Intramolecular interactions in porphyrin – labelled polymers studied by spectroscopic, photothermal and photoelectric examinations

Triplet Thermal Relaxation Study as a Probe of Weak Interdimers of Porphyrin Derivatives

“…In this article we present the results of the study done for two different systems: two metal-free non-substituted phthalocyanine dyes [21] and covalent porphyrin-polymer systems [23,24]. We divided our presentation into two parts; in the first we show the absorption and fluorescence results of our systems-the phthalocyanine dyes and the porphyrin-polymer samples were examined in the wide range of concentrations in solvents of different polarities (dioxane, water, and DMSO), in the second part of our investigations we concentrate on the PAS and LIOAS examinations to show how one can take advantage from the PAS and LIOAS methods to follow the presence of weakly interacting aggregates.…”

“…The main absorption and fluorescence parameters are reported in Table 1. [21,23,24] Apart from the small blue absorption band shifts in the Q region, the increase of the 606/607 nm bands and small broadening of the bands are observed. The half-width of the absorption band evaluated for the phthalocyanine monomers of 1 and 2 are about 3.0×10 5 cm −1 (the Soret band) and 1.2×10 5 cm −1 (the Q band), respectively.…”

“…2c-e. As observed, the porphyrin dye moieties absorb intensively in the range from 418 nm to 453 nm (Soret bands) and only modestly in the Q region from about 500 nm to about 700 nm; in metallic porphyrins 3 and 4, two Q bands are characteristic for monomeric porphyrins (due to the D 4h π -electron symmetry), and in the absorption spectra of the porphyrin of the D 2h symmetry, four Q bands are seen in 5 [26]. In the investigated porphyrin-PEG samples, no spectacular influence of the polymer chains is observed [23]. Thus, we will not discuss this problem, but rather we focus our study mostly on the influence of the solvent polarity on interactions between the dye molecules.…”

“…However, when weak interactions between molecule species take place and even that no significant changes in absorption and only slightly in fluorescence are observed, it is possible to follow weakly interacting molecules by performing enhancement of the triplet population by the use of complementary spectroscopic methods such as photoacoustics (PAS) and light-induced optoacoustic spectroscopy (LIOAS) [22][23][24].…”

“…This article is a mini-review of the studies and shows how one can take advantage of the LIOAS method accompanied with the photoacoustic method supported by other spectroscopic examinations such as absorption and fluorescence to follow weakly interacting dye molecules in interdimers for the case when absorption spectroscopy (and/or weak fluorescence) is not fully useful for this purpose [21][22][23][24]. Particular attention was paid on the LIOAS experiments to follow the dye's triplet population, triplet thermal relaxation, and intermolecular interactions occurring in the investigated systems.…”