Substituent position effect on the properties of new unsymmetrical isomeric diarylethenes having a chlorine atom

Coevolving stability and activity of LsCR by a single point mutation and constructing neat substrate bioreaction system

Carbonyl reductase (CR)-catalyzed bioreduction in the organic phase and the neat substrate reaction system is a lasting challenge, placing higher requirements on the performance of enzymes. Protein engineering is an effective method to enhance the properties of enzymes for industrial applications. In the present work, a single point mutation E145A on our previously constructed CR mutant LsCR_M3 , coevolved thermostability, and activity. Compared with LsCR_M3 , the catalytic efficiency k_cat /K_M of LsCR_M3 -E145A (LsCR_M4 ) was increased from 6.6 to 21.9 s^-1  mM^-1 . Moreover, E145A prolonged the half-life t_1/2 at 40°C from 4.1 to 117 h, T m ${T}_{m}$ was increased by 5°C, T 50 30 ${T}_{50}^{30}$ was increased by 14.6°C, and T_opt was increased by 15°C. Only 1 g/L of lyophilized Escherichia coli cells expressing LsCR_M4 completely reduced up to 600 g/L 2-chloro-1-(3,4-difluorophenyl)ethanone (CFPO) within 13 h at 45°C, yielding the corresponding (1S)-2-chloro-1-(3,4-difluorophenyl)ethanol ((S)-CFPL) in 99.5% ee_P , with a space-time yield of 1.0 kg/L d, the substrate to catalyst ratios (S/C) of 600 g/g. Compared with LsCR_M3 , the substrate loading was increased by 50%, with the S/C increased by 14 times. Compared with LsCR_WT , the substrate loading was increased by 6.5 times. In contrast, LsCR_M4 completely converted 600 g/L CFPO within 12 h in the neat substrate bioreaction system.

A turn-on fluorescence sensor for the highly selective detection of Al3+ based on diarylethene and its application on test strips

A novel fluorescent sensor, 1O, based on photochromic diarylethene with a 2-hydroxybenzhydrazide unit was designed and synthesized and can be used to recognize Al³⁺ in methanol (2.0 × 10⁻⁵ mol L⁻¹).

Structure and photochromism of 1-[2-methyl-5-phenyl-3-thienyl]-2-[2-methyl-5-(4-chlorophenyl)-3-thienyl]3,3,4,4,5,5-hexafluorocyclopent-1-ene, C27H16ClF6S2

C27H16ClF6S2, monclinic, P21/c (no. 14), a = 24.1193(5) Å, b = 9.2419(2) Å, c = 10.8343(2) Å, β = 96.1260(10)°, V = 2401.26(8) Å3, Z = 4, Rgt(F) = 0.0292, wRref(F2) = 0.0878, T = 100(2) K.

An efficient and sensitive chemosensor based on salicylhydrazide for naked-eye and fluorescent detection of Zn2

We reported here the synthesis of a diarylethene with a 2,4-dihydroxybenzoyl hydrazine moiety (1O) for Zn2+ recognition. The compound is easy to prepare with a high yield up to 85%. Compound 1O can act as a highly selective and specific fluorescent sensor for Zn2+ without interference by other common metal ions. The LOD for Zn2+ detection was determined to be 1.28 × 10-6 mol L-1. Meanwhile, 1O can be used as a naked-eye detector for the Zn2+ ion with an obvious color change from colorless to olive. Based on the fluorescent properties of 1O, we constructed a logic circuit with four inputs of the combinational stimuli of UV/vis light and Zn2+/EDTA, and one output of fluorescence intensity.

Photodegradative fate and potential phototoxic products of bromocarbazoles and chlorocarbazoles in water

Bromocarbazoles and chlorocarbazoles are emerging environmental contaminants that have been reported to be persistent and possessing dioxin-like toxicity; however, their photodegradative fate in water is unknown. The photodegradation of 3-bromocarbazole, 3-chlorocarbazole, and 3,6-dichlorocarbazole was determined in ultrapure water. They proceeded by direct photolysis and followed first-order kinetics. The rate constants (k) were 0.4838, 0.3454, and 0.4422 h^-1 corresponding to half-lives (t _1/2) 1.81, 2.01, and 1.62, while the quantum yields (Ф) were 0.232, 0.180, and 0.295 respectively. The maximum wavelengths of absorption (λ _max) were in the near ultraviolet region (295, 296, 299, and 301 nm) implying these compounds are likely to degrade slowly under sunlight in natural aquatic environment. The molar extinction coefficients (ε) determined in acetonitrile were 18,573, 17,028, 13,385, and 14,010 L mol^-1 cm^-1, respectively, the latter being 3,6-dibromocarbazole. A bathochromic shift was observed with halogen addition on their respective mono-substituted congeners. Bromocarbazoles were observed to degrade faster in water than chlorocarbazoles. In addition, photodegradation was estimated to proceed faster in summer than in winter, in natural water system at 50° N latitude. In the absence of light, hydrolytic degradation occurred but proceeded very slowly. Hexahydroxybenzene and trihydroxycarbazole were positively identified as the likely photoproducts with the former being a known toxic compound. Dehalogenation, oxidative cleavage, hydroxylation, and hydrolysis are suggested as the major photodegradation mechanisms in water, yielding phototoxic products that may be of enhanced toxicity than the parent compounds.

Structure and photochromism of 1,2-bis[2-methyl-5-(2-chlorophenyl)-3-thienyl]-3,3,4,4,5,5-hexafluorocyclopent-1-ene, C27H16Cl2F6S2

C27H16Cl2F6S2, triclinic, P1̅ (no. 2), a = 8.3612(18) Å, b = 11.8991(7) Å, c = 13.3979(7) Å, α = 94.667(3)°, β = 99.927(3)°, γ = 105.882(3)°, V = 1251.21(12) Å3, Z = 2, R gt(F) = 0.0441, wR ref(F 2) = 0.1345, T = 100(2) K.

