Synthesis of 4H-3,3a-dihydrothiazolo[4,3-b]quinazolines

Regiospecific synthesis of 4H-3,3a-dihydrothiazolo[4,3-b]quinazolines and 7-methyl-4H-3,3a-dihydrothiazolo[4,3-b]quinazolines IVa and IVb is described. The N-substituted thiazolidinecarboxylic acids Ia and Ib were converted to the corresponding acid chlorides, IIa and IIb but neither reacted with silver trifluoromethanesulphonate. The carboxylic acids Ic and Id were however, decarboxylated to the corresponding iminium ions using phosphorus oxychloride and these afforded the nitroamines IIIa and IIIb. Reductive cyclisation led to the quinazolines IVa and IVb.     

Polycyclic nitrogen compounds. Part II. Tricyclic quinoxalinones and their 4- or 6-aza analogues

1,2,3,3a-Tetrahydro-9-nitropyrrolo[1,2-α]quinoxalin-4-one and 7,8,9,10-tetrahydro-3-nitropyrido[1,2-α]quin-oxalin-6-one (V-VI) were reduced and deaminated to give new parent tricyclic quinoxalinone skeletons I-II. The latter compounds were identical with the tricycles obtained by an unambiguous independent synthesis. New 6-aza-1,2,3,3a-tetrahydropyrrolo[1,2-α]quinoxalin-4-one (III) and 4-aza-7,8,9,10-tetrahydropyrido[1,2-α]-quinoxalin-6-one (IV) were prepared by selective hydrogen transfer reductive cyclisation of esters of N-(2-nitro-3-pyridyl)pyrrolidine-2-carboxylic acid and N-(2-nitro-3-pyridyl)piperidine-2-carboxylic acid (Xb and XIb) respectively.     

Polycyclic nitrogen compounds. Part I. Synthesis of new heterotricyclic quinoxalinones with bridgehead nitrogen atoms

New tricyclic quinoxalinone skeletons with a fully-reduced ring ‘C’ -1,2,3,3a-tetrahydropyrrolo[1,2-α]quin-oxalin-4-one (I-II) and 7,8,9,10-tetrahydropyrido[1,2-α]quinoxalin-6-one (III-IV) derivatives were obtained by selective hydrogen transfer reductive cyclisation of N-(2-nitrophenyl)pyrrolidine-2-carboxylic acid esters and N-(2-nitrophenyl)piperidine-2-carboxylic acid esters (VIa,b and VIIIa,b), respectively.     

Novel fluorescent probe as aggregation predictor and micro-polarity reporter for micelles and mixed micelles

Aggregational behaviour of micelles sodium dodecyl sulphate (SDS and Triton X-100, TX-100 both in pure and mixed form) and micelle like aggregates such as polymer-surfactant system [polymer poly(vinyl pyrrolidone), PVP]-SDS have been studied by using fluorescence characteristics of a newly synthesized probe. The critical micelle concentration (CMC) values determined at various surfactant compositions are lower than the ideal values indicating a synergistic effect. The value of the interaction parameter for the surfactant mixture has been determined which agrees well with the value calculated according to molecular thermodynamic theory. The total aggregation number of surfactant in mixed micelle shows a drastic variation in the SDS mole fraction range 0 < or = alpha1 < or = 0.3 and beyond the range it remains practically constant. Molar-based partition coefficients for the dye between the micellar and aqueous phase have been determined and a non-linear variation is obtained for the mixed micellar system. Variations of micro-polarity in the mixed micellar region have been investigated as a function of surfactant composition and results have been explained in terms of a suitable realistic model.     

Synthesis,Photophysics and Nonlinear Optical Properties of Stilbenoid Pyrimidine‐Based Dyes Bearing Methylenepyran Donor Groups

The nonlinear properties and the photophysical behavior of two π‐conjugated chromophores that incorporate an electron‐deficient pyrimidine core (A) and γ‐methylenepyrans as terminal donor (D) groups have been thoroughly investigated. Both dipolar and quadrupolar branching strategies are explored and rationalized on the basis of the Frenkel exciton model. Even though a cooperative effect is clearly observed if the dimensionality is increased, the nonlinear optical (NLO) response of this series is moderate if one considers the nature of the D/A couple and the size of the chromophores (as measured by the number of π electrons). This effect was attributed to a disruption in the electronic conjugation within the dyes’ scaffold for which the geometry deviates from planarity owing to a noticeable twisting of the pyranylidene end‐groups. This latter structural parameter also has a strong influence on the excited‐state dynamics, which leads to a very efficient fluorescence quenching.     

