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Biomedical subjects

Leonard J Barbour

Publications and source records attributed to Leonard J Barbour.

At least 19 recordsLinked to original sources
PubMed2006

Crystal porosity and the burden of proof.

The study of porosity in the context of crystal engineering is rapidly growing in intensity. However, claims of porosity are often highly subjective and use of the term "porous" is susceptible to abuse. This contribution discusses some of the criteria to be considered when stating that a particular crystal structure is porous.

Journal Article↗
PubMed2006

Permeability of a seemingly nonporous crystal formed by a discrete metallocyclic complex.

We describe the structure and permeability of a crystalline material that appears to be nonporous in a conventional sense. The material is initially formed as a solvate, and removal of the solvent molecules under relatively mild conditions proceeds via a single-crystal to single-crystal transformation, leaving the host structure intact. Although discrete unoccupied voids of 108 A3 are present in the structure, it is not possible to map open channels that represent an intuitive pathway for guest diffusion. Despite the apparent absence of pores, the material is permeable to a variety of gases including H2, O2, N2, CO, CH4, CO2, and I2. These findings show that porosity in crystalline systems cannot always be rationalized by considering the static structures and that as-yet unknown dynamic and cooperative mechanisms prevail by which porosity can be induced.

Journal Article↗
PubMed2005

A discrete metallocyclic complex that retains its solvent-templated channel structure on guest removal to yield a porous, gas sorbing material.

A discrete rectangular metal-organic complex that stacks to form one-dimensional channels filled with acetonitrile solvent molecules is described. Removal of the solvent under relatively mild conditions proceeds via a single-crystal to single-crystal transformation that leaves the host lattice unaltered. These findings proffer a design strategy for porous materials based on the simple principle that rigid molecular rings cannot pack efficiently and would thus favor the inclusion of guest species whenever possible. Upon guest removal, an efficiently packed new phase can then only be achieved by means of bond cleavage. Thus, achieving crystal porosity by maintaining robust metal-ligand coordination bonds in such discrete cyclic systems directly parallels the strategy employed for MOFs.

Adsorption↗
PubMed2005

Crystal engineering of nonporous organic solids for methane sorption.

The low density polymorph of the well-known host p-tert-butylcalix[4]arene absorbs more methane than p-tert-pentylcalix[4]arene at room temperature and 1 atm pressure, but the order of absorption is reversed at 38 atm with p-tert-pentylcalix[4]arene absorbing more.

Journal Article↗
PubMed2004

Toward mimicking viral geometry with metal-organic systems.

Icosahedral and cuboctahedral arrangements of calixarenes, a nanometer-scale, spheroidal assembly of 12 calixarene molecules, can be manipulated in a highly controlled fashion. Previously, such assemblies were observed to favor placement of the calixarenes at the vertexes of an icosahedron. A supramolecular constraint is employed in order to enforce molecular alignment and produce a cuboctahedral arrangement. The internal volume of the cuboctahedron is approximately 30% greater than that of the icosahedron. Furthermore, in stark contrast to that of the icosahedral Platonic solid, the shell of the cuboctahedral Archimedean solid is porous.

Biomimetic Materials↗