Novel Triphenylamine Appended 1,3-Alternate-Calix[4]arenes: Synthesis and Characterization

In the present study, two novel calix[4]arene receptors containing triphenylamine units in 1,3-alternate conformation have been synthesized and characterized in detail. First, the 25,27-dipropoxy-26,28-bis[(3-aminopropyl)oxy]-calix[4]arene 4 and 25,26,27,28-tetra[(3-aminopropyl)oxy]-calix[4]arene 7 were prepared by using convenient reagents. Then, these amino derivatives of calix[4]arene were converted to Schiff base derivatives appended to triphenylamine of calix[4]arene (5 and 8) using 4-formyltriphenylamine via condensation. The 1,3-alternate conformation of the synthesized calix[4]arenes was determined by ¹H and ¹³C NMR analyses. Also, their structures have been characterized by using ¹H and ¹³C NMR, infrared, and elemental analyses.

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‘Naked-eye’ detection of F− ions by two novel colorimetric receptors

Two novel colorimetric receptors, S1 and S2, linked to one or two nitrophenylurea groups were synthesized in good yields, characterized and their chromogenic properties investigated towards various anions (F^?, Cl^?, Br^?, I^?, NO₃^?, AcO^?, ClO₄^?, HSO₄^?, and H₂PO₄^?) by UV–vis and ¹H NMR techniques. The receptors, effectively and selectively, recognized and distinguished the biologically important F^? from other anions such as Cl^?, Br^?, I^? etc. in CH₃CN. This selectivity could be easily observed by the naked eye, indicating that receptors S1 and S2 are potential colorimetric sensors for fluoride ion.     

Competitive formation of cis and trans derivatives in the nucleophilic substitution reactions of cyclophosphazenes having a mono-spiro P-NHR group

Nucleophilic substitution reactions of N(3)P(3)Cl(4)[NH(CH(2))(3)NMe] (1) and N(3)P(3)Cl(4)[NH(CH(2))(3)O] (2) with mono-functional alcohols (methanol, 2,2,2-trifluoroethanol, phenol) and a secondary amine (pyrrolidine) were used to investigate the relationship between the incoming nucleophile and the proportions of products with substituents that are cis or trans to the spiro NH moiety. The reaction products were characterized by elemental analysis, mass spectrometry, (1)H and (31)P NMR spectroscopy and the configurational isomers by X-ray crystallography. Six products have been characterised with the substituent cis to the spiro NH group for the alcohol (methanol, phenol) and pyrrolidine derivatives of both compounds 1 and 2, compared to just one derivative with the substituent trans to the spiro NH group, that for the pyrrolidine derivative of compound 2. For each reaction the relative proportions of cis and trans isomers were determined by (31)P NMR measurements of the reaction mixtures. It was found that the reactions of compound 1 with all three alcohols and of compound 2 with methanol lead to exclusive formation of isomers with the substituent cis to the NH moiety, whereas all other reactions lead to mixtures of cis and trans isomers in different ratios under standard reaction conditions. However, when crown ether is included in the reaction medium for the reactions of compound 2 with both 2,2,2-trifluoroethanol and phenol, it is found that only cis isomers are formed. All these results are rationalised in terms of the competition between at least two effects; the cis-directing effect by hydrogen bonding of the incoming nucleophile to the spiro N-H group already present on the cyclophophazene ring and the cis-directing effect of the sodium cation coordinating to the oxygen lone pairs of the P-O moiety of the spiro ring.     

Preparation and chromatographic performance of calix[4]crown-5 macrocycle-bonded silica stationary phase

A new calix[4]crown-5 macrocycle-bonded silica stationary phase (CL-CIMS) was prepared and applied at the same time to develop a chromatographic procedure to separate aromatic amines, phenols and drugs in this study. The chromatographic behaviors of the prepared stationary phase for these analytes were studied and compared with those of ODS (octadecylsilane). The effect of organic modifier content and pH of the mobile phase on retention and selectivity of these compounds were investigated. Some aromatic amines, phenols or drugs on CL-CIMS were successfully separated. The results show that CL-CIMS exhibits high selectivities for the above analytes in high aqueous mobile phases and a bright prospect in routine, fast separation of aromatic amines, phenols and drug compounds. From chromatographic data, it can be concluded that hydrophobic interaction is mainly responsible for the retention behavior as well as hydrogen-bonding interaction, π-π and dipole-dipole interaction.     

Chemical composition and antibacterial activity of Origanum saccatum P.H. Davis essential oil obtained by solvent-free microwave extraction: comparison with hydrodistillation

The components of the essential oils (EOs) obtained by solvent-free microwave extraction (SFME) and hydrodistillation (HD) from endemic Origanum saccatum P.H. Davis were identified by using GC/MS. The main constituents of both EOs obtained by SFME and HD, respectively, from O. saccatum were p-cymene (72.5 and 70.6%), thymol (9.32 and 8.11%), and carvacrol (7.18 and 6.36%). The EO obtained by SFME contained substantially higher amounts of oxygenated compounds and lower amounts of monoterpenes than did the EO obtained by HD. The antibacterial activities of the EOs obtained by SFME and HD were evaluated with the disc diffusion method by comparison with 10 different bacterial strains. The antibacterial activity of the EO extracted by SFME was found to be more effective than that of the EO extracted by HD against seven of the tested bacteria.     

