Excited state dynamics of shape-shifting molecules

Molecules that change shape (isomerise) in response to light are essential in numerous light-controlled technological applications including optical memory registers, advanced materials and nanotechnological molecular machines capable of performing specific tasks at the microscopic level. In addition to their technological applications, shape-changing 'photoswitch' molecules have widespread biological importance, including roles in vision, phototropism and photosynthesis in bacteria, and ion channel switches. The shape-shifting properties of these photoswitch molecules stems from the existence of two or more distinct isomers that can be toggled following exposure to different colours of light. Each isomer may have unique properties, including molecular volume, colour, solubility, and conductivity.

Improving our molecular-level understanding of the actinic mechanistic details of photoswitching - the so-called excited state dynamics - is critical for the rational design of improved derivatives. Harnessing this knowledge is becoming increasingly important due to the widespread adoption of photoswitches into everyday life, requiring new spectroscopic methodologies that offer increased selectivity and information content. In particular, the spectroscopic toolkit must have the capacity to independently probe the excited state dynamics associated with each isomer, which invariably occurs over the ultrafast femtosecond (0.000000000000001 second) timescale, and also the capacity to characterise branching to multiple photoswitch forms or degradation pathways. It is often difficult or impossible to characterise the inherent photoswitching properties of each isomer using conventional analytical or physical chemistry techniques, particularly when there are several isomers, rapid interconversion and strong environmental influences. This research program will develop new vacuum-based instrumentation and methodology to help address these deficiencies and will focus on applying the toolkit to characterising two classes of molecular photoswitches important in optoelectronics and optical control of biotechnological molecules.

Building on our unique expertise gained from multiple world-leading laboratories, this research program will establish long-term research infrastructure in the UK, permitting study of shape-selected molecules and their ultrafast shape-shifting dynamics. The instrumentation and methodology will provide a distinctive new approach and offer end capabilities that are not possible by any other single research group.