Design principles of fluorescent molecular sensors for cation recognition

Pyrene-based materials for organic electronics.

Calixarene-derived fluorescent probes.

A new fluorescent chemosensor with two different types of cation binding sites on the lower rims of a 1,3-alternate calix[4]arene (1) is synthesized. Two pyrene moieties linked to a cation recognit...

An Excimer-Based, Binuclear, On−Off Switchable Calix[4]crown Chemosensor

A neutral 2-site chloride selective compound has been developed (3), based on a 1,3-alternate tetrasubstituted calix[4]arene providing a preorganized supramolecular scaffold. The resultant supramolecular cavity is among the first to combine urea functional groups bridged with single methylene spacers to pyrene moieties. It combines a naturally and synthetically proven H-bonding system with the elegant ratiometric fluorescent signaling properties of an intramolecular pyrene excimer system, triggered by conformational changes upon anion coordination. The excimer emission of 3 is quenched, with a simultaneous rise in the monomer emission solely by the chloride anion among a wide variety of anions tested. 3 has an association constant of 2.4 x 10(4) M(-1) with chloride. The suitability and advantages of ratiometric optical sensor compounds like 3 for use in practical sensor devices is discussed. 3 has an LOD of 8 x 10(-6) M with chloride in acetonitrile-chloroform (95:5 v/v). A dynamic fluorescence study revealed a response time of < 3 s. A recently developed and simple HPLC-based purification method complimented conventional organic work up methods to yield pure product.

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Chloride selective calix[4]arene optical sensor combining urea functionality with pyrene excimer transduction.

New fluorescent reagents, 2,2‘-[oxybis(3-oxapentamethyleneoxy)]-bis[N-(1-pyrenylmethyl)benzamide)] (4) and its analogues (2, 3, and 5) which have two pyrenes at the both terminals of polyoxyethylene compounds, were synthesized, and their complexation behavior with alkaline earth cations was investigated by fluorescence spectrometry, fluorescence lifetimes, and 1H NMR spectrometry. These reagents (3−5) showed strong intramolecular excimer emissions around at 480 nm in the fluorescence spectra. On the complexation with alkaline earth metal cations, the increase of monomer emission around at 400 nm accompanied by the disappearance of intramolecular excimer emission of free reagents was observed. These reagents formed a 1:1 complex, and the order of complex formation constants was Ca2+ ≅ Sr2+ > Ba2+ > Mg2+ > Li+ for all reagents. 1H NMR spectra of these complexes with alkaline earth cations suggested the helical structures of the complexes. Fluorescence spectral changes at the formation of complexes depended ...

New Fluorimetric Alkali and Alkaline Earth Metal Cation Sensors Based on Noncyclic Crown Ethers by Means of Intramolecular Excimer Formation of Pyrene

Recent advances regarding podand derivatives which are non-cyclic crown ethers incorporating functional groups have been reviewed. Particular attention has been paid to fluorophore appended non-cyclic crown ethers as sensors for cation detection. Their complexation behavior with alkali and alkaline earth cations and interactions between their terminal groups is also discussed in detail.

New Fluorophores Based on Non-Cyclic Crown Ethers for Alkali and Alkaline Earth Metal Cation

https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/43119/1/CS52-6_2098-2103.pdf

Microstructure and analysis of oxide scales formed on Cr–Si–Ni compacts in air and H2O-containing atmosphere

Differential pulse voltammetry of Cr 6+ /Cr 3+ in alkali silicates, which has been worked in the previous study (Ref. (11)) was extended to silicate melts containing alkalin earth oxides. The basicity scale of new systems finds more relevant applications to practical slags. As compared at the disilicate composition, the basicity increase in the order of MgO, CaO and Li 2 O, BaO, Na 2 O, K 2 O, Rb 2 O, and Cs 2 O.

Yoshio Suzuki

Papers

New Fluorimetric Alkali and Alkaline Earth Metal Cation Sensors Based on Noncyclic Crown Ethers by Means of Intramolecular Excimer Formation of Pyrene

New Fluorophores Based on Non-Cyclic Crown Ethers for Alkali and Alkaline Earth Metal Cation

Microstructure and analysis of oxide scales formed on Cr–Si–Ni compacts in air and H2O-containing atmosphere

Basicity of Alkaline Earth Silicate Melts Based on the Cr6+/Cr3+ Redox Equilibria