“Seems Bad Turns Good” – traces of precursor in dicationic ionic liquid lead to analytical application

Research on Chemical Intermediates - We explored a geminal dicationic ionic liquid (DCIL), 1′-(propane-1,3-diyl)bis(4-aminopyridin-1-ium) dibromide, [C3(Amp)2][Br]2, as a fluorescent probe...     

Thermosensitive water‐soluble poly(ethylene glycol)‐based polythiophene graft copolymers

Diethyleneglycol methylethermethacrylate(MeO₂MA) and oligoethylene glycol methylethermethacrylate(OEGMA) are polymerized on polythiophene(PT) backbone to produce water‐soluble PT‐g‐PMeO₂MA(PTD) and PT‐g‐P(MeO₂MA‐co‐OEGMA)(PTDO) using atom transfer radical polymerization. They are characterized by ¹H NMR and GPC techniques. TEM micrographs indicate that PT‐chains self‐organize as nanospheres, and atomic force micrographs suggest that aggregated PT‐chains are present at the centre surrounded by dispersed PMeO₂MA fibers producing miceller‐type aggregates. Dynamic light scattering study indicates an initial decrease followed by sharp increase of Z‐average particle size of PTD with temperature for attaining lower critical solution temperature (LCST) at 20 °C. The LCST increases with OEGMA concentration in PTDO. The temperature dependent PL emission of PTD shows a minimum at 19 °C, followed by a sharp increase till 21 °C, and in the cooling cycle, it shows a complete reversibility. In the PTDO copolymers, the PL intensity shows the hike at progressively higher temperatures due to the increase of LCST with increasing OEGMA concentration. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Towards the Discrimination of Carboxylates by Hydrogen‐Bond Donor Anion Receptors

The binding constants (log K_ass) of small synthetic receptor molecules based on indolocarbazole, carbazole, indole, urea and some others, as well as their combinations were measured for small carboxylate anions of different basicity, hydrophilicity and steric demands, that is, trimethylacetate, acetate, benzoate and lactate, in 0.5 % H₂O/[D₆]DMSO by using the relative NMR‐based measurement method. As a result, four separate binding affinity scales (ladders) including thirty‐eight receptors were obtained with the scales anchored to indolocarbazole. The results indicate that the binding strength is largely, but not fully, determined by the strength of the primary hydrogen‐bonding interaction. The latter in turn is largely determined by the basicity of the anion. The higher is the basicity of the anion the stronger in general is the binding, leading to the approximate order of increasing binding strength, lactate<benzoate<acetate≤trimethylacetate, which holds with all investigated receptors. Nevertheless, there are a number of occasions when the binding order changes with changing of the carboxylate anion, sometimes quite substantially. Principal component analysis (PCA) reveals that this is primarily connected to preferential binding of trimethylacetate, supposedly caused by an additional hydrophobic/solvophobic interaction. These findings enable making better predictions, which receptor framework or cavity is best suited for carboxylate anions in receptor design.     

Development and validation of an RP‐HPLC method for the quantitation of odanacatib in rat and human plasma and its application to a pharmacokinetic study

A simple, specific, sensitive and reproducible high‐performance liquid chromatography (HPLC) assay method has been developed and validated for the estimation of odanacatib in rat and human plasma. The bioanalytical procedure involves extraction of odanacatib and itraconazole (internal standard, IS) from a 200 μL plasma aliquot with simple liquid–liquid extraction process. Chromatographic separation was achieved on a Symmetry Shield RP₁₈ using an isocratic mobile phase at a flow rate of 0.7 mL/min. The UV detection wave length was 268 nm. Odanacatib and IS eluted at 5.5 and 8.6 min, respectively with a total run time of 10 min. Method validation was performed as per US Food and Drug Administration guidelines and the results met the acceptance criteria. The calibration curve was linear over a concentration range of 50.9–2037 ng/mL (r² = 0.994). The intra‐ and inter‐day precisions were in the range of 2.06–5.11 and 5.84–13.1%, respectively, in rat plasma and 2.38–7.90 and 6.39–10.2%, respectively, in human plasma. The validated HPLC method was successfully applied to a pharmacokinetic study in rats. Copyright © 2015 John Wiley & Sons, Ltd.     

