Evaluation of a simple and novel fluorescent anion sensor, 4-quinolone, and modification of the emission color by substitutions based on molecular orbital calculations

4-Quinolone (4-QO) was evaluated as a simple and novel fluorescent anion sensor, and the modification of its emission color was carried out. The series of 4-QO derivatives having molecular orbitals with different energy levels was designed by substitutions at the 6 and 7 positions based on the molecular orbital calculations. All derivatives showed drastic fluorescence enhancements in the presence of F⁻ via the intramolecular charge transfer mechanism, and the successful modification of the emission color was achieved. The anion-induced emission colors of these derivatives as well as their binding affinities for F⁻ could be predicted by ab initio quantum chemical calculations, indicating that the present calculations are useful in designing new anion sensors.     

The emission properties of ortho-phenylazo-phenols and naphthols

The fluorescence spectra of a series of orthohydroxy-arylazo compounds were investigated. Fluorescence was detected only in those derivatives known to exist either in tautomeric equilibrium with the corresponding phenylhydrazones, or only in that form. The emission is therefore ascribed to the hydrazone tautomer. There seems to be no evidence for emission from true arylazo compounds. Pronounced changes in absorption and emission spectra of 10⁻³ M solutions were observed at reduced temperatures, and are ascribed to aggregation phenomena.     

Polarity effect on fluorescence of styryl derivatives of quinolizinium salts in micellar media

The styryl derivatives of quinolizinium salts show a marked solvatochromic effect. The p-amino and p-hydroxy derivatives exhibited the greatest effect. The fluorescent intensity of the salts dissolved in nine different solvents is shown to be related to their polarity parameters. The emission was highest for hydroxylic solvents. For all solvents the changes in the fluorescence of the styryl derivatives in the presence of various surfactants is also studied; a great increase in intensity was produced in the presence of sodium dodecylsulfate. This enhanced emission was not observed for non-ionic surfactants. This behaviour is discussed ansd also related to solvent polarity.     

Fluorescence properties of novel 6-butyl-2,3-dicyano-7-methyl-6H-1,4-diazepine styryl dyes containing ethyleneglycol units

The fluorescence properties of novel 6-butyl-2,3-dicyano-7-methyl-6H-1,4-diazepine styryl dyes having mono-, di-, tri-, and tetra(ethyleneglycol) units were examined. The mono(ethylenglycol) derivative was solid at room temperature, whereas the di-, tri-, and tetra(ethylenglycol) derivatives were oily. The monoethyleneglycol derivative showed weak aggregation-induced emission enhancement with fluorescence maximum at 649 nm, which comes from J-aggregates. The fluorescence of oily di-, tri-, and tetra(ethyleneglycol) derivatives in neat form was very weak. No aggregation-induced emission enhancement was observed for the oily derivatives.     

Excited-state intramolecular proton transfer in 2-(2'-arylsulfonamidophenyl)benzimidazole derivatives: the effect of donor and acceptor substituents

A series of water-soluble 2-(2'-arylsulfonamidophenyl)benzimidazole derivatives containing electron-donating and accepting groups attached to various positions of the fluorophore pi-system has been synthesized and characterized in aqueous solution at 0.1 M ionic strength. The measured pK(a)'s for deprotonation of the sulfonamide group of monosubstituted derivatives range between 6.75 and 9.33 and follow closely Hammett's free energy relationship. In neutral aqueous buffer, all compounds undergo efficient excited-state intramolecular proton transfer (ESIPT) to yield a strongly Stokes-shifted fluorescence emission from the phototautomer. Upon deprotonation of the sulfonamide nitrogen at high pH, ESIPT is interrupted to yield a new, blue-shifted emission band. The peak absorption and emission energies were strongly influenced by the nature of the substituents and their attachment positions on the fluorophore pi-system. The fluorescence quantum yield of the ESIPT tautomers revealed a significant correlation with the observed Stokes shifts. The study provides valuable information regarding substituent effects on the photophysical properties of this class of ESIPT fluorophores in an aqueous environment and may offer guidelines for designing emission ratiometric pH or metal-cation sensors for biological applications.     

Study of the substituent groups effect on the room-temperature phosphorescent emission of fluorene derivatives in solution

We present here the first study of the effect of substituent groups and the chemical structure of fluorene derivatives on phosphorescent emission. A group of fluorene derivatives have been studied with a new methodology of room-temperature phosphorescence emission called heavy atom induced room-temperature phosphorescence (HAI-RTP). This methodology makes use of RTP emission directly from the compound in fluid solution, without a protective medium but only with the presence of high concentrations of heavy atom perturbers and an oxygen scavenger. These experimental conditions permit sufficient interaction between the perturbers and the phosphors to produce effective population of the triplet states of the latter and, consequently, intense phosphorescent emission. Good deoxygenation conditions are obtained using sodium sulfite as the oxygen scavenger. We show here that it is possible that many fluorene derivatives can exhibit RTP emission in aqueous solutions in the absence of a protective medium. Phosphorescence spectral characteristics of these compounds (excitation and emission wavelengths and lifetime) and the optimization of the chemical variables involved in the phosphorescence phenomenon are reported. Under optimal experimental conditions, calibration graphs and detection and quantification limits in the ng ml⁻¹ level have been established.     

