The geometrical, conformational, and electronic properties of a series of D-π-A metal-free dyes designed for use as sensitizers in DSSCs were studied using DFT and TD-DFT methods. A substituted triphenylamine moiety was used as the donor group and 2-cyanoacrylic acid as the acceptor group in these dyes. They also contained conjugated bridging π-linker groups containing two or more thiophene rings to enhance the intramolecular charge transfer. The B3LYP, M06-HF, ωB97XD and CAM-B3LYP functionals were utilized in combination with the 6-31G(d,p) basis set for the calculations. The dye solvation process was taken into account via the polarizable continuum model. To rationalize the relationships between dye structure and the photochemical properties of the dyes when used as sensitizers in DSSCs, the vertical excitation energies, the light-harvesting efficiencies, the free-energy changes during the process of injecting an electron into the surface of a TiO2 nanocrystalline semiconductor, and the open-circuit potentials were calculated for all of the dyes in the solvent THF using the above methods. The results of these computations are discussed and compared with the available corresponding experimental data.

The kinetics of solvolysis of trans — [Co(py)4Cl2]ClO4 have been investigated in aquo-organic solvent media such as water + ethanol (0-60% v/v) and water -+ urea (0-40% w/w) in the temperature range 40-60°C. The first-order rate constant varies nonlinearly with the reciprocal of the relative permittivity ∊r. The solvolysis of these types of complex involves a rate-determining dissociative step corresponding closely to 100% separation of Co3+ … Cl in the transition state. The Gibbs energy cycle relating the Gibbs energy of activation in water and in the mixtures to the Gibbs energies of transfer of individual ionic species between water and the mixtures ΔG°t(Cl) can be applied. Moreover, more than one extrema in the enthalpies and entropies of activation are found with both binary aqueous solvent mixtures. The solvolysis of trans — [Co(py)4Cl2]ClO4 has also been studied in the presence of Hg(II) and the ionic strength dependence of the reaction rate has been analysed.

Reactions of aniline derivatives in dimethyl sulfoxide with phenyl 1‐(2,4‐dinitronaphthyl) ether yield aryl 1‐(2,4‐dinitronaphthyl) amine, which results in substitution of the phenoxy groups at the naphthyl ipso carbon atom. Rate constants were measured spectrophotometrically, and reaction proton transfer was rate limiting. The values of the rate coefficients indicate a rate‐limiting proton transfer mechanism with significant substituent effects. The calculated activation parameters were of regular variation with substituents in 4‐ and 3‐position in the aniline nucleophile, and the reaction proceeded through a common mechanism. Hammett's reaction constant showed that the reaction rate constants depend on the electron density of the nitrogen atom of aniline derivative, whereas the coefficient value obtained from the Brönsted relation indicated that the reaction was significantly associative and quite zwitterion like. Computational studies of the substitution were carried out based on density functional theory, and theoretical to the experimental agreement was achieved.

Kinetics and solvent effects of the aquation of trans 4 Cl 2 ] + have been studied in ethanol + water ranging from 0 to 60% (v/v) and urea + water of various solvent compositions up to 40% (w/w) of organic solvent. Thermodynamic activation parameters were computed and discussed in terms of the solvation effect. Isokinetic temperature within the experimental range revealed that the existence of the compensation effect arising from the solute-solvent interaction. Nonlinear plots of log k with D −1 suggest that changes in the solvent structure are an important factor that influences these rates. The influence of the added cosolvent on reactivity was analyzed in light of various simple and multiple regression equations using Kirkwood, E T (30), and Kamlet-Taft parameters. The obtained results showed that the solvation phenomenon plays a dominant role in the aquation. C 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: [230][231][232][233][234][235][236][237] 2011