Coordination polymers and a dinuclear complex constructed from zinc(II) ions and fluorescein: iodine adsorption and optical properties

Abstract

1-D coordination polymers, ¹_∞[Zn(fl)₂]·2EtOH and ¹_∞[Zn(fl)₂]·2MeOH, and a dinuclear complex, [{Zn(fl)₂}₂(dienpip)]·4H₂O·4EtOH (dienpip?= N,N′-bis(2-aminoethyl)piperazine), were obtained using Zn(II) ions and fluorescein anions (fl). Thermal analysis shows stability of the polymers after solvent removal up to more than 400?°C. Crystallization solvent molecules were removed under reduced pressure with the preservation of the polymeric structure, ¹_∞[Zn(fl)₂]. Desolvated crystals were exposed to I₂ vapors and the crystal structure determination by X-ray diffraction confirmed the presence of I₂ molecules in the channels generated in crystals by the metal-organic framework. The iodine content, evaluated by X-ray diffraction, corresponds to the overall formula ¹_∞[Zn(fl)₂]·0.3I₂. The optical properties of the coordination polymers and the dinuclear complex have been investigated.     

Intermolecular cyclization of cinnamoyl isothiocyanate: A new synthetic entry for pyrimidine,triazine, and triazole candidates

An efficient and facile protocol for the synthesis of azine and azole ring systems was reported. Whereas, reaction of cinnamoyl isothiocyanate with N-nucleophile containing compounds (namely, p-aminophenol (2), N¹-phenylbenzene-1,4-diamine (5) and p-aminoacetophenone (8)) tolerated thiourea derivatives 3, 6, and 9, respectively. The later compounds underwent intramolecular cyclization upon treatment with EtONa to give pyrimidinethiones 4, 7, and 10, respectively, in moderate yield (74–79%). Compound 9 underwent intramolecular cyclization and condensation upon reaction with NaOH and benzaldehyde to give pyrimidinethione 12. Thiosemicarbazides 14 and 19 were obtained through reaction of heteroallen 1 with 2,4-dinitrophenylhydrazine 13 and hydrazone 18, respectively. Compound 14 was cyclized to pyrimidinethione 15 and triazine derivatives 17 through its reaction with EtONa at room temperature and refluxing temperature, respectively. Finally, base mediated and oxidative cyclization of thiourea derivative 19 with EtONa, Br₂/AcOH, and Pb(OAc)₂ afforded thiadiazole 20, benzothiazolotriazole 21, and triazolethione 22 derivatives, respectively.     

Synthesis and characterization of fluorescent starch using fluorescein as fluorophore: potential polymeric temperature/pH indicators

A convenient method for attaching fluorescein (via its epoxy derivate) to natural starch and its temperature/pH‐sensitive qualities of fluorescence were investigated. 3‐epoxypropoxy fluorescein (EPF) was first synthesized through the reaction between fluorescein and epichlorohydrin, and starch‐bearing fluorescein (ST‐EPF) was prepared via ring‐opening reaction with EPF in dimethyl sulfoxide (DMSO) solution, in the presence of NaH as a catalyst. Both of them were characterized by the methods of ¹H NMR, MS, IR, XRD, UV–Vis, and luminescence spectra, respectively. The chemiluminescent and photophysical behaviors of the dye fluorescein derivative and the polymer‐containing fluorescein were studied. The results indicated that ST‐EPF could still provide temperature and pH sensitivity similar to that of fluorescein and could achieve better long‐term stability and fast equilibrium response. ST‐EPF had an excellent linear response between relative fluorescence intensity and temperature in the range of 0–60°C and a nonlinear relationship between relative fluorescence intensity and pH in the wide range of 0.0–12.0, and so it has promise as an optical transducer for temperature and pH value determinations. Copyright © 2008 John Wiley & Sons, Ltd.     

