Triplet states of oligomeric axially bridged ruthenium phthalocyanines
The photophysical properties of a soluble oligomeric ruthenium phthalocyanine in which the macrocycles are axially linked through a bidentate bridging ligand are reported and compared with that of a monomeric analogue. The triplet states have been characterized by time-resolved absorption spectroscopy. From the decay kinetics, studied as a function of the number of triplet states per oligomeric chain, it is deduced that triplet migration is not efficient in the oligomeric chains. At high excitation intensities, direct triplet–triplet annihilation, which is not diffusion-limited, is observed. Triplet–triplet interactions are probably effective at distances of at least 24 Å.