Stereochemically Active and Inactive Lone Pairs in Two Room-Temperature Phosphorescence Coordination Polymers of Pb2+ with Different Tricarboxylic Acids.

Two new Pb2+-based coordination polymers (CPs), [Pb2(HBTC)2(DMF)] (1) and [Pb(HPTC)] (2), have been synthesized under solvothermal condition; herein, H3BTC and H3PTC represent 1,3,5-benzenetricarboxylic acid and 2,4,6-pyridine tricarboxylic acid, respectively. Both 1 and 2 were characterized by microanalysis, infrared spectra (IR), thermal gravimetric analyses (TGA), and powder X-ray diffraction (PXRD) techniques. Single-crystal structural analysis indicates that 1 and 2 show different coordination sphere around Pb2+ ions and distinct coordination frameworks. The I1O2 type three-dimensional (3D) nonporous metal-organic framework forms in 1, where the Pb2+ ion shows holo-directed coordination geometry, while the I0O2 type two-dimensional (2D) coordination polymeric layered structure forms in 2, where Pb2+ ion shows a hemidirected coordination sphere and the 6s2 lone electron pair in Pb2+ ion is stereochemically active. The two CPs emit intense and long-lasting greenish phosphorescence in air at room temperature, with absolute quantum yields of 1.2% for 1 and 4.7% for 2 and decay lifetimes of 0.73 ms for 1 and 1.52 ms for 2.

Quantification of pantoprazole in human plasma using LC-MS/MS for pharmacokinetics and bioequivalence study.

A highly sensitive and rapid method for the analysis of pantoprazole in human plasma using liquid chromatography coupled to tandem electrospray ionization mass spectrometry was developed. The procedure involves a simple protein precipitation method with methyl alcohol and separation by RP-HPLC. Detection was performed by positive ion electrospray ionization in multiple reaction monitoring mode, monitoring the transitions m/z 384.1→200.0 and m/z 346.1→198.0, for quantification of pantoprazole and IS, respectively. The standard calibration curves showed good linearity within the range of 5-5,000 ng mL(-1). The lower limit of quantitation (LLOQ) was about 5 ng mL(-1). The extractive recovery of pantoprazole from the biological matrix was more than 77.58% and the matrix effect was complied with relevant provision. The intra-day accuracy of the drug containing serum samples was more than 92.19% with a precision of 0.79-5.36%. The inter-day accuracy was 85.49% or more, with a precision of 0.91-12.67%. Intra and inter-day accuracy of the assay at four concentrations were 97.9-98.2% with a precision of 4.2-13.9%. This method offered good precision and accuracy and was successfully applied to the pharmacokinetic and bioequivalence studies of 40 mg of enteric-coated pantoprazole in 20 healthy Chinese volunteers.

Phase selectivity and tunable photophysical nature of rare earth metal-organic frameworks of EuxY1-x-PTC (H3PTC = 2,4,6-pyridine tricarboxylic acid; x = 0-1).

Two rare earth metal-organic frameworks (MOFs), [Y2(PTC)2(H2O)2]·3H2O (Y-PTC) and [Eu2(PTC)2(H2O)5]·H2O (Eu-PTC) together with the solid solutions [Eu2xY2(1-x)(PTC)2(H2O)5]·H2O (EuxY1-x-PTC, x = 0.013-0.82), were synthesized hydrothermally, and characterized by microanalysis, IR spectroscopy, TG, powder, and single crystal X-ray diffraction techniques. Eu-PTC and Y-PTC showed different crystal structures; however, all solid solutions were isomorphic to Eu-PTC even at x = 0.013, leading to the IR spectra and TG plots of the solid solutions to be similar to those of Eu-PTC but distinct from those of Y-PTC. DFT calculations for the crystal lattice energy demonstrated that the procedure for the crystallizing nucleation of Eu-PTC occurred prior to that of Y-PTC in the reaction solution, leading to the all solid solutions being isomorphic to Eu-PTC. The solid emission spectra at ambient condition showed that Y-PTC emitted ligand-based phosphorescence at 433 nm with a quantum yield (QY) of 27.02%, while Eu-PTC and EuxY1-x-PTC (x = 0.013-0.82) emitted the characteristic luminescence of Eu3+ ions, and most solid solutions showed higher QYs than Eu-PTC; in particular, the QY of Eu0.195Y0.805-PTC was up to 29.48%, i.e., increased by 10% regarding Eu-PTC (19.86%). Interestingly, solid solutions with x = 0.013-0.395 showed excitation-wavelength-dependent luminescence, and such type of luminescence MOFs have promising applications including the areas of precise temperature, gas sensing and information encryption or anti-counterfeiting materials.

