When
Presenter:
Dr. Chris Bardeen
Professor
Department of Chemistry
University of California, Riverside
Abstract:
Molecular crystals are often thought of as static and fragile entities, but there is now a growing body of work showing that they can exhibit dynamic mechanical behavior in response to heat or light. We will describe our work in the area of photomechanical crystals, where the mechanical response is driven by photochemical reactions of the constituent molecules. Examples include crystalline 4-fluoro-9-anthracenecarboxylic acid, which undergoes a [4+4] photodimerization that can be reversed by thermal fluctuations. This “negative” photochromic reaction proceeds in a spatially cooperative nature and allows discrete regions of the crystal to be expanded using structured light. We show how this property can be used to demonstrate reconfigurable optical elements. In contrast, divinyl anthracenes undergo an E-Z photoisomerization that can only be reversed by light. Under the right conditions, the competing E-Z and Z-E isomerizations can give rise to oscillatory reaction and mechanical dynamics. Under a steady-state light source, these systems avoid equilibrium and act as light powered molecular crystal motors.
Bio:
Prof. Bardeen received his B.S. in chemistry from Yale University in 1989 and a Ph. D. in chemistry from UC Berkeley in 1995 under Charles V. Shank. He became an assistant professor at U. Illinois, Urbana-Champaign in 1998 and moved to the Chemistry Department at UC Riverside in 2005. He is a physical chemist who uses laser spectroscopy and microscopy to study light-induced dynamics in solid-state organic materials. Awards include the Camille and Henry Dreyfus New Faculty Award, the 3M Non-Tenured Faculty Award, the Research Corporation Research Innovation Award, the National Science Foundation CAREER Award, and a Sloan Research Fellowship.
Hosted by: Dr. Vanessa Huxter