A new highly selective “off–on” typical chemosensor of Al3+, 1-((Z)-((E)-(3,5-dichloro-2-hydroxybenzylidene)hydrazono)methyl) naphthalene-2-ol, an experimental and in silico study

Fabrication of a New Coumarin Based Fluorescent "turn-on" Probe for Distinct and Sequential Recognition of Al3+ and F- Along With Its Application in Live Cell Imaging

A new coumarin based fluorescent switch PCEH is fabricated which displays high selective sensing towards Al3+ among other metal cations at physiological pH. On gradual addition of Al3+, PCEH shows a brilliant "turn-on" emission enhancement in MeOH/H2O (4/1, v/v) solution. This new fluorescent switch is proven to be a reversible probe by gradual addition of F- into the PCEH-Al3+ solution. Detection limit as well as binding constant values are calculated to be in the order of 10-9 M and 104 M-1 respectively. We have also explored its potential as a biomarker in the application of live cell imaging using breast cancer cells (MDA-MB-231 cell).

ESIPT-based probes for cations, anions and neutral species: recent progress, multidisciplinary applications and future perspectives

Fluorescent and colourimetric probes for small analytes (cations, anions and neutral molecules) have drawn significant attention in recent years. These probes interact with analytes and induce spectral change due to the variations in the photo-physical properties of the fluorophore/chromophore used. Among several photo-physical mechanisms, ESIPT (excited state intramolecular proton transfer) based probes are more advantageous due to their photo-physical properties viz. solvent polarity effect, large spectral shift with multi-channel fluorescence, high quantum yield etc. In recent years, ESIPT-based probes have shown several promising applications, especially monitoring small analytes in biological samples, smartphone app-assisted heavy metal detection in environmental samples, inkless writing, anti-counterfeiting applications etc. Therefore, this review is dedicated to recently reported ESIPT-based probes for small analytes. We have highlighted the organic units responsible for the ESIPT mechanism, their photo-physical parameters, selectivity and sensitivity properties and recent advances in their applications.

Modulation of aluminum sensing properties of a sulphone group containing chemosensor and its biological applications

A chemosensor with two binding pockets facilitates binding of one metal ion in either of the pockets providing a better chance for the interaction and hence recognition of the cation. We report here a chemosensor, namely 2,2'-(1E)-(5,5'-sulfonylbis(2-hydroxy-5,1-phenylene))bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)dinaphthalen-1-ol (H₄L-naph), for selective sensing of Al³⁺ in DMF- HEPES buffer (1:4, v/v, pH 7.4). It shows almost 100-fold fluorescence enhancement at 532 nm (λ_ex = 482 nm) in the presence of Al³⁺. Its quantum yield and excited state lifetime enhances significantly with the cations. H₄L-naph forms a 1:2 complex with Al³⁺ with an association constant value of 2.18 × 10⁴ M^-2. Fluorescence enhancement may be attributed to CHEFF mechanism and restriction of >CN isomerization. Effect of the presence of naphthyl rings instead phenyl ring of a previously reported probe has resulted shifting of excitation/emission peak towards longer wavelength. The probe has been applied to image Al³⁺ in L6 cells with no significant cytotoxicity.