Formal hydride transfer mechanism for photoreduction of 3-phenylquinoxalin-2-ones by amines. Association Of 3-phenylquinoxalin-2-one with aliphatic amines

The photophysical and photochemical behavior of 1-methyl-3-phenylquinoxalin-2-one (MeNQ) and 3-phenylquinoxalin-2-one (HNQ) in the presence of amines is reported. While HNQ fluorescence shows an auxochromic effect and a bathochromic shift with added amines, explained by association of HNQ with amine in the ground state and emission from both excited species HNQ and [HNQ-amine], both MeNQ and HNQ are photoreduced efficiently on irradiation in the presence of amines, leading to the semireduced quinoxalin-2-ones, MeNQH(-) and HNQH(-), respectively, via an electron-proton-electron transfer, with unit quantum yields at high amine concentrations. The semireduced quinoxalin-2-ones XNQH(-) (X = H, Me) revert almost quantitatively to the parent XNQ in a dark thermal reaction with an activation free energy for MeNQH(-) of 17.4 and 25.9 kcal/mol in acetonitrile and benzene, respectively. Kinetic and spectroscopic (UV and NMR) evidence supports the proposed reaction mechanism for the reversible photoreduction.     

钴卟啉对三种胺的固定用于SO2的脱除

利用紫外-可见光谱和荧光光谱手段研究了四苯基卟啉钴（CoTPP）对苯胺、乙二胺和二乙胺的超分子固定用于脱除SO2. 紫外-可见光谱表明CoTPP与三种胺作用后生成CoTPP-胺配合物,Soret吸收带发生红移. 当通入SO2后,SO2与胺的作用强于CoTPP与胺的作用,CoTPP-胺配合物释放出CoTPP,CoTPP 在胺法脱硫过程中起到胺固定作用. 荧光光谱表明CoTPP与三种胺作用形成1：1的分子配合物,且为熵驱动反应. CoTPP与苯胺和二乙胺作用为吸热反应,CoTPP与乙二胺作用为放热反应.     

The influence of tetrahydroquinoline rings in dicyanomethylenedihydrofuran (DCDHF) single-molecule fluorophores

We have synthesized several series of DCDHF fluorophores with the amine donor either acyclic or constrained in one or two tetrahydroquinoline rings. The absorption and the fluorescence emission wavelengths and quantum yields have been determined and correlated with the specific donor structures. Generally, inclusion of the donor in a ring annulated to the benzene or naphthalene aromatic (Ar) π-core results in a bathochromic shift of absorption and emission accompanied by an increase in the quantum yield. Thus, the tetrahydroquinoline donor provides an efficient way to tailor the properties of fluorophores with substituted amines as electron-donating groups.     

芳香胺与电子受体相互作用的吸收光谱研究

芳香胺与电子受体相互作用形成的电荷转移复合物(CTC)的吸收峰位置与两者的结构有关。弱的电子受体使芳胺紫外吸收峰加宽,而强的电子受体如四氰基乙烯(TCNE)与芳胺作用产生的CTC显示新峰。受体的受电子能力越强,新峰红移越多。芳胺苯环上氨基对位的取代基给电子能力越强,氮原子上烷基取代基越多,其与受体形成的CTC的吸收峰红移也越多。     

A versatile standard for bathochromic fluorescence based on intramolecular FRET

A perylene and a terrylene tetracarboxylic bisimide dyad was prepared in which an efficient energy transfer from the former to the latter is observed. The absorption spectrum of this compound covers a broad range. Bathochromic fluorescence with a high quantum yield was obtained independent of excitation wavelengths (λ < 655 nm). The dyad can be recommended for the use of calibrating fluorescence spectrometers, as well as a fluorescence standard in the bathochromic region.     

