Side-to-Face Ruthenium Porphyrin Arrays. Photophysical Behavior of Dimeric and Pentameric Systems

The investigated systems are side-to-face porphyrin arrays made of two types of molecular components: a porphyrin unit with meso-pyridyl substituents, and one or more ruthenium carbonyl tetraphenylporphyrin units. The two types of unit are assembled by axial coordination of the meso-pyridyl groups of the former onto the metal center of the latter. The number (one or four) of the meso-pyridyl groups on the axial unit determines whether the arrays are dimeric or pentameric. The geometry of the groups (4′-pyridyl or 3′-pyridyl) determine whether the arrays have perpendicular or canted structures. Furthermore, the meso-pyridyl porphyrin can be either free-base or zinc-substituted, leading to a total of eight different arrays. All arrays were shown to be stable in toluene, even in the dilute solutions (1×10-5 M) required for photophysical experiments. The energy levels of the molecular components are practically unaltered in the arrays, with the excited states of the ruthenium porphyrin uni...