Circular polarization of ion fluorescence completing the analysis of resonant Xe* 4d(-1)(5/2)6p Auger decay

The relative contributions of the partial electron waves emitted in the Auger decay of the Xe* 4d(-1)(5/2)6p(J(*)=1) resonance have been determined by fluorescence polarimetry after excitation with circularly polarized synchrotron radiation. The analysis of circularly polarized fluorescence of the photoion leads to an independent determination of the orientation parameters for all states of the Xe II 5p(4)6p multiplet. The present study provides, in combination with data on the angular distribution and spin polarization of the Auger electrons, complete quantum mechanical information on the resonant Auger decay, i.e., branching ratios and relative phases of the Auger decay amplitudes.     

Photophysics of representative ketocyanine dyes: dependence on molecular structure

Spectral properties of a new fluorescent ketocyanine dye have been discussed. The energy of maximum absorption/fluorescence of the dye exhibits bathochromic shift with increasing polarity of the medium. Both dipolarity-polarisability and hydrogen bond donation interaction contribute to solvation of the dye. Study of fluorescence parameters points to existence of different emitting states of the dye for aprotic and protic solvents. While the emitting state is the (1)(π, π*) state for aprotic solvents, fluorescence supposedly take place from a different emitting state involving H-bond formation in the excited state in protic solvents. Fluorescence parameters of the dye have been compared with those for a structurally similar symmetric ketocyanine dye. The faster decay of the dye relative to its symmetric counterpart has been explained as due to an increase of nonradiative decay.     

The excited state dipole moments of betaine pyridinium investigated by an innovative solvatochromic analysis and TDDFT calculations

This work reports on the solvatochromic properties of a simple heterocyclic betaine pyridinium, 2-(1-pyridinio)benzimidazolate (SBPa), having promising potentialities in non-linear optics. From advanced PCM-TDDFT calculations, the solvatochromism of SBPa was found to be unusual, involving two different electronic states for absorption (S(0)→ S(2)) and emission (S(1)→S'(0)). To account for this behavior, we developed an innovative physical treatment which consists in a non-linear fit of the solvatochromic data using the Bilot-Kawski theoretical model and visualizing the least-square coefficient χ(2) on a 2D map as a function of the solute polarizability and gas phase absorption energy. In parallel, Kamlet-Taft correlations were undertaken to select a propitious set of electrostatic solvents usable in this treatment. Protic solvents that lead to specific interactions and nonpolar solvents that favor dimerization processes were excluded. From a choice of aprotic solvents with sufficiently high polarity, 4 dipole moments μ(g)(S(0)) = +9.1 D, μ(e)(S(2)) = -1.5 D, μ(e)(S(1)) = 0 D and μ(g)(S'(0)) = +3.31 D were determined, the 3 former values being in close agreement with TDDFT values, although the solute polarizability values seem underestimated. Anyhow, disregarding this discrepancy, we evaluated the static hyperpolarizability to β(0) = -64 × 10(-30) esu from the solvatochromic data in close agreement with DFT calculations.     

Effect of low intensity helium-neon (HeNe) laser irradiation on experimental paracoccidioidomycotic wound healing dynamics

The effect of HeNe laser on the extracellular matrix deposition, chemokine expression and angiogenesis in experimental paracoccidioidomycotic lesions was investigated. At days 7, 8 and 9 postinfection the wound of each animal was treated with a 632.8 nm HeNe laser at a dose of 3 J cm(-2). At day 10 postinfection, the wounds were examined by using histologic and immunohistochemical methods. Results revealed that laser-treated lesions were lesser extensive than untreated ones, and composed mainly by macrophages and lymphocytes. High IL-1beta expression was shown in the untreated group whereas in laser-treated animals the expression was scarce. On the other hand, the expression of CXCL-10 was found to be reduced in untreated animals and quite intensive and well distributed in the laser-treated ones. Also, untreated lesions presented vascular endothelial growth factor (VEGF) in a small area near the center of the lesion and high immunoreactivity for hypoxia-inducible factor-1 (HIF-1), whereas laser-treated lesions expressed VEGF surrounding blood vessels and little immunoreactivity for HIF-1. Laser-treated lesions presented much more reticular fibers and collagen deposition when compared with the untreated lesion. Our results show that laser was efficient in minimizing the local effects observed in paracoccidioidomycosis and can be an efficient tool in the treatment of this infection, accelerating the healing process.