Binuclear Orthometalated N,N-Dimethylbenzylamine Complexes of Palladium(II): Synthesis,Structures and Thermal Behavior

Abstract

Organochalcogenolate-bridged cyclometalated palladium(II) complexes of the formulae, [Pd₂(μ-Epy)₂(Me₂NCH₂C₆H₄-C,N)₂] (2) (E = S (2a), Se (2b)), [Pd₂(μ-SAr)(μ-Cl)(Me₂NCH₂C₆H₄-C,N)₂] (3) (Ar = Ph (3a), Mes (Mes = 2,4,6-Me₃C₆H₂) (3b)) and [Pd₂(μ-SeAr)₂(Me₂NCH₂C₆H₄-C,N)₂] (4) (Ar = Ph (4a), Mes (4b)), have been synthesized by the reactions of [Pd₂(μ-Cl)₂(Me₂NCH₂C₆H₄-C,N)₂] with lead or sodium salts of the chalcogenolate ligand. These complexes have been characterized by elemental analysis, mass spectral data, and NMR (¹H and ⁷⁷Se{¹H}) spectroscopy. The molecular structure of 2, determined by single crystal X-ray diffraction analysis, revealed a Epy-bridged head-to-tail arrangement in which the eight-membered “(PdECN)₂” ring adopts a distorted twist boat conformation. The Pd····Pd separation in 2a is within the van-der-Waals interaction but in 2b it is too large to support the presence of any metal–metal interaction. The thermal behavior of these complexes has been studied by thermogravimetric analysis.     

Exploiting Supramolecular Synthons in Designing Gelators Derived from Multiple Drugs

A simple strategy for designing salt‐based supramolecular gelators comprised of various nonsteroidal anti‐inflammatory drugs (NSAIDs) and amantadine (AMN) (an antiviral drug) has been demonstrated using a supramolecular synthon approach. Single‐crystal and powder X‐ray diffraction established the existence of the well‐studied gel‐forming 1D supramolecular synthon, namely, primary ammonium monocarboxylate (PAM) synthon in all the salts. Remarkably five out of six salts were found to be capable of gelling methyl salicylate (MS)—an important ingredient in commercially available topical gels; one such selected biocompatible salt displayed an anti‐inflammatory response in prostaglandin E₂ (PGE₂) assay, thereby indicating their plausible biomedical applications.     

α-Fe_2O_3 immobilized benzimidazolium tribromide as novel magnetically retrievable catalyst for one-pot synthesis of highly functionalized piperidines

Nanostructured α-Fe_2O_3 were prepared by precipitation followed by calcination method.Cetyltrimethylammonium bromide(CTAB) was used as surfactant.The nano α-Fe_2O_3 was then silanized with(3-chloropropyl)-triethoxysilane(CPTES) by room temperature mixing of α-Fe_2O_3 and CPTES to produce silane coated α-Fe_2O_3(ClPr-Si@Fe_2O_3).As-synthesized ClPr-Si@Fe_2O_3 was functionalized via covalent grafting of benzimidazole to produce 3-(l-benzimidazole)Pr-Si@Fe_2O_3.This was further reacted with bromine to afford α-Fe_2O_3 immobilized benzimidazolium tribromide(α-Fe_2O_3-BIM tribromide).This ionic liquid(IL)α-Fe_2O_3 BIM tribromide was characterized by FT-IR,XRD,TEM,SEM,TGA,VSM,EDX and BET analysis.The as-synthesized IL tribromide was used as catalyst for one-pot synthesis of highly substituted piperidines.The method is greener in terms of solvent selection,recovery of the catalyst and efficiency.     

