Novel intramolecular rearrangement leading to the synthesis of biheterocyclic indole-benzoimidazole derivatives on solid phase

[reaction: see text] A novel intramolecular SNAr rearrangement observed during the S-alkylation of benzoimidazole-2-thione with alpha-haloacetophenone is reported. The rearrangement led to the formation of a new benzoimidazole-based intermediate, which is further utilized for the generation of a new biheterocyclic indole-benzimidazole derivatives with a two-point diversity.     

Baryogenesis and damping in nonminimal electroweak models

We calculate the baryon asymmetry of the Universe in the standard model of the electroweak theory with CP violation appropriate for simple extensions of the Higgs sector. The propagation of quarks of masses up to about 5 GeV are considered, taking into account the effect of damping rate. We find that the contribution of the b quark can still account for the observed baryon asymmetry to within the theoretical uncertainties of such models.

     

Laser optogalvanic spectroscopy of argon in the wavelength region 605–740 nm

Two-photon optogalvanic transitions in Ar glow discharge with Nd: YAG laser pumped dye laser excitation in the frequency range 13520–16520 cm⁻¹ has been studied using linear and circular polarization. The intensities of two-photon optogalvanic transitions are very sensitive to changes in the incident laser power which is not the case with one-photon transitions. Intensity ratio for circular and linear polarized light for two photon transitions 6s′[1/2]°1←4s[3/2]°2, 6s′[1/2]°0←4s[3/2]°2, and 5d[1/2]°0←4s[3/2]°2, 5d[1/2]°1←4s[3/2]°2 are quite different from the other two-photon transitions. This has been explained as due to near one photon resonance of 4p′[3/2]1 level for the first pair and 4p′[1/2]1 for the second pair of transitions. The ratio of optogalvanic intensity for circular to linear polarized light has been theoretically estimated and compared with the observed results.     

Distinguishability ofSU(2)×U(1)×U′(1) andSO(10) gauge models from the Weinberg-Salam model

The predictions ofSU(2)×U(1)×U′(1) andSO(10) gauge models for the asymmetry parametersA-,B-,C _L andC _R in the deep inelastic scattering of polarized electrons and positrons by unpolarized protons and deuterons are compared with those calculated in the Weinberg Salam model for different values ofy. The model based on,SU(2)×U(1)×U′(1) group has been found almost indistinguishable from the Weinberg Salam model with regard to the parametersA-,B- andC _L (except forB- in the region 0≦y≦0.2) althoughC _R exhibits marked distinguishability. TheSO(10) model, for certain choice of its model parameters, can be distinguished from the Weinberg Salam model through measurement of the asymmetry parameters for different values ofy.     

Effects of liquid crystal environment on the spectroscopic and photophysical properties of well-known reacting systems 2,3-dimethylindole (DMI) and 9-cyanoanthracene (9CNA)

Electrochemical and steady-state and time-resolved spectroscopic studies on a disubstituted indole, 2,3-dimethylindole (DMI), and well-known electron acceptor 9-cyanoanthracene (9CNA) in liquid crystal (LC) 4-(n- pentyl)-4'-cyanobiphenyl (5CB) environment demonstrate entirely different spectroscopic and photophysical behaviors from those observed earlier by our research group with the same reacting systems in isotropic media n-heptane and acetonitrile (ACN). From the UV-vis absorption spectral measurements of the donor DMI in the presence of the acceptor 9CNA in liquid crystal medium (in 5CB) in various temperatures above the nematic-isotropic phase transition from 308 to 313 K (pseudo-ordered domain), it was observed that the lower energy lying absorption band of DMI situates in a longer wavelength region than the corresponding band observed in isotropic medium n-heptane or ACN. The possibility of the photochromic effect is discussed. In this band, the degree of mixing of the two closely spaced electronic states (1)L(a) (S(2)) and (1)L(b) (S(1)) of DMI was very prominent in the ordered LC environment (5CB) whereas in isotropic medium the dominant contribution for the formation of the lower energy band system primarily originates from the (1)Lb (S(1)) state, as evidenced from the steady-state polarization measurements. Both steady-state fluorescence quenching and time-resolved fluorescence studies clearly demonstrate in favor of the presence of only the static mode in LC environment. The situation differs in isotropic media where the dynamic process possesses the key role in the quenching mechanism. Expectedly, the transient absorption measurements by the nanosecond laser flash photolysis technique show a lack of formation of transient ionic species in the pseudo-ordered domain of 5CB. On the contrary, in isotropic solvents n-heptane and ACN, the transient absorption spectra measured by the same nanosecond laser flash photolysis technique exhibit the broad band of 9CNA radical anion at around 560 nm (9CNA-) and the band of neutral radical of DMI at 540 nm. It is inferred that the charge-separation reactions occurring within the present intermolecular systems could be stopped significantly by changing the nature of the environment from the isotropic to the LC's pseudo-ordered domain which situates closely above the nematic (N)-isotropic (I) phase transition temperature. From the steady-state and time-resolved investigations, it is revealed that, due to the hysteresis phenomenon, the nematic phase properties persist over a wide temperature range well within pseudo-ordered domain to some extent into the isotropic phases. The investigations with the different donor-acceptor inter- and intramolecular systems in 5CB and some other LC's environment are underway.