A new weakly basic amino‐reactive fluorescent label for use in isoelectric focusing and chip electrophoresis

In this study, we present a novel amino‐reactive fluorescence marker (referred to as UR‐431), which is well suited for electrophoretic techniques. A main feature of this marker is its weakly basic behavior when conjugated to analytes. Labeled primary amines exhibit a positive net charge and accordingly a cathodic mobility below a pH of 2.4. The label features a pH‐independent fluorescence emission and is thus very interesting for electrophoretic applications such as IEF. The absorption maximum of this yellow daylight chromophore is at 431 nm, whereas fluorescence emission peaks at 537 nm (quantum yield≈0.1). The label was successfully conjugated to amines, peptides and proteins and separated via CE and MCE. The on‐chip detection limit of labeled lysine using a mercury‐lamp‐based fluorescence microscope was determined as 12 nM. An important feature of the new label is that it effects only a subtle change of the pI of proteins compared with common anionic labels, e.g. FITC. pI values of proteins were investigated by comparing native proteins and labeled proteins in CIEF. UR‐431 was also applied to sensitive detection of amines and peptides in MCE.     

Phenol-containing bis(oxazolines): synthesis and fluorescence sensing of amines

The fluorescence sensing of primary amines as their neutral forms has been studied with bis(oxazolinyl)phenols (Me-BOP, Ph-BOP), which are efficiently synthesized starting from mesitylene in six steps and in overall 12-22% yields. The BOP sensors showed fluorescence enhancement toward butylamine and several arylethylamines, whereas they showed fluorescence quenching toward secondary and branched amines. The opposite fluorescence behavior is explained by an increased conformational restriction at the excited state, at which a proton transfer complex between the host and guest forms that is stabilized in a tripodal hydrogen bonding mode. This is the first example in which fluorescence enhancement is observed in amine sensing with phenolic fluorophores. Enantiomeric α-chiral organoamines were also sensed with different fluorescent intensity changes by Ph-BOP, complementing the previous tris(oxazolines) that sense enantiomeric α-chiral organoammonium ions.     

Ultrafluorogenic Monochromophore-Type BODIPY-Tetrazine Series for Dual-Color Bioorthogonal Imaging with a Single Probe

Various fluorogenic probes utilizing tetrazine (Tz) as a fluorescence quencher and bioorthogonal reaction partner have been extensively studied over the past few decades. Herein, we synthesized a series of boron-dipyrromethene (BODIPY)-Tz probes using monochromophoric design strategy for bioorthogonal cellular imaging. The BODIPY-Tz probes exhibited excellent bicyclo[6.1.0]nonyne (BCN)-selective fluorogenicity with three- to four-digit-fold enhancements in fluorescence over a wide range of emission wavelengths, including the far-red region. Furthermore, we demonstrated the applicability of BODIPY-Tz probes in bioorthogonal fluorescence imaging of cellular organelles without washing steps. We also elucidated the aromatized pyridazine moiety as the origin of BCN-selective fluorogenic behavior. Additionally, we discovered that the fluorescence of the trans-cyclooctene (TCO) adducts was quenched in aqueous media via photoinduced electron transfer (PeT) process. Interestingly, we observed a distinctive recovery of the initially quenched fluorescence of BODIPY-Tz-TCO upon exposure to hydrophobic media, accompanied by a significant bathochromic shift of its emission wavelength relative to that exhibited by the corresponding BODIPY-Tz-BCN. Leveraging this finding, for the first time, we achieved dual-color bioorthogonal cellular imaging with a single BODIPY-Tz probe.     

Fluorescent derivatives of nucleosides

Fluorescence spectra of formycin anhydronucleosides 5,6,8 and of N-dimethylaminomethylene ribonucleosides 1b, 2, 3a-3c and 4 in aqueous solution at 5-7 × 10^?5 M are reported. Compounds 5 and 6 exhibit a very strong fluorescence emission, ca. 4 and 2 times more intense than that of formycin ( 1a ) accompanied by a bathochromic shift of the emission maximum. Anhydronucleoside 8 also has an increased fluorescence intensity over the parent nucleoside 7 . The level of fluorescence emission is lower in 7 and 8 than in 1a , 5 or 6 . Introduction of N-dimethylaminomethylene group into 1a (compound 1b ) caused a decrease in the fluorescence intensity relative to 1a but a bathochromic shift of the emission maximum. In other instances (compounds 2, 3a-3c, 4 ) the introduction of N-dimethylaminomethylene group led also to fluorescent derivatives. This effect is most pronounced with 2 , whereas the fluorescence intensity of the rest of the group ( 3a-3c and 4 ) is much lower. Compounds 3c and 4 exhibit, however, a profound bathochromic shift in the fluorescence emission maximum relative to 2, 3a or 3b . A possible relationship of the fluorescence emission to the base conformation in formycin and potential use of N-dimethylaminomethylene nucleoside and nucleotide derivatives as fluorescent probes are discussed. J. Heterocyclic Chem., 14 , 135 (1977).     

