Abstract
Spectroscopy reveals that chromophore-connected hexa-peri-hexabenzocoronene (HBC) dipyridophenazine (dppz) complexeswith rhenium(I) and ruthenium(II) have a lowest excited state thatis localized on the HBC. These excited states lie in the microsecondregime.
A hexa-peri-hexabenzocoronene (HBC)-substituteddipyridophenazine (dppz) ligand (dppz-HBC) and its corresponding rhenium[Re(CO)(3)Cl] and ruthenium [Ru(bpy)(2)](2+) complexes were synthesized and characterized. The interplay of theirvarious excited states was investigated using spectroscopic and computationaltechniques. Perturbation of the HBC was seen through a broadeningand decreased intensity of the HBC absorption bands that dominatethe absorption spectra. A delocalized, partial charge transfer statewas shown through emission (520 nm) in the ligand and rhenium complexand is supported by time-dependent density functional theory calculations.Transient absorption measurements revealed the presence of dark stateswith a triplet delocalized state populated in the ligand, while inthe complexes, longer-lived (2.3-2.5 & mu;s) triplet HBCstates could be accessed. The properties of the studied ligand andcomplexes provide insight into the future design of polyaromatic systemsand add to the rich history of dppz systems.