Design of Stimuli-Responsive Phenothiazine Derivatives with Triplet-Related Dual Emission and High-Contrast Mechanochromism Guided by Polymorph Prediction

The development of high-contrast stimulus-responsive materials with excited triplet emission is of great significance for anti-counterfeiting, sensor and memory applications, but remains a challenge. Here, we report a strategy for the rational design of stimulus-responsive phenothiazine derivatives with triplet-related dual emissions and high-contrast mechanochromism guided by Polymorph Prediction. The designed phenothiazine derivatives have the characters of simple structures, a facile synthetic procedure, and a good crystalline nature. We found that the crystals of those derivatives with the potential to form both quasi-axial (ax) and quasi-equatorial (eq) conformations could undergo conformation transition and show significant emission difference (Δλ_em>100 nm) under mechanical force. Meanwhile, all these phenothiazine derivatives exhibit aggregation-induced emission and emit room-temperature phosphorescence or thermally activated delayed fluorescence. The significant luminescent change of these materials under different stimuli gives them promise for applications in encryption and anti-counterfeiting.     

Enhanced luminescence determination of horseradish peroxidase conjugates: Application of Benzothiazole Derivatives as Enhancers in Luminescence Assays on Microtitre Plates

The benzothiazole derivatives, 2-cyano-6-hydroxybenzothiazole, 6-hydroxybenzothiazole and dehydroluciferin, enhance light emission from the horseradish peroxidase-catalysed oxidation of cyclic diacylhydrazides such as luminol. The relatively intense and prolonged light emission from reactions enhanced by benzothioazole derivatives is easily detected and is utilised in a rapid assay for specific antibody against cytomegalovirus done on black polystyrene microtitre plates. Rapid measurements are possible when a prototype manually-operated microtitre plate reader is used. Light emission from individual wells was quantified by an end-window photomultiplier tube positioned either just above the microtitre plate surface, or some distance away, the light being collected through a fibre optic light guide. The assay was also done on transparent (poly(vinyl chloride) microtitre plates with simultaneous measurement of light emission from several wells; this was achieved with simple instrumentation and a 20 000-ASA Polaroid instant photographic film.     

Excited State Intramolecular Proton Transfer in Ethynyl‐Extended Regioisomers of 2‐(2′‐Hydroxyphenyl)benzothiazole: Effects of the Position and Electronic Nature of Substituent Groups

Although the organic dyes based on excited state intramolecular proton transfer (ESIPT) mechanism have attracted significant attention, the structure‐property relationship of ESIPT dyes needs to be further exploited. In this paper, three series of ethynyl‐extended regioisomers of 2‐(2′‐hydroxyphenyl)benzothiazole (HBT), at the 3′‐, 4′‐ and 6‐positions, respectively, have been synthesized. Changes in the absorption and emission spectra were correlated with the position and electronic nature of the substituent groups. Although 4′‐ and 6‐substituted HBT derivatives exhibited absorption bands at longer wavelengths, the keto‐emission of 3′‐substituted HBT derivatives was found at a substantially longer wavelength. The gradual red‐shifted fluorescence emission was found for 3′‐substituted HBT derivatives where the electron‐donating nature of substituent group increased, which was opposite to what was observed for 4′‐ and 6‐substituted HBT derivatives. The results derived from the theoretical calculations were in conformity with the experimental observations. Our study could potentially provide experimental and theoretical basis for designing novel ESIPT dyes that possess unique fluorescent properties.     

Fluorescence derivatisation of amino acids in short and long-wavelengths

3-(Naphthalen-1-ylamino)propanoic acid was coupled to the amino group of the main and lateral chains of various amino acids in order to evaluate its applicability as a fluorescent derivatising reagent. The resulting amino acid derivatives are strongly fluorescent with a maximum emission of about 415 nm. Condensation of these derivatives with 5-ethylamino-4-methyl-2-nitrosophenol hydrochloride resulted in the corresponding blue benzo[a]phenoxazinium conjugates, also revealing strong fluorescence in ethanol and water at physiological pH and good quantum yields, but with emission wavelengths between 644 and 657 nm, which was preferable in biological assays.     

