Cyclobutenediylium Dyes

In agreement with the aromaticity and electrophilic behavior of squaric acid, a cyclobutenediyliumtetroxide ion is formulated as a limiting form of the squarate dianion. These views are confirmed by the structure of a series of new compounds that are readily obtainable from squaric acid or its derivatives, and most of which are deeply colored. The compounds contain the cyclobutenediyliumdioxide grouping as the chromophore, and form a new class of dyes, for which the name cyclobutenediylium dyes is proposed.     

Highly Fluorescent and Water‐Soluble Diketopyrrolopyrrole Dyes for Bioconjugation

The preparation of highly water‐soluble and strongly fluorescent diketopyrrolopyrrole (DPP) dyes using an unusual taurine‐like sulfonated linker has been achieved. Exchanging a phenyl for a thienyl substituent shifts the emission wavelength to near λ=600 nm. The free carboxylic acid group present in these new derivatives was readily activated and the dyes were subsequently covalently linked to a model protein (bovine serum albumin; BSA). The bioconjugates were characterized by electronic absorption, fluorescence spectroscopy and MALDI‐TOF mass spectrometry, thus enabling precise determination of the labeling density (ratio DPP/BSA about 3 to 8). Outstanding values of fluorescence quantum yield (30 % to 59 %) for these bioconjugates are obtained. The photostability of these DPP dyes is considerably greater than that of fluorescein under the same irradiation conditions. Remarkably low detection limits between 80 and 300 molecules/μm² were found for the BSA bioconjugates by fluorescence imaging with a epifluorescence microscope.     

吡啶酮偶氮分散染料光谱性能

吡啶酮分散染料应用性能优异 ,其色谱主要为黄色及橙色 ,尤以黄色为主 [1～ 3]。Cheng和 Peng等 [2 ,3] 对以氨基噻二唑类和苯系芳胺为重氮组分的吡啶酮类染料的可见光谱及互变异构进行了研究 ,Ertan等 [4 ] 研究了以氨基噻唑和氨基苯并噻唑为重氮组分的吡啶酮偶氮染料的可见光谱 ,结果表明上述染料色谱主要仍为黄色。为得到具有更深色谱的吡啶酮类染料 ,我们用不同的重氮组分合成了一系列吡啶酮分散染料 ,研究了其在不同溶剂及不同 p H值下的光谱 ,发现该类染料亦可达到红、甚至蓝色谱 ,其中染料 1 a、1 b及 2 b3个染料结构未见报道。O2 …     

New indolium and quinolinium dyes sensitive to aqueous halide ions at physiological concentrations

Twelve new highly fluorescent dyes have been produced by the reaction of two heterocyclic nitrogen bases with 8-bromooctanoic acid, 11-bromoundecanoic acid and 15-bromopentadecanoic acid. The bromide counter ions of the first six dyes have been replaced with the tetraphenylborate ion. Unlike the bases themselves, the quaternary salts are water soluble and have fluorescence characteristics independent of pH in the pH range 7–11. Both the fluorescence intensity and fluorescence lifetime of dyes 1–12 are reduced in the presence of aqueous halide ions allowing halide concentrations to be determined accurately at physiological levels. All the dyes have been characterised in terms of steady state fluorescence spectra and steady-state Stern-Volmer analysis.     

Syntheses and Derivatives of Squaric Acid

Squaric acid (dihydroxycyclobutenedione), the dianion of which may be regarded as a novel aromatic system, has recently become readily accessible by simple syntheses. The acidic character of squaric acid manifests itself in the formation of salts and of lower alkyl esters, which can be converted into the amides. Squaric acid dichloride shows in its reactions typical acyl chloride behavior. Condensation of squaric acid with pyrrole, phenol, and azulene derivatives yields cyclotrimethine dyes.     

The fast atom bombardment mass spectra of xanthane dyes

The Fast Atom Bombardment mass spectra of a number of xanthane dyes are reported. These dyes are insufficiently volatile to give spectra by conventional electron impact ionization. Fragmentation pathways have been determined by metastable linked scan techniques and accurate masses obtained by peak matching. The xanthane dyes may be readily identified from their FAB spectra by the presence of characteristic ions.     

