Dual recognition of Al3+ and Zn2+ ions by a novel probe based on diarylethene and its application

Novel pyrazoline and pyrazole "turn on" fluorescent sensors selective for Zn2+/Cd2+ at λem 480 nm and Fe3+/Fe2+ at λem 465 nm in MeCN

A small series of simple pyrazoline and pyrazole based sensors, all derived from the same chalcone precursors, were synthesised, characterised and screened for their fluorescence "turn on" properties in the presence of multiple metals. Pyrazole 8 displayed an excellent fluorescence profile with approx. 20× fold increase in λem 480 nm with Zn2+ compared to a 2.5× fold increase with Cd2+. Pyrazole 9 displayed a 30× fold increase at λem 465 nm for Fe3+ compared to Fe2+ with a Fe3+ limit of detection of 0.025 μM. The corresponding pyrazolines displayed contrasting properties with important implications for future pyrazoline and pyrazole sensor design.

A Colorimetric Distinct Color Change Cu(II) 4-{[1-(2,5-dihydroxyphenyl)ethylidene]amino}-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one Chemosensor and its Application as a Paper Test Kit

In the current research work "4-{[1-(2,5-dihydroxyphenyl)ethylidene]amino}-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one" chemosensor (C1) synthesized by condensation reaction using "4-amino-1,2-dihydro-1,5-dimethyl-2-phenylpyrazol-3-one" and "2,5-dihydroxy actophenone" was used as the effective sensor of metal ion. The C1 shows absorption peak at 326 nm due to the C = C bond (π-π* transition), while the absorption peak at 364 nm is caused by the C = O bond (n-π* transition). In the presence of copper, C1 only demonstrated a redshift in absorption peak from 364 to 425 nm. Even in the presence of other competing metal ions, the hypsochromic shift of the absorption band and the quenching of the fluorescence emission intensity were different for detecting Cu²⁺, in CH₃OH-H₂O (v/v = 6:4). The capacity of the C1 to bind with Cu²⁺ was further proved using DFT simulations. The complex C1 + Cu²⁺ has a HOMO-LUMO energy gap of 2.8002 eV, which is lesser than C1 (2.9991 eV) showing improvement in the stability of the C1 + Cu²⁺ complex. Using the Benesi-Hildebrand and Scatchard plots, calculated Kb values were to be 47,340 and 48369 M^-1 respectively, showing the creation of stable complexation between Cu²⁺ and C1 with 1:1 stoichiometry. The limit of detection (LOD) for Cu²⁺ ion was 649 nM. Strip sheets were also built and tested to detect varying amounts of Cu²⁺ in aqueous solution, and their color change suggested that they might be used for on-site Cu²⁺ detection in polluted water.

Achieving Enhanced Photochromic Properties of Diarylethene through Host-Guest Interaction in Aqueous Solution

Diarylethene (DTE) has been widely used in fluorescence probes, molecular logic gates, optical data-storage devices owing to the excellent photochromic property, while constructing high-performance photochromic DTE in aqueous media remains a big challenge. Herein we present several host-guest systems formed between cucurbit[n]uril (CB[n], n=7, 8, 10) and two water-soluble DTE derivatives 1 and 2. It was found that host-guest interactions not only affect the photophysical properties of photochromic guests, but also make great differences on the photoreaction process. Different host-guest binding behaviors also lead to different effects on the photochromic properties of guests. In the presence of CB[n], both 1 and 2 showed enhanced emission and higher fluorescence quenching ratio at photostationary state. Besides, CB[10]⋅1 exhibited faster response rate in cyclization reaction and better photofatigue resistance than free 1 in aqueous solution, while the supramolecular assembly of (CB[8])_n ⋅(2)_n showed slower response rate in both directions of the reversible photoreaction. Besides, the photofatigue resistance of 2 can be greatly improved through binding with CB[7]. Our results suggest that host-guest interactions could be an efficient way to improve photochromic properties of DTE in aqueous solution.

Fluorescent sensor based on triphenylamine for Zn2+ with high selectivity and imaging in living cells

It is of great importance to design a fluorescent sensor with high selectivity, sensitivity and large Stokes shift to zinc detection for environmental water sample and in vivo. Herein, A novel Zn²⁺ fluorescent sensor with larger Stokes shift (110 nm) 1-((5-(4-(diphenylamino)phenyl)pyridine-2-imino)methyl)naphthalene-2-ol (abbr. TPA-PN) was designed and synthesized. In DMF-H₂O (V: V = 1: 1, pH = 7.0) solution, it could achieve high selectivity and sensitivity to Zn²⁺, there was a linear responsive range of 0-20 μM of concentration of Zn²⁺ ions for the sensor, the detection limit was as low as 19.134 nM and the binding constant was calculated to be 3.24 × 10⁴ M^-1. The species of TPA-PN and zinc were clarified at different pH. Besides, the interaction properties and fluorescence mechanism were demonstrated by the species theory, density functional theory (DFT) calculation, ¹H NMR titration, FT-IR and MS. Most importantly, it provided a new real-time, on-site method and showed excellent potential in-vivo imaging ability.

Eu(III)-organic complex as recyclable dual-functional luminescent sensor for simultaneous and quantitative sensing of 2,4,6-trinitrophenol and CrO42- in aqueous solution

A novel metal-organic complex (MOC) {[Eu₂(HL)₂(H₂O)₄]·3H₂O}_n (1) (H₄L = 3,3',5,5'-azoxybenzenetetracarboxylic acid) has been successfully constructed, which exhibits a fascinating 2D bilayer network with the 1D open channels and has excellent water, pH and thermal stabilities. Luminescence studies reveal that 1 can detect TNP and CrO₄^2- ions with high selectivity and sensitivity in aqueous solution, even if there are related interfering substances. And the mechanisms of luminescence recognitions are discussed on the basis of experiments and theoretical calculations. Furthermore, 1 shows excellent photostability and can be repeatedly used in the above two detection systems. Most importantly, 1 can detect TNP and CrO₄^2- concentration with a good recovery rate in practical application. Therefore, 1 should be a potential dual-functional luminescent sensor for reliable sensing of TNP and CrO₄^2- in the field.