Halogen-substituent effect on the spectroscopic properties of 2-phenyl-6-dimethylaminobenzothiazoles

6-Dimethylamino-2-phenylbenzothiazole (1-H) is a push-pull benzothiazole fluorophore mimicking the firefly oxyluciferin structure. We newly prepared 7-chloro and 7-bromo derivatives of 1-H and its 4-acetyl derivative (2-H), and their spectroscopic and photophysical properties were investigated. The halogenated derivatives showed the blue-shifted electronic absorption maxima and fluorescence emission maxima compared to 1-H and 2-H, resulted from the deformations of the NMe₂ groups and the electron withdrawing properties of the halogen groups. In addition, the halogen substitutions accelerate intersystem crossing by heavy atom effect, resulting in a decrease in fluorescence quantum yields. Interestingly, however, the halogenated derivatives of 2-H still showed moderate fluorescence quantum yields. The halogenation effect is one of the guides to design push-pull benzothiazole fluorophores for tuning fluorescence properties.     

Study on the effects of intermolecular interactions on firefly multicolor bioluminescence

Firefly luciferase exhibits a color-tuning mechanism based on pH-induced changes in the structure of the active site. These changes increase the polarity of the active site, and thus modulate the intermolecular interactions between the light emitter and active site molecules. In this study, the effects exerted by adenosine monophosphate (AMP), water molecules, and amino acids of Luciola cruciata luciferase active site on the emission wavelength of oxyluciferin were assessed by TD-DFT calculations. The redshift results mainly from decreased interaction of oxyluciferin with AMP and increased interaction of the emitter with a water molecule and Phe249. Breaking of a hydrogen bond between the benzothiazole oxygen atom with formation of a similar bond to the thiazolone oxygen atom is also instrumental.     

Theoretical modulation of the color of light emitted by firefly oxyluciferin

One of the major mysteries regarding firefly bioluminescence is its pH-dependent multicolor variation. At basic pH, the emission is on the yellow-green region, whereas at acid pH, the light emission is observed on the red region of the visible spectrum. Theoretical calculations using density functional theory, molecular mechanics, and semiempirical methods were made to investigate the effect exerted by intermolecular forces on light emission, and their modulation by polarity, and the differences in the conformation of the active site at basic and acid pH. Red emission is achieved by the weakening of the interactions of the emitter with ionic and hydrophobic molecules, by the polarization of the benzothiazole microenvironment, by ionization of the enzyme-emitter complex and by changes of the hydrogen bond network. Arg220, Glu346, Ala350, Leu344 and adenosine-5'-monophosphate have blue-shifting effects, while His247, Phe249, Gly341, Thr253, and Ile288 exert a redshifting one.     

Structure, configuration, conformation and quantification of the push-pull effect of 2-alkylidene-4-thiazolidinones and 2-alkylidene-4,5-fused bicyclic thiazolidine derivatives

Structures of a series of push-pull 2-alkylidene-4-thiazolidinones and 2-alkylidene-4,5-fused bicyclic thiazolidine derivatives were optimized at the B3LYP/6-31G(d) level of theory in the gas phase and discussed with respect to configurational and conformational stability. Employing the GIAO method, ¹³C NMR chemical shifts of the C-2, C-2′, C-4 and C-5 atoms were calculated at the same level of theory in the gas phase and with inclusion of solvent, and compared with experimental data. Push-pull effect of all compounds was quantified by means of the quotient π^∗/π, length of the partial double bond, ¹³C NMR chemical shift difference (Δδ_CC) and ¹H NMR chemical shifts of olefinic protons. The effect of bromine on donating and accepting ability of other substituents of the push-pull CC double bond is discussed, too.     

Development of a push-pull microdialysis sampling technique for the quantitative determination of proteins

Summary An on-line push-pull sampling technique has been developed for continuous analysis of proteins of molecular weight from 5.7 to 67 kDa. The characteristics of the system include gradient elution with a total cycle time of 21 min, membrane stability, unattended automatic operation, and adjustment of the sampling mode and extraction fraction (the ratio of the concentration of analyte in the dialysate to that in the sample) by varying the effective dialysis length. The push and pull flow rates were adjusted in a manner which enabled three different modes of operation. When push-pull microdialysis was compared with conventional microdialysis sampling, significantly higher extraction fractions were obtained for all five model proteins studied. The technique has been applied to the quantification of proteins in cell samples. On-line fractionation enabled complementary MS identification of the proteins present.     

