Bicyclic Diphosphines Flip Inside Out | June 13, 2011 Issue - Vol. 89 Issue 24 | Chemical & Engineering News
Volume 89 Issue 24 | p. 33 | Concentrates
Issue Date: June 13, 2011

Bicyclic Diphosphines Flip Inside Out

Chemists identify a rare case of isomerism in which a cagelike macromolecule turns itself inside out
Department: Science & Technology
Keywords: isomerization, phosphine, chemical dynamics, host-guest interactions
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MOLECULAR CONTORTIONIST
In this schematic representation, a dibridgehead diphosphorus molecule transitions through different configurations as the molecule turns itself inside out.
Credit: Angew. Chem. Int. Ed.
Graphical_Abstract_3
 
MOLECULAR CONTORTIONIST
In this schematic representation, a dibridgehead diphosphorus molecule transitions through different configurations as the molecule turns itself inside out.
Credit: Angew. Chem. Int. Ed.

In chemistry that contortionists can relate to, a research team led by Michael Stollenz and John A. Gladysz of Texas A&M University has identified a rare case of isomerism in which a macromolecule turns itself inside out (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201100893). By careful study of 31P NMR spectra, the researchers discovered that the alkyl chains of a cagelike bicyclic diphosphine, made up of two phosphorus atoms linked by three (CH2)14 chains, can reversibly slide between one another to invert the molecule, flipping over the phosphorus atoms and interconverting three configurational isomers. The researchers designate these isomers as in/in, out/out, and in/out, depending on whether each phosphorus atom’s lone pair of electrons is facing into or out of the molecular cage. This type of isomerization might be a general mechanism for encapsulating atoms or molecules that has been overlooked, Gla dysz says. It could be useful for controlled sequestration, transport, and delivery of guest molecules that bind to the phosphorus lone pairs, he suggests.

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INSIDE AND OUT
Gladysz and coworkers' dibridgehead diphosphine molecule exists as three in/out isomers based on the orientation of each phosphorous atom's lone pair of electrons.
Credit: Angew. Chem. Int. Ed.
8924scicon3600_live
 
INSIDE AND OUT
Gladysz and coworkers' dibridgehead diphosphine molecule exists as three in/out isomers based on the orientation of each phosphorous atom's lone pair of electrons.
Credit: Angew. Chem. Int. Ed.
 
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