Turn-on colorimetric sensing of fluoride ions by a cationic triarylborane bearing benzothiazolium

Large Stokes shift benzothiazolium cyanine dyes with improved intramolecular charge transfer (ICT) for cell imaging applications

Intramolecular Charge Transfer (ICT) is a crucial photophysical phenomenon that can be used to improve the Stokes' shift in fluorescent dyes. The introduction of molecular asymmetry is a promising approach to mitigate significant drawbacks of the symmetric cyanine dyes due to their narrow Stokes' shifts (Δλ < 20 nm). In this feature article, we discuss recent progress towards improving the Stokes' shift (Δλ > 100 nm) in benzothiazolium-based fluorophore systems via efficient ICT and recent discoveries related to potentially useful live cell imaging applications of these asymmetric cyanine dyes. This article explores three interesting asymmetric benzothiazolium dye designs (D-π-A, π-A and D-π-2A) in detail while discussing their optical properties. The key advantage of these probes is the synthetic tunability of the probe's photophysical properties and cellular selectivity by simply modifying the donor (D) or the acceptor (A) group in the structure. These new asymmetric ICT fluorophore systems exhibit large Stokes' shifts, high biocompatibility, wash-free staining, red to NIR emission and facile excitation with commercially available laser wavelengths.

Coumarin based thiosemicarbazones as effective chemosensors for fluoride ion detection

Anion sensing have attained immense importance as these charged ions are prevailing in agriculture industry and in heavy industry and therefore in the environment around us, chemosensors are commencing to claim several applications as their role is being better perceived day by day. In the current study, coumarin based thiosemicarbazone R-1 (phenyl moiety) and R-2 (benzyl moiety) were synthesized. It was observed that there were variations in the sensing patterns of compound bearing benzyl group, as compared to the simple phenyl group bearing receptor. Different techniques were used to confirm the interaction of coumarin based receptors with anions. These techniques included naked-eye test, UV-visible, 1H NMR, and fluorescence spectroscopic techniques. The synthesized receptors showed selectivity for fluoride ions. Benesi-Hildebrand equation was employed for determining the detection limits and binding constants values. The synthesized receptors were employed as efficient chemosensors in real life samples and satisfactory results were obtained.

Squeezing fluoride out of water with a neutral bidentate antimony(V) Lewis acid

Because of hydration, fluoride ions in water typically elude complexation by neutral Lewis acids. Here, we show how this limitation can be overcome with a bidentate Lewis acid containing two antimony(V) centers. This derivative (2) is obtained by the simple reaction of 4,5-bis(diphenylstibino)-9,9-dimethylxanthene (1) with two equivalents of 3,4,5,6-tetrachlorobenzoquinone (o-chloranil). It features two square-pyramidal stiborane units oriented in a face-to-face fashion. Titration experiments show that this new bidentate Lewis acid binds fluoride in aqueous solutions containing 95% water with a binding constant (K) of 700±30 M(-1). The structure of the fluoride adduct confirms fluoride anion chelation between the two antimony centers.

Truxene-cored π-expanded triarylborane dyes as single- and two-photon fluorescent probes for fluoride

Two triarylboranes were synthesized and they exhibited high selectivity and sensitivity to fluoride as both single-photon and two-photon fluorescent probes.