Electrokinetic separation of charged macromolecules in nanochannels within the continuum regime: effects of wall interactions and hydrodynamic confinements

In this paper, a detailed continuum-based theoretical model is proposed to investigate the effects of near-wall potentials and hydrodynamic confinement on separation of charged macromolecules in channels of nanoscale dimensions. These wall effects are primarily confined within a few nanometers from the channel wall, and hence have negligible influences in the conventional electrokinetic separation methods that are routinely performed in microchannels. However, in nanochannels, their zone of influence becomes significant in comparison to the channel height, thereby inducing certain nontrivial effects on the resultant separation characteristics. By executing a regular perturbation analysis, it is established that depending on the macromolecular size relative to the channel height and the extent of electrical double layer (EDL) interactions, the wall forces decide the speed of traverse and the extent of spreading (dispersion) of the macromolecular bands. These factors combine together to finally decide the separation characteristics (quantified by the resolution of separation) of the charged macromolecules in nanochannels. It is demonstrated that because of the near-wall effects, macromolecular pairs with less disparities in sizes give rise to higher values of resolution. Moreover, the wall-induced influences are shown to magnify the resolution for any given pair of macromolecules in the nanofluidic systems, thereby signifying greater separation efficiency.     

Comparison of LC and LC/MS methods for quantifying <Emphasis Type="Italic">N</Emphasis>-glycosylation in recombinant IgGs

High-performance liquid chromatography (LC) and liquid chromatography/electrospray ionization time-of-flight mass spectrometry (LC/ESI-MS) methods with various sample preparation schemes were compared for their ability to identify and quantify glycoforms in two different production lots of a recombinant monoclonal IgG1 antibody. IgG1s contain a conserved N-glycosylation site in the fragment crystallizable (Fc) subunit. Six methods were compared: (1) LC/ESI-MS analysis of intact IgG, (2) LC/ESI-MS analysis of the Fc fragment produced by limited proteolysis with Lys-C, (3) LC/ESI-MS analysis of the IgG heavy chain produced by reduction, (4) LC/ESI-MS analysis of Fc/2 fragment produced by limited proteolysis and reduction, (5) LC/MS analysis of the glycosylated tryptic fragment (293EEQYNSTYR301) using extracted ion chromatograms, and (6) normal phase HPLC analysis of N-glycans cleaved from the IgG using PNGase F. The results suggest that MS quantitation based on the analysis of Fc/2 (4) is accurate and gives results that are comparable to normal phase HPLC analysis of N-glycans (6).     

Electronic and steric effects in binding of deep cavitands

A deep, self-folding cavitand responds to minor electronic differences between suitably sized adamantane guests. Binding constants range from <0.5 to 4000 M(-1) for guests as similar as 1-bromoadamantane and 1-cyanoadamantane. The barriers to guest exchange also vary up to 3 kcal mol(-1).     

Microwave-assisted solvent extraction of solid matrices and subsequent detection of pharmaceuticals and personal care products (PPCPs) using gas chromatography-mass spectrometry

Concentrations of pharmaceuticals and personal care products (PPCPs) in natural solids remain largely unknown. Contributing to this, is a lack of methods permitting the simultaneous detection of the diverse, low-level contaminants present in these complex matrices. We have developed a microwave-assisted solvent extraction (MASE)-based method targeting seven diverse PPCPs (caffeine, 17β-estradiol, ibuprofen, ketoprofen, musk ketone, naproxen, and triclosan) and a molecular marker for fecal waste (epicoprostanol). The method consisted of optimizing the following variables: derivatization of the polar target analytes, silica gel open column clean-up, and gas chromatographic-mass spectrometric (GC-MS) analysis of sample extracts for analysis and detection of the compounds noted above. Testing of the method on spiked soil allowed for 89.6 ± 2.89% recovery of three target compounds and 25.0 ± 1.93% recovery of five of the compounds. Although the latter recoveries were low, the precision across all recoveries was high, suggesting good reproducibility in application of the method. Furthermore, we suspect that matrix effects are likely responsible for the lower recoveries. Techniques with the exclusive incorporation of organic solvents were found inapplicable in the study of a pharmaceutical salt, diphenhydramine HCl. Application of the developed method to sediment collected directly downstream of the effluent pipe of a wastewater treatment plant allowed detection of ibuprofen, naproxen, ketoprofen, and epicoprostanol at ng-μg per gram dry weight concentrations. The observation of acidic pharmaceuticals, previously believed to exhibit insignificant sorption to solid matrices, in the tested sediment samples, coupled with application of biosolids for agricultural purposes, demonstrates the need for expanded investigation of PPCP contamination of natural solid matrices.