Nanographene‐Based Decoration as a Panchromatic Antenna for Metalloporphyrin Conjugates

Abstract

Porphyrins, a type of heterocyclic aromatic compounds consisting of tetrapyrroles connected by four substituted methine groups, are appealing building blocks for solar energy applications. However, their photosensitization capability is limited by their large optical energy gap, which results in a mismatch in absorption toward efficient harvesting of the solar spectrum. Porphyrin π‐extension by edge‐fusing with nanographenes can be employed for narrowing their optical energy gap from 2.35 to 1.08 eV, enabling the development of porphyrin‐based panchromatic dyes with an optimized energy onset for solar energy conversion in dye‐sensitized solar fuel and solar cell configurations. By combining time‐dependent density functional theory with fs transient absorption spectroscopy, it is found that the primary singlets, which are delocalized across the entire aromatic part, are transferred into metal centred triplets in only 1.2 ps; and subsequently, relax toward ligand‐delocalized triplets. This observation implies that the decoration of the porphyrin moiety with nanographenes, while having a large impact