Integration of the 1,2,3‐Triazole “Click” Motif as a Potent Signalling Element in Metal Ion Responsive Fluorescent Probes

In a systematic approach we synthesized a new series of fluorescent probes incorporating donor–acceptor (D‐A) substituted 1,2,3‐triazoles as conjugative π‐linkers between the alkali metal ion receptor N‐phenylaza‐[18]crown‐6 and different fluorophoric groups with different electron‐acceptor properties (4‐naphthalimide, meso‐phenyl‐BODIPY and 9‐anthracene) and investigated their performance in organic and aqueous environments (physiological conditions). In the charge‐transfer (CT) type probes 1 , 2 and 7 , the fluorescence is almost completely quenched by intramolecular CT (ICT) processes involving charge‐separated states. In the presence of Na⁺ and K⁺ ICT is interrupted, which resulted in a lighting‐up of the fluorescence in acetonitrile. Among the investigated fluoroionophores, compound 7 , which contains a 9‐anthracenyl moiety as the electron‐accepting fluorophore, is the only probe which retains light‐up features in water and works as a highly K⁺/Na⁺‐selective probe under simulated physiological conditions. Virtually decoupled BODIPY‐based 6 and photoinduced electron transfer (PET) type probes 3 – 5 , where the 10‐substituted anthracen‐9‐yl fluorophores are connected to the 1,2,3‐triazole through a methylene spacer, show strong ion‐induced fluorescence enhancement in acetonitrile, but not under physiological conditions. Electrochemical studies and theoretical calculations were used to assess and support the underlying mechanisms for the new ICT and PET 1,2,3‐triazole fluoroionophores.     

Rational Design of a Solvatochromic Fluorescent Uracil Analogue with a Dual‐Band Ratiometric Response Based on 3‐Hydroxychromone

Fluorescent nucleoside analogues with strong and informative responses to their local environment are in urgent need for DNA research. In this work, the design, synthesis and investigation of a new solvatochromic ratiometric fluorophore compiled from 3‐hydroxychromones (3HCs) and uracil fragments are reported. 3HC dyes are a class of multi‐parametric, environment‐sensitive fluorophores providing a ratiometric response due to the presence of two well‐resolved bands in their emission spectra. The synthesized conjugate demonstrates not only the preservation but also the improvement of these properties. The absorption and fluorescence spectra are shifted to longer wavelengths together with an increase of brightness. Moreover, the two fluorescence bands are better resolved and provide ratiometric responses across a broader range of solvent polarities. To understand the photophysical properties of this new fluorophore, a series of model compounds were synthesized and comparatively investigated. The obtained data indicate that uracil and 3HC fragments of this derivative are coupled into an electronic conjugated system, which on excitation attains strong charge‐transfer character. The developed fluorophore is a prospective label for nucleic acids. Abstract in Ukrainian: .     

Construction of Fluorescent Probes Via Protection/Deprotection of Functional Groups: A Ratiometric Fluorescent Probe for Cu2+

Herein a ratiometric fluorescent Cu²⁺ probe was rationally constructed in a straightforward manner with the concept of aldehyde group protection/deprotection. The probe showed a ratiometric fluorescent response to Cu²⁺ with a large emission wavelength shift (>100 nm) and displayed high selectivity for Cu²⁺ over other metal ions due to distinct deprotection conditions. In addition, a Cu²⁺‐promoted dethioacetalization mechanism was proposed.     

Multicolored‐Fluorescence Switching of ICT‐Type Organic Solids with Clear Color Difference: Mechanically Controlled Excited State

A donor–acceptor‐type fluorophore containing a twisted diphenylacrylonitrile and triphenylamine has been developed by using the Suzuki reaction. The system indicates typical intramolecular charge‐transfer properties. Upon mechanical grinding or hydrostatic pressure, the fluorophore reveals a multicolored fluorescence switching. Interestingly, a fluorescence color transition from green to red was clearly observed, and the change of photoluminescent (PL) wavelength gets close to 111 nm. The mechanisms of high‐contrast mechanochromic behavior are fully investigated by techniques including powder XRD, PL lifetime, high‐pressure PL lifetime, and Raman spectra analysis. The tremendous PL wavelength shift is attributed to gradual transition of excited states from the local excited state to the charge‐transfer state.     

