Abstract:
The incorporation of boron into conjugated organic molecules has emerged as a useful strategy to elicit interesting optical and electronic properties which cannot be obtained with the analogous all-carbon systems. Thus, the synthesis of organoboron heterocycles has been a topic of intense investigation. Research in the Gilliard laboratory combines various aspects of contemporary main-group chemistry and molecular materials chemistry. Our primary goal has been to isolate molecules in rare electronic states and to provide a link between structure and function. We have synthesized, structurally characterized, and assessed the aromaticity and optical properties of unusual borafluorene cations, radicals, and anions. Photolysis of the boraphosphaketene led to the aromatic BP-phenanthryne. We have now initiated efforts aimed at understanding the chemical reactivity of these 5- and 6-membered boron-containing rings. More recently, we discovered that borenium ions are viable stimuli-responsive materials, possessing thermo-chromic and/or -luminescent properties. In addition to reduced borafluorenes, we have isolated electronically distinct borepin radicals and anions (i.e., 7-membered boron-containing rings). While the anions would formally be 8π electron anti-aromatic systems, the unique non-planar boat-shaped confirmation results in non-aromatic molecules. This lecture will cover our most recent results in these research areas.