The excited-state interaction of resazurin and resorufin with amines in aqueous solutions. Photophysics and photochemical reactions

The photophysics and photochemical behavior of the phenoxazin-3-one dyes, resazurin and resorufin, have been studied in aqueous solutions. The irradiation of resazurin in the presence of amines leads to deoxygenation of the N-oxide group, giving resorufin. This photoreaction is highly dependent on the amine structure and is efficient only in the presence of tertiary aliphatic amines. The absorption and fluorescence properties of these dyes are dependent on pH. At pH above 7.5 both dyes are in their anionic form. For resorufin this form is highly fluorescent (phiF = 0.75). At lower pH the fluorescence is strongly reduced. The N-oxide dye presents a very weak fluorescence quantum yield (0.11), which also is reduced at low pH. Flash photolysis experiments allowed characterization of the triplet state and the transients formed after irradiation of these dyes in the absence and presence of amines. The triplet quantum yields are 0.08 for resazurin and 0.04 for resorufin. The photodeoxygenation of N-oxide in the presence of amines occurs from the triplet state.     

Synthesis and study of fluorescent properties of benzothiazolylthieno-thiophene derivatives

A number of benzothiazolylthienothiophenes have been synthesized. Spectral studies have revealed that all these compounds have fluorescent properties that depend on their structure. Dependence of absorption and fluorescence bands positions on the nature of substituents have been established. Increase of the electron-withdrawing nature of substituents led to bathochromic shift of the absorption and fluorescence bands as well as to decrease of the fluorescence intensity.     

Spectral-luminescence characteristics of 1,3-diaryl-4,7-phenanthrolines

The effect of the nature of the substituents and the solvent on the absorption and fluorescence spectra and the fluorescence quantum yields of 1,3-diaryl-4,7-phenanthrolines was studied. Electron-donor groups in the para position of the phenyl ring cause a bathochromic shift of the absorption and fluorescence spectra and an increase in the fluorescence quantum yields. A change in the polarity of the solvent leads to a significant shift of the fluorescence spectra of hydroxy and dialkylamino derivatives of 4,7-phenanthroline.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1651–1654, December, 1987.     

Revisiting noncovalent So2- amine chemistry: an indicator-displacement assay for colorimetric detection of So2

A supramolecular approach for potential detection of SO2 is presented, which is based on the "old" donor-acceptor chemistry between SO2 and amines and includes an indicator-displacement assay. When amines were added to Zn-tetraphenylporphyrin 1 in CHCl3, the solution changed from red to dark green. A bathochromic shift of Deltalambda approximately 10 nm was observed for the Soret band, indicating the formation of 1*amine complexes. After this, SO2 gas was introduced, and the original red color of the solution was restored. The Soret band returned to its position for free porphyrin 1. The 1*amine complexes dissociated, and new SO2*amine adducts formed. Porphyrin 1 thus served as an indirect colorimetric indicator for SO2. The system discriminates between SO2 and such typical exhaust gases as COX, NOX, and H2O. From the indicator-displacement assay, the Kassoc values between 1000 and 30 000 M-1 for SO2*amine complexes were determined, which are comparable to those obtained by direct titration experiments between SO2 and the amines. Spectroscopic features of SO2*amine complexes are also presented.     