Organometallic modification approach to the control of push-pull architectures: Synthesis, properties and radical polymerization of chromium N-vinylcarbazole derivatives

In an effort to combine the donor character of the carbazole unit with the electron-withdrawing nature of the chromiumtricarbonyl moiety, which can be further modified by exchange of the CO ligand, a new series of vinyl-type monomers with organometallic push-pull chromophores, (N-vinylcarbazole)Cr(CO)₂L (L = CO (2), PPh₃ (4), (5)) and (N-vinylcarbazole)bisCr(CO)₃ (3), have been synthesized and isolated, wherein 2 could be converted into 3 under appropriate conditions. All compounds were characterized spectroscopically, and X-ray crystal structure analyses were performed for 2-4. The coordination-induced geometrical changes occur predominantly on the N-center and its attached double bond. PPh₃ replaces a CO group leading to the N-vinyl double bond length shortening from 1.274 (12) to 1.245 (9) Å. The distance of Cr from the carbazole plane, which allows estimates of the strength of the metal-ligand π-bonding, is shorter in 3 than in 2 as a result of an electronic communication between the two Cr(CO)₃ groups on each aryl ring of carbazole molecule. Electronic absorption and fluorescence spectral features of these complexes have been studied in terms of the electronic nature of the ligands. The change from 2 to 3 causes a subtle red-shift of the absorption bands due to the electronic transitions within dinuclear-carbazole ring system. The polymerization studies of these complexes under free-radical conditions lead to a better understanding of how the organometallic moiety affects the vinyl polymerization. The intriguing effect of the organometallic moiety on the intrachain excimer formation in the resultant polymers have been shown to be likely.     

Theoretical studies on NLO properties of push-pull multi-cycle electro-optical polymer intermediates including thiophene ring

The second-order nonlinear optical susceptibilities βijk,βμ and third-order non-linear optical susceptibilities γijkl,<γ> of a series of the novel push-pull multi-ring electro-photo polymer intermediates have been calculated.The influences of molecular structure,donor,acceptor and the frequency of external field on P and v,and the relationship between V and the number of thiophene rings(i.e.conjugated chain length)have been studied using UNDO/SCI methods combined with sum-overstate(SOS)formula.The calculated results show that γ is proportional to 2.69 power of the chain length of the conjugated molecular bonds when the length is not quite long.     

Carbon-bromine cleavage by dimethyl sulfoxide: the key step of C(5) functionalization of push-pull 2-alkylidene-4-oxothiazolidine vinyl bromides

Push-pull 2-alkylidene-4-oxothiazolidine vinyl bromides undergo efficient C(5) functionalization through DMSO-assisted carbon-bromine cleavage, followed by a bromine transfer-substitution (or elimination) sequence. A mechanism for this novel transformation is proposed.     

Regioselective phenyl-substitution effects on the solvatochromism of 2-phenylimidazo[1,2-a]pyrazin-3(7H)-one derivatives: expansion of the color variation range of a visible indicator for the proton donor ability of solvents

Phenyl-substitution to the C8 position of an imidazopyrazinone ring resulted in the significant bathochromic shift of the lowest energy band, while the substitution to the C6 position does not produce such a shift. This provides evidence that a color variation range of the solvatochromism of 2-phenylimidazopyrazinone derivatives depends strongly on the position of phenyl-substitution. Results indicated that an imidazopyrazinone with the phenyl groups at the C2 and C8 positions acts as a potential indicator of the proton donor ability of solvents.     

ZnO-beta zeolite:As an effective and eco-friendly heterogeneous catalyst for the synthesis of benzothiazole derivatives

<正>A cheap and recyclable ZnO-beta zeolite was used as catalyst for the synthesis of benzothiazole derivatives.This method provides several advantages such as environmental friendliness,short reaction times,high yields,simple work-up procedure and catalyst was successfully reused for four cycles without significant loss of activity.     

新型苯并噻唑类探针的合成及其对S2-的荧光和比色检测

本文设计合成了一种基于激发态分子内质子转移(ESIPT)机理的苯并噻唑类荧光探针TZ-1,并对其结构进行了表征。实验结果表明,在体积比1∶1的DMSO/PBS(10mmol/L,pH=7.4)溶液中,探针TZ-1具有高选择性并可在3s内实现荧光"off-on"(在365nm紫外灯照射下,由无荧光变成橙色荧光)识别S~(2-),检测限为81μmol/L,pH适用范围为6～12;此外,加入S~(2-)后探针TZ-1的DMSO/PBS溶液由无色变为浅黄色,通过裸眼即可识别S~(2-)。     

Studies on the solvatochromism of Fe(CN)2(phen)2

Summary The influence of organic solvents on the electronic spectra of Fe(CN)₂(phen)₂ has been investigated by trichromatic colorimetry. The color parameters of these solutions have been calculated on the basis of the absorption spectra and are described in the CIE and CIELAB color spaces. It has been shown that one of the parameters (the so-called hue angle) could be related to some acidity parameters of solvents. Thus, it is possible to calculate the hue angle and, therefore, to predict the color of solution if the solvent acceptor number is known, or vice versa.

