A Novel Class of Powerful Neutral Chelating Reagents : β-Biphosphoramides

Abstract

The structure of β-diphosphoramide chelates and their use as novel extractants are described.     

Selective adsorption of 2,4-dinitrophenol on molecularly imprinted nanocomposites of mesoporous silica SBA-15/polyaniline

Surface imprinting and adoption of a nano-sized physical form are two effective approaches to overcome the template transfer difficulty within molecularly imprinted polymers (MIPs). This work is an attempt to conquer the problem of template transfer difficulty within MIPs by using a nano-reactor as a substrate for the reaction between the monomer and the template. Negatively charged hexagonal nano-channels of SBA-15 can act as a support for attachment of positively charged aniline monomers and the 2,4-dinitrophenol (2,4-DNP) template. The imprinted and non-imprinted SBA-15/polyaniline nanocomposites were characterized by Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and nitrogen adsorption-desorption isotherms. The results showed that the synthesized polymer possessed a highly ordered mesoporous structure. The distribution coefficient values of 2,4-DNP, K(d (2,4-DNP)), were estimated as 301.4 ± 2.3 and 101.2 ± 1.0 mL g(-1) for imprinted and non-imprinted polymers (NIP), respectively. The MIP-solid-phase extraction (SPE) process was optimized by evaluating the type of washing solvent and the composition and volume of the eluting solvent. The prepared MIP was used as a selective sorbent for SPE of 2,4-DNP in the presence of phenolic compounds in tap and sea water. The experimental results indicated that the MIP-SPE and NIP-SPE column yielded recoveries higher than 96% and 38%, respectively. The R.S.D. values were also lower than 3.2% and 4.6% for MIP-SPE and NIP-SPE, respectively.     

Novel modified nanoporous silica for oral drug delivery: loading and release of clarithromycin

Nanoporous silica SBA-15 was prepared to evaluate its application as an oral drug delivery system. A series of surface-functionalized nanopore materials as efficient clarithromycin delivery carriers was investigated. An efficient pH-responsive carrier system was constructed by hydrogen bond interaction between carboxyl and hydroxyl groups in the clarithromycin and the amine group in modified SBA-15. HPLC analyses of clarithromycin were run on a C₁₈ column using a mobile phase comprised of potassium dihydrogen phosphate, acetonitrile and methanol (30:40:30, v/v/v). Active molecules such as clarithromycin could be stored and released from the pore voids of SBA-15 by changing the pH. The amount of clarithromycin stored in the pores of nanoporous silica based on TREN [tris(2-aminoethyl) amine]-modified SBA-15 rods was up to 46 ± 4.8 wt% at pH 8. In addition, when the pH was below 4, clarithromycin was steadily released from the pores of SBA-15 (up to 97 wt% in simulated gastric medium).     

Preparation and evaluation of solid-phase microextraction fiber based on nano-structured copolymer of aniline and m-amino benzoic acid coating for the analysis of fatty acids in zooplanktons

A novel nano-structured copolymer of aniline and m-amino benzoic acid (m-ABA) was introduced as a coating of solid phase microextraction (SPME) of saturated-fatty acids in zooplanktons by coupling to gas chromatography-mass spectrometry (GC-MS). The nano-structured coating was prepared using co-polymerization of m-aminobenzoic acid and aniline. Improved temperature resistance (up to 350°C), relatively improved life time (more than 50 times) and satisfactory extraction efficiency were obtained by insertion of carboxylate groups into the framework of polyaniline. Different extraction parameters such as extraction temperature, extraction time, ionic strength, stirring rate and headspace volume were investigated and optimized. Single fiber repeatability and fiber-to-fiber reproducibility were <5.7% and <10.2%, respectively and the limits of detection varied from 0.01 (C14:0) to 6.07 μg L(-1) (C20:0). Correlation coefficients (R(2)) of the calibration curves ranged from 0.992 (C20:0) to 0.998 (C18:0) with a linearity from 0.5 to 200 μg mL(-1). The recoveries obtained ranged from 83% (C16:0) to 115% (C14:0).     

Existence of global solutions to nonlinear fuzzy Volterra integro-differential equations

In this paper, we introduce new solutions for fuzzy differential equations as mixed solutions, and prove the existence and uniqueness of global solutions for fuzzy initial value problems involving integro-differential operators of Volterra type. One example is also given by applying mixed solution concept to fuzzy linear differential equations for obtaining their global solutions.     

Transition states of the retro-ene reactions of allylic diazenes

[reaction: see text] Density functional theory studies of intramolecular retro-ene reactions of allyldiazenes show that the reaction is a concerted process involving a six-center cyclic transition state. The activation barriers for deazetization for X = H, Me, F, Cl, and Br (3a-e) are 2.4, 40.2, 22.3, 9.3, and 8.8 kcal/mol, respectively.