Self-Assembly of Luminescent Molecular Squares Featuring Octahedral Rhenium Corners

A new family of molecular squares containing ReI polypyridyl and polypyrazyl centers has been synthesized at quantitative yields via a self-assembly method. Ambient-temperature photophysical studies reveal that two of the squares (4,4‘-bipyridine- and pyrazine-bridged species) readily luminesce in solution from relatively long-lived charge-transfer excited states. These squares expand the growing field of inorganic cyclophane self-assembly chemistry to the octahedral metal systems.