Spectral, luminescent, and lasing properties of 3-(benzothiazolyl-2)-7-hydroxy-and-8-hydroxycoumarins

The spectral and luminescent properties of 3-(benzothiazolyl-2)-7-hydroxy-and-8-hydroxycoumarins and their protolytic forms are studied experimentally and with the help of quantum-chemical calculations using the method of intermediate neglect of differential overlap with spectroscopic parameterization. The photophysical processes in these compounds are analyzed. The fluorescence of 3-(benzothiazolyl-2)-8-hydroxycoumarin is shown to be extremely weak due to intercombination conversion of the excitation energy. The introduction of a proton-accepting substituent next to the hydroxy group of the molecule (at position 8) leads to intramolecular proton transfer, resulting in formation of a zwitterion, with the probability of the proton transfer increasing in the excited S ₁ state. The lasing ability of the protolytic forms of the molecules under excitation with a XeCl excimer laser is studied. It is shown that the compounds have the highest lasing efficiency in the anionic form.     

4H-benzochromene derivatives as novel tyrosinase inhibitors and radical scavengers: synthesis,biological evaluation,and molecular docking analysis

Molecular Diversity - A series of ethyl 2-amino-4H-benzo[h]chromene-3-carboxylate derivatives, having phenyl ring with diverse substituents at C4 position of 4H-benzochromene nucleus, were...     

Mass Spectrometry Study of 7-Chloro-3,4-dihydro-4,5-dioxo-3-substituted Aryl-2-thio-2H, 5H-pyrano [3,4-e]-1,3-Oxazine,their Morpholine and Alcohol Reaction Products

Retro Diels-Alder mechanism is the main fragmentation pattern of the 7-chloro Pyrano oxazine (2),7-morpholino pyrano oxasine (3),5-morpholino carbonyl-4-oxo-3-substituted phenyl-2-thio-1-3-oxazine-6-ylacetomorpholide (4) and ethyl-6-ethoxy carbonyl methyl-4-oxo-3-(substituted phenyl)-2-thio-2H-1,3-oxazine-5-carboxylate (5). Further fragmentation routes were also discussed.     

Lasing properties of 3CN coumarins

In this report the effects of 3CN substitutions on the spectral luminescence and lasing properties of oxy- and diethylaminocoumarins are studied. In both classes of coumarins the CN group decreases the tuning region of the maximum lasing wavelengths: in aminocoumarine as a result of decreased intermolecular interaction with the solvents, and in the oxy- as a result of a shift in the equilibrium of protolytic reactions towards anion forms. As a result, the lasing efficiency of anion forms of 3CN oxycoumarins increases. The lasing properties of aminocoumarins decrease with the given substitutions, while the probability increases for the formation of nonplanar molecular conformations.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 103–106, June, 1988.     

Gas phase retro-Michael reaction resulting from dissociative protonation: fragmentation of protonated warfarin in mass spectrometry

A mass spectrometric study of protonated warfarin and its derivatives (compounds 1 to 5) has been performed. Losses of a substituted benzylideneacetone and a 4-hydroxycoumarin have been observed as a result of retro-Michael reaction. The added proton is initially localized between the two carbonyl oxygens through hydrogen bonding in the most thermodynamically favorable tautomer. Upon collisional activation, the added proton migrates to the C-3 of 4-hydroxycoumarin, which is called the dissociative protonation site, leading to the formation of the intermediate ion-neutral complex (INC). Within the INC, further proton transfer gives rise to a proton-bound complex. The cleavage of one hydrogen bond of the proton-bound complex produces the protonated 4-hydroxycoumarin, while the separation of the other hydrogen bond gives rise to the protonated benzylideneacetone. Theoretical calculations indicate that the 1, 5-proton transfer pathway is most thermodynamically favorable and support the existence of the INC. Both substituent effect and the kinetic method were utilized for explaining the relative abundances of protonated 4-hydroxycoumarin and protonated benzylideneacetone derivative. For monosubstituted warfarins, the electron-donating substituents favor the generation of protonated substituted benzylideneacetone, whereas the electron-withdrawing groups favor the formation of protonated 4-hydroxycoumarin. Copyright ? 2012 John Wiley & Sons, Ltd.     