A Robust,Precious-Metal-Free Dye-Sensitized Photoanode for Water Oxidation: A Nanosecond-Long Excited-State Lifetime through a Prussian Blue Analogue

Herein, we establish a simple synthetic strategy affording a heterogeneous, precious metal-free, dye-sensitized photoelectrode for water oxidation, which incorporates a Prussian blue (PB) structure for the sensitization of TiO₂ and water oxidation catalysis. Our approach involves the use of a Fe(CN)₅ bridging group not only as a cyanide precursor for the formation of a PB-type structure but also as an electron shuttle between an organic chromophore and the catalytic center. The resulting hetero-functional PB-modified TiO₂ electrode demonstrates a low-cost and easy-to-construct photoanode, which exhibits favorable electron transfers with a remarkable excited state lifetime on the order of nanoseconds and an extended light absorption capacity of up to 500 nm. Our approach paves the way for a new family of precious metal-free robust dye-sensitized photoelectrodes for water oxidation, in which a variety of common organic chromophores can be employed in conjunction with CoFe PB structures.     

Immobilization of Invertase in DAD Type Polymers: Combination of Benzothiadiazole Acceptor Unit and 3,4-Ethylenedioxythiophene and Thiophene Donor Units

Conductive polymers with donor-acceptor-donor (DAD) type units; benzothiadiazole acceptor unit and 3,4-ethylenedioxythiophene (EDOT) and thiophene (Th) donor units, were investigated for immobilization of invertase. The polymers were prepared potentiodynamically from their monomers, M₁ (Th-benzothiadiazole-Th), M₂ (EDOT-benzothiadiazole-EDOT), M₃ (Th-benzothiadiazole-EDOT) and a copolymer, which is a homolog to homopolymer of M₃, was prepared from M₁ and M₂. Invertase was trapped between a two layer-composite; DAD polymer and polypyrrole. The characterization of immobilized invertase was performed using a spectrophotometric method at 540 nm. Kinetic parameters, V _max, maximum reaction rate and K_m , Michaelis-Menten constant values of immobilized invertase in DAD type homopolymer (P₃), 0.95 μmol min^?1 and 22.7 mM, respectively, are found between those of homopolymers P₁ and P₂ and are better than the copolymer. Polymers and copolymers exhibited a broad optimal temperature profile between 30 and 50°C compared to the free enzyme. Optimum pH (5.0) is the same as for free invertase. The electrodes were found to be stable with 100% activity during one day for 40 consecutive measurements. As to the self-life, 25% of the initial activity was lost in the first ten days, then the electrodes were stable with 75% activity for a 40 day storage at 4°C.     

Removal of Chromium Anions with Nanofiltration-Complexation by Using p-Sulfonated Calix[4]arene

This article describes the removal of chromium anions from aqueous solutions by using nanofiltration-complexation consisting of pilot-scale nanofiltration equipment (Osmonics Sepa CF Membrane Cell) and water-soluble p-sulfonated calix[4]arene ligand. For the determination of optimum removal conditions of the chromium anions, the effect of pH, ligand cavity size, and foreign anions on the retention of the chromium anions in nanofiltration-complexation system was also evaluated. The results showed that water-soluble p-sulfonated calix[4]arene was an effective and selective ligand for the chromium anions over Cl^? , SO₄ ^2 ?  and NO₃ ^?  anions in nanofiltration-complexation system at pH 9.4.     

Polymerization of 2‐hydroxyethyl acrylate in bulk and solution by chemical initiator and by ATRP method

In this study, 2‐hydroxyethyl acrylate (HEA) was polymerized to obtain polymers that can be used as hydrogel and copolymerized for biomedical applications. Bulk, solution, and atom transfer radical polymerization (ATRP) techniques at different temperatures were applied. The polymerization in bulk form was carried out in vacuum and in open atmosphere. The polymerization curves showed autoacceleration mechanism and the limiting conversion was 100%. The polymers obtained were insoluable in most common solvents because of high molecular weights and strong intermolecular hydrogen bonding. They absorb more than 30% (w/w) water as hydrogel. To decrease the molecular weight and obtain soluble polymers, HEA was polymerized in solution by ATRP method, which also gave insoluble hydrogel type polymers. The activation energy for bulk polymerization was 155.8 kJ/mol, which is very high for a free radical polymerization. This is due to the high degree of intermolecular hydrogen bonding, which was also supported by FTIR and TGA analysis. The polymers were characterized by FT‐IR, DSC, TGA, and ¹H NMR techniques. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3957–3965, 2005     

Relationship between self-association of glycine molecules in supersaturated solutions and solid state outcome

Small angle x-ray scattering is utilized to directly examine the formation of clusters in supersaturated solutions of glycine, in an attempt to understand their role in the nucleation process. The results suggest that the majority of glycine molecules exist as dimers in aqueous solutions, and monomers in 13% (upsilon/upsilon) acetic acid-water mixtures. As the water and acetic acid-water solutions crystallize into alpha and gamma forms, respectively, the findings indicate a direct correlation between molecular self-association in solution and the polymorphic outcome.