Fluorescent Coumarin Derivatives with Viscosity Sensitive Emission - Synthesis,Photophysical Properties and Computational Studies

New derivatives of (benzo[d]azolyl)-benzo[f]chromenone were synthesized from the intermediate 3-(1,3-benzazol-2-yl)naphthalen-2-ol, obtained from 3-hydroxynaphthalene-2-carboxylic acid and 2-amino phenol in the presence of PCl₃ in chlorobenzene at 130–135 °C. The compounds were characterized by FT-IR, ¹ H NMR, mass spectroscopy and elemental analysis. The synthesized compounds are fluorescent which absorb in the range of 296 to 332 nm while emit in the range of 368 to 404 nm. The experimental absorption and emission wavelengths for the compounds 5 and 6 are in good agreement with those predicted using the Time-Dependent Density Functional Theory (TD-DFT) [B3LYP/6-31G(d)]. The largest wavelength difference between the experimental and computed absorption maxima was 29 nm (tetrahedrofuran) for compound 5 while for emission it was 61 nm (dichloromethane) for compound 7. The emission intensities of all the compounds decrease continuously as the viscosity of the microenvironment increases. The compounds are thermally stable up to a temperature range of 300 to 350 °C.     

Role of Dicarboxylate Linkers in MnIII‐Salicylaldoximate Based Extended Structures: Synthesis,Structures, and Magnetic Behavior

Four new oxo‐centered Mn^III‐salicylaldoximate triangle‐based extended complexes [Mn^III₆O₂(salox)₆(EtOH)₄(phda)]_n?(saloxH₂)_n?(2H₂O)_n ( 1 ), [Mn^III₆O₂(salox)₆(MeOH)₅(5‐I‐isoph)]_n?(3 MeOH)_n ( 2 ), [Mn^III₆O₂(salox)₆(MeOH)₄(H₂O) (5‐N₃‐isoph)]_n?(4 MeOH)_n ( 3 ) and [Mn^III₃NaO(salox)₃(MeOH)₄(5‐NO₂‐isoph)]_n?(MeOH)_n (H₂O)_n ( 4 ) [salox=salicylaldoximate, phda=1,3‐phenylenediacetate, isoph=isophthalate] have been synthesized under similar reaction conditions. Single crystal X‐ray structures show that in 1 , only one type of Mn₆ cluster is arranged in 1 D, whereas in 2 and 3 there are two types of clusters, differing in the way the triangle units are joined and assembled. In complex 4 , however, the basic building structure is heteronuclear and based on Mn₃ units extended in 2 D. Susceptibility measurements (dc and ac) over a wide range of temperatures and fields show that the complexes 1 , 2 , and 3 behave as single molecule magnets (SMMs) with S=4 ground state, while 4 is dominantly antiferromagnetic with a ground spin state S=2. Density functional theory calculations have been performed on model complexes to provide a qualitative theoretical interpretation for their overall magnetic behavior.     

Oriented bipartite graphs and the Goldbach graph

In this paper, we study oriented bipartite graphs. In particular, we introduce “bitransitive” graphs. Several characterizations of bitransitive bitournaments are obtained. We show that bitransitive bitounaments are equivalent to acyclic bitournaments. As applications, we characterize acyclic bitournaments with Hamiltonian paths, determine the number of non-isomorphic acyclic bitournaments of a given order, and solve the graph-isomorphism problem in linear time for acyclic bitournaments. Next, we prove the well-known Caccetta-Häggkvist Conjecture for oriented bipartite graphs in some cases for which it is unsolved, in general, for oriented graphs. We also introduce the concept of undirected as well as oriented “odd-even” graphs. We characterize bipartite graphs and acyclic oriented bipartite graphs in terms of them. In fact, we show that any bipartite graph (acyclic oriented bipartite graph) can be represented by some odd-even graph (oriented odd-even graph). We obtain some conditions for connectedness of odd-even graphs. This study of odd-even graphs and their connectedness is motivated by a special family of odd-even graphs which we call “Goldbach graphs”. We show that the famous Goldbach's conjecture is equivalent to the connectedness of Goldbach graphs. Several other number theoretic conjectures (e.g., the twin prime conjecture) are related to various parameters of Goldbach graphs, motivating us to study the nature of vertex-degrees and independent sets of these graphs. Finally, we observe Hamiltonian properties of some odd-even graphs related to Goldbach graphs for a small number of vertices.