Interactions between 3H-indole derivatives, their cations and anions, and microheterogeneous environments like micelles and vesicles have been studied extensively in our laboratory recently. We report herein the interactions of 2-(p-aminophenyl)-3,3-dimethyl-5-cyano-3H-indole (1) and 2-[p-(dimethylamino)phenyl]-3,3-dimethyl-5-cyano-3H-indole (2) with aqueous solutions of β-cyclodextrin (β-CD), studied by absorption and fluorescence steady-state and time-resolved measurements. The stoichiometries of the cyclodextrin:guest inclusion complexes have been determined by steady-state fluorescence measurements. The data reveal that two types of complexes, i.e., 1:1 and 2:1 types are formed. Thermodynamic parameters are calculated at six different temperatures. Spectral characteristics, bandwidths, and photophysical parameters indicate that molecule 2 is better protected against hydrophilic interactions. Protonation reactions carried out at different concentrations of β-CD show that the protonation is inhibited at the indolic nitrogen, contrary to what was observed in other microheterogeneous media. Time-resolved measurements and global analysis of the results are best described by a discrete triple exponential decay law clearly indicating that the guest molecules experience three different environments in aqueous solutions:  bulk water and a stepwise 1:1 and 2:1 (β-cyclodextrin:guest) inclusion complexation. The effective polarity of the cyclodextrin cavity is equivalent with the polarity of an 80:20 methanol−water mixture at the β-CD rim where the indolic (tertiary) nitrogen is likely to be located near the “alcoholic” secondary rim of the macrocycle.

We report on the rotational diffusion and vibrational population relaxation dynamics of the probe molecules perylene and 1-methylperylene in selected aliphatic aldehyde and ketone solvents. The reorientation data demonstrate that, for both solvent systems, there is a change in the nature of the solvent−solute interactions with both probe molecules as the hydrodynamic volume of the solvent molecules approaches that of the probes. The solvent-dependent change in behavior occurs for different solvent aliphatic chain lengths in the two systems. Vibrational population relaxation measurements for two probe molecule vibrational modes reveal efficient intermolecular coupling in all cases. The data point to the role of the solvent aldehyde proton in mediating solvent−solvent and solvent−solute interactions, leading to chromophore dynamics reminiscent of those seen in the n-alcohols. Reorientation of the two probes in the ketones yields results that are more consistent with those seen in the alkanes, suggesting the relative weakness of dipole−induced dipole interactions relative to hydrogen-bonding interactions in the solvation of perylene and 1-methylperylene.

Electroreduction of Ni(II) and Co(II) has been carried out in aqueous mixtures of formamide, acetamide and urea. Electrode kinetics in terms of theories of irreversible waves have been studied. After calculating the rate constants by DELAHAY1 and Kou-TECKY2 treatments separately their variation with electrode potential has been used to calculate the product ‘ana’. The rate constants and ‘ana’ calculated from two different approaches show remarkable agreement. `ana’ records a gradual decrease with increasing amide content of the aqueous mixture.