Fluorometric sensing of biogenic amines with aggregation-induced emission-active tetraphenylethenes

A fluorometric sensor for detection and identification of biogenic amines with carboxylic acid modified tetraphenylethenes (TPEs) based on aggregation-induced emission (AIE) is reported. A mixture of the carboxylic acid substituted TPE and biogenic amines displayed a blue emission on aggregation, which serves as a "turn-on" fluorescent sensor for the amines, the degree of fluorescence enhancement being dependent on the amine. The chromic responses were utilized to distinguish the amines. A fluorometric sensor array of three TPEs with carboxylic acid groups was shown to identify accurately 10 different amines, including biogenic amines. The response patterns were systematically classified by using linear discriminant analysis (LDA) with 98% classification accuracy. Additional information on the concentration of histamine in a "tuna fish matrix" as an example was assessed by the further analysis of the fluorescence intensity, demonstrating a test for food freshness and quality.     

Determination of aliphatic amines using fluorescence intensity of 4-methyl umbelliferone

Effect of aliphatic amines and their concentration on fluorescence intensity of 4-methyl umbelliferone (4-MU) one of coumarin derivative were investigated. This compound has blue light emission under UV lamp in methanolic solution. Spectral investigation of 4-MU solution containing amine compounds showed lower intensity at 350-410 nm (quenching region) and higher intensity at 430-500 nm (enhancing region) as compared to pure methanolic solution of 4-MU. Fluorescence intensity at isoemitting point was independent from concentration of amines. The variation of fluorescence intensity could be used for determination of aliphatic amines in both quenching and enhancing region. Linear ranges for determination of amines in the quenching region were obtained from Stern-Volmer diagram of 4-MU. Determination of amines at fluorescence enhancing region using inverse fluorescence intensity against inverse amine concentration (bireciprocal plot) were investigated and related equations was also proposed.     

Direct amination of 3-phenothiazone

3-Phenothiazone reacts with primary and secondary aliphatic and aromatic amines to give 2- and 7-monoamino derivatives. Replacement of the bridge oxygen atom of 3-phenoxazinone by a sulfur atom leads to an increase in the reactivity of the 7 position and to a bathochromic shift of the long-wave absorption band in the electronic spectrum.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 353–357, March, 1975.     

Anthracene carboxyimides and their dimers

Soluble anthracenedicarboxyimides have been prepared and undergo a photodimerisation of the anthracene skeleton, which is important for their application as antitumour agents, such as azonafides. Reaction under strongly alkaline conditions causes C-C coupling to form soluble dimeric fluorescent dyes with bathochromic absorption and fluorescence in the NIR region. These dyes are of special interest because of their absorption at longer wavelengths.     

Effects of cetylpyridinium bromide micelles on the spectrofluorimetric characteristics of polycyclic aromatic hydrocarbons

The presence of a micellar medium of cetylpyridinium bromide (CPB) causes, in relation to the aqueous medium, important bathochromic shifts in the excitation spectra of a considerable number of polycyclic aromatic hydrocarbons (PAHs). Furthermore, the CPB acts as a quencher, provoking inhibitions of the fluorescence intensity emitted by PAHs. The micellar inhibition factors show that, generally, the quenching affects alternant hydrocarbons to a greater extent. Some interesting relationships between the hydrocarbon structure and both the characteristic wavelengths of fluorescence spectra and the values of Deltalambda are established.     

Selenodiazole-fused diacetamidopyrimidine, a selective fluorescence sensor for aliphatic monocarboxylates

A designed sensor, selenodiazole-fused pyrimidine ring having two acetylamino groups at 2,4-positions has been synthesized for selective recognition of aliphatic monocarboxylate anions over a wide range of other anions. The recognition study has been carried out by UV-vis and fluorescence methods. A significant bathochromic shift of the fluorescence intensity of the receptor in the presence of carboxylate makes the receptor a discriminating sensor for aliphatic monocarboxylates.     

Fluorescent cyclopentadithiophene derivatives having phenyl-substituted silyl moieties

4,4-Dimethylcyclopenta[2,1-b:3,4-b′]dithiophene derivatives bearing trimethyl-, dimethylphenyl-, diphenylmethyl-, or triphenyl-silyl moieties were synthesized. The introduction of the silyl moieties onto cyclopenta[2,1-b:3,4-b′]dithiophene induced fluorescent emission as well as the bathochromic shift of wavelength at the maximum absorption and fluorescence. It was found that the larger number of phenyl group on silyl moiety resulted in the higher fluorescence quantum yield.