Ultrafast Dynamics of New Molecular Photoswitches

Tung T. To and Edwin J. Heilweil

Optical Technology Division, Physics Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Stop 8443, Gaithersburg , MD  20878, USA. 

 

There is great interest in developing high speed reversible molecular photoswitches for optical devices.  Fast rates, high quantum yields, and low fatigue are desirable features.  The current challenge for the application of these novel molecules is that their desirable properties can be hindered by cage processes such as recombination and solvation.  For example, recombination ultimately slows down a reaction since it lowers the quantum yield and thereby requires additional excitation to complete the reaction.  Solvation prolongs the lifetime of transient species and provides more opportunities for side reactions and hence fatigue in molecular devices.  These processes are known to occur on the sub-picosecond timescale and so it is prudent to design the system to have an ultrafast response, attain near unity quantum yield, and control the reaction mechanism which is driven by transient molecular structures and reaction environment.  To reach these goals, we synthetically manipulate molecular structures and use picosecond time-resolved infrared spectroscopy to directly measure their physicochemical responses.  We have synthesized and demonstrated model molecular photoswitches capable of chelation (ring formation of metal-multidentate ligand complexes) to the exclusion of ultrafast solvent coordination and cage recombination in solution.  In this presentation, the chelation dynamics of organomanganese complexes in various reaction environments (in solution and in solid films) will be discussed as well as how ultrafast chelation has been utilized as a mechanistic platform for designing reversible molecular photoswitches. 

 

 

 

 

 

 

 

Left : controlling the reaction pathways by changing the structure of the chelatable ligand, the metal center, and reaction environment.  Right : molecular photoswitches based on ultrafast reversible non-competing chelation.  Strong IR absorption of the M-CO group allows direct measurement of the physicochemical changes in ps timescale using time-resolved infrared spectroscopy.

 

Authors:           Tung T. To

Mentor:            Edwin J. Heilweil

Room #:           B107

Address:           100 Bureau Drive Stop 8443,   Gaithersburg, Maryland 20899-8443

Phone:              301-975-5342,  Email: tung.to@nist.gov, edwin.heilweil@nist.gov

Sigma Xi:          Not members of Sigma Xi

Category:         Chemistry