Photoactive barbiturate receptors: an ultimate lock-and-key system in which the key unlocks the lock.

Conditional photofragmentation is achieved with binary systems incorporating the isophthaloyl bis-aminopyridine barbiturate recognition motif and dithiane- or trithiane-based photolabile modules, which cleave only in the presence of an external sensitizer. The components of the host-guest molecular recognition pair were each outfitted with either the sensitizer or the photocleavable module. In these pairs, photoinduced fragmentation is contingent on a molecular recognition event, which brings the sensitizer into the immediate proximity of the photolabile latch. [structure: see text]