Spectral investigation of intramolecular interaction in sulfur-organic compounds

Earlier¹ it was reported that 4-aryl-4,5-dihydrothiophene-1,1-dioxides (I) are converted in aqueous and alcohol solution of bases to isomeric 3-aryl-2,5-dihydrothiophene dioxides (II) and 3-aryl-4,5-dihydrothiophene-1,1-dioxides (III) (Fig. 1).In the presence of electron-donor substituents in the p-position of the phenyl ring, IIb, c compounds are practically irreversibly isomerised to III b, c. For unsubstituted phenyldihydrothiophene-1,1-dioxides IIa and IIIa the reaction proceeds riversibly but equilibrium is shifted towards isomer IIIa indicating its high thermodynamic stability. It is known² that 2,5-dihydrothiophene-1,1 -dioxide is more stable than 4,5-dihydrothiophene-1,1-dioxide. Consequently, the observed stability increase of 3-aryl-4,5-dihydrothiophene-1,1-dioxides (IIIa–c) is due to interaction of the substituent C₆H₄X with the sulfonyl group. This paper investigates the nature of this interaction.     

Electronic nature of substituents and the structure of 4,4′-dipyridylium dications: Crystal structure of <Emphasis Type="Italic">N,N′</Emphasis>-di(2-carboxyethyl)-4,4′-dipyridylium diperchlorate

The crystal structure of N,N′-di(2-carboxyethyl)-4,4′-dipyridylium diperchlorate, C₁₆H₁₈Cl₂N₂O₁₂, is determined using X-ray diffraction analysis at 293 K. The crystals are orthorhombic, a = 20.084(4) Å, b = 8.687(2) Å, c = 11.725(2) Å, space group Pna2₁, and Z = 4; 1688 reflections measured; and R = 0.056 and R _w = 0.059 for 1244 reflections with I > 3σ(I). It is found that, in the absence of charge transfer or short intramolecular O?N contacts, the nucleus of the dication adopts a twist conformation (the angle of rotation between the planes of the pyridine rings is equal to 23°).     

Intramolecular interaction in aryldihydrothiophene 1,1-dioxides

The peculiarities of the intramolecular interaction in unsaturated five-membered cyclic sulfones as a function of their structures were studied on the basis of an analysis of the electronic absorption spectra of single crystals of isomeric -aryldihydrothiophene 1,1-dioxides at 4.2°K, the IR spectra of the molecules at 298°K, and the results of x-ray diffraction analysis of 3-phenyl-4,5-dihydrothiophene 1,1-dioxide. In addition to the inductive effect, conjugation of the SO₂ group with the -electron system of 3-phenyl-4,5-dihydrothiophene 1,1-dioxide, which is manifested most appreciably in the excited electronic state, was observed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1056–1059, August, 1977.     

Effect of spin-orbit coupling in para-dihalogenobenzenes on the environment-induced frequency changes in their S1 ← S0 spectra

The consequences of spin-orbit coupling in p-dihalogenobenzenes for solvent-induced shifts or S₁ ← S₀ spectral transitions, and for changes of S₁-state vibrational frequencies compared with the S₀ state, are assigned to mixing low-energy triplet states into the singlet-state system.     

Electronic spectra and molecular symmetry for some aromatic compounds

Interpretations are given for the electronic absorption spectra of crystals of alkylbenzenes and benzene itself; these are based on molecular models that include somewhat out-of-plane positions for the carbon atoms in the benzene ring. The relation of stability and specific properties to structure for aromatic hydrocarbons is discussed.     

Nonlinear optical properties of composites based on conductive metal-alkanoate liquid crystals

The dynamic holography in new composite materials based on a novel class of metal-alkanoate ionic liquid crystals (ILCs) is studied experimentally and theoretically. The composites are formed as a dielectric dye film covered by lyotropic metal-alkanoate ILC and ionic smectic glasses with doped dye molecules. The dynamic gratings are created by nanosecond pulses of double frequency Nd:YAP laser, the recording demonstrates fast erasure time of residual thermal gratings. The nonlinear optical properties are determined by the resonance nonlinearity in photosensitive centres of ILC. Note, that permanent relief gratings will be formed on a dielectric dye film only as well as in composite cells either with nematic LC or with polymers under action of pulsed laser radiation. Lyotropic ILC layer applied over the dye film provides the dynamic regime of grating recording in composite cells. We found a secondary thermal grating is much smaller, the conductive ILC matrix provides effective heat dissipation and erasure of this thermal grating. A theory of Raman-Nath self-diffraction holography on thin films followed from the wave equation and the nonlinear mechanism of absorption saturation is developed to explain experimental results.