Preferential solvation and solvation shell composition of free base and protonated 5, 10, 15, 20-tetrakis(4-sulfonatophenyl)porphyrin in aqueous organic mixed solvents

Supramolecular Chiral Aggregation of Porphyrin Induced by Photo-Generated Triphenylamines Radical Cations

Here, it is shown that photoirradiation triggered chiral J-aggregates formation of an achiral anionic porphyrin, TPPS (tetrakis(4-sulfonatophenyl) porphyrin), in the presence of chiral triphenylamine (TPA) derivatives. A series of chiral triarylamines linked with aromatic rings is designed through urea or amide bonds. UV-irradiation of self-assembled urea-linked triphenylamine derivatives causes the formation of persistent radical cations in the chlorinated solvents, which subsequently induces the aggregation of TPPS. Transferring chirality of TPA derivatives to achiral TPPS J-aggregates leads to the chiral assemblies with remarkable chiroptical signals. The experimental results demonstrate that, TPA derivatives linked by the urea bond can effectively promote the aggregation of TPPS rather than those with the amide bond although the photo-generated radical cations are both produced. It is suggested that the urea-linked TPA derivatives are more favorable to stable radical cations and thus cause the formation of TPPS chiral J-aggregation. This work may open up an avenue for designing photo-modulated chiral supramolecular assemblies.

Solvatochromism, Preferential Solvation and Multiparametric Approach to the Spectral Shift of Methyl Orange in Aqueous Cosolvent Mixtures

In this study, the solvatochromic behavior of Methyl orange was studied visible spectrophotometrically in seven aqueous binary systems from water with methanol, ethanol, propanol, DMF, DMSO, acetone and dioxane solvents. The spectral data was interpreted in terms of solute-solvent and solvent-solvent interactions. The deviation from linearity in the plots of νmax versus x2 due to preferential solvation of the Methyl orange by one component of the mixed solvent and due to solvent microheterogeneity. The preferential solvation parameters local mole fraction X2L, solvation index δs2 and exchange constant K12 were evaluated. The preference of solute to be solvated by one of the solvating species relative to others was explained. All values of K12 were less than unity that indicates the preferential solvation of Methyl orange by water, except in case the water-propanol mixture where K12 was higher than unity. The preferential solvation index δs2 values were calculated and interpreted for each binary mixture. The magnitude of preferential solvation index was highest in water-DMSO mixtures than in the all other solvent mixtures. The energy of electronic transition in maximum absorption (ET) was calculated in each binary mixture. The extent and importance of each solute-solvent interactions to ET were analyzed by the linear solvation energy relationships using the Kamlet-Taft strategy.

The Preferential Solvation of Methyl Red in Various Binary Aqueous Solutions: Solvatochromism, Preferential Solvation Parameters, Microheterogeneity of Solvents and Polarity Scale

The solvatochromic characteristics of methyl red were examined in several aqueous solutions from pure water, with methanol, ethanol, propanol, acetonitrile, and dioxane. In order to explain the preferred solvation of the probe azo dye in the binary mixed solvents, the solvent exchange model of Bosch and Roses was used to evaluate the association between the empirical solvent polarity scale (ET) values of MR and solvent composition. Non-linear solvatochromism of methyl red was noted in all aqueous mixtures containing methanol, ethanol, propanol, acetonitrile, and dioxane. In addition to calculating the local mole fraction of each solvent composition in the cybotactic area of the probe, the impact of the solvating shell composition on the preferential solvation of the solute dye was examined in terms of both solvent-solvent and solute-solvent interactions. The local mole fraction of each solvent composition in the cybotactic region of the probe was also calculated. The results indicated that the MR solvation shell was thoroughly saturated with the solvent complex S12 in the following order: dioxane > ethanol > methanol > acetonitrile > propanol. Data from the binary systems were analyzed with KAT parameters using a multi-model; in aqueous methanol and ethanol solutions, the hydrogen acidity was more responsible for the spectral shift, whereas in aqueous acetonitrile and dioxane solutions, the basicity has a greater influence.

First-principles modeling of chemistry in mixed solvents: Where to go from here?