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Untersuchung zur Solvatochromie von Fe(CN)₂(phen)₂

Zusammenfassung Der Einfluß organischer Lösungsmittel auf die UV-Spektren von Fe(CN)₂-(phen)₂ wurde mittels trichromatischer Kolorimetrie untersucht. Die Farbparameter der Lösungen wurden aus den Absorptionsspektren berechnet und werden in den CIE- und CIELAB-Farbräumen beschrieben. Es konnte gezeigt werden, daß einer der Farbparameter (der sogenannte Farbtonwinkel) zu den Aciditätsparametern des jeweiligen Lösungsmittels in Beziehung gesetzt werden kann. Es ist daher z.B. möglich, die Farbe der Lösung vorherzusagen, wenn die Akzeptorzahl des Lösungsmittels bekannt ist und umgekehrt.

     

2-(甲苯-4-磺酰胺基)-苯甲酸的晶体结构、光谱及热性质

报道了2-(甲苯-4-磺酰胺基)-苯甲酸(I)的元素分析和红外、核磁共振光谱性质并通过单晶X射线衍射确定了其晶体结构. 晶体属单斜晶系, 空间群为C2/c,晶胞参数为, a=2.7320(3) nm, b=0.85441(8) nm, c=1.17607(11) nm, α=90°, β=98.728(3)°, γ=90°, V=2.7135(5) nm3, Z=8. 晶体中分子单体通过N—H…O 和O—H…O氢键作用形成具有中心对称的二聚体, 且进一步通过两种不同的C—H…O 氢键和π…π作用形成超分子结构. 在不同的溶剂中, 化合物I的紫外吸收表现出明显的溶剂效应, 此外, 荧光光谱与DSC-TGA热重分析表明, 该化合物是一种耐热的荧光材料.     

Synthesis and characterization of novel push-pull oligomer based on naphthodithiophene-benzothiodiazole for OFETs application

A novel push-pull oligomeric semiconductor, ENBT based on naphthodithiophene-benzothiodiazole was successfully designed and synthesized. ENBT was fully characterized by ¹H NMR, MS, thermogravimetric analysis (TGA), UV–vis spectra, and cyclic voltammetry (CV). Furthermore, ENBT-based OFETs were fabricated by solution-processed dip-coating technique and its charge transporting property was investigated. The film of ENBT exhibited a hole mobility as high as 1.4?×?10^?2?cm²/(Vs) with a current on/off ratio of 10⁶–10⁷ after annealed at 160?°C. In order to give an insight to the transporting property of ENBT films, thin film morphologies after annealing at different temperatures were also studied by atomic force microscopy (AFM).     

Substituent effects on the spectroscopic properties of solvatochromic 2-phenylimidazo[1,2-a]pyrazin-3(7H)-ones: an effective control for the colorimetric sensor properties

Substituent effects on the spectroscopic properties of a solvatochromic compound, 7-methyl-2-phenylimidazo[1,2-a]pyrazin-3(7H)-one (1c), using derivatives 1 with a para-substituent R on the phenyl group, were investigated systematically. In the UV/visible absorption spectra, the solvatochromic property of 1 originating from hydrogen-bonding interactions was effectively regulated by the substituent effects. In particular, the cyano derivative 1e showed significant solvatochromism with a wide color variation range and a high sensitivity toward solvents. Similarly, the fluorescence of 1 showed a redshift as the electron-withdrawing property of R increased. The substituent effects were evaluated by AM1-COSMO calculations, which also suggested that derivatives 1 are good electron donors and that the electron-donating ability is regulated by R. This was confirmed by the observation of low oxidation potentials and the formation of charge-transfer complexes with tetracyanoethylene. Absorption-spectrum changes of 1c and 1e caused by metal-ion complexation were also compared, showing that the cyano derivative 1e is a good colorimetric sensor for the Lewis acidity of the metal ions. From these observations, it was established that para-substitution of R on the phenyl group of 1c caused successive modulations of the colorimetric sensor properties.     

Synthesis and crystal structure of dinuclear tetraphenylantimony carboxylate derivatives based on different coordination modes

Two novel dinuclear tetraorganoantimony carboxylate derivatives were synthesized based on two different coordination modes, in which the environment of one of the two Sb atoms is described as trigonal bipyramid and the other is ascribed to distorted octahedron carrying four phenyl and one benzoate substituent. Structures of compound 1 and 2 were determined by single-crystal X-ray analysis, IR and NMR. Of the two compounds, a novel double-chain structure was shown in compound 1 through C-H?π weak interaction, while compound 2 exhibited a 1D chain by C-H?π weak interaction identically.     

