Design strategies for water-soluble small molecular chromogenic and fluorogenic probes.

Due to the wide range of applications and biological significance, the development of optical probes for silver, gold and platinum ions has been an active research area in the past few years. This tutorial review focuses on the recent contributions concerning the fluorescent or colorimetric sensors for these metal ions, and is organized according to their structural classifications (for Ag+ detection) and unique mechanisms between the sensors and metal ions (for Au3+ and Pt2+ detection).

Recent progress in fluorescent and colorimetric chemosensors for detection of precious metal ions (silver, gold and platinum ions)

New fluorescent chemosensors for metal ions in solution

Flipping the light switch 'on'--the design of sensor molecules that show cation-induced fluorescence enhancement with heavy and transition metal ions.

The UV- and sensor-induced interferences to living systems pose a barrier for in vivo Zn2+ imaging. In this work, an intramolecular charge transfer (ICT) fluorophore of smaller aromatic plane, 4-amino-7-nitro-2,1,3-benzoxadiazole, was adopted to construct visible light excited fluorescent Zn2+ sensor, NBD-TPEA. This sensor demonstrates a visible ICT absorption band, a large Stokes shift, and biocompatibility. It emits weakly (Φ = 0.003) without pH dependence at pH 7.1−10.1, and the λex and λem are 469 (e469 = 2.1 × 104 M−1 cm−1) and 550 nm, respectively. The NBD-TPEA displays distinct selective Zn2+-amplified fluorescence (Φ = 0.046, e469 = 1.4 × 104 M−1 cm−1) with emission shift from 550 to 534 nm, which can be ascribed to the synergic Zn2+ coordination by the outer bis(pyridin-2-ylmethyl)amine (BPA) and 4-amine. The Zn2+ binding ratio of NBD-TPEA is 1:1. By comparison with its analogues NBD-BPA and NBD-PMA, which have no Zn2+ affinity, the outer BPA in NBD-TPEA should be responsible for the Zn2+-induced...

Visible Light Excitable Zn2+ Fluorescent Sensor Derived from an Intramolecular Charge Transfer Fluorophore and Its in Vitro and in Vivo Application

Excellent mercury(II) ion selectivefluoroionophore based on a 3,6,12,15-tetrathia-9-azaheptadecane derivativebearing a nitrobenzoxadiazolyl moiety

A dozen novel fluoroionophores have been synthesized which are polythiazaalkane and polythiaalkane derivatives coupled with an anthracene moiety by methyl, carbonyl, or methylphenylene bridging groups The protonation and metal ion complexation behavior of analogues were examined in 1,4-dioxane−water solutions spectrophotometrically and spectrophotofluorometrically The fluoroionophores, 1, 2, 5, and 6 contain basic nitrogen atoms and quench the fluorescence in the free forms because of photoinduced electron transfer (PET) from a nitrogen atom to a photoexcited anthracene unit The fluorescence was recovered by the protonation on the nitrogen atom The fluorescence intensities of the other fluoroionophores used here were not dependent on the pH of the solution On the complexation of the protonated fluoroionophores 1, 2, 5, and 6 with metal ions under the acidic condition, the fluorescence intensities were decreased by the addition of silver ion selectively Under the same conditions, the other fluoroiono

Silver Ion Selective Fluoroionophores Based on Anthracene-Linked Polythiazaalkane or Polythiaalkane Derivatives.

Cyclic and acyclic dithiamonoaza, tetrathiamonoaza, and tetrathiadiaza analogs of polyethers bearing a hydrazone moiety on nitrogen atom(s) were synthesized. Their acidity constants in 1,4-dioxane–water solution and stability constants of hydrazones derived from dithiamonoaza and tetrathiamonoaza analogs of polyethers for some heavy metal ions in same acidic media were measured spectrophotometrically. Hydrazones of cyclic and acyclic tetrathiamonoaza series had highly Ag+-selective complexability.

Hydrazones Derived from Dithiamonoaza and Tetrathiamonoaza Analogs of Polyethers as Silver Ion Selective Ionophores: Syntheses, Proton-Dissociation Behaviors, and Metal Ion Complexing Properties in 1,4-Dioxane–Water Acidic Solution

Dithiazacrown, tetrathiazacrown, and two tetrathiadiazacrown ether derivatives, bearing a phenyl group on each nitrogen atom at the periphery, were synthesized, and the solvent extractions of some transition metal ions with these compounds were carried out using an H2O–1,2-dichloroethane system. All of the thiazacrown compounds employed exhibited Ag+ selectivity, and formed 1 : 1 : 1 complexes of Ag+ : ligand : laurate ion as a counter anion to be extracted into a 1,2-dichloroethane solution. The extractabilities (extraction constants, Kex) for Ag+ decreased in the order: 7,16-diphenyltetrathia-7,16-diaza-18-crown-6 (3) (log Kex = 1.18 ± 0.13) > 13-phenyltetrathia-13-aza-15-crown-5 (2) (0.75 ± 0.09) > 7-phenyldithia-7-aza-9-crown-3 (1) (−0.47 ± 0.06) > 13,16-diphenyltetrathia-13,16-diaza-18-crown-6 (4) (−0.62 ± 0.16).

Silver Ion Selective Extraction with Dithiaza-, Tetrathiaza-, and Tetrathiadiazacrown Ether Derivatives.

Liquid membranes containing cyclic and acyclic tetrathiazaalkanes bearing a hydrazone moiety as a proton-dissociable group exhibited effective uphill silver ion transport behavior in the proton-driven cation transport. Excellent silver ion selectivities relative to other class ab and class b metal ions were observed for these membranes when citric acid was used for adjusting pH and for preventing hydrolysis of several metal ions in the source phase. Complete recovery of silver ion from a silver solder sample was selectively achieved using the liquid membrane containing acyclic tetrathiazaalkane hydrazone.

Junichi Ishikawa

Papers

Excellent mercury(II) ion selectivefluoroionophore based on a 3,6,12,15-tetrathia-9-azaheptadecane derivativebearing a nitrobenzoxadiazolyl moiety

Silver Ion Selective Fluoroionophores Based on Anthracene-Linked Polythiazaalkane or Polythiaalkane Derivatives.

Hydrazones Derived from Dithiamonoaza and Tetrathiamonoaza Analogs of Polyethers as Silver Ion Selective Ionophores: Syntheses, Proton-Dissociation Behaviors, and Metal Ion Complexing Properties in 1,4-Dioxane–Water Acidic Solution

Silver Ion Selective Extraction with Dithiaza-, Tetrathiaza-, and Tetrathiadiazacrown Ether Derivatives.

Highly Silver Ion-selective Transport Through Liquid Membranes Containing Cyclic and Acyclic Polythiamonoazaalkanes Bearing an Easily Ionizable Moiety