Crystal Structures, Photoluminescence, and Magnetism of Two Novel Transition-Metal Complex Cocrystals with Three-Dimensional H-Bonding Organic Framework or Alternating Noncovalent Anionic and Cationic Layers.

Cocrystallization may alter material physicochemical properties; thus, the strategy of forming a cocrystal is generally used to improve the material performance for practical applications. In this study, two transition-metal complex cocrystals [Zn(bpy)3]H0.5BDC·H1.5BDC·0.5bpy·3H2O (1) and [Cu2(BDC)(bpy)4]BDC·bpy·2H2O (2) have been achieved using a hydrothermal reaction, where bpy and H2BDC represent 2,2'-bipyridine and benzene-1,3-dicarboxylic acid, respectively. Cocrystals were characterized by microanalysis, infrared spectroscopy, and UV-visible spectroscopy. Cocrystal 1 contains five components and crystallizes in a monoclinic space group P21/n. The H0.5BDC1.5-, H1.5BDC0.5-, and H2O molecules construct three-dimensional H-bonding organic framework; the [Zn(bpy)3]2+ coordination cations and uncoordinated bpy molecules reside in channels, where two coordinated bpy ligands in [Zn(bpy)3]2+ and one uncoordinated bpy adopt sandwich-type alignment via π···π stacking interactions. Cocrystal 2 with four components crystallizes in a triclinic space group P-1 to form alternating layers; the binuclear [Cu2(bpy)4(BDC)]2+ cations and uncoordinated bpy molecules build the cationic layers, and the BDC2- species with disordered lattice water molecules form the anionic layers. Cocrystal 1 shows intense photoluminescence at an ambient condition with a quantum yield of 14.96% and decay time of 0.48 ns, attributed to the π* → π electron transition within phenyl/pyridyl rings, and 2 exhibits magnetic behavior of an almost isolated spin system with rather weak antiferromagnetic coupling in the [Cu2(bpy)4(BDC)]2+ cation.

Preparation of imprinted polymers at surface of magnetic nanoparticles for the selective extraction of tadalafil from medicines.

In this paper, highly selective core-shell molecularly imprinted polymers (MIPs) of tadalafil on the surface of magnetic nanoparticles (MNPs) were prepared. Three widely used functional monomers 2-(trifluoromethyl) acrylic acid (TFMAA), acrylic acid (AA), and methacrylic acid (MAA) were compared theoretically as the candidates for MIP preparation. MIP-coated magnetic nanoparticles (MIP-coated MNPs) showed large adsorption capacity, high recognition ability, and fast binding kinetics for tadalafil. Furthermore, because of the good magnetic properties, MIP-coated MNPs can achieve rapid and efficient separation with an external magnetic field simply. The resulting MIP-coated MNPs were used as dispersive solid-phase extraction (DSPE) materials coupled with HPLC-UV for the selective extraction and detection of tadalafil from medicines (herbal sexual health products). Encouraging results were obtained. The amounts of tadalafil that were detected from the herbal sexual health product was 43.46 nmol g(-1), and the recoveries were in the range of 87.36-90.93% with the RSD < 6.55%.

Determination of itopride hydrochloride in human plasma by RP-HPLC with fluorescence detection and its use in bioequivalence study.

A sensitive, selective and simple method using a precipitation of protein with 10% perchloric acid, followed by high-performance liquid chromatography (HPLC) with fluorescence detection was developed for the determination of itopride hydrochloride in human plasma, using levofloxacin as the internal standard (IS). Chromatographic separation was obtained within 7.0 min using a reverse phase Hypersil BDS C(18) (250 mm x 4.6 mm, 5 microm) column and an isocratic mobile phase, constituting of a mixture of 0.1 mol/l ammonium acetate-methanol (30:70, v/v) flowing at 1.1 ml/min. The excitation and emission wavelengths were set at 304 and 344 nm, respectively. The method was validated over the concentration range of 5 ng/ml to 1000.0 ng/ml. The lower limit of quantitation (LLOQ) was 5 ng/ml. The extractive recovery of itopride hydrochloride from the biological matrix was more than 80.77%. The intra-day accuracy of the drug containing serum samples was more than 82.94% with a precision of 2.81-4.37%. The inter-day accuracy was 82.91% or more, with a precision of 6.89-9.54%. The limit we have used (70-143%) is based on the local regulatory authority (SFDA). The developed method was validated and successfully applied to bioequivalence studies of itopride hydrochloride in healthy male volunteers.