N -Alkyl 4,4'-bipyridylium salts were synthesized and characterized. Cyclic voltammetry investigation showed that monosubstited 4,4'-bipyridylium salts are prone to reversible single-electron reduction. The formal redox potentials vs. a saturated silver chloride electrode were determined for different potential sweep rates. High-resolution ESR spectra of the radical cations formed upon the reduction of N-substituted 4,4'- bipyridylium salts in acid media were measured and interpreted. The substituent structure and the type of anion in the molecule have a considerable effect on the spin density distribution, current–voltage characteristics, and elctrooptical properties. The applicability of monosubstituted 4,4'-bipyridylium salts as photoelectrochromic compounds was studied.

Symmetric N , N ′-disubstituted salts of 4,4′-bipyridyl (viologens) are synthesized and described. It is shown by cyclic voltammetry that disubstituted salts of 4,4′-bipyridyl have a tendency toward reversible two-electron reduction. Normal first and second step oxidation-reduction potentials with respect to saturated silver chloride electrodes at various potential scan rates are found. The spectra of the high-resolution electron paramagnetic resonance of viologen cation radicals formed during the reduction of N , N ′-disubstituted salts of 4,4′-bipyridyl are obtained and interpreted. It is established that the nature of substitutes and counterions in a viologen molecule considerably influences the distribution of its spin density, voltammetric curves, and electro-optical properties.

Semi-empirical PM3 method for the quantum calculations of molecular electronic structure based on NDDO integral approximation is used to investigate the complex formation of monosubstituted 4,4′-bipyridinium salts BpyR (Hal) containing a halide anion interacting with the quaternary nitrogen atom and carboxylic group of the two-units construct. Significant effect of the BpyR (Hal) electronic structure is unveiled that contributes in two different structures of these salts, namely, partial charge transfer complex and ion pair structure, both having stable energy minima. We demonstrate that (i) the structure of the N-substituent modulates the energy and electronic characteristics of monosubstituted salts BpyR with chlorine and bromine anions and (ii) the coulomb interactions between quaternary N-atom, halogen anion, and the proton of carboxylic group stimulate the transformation of the charge transfer complex into the ion pair structure. Results of calculations are compared with the experimental FTIR spectra of blends of BpyR(Hal) with Eudragit copolymer.

The mass spectrometric behavior of symmetrically disubstituted 4,4′-bipyridinium salts under electron ionization (EI), electrospray ionization (ESI), direct analysis in real time (DART) ionization, and matrix-assisted laser desorption-ionization (MALDI) has been investigated. Electron ionization spectra were recorded using the direct injection of the probe at elevated temperature, when the salts were decomposed with the loss of counter-ions. In the case of ESI, primary ions are radical cations [Cat]+· and cations [Cat-H]+, decomposed further by the loss of N-substituents. More complicated DART spectra revealed the peaks characterizing both bipyridyl group and organic substituents. MALDI spectra were rather simple and contained the peaks for [Cat]+ · ions that are structurally identical to radical cations formed during the reduction of the salts in solution. Among all the methods, DART and MALDI are suitable for the qualitative analysis of such bis-quaternary salts, while ESI is convenient for the quantitative analysis of these analytes.

New composite electrochromic systems combining the advantages of low-molecular-mass organic electrochroms-high molar-absorption coefficients in the colored state and high switching rates-with good properties of polymers-such as mechanical strength and film-formation ability-are prepared through the incorporation of low-molecular-mass viologens into a carboxyl-containing polymer matrix via noncovalent binding. The formation of noncovalently bound polymer-viologen complexes is confirmed by IR and UV spectroscopy. It is found that the degree of substitution in a viologen molecule strongly affects the character of interaction with the polymer matrix and the electrochromic properties of the composite.

The effect of internal and external electron donors on the polymerization of propylene in a liquid monomer or a hydrocarbon diluent (hexane) in the presence of a titanium-magnesium nanocatalyst activated with an organoaluminum compound (triethylaluminum, triisobutylaluminum) and the properties of the resulting PP are studied. The polymerization of propylene in the absence of internal and external donors yields atactic PP, whereas, in the presence of a catalyst containing an aryl internal donor, isotactic PP is formed. The activity and stereospecificity of the catalytic system substantially depends on the method of electron-donor introduction. The thermal treatment of the catalyst with an electron donor affects its activity and stereospecificity.