Coordinated Projects

The preferential solvation of 8-N,N-(dimethylamino)-11H-indeno[2,1-a]pyrene, Py(S)DMA, in its transient charge transfer (CT) state in binary solvents such as toluene/DMSO liquid mixtures was studied by means of frequency-domain fluorometry. The data obtained were considered within the following kinetic scheme: the preferential solvation was described by the system of consecutive reversible reactions of which each step is associated with the absorption of one DMSO molecule in the first solvation shell of the fluoresent Py(S)DMA dipolar CT molecule. [...]

Based on experimental data a kinetic model is presented that adequately describes the main features of preferential solvation of a charge-transfer dipole in binary mixtures. 8-(N,N-dimethylamino)-11H-indeno[2,1-a]pyrene is used as fluorescent probe in toluene/DMSO mixtures. [...]

The intramolecular electron hopping in cation dimer radicals of 1,n-bis(N-carbazolyl) alkanes for n = 3,4 that are produced via photoinduced electron transfer to 1,4-dicyanobenzene (DCNB) has been studied by means of the exciplex fluorescence detected magnetic field effect (MFE) in a 18 vol % mixture of dimethylformamide with tetrahydrofuran. It has been found that on passing from a single cation radical of N-methylcarbazole to the cation dimers, the parameter B1/2 decreases from ca. [...]

Using the picosecond spectro-streak method we monitored the dynamics of preferential solvation of charge-transfer dipoles in binary mixtures of solvents strongly different in dielectric constants. The observed slow (⩽1 ns) (⩽1 ns) spectral red-shift of the charge-transfer (exciplex) fluorescence is considered to be mainly due to the formation and the dielectric enrichment of the solvation shell around the solute molecules in their dipolar excited charge transfer state by diffusion of polar molecules from the bulk of the solvent mixture. [...]

We present the results of light scattering and turbidity experiments along the initial part of the binodals in nonionic oil-in-water microemulsions. The data permit evaluating the mean radii of the oil globules at their (lower) stability limit [...]

Magnetic field effects (MFE) detected by intramolecular exciplex fluorescence have been studied in acetonitrile solutions for new donor−acceptor compounds in which pyrene is linked to aza-15-crown ether by a polymethylene chain with 3, 9, and 16 CH2 units. It was found that addition of alkali and alkaline-earth ions to the solutions decreases the observable MFE. [...]

Magnetic field effects of radical ion pair reactions detected by exciplex fluorescence spectroscopy were studied in pyrene/aza-15-crown-5 solutions in mixtures of either dimethyl sulfoxide (25 vol %) or acetonitrile (35 vol %) with toluene or benzene at room temperature. It was found that, unlike the extensively studied pyrene/aromatic amine system, the half saturation fields (B1/2 = 41−52 G, depending on solvents) are almost independent of azacrown concentration [...]

Assuming the globules at the (lower) stability limit of (diluted) nonionic o/w microemulsions in the water-rich corner of the phase prism to be spherical, and assuming, furthermore, the mean curvature of the (saturated) interfacial layers to decrease monotonically with rising temperature, it is shown that the size distribution of the globules must change to a lower number density of larger nonspherical globules upon raising temperature at fixed mean composition simply for volumetric reasons, irrespective of the explicit expression for the temperature dependence of the mean curvature. Applying Flory's model, it is, furthermore, shown that this could explain the phase separation of o/w microemulsions at their upper stability limit in the water-rich corner. [...]