Speaker: Dr. John Gladysz, Texas A&M University
Title: “From Molecular Gyroscopes to Homeomorphic Isomerization: Molecules that Turn Themselves Inside-Out”
Abstract: Children never cease to be fascinated by toy gyroscopes, which commonly consist of (1) a rotating axis and disk, and (2) two to four spokes that connect the termini of the axis. This talk will describe syntheses of molecules that duplicate the connectivity, symmetry, and rota­tional ability of such gyroscopes. Complexes with trans R3P-MLn-PR3 linkages are first pre­pared, with R groups that terminate with a CH=CH2 moiety. Then alkene metathesis followed by hydrogenation is used to construct three-spoked cage molecules. Square planar, trigonal bipyramidal, and octahedral systems can be prepared.

Certain complexes can be demetallated to yield dibridgehead diphosphines, which can exist as three stereoisomers (phosphorus lone pairs in/in, out/out, or in/out). This provides a starting point for another very interesting story. It has proved possible to show that these molecules rapidly turn themselves "inside-out" by a dynamic process that has rarely been observed previously. These topologically novel equilibria interconvert what any chemist would regard as two configurational diastereomers by purely conformational processes.

The Chemistry and Biochemistry Departmental Seminar Series covers a broad range of fields in the Chemical and Biochemical Sciences. In past seminars, scientists from Academia, Government, and Industry have presented their most recent discoveries and contributions in their respective areas. This Seminar Series offers students and faculty the opportunity to interact directly with other leaders in their specializations and to gain a good overview of the entire range of fields in Chemistry and Biochemistry.