The First Normal-Phase High-Performance Thin-Layer Chromatographic Method for the Simultaneous Determination of the Antimalarial Drugs Atovaquone and Proguanil from Malarone® Tablets

JPC – Journal of Planar Chromatography – Modern TLC -     

Photovoltaic response to structural modifications on a series of conjugated polymers based on 2‐aryl‐2H‐benzotriazoles

The synthesis, characterization, and photovoltaic properties of a series of four conjugated polymers containing 2‐aryl‐2H‐benzotriazoles and “bis(thiopheno)dialkylfluorenes” is described. The polymers were obtained via Suzuki‐polycondensation and comprise alternating electron rich and electron poor building blocks. The impact of systematic structural changes on the electronic and morphological properties and device efficiencies were studied. Application of these polymers as light‐harvesting and electron‐donating materials in organic solar cells using PCBM derivatives as electron accepting materials resulted in power conversion efficiencies up to 1.8%. Both the properties of the pristine polymers and the device performance show that the impact of the substitution farther‐off the backbone is negligible while substitution directly on the backbone has a major impact. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Optimal Control and Geodesics on Quadratic Matrix Lie Groups

The purpose of this paper is to extend the symmetric representation of the rigid body equations from the group SO (n) to other groups. These groups are matrix subgroups of the general linear group that are defined by a quadratic matrix identity. Their corresponding Lie algebras include several classical semisimple matrix Lie algebras. The approach is to start with an optimal control problem on these groups that generates geodesics for a left-invariant metric. Earlier work by Bloch, Crouch, Marsden, and Ratiu defines the symmetric representation of the rigid body equations, which is obtained by solving the same optimal control problem in the particular case of the Lie group SO (n). This paper generalizes this symmetric representation to a wider class of matrix groups satisfying a certain quadratic matrix identity. We consider the relationship between this symmetric representation of the generalized rigid body equations and the generalized rigid body equations themselves. A discretization of this symmetric representation is constructed making use of the symmetry, which in turn give rise to numerical algorithms to integrate the generalized rigid body equations for the given class of matrix Lie groups. Dedicated to Professor Arieh Iserles on the Occasion of his Sixtieth Birthday.     

Orthogonally functionalizable copolymers based on a novel reactive carbonate monomer

A novel N‐hydroxy succinimide‐based carbonate monomer that allows direct synthesis of polymers incorporating a reactive carbonate group in the side chain was synthesized. This new monomer was copolymerized with methyl methacrylate and poly(ethylene glycol) methylether methacrylate using free‐radical polymerization to obtain organo‐ and water‐soluble reactive copolymers. Copolymerization of the activated carbonate monomer with an azide‐containing monomer and N‐hydroxy succinimide‐containing activated ester monomer provided orthogonally functionalizable copolymers. The pendant reactive carbonate groups of the copolymers were functionalized with amines to obtain carbamates. Polymers capable of orthogonal functionalization could be selectively functionalized as desired using subsequent 1,3‐dipolar cycloaddition or amidation reactions. The novel monomer and the copolymers were characterized by ¹H‐NMR, ¹³C‐NMR, and infrared spectroscopy. The efficient stepwise orthogonal functionalization of the copolymers were examined via ¹H‐NMR spectroscopy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

On the Alkylation of 5-Fluorouracil-Some Recent Findings

Since its discovery 5-fluorouracil ¹(1,5-FU), an important anticancer drug, has been the subject of study for the preparation of some suitable derivatives² which may have better therapeutic efficacy. These are prepared through silylation method³, mercuri salt method⁴ and direct alkylation method⁵ of 5-FU. It was reported⁵ that the direct alkylation of 5-FU with saturated and allylic type halides under controlled conditions occur at N₃ (3-) and N₁ (1-) position respectively in contrast to alkylation of uracil where N₁ alkylated products are obtained in both cases. The position of alkylation in 5-FU was determined, with analogy from uracil⁶, by the bathochromic shift in UV from the neutral pH to alkaline pH of the 3-substituted product compared to no such shift of the 1-substituted product.     

Order-disorder transitions: structural and magnetic ordering in double perovskites

Using an effective lattice gas-like model for B-B′ site ordering we study order-disorder transitions in double perovskite materials A₂BB′O₆. We motivate this effective model from a microscopic hamiltonian. Using this model, we are able to address several experimentally observed issues including nonmonotonic dependence of the degree of order on annealing temperature, and the rapid decrease of order upon overdoping with either B or B′ species. We also study ordering in the ‘ternary’ compounds A₂BB′_1−yB″_yO₆, using a variant of the Blume-Emery-Griffiths model. Several issues related to structural and magnetic ordering are discussed.