Exploring the Excited States of a Hexa-peri-hexabenzocoronene-Substituted Dipyridophenazine Ligand and Its Metal Complexes

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.

Automated summary

Spectroscopy was used to study the excited states of chromophore-connected HBC-dppz complexes with rhenium(I) and ruthenium(II). The HBC-substituted dppz ligand and its corresponding complexes were synthesized and characterized. The interplay of their excited states and the perturbation of the HBC were investigated. These studies provide insight into the design of polyaromatic systems and contribute to the knowledge of dppz systems.