Preparation and Photophysical Properties of Molecular Architectures Composed of Polycyclic Aromatic Hydrocarbon and Porphyrin Derivatives

The self-assembly of organic molecules to form ordered nanoarchitectures is currently receiving great interest as a means of constructing well-defined nanostructures. The possibility for controlling macroscopic structures through a proper choice of the molecular components paves a way to design and synthesize materials with specific properties and functions. One of the main challenges is the consturction of highly organized supramolecular multicomponent nanostructures in a well-controlled manner, which is very related to the molecular systems of natural photosynthesis highly organized in quaternary protein structures. Therefore, utilization of electron donor (D) and acceptor (A) molecules such as polycyclic aromatic hydrocarbon derivatives (PAHs) (e.g., perylene and coronene) for controlled assembly has stimulated the related research fields such as molecular electronics and light energy conversion.^1-3

Disc-like PAH derivatives such as triphenylene functionalized with alkyl chains, which self-assemble into supramolecular structures due to the stacking π−πinteractions, may be a good candidate to construct face-to-face complexes with planar dye molecules. In this context, 1,4,5,8,9,12-hexaazatriphenylene (HAT) derivatives are good electron acceptors since these molecules have the electron deficient pyrazine units.

Along this point, planar porphyrins and 1,4,5,8,9,12-hexaazatriphenylene (HAT) derivatives are expected to form supramolecular charge-transfer (CT) π-complexes, exhibiting broad CT absorption bands. The redox properties of porphyrins and HAT derivatives measured by electrochemical measurements indicate that porphyrins and HAT derivatives act as electron donors and acceptors, respectively. The 1 : 1 CT complexes between porphyrins and HAT derivatives was successfully examined by the UV-vis, fluorescence and ¹H NMR measurements. The occurrence of ultrafast photoinduced electron transfer from the porphyrin unit to the HAT unit was confirmed by transient absorption measurements. Finally, highly one-dimensional assembly composed of porphyrin and an HAT derivatives was observed by transmission electron microscope (TEM) and atomic force microscope (AFM).

Additionally, the related molecular architectures containing fullerene derivatives will be also discussed in this presentation.

References

(1)  Hirayama, S.; Sakai, H.; Araki, Y.; Tanaka, M.; Imakawa, M.; Wada, T.; Takenobu, T.; Hasobe, T. Chem. Eur. J. 2014, 20, 9081.

(2)  Ida, K.; Sakai, H.; Ohkubo, K.; Araki, Y.; Wada, T.; Sakanoue, T.; Takenobu, T.; Fukuzumi, S.; Hasobe, T. J. Phys. Chem. C 2014, 118, 7710.

(3)  Sakai, H.; Shinto, S.; Araki, Y.; Wada, T.; Sakanoue, T.; Takenobu, T.; Hasobe, T. Chem. Eur. J. 2014, 20, 10099.