Synthesis and fluorescence properties of 2-aryl-3-hydroxyquinolones, a new class of dyes displaying dual fluorescence

A series of 2-aryl-3-hydroxyquinolones (3HQs) with different electron donating aryl substituents at the position 2 were synthesized. Their absorption and fluorescence properties were studied in solvents of medium and high polarity. Almost all the synthesized 3HQs display dual fluorescence in the tested solvents, in line with an excited state intramolecular proton transfer reaction. For N-methyl substituted compounds, the intensity ratio of the two emission bands was found to be exquisitely sensitive to solvent polarity, with a two orders of magnitude change from toluene to dimethylsulfoxide. Consequently, these compounds appear as prospective polarity fluorescent labels for proteins and nucleic acids.     

一种蓝光单体的合成及其荧光性能研究

吡唑啉衍生物在生物医药[1,2]应用的领域非常广泛.吡唑啉还是一种优质的发光材料[3],其发射波长位于450nm左右,具有很高的荧光量子效率,且发光波长窄,色纯度好,是一种纯正的蓝光.当吡唑啉环3位引入给电子基时,化合物则具有很高的荧光量子产率,可制得具有高热稳定性的空穴传输蓝光发光材料[4-6]和荧光探针[7].它还可以将吸收的不可见的紫外光转变为蓝色的可见光反射出来,从而增加了光线的反射率,使被其处理过的物体白度和光泽提高,所以吡唑啉又被做为荧光增白剂和荧光染料[8,9]进行广泛地应用.     

Zinc(II) complex immobilized on amine functionalized silica gel: a novel,highly efficient and recyclable catalyst for multicomponent click synthesis of 1,4-disubstituted 1,2,3-triazoles

We report a highly efficient and recyclable heterogeneous zinc catalytic system via covalent immobilization of 2-hydroxyacetophenone (2-HAP) onto an amine functionalized silica gel followed by metallation with zinc chloride and its catalytic application in three component click synthesis of 1,4-disubstituted 1,2,3-triazoles. The structure of the synthesized organic–inorganic hybrid material (SiO₂@APTES@2HAP-Zn) has been confirmed by various physicochemical characterization techniques, such as solid-state ¹³C CPMAS NMR spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, scanning electron microscopy (SEM), atomic absorption spectroscopy (AAS), energy-dispersive X-ray fluorescence spectroscopy (ED-XRF), and elemental analysis. The newly designed catalyst works under mild reaction conditions and also exhibits excellent performance in terms of good product yield and high turnover number (TON). One of the most important attributes of the present methodology is that the catalyst can be recycled several times without appreciable loss in its activity as proved by FTIR spectroscopy and SEM analysis. Besides, the heterogeneity test also confirms that no leaching of active catalytic species occurs from the silica supported zinc catalyst which confirms its remarkable structural stability under the reaction conditions.     

Unusual Luminescence of Ca8[Al12O24]（WO4）2： Tb^3＋

The luminescence properties of aluminate sodalite Ca8[Al12024](WO4)2 (CAW) undoped and doped with Th^3 are reported and discussed. At room temperature the emission of tetrahedral WO4^2- in CAW showed an abnormally small Stokes shift (9060 cm^-1), which is related to the crystal structure of CAW. A strong absorption band in the excitation spectrum of the Th^3 -activated CAW is ascribed to the absorption of the charge transfer state Th^4 -W^5 , into which the excitation resulted in the efficient emission from the ^5D4 level of Tb^3 , but not from the ^5D3 level.     

