Synthesis, Characterization, Optical Properties and Theoretical Studies of Novel Substituted Imidazo[1,5-a]pyridinyl 1,3,4-Oxadiazole Derivatives

Novel imidazo[1,5-a]pyridinyl 1,3,4-Oxadiazole derivatives were synthesized and characterised by IR, ¹H NMR and HRMS.UV-vis absorption and fluorescence properties of these compounds in different solutions showed that the maximal emission wavelength was not significantly changed in different solvents; however, maximum absorption wavelength was blue-shifted with the increase of solvent polarity. Absorption λ_max and emission λ_max was less correlated with substituent groups on benzene rings. The calculated molecular orbital correlates well with their absorption.     

Push-Pull Fluorophores Based on Imidazole-4,5-dicarbonitrile: A Comparison of Spectral Properties in Solution and Polymer Matrices

Spectral properties of novel type of fluorophores consist of a π-conjugated system end-capped with an electron-donating N,N-dimethylaminophenyl group and an electron-withdrawing imidazole-4,5-dicarbonitrile moiety were examined. An additional π-linker separating these two structural units comprises simple bond (B1P), phenyl (B2B), styryl (B3S) and ethynylphenyl (B4A) moieties. The absorption and fluorescence spectra were taken in cyclohexane, chloroform, acetonitrile, methanol and in polymer matrices such as polystyrene, poly(methyl methacrylate) and poly(vinylchloride). The longest-wavelength absorption band was observed in the range of 300 to 400 nm. Intense fluorescence with quantum yields of 0.2 to 1.0 was observed in cyclohexane, chloroform and in polymer matrices within the range of 380 to 500 nm. The fluorescence was strongly quenched in neat acetonitrile and methanol. The fluorescence lifetimes are in the range of 1–4 ns for all measured fluorophores. The large Stokes shift (4,000 to 8,000 cm⁻¹) indicates a large difference in the spatial arrangement of the chromophore in the absorbing and the emitting states. The observed fluorescence of all fluorophores in chloroform was quenched by 1-oxo-2,2,6,6-tetramethyl-4-hydroxy piperidine by the diffusion-controlled bimolecular rate (cca 2 × 10¹⁰ L mol⁻¹ s⁻¹). Polar solvents such as acetonitrile and methanol quenched the fluorescence as well but probably via a different mechanism.     

瓜环与咪唑[4,5,f]-1,10-菲咯啉衍生物相互作用模式的测试

以合成的三种的咪唑[4,5,f]-1,10-菲咯啉衍生物为客体,以瓜环(cucurbit[n]uriln=6～8)为主体,利用1H NMR技术,荧光光谱和紫外吸收光谱方法,测试了主客体相互作用形式、形成包结物的结构特征及其光学性质,三种方法得到的结果相同.研究表明,六元瓜环(Q[6])仅能与2-(4-甲基苯基)-咪唑-[4,5,f]菲咯啉(W1)盐酸盐相互作用(包结比为1:1);七元瓜环(Q[7])与三种客体2-(4-甲基苯基)-咪唑-[4,5,f]菲咯啉,2-(2-甲基苯基)-咪唑-[4,5,f]菲咯啉(W2)以及2-(3-甲氧基苯基)-咪唑-[4,5,f]菲咯啉(W3)的盐酸盐均以1:1的物质的量比发生相互作用;而八元瓜环(Q[8])除与W1形成的是1:2的包结物外,与另外两种客体W2,W3也是形成1:1的包结配合物.     

Mass Spectral Fragmentation Patterns of Some Substituted 10,Ll-Dihydro-5H-Dibenzo[A,D] Cycloheptene-5-One and 9,10-Dihydro-4H-Benzo [4,5]Cyclohepta[1,2-B]Thiophene-4-One

Electron impact mass spectra of some substituted 10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-one and 9,10-dihydro-4H-benzo[4,5] cyclohepta[1,2-b] thiophene-4-one have been recorded and the identity of various ions in the mass spectra established. Substituted dibenzosuberones (2-6) exhibit one main fragmentation route, which include the elimination of the tropolone molecule from the dibenzosuberone fragment cation. Their monothiophene analogues(7-11) exhibit characteristic CO elimination from the molecular ion and formation of corresponding naphtho[1,2-b]thiophene radical cation which after elimination of CS or HCS from the thiophene nuclei give rise to the benzotrophyne radical cation.     

