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Fluorescent single crystals that respond to multiple external stimuli are of great interest in molecular machines, sensors, and displays. The integration of photo‐ or acid‐induced fluorescence enhancement and bending in one organic crystal, however, has not been reported yet. Herein, we report the interesting plastic photomechanical bending and switching on of the fluorescence of an azine crystal in a single‐crystal transformation, due to extended π‐conjugation and molecular slippage. Moreover, the fluorescent plastic bending driven by multiple volatile acid vapors was firstly observed, and attributed to the synergistic effect of push–pull electronic structure and hydrogen bonding. The single crystal also shows high elasticity under external force. In addition, reversible fluorescence switching can be triggered by grinding and solvent fuming, as well as by the adsorption and desorption of HCl vapor. The integration of plastic, elastic bending and switch‐on fluorescence into one single crystal provides a new strategy for next‐generation smart materials. [ABSTRACT FROM AUTHOR]

Dipyrrolydiketones BF2 complex was synthesized and characterized by NMR, HRMS, and single crystal diffraction. In non-polar environment, this BF2 containing dye emitted bright blue-green fluorescence. No significant spectra shift was observed both in absorption and emission spectra, which indicates the insensitivity of absorption/emission toward environment. The alkyl substituted pyrrole rings lead to its highly emission character in solid state by enhancing the distance between dye molecules. Absolute quantum yields were determined to be 0.51–0.78/0.36 in selected organic medium and solid state, respectively. The emission dynamics was investigated by fluorescence lifetime and both monoexponential and bi-exponential decay was observed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chemosensor was configured by attaching responsive group, diaminomaleonitrile, to BODIPY scaffold. • Cu2+ can be selectively recognized on a 2-s time-scale. • The recognition mechanism is based on the Cu2+ induced intramolecular oxidative cyclization of γ-aminoimine. • The absolute fluorescence quantum yield of BD + Cu2+ is determined to be 98%, attributing to the formation of dicarbonitrile substituted imidazole ring. A highly fluorescent Cu2+-responsive sensor, 2-amino-3-(BODIPYmethyleneamino)maleonitrile (BD) was constructed by attaching diaminomaleonitrile to a BODIPY scaffold. Cu2+ can be selectively recognized on a 2-s time-scale by way of fluorescence emission. When Cu2+ and BD coexist in solution, typical BODIPY emission was observed and the emission intensity could be increased to 334 times that of the blank dye solution. The mechanism of fluorescence increase is based on the generation of highly fluorescent species by Cu2+-triggered oxidative cyclization of the attached diaminomaleonitrile. The absolute fluorescence quantum yield (AFQY) of the cyclization product is 98% determined by integrating sphere. The highly emissive character can be attributed to the imidazole ring and dicarbonitrile on the BODIPY scaffold. It surpasses the meso -phenyl substituted analogue in AFQY and detection limits (DL). The specific Cu2+ recognition behavior was also validated in Hela cells with high-contrast fluorescence images. [ABSTRACT FROM AUTHOR]

A heavy metals sensor (2-N,N-bis(pyridin-2-ylmethyl)methanamine-BODIPY, DB) for the recognition of Pb2+, Ba2+, Cr2+, Cd2+, Hg2+, Sn2+, and Zn2+ was developed by anchoring (bis(pyridin-2-ylmethyl)amine) DPA unit to the BODIPY framework. It exhibited excellent sensitivity and selectivity against other competent metal ions. The stoichiometry of DB and metal ions were determined to be 1:1. The limit of detection of DB toward Pb2+, Ba2+, Cr2+, Cd2+, Hg2+, Sn2+, and Zn2+ was ranged from 60.07 to 89.37 nM. Photo induced transfer (PET) leads to the weak emission of BODIPY unit. When metal ions anchored with DPA, PET was blocked due to the weak electron donating ability of N in DPA to BODIPY and the highly emissive character of BODIPY was recovered, establishing a fluorescence switch. [ABSTRACT FROM AUTHOR]

A fluorine-boron (F-B) containing dye was configured and routinely characterized by nuclear magnetic resonance (NMR) and mass spectrometry (MS) technology. The absorption and emission behavior were investigated in selected solvent with different polarity. Both in chloroform and in solid powder state, it is highly emissive. The absolute fluorescence quantum yield was determined to be 0.60. The coordination lock of B atom prevents the free rotation of two fragment of the dye and limited the nonradiation transition, thus leading to the fluorescence emission character. In addition, significant Stoke's shift (∼190 nm) was observed. Similar emission maximum in solution and solid shows that the emission behavior is insensitive to molecular aggregation behavior. In all the case, the emission colors were demonstrated by Commission internationale de l'éclairage (CIE) chromaticity system. [ABSTRACT FROM AUTHOR]