A general three-step one-pot synthesis of novel (<Emphasis Type="Italic">E</Emphasis>)-6-chloro-2-(aryl/hetarylvinyl)quinoline-3-carboxylic acids

In this work, a facile and general three-step one-pot synthesis of structurally new (E)-6-chloro-2-(aryl/hetarylvinyl)quinoline-3-carboxylic acid derivatives has been achieved from easily available ethyl 6-chloro-2-(chloromethyl) quinoline-3-carboxylate and aromatic or heteroaromatic aldehydes. This strategy features simple one-pot operation, tolerance of a wide range of substituents, and good yields. Moreover, these newly synthesized compounds belong to a new class of quinoline derivatives and could be good candidates for the development of more complex quinoline compounds for use in medicinal chemistry.     

Electro-optic and viscoelastic properties of a ferroelectric liquid crystalline binary mixture

ABSTRACT

This study describes the properties of a binary liquid crystalline mixture composed of commercially available materials, Ce-3 (4-(n-hexyloxy phenyl)-1-(2-fuethyl butyl) biphenyl-4-carboxylate) and Ce-8 (4-(2-methylbutyl) phenyl-4-n-octylbiphenyl-4-carboxylate), in a weight ratio of 50:50. Both compounds show polymesomorphism and ferroelectric properties within a relatively wide temperature range. Taken separately, each compound has its advantages and disadvantages from the technical point of view. The influence of temperature on the electro-optical and viscoelastic properties of the produced binary mixture is investigated in this paper.     

Synthesis of polyfunctionalized acrylates via one-pot reactions of arylamines, methyl propiolate, aromatic aldehydes, and active methylene compounds

An efficient synthetic method for the densely substituted 3-arylaminoacrylates was successfully developed via the one-pot reaction of arylamines, methyl propiolate, aromatic aldehydes, and active methylene compounds such as pivaloylacetonitrile, 1,3-cyclopentanedione, and 4-hydroxycoumarin. The key step of the reaction was believed to involve the formation of a β-enamino ester and a sequential Michael addition to the in situ formed arylidene dicarbonyl compound.     

Synthesis, Photo- and Electro-Luminescence of 3-Benzoxazol-2-yl-Coumarin Derivatives

Two coumarin derivatives containing electron-transporting benzoxazolyl moiety, 7-(diethylamino)-3-(benzoxazol-2-yl)coumarin (DABOC) and 3-(benzoxazol-2-yl)benzo[5,6]coumarin (BOBC), were synthesized and characterized. The photoluminescence and electroluminescence of the compounds were investigated detailedly. The compounds exhibited strong blue-green emissions in both solution and solid states, but the devices with DABOC as the emitting layer exhibited orange emission and maximum luminous efficiency of 2.8 cd/A and maximum luminance of 8,800 cd/m², and the devices with BOBC displayed orange-white emission and maximum luminous efficiency of 0.13 cd/A and maximum luminance of 540 cd/m².     

Peculiarity of methoxy group-substituted phenylhydrazones in Fischer indole synthesis

We found that the Fischer indole synthesis of ethyl pyruvate 2-methoxyphenylhydrazone (5) with HCl/EtOH gave an abnormal product, ethyl 6-chloroindole-2-carboxylate (7), as the main product, with a smaller amount of ethyl 7-methoxyindole-2-carboxylate (6) as the normal product. This abnormal reaction was the result of a cyclization on the side with the substituent (methoxy group) of a benzene ring on phenylhydrazone, which was not previously observed. In this initial investigation, we focused on 1) the application of the above-mentioned abnormal Fischer indole synthesis, 2) the details of this reaction of phenylhydrazone with other kinds of substituents, 3) the mechanism of the first step of the Fischer indole synthesis, 4) the abnormal reaction in methoxydiphenylhydrazones, and 5) a synthetic device to avoid an abnormal reaction. The results of these studies are summarized herein.     

