PHYS 337 |
| Elimination of undesirable side reactions to increase quantum yields and reaction rates is a challenge for developing reversible molecular photoswitches for optical devices. In this study, a series of model molecular photoswitches, organomanganese ((η5-C5H4R)Mn(CO)3) and organochromium ((η6-C6H5R)Mn(CO)3) complexes with pendant chelatable functional groups were synthesized and their ultrafast chelation dynamics in various reaction environments (heptane, acetonitrile, THF, polyacrylonitrile solid polymer film) were investigated using time-resolved infrared spectroscopy. Chelation occurs via two reaction pathways: 1) direct sub-100 ps chelation where photodissociation of a CO ligand results in immediate coordination of the chelatable functional group; 2) indirect >100 ns solvation pathways where photodissociation of a CO ligand results in formation of a solvated intermediate which converts to the final stable chelated product. The chelation pathways and rates were controlled by synthetically modifying the structure of the R group, using different metal centers, and changing the reaction environment. Chelation to the exclusion of side reactions, including cage recombination and solvation in solution and matrix cage effects in solid polymer films was successfully demonstrated. This study shows that chelation can be used as mechanistic platform for designing high quantum yield, high speed, and high fatigue resistant reversible molecular photoswitches for optical devices. |
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PHYS Poster Session - Optical Probes of Dynamics in Complex Environments
7:30 PM-10:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- Hall A, Poster
Division of Physical Chemistry |