The HPLC Enantioresolution of Phenyl Isothiocyanated Amino Acids on Vancomycin Bonded Phase Using the Acetonitrile‐Based Mobile Phase: A Comparison to the Teicoplanin Phase

The phenyl isothiocyanate, an electrophilic reagent for peptide chain sequencing, is used to pre‐column derivatize a variety of α‐amino acids in alkaline medium before their enantioresolution on a vancomycin bonded chiral phase using the acetonitrile‐based mobile phase. The observed resolution is believed to be due to the re‐location of the hydrogen receptor site from sulfur to nitrogen on the isothiocyanyl fragment of derivatizing reagent, which in turn changes the enantioselectivity. Under the same chromatographic conditions, the resolution for N‐benzoylated, 3,5‐dinitrobenzoylated and N‐carbobenzyloxylated amino acids is either not found or unsatisfactory. Also, no resolution is obtained in the reversed‐ or normal phase mode for all phenyl isothiocyanated amino acids examined in this study.     

High-Performance Liquid Chromatographic Analysis of Amino Acids in Edible Seaweeds after Derivatization with Phenyl Isothiocyanate

Summary A reversed-phase high-performance liquid-chromatographic method has been used for analysis of the amino acids in edible seaweed. Sample proteins were hydrolysed with hydrochloric acid and the amino acids produced were derivatized with phenyl isothiocyanate. The resulting phenylthiocarbamyl amino acids were chromatographed on an ODS2 column with UV detection at 254 nm. The mobile phase was a mixture of 0.14 M ammonium acetate buffer, pH 6.4, containing 0.05% triethylamine (A) and 60:40 (v/v) acetonitrile–water (B), at a flow rate of 1.1 mL min^–1; the elution gradient (min:A%) was: 0:90, 8:90, 10:70, 12:70, 18:52, 20:0, 25:0, 28:90, 35:90. Method precision for the different amino acids was between 1.33 and 3.88% (relative standard deviation); detection limits were between 6.9 and 14.3 ng mL^–1. The amino acid content of the algae analysed ranged from 22.4 ± 1.9 to 138.0 ± 5.6 mg g^–1 d.w. The amino acids present at highest concentrations were glutamic acid, alanine, and phenylalanine.     

Time-Resolved Detection of Hot Electron-Induced Electrochemiluminescence of Fluorescein in Aqueous Solution

Strong electrogenerated chemiluminescence (ECL) of fluorescein is generated during cathodic pulse polarization of oxide-covered aluminum electrodes and the resulting decay of emission is so sluggish that time-resolved detection of fluorescein is feasible. The present ECL in aqueous solution is based on the tunnel emission of hot electrons into the aqueous electrolyte solution, which probably results in the generation of hydrated electrons and hydroxyl radicals acting as redox mediators. The successive one-electron redox steps with the primary radicals result in fluorescein in its lowest excited singlet state. The method allows the detection of fluorescein (or its derivatives containing usable linking groups to biomolecules) over several orders of magnitude of concentration with detection limits well below nanomolar concentration level. The detection limits can still be lowered, e.g., by addition of azide or bromide ions as coreactants. The results suggest that the derivatives of fluorescein, such as fluorescein isothiocyanate (FITC), can be detected by time-resolved measurements and thus be efficiently used as electrochemiluminescent labels in bioaffinity assays.     

A novel one pot multi-component strategy for facile synthesis of 5-aryl-[1,2,4]triazolidine-3-thiones

We have disclosed an efficient, one pot, novel multi-component approach for the synthesis of 5-aryl-[1,2,4]triazolidine-3-thiones from aldehyde, hydrazine hydrate, and trimethylsilyl isothiocyanate (TMSNCS) in the presence of catalytic amount of sulfamic acid. High yields, easy work-up procedure, no chromatographic separation, and novelty in multi-component strategy are the main merits of the present strategy.     

TMEDA-CATALYZED SYNTHESIS OF N-ARYL-N′-ETHOXYCARBONYL THIOUREA AND ARENE (OR POLYMETHYLENE)-BIS-ETHOXYCARBONYLTHIOUREA DERIVATIVES

A novel and efficient method for synthesis ethoxycarbonyl isothiocyanate and ethoxycarbonyl thioureas catalyzed by TMEDA is reported. A series of N-aryl-N′-ethoxycarbonyl thioureas and arene (or polymethylene)-bis-ethoxycarbonyl thiourea derivatives have been synthesized in good-to-excellent yields via this method at room temperature.