Induced phase separation in cellulose nanocrystal suspensions containing ionic dye species

Suspensions of negatively charged cellulose nanocrystal are obtained by sulfuric acid hydrolysis of cotton cellulose. Within a specific concentration range, the suspensions spontaneously phase separate to give isotropic and chiral nematic phases. Added anionic dyes of varying charge cause separation of an isotropic phase from the highly concentrated, completely anisotropic suspensions; these dyes have a much greater effect on the suspensions than the equivalent ionic strength of a simple 1:1 electrolyte (sodium chloride). Neutral, cationic and cellulose-binding anionic dyes do not cause phase separation in the anisotropic cellulose suspensions.     

Biomimetic dyes as affinity chromatography tools in enzyme purification

Affinity adsorbents based on immobilized triazine dyes offer important advantages circumventing many of the problems associated with biological ligands. The main drawback of dyes is their moderate selectivity for proteins. Rational attempts to tackle this problem are realized through the biomimetic dye concept according to which new dyes, the biomimetic dyes, are designed to mimic natural ligands. Biomimetic dyes are expected to exhibit increased affinity and purifying ability for the targeted proteins. Biocomputing offers a powerful approach to biomimetic ligand design. The successful exploitation of contemporary computational techniques in molecular design requires the knowledge of the three-dimensional structure of the target protein, or at least, the amino acid sequence of the target protein and the three-dimensional structure of a highly homologous protein. From such information one can then design, on a graphics workstation, the model of the protein and also a number of suitable synthetic ligands which mimic natural biological ligands of the protein. There are several examples of enzyme purifications (trypsin, urokinase, kallikrein, alkaline phosphatase, malate dehydrogenase, formate dehydrogenase, oxaloacetate decarboxylase and lactate dehydrogenase) where synthetic biomimetic dyes have been used successfully as affinity chromatography tools.     

A facile synthesis of phthalein indicator dyes

The use of methanesulfonic acid offers a novel and highly efficient method for the synthesis of phthalein indicator dyes in excellent yields on an industrial scale.     

Water-soluble phosphonate-substituted BODIPY derivatives with tunable emission channels

Water-soluble BODIPY dyes have been readily obtained by introduction of phosphonate fragments either on the boron for the green and yellow emitting dyes or on the side chain for the red emitting dyes. Hydrolysis of the phosphonate is realized at the end of the reaction sequence and allows isolation of the targets by precipitation. All these novel dyes are soluble and fluorescent in water with quantum yields in the 23-59% range and emission wavelength spanning from 667 to 509 nm.     

Push-pull amino succinimidyl ester thiophene-based fluorescent dyes: synthesis and optical characterization

The design and synthesis of new fluorescent dyes with emission range at 490-650 nm are described. Their structural and electronic properties have been characterized by both experimental techniques and quantum-chemical calculations. The chromophores are donor-π-bridge-acceptor push-pull compounds with a π bridge of phenyl and thiophene rings and their combination. Compared with previous thiophene fluorophores, these dyes show significant redshift in the absorption and emission spectra and offer compact, red-emitting fluorophores. The dyes have amino succinimidyl active ester and can be readily conjugated to proteins, polymers and other amino-group-containing materials.     

Bioconjugatable Azo‐Based Dark‐Quencher Dyes: Synthesis and Application to Protease‐Activatable Far‐Red Fluorescent Probes

