Screening Nanographene‐Mediated Inter(Porphyrin) Communication to Optimize Inter(Porphyrin–Fullerene) Forces

Abstract

Multifunctional molecular materials comprising porphyrins and fullerenes have served as perfect prototypes to study key aspects of natural photosynthesis starting at light harvesting and energy transfer processes all the way to charge separation, charge shift, and charge recombination. Herein, hexa‐peri‐hexabenzocoronenes (HBCs) are explored, decorated with one, two, and six porphyrins at their peripheral positions, within the context of replicating key steps of photosynthesis. The major focus of the investigations is to screen inter(porphyrin) communications across the HBC platform as a function of the substitution pattern and to optimize the intermolecular forces with fullerenes. To this end, the ground‐ and excited‐state features are investigated in the absence of C60 and C70 by employing an arsenal of spectroscopic methods. Further insights into inter(porphyrin) communications come from time‐dependent density‐functional theory (TDDFT) calculations. In the presence of C60 and C70, X‐ray crystallography, steady‐state and time‐resolved spectroscopy, and mass spectrometry corroborate exceptionally strong inter(porphyrin–fullerene) interactions in the solid, liquid, and gas phases. The experiments are backed‐up with DFT calculations of the geometrically optimized and energetically stable complex configuration.

Recent advances in supramolecular fullerene chemistry

“…368,369 p-Extended nanographenes with suitably sized cavities have also been utilized as hosts for fullerenes. [370][371][372] For example, Wang and coworkers reported a Janusarene 61, 342 possessing nineteen phenyl rings (seven constituting the hexaphenylbenzene core and the other twelve forming a ''fence'' around the two faces of the core), which was synthesized via an efficient cobalt-catalyzed cyclotrimerization of alkyne precursors. Hostguest complexation of 61 and C 60 was supported by SCXRD, which revealed a ratio of 1 : 1 in the solid state.…”

Anti-Dissipative Strategies toward More Efficient Solar Energy Conversion

“…Upon excitation and ISC, vibrationally hot 3 MLCT­(L p ) relaxed to the thermally equilibrated 3 MLCT­(L p ) in less than 10 ps, typical for VR processes in [Ru­(bpy) 3 ] 2+ and other ruthenium polypyridine chromophores. ,− Electronic coupling between the different excited states was strong, and it favored an efficient IC without any significant kinetic barriers (Figure , top), leading to the population of the lowest triplet state in a few picoseconds, like in [Ru­(bpy) 3 ] 2+ . Observations involving a variety of intramolecular donor/bridge/acceptor processes, ranging from singlet fission to ground- and excited-state intervalence charge transfers, ,− revealed that para connectivity promotes stronger electronic coupling than meta connectivity, suggesting that the topology of the bridge can be exploited to modulate excited-state electronic coupling. , Therefore, we hypothesized that the meta topology of the bridge in D m could lead to poor electronic coupling and thus to an anti-Kasha scenario, fulfilling the requirements for an anti-dissipative photosensitizer/photocatalyst. Thus, we sought to explore the IC/VR dissipative pathways of D m , by means of TAS in the femtosecond (fsTAS) and nanosecond (nsTAS) ranges.…”

Probing Charge Management across the π-Systems of Nanographenes in Regioisomeric Electron Donor–Acceptor Architectures

“…19,32−38 In, e.g., multiporphyrinic HBC conjugates, the interporphyrinic communication was found to be mediated by the HBC backbone and the resulting geometry. 38 In the current systems, the peripheral positions of the HBCs are utilized to study the electron transfer interactions between (metallo)porphyrins and fullerenes one step ahead. We decorated the HBC platform with ZnP and C 60 to obtain geometrical isomers with electron donors and acceptors positioned in ortho-, meta-, and para-positions to each other (Figure 1A).…”

“…Hexa- peri -hexabenzocoronenes (HBCs) have recently attracted increasing attention due to their unique optoelectronic properties and the possibilities to utilize/tune or functionalize them. Multiple publications document the properties of HBCs regarding photon and charge management, as well as electronic communication. − Noteworthy is the efficient coupling between HBCs and porphyrins. ,− In, e.g., multiporphyrinic HBC conjugates, the interporphyrinic communication was found to be mediated by the HBC backbone and the resulting geometry …”