Mixed solvents (i.e., binary or higher order mixtures of ionic or nonionic liquids) play crucial roles in chemical syntheses, separations, and electrochemical devices because they can be tuned for specific reactions and applications. Apart from fully explicit solvation treatments that can be difficult to parameterize or computationally expensive, there is currently no well-established first-principles regimen for reliably modeling atomic-scale chemistry in mixed solvent environments. We offer our perspective on how this process could be achieved in the near future as mixed solvent systems become more explored using theoretical and computational chemistry. We first outline what makes mixed solvent systems far more complex compared to single-component solvents. An overview of current and promising techniques for modeling mixed solvent environments is provided. We focus on so-called hybrid solvation treatments such as the conductor-like screening model for real solvents and the reference interaction site model, which are far less computationally demanding than explicit simulations. We also propose that cluster-continuum approaches rooted in physically rigorous quasi-chemical theory provide a robust, yet practical, route for studying chemical processes in mixed solvents.

Solvatochromism in some cosolvent mixtures of sulfolane and aliphatic alcohols: a tool to predict preferential solvation

The phenomenon of solvatochromism for three indicator solutes, namely para-nitroaniline, N,N-dimethyl-p-nitroaniline, and the betaine dye 4-(2,4,6-triphenylpyridinium-1-yl)-2,6-diphenylphenolate, was studied at 303.15 ± 0.1 K by means of UV–vis absorption measurements. The spectral shifts of these dyes in different mole fractions (0.0–1.0) of binary mixtures of sulfolane with eight alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butanol, tert-butanol) were analyzed to investigate preferential solvation of them in terms of both the solute–solvent and the solvent–solvent interactions. A modified theoretical model (solvent exchange model) was successfully employed to calculate preferential solvation parameters and to obtain information into the contribution of intermolecular interactions to the local and bulk mole fraction distribution of solvation species. It was found that the solvation shell of the dyes is mainly affected by the solvent–solvent interactions, and in all binary mixtures, the studied solvation behavior was non-ideal.

Dispersion of the Photosensitizer 5,10,15,20-Tetrakis(4-Sulfonatophenyl)-porphyrin by the Amphiphilic Polymer Poly(vinylpirrolidone) in Highly Porous Solid Materials Designed for Photodynamic Therapy

The ability of the amphiphilic and biocompatible poly(vinylpyrrolidone) to avoid self-aggregation of the photosensitizer 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin in aqueous solution in the presence of the biocompatible polycation chitosan, polymer that induces the dye self-aggregation, is shown. This is related to the tendency of the dye to undergo preferential solvation by the amphiphilic polymer. Importantly, the dispersant ability of this polymer is transferred to the solid state. Thus, aerogels made of the biocompatible polymers chitosan and chondroitin sulfate, and containing the photosensitizer dispersed by the amphiphilic polymer have been synthesized. Production of reactive oxygen species by the aerogel containing the amphiphilic polymer was faster than when the polymer was absent, correlating with the relative concentration of dyes dispersed as monomers. The aerogels presented here constitute low cost biocompatible materials bearing a conventional photosensitizer for photodynamic therapy, easy to produce, store, transport, and manage in clinical practice.

The solvation dynamics and rotational relaxation of protonated meso-tetrakis(4-sulfonatophenyl)porphyrin in imidazolium-based ionic liquids measured with a streak camera

For the steady-state behavior of diprotonated tetrakis(4-sulfonatophenyl)porphyrin (H4TPPS2-) in five imidazolium ionic liquids (ILs), the absorption positions of H4TPPS2- primarily depend on the constituent ions of the ILs whereas the emission positions of H4TPPS2- strongly depend on the polarity of the ILs. The fluorescence spectra of H4TPPS2- with different excitation wavelengths show no red-edge effect in our system. The dynamics of H4TPPS2- in ILs is further studied with a streak camera, and the relaxation process of ILs occurs on two different time scales. The short lived component attributed to the local motion of the cations and the anions around the porphine core varies from 32 to 196 ps. The long lived one originated from the collective diffusive motions of the cations and anions varies from 460 to 1072 ps. The average solvation time depends on the viscosity of the ILs. The rotational relaxation times of H4TPPS2- decrease as the viscosity of the ILs decreases.