In this contribution, the emission response of 4-(2,5-dimethylthiophen-3-yl)-2-(2-hydroxy- phenyl)benzothiazole (THBT) was investigated in detail. The experimental shows that Zn2+ could induce fluorescence increasing in tetrahydrofuran (THF). Especially, the quenched emission of THBT was significantly enhanced with 0.76 quantum yield. Due to the coordination of Zn2+, the excited state intramolecular proto transfer (ESIPT) was inhibited and leads to emission quenching correspondingly. The strong emission could ascribe to the Zn-THBT complex. As well, the addition of BF3·Et2O also could form fluorine-boron complex and inhibit ESIPT effect. Additionally, the BF complex is also a strong blue emitter. Therefore, strong blue emission upon BF3·Et2O addition to THBT in dioxane was found. The possible coordinating mechanisms of THBT coordinate with Zn2+ and BF3·Et2O were given. [ABSTRACT FROM AUTHOR]

A novel BODIPY-based dye with highly emissive character was configured by Sonogashira coupling and routinely characterized by NMR and MS technology. The emission of dye was investigated in solution/film/solid and shows intensive emission. In solution, the emission peak appeared around 510 nm with little influence by the polar environment. The terthiophene plays an effective antenna effect, harvesting the light and transferring the energy to BODIPY. The pseudo Stoke's shift enlarged to ∼170 nm in solution. In film, the emission peak shifted to 563 nm in polycarbonate matrix. And it shifted further to 585 nm in solid due to the highly twisted structure, which avoided closely regular-tight packing. The dye rendered an intense fluorescence, good optothermal stability, and high fluorescence quantum yield (0.55). The solid emission showed highly red emission with Commission Internationale de L'Eclairage (CIE) coordinates of (X = 0.69, Y = 0.31). Thus, the synthesized dye is idea candidate for emitting materials. [ABSTRACT FROM AUTHOR]

In this contribution, the emission response of 4-(2,5-dimethylthiophen-3-yl)-2-(2-hydroxy- phenyl)benzothiazole (THBT) was investigated in detail. The experimental shows that Zn2+ could induce fluorescence increasing in tetrahydrofuran (THF). Especially, the quenched emission of THBT was significantly enhanced with 0.76 quantum yield. Due to the coordination of Zn2+, the excited state intramolecular proto transfer (ESIPT) was inhibited and leads to emission quenching correspondingly. The strong emission could ascribe to the Zn-THBT complex. As well, the addition of BF3·Et2O also could form fluorine-boron complex and inhibit ESIPT effect. Additionally, the BF complex is also a strong blue emitter. Therefore, strong blue emission upon BF3·Et2O addition to THBT in dioxane was found. The possible coordinating mechanisms of THBT coordinate with Zn2+ and BF3·Et2O were given. [ABSTRACT FROM AUTHOR]

A BODIPY based with perimidine attached derivative was developed and characterized. It was efficiently synthesized by condensation between aldehyde sited at β-position of BODIPY and 1,8-diamino-naphthalene. Owing to the electron-donor effect of N in heterocycle, emission was quenched completely. Upon protonation of N, the solution exhibited dramatic emission enhancement with emission peak locating at 510 nm, which is estimated to be 275-fold of initial emission. With OH−addition, it could be reverted to the emission to non-emisison state again and establish a fluorescence switch. The underlying mechanism of fluorescence “off-on” is based on the intramolecular PET, which was attested by quantum chemistry calculation approach. [ABSTRACT FROM PUBLISHER]

Detailed absorption and emission behavior were investigated for a sexthiophene molecule in solution, film, and solid. Only strong polarity solvent could result a notable influence on the quench of its fluorescence. In weak and medium polar environment, including in polymer matrix, highly emissive behavior was maintained and exhibit large Stokes shift. More important is its highly emissive in solid state due to the twisted molecular conformation. However, the bandwidth of solid emission (FWHM: 2149 cm−1) is similar to that of solution emission. The calculated frontier orbital based on TDDFT theory uncovered the underlying signal mechanism furtherly. [ABSTRACT FROM AUTHOR]

