Tagged Metals Are Ready To Star in Action Movies

A new family of fluorescent compounds may enable transition-metal-catalyzed reactions to be imaged at the single-molecule level, according to a study by Stephen M. Canham, Suzanne A. Blum, and coworkers at the University of California, Irvine (Organometallics, DOI: 10.1021/om800228v). The advance may lead to novel procedures for probing catalytic reaction mechanisms as well as insights into designing catalysts. The compounds, which are based on dipyrromethene boron difluoride (BODIPY, shown), serve as fluorescent tags by forming complexes with catalytic metal centers. These complexes can be monitored as individual bright spots via single-molecule fluorescence microscopy (SMFM). Until now, SMFM has generally been limited to investigations of biological systems or has been applied in ways that require the fluorescent tag to undergo a specific type of chemical reaction in order to image the tagged species. The UC Irvine group has broadened the reach of SMFM by synthesizing amine, alcohol, and other BODIPY derivatives and using them to tag and probe individual palladium(II) complexes. The group is in the process of applying the method to other transition-metal complexes and developing methods to image individual bond-forming events.