Host–guest complexation of a fluorescent and electrochemical chemsensor for fluoride anion

Zinc(ii), copper(ii) and cadmium(ii) complexes as fluorescent chemosensors for cations

The fluorescence chemosensing behavior of Zn(ii), Cu(ii), and Cd(ii) based complexes toward cations has been described. Cation detection via conventional mechanisms, metal-metal exchange and chemodosimetric approaches along with the importance of metal ions and the scope, significance, and challenges with regard to the detection of cations by metal complex based probes will be discussed in detail. The fundamentals of photophysical behavior and mechanisms involved in the fluorescence detection of analytes will also be described. This article provides a detailed overview of Zn(ii), Cu(ii), and Cd(ii) based complexes as fluorescent probes for cations, together with essential discussions pertaining to detection mechanisms.

Ferrocene-Containing Acylhydrazone Receptors: Synthesis, Structures and Electrochemical Anion Recognition Characteristics

Ferrocene-containing redox receptors bearing the 2-(quinolin-8-yloxy)acetohydrazide (qa) moiety on one arm, [Fe(Cpqa)Cp], or two arms, [Fe(Cpqa)2], have been synthesised and the X-ray crystal structure of [Fe(Cpqa)2] determined. [Fe(Cpqa)2] can sense H2PO−4 both electrochemically and selectively even in the presence of a large excess of Cl− and ClO−4.

Highly selective fluorescence sensors for the fluoride anion based on carboxylate-bridged diiron complexes

The diiron–sulfur clusters bearing urea and anthracene units showed rapid and selective recognition for the fluoride ion.

A diarylethene-derived probe for colorimetric detection of CN−and highly selective fluorescent recognition of I−

A new photochromic diarylethene with 2-hydrazinobenzothiazole was synthesized, and its multi-controllable switching behavior specially interacting with light, CN⁻and I⁻was investigated systematically.

Crystal structure of 1,1-di-acetyl-ferrocene dihydrazone

The title compound, [Fe(C₇H₉N₂)₂], crystallizes with two crystallographically independent mol­ecules in the unit cell. These represent the chiral atropoisomers distinguished by the mutual arrangement of the two acet­yl–hydrazone groups with a cis conformation of the C=N bonds. The two cyclo­penta­dienyl (Cp) rings are planar and nearly parallel, the tilt between the two rings being 3.16 (16)° [4.40 (18)° for the second independent mol­ecule]. The conformation of the Cp rings is close to eclipsed, the twist angle being 0.1 (2)° [3.3 (2)°]. The two acet­yl–hydrazone substituents are also planar and are inclined at 13.99 (15)/9.17 (16)° [6.83 (17)/14.59 (15)°] relative to the Cp rings. The Fe—C bond lengths range from 2.035 (3) to 2.065 (2) Å, with an average of 2.050 (3) Å [2.036 (3) to 2.069 (2), average 2.046 (3) Å], which agrees well with those reported for most ferrocene derivatives. In the crystal, the mol­ecules form dimers via two strong N—H⋯N hydrogen bonds. The dimers are linked into a three-dimensional framework by weak N—H⋯N hydrogen bonds.

Synthesis and characterization of bis[N'-(4-carboxybenzylidene)]-pyridine-2,6-dicarbohydrazide: colorimetric and fluorometric modulation in presence of F- ions

A novel organic compound bis[N'-(4-carboxybenzylidene)]-pyridine-2,6-dicarbohydrazide (L) was synthesized and characterized using spectroscopic and X-ray diffraction techniques. Tetrabutyl ammonium halides [(Bu)4N(+)X(-)] X = F, Cl, Br and I were allowed to react separately with a solution of L in DMSO (1 × 10(-5)M). The solution of L turned to shining yellow colour in the presence of F(-) ion only. The binding properties have been studied using absorption, emission and (1)H NMR titrations. Theoretical studies on compound L and compound L+X(-) (X = F, Cl and Br) in DMSO medium were carried out using density functional theory (DFT) at the B3LYP/6-31 G(d,p)/6-31 G+(d,p) level. The theoretical calculations agreed to the experimental results.