An unexpected tetracyclic product isolated during the synthesis of biscoumarins catalyzed by [MIM(CH2)4SO3H][HSO4]: Characterization and X-ray crystal structure of 7-(2-hydroxy-4-oxo-4H-chromen-3-yl)-6H,7H-chromeno[4,3-b]chromen-6-one

Under solvent-free conditions and in the presence of 3-methyl-1-(4-sulfonic acid)butylimidazolium hydrogen sulfate [MIM(CH₂)₄SO₃H][HSO₄], a Brønsted acidic ionic liquid, the reaction of aromatic aldehydes with 4-hydroxycoumarin has been investigated. A wide range of aromatic aldehydes easily undergoes condensation with 4-hydroxycoumarin to afford biscoumarins with good purity in excellent yields. However, reaction of 2-hydroxybenzaldehyde with 4-hydroxycoumarin gave, not the corresponding biscoumarin, but a tetracyclic compound, 7-(2-hydroxy-4-oxo-4H-chromen-3-yl)-6H,7H-chromeno[4,3-b]chromen-6-one, in high yield.     

Synthesis and Fluorescence Investigation of Differently Substituted Benzo[b][1,8]Naphthyridines: Interaction with Different Solvents and Bovine Serum Albumin (BSA)

A series of benzo[b][1, 8]naphthyridines has been synthesized by Friedl?nder condensation of 2-aminoquinoline-3-carbaldehyde 1 (o-aminoaldehyde) with active methylenes in basic medium. The fluorescence spectroscopic properties of some representative compounds has been studied in different organic solvents; moreover interaction with bovine serum albumin (BSA) in phosphate buffer was examined by UV-vis and fluorescence spectroscopy. The effect of electron donor-acceptor substituents on fluorescence properties of benzo[b][1, 8]naphthyridines 13(a-n) has been investigated along with their fluorescent quantum yields.     

二烷氧基取代酞菁的合成及其吸收光谱的研究

以1,3,3-三氯异二氢氮杂茚和3-(2’,2’,4’-三甲基-3’-戊氧基)-1,3-二亚胺基异吲哚啉为原料,合成了二烷氧基取代无金属酞菁,产物经IR,UV-Vis,1H NMR及MS表征。在与相应的四烷氧基取代无金属酞菁相比较的基础上,探讨了产物的UV-Vis光谱中的Q带波长及其分裂程度与取代基的数目以及溶剂极性的关系。     

Synthesis and Characterization of Molecules Containing Thiazole and Oxazole Moieties and Study of ESIPT Phenomenon

Two novel ESIPT molecules, 2-[4-(1,3-benzothiazol-2-yl)naphtho[1,2-d][1,3]oxazol-2-yl]phenol 9a and 4-[4-(1,3-benzothiazol-2-yl)naphtho[1,2-d][1,3]oxazol-2-yl]benzene-1,3-diol 9b were synthesized by condensing 1-amino-3-(1,3-benzothiazol-2-yl)naphthalen-2-ol with 2-hydroxybenzoic acid and 2,4-dihydroxybenzoic acid respectively. The novel compounds were characterized by FT-IR, (1)H NMR, Mass spectral and elemental analysis. Effect of polarity on photo physical properties, absorption and emission were studied. Compounds showed single absorption and dual emission due to ESIPT phenomenon. The structural changes due to ESIPT phenomenon in terms of bond angle, bond distances and geometry were investigated by using Gaussian 03 software. These two novel ESIPT molecules are thermally stable up to 200?°C.     

