Photophysics of multicomponent molecules under dynamic control

Abstract

This work focusses on seeking to gain a deep understanding of the photophysical processes inherent to multi-functional and/or multi-component supermolecules in the condensed phase. To do this, a variety of molecular systems have been subjected to spectroscopic examination, most commonly using steady-state and time-resolved emission spectroscopy to interrogate the samples. A common feature of all the molecular architectures examined herein relates to the possibility for structural motion on timescales of concern to the photophysical event. Furthermore, to provide a spectroscopic signature, most of the target dynamic systems comprise a donor covalently attached to a complementary acceptor. These systems possess the potential to be used as solar-energy concentrators or for specific sensing applications. However, attention is given only to the fundamental properties. Chapter 1 provides a general introduction to the field of molecular rotors and to the concepts of energy and electron transfer in molecular systems. Key literature examples are used to illustrate the current state-of-the-art and to set the tone for later discussions. Each chapter includes a brief introduction to the specific topic under discussion while avoiding the generic details covered in the main introduction. The essential experimental details and underlying analytical protocols for all the studies described are provided in the final chapter. Chapter 2 describes a new series of molecular rotors based on the boron dipyrromethene (BODIPY) structure. This series includes structurally-similar compounds that exhibit surprisingly disparate behaviours as putative probes for solvent viscosity. In fact, the results tend to challenge the conventional understanding of BODIPY-based molecular probes. In this chapter, we highlight the importance of asymmetry, question how it might be used to one’s advantage in the design of next generation probes, and raise ideas about porosity of the excited-state potential energy surface.