We describe the efficient synthesis and one‐step derivatization of novel, nonfluorescent azo dyes based on the Black Hole Quencher‐3 (BHQ‐3) scaffold. These dyes were equipped with various reactive and/or bioconjugatable groups (azido, α‐iodoacetyl, ketone, terminal alkyne, vicinal diol). The azido derivative was found to be highly reactive in the context of copper‐catalyzed azide–alkyne cycloaddition (CuAAC) reactions and allowed easy synthetic access to the first water‐soluble (sulfonated derivative) and aldehyde‐modified BHQ‐3 dyes, the direct preparation of which failed by means of conventional azo‐coupling reactions. The aldehyde‐ and α‐iodoacetyl‐containing fluorescence quenchers were readily conjugated to aminooxy‐ and cysteine‐containing peptides by the formation of a stable oxime or thioether linkage, respectively. Further fluorescent labeling of the resultant peptide conjugates with red‐ or far‐red‐emitting rhodamine or cyanine dyes through sequential and/or one‐pot bioconjugations, led to novel Förster resonance energy transfer (FRET) based probes suitable for the in vivo detection and imaging of urokinase plasminogen activator, a key protease in cancer invasion and metastasis.     

Synthesis of novel quinaldine-based squaraine dyes: effect of substituents and role of electronic factors

[reaction: see text] Condensation of squaric acid with quinaldinium salts containing electron-donating substituents gave only the semisquaraines. However, with salts possessing electronegative and electron-withdrawing groups, the squaraine dyes were isolated in quantitative yields. The semisquaraines formed undergo condensation with highly nucleophilic salts yielding the unsymmetrical squaraine dyes. These results demonstrate the role of electronic factors and provide valuable information for the design of efficient squaraine-based sensitizers that can have potential applications in photodynamic therapy.     

A simple and effective “capping” approach to readily tune the fluorescence of near-infrared cyanines

Heptamethine cyanines are favorable for fluorescence imaging applications in biological systems owing to their near-infrared (NIR) absorption and emission. However, it is very difficult to quench the fluorescence of NIR dyes by the classic photoinduced electron transfer mechanism due to their relatively high-lying occupied molecular orbital energy levels. Herein, we present a simple and effective “capping” approach to readily tune the fluorescence of NIR cyanines. The resulting new functional NIR CyBX (X = O, N, or S) dyes not only retain the intact tricarbocyanine scaffold, but also have a built-in switch to regulate the fluorescence by spiro-cyclization. When compared to traditional cyanines, novel CyBX dyes have a superior character in that their NIR optical properties can be readily tuned by the intrinsic spiro-cyclization mechanism. We expect that this “capping” strategy can be extended across not only the visual spectrum but also to structurally distinct fluorophores.     

呫吨染料合成方法研究进展

呫吨染料是一类重要荧光染料,其良好的光物理性质使其得到了广泛应用。呫吨染料一般通过富电子的间苯二酚(或间氨基苯酚)与邻苯二甲酸酐在酸催化条件下缩合得到。近年来,呫吨染料在生物显微成像领域获得广泛应用,染料结构也日趋复杂,传统的合成方法不能满足需要,因而不断有新的呫吨染料合成方法见诸文献。本文简要概述了既有呫吨染料合成路线,并分析讨论了各方法的优缺点及适用底物范围。     

Masked Rhodamine Dyes of Five Principal Colors Revealed by Photolysis of a 2‐Diazo‐1‐Indanone Caging Group: Synthesis,Photophysics, and Light Microscopy Applications

