How To Reach Intense Luminescence for Compounds Capable of Excited‐State Intramolecular Proton Transfer?

Photoinduced intramolecular direct arylation allows structurally unique compounds containing phenanthro[9′,10′:4,5]imidazo[1,2‐f]phenanthridine and imidazo[1,2‐f]phenanthridine skeletons, which mediate excited‐state intramolecular proton transfer (ESIPT), to be efficiently synthesized. The developed polycyclic aromatics demonstrate that the combination of five‐membered ring structures with a rigid arrangement between a proton donor and a proton acceptor provides a means for attaining large fluorescence quantum yields, exceeding 0.5, even in protic solvents. Steady‐state and time‐resolved UV/Vis spectroscopy reveals that, upon photoexcitation, the prepared protic heteroaromatics undergo ESIPT, converting them efficiently into their excited‐state keto tautomers, which have lifetimes ranging from about 5 to 10 ns. The rigidity of their structures, which suppresses nonradiative decay pathways, is believed to be the underlying reason for the nanosecond lifetimes of these singlet excited states and the observed high fluorescence quantum yields. Hydrogen bonding with protic solvents does not interfere with the excited‐state dynamics and, as a result, there is no difference between the occurrences of ESIPT processes in MeOH versus cyclohexane. Acidic media has a more dramatic effect on suppressing ESIPT by protonating the proton acceptor. As a result, in the presence of an acid, a larger proportion of the fluorescence of ESIPT‐capable compounds originates from their enol excited states.     

Color‐Tunable Solid‐State Fluorescence Emission from Carbazole‐Based BODIPYs

Several carbazole‐based boron dipyrromethene (BODIPY) dyes were synthesized by organometallic approaches. Thiazole, benzothiazole, imidazole, benzimidazole, triazole, and indolone substituents were introduced at the 1‐position of the carbazole moiety, and boron complexation of each dipyrrin generated the corresponding compounds 1 , 2 a , and 3 – 6 . The properties of these products were investigated by UV/Vis and fluorescence spectroscopy, cyclic voltammetry, X‐ray crystallography, and DFT calculations. These compounds exhibited large Stokes shifts, and compounds 1 , 2 a , and 3 – 5 fluoresced both in solution and in the solid state. Complex 2 a showed the highest fluorescence quantum yield (Φ_F) in the solid state, therefore boron complexes of the carbazole–benzothiazole hybrids 2 b – f , which had several different substituents, were prepared and the effects of the substituents on the photophysical properties of the compounds were examined. The fluorescence properties showed good correlation with the results of crystal‐packing analyses, and the dyes exhibited color‐tunable solid‐state fluorescence.     

Constructing a Nonfluorescent Conformation of AIEgen: A Tetraphenylethene Embedded in the Calix[4]arene's Skeleton

Two novel 1,1‐diphenylmethylidene decorated calix[4]arenes, ( Calix‐DPE(OCH₃)₄ and Calix‐DPE(OH)₄ ), were designed and prepared. The tetraphenylethene (TPE) unit is embedded in the calix[4]arenes skeleton, so the conformation of tetraphenylethene unit is significantly affected by the conformation of calix[4]arene. Unlike the Calix‐DPE(OCH₃)₄ , the Calix‐DPE(OH)₄ does not show the aggregation‐induced emission (AIE) phenomena in solution or the crystal state because of the presence of intramolecular hydrogen bonding, which leads to a cone conformation for the calix[4]arene skeleton in which the embedded phenyl rings of the TPE have to take an almost perpendicular configuration to the C=C bond. This result provides direct evidence that the maximal cross‐chromophore π‐conjugation within the tetraphenylethene is one of the prerequisites of switching on its AIE. This offers the possibility of switching the emission of TPE by conformation changes.     

Near‐IR BODIPY Dyes à la Carte—Programmed Orthogonal Functionalization of Rationally Designed Building Blocks

Herein, we report the synthesis of polyfunctional BODIPY building blocks suitable to be subjected to several reaction sequences with complete chemoselectivity, thereby allowing the preparation of complex BODIPY derivatives in a versatile and programmable manner. The reactions included the Liebeskind–Srogl cross‐coupling reaction (LSCC), nucleophilic aromatic substitution (S_NAr), Suzuki, Sonogashira, and Stille couplings, and a desulfitative reduction of the MeS group. This novel synthetic protocol is a powerful route to design a library of compounds with tailored photophysical properties for advanced applications. In this context, it is noteworthy that it offers a straightforward and cost‐effective strategy to shift the BODIPY emission deep into the near‐infrared spectral region while retaining high fluorescence quantum yields as well as highly efficient and stable laser action. These new dyes outperform the lasing behaviour of dyes considered as benchmarks over the red spectral region, overcoming the important drawbacks associated with these commercial laser dyes, namely low absorption at the standard pump wavelengths (355 and 532 nm) and/or poor photostability.     