LUMINESCENCE STUDIES ON FORMYCIN, ITS AGLYCONE, AND THEIR N-METHYL DERIVATIVES: TAUTOMERISM, SITES OF PROTONATION AND PHOTOTAUTOMERISM

Abstract— A detailed study has been made of the luminescence spectra of 3-β-d -ribofuranosyl-7-amino-pyrazolo(4,3-d)pyrimidine (formycin A), 3-propyl-7-aminopyrazolo(4,3-d)pyrimidine (7APP), and their various N-methyl derivatives, at room temperature and in methanol-water glasses at 77 K. Comparisons of the foregoing, together with the observed dependence of the emission spectra of formycin and 7APP on excitation wavelength, demonstrated that these consist of two tautomeric species, N(1)H and N(2)H, both of which emit at 300 and 77 K. The two tautomers may be distinguished by the location of the emission maxima, especially for phosphorescence, and quantum yields for emission. Comparisons of the emission spectra of the protonated forms of 7APP and its N-methyl derivatives showed that the fluorescence of the cations of 7APP and its N,- and N₂-methyl derivatives originates from the forms protonated on N(4). By contrast, the forms protonated on N(6) contribute appreciably to the phosphorescence at 77 K. On the basis of the emission spectra at 77 K, it is concluded that the major tautomeric form of the formycin cation is N(1)H,N(4)H₊, but there is also some contribution by the form N(2)H,N(4)H₊. In acid medium at room temperature, there is photodissociation of a proton from the pyrazole ring of the formycin cation. This leads to formation in the state S! of the tautomeric species N(4)H, which does not exist in the ground state. This conclusion, similar to that previously reported for the analogous isomeric 4-aminopyrazolo(3,4-d)pyrimidines, is derived from a comparison of the fluorescence spectra of the cations of formycin and N₄-methylformycin, which exhibit two bands at 375 and 440 nm, the latter corresponding to the emission of the neutral form of N,i-methylformycin. The proposed mechanism of phototautomerization is supported by a study of solvent and salt effects.     

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).     

Excited state intramolecular proton transfer of novel conjugated derivatives containing hydroxy and imino groups

<正>This letter presents excited state intramolecular proton transfer(ESIPT) of new conjugated derivatives containing hydroxy and imino groups.ESIPT occurrence in one photon process is confirmed by well-separated emission band for the derivatives.Twophoton absorption(TPA) induced ESIPT emission has been determined by Ti:sapphire femtosecond laser tuning from 700 nm to 800 nm at the internals of 20 nm.     

Functional Polymers. XXV. Fluorescence Spectra of Derivatives of Methyl Salicylate and Copolymers of Methyl Vinylsalicylates

Ultraviolet absorption and fluorescence spectra of methyl salicylate, isomers of methyl salicylate derivatives, and polymers with units of isomers of methyl salicylate have been investigated. The λ_max of methyl salicylate and its derivatives is centered around 310 nm. When the phenolic hydroxyl group is acetylated, the maximum is at 285 nm. Fluorescent emission maxima depend on the excitation wavelength. Two groups of maxima centered at 350 and 460 nm indicate that two molecular species (already present in the ground state) of the methyl salicylate moiety, probably tautomers, play essential parts as photoexcited states in the photophysics of methyl salicylate derivatives.     

多芳基吡咯衍生物的发光性质及其应用

荧光分子在良溶剂中基本不发光或发光较弱,而在聚集状态下发光较强的现象,称为聚集诱导发光(Aggregation-induced emission,AIE)现象,这与传统的聚集导致猝灭(Aggregation-caused quenching,ACQ)现象相反。本文研究了多苯基吡咯衍生物的结构与发光性能的关系。通过比较吡咯衍生物的单晶结构和发光性质发现扭曲的结构可以限制共轭发光基团的分子内旋转(RIR),这是产生AIE现象的主要原因。羧酸化的吡咯衍生物可以对Al³⁺实时、选择性检测。由DMF诱导的三苯基吡咯羧酸衍生物(TPPA)重结晶在固态时出现可控的荧光发射,它具备很好的温度选择性,响应迅速,并可以循环利用,这证明TPPA可以作为一种热响应材料用于温度监控设备中。     

Analysis of Pseudouridine by Fluorescence Spectrometry

Abstract

Fluorescence spectral properties of pseudouridine, an important biological indicator, have been measured for the first time in this study. The fluorescence quantum yield is maximal in aqueous solution with pH values above 9 with spectral properties characteristic of 5 alkyl substituted uracil derivatives. Chromatographic analysis shows the fluorescence is associated only with the pseudouridine peak. The concentration dependence of fluorescence is linear from 4 to 45 micromolar at pH 11.5. The excitation maximum is about 295 nm and the emission is broad with a maximum at about 390 nm. Addition of pseudouridine to urine extracts gives a linear increase in fluorescence with increasing pseudouridine concentration.     

