Professor, Chemistry Department
Photochromic materials reversibly change color upon irradiation. The most well know application is "Transition Lenses". The change in color is most often based on the rearrangement between two isomers (isomerization). We design photochromes based on a linkage isomerization, the migration of a metal center between two atoms or functional groups of a ligand. (Figure 1). Several factors are important in useful photochromes: color difference between isomers, isomerization yield per photon, rate of isomerization, and the nature and rates of competing reactions and processes. To eliminate processes that are unproductive, optimization of ligand structures for linkage isomerization is critical. Our current research investigates functional groups and their relative positions that favor linkage isomerization. This information will also be valuable for the development of optically driven molecular devices.
A photochrome based on an ultrafast linkage isomerization would be a major step in eliminating competing processes that cause photochrome fatigue. While a great deal of research has been carried out, photochromic materials have had marginal commercial development. Photochromes have been reported for applications in information processing and data storage with the development of optical switches optical memories, three-dimensional data storage, and holography recording. Development has begun in microfabrication, wettability of surfaces (for microfluidic devices), and volume changes (for photoactuators). Practical application will almost certainly require functioning in the solid state. Figure 2 demonstrates that a 1,4 linkage isomerization readily occurs in a polymer matrix.
Charles B. Duke III, Roger G. Letterman, Jermaine O. Johnson, James W. Barr, Songnan
Hu, Charles R. Ross II,Charles Edwin Webster, and Theodore J. Burkey, "Photochemistry
of Arene Chromium Tricarbonyl Complexes with Tethered Pyridinyl and Propenyl Groups:
Investigations of Chelate Formation, Structure, and Linkage Isomerization" Organometallics,
2014, 33, 485-497. dx.doi.org/10.1021/om400928k
Roger G. Letterman, Charles B. Duke III, Tung T. To, Theodore J. Burkey, and Charles Edwin Webster, "Degenerate Pathways for Metallacycle Ring Inversions: A Common Phenomenon Consistent with the Principle of Microscopic Reversibility" Organometallics, 2014, 33, 5928-5931. dx.doi.org/10.1021/om5007165.
Kristy M. DeWitt, Tung T. To, Edwin J. Heilweil†, Theodore J. Burkey "Linkage Isomerization via Geminate Cage or Bimolecular Mechanisms: Time-Resolved Investigations of an Organometallic Photochrome" J. Phys. Chem. A, 2015, 119, accepted for publication. 2/2015.