DNA Binding,Cleavage and Antibacterial Activity of Mononuclear Cu(II), Ni(II) and Co(II) Complexes Derived from Novel Benzothiazole Schiff Bases

A series of novel bivalent metal complexes M(L₁)₂ and M(L₂)₂ where M = Cu(II), Ni(II), Co(II) and L₁ = 2-((benzo [d] thiazol-6-ylimino)methyl)-4-bromophenol [BTEMBP], L₂ = 1-((benzo [d] thiazol-6-ylimino)methyl) naphthalen-2-ol [BTEMNAPP] were synthesized. All the compounds have been characterized by elemental analysis, SEM, Mass, ¹H NMR, ¹³C NMR, UV–Vis, IR, ESR, spectral data and magnetic susceptibility measurements. Based on the analytical and spectral data four-coordinated square planar geometry is assigned to all the complexes. DNA binding properties of these complexes have been investigated by electronic absorption spectroscopy, fluorescence and viscosity measurements. It is observed that these binary complexes strongly bind to calf thymus DNA by an intercalation mode. DNA cleavage efficacy of these complexes was tested in presence of H₂O₂ and UV light by gel electrophoresis and found that all the complexes showed better nuclease activity. Finally the compounds were screened for antibacterial activity against few pathogens and found that the complexes have potent biocidal activity than their free ligands.     

Fine-structure energy levels,oscillator strengths and lifetimes in Mg-like chromium

Excitation energies from ground state for 86 fine-structure levels as well as oscillator strengths and radiative decay rates for all fine-structure transitions among the levels of the terms (1s²2s²2p⁶)3s²(¹S), 3s3p(^1,3P^o), 3s3d(^1,3D), 3s4s(^1,3S), 3s4p(^1,3P^o), 3s4d(^1,3D), 3s4f(^1,3F^o), 3p²(¹S, ³P, ¹D), 3p3d(^1,3P^o, ^1,3D^o, ^1,3F^o), 3p4s(^1,3P^o), 3p4p(^1,3S, ^1,3P, ^1,3D), 3p4d(^1,3P^o, ^1,3D^o, ^1,3F^o), 3p4f(^1,3D, ^1,3F, ^1,3G) and 3d²(¹S, ³P, ¹D, ³F,¹G) of Cr XIII are calculated using extensive configuration-interaction (CI) wave functions obtained with the CIV3 computer code of Hibbert. The important relativistic effects in intermediate coupling are included through the Breit-Pauli approximation via spin-orbit, spin-other-orbit, spin-spin, Darwin and mass correction terms. Small adjustments to the diagonal elements of the Hamiltonian matrices have been made. The mixing among several fine-structure levels is found to be very strong. Our excitation energies, including their ordering, are in excellent agreement (better than 0.5%) with the available experimental results. From our transition probabilities, we have also calculated radiative lifetimes of some fine-structure levels. Our calculated lifetime for the longer-lived level 3s3p(³P₁) is found to be in excellent agreement with the experimental result of Curtis compared to other theoretical calculations.     

几种咪唑-二氧杂环的含能取代衍生物的理论研究

使用DFT的B3LYP方法对几种咪唑二氧杂环化合物的分子结构、红外光谱、生成焓、爆轰性能和化学/热稳定性进行了研究.四种不同含能基团-NO₂,-NH₂,-N₃和-ONO₂对该化合物各项性能的影响进行了比较.结果表明-NO₂和-ONO₂基团有效地增加了化合物的密度,而-N³基团极大地增加了化合物的生成焓.其中-NO₂取代物爆轰性能接近1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane,-ONO₂取代物的爆轰性能低于hexahydro-1,3,5-trinitro-1,3,5-triazine.自然键轨道分析表明,这些化合物中相对较弱的键为取代基和咪唑环之间的键,以及二氧杂环中的C-O键.吸电子基团(-NO₂, -N³和-ONO₂)在分子中产生了明显的诱导效应,减弱了基团与咪唑环之间的链接,降低了对应键的键裂解能.研究表明基团的电负性与化合物的稳定性有关.考虑到化合物的爆轰性能和热稳定性,DNTNDI化合物满足高能量密度材料的要求.     