Caged rhodamine dyes (Rhodamines NN) of five basic colors were synthesized and used as “hidden” markers in subdiffractional and conventional light microscopy. These masked fluorophores with a 2‐diazo‐1‐indanone group can be irreversibly photoactivated, either by irradiation with UV‐ or violet light (one‐photon process), or by exposure to intense red light (λ～750 nm; two‐photon mode). All dyes possess a very small 2‐diazoketone caging group incorporated into the 2‐diazo‐1‐indanone residue with a quaternary carbon atom (C‐3) and a spiro‐9H‐xanthene fragment. Initially they are non‐colored (pale yellow), non‐fluorescent, and absorb at λ=330–350 nm (molar extinction coefficient (ε)≈10⁴ M^?1 cm^?1) with a band edge that extends to about λ=440 nm. The absorption and emission bands of the uncaged derivatives are tunable over a wide range (λ=511–633 and 525–653 nm, respectively). The unmasked dyes are highly colored and fluorescent (ε= 3–8×10⁴ M^?1 cm^?1 and fluorescence quantum yields (?)=40–85 % in the unbound state and in methanol). By stepwise and orthogonal protection of carboxylic and sulfonic acid groups a highly water‐soluble caged red‐emitting dye with two sulfonic acid residues was prepared. Rhodamines NN were decorated with amino‐reactive N‐hydroxysuccinimidyl ester groups, applied in aqueous buffers, easily conjugated with proteins, and readily photoactivated (uncaged) with λ=375–420 nm light or intense red light (λ=775 nm). Protein conjugates with optimal degrees of labeling (3–6) were prepared and uncaged with λ=405 nm light in aqueous buffer solutions (?=20–38 %). The photochemical cleavage of the masking group generates only molecular nitrogen. Some 10–40 % of the non‐fluorescent (dark) byproducts are also formed. However, they have low absorbance and do not quench the fluorescence of the uncaged dyes. Photoactivation of the individual molecules of Rhodamines NN (e.g., due to reversible or irreversible transition to a “dark” non‐emitting state or photobleaching) provides multicolor images with subdiffractional optical resolution. The applicability of these novel caged fluorophores in super‐resolution optical microscopy is exemplified.     

Mono- versus bidentate ligands in rhodium-catalyzed asymmetric hydrogenation. A comparative rate study

[reaction: see text] Bidentate chiral phosphines are no longer essential for achieving a fast and highly enantioselective hydrogenation of alpha- or beta-dehydroamino acid derivatives. In particular, a readily accessible and stable monodentate phosphoramidite can be highly effective in these asymmetric hydrogenations.     

General route to symmetric and asymmetric meso-CF3-3(5)-aryl(hetaryl)- and 3,5-diaryl(dihetaryl)-BODIPY dyes

A general efficient route to hitherto inaccessible symmetric and asymmetric meso-CF(3)-BODIPY dyes has been developed. The key stages include the reduction of available 2-trifluoroacetylpyrroles to the corresponding alcohols which are further condensed with pyrroles. The method allows the BODIPY with 3(5)aryl(hetaryl) and 3,5-diaryl(hetaryl) substituents to be readily assembled. The BODIPY dyes synthesized fluoresce (Φ(f) = 0.56-1.00) in the 560-680 nm region.     

具有超高阳离子染料去除能力的磺酸功能化球形共价有机框架

通过三醛基间苯三酚(TFP)与2,2′-联苯胺二磺酸(BDSA)的席夫碱反应, 合成了β-酮烯胺连接的磺酸功能化球形共价有机框架(TFP-BDSA COF). 所得阴离子型TFP-BDSA可迅速吸附如亚甲基蓝(MLB)、 结晶紫(CV)和罗丹明B(RhB)等阳离子染料, 而对如甲基橙(MO)和荧光素钠(FS)等阴离子染料则难以吸附, 该COF可实现基于电荷模式的阴离子、 阳离子染料的分离. TFP-BDSA对阳离子染料的吸附动力学均遵循拟二级吸附动力学模型, 吸附过程符合Langmuir吸附模型, 其对MLB, CV和RhB的最大吸附容量分别高达1116, 1429和1638 mg/g. 与其它COFs材料相比, TFP-BDSA对CV和RhB的吸附容量最高. 该工作可为开发功能COFs材料实现对废水中有机污染物的快速吸附和有效去除提供参考.     

Inorganic–Organic Hybrid Nanoparticles with Biocompatible Calcium Phosphate Thin Shells for Fluorescence Enhancement

Polymeric micelles consisting of asymmetric triblock copolymers were successfully used for fabrication of robust hybrid nanoparticles with highly biocompatible calcium phosphate shells. The hydrophobic polystyrene core encapsulates hydrophobic fluorescent dyes such as Nile red. The anionic polyacrylic acid provides the site for the mineralization reaction of calcium phosphate. The polyethylene glycol corona stabilizes the hybrid nanoparticles. Fluorescent dyes can be used as imaging agents for determining the location of the nanoparticles and to give an observable indication of drug delivery, while the calcium phosphate shell can enhance the fluorescence of the encapsulated dye.