explanation of the shape of optical bands in polymethine dyes, their dimers and aggregates are summarized. The theoretical dependence of the shape of optical bands for the dye monomers in the vinylogous series in line with a change in the solvent polarity is considered. A simple physical (analytical) model of the shape of optical absorption bands in H-aggregates of polymethine dyes is developed based on taking the dozy-chaos dynamics of the transient state and the Frenkel exciton effect in the theory of molecular quantum transitions into account. As an example, the details of the experimental shape of one of the known H-bands are well reproduced by this analytical model under the assumption that the main optical chromophore of H-aggregates is a tetramer resulting from the two most probable processes of inelastic binary collisions in sequence: first, monomers between themselves, and then, between the resulting dimers. The obtained results indicate that in contrast with the compact structure of J-aggregates (brickwork structure), the structure of H-aggregates is not the compact pack-of-cards structure, as stated in the literature, but a loose alternate structure. Based on this theoretical model, a simple general (analytical) method for treating the more complex shapes of optical bands in polymethine dyes in comparison with the H-band under consideration is proposed. This method mirrors the physical process of molecular aggregates forming in liquid solutions: aggregates are generated in the most probable processes of inelastic multiple binary collisions between polymethine species generally differing in complexity. The results obtained are given against a background of the theoretical results on the shape of optical bands in polymethine dyes and their aggregates (dimers, H*- and J-aggregates) previously obtained by V.V.E.
Highlights
Aggregation of polymethine dyes is one of the simplest and most striking examples of self-organization of organic matter at the supramolecular level
This is because the probabilities of quantum transitions in the case of strong dozy chaos no longer depend on the chaotic dynamics of the transient state and depend only on the initial and final states, which is why dozy chaos so long eluded researchers’ attention
This work brings some completion to the theoretical explanation of a set of the optical band shapes in polymethine dyes, their dimers and aggregates
Summary
Aggregation of polymethine dyes is one of the simplest and most striking examples of self-organization of organic matter at the supramolecular level. Until very recently, these aggregates could not be observed directly in experiments, and optical spectroscopy methods were essentially the only way to study them. To highlight the features of the new results obtained here (§2: figure 6 and the related text about optical bands as solution-dependent; §3.4; §4 and §5), we present those features against a background of the theoretical results on the shape of optical bands in polymethine dyes and their aggregates (monomers, dimers, H*- and J-aggregates), which were previously obtained by V.V.E. For the self-sufficiency of this article, we briefly introduce the dozy-chaos theory on the qualitative (§2.1 and §2.2) and quantitative (§2.2) levels
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
