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Biomedical subjects

Neil R Brooks

Publications and source records attributed to Neil R Brooks.

7 recordsLinked to original sources
PubMed2003

Single-crystal structures of polymer electrolytes.

The mechanisms by which ions are transported through polymer electrolytes are poorly understood. Structural information should greatly aid in the determination of such mechanisms and the optimization of the electrolyte properties. Ionic conductivity, however, predominates in amorphous polymer-salt phases, and characterization of amorphous solvate structures is difficult. The task is simplified by comparisons with crystalline poly(ethylene oxide) (PEO)-salt phases, but the structural determination of such phases is also difficult because single crystals have not been available. Here, it is demonstrated that single crystals of PEO-lithium salt phases may be prepared and characterized using low molecular weight PEO.

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PubMed2003

Crystals from concentrated glyme mixtures. The single-crystal structure of LiClO4.

A procedure for the preparation of high-quality single crystals from concentrated glyme mixtures is presented. Anhydrous single crystals of LiNO(3) and LiClO(4) were prepared in this manner, and the single-crystal structure of LiClO(4) (orthorhombic, Pnma, a = 8.6447(12) A, b = 6.8512(10) A, c = 4.8254(7) A, Z = 4) was determined as an example. This procedure is expected to be widely applicable for not only salts but also a wide range of other materials solvated by glymes.

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PubMed2003

Derivatization, complexation, and absolute configurational assignment of chiral primary amines: application of exciton-coupled circular dichroism.

We report here a sensitive method for the determination of the absolute configurations of primary amines using exciton-coupled circular dichroism (ECCD). The method works on a microgram scale by derivatization of chiral amines with quinoline chromophores. Complexation of the chiral ligands with metal ion fixes the geometry of the chromophores, resulting in a twist that is governed by the asymmetric carbon configuration and steric environment of the amine. The absolute configurations of the primary amines can be interpreted from the couplets of the ECCD spectra of the derivatized complexes. Crystal structures, 2D NMR studies, and semiempirical calculations provide structural evidence for our model.

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PubMed2002

Stereoselective Stobbe condensation of ethyl methyl diphenylmethylenesuccinate with aromatic aldehydes.

The E configuration of benzylidene(diphenylmethylene)succinic anhydride (R = H), obtained by the Stobbe condensation of ethyl methyl diphenylmethylenesuccinate with benzaldehyde, was determined by single-crystal X-ray diffraction. Noncovalent pi stacking interaction between two stacked phenyl groups is suggested as a stabilizing energy for the highly crowded molecule. The nature and the position of substituents (R) on the aromatic rings of substituted benzaldehydes showed no effect on the E stereoselectivity in the condensation. [structure: see text]

Journal Article↗
PubMed2002

Li+ cation coordination in [Li2(CF3SO3)2(diglyme)] and [Li3(C2F3O2)3(diglyme)].

The title compounds, poly[[[bis(2-methoxyethyl) ether]lithium(I)]-di-mu(3)-trifluoromethanesulfonato-lithium(I)], [Li(2)(CF(3)SO(3))(2)(C(6)H(14)O(3))](n), and poly[[[bis(2-methoxyethyl) ether]lithium(I)]-di-mu(3)-trifluoroacetato-dilithium(I)-mu(3)-trifluoroacetato], [Li(3)(C(2)F(3)O(2))(3)(C(6)H(14)O(3))](n), consist of one-dimensional polymer chains. Both structures contain five-coordinate Li(+) cations coordinated by a tridentate diglyme [bis(2-methoxyethyl) ether] molecule and two O atoms, each from separate anions. In both structures, the [Li(diglyme)X(2)](-) (X is CF(3)SO(3) or CF(3)CO(2)) fragments are further connected by other Li(+) cations and anions, creating one-dimensional chains. These connecting Li(+) cations are coordinated by four separate anions in both compounds. The CF(3)SO(3)(-) and CF(3)CO(2)(-) anions, however, adopt different forms of cation coordination, resulting in differences in the connectivity of the structures and solvate stoichiometries.

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