A fluorescent fluoride ion probe based on a self-organized ensemble of 5-hydroxyflavone-Al(III) complex

In the presence of Al(III) ions, 5-hydroxyflavone (5HF) through a complexation reaction in MeOH, shows dual fluorescence, characterized by a newly developed peak at 554nm upon excitation at 363nm. In this communication, the subsequent ligand exchange reaction of the complex with fluoride ion causing a fluorescence enhancement followed by a decrease in fluorescence intensity involving an intermediate mechanistic pathway, delivering a quantitative estimation route for fluoride ion in the concentration range from 5x10(-5) to 7x10(-4)M, has been reported. The ligand exchange reaction, without interference from other common anions, has been investigated by UV-vis and fluorescence spectroscopies combined with the AM1 semi-empirical self-consistent field quantum chemical calculations within UHF formalism in their ground state.

Photophysical and anion sensing properties of platinum(ii) terpyridyl complexes with phenolic ethynyl ligands

A series of platinum(II) terpyridyl complexes with phenolic ethynyl ligands have been synthesized and characterized. Their photophysical and sensing properties towards anions such as fluoride, acetate and dihydrogenphosphate have been investigated. These complexes show a colorimetric response and fluorescence quenching in the presence of anions including fluoride, acetate and dihydrogenphosphate, and selective sensing towards fluoride in some cases. The sensing mechanism has been investigated by spectrophotometric and 1H NMR titration.

A Self-Organized Ensemble of Fluorescent 3-Hydroxyflavone-Al (III) Complex as Sensor for Fluoride and Acetate Ions

Aluminum chloride addition results in a self-organized TURN-ON fluorescence of 3-hydroxyflavone (3HF) by a complexation reaction in MeOH and subsequent ligand exchange reaction with fluoride or acetate ions causes a fluorescence TURN-OFF of this complex, delivering a quantitative estimation route for fluoride and acetate ions. The ternary complex of 3HF with Al (III), a hard acid provides for a sensitive signalling system for fluoride ion, a hard base in the concentration range from 6 muM to 50 mM by a concerted co-ordination of fluoride ion involving an intermediate mechanistic pathway, while the complex is sensitive to acetate addition between 0-68 muM. The ligand exchange reaction of Al (3HF)(2) complex by fluoride or acetate ion, without interference from other common anions, has been investigated by UV-visible and fluorescence spetroscopies. The structure of the in-situ intermediate isolated at higher Al (3HF)(2) complex and acetate concentrations was inferred from the FT-IR spectrum and ESI-MS of the sample.

Ferrocene-Based Ureas as Multisignaling Receptors for Anions

The synthesis of structurally new types of ferrocene-based ureas, in which the ferrocene moiety is simultaneously attached to two urea groups, have been prepared directly from 1,1'-bis(isocyanato)ferrocene 1. Homoditopic receptors 2a-e show spectral and electrochemical anion-sensing action: they display a selective downfield shift of the urea protons and a cathodic shift of the ferrocene/ferrocinium redox couple with hydrogen phosphate and fluoride anions. In addition, receptor 2d based on an unprecedent tetraaza[9]ferrocenophane architecture, shows spectral, electrochemical, and selective fluorescent responses to fluoride anion.

A highly selective chromo- and fluorogenic dual responding fluoride sensor: naked-eye detection of F- ion in natural water via a test paper

A highly selective and sensitive chromogenic and fluorogenic dual signal responding fluoride-sensor 1, comprising a Ru-bipy fluorophore (bipy = 2,2'-bipyridine) and a 2,4-dinitrophenylhydrazone chromophore was prepared and spectroscopically characterized. Uv-vis titrations with F- revealed the appearance of a new intense absorption band centered at about 580 nm which was accompanied by a dramatic change in color from yellow to magenta, with the association constant logK being 6.71 +/- 0.04. Fluorescence spectra showed that upon addition of F-, the emission intensities enhanced significantly without any change in the excited and emission wavelengths, suggesting a potential photoinduced electronic transfer (PET) signaling transduction mechanism. An easy-to-prepare test paper which was obtained by putting a filter paper into an acetonitrile solution of 1, can detect F- in aqueous media, indicating the potential application for detecting F- in natural aqueous environments without any spectroscopic instrumentation. Spectroscopic titrations of the free ligand were also studied for comparison.