Synthesis of-4-((4-trimethylsilyl-1H-1,2,3-triazol-1-yl)methyl)-2H-chromen-2-ones: A novel class of heteroaryl anionic synthon

A one-pot synthesis of some novel anionic scaffolds: the substituted-4-((4-trimethylsilyl-1H-1,2,3-triazol-1-yl)methyl)-2H-chromen-2-one is reported. Reaction of 10 different substituted bromomethylcoumarins with trimethylsilylacetylene and sodium azide in the presence of copper(I) iodide catalyst gave the corresponding heteroaryl conjugates: the substituted-4-((4-trimethylsilyl-1H-1,2,3-triazol-1-yl)methyl)-2H-chromen-2-one in 70–92% yields. The structures of the synthesized compounds have been completely characterized by spectral and elemental analyses. For the first time, the representative single-crystal X-ray structure analysis of 6-methoxy-4-((4-trimethylsilyl-1H-1,2,3-triazol-1-yl)methyl)-2H-chromen-2-one is reported which confirms the formation of anionic synthon which bears the trimethylsilyl-group.     

Intramolecular triarylmethane-triarylmethylium complexes with a naphthalene-1,8-diyl skeleton: isolation, structure, and reactivities of the C--H-bridged carbocations

Isolation and low‐temperature X‐ray analyses of intramolecular triarylmethane–triarylmethylium complexes with a naphthalene‐1,8‐diyl‐type skeleton have been achieved. These bridged cations prefer a C? H localized structure both in solution and in the solid state. The bridging hydrogen undergoes a facile intramolecular 1,5‐hydride shift from one carbon to another in solution. The C? H delocalized geometry is suggested to be the transition‐state structure of the degenerate rearrangement. Charge‐transfer interaction from the triarylmethane to the triarylmethylium units is evident in the electronic spectra. This interaction stabilizes the present cations. Low reactivity toward Brønsted acids indicates that these species are not the reaction intermediates in the acid‐assisted long‐bond cleavage of 1,1,2,2‐tetraarylacenaphthene derivatives.     

联有含氮艹/氐的2-吡唑啉化合物的光物理行为

合成了一种在(5)位上联有含氮的2-吡唑啉化合物，研究了该化合物分子所呈现的光敏顺-反异构化现象，并对其机理进行了考察，研究结果表明：具电子转移性质的该化合物顺-反异构化反应速率强烈的依赖于溶剂的极性。同时，光敏异构化还导致了该吡唑啉化合物荧光发射强度随光照时间而增大的有趣结果。     

A series of poly[N-(2-hydroxypropyl)methacrylamide] copolymers with anthracene-derived fluorophores showing aggregation-induced emission properties for bioimaging

A series of new poly[N-(2-hydroxypropyl)methacrylamide]-based amphiphilic copolymers were synthesized through a radical copolymerization of a monomeric/hydrophobic fluorophore possessing aggregation-induced emission (AIE) property with N-(2-hydroxypropyl)methacrylamide. Photophysical properties were investigated using UV-Vis absorbance and fluorescence spectrophotometry. Influences of the polymer structures with different molar ratios of the AIE fluorophores on their photophysical properties were studied. Results show that the AIE fluorophores aggregate in the cores of the micelles formed from the amphiphilic random copolymers and polymers with more hydrophobic AIE fluorophores facilitate stronger aggregations of the AIE segments to obtain higher quantum efficiencies. The polymers reported herein have good water solubility, enabling the application of hydrophobic AIE materials in biological conditions. The polymers were endocytosed by two experimental cell lines, human brain glioblastoma U87MG cells and human esophagus premalignant CP-A, with a distribution into the cytoplasm. The polymers are non-cytotoxic to the two cell lines at a polymer concentration of 1 mg/mL.     

Straightforward Access to Water‐Soluble Unsymmetrical Sulfoxanthene Dyes: Application to the Preparation of Far‐Red Fluorescent Dyes with Large Stokes’ Shifts

An efficient synthesis of water‐soluble unsymmetrical sulforhodamine/sulforhodol fluorophores containing a single julolidine fragment is presented. Owing to their valuable spectral properties in aqueous buffers, these dyes, especially those bearing a free aniline or phenol moiety, are valuable components of fluorogenic probes for a variety of biosensing applications. A further extension of this synthetic methodology to unusual phenols, namely 7‐N,N‐dialkylamino‐4‐hydroxy coumarins has enabled us to provide a new family water‐soluble dyes of large Stokes’ shift with far‐red spectral features.