Theoretical design of blue emitting materials based on symmetric and asymmetric spirosilabifluorene derivatives

Equilibrium ground state geometry configurations and their relevant electronic properties of four experimentally reported asymmetric spirosilabifluorene derivatives are calculated by the HF(DFT)/6-31G(d) method. Their excited state geometries are investigated using the CIS/6-31G(d) method. The absorption and emission spectra are evaluated using the TD-B3LYP/6-31G(d) and TD-PBE0/6-31+G(d) levels both in gas phase and CHCl₃ solvent. Our results show an excellent agreement with the experimental data on their optical properties. To predict the substitution effect, the H/R (R = –NO₂, –CN, –NH₂ and –OCH₃) substituted symmetric and asymmetric spirosilabifluorene derivatives are also investigated, and the optical properties of H/R substituted derivatives are predicted in gas phase and CHCl₃ solvent. In comparison with the parent compound, significant red-shift is predicted for the emission spectra of the di-substituted symmetric derivatives with –NH₂ (96 nm), –OCH₃ (61 nm) and the push–pull (containing both –NH₂ and –NO₂) derivative (56 nm). It is found that the performance and the optical properties of these derivatives can be improved by adding push–pull substitutents. The largest change in the electronic and optical properties of this system can be obtained upon symmetric di-substitution among mono-, di-, tri- and tetra-substitutions. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Syntheses and characterization of mixed-chelate copper(II) complexes containing different counter ions; spectroscopic studies on solvatochromic properties

Solvatochromic mixed-chelate copper(II) complexes, [Cu(Cl-acac)(diamine)]X (where Cl-acac = 3-chloroacetylacetonate ion, diamine = N,N′-dimethyl,N′-benzyl-1,2-diaminoethane and X = B(Ph)₄⁻, PF₆⁻, BF₄⁻ and ClO₄⁻), have been prepared. The complexes were characterized on the basis of elemental analysis, molar conductance, UV-Vis and IR spectroscopies. Single crystals of [Cu(Cl-acac)(diamine)(H₂O)]PF₆, complex 2, were also characterized by X-ray diffraction. The influence of the solvent polarity and counter ions on the ν_max values of the d-d bands of the complexes have been investigated by means of visible spectroscopy. All the complexes demonstrated negative solvatochromism. A multi-parametric equation has been utilized to explain the solvent effect on the d-d transition of the complexes using SPSS/PC software. The stepwise multiple linear regression (SMLR) method demonstrated that the donor power of the solvent plays the most important role in the solvatochromism of the compounds. The relative donor power of the anions X was determined by visible spectra in the solvent dichloromethane.     

Synthesis of benzothiazoles from 2-aminobenzenethiols in the presence of a reusable polythiazolium precatalyst under atmospheric pressure of carbon dioxide

Synthesis of benzothiazoles from 2-aminobenzenethiols and carbon dioxide was carried out using poly(3,4-dimethyl-5-vinylthiazolium) iodide as a precatalyst to in situ generation of NHCs by deprotonation. The reaction was successfully carried out under mild conditions (1 atm of CO₂ and 60–70 °C) with a broad substrate scope and functional group tolerance. The precatalyst salt was recovered and reused for several times without any loss of activity.     

A fluorescence turn-on method for real-time monitoring of protease activity based on the electron transfer between a fluorophore labeled oligonucleotide and cytochrome c

A new continuous fluorescence turn-on assay for protease activity and inhibitor screening has been developed. A fluorophore labeled single stranded DNA (FAM-DNA) and cytochrome c (cyt c) were employed. The fluorescence of the FAM-DNA was efficiently quenched when binding to cyt c, through the electron transfer between the FAM fluorophore and the heme cofactor of cyt c. In the presence of a protease, such as trypsin, cyt c was digested into small peptide fragments. The FAM-DNA was released, which resulted in the recovery of the FAM fluorescence. The rate of the cyt c digestion could be reduced via the addition of an inhibitor. As a result, reduced degree of the fluorescence recovery was obtained. The limit of detection of our assay is 1 nM trypsin and the IC₅₀ values are 3.23 μg mL⁻¹ and 0.303 μg mL⁻¹ for the inhibitor from egg white and the inhibitor from soybean, respectively. Our method could be used for the sensing of protease activity for various biochemical applications, and for the screening of protease inhibitors as drugs for the treatment of various related diseases.