Synthesis and Fluorescence Properties of Pyrimidine‐Based Diboron Complexes with Donor–π–Acceptor Structures

Pyrimidine‐based diboron complexes bearing β‐iminoenolate ligands and phenyl groups as bulky substituents on the boron atoms were synthesized as novel fluorescent dyes, and their fluorescence properties were investigated in solution and in the solid state. The diboron complexes with donor–π–acceptor structures showed positive solvatochromism in the fluorescence spectra. The cyano derivative exhibited the most dramatic redshift of the fluorescence maximum F_max with increasing solvent polarity (from 551 nm in n‐hexane to 710 nm in acetonitrile). The diboron complexes showed solid‐state fluorescence in the range of 578–706 nm with fluorescence quantum yields of 0.06–0.28. Additionally, the trifluoromethyl derivative exhibited solvent‐inclusion solid‐state fluorescence. The trifluoromethyl derivative formed toluene‐inclusion and ethyl acetate‐inclusion crystals. The toluene‐inclusion crystal (F_max=668 nm, Φ_f=0.16) showed a blueshifted F_max and higher Φ_f value compared to the original trifluoromethyl derivative (F_max=694 nm, Φ_f=0.08) in the solid state. On the other hand, the F_max (709 nm) and Φ_f (0.04) values of the ethyl acetate‐inclusion crystal were redshifted and lower, respectively.     

Synthesis,Structure, and Optical Studies of Donor–Acceptor‐Type Near‐Infrared (NIR) Aza–Boron‐Dipyrromethene (BODIPY) Dyes

Six donor–acceptor‐type near‐infrared (NIR) aza–boron‐dipyrromethene (BODIPY) dyes and their corresponding aza–dipyrrins were designed and synthesized. The donor moieties at the 1,7‐positions of the aza–BODIPY core were varied from naphthyl to N‐phenylcarbazole to N‐butylcarbazole. The 3,5‐positions were also substituted with phenyl or thienyl groups in the aza–BODIPYs. Photophysical, electrochemical, and computational studies were carried out. The absorption and emission spectra of aza–BODIPYs were significantly redshifted (≈100 nm) relative to the parent tetraphenylaza–BODIPY. Fluorescence studies suggested effective energy transfer (up to 93 %) from donor groups to the aza–BODIPY core in all of the compounds under study. Time‐dependent (TD)‐DFT studies indicated effective electronic interactions between energy donor groups and aza–dipyrrin unit in all the aza–BODIPYs studied. The HOMO–LUMO gap (ΔE) calculated from cyclic voltammetry data was found to be lower for six aza–BODIPYs relative to their corresponding aza–dipyrrins.     

Thermochromic cellulose fibers

A method of obtaining thermochrome cellulose fibers has been developed. The basis technology used to form fibers was the Lyocell process. This method is based on spinning fibers from concentrated solvents of cellulose, using dry‐wet method in aqueous solidification bath. The cellulose solvent used in this process was N‐oxide‐N‐methylomorpholine (NMMO). The studies were to check on the features of the fibers obtained from solvents with thermochrome pigmentation, in order to evaluate their practical use. Thermochrome modifier used in the experiment was Chromicolor®AQ‐INK, Magenta type#27 pigmentation. This modifier was introduced into the spinning solutions in such amounts that fibers obtained from them would contain 1–10 wt% of pigmentation. Fibers formed out of modified solvents underwent spectral values, thermal, physicomechanical analyses, also their sorption features were evaluated. Copyright © 2007 John Wiley & Sons, Ltd.     

等离激元增强拉曼光谱食用合成色素快速检测系统设计

基于等离激元增强拉曼光谱技术,研制出适合现场分析检测的食用合成色素快速检测系统,适用于饮料、肉制品、蜜饯等食品中合成色素的快速检测。检测系统的硬件部分主要由双CPU(ARM和FPGA)主控板、样品前处理模块(含有增强粒子施加装置)、半导体激光光源、光谱数据采集模块构成;软件部分控制样品前处理模块自动运行,并可读取被测样品的拉曼谱图。利用快速检测系统对三种实际样品(蜜饯、汽水、火腿肠)中的食用合成色素胭脂红、柠檬黄、诱惑红进行检测,以验证该系统在食用合成色素检测中的性能。样品检测结果的相对标准偏差小于±5%,表明此检测系统具有良好的灵敏度和重现性,且检测时间短,能够满足食品中合成色素现场快速检测的要求。     

Incorporation of Pigments in TEOS Derived Matrices

Small organic pigments were incorporated in TEOS derived sol-gel layers on glass. The layers were characterised on transparency, lightfastness and pencil hardness. It was found that transparent layers can be made. Pigment loaded layers have a better lightfastness than layers into which dyes are incorporated. As only moderate curing temperatures (160°C) were applied, the organic fraction originating from the organic stabilizer present in the pigment dispersion remains to a large extent in the layer. Therefore the pencil hardness decreases with the amount of stabilizer used to disperse the pigment particles. The type of pigment has no influence on the pencil hardness.     

功能化石墨烯对亚甲基蓝染料吸附的密度泛函理论研究

由于染料在食品,印刷,纺织等行业的广泛应用,水中的染料被广泛发现,染料污染是造成水污染的重要原因之一,因此,对于水中染料进行前处理变得尤为重要.石墨烯和功能化石墨烯的吸附性能可以被应用于水中染料的检测和去除.本研究采用密度泛函理论方法详细探讨了纯石墨烯和功能化石墨烯对亚甲基蓝有机染料污染物的吸附机理.研究结果表明,纯的石墨烯和功能化石墨烯表面对亚甲基蓝染料均有一定程度的吸附,其中环氧原子,羧基和羟基功能化的石墨烯对亚甲基蓝的吸附能力较纯石墨烯吸附能力强,其次是环氧,羧基和羟基三者共同功能化的石墨烯吸附能力最强.研究结果有望为石墨烯材料在有机染料的吸附应用方面提供有意义的理论指导.