In this contribution, a dye (THBT) with 2,5-dimethylthiophene substituted to 2-(2-hydroxyphenyl)benzothiazole was synthesized and characterized by NMR and mass spectroscopic techniques. Its emission behavior in various solvents was investigated and obvious negative solvatochromism was observed. The emission maximum ofTHBTvaried from deep blue (425 nm) in DMSO to orange (550 nm) in chloroform. It is also highly emissive in polycarbonate film and solid powder with the emission peaks 546 and 554 nm, respectively. The ESIPT effect, together with the relaxation of free rotation of thiophene in the excited states, shifted the solid emission 34 nm toward longer wavelength furtherly, with respect the 520 nm (green) emission ofHBT. Quantum calculation of frontier molecular orbitals uncovers the underlying mechanism of negative solvatochromism. [ABSTRACT FROM AUTHOR]

The π -conjugate system of a bipyrrole fluorine–boron-based fluorophore was linearly extended by coupling methodology, and the resulting complexes were fully characterized. Various substituents linked to the framework of the bipyrrole fluorine–boron complexes by ethynyl spacers not only extended the π -conjugate system but also caused the emission maxima to red-shift by ∼10 nm increments. The emission maxima of these complexes spanned 49 nm, extending from 487 nm (blue-green) to 536 nm (green-yellow). These complexes were highly emissive both in solution and as a solid powder. Triple bonds, along with the substituent effect, can be regarded as ideal for fluorescence modulation. [ABSTRACT FROM AUTHOR]

In this contribution, a new naphthalimide dimer with A- π -D- π -A framework was synthesized efficiently and well characterized. Its spectral properties were investigated. Significant features, such as strong solid and liquid fluorescence, usual large Stokes shift were discussed in terms of its electronic structures. In addition, it is soluble in common organic solvent and stable at ambient conditions. Optimized molecular structure shows the twisted molecular conformation, which leads to its narrow solid emission. Frontier orbital calculation indicates effective excited-state intramolecular charge transfer (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Abstract: Isomers based on the bisindolylmaleimide architecture were reported in this Letter. Introducing hydroxyl to this architecture lead to quenching the fluorescence of bisindolylmaleimide. The fluorescence was recovered with its hydroxyl group esterified. Ester group can be easily transformed to hydroxyl group by hydrolysis reaction. Thus, a toggle-switchable fluorescence, ‘off–on’ cycle can be established on the basis of reversible esterification/hydrolysis reaction. [Copyright &y& Elsevier]

Abstract: A new photochromic compound based on the hexatriene backbone was prepared by one-step coupling. The photochromic backbone, composed of three thiophene ring, undergoes reversible ring-opening and ring-closing photoisomerization reactions when irradiated with ultraviolet and visible light, respectively. It exhibited fatigue resistance and thermally irreversible photochromic properties. The ring-open form exhibits appreciable fluorescence, while quenched by the ring-closed form. [Copyright &y& Elsevier]

A specific Cu2+ sensor, 2-amino-3-(BODIPYmethyleneamino)maleonitrile (BDM), was established by a simple dehydration between BODIPY and diaminomaleonitrile. Cu2+ could be recognized by BDM over other competing metal ions in acetonitrile with distinct fluorescence emission signal response. Upon the addition of Cu2+ to BDM in acetonitrile, the maximum absorption at approximately 530 nm on the longer wavelength side was quenched, and the emission at 530 nm was ignited simultaneously. The fluorescence intensity enhancement could reach a maximum of 204 times the intensity of the BDM blank solution. The fluorescence "off-on" effect is established according to the Cu2+-induced fast intramolecular oxidative cyclization reaction, which could be deduced from the formation of an imidazole ring appended to the cyclization product (2-BODIPY-1 H -imidazole-4,5-dicarbonitrile, BMC). Single-crystal structure analysis of the sensor BDM and cyclization product BMC further demonstrated this oxidative cyclization. Finally, the Cu2+ recognition property of BDM was validated in SiHa cells and living zebrafish. Additionally, the blood-brain barrier of the zebrafish can be penetrated by the BDM dye and the neuron cells in the brain were stained. Unlabelled Image • Intramolecular oxidative cyclization reaction based sensor was established. • Single crystal structure analysis was also demonstrated. • Sensing property was validated in Siha cells and living vertebrate model, zebrafish. [ABSTRACT FROM AUTHOR]