A multi-addressable diarylethene for the selective detection of Al3+ and the construction of a logic circuit

A multi-addressable diarylethene was designed and synthesized, which not only acted as a fluorescent sensor for Al³⁺ with high selectivity, but was also used to construct a combinational logic circuit.

A highly sensitive fluorescent sensor for Al3+and Zn2+based on a diarylethene salicylhydrazide Schiff base derivative and its bioimaging in live cells

A new photochromic diarylethene based sensor with a salicylhydrazide Schiff base displayed a dual-mode with a “turn on” fluorescence response and color changes upon addition of Al³⁺or Zn²⁺.

A diarylethene-based fluorescent chemosensor for the sequential recognition of Fe3+ and cysteine

A new fluorescent chemosensor based on a diarylethene was designed and synthesized for sequential recognition of Fe³⁺ and cysteine.

Alcohols at the aqueous surface: chain length and isomer effects

Alcohol isomers at the water–vapor interface were studied to determine free energies of adsorption, surface concentrations and enrichment factors.

A highly selective fluorescent sensor for Al3+ based on a new diarylethene with a 3-hydroxy-2-naphthohydrazide unit

A novel diarylethene with a 3-hydroxy-2-naphthohydrazide unit was synthesized. It exhibited multi-responsive properties when triggered by lights, base/acid and metal ions. Moreover, the diarylethene could be used as a fluorescent sensor for Al³⁺.

Highly sensitive fluorescent sensor for Mg2+ and Ca2+ based on a multi-addressable diarylethene

A new photochromic diarylethene bearing 8-aminoquinoline unit was designed and synthesized, and the multi-addressable behaviors were investigated. It was highly sensitive towards Mg²⁺ and Ca²⁺ with different fluorescence emission and color change.

A new multi-addressable molecular switch based on a photochromic diarylethene with a 6-aryl[1,2-c]quinazoline unit

A novel diarylethene with a 6-aryl[1,2-c]quinazoline unit has been synthesized via a nucleophilic reaction. Its photochromism and fluorescence exhibited multi-addressable behaviors by the stimulation of both light irradiation and acid/base. Addition of trifluoroacetic acid to the solution of the diarylethene resulted in notable absorption spectral change, and the protonated form also possessed excellent photochromic properties. Meanwhile, its emission intensity was enhanced remarkably and the emission peak redshifted with a notable color change from dark blue to bright green. The changes could be recovered to the initial state by neutralizing with triethylamine. Consequently, a logic circuit was constructed with the diarylethene by using the fluorescence intensity at 482nm as output and acid/base as inputs.

Surface behavior of amphiphiles in aqueous solution: a comparison between different pentanol isomers

Molecular-level understanding of concentration-dependent changes in the surface structure of different amphiphilic isomers at the water–vapor interface was gained by molecular dynamics (MD) simulation and X-ray photoelectron spectroscopy (XPS).

Multi-responsive photochromism of a new diarylethene with a salicylaldehyde group

A new photochromic diarylethene with a salicylaldehyde group was synthesized and fully characterized. With the stimulation of acid/base and light, the diarylethene showed multi-responsive photochromism. The deprotonated derivative of the diarylethene with salicylaldehyde group, due to the addition of triethylamine into its solution, also showed excellent photochromism with distinguishable color change. And the deprotonated example could recover its original state with trifluoroacetic acid. Furthermore, the processes of photochromism and acidichromism could be effectively modulated with light and chemicals. Cyclic voltammetry tests suggested that triethylamine could significantly decrease band-gaps of both open-ring and closed-ring isomers of the diarylethene.

Synthesis, crystal structure and photochromism of new diarylethenes with a benzene moiety

Three unsymmetrical diarylethenes with both thiophene and benzene moieties were synthesized. Their crystal structures and photochromic features were investigated systematically to elucidate the substituent effects of the terminal phenyl group on photochromism. Computational studies were performed to provide further insight into their frontier molecular orbitals and spatial distributions of electronic density. Each compound exhibited favorable photochromism in hexane and functioned as notable fluorescent photo-switches with fluorescence quenching efficiency of ∼96% induced by the intensity change of UV/vis light. Among the three diarylethenes, the cyano group on the terminal phenyl group significantly decreased the distance of the two reactive carbon atoms and strengthened the intermolecular hydrogen bond stacking interactions, resulting in improved stability in crystal state. Furthermore, it exhibited a red-shifted absorption maximum, an enhanced molar absorption coefficient, cyclization quantum yield, and fluorescence quantum yield in solution.

The effect of the formyl group position upon asymmetric isomeric diarylethenes bearing a naphthalene moiety

Three new isomeric asymmetric diarylethenes with a naphthyl moiety and a formyl group at the para, meta or ortho position of the terminal benzene ring were synthesized. Their photochromism, fluorescent-switch, and electrochemical properties were investigated. Among these diarylethenes, the one with a formyl group at the ortho position of benzene displayed the largest molar absorption coefficients and fluorescence quantum yield. The cyclization quantum yields of these compounds increased in the order of para < ortho < meta, whereas their cycloreversion quantum yields decreased in the order of meta > para > ortho. Additionally, all of these diarylethenes functioned as effective fluorescent switches in both solution and PMMA films. Cyclic voltammograms proved that the formyl group and its position could effectively modulate the electrochemical behaviors of these diarylethene derivatives.