Acetate selective fluorescent turn-on sensors derived using vitamin B6 cofactor pyridoxal-5-phosphate.

Two new Schiff base receptors have been synthesized by condensation of pyridoxal-5-phosphate with 2-aminophenol (L(1)) or aniline (L(2)). In DMSO, the receptors showed both chromogenic and 'turn-on' fluorescence responses selectively in the presence of AcO(-) and F(-). However, in mixed DMSO-H2O medium, the receptors showed AcO(-) selective 'turn-on' fluorescence without any interference from other tested anions including F(-). The detection limit for AcO(-) was found to be 7.37 µM and 22.9 µM using the receptors L(1) and L(2), respectively.

An aqueous friendly chemosensor derived from vitamin B6 cofactor for colorimetric sensing of Cu²âº and fluorescent turn-off sensing of Fe³âº.

Chemosensor L derived from vitamin B6 cofactor pyridoxal-5-phosphate was investigated for the selective detection of Cu(2+) and Fe(3+) in aqueous medium. Sensor L formed a 1:1 complex with Cu(2+) and displays a perceptible color change from colorless to yellow brown with the appearance of a new charge transfer band at ~450 nm. In contrast, the fluorescence of L was quenched selectively in the presence of Fe(3+) without any interference from other metal ions including Cu(2+).

Bioimaging application of a novel anion selective chemosensor derived from vitamin B6 cofactor.

The detection of intracellular fluoride was achieved by a novel Schiff base chemosensor derived from vitamin B6 cofactor (L) using fluorescence imaging technique. The sensor L was synthesized by condensation of pyridoxal phosphate with 2-aminothiophenol. The anion recognition ability of L was explored by UV-Vis and fluorescence methods in DMSO and mixed DMSO-H2O system. The sensor L showed both naked-eye detectable color change from colorless to light green and remarkable fluorescence enhancement at 500 nm in the presence of F(-) and AcO(-). The anion recognition was occurred through the formation of hydrogen bonded complexes between these anions and L, followed by the partial deprotonation of L. The detection limit of L for the analysis of F(-) and AcO(-) was calculated to be 1.88 µM and 9.10 µM, respectively. Finally, the detection of cytoplasmic fluoride was tested using human cancer cell HeLa through fluorescence imaging.

Fluorescence 'turn-on' sensor for F- derived from vitamin B6 cofactor.

A novel vitamin B6 Schiff base analog (L) was synthesized by combining vitamin B6 cofactor pyridoxal with 2-aminophenol. Receptor L displays a color change detectable by the naked-eye from yellow to red in the presence of fluoride and acetate due to the formation of hydrogen bonding host-guest complexes in 1 : 1 stoichiometry. Importantly, receptor L showed fluoride-selective 'turn-on' fluorescent response with a detection limit (3σ) of 7.39 × 10(-8) M.

Spectroscopic and computational study of a naphthalene derivative as colorimetric and fluorescent sensor for bioactive anions.

The anion recognition property of a naphthalene based receptor (L) was investigated by naked-eye, UV-Vis, fluorescence, (1)H NMR and computational methods. The receptor L showed fluoride selective naked-eye detectable colorimetric and UV-Vis spectral changes over other tested anions due to the formation of hydrogen bonding complex in 1:1 stoichiometry and/or deprotonation between fluoride and the receptor. Interestingly, the fluorescence of L was quenched by fluoride but enhanced by acetate.

Naphthalene based colorimetric sensor for bioactive anions: experimental and DFT study.

A simple anion selective colorimetric sensor L has been designed by combining 2-hydroxy-1-naphthaldehyde with 2-aminothiophenol. Sensor L portrayed a necked-eye detectable color change from light green to red upon addition of AcO(-), F(-) and H(2)PO(4)(-) anions in CH(3)CN, where as no significant color change was observed upon addition of other anions such as Cl(-), Br(-), I(-) and HSO(4)(-). Sensor L showed selectivity towards AcO(-) under competitive environment, with a detection limit (3σ/S) down to 1.1×10(-7) M. In addition, the anion sensing ability of L was explored in mixed H(2)O/CH(3)CN (v/v) medium. Further, the nature of interactions between the sensor L and AcO(-) was investigated by (1)H NMR and the probable structure of the L-AcO(-) complex was predicted by B3LYP/6-31G(d,p) method.

Iron(III) selective molecular and supramolecular fluorescent probes.

Iron is one of the most important elements in metabolic processes, being indispensable for all living systems and therefore it is extensively distributed in environmental and biological materials. However, both its deficiency and excess from the normal permissible limit can induce serious disorders. Therefore, several analytical techniques have been adopted for the detection of iron. Among the various techniques used for its detection, the method based on fluorescent sensors has received considerable interest in recent years because of its ability to provide online monitoring of very low concentrations without any pre-treatment of the sample together with the advantages of spatial and temporal resolution. In this article, efforts have been made to review the various molecular and supramolecular fluorescent sensors that have been developed for the selective detection of iron(III).

Studies on molecular structure and tautomerism of a vitamin B6 analog with density functional theory.

This work presents a computational study on the molecular structure and tautomeric equilibria of a novel Schiff base L derived from pyridoxal (PL) and o-phenylenediamine by using the density functional method B3LYP with basis sets 6-31 G(d,p), 6-31++G(d,p), 6-311 G(d,p) and 6-311++G(d,p). The optimized geometrical parameters obtained by B3LYP/6-31 G(d,p) method showed the best agreement with the experimental values. Tautomeric stability study of L inferred that the enolimine form is more stable than its ketoenamine form in both gas phase and solution. However, protonation of the pyridoxal nitrogen atom (LH) have accelerated the formation of ketoenamine form, and therefore, both ketoenamine and enolimine forms could be present in acidic media.

Potentiometric Study of a Benzene-based Tripodal Triamine as Chelator for Zn(II) Ion.

The complexation of a C3-symmetrical tripodal triamine ligand, N1, N3, N5-tris(2-aminoethyl)benzene-1, 3, 5-tricarboxamide (TAT, L) with Zn(II) ion was investigated at an ionic strength of 0.1 M NaClO4 and 25 ± 1 °C in aqueous medium. Formation of complex species [ZnL(H2O)]2+ and [ZnL(OH)]+ were depicted in solution, where the ligand is tri-coordinated through three amine N-atoms and their stability constants were calculated with the HYPERQUAD 2000 computer program. The pKa of the zinc-bound water molecule is 7.84, making the Zn(TAT) complex a viable model of carbonic anhydrase.