Synthesis and characterization of highly hindered and thermally stable poly(1,4‐spirobifluorenylenevinylene) derivative

A new poly(1,4‐spirobifluorenylenevinylene) having advantage PPV and spirobifluorene as new emissive family was synthesized. Compared with PPV derivatives that usually have a tolane bisbenzyl defect, the polymer has the defect free structure because of the steric hindrance of the asymmetric bulky spirobifluorenyl group. Compared with spirobifluorene derivatives that usually have a low solubility, the polymer has the good solubility in common organic solvents. The polymer was amorphous and showed high PL quantum efficiency and high thermal stability with high T_g. The PL emission peaks were shown at 480–490 nm in solution and film, respectively, which may represent the bluest emission peak reported for fully conjugated PPV derivatives. The study of thermal annealing of PL spectrum showed excimer formation inhibited. The thermal and optoelectronic properties of the polymer imply that it is a promising material for the PLED application. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 900–907, 2007.     

Theoretical Insight into the Origin of Large Stokes Shift and Photophysical Properties of Anilido‐Pyridine Boron Difluoride Dyes

The geometric and electronic structures and photophysical properties of anilido‐pyridine boron difluoride dyes 1 – 4 , a series of scarce 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) derivatives with large Stokes shift, are investigated by employing density functional theory (DFT) and time‐dependent DFT (TD‐DFT) calculations to shed light on the origin of their large Stokes shifts. To this end, a suitable functional is first determined based on functional tests and a recently proposed index—the charge‐transfer distance. It is found that PBE0 provides satisfactory overall results. An in‐depth insight into Huang–Rhys (HR) factors, Wiberg bond indices, and transition density matrices is provided to scrutinize the geometric distortions and the character of excited states pertaining to absorption and emission. The results show that the pronounced geometric distortion due to the rotation of unlocked phenyl groups and intramolecular charge transfer are responsible for the large Stokes shift of 1 and 2 , while 3 shows a relatively blue‐shifted emission wavelength due to its mild geometric distortion upon photoemission, although it has a comparable energy gap to 1 . Finally, compound 4 , which is designed to realize the rare red emission in BODIPY derivatives, shows desirable and expected properties, such as high Stokes shift (4847 cm^?1), red emission at 660 nm, and reasonable fluorescence efficiency. These properties give it great potential as an ideal emitter in organic light‐emitting diodes. The theoretical results could complement and assist in the development of BODIPY‐based dyes with both large Stokes shift and high quantum efficiency.     

Modulation of Aggregation‐Induced Emission and Electroluminescence of Silole Derivatives by a Covalent Bonding Pattern

The deciphering of structure–property relationships is of high importance to rational design of functional molecules and to explore their potential applications. In this work, a series of silole derivatives substituted with benzo[b]thiophene (BT) at the 2,5‐positions of the silole ring are synthesized and characterized. The experimental investigation reveals that the covalent bonding through the 2‐position of BT (2‐BT) with silole ring allows a better conjugation of the backbone than that achieved though the 5‐position of BT (5‐BT), and results in totally different emission behaviors. The silole derivatives with 5‐BT groups are weakly fluorescent in solutions, but are induced to emit intensely in aggregates, presenting excellent aggregation‐induced emission (AIE) characteristics. Those with 2‐BT groups can fluoresce more strongly in solutions, but no obvious emission enhancements are found in aggregates, suggesting they are not AIE‐active. Theoretical calculations disclose that the good conjugation lowers the rotational motions of BT groups, which enables the molecules to emit more efficiently in solutions. But the well‐conjugated planar backbone is prone to form strong intermoelcular interactions in aggregates, which decreases the emission efficiency. Non‐doped organic light‐emitting diodes (OLEDs) are fabricated by using these siloles as emitters. AIE‐active silole derivatives show much better elecroluminescence properties than those without the AIE characterisic, demonstrating the advantage of AIE‐active emitters in OLED applications.     

Reaction-based fluorescent probe for detecting of sulfur dioxide derivatives and hydrazine via distinct emission signals

Recently, the construction of multiple analytes responsive fluorescent probes with distinct emission signals has attracted widely attention. Thus, we have designed and synthesized a new fluorescent probe, 2-(2-hydroxyphenyl)benzothiazole dye skeleton (HBT-1), for the detection of sulfur dioxide and hydrazine. Significant fluorescence enhancements in two distinct emission bands (λ_em?=?464?nm and 498?nm) were generated when HBT-1 reacted with sulfur dioxide derivatives or hydrazine, respectively. Furthermore, the probe HBT-1 response can be saturated surpurisingly at the low concentration (100?μM), shorter reaction time for sulfur dioxide derivatives, while a longer reaction time and greater concentration (400?μM) for hydrazine. In other words, the probe HBT-1 can detect sulfur dioxide derivatives without hydrazine interference at low analyte concentrations.