Synthesis, Structure, and Ion Selective Complexation of Trans and Cis Isomers of Photochromic Dithia-18-crown-6 Ethers

Abstract

Photochromic styryl dyes containing benzodithia-18-crown-6 and N-substituted benzothiazolium moieties are synthesized and characterized spectroscopically and, for a specific case, by X-ray crystallography. The effects of the N-substituent and of sulfur atom substitution in the crown ether cavity on metal cation complex formation and on photochromism due to reversible trans−cis photoisomerization are evaluated. High selectivities for heavy metal ions, such as Ag+ and Hg2+, are observed, in contrast to the benzo-18-crown-6 dyes which selectively bind alkali and alkali earth cations. Relative complex formation stability constants, determined spectrophotometrically, are converted to absolute values by polarographic measurements. The stability constant for Hg2+ complex formation by the trans dye is enhanced 47-fold upon substitution of the 4-butylsulfonate group for methyl at the nitrogen of the benzothiazolium moiety. Photoisomerization to the cis dye is accompanied by a further 11-fold stability constant increase and by spectral changes that are consistent with formation of an ion-“capped” complex, involving intramolecular coordination of the sulfonate anion to Hg2+. Addition of a large excess of Mg2+ ions disrupts this intramolecular coordination bond without displacing the Hg2+ ion from the dithiacrown ether cavity.

Synthesis, Structure, Spectroscopic Studies, and Complexation of Novel Crown Ether Butadienyl Dyes

“…The Mg, Ca, Sr, and Ba perchlorates (Aldrich) were dried in vacuo at 2308. Et 4 NClO 4 was prepared from HClO 4 and Et 4 NOH and twice recrystallized from H 2 O and dried in vacuo at 508. MeCN (for spectrophotometry, transmission l !…”

Synthesis, Optical Characteristics and Complex Formation of Molecular Receptors Based on 1,8-Naphthalimide Derivatives in Solution and in Composition of Hybrid Tin Dioxide Nanoparticles

“…These results are presumably due to well-known high affinity of thiacrown ethers towards the Hg 2+ , Pb 2+ and Cu 2+ cations. [12] The degree of fluorescence enhancement (FE) of 2b in the presence of tenfold excess of various metal cations is shown in Figure 5. FE value represents the ratio of the integrated fluorescence intensities of the ligand solution in the presence and absence of the cation, respectively.…”

“…Furthermore, the 1,8-naphthalimide derivatives containing dithiacrown ether moieties are capable of binding with heavy and transition metals cations in organic solvents and in aqueous medium. [12] Previously we have carried out the attachment of crown ether containing 1,8-naphthalimides to the surface of SnO 2 through the silicon-organic linker. [13] The obtained hybrid material showed a fluorescence enhancement upon the binding with magnesium cations.…”

Chemosensors with crown ether based receptors

“…36 The binding of Pb 2+ with chromene CEBC 33 occurs in the dark, and UV irradiation releases this cation. 37 Fulgide 34 and its photoisomeric colored form behave as chromogenic CEBC displaying blue shift of the longest wavelength absorption band upon complexation with alkali and alkaline earth metal cations.…”