基于α-肉桂酰环乙烯酮二硫缩酮的一类新型D-A有机发光材料的理论

用密度泛函理论B3LYP方法对四种新型D-π-A分子(PKD,NKD,TKD和CKD)进行基态几何构型全优化,计算分子的电离势IP和电子亲和势EA等相关能量。用含时密度泛函(TDDFT)方法计算吸收光谱,用单组态相互作用方法(CIS)优化四种化合物分子的S₁激发态结构,分析其能量与发射光谱的关系。根据化合物组成的不同恰当地选择泛函计算分子的发射光谱,并与实验结果对照表明,计算结果比较可靠。     

Photochromism of dihydroindolizines part VII: multiaddressable photophysical properties of new photochromic dihydroindolizines bearing substituted benzo[i]phenanthridine as a fluorescing moiety

Sixteen benzo[i]phenanthridine derivatives 8a‐p were prepared via photocyclization of cis‐trans substituted 4‐styrylquinolines in low‐to‐moderate yields. The chemical structure of the photocyclized benzo[i]phenanthridine derivatives was unambiguously elucidated by means of both spectral and analytical tools. The photochromic (PC) dihydroindolizines (DHIs) 8a‐p based on benzo[i]phenanthridines were prepared in 19–57% yields via nucleophilic addition of benzo[i]phenanthridines 4a‐p to spirocyclopropenes 5 . The 1D, 2D, NOESY NMR spectra, mass spectrometry, and elemental analysis were used for characterization of the chemical structures of the newly synthesized DHIs 8a‐p . Developing and tuning of the photophysical properties of the synthesized compounds by substituents in the base part have been achieved. The absorption maxima (λ_max) and the half‐lives (t_1/2) of the colored zwitterionic forms 7a‐p were detected in all cases by flash‐photolysis measurements due to the fast 1,5‐electrocyclization back to the DHI system. Irradiation of DHI 8a‐p in'CH₂Cl₂ solution with polychromatic light leads to the formation of green to green–blue colored betaines 7a‐p after cooling with liquid nitrogen. The kinetics of the fast bleaching process of betaines 7a‐p to DHIs 8a‐p , studied by flash photolysis as well as low temperature FT‐UV/VIS, were found to take place in the millisecond range (432–2675 ms) in dichloromethane solution and fitted well a first‐order thermal back reaction. The fluorescence spectra as well as the fluorescence quantum yield were studied. Noticeable bathochromic and hypsochromic shifts in the emission spectra by changing the substituents in the base part were monitored. Interestingly, the photo‐fatigue resistance of some studied betaines 7a‐p showed a higher t₃₀‐value than the standard one (dicyanopyridazine DHI). Large solvatochromic effects on the absorption maxima (λ_max) as well as a substantial increase in the half‐lives (t_1/2) with solvent polarity of betaines 7a‐p were also observed. The multiaddressable PC properties of DHIs 8a‐p will help these compounds to find applications. Copyright © 2007 John Wiley & Sons, Ltd.     

The effect of 4-hydroxycoumarin and umbelliferone on DPPC bilayers. Ultrasound study

The organisation of two coumarins, 4-hydroxycoumarin and 7-hydroxy- coumarin (umbelliferone) in dipalmitolyphosphatidylcholine (DPPC) was examined in the study. Ultrasound absorption technique was applied to study the effect of the presence in DPPC membranes of one of the coumarines on the parameters of phase transition. 4-hydroxycoumarin was found to change both phase transition temperature of this transition, and cooperativity more than umbelliferone. Different influence of these examined compounds is associated with their different location in the DPPC membrane, what results from different distribution of amphyphilness in molecules of both compounds.