Synthesis and optical properties of novel pyrido[1,2-a]benzimidazole-containing 1,3,4-oxadiazole derivatives

A series of novel substituted 1,3,4-oxadiazole derivatives containing pyrido[1,2-a]benzimidazole moiety were synthesized and characterized using FTIR, ¹H NMR, ¹³C NMR, and HRMS. An efficient tandem reaction was employed as a key step in constructing the pyrido[1,2-a]benzimidazole moiety under very mild condition. The structure of compound 4a was established by X-ray crystallography. The UV-vis absorption and fluorescence spectral characteristics of these compounds were investigated in several solvents. Compounds 4a-i display similar absorptions, with absorption peaks ranging from 330 to 339 nm in acetonitrile, while the absorption maxima of compound 4j bearing a diphenylamino group on the benzene ring is red-shifted distinctly to 377 nm due to the strong electron-donating property of its substituent and extended π-conjugated system. All these target heterocyclic compounds present blue-green emissions (461-487 nm) in dilute solutions and show high quantum yields of fluorescence (Ф_PL=0.65−0.99) in dichloromethane.     

Synthesis and Fluorescence Studies of Some New Fluorophores and Their Effect on Hybridization of Oligodeoxyribonucleotides

Some novel fluorophores, viz. 6-(6-isobutyrylamino-1,3-dioxo-1H,3H-benzo[de]isoquinolin-2-yl)-hexanoic acid (1), 6-(6-dimethylamino-1,3-dioxo-1H, 3H-benzo[de]isoquinolin-2-yl)-hexanoic acid (2), 6-(6-benzoylamino-1, 3-dioxo-1H, 3H-benzo[de]isoquinolin-2-yl)-hexanoic acid (3), 6-(6-amino-1-oxo-1H, 3H-benzo[de]isoquinolin-2-yl)-hexanoic acid (4) and 6-(6-amino-1H,3H-benzo[de] isoquinolin-2-yl)-hexanoic acid (5) have been designed, synthesized and characterized. Their comparative fluorescence has been studied in different organic solvents and aqueous solutions containing inorganic ions. Out of these, two fluorophores, 1 and 2 have been used for labelling of nucleosides which were finally converted into their phosphoramidites, and used for labelling of oligodeoxyribonucleotides through covalent attachment. These fluorophores after attachment on oligodeoxyribonucleotides showed good fluorescence signals and higher hybridisation affinity than unlabelled oligodeoxyribonucleotides.     

Preparation of a Novel pH-responsive Fluorescent Probe Based on an Imidazo[1,2-a]indole Fluorophore and its Application in Detecting Extremely Low pH in Saccharomyces cerevisiae

A novel pH-responsive probe based on an imidazo[1,2-a]indole fluorophore architecture is reported. The probe was highly selective to strongly acidic pH (pK_a = 3.56) with high sensitivity and a fast response time (within 30 s). The probe did not demonstrate any fluorescence changes in the presence of interfering metal ions, and it featured excellent reversibility under strongly acidic conditions. The mechanism of detection of the probe was determined to be based on intramolecular charge transfer (ICT) at different pH. The probe was also able to be used for imaging for detecting acidic pH in Saccharomyces cerevisiae.

     

Synthesis and evaluation of ursolic acid-based 1,2,4-triazolo[1,5-a]pyrimidines derivatives as anti-inflammatory agents

Here, two series of novel ursolic acid-based 1,2,4-triazolo[1,5-a]pyrimidines derivatives were synthesized and screened for their anti-inflammatory activity by evaluating their inhibition effect of using LPS-induced inflammatory response in RAW 264.7 macrophages in vitro; the effects of different concentrations of the compounds on the secretion of nitric oxide (NO) and inflammatory cytokines including TNF-α and IL-6 were evaluated. Their toxicity was also assessed in vitro. Results showed that the most prominent compound 3 could significantly decrease production of the above inflammatory factors. Docking study was performed for the representative compounds 3, UA, and Celecoxib to explain their interaction with cyclooxygenase-2 (COX-2) receptor active site. In vitro enzyme study implied that compound 3 exerted its anti-inflammatory activity through COX-2 inhibition.

     

2-（4，5-二硫甲基-1，3-二硫环戊烯基）-3，4-富勒吡咯烷的合成表征及电子光谱的INDO/ S研究

通过亚胺叶立德与C60 发生 1,3 偶极环加成反应的方法 ,合成了一种新的具有分子内给 受体系的C60吡咯烷衍生物 2 (4 ,5 二硫甲基 1,3 二硫环戊烯基 ) 3,4 富勒吡咯烷 (C66H9NS4) ,以红外、元素分析、核磁共振氢谱、紫外进行了表征 .运用Gaussian98量子化学程序包 ,利用密度泛函的方法对分子的几何构型进行了优化 ,在优化的基础上 ,应用INDO/S的方法计算了化合物的电子光谱 ,计算结果表明 ,C66H9NS4的光谱吸收在 4 38.9nm ,与实验值 4 31.4nm基本一致     

Anchoring of Fluorophores to Plasma-chemically Modified Polymer Surfaces and the Effect of Cucurbit[6]uril on Dye Emission

Polypropylene supports were functionalized by plasma-deposition of polymeric allylamine layers. The surface amino groups generated were wet-chemically reacted with xanthene dyes resulting in fluorescent polymer films. The effect of polymer-attachment of the dyes on their emission features was studied fluorometrically and different methods were tested to improve the fluorescence properties of the films. Modification with cucurbit[6]uril (CB6) yields a moderately enhanced fluorescence as well as an improved photostability. The observed effect is most likely due to CB6-induced rigidization of the linker molecules which seems to reduce fluorescence quenching dye–dye and fluorophore–surface interactions.     

Ultrasound assisted one-pot, three-components synthesis of pyrimido[1,2-a]benzimidazoles and pyrazolo[3,4-b]pyridines: A new access via phenylsulfone synthon

A simple, facile, efficient and three-components procedure for the synthesis of pyrimido[1,2-a]benzimidazoles and pyrazolo[3,4-b]pyridines utilizing phenylsulfone synthon, under ultrasonic irradiation was developed.     

Design,synthesis, and molecular docking studies of new [1,2,4]triazolo[4,3-a]quinoxaline derivatives as potential A2B receptor antagonists

Molecular Diversity - Many shreds of evidence have recently correlated A2B receptor antagonism with anticancer activity. Hence, the search for an efficient A2B antagonist may help in the...     

Electronic Spectral Studies and Determination of the First Excited Singlet-State Dipole Moments of New Benzo[a]phenothiazine Derivatives

The room temperature (298 K) electronic absorption, and fluorescence excitation and emission spectra of seven new, pharmacologically-important benzo[a]phenothiazines (12H-benzo[a]phenothiazine ( 1 ), 9-methyl-12H-benzo[a] phenothiazine ( 2 ), 10-methyl-12H-benzo[a] phenothiazine ( 3 ), 11-methyl-12H-benzo[a]phenothiazine ( 4 ), 5-oxo-5H-benzo[a]phenothiazine ( 5 ), 6-hydroxy-5-oxo-5H-benzo[a]phenothiazine ( 6 ) and 6-methyl-5-oxo-5H-benzo[a] phenothiazine ( 7 ):) were measured in several solvents of different polarities and hydrogen bonding abilities. In combination with the ground state dipole moments of these benzo[a]phenothiazines, the spectral data were used to determine their first excited singlet-state dipole moments by means of the solvatochromic shift method. These excited singlet-state dipole moments were found to be significantly higher (1.9 to 2.5 Debye units) than their ground-state counterparts.     

Design,synthesis and molecular docking of new [1,2,4] triazolo[4,3-a]quinoxaline derivatives as anticancer agents targeting VEGFR-2 kinase

Molecular Diversity - Vascular endothelial growth factor receptor-2 (VEGFR-2) is critically involved in cancer angiogenesis. Blocking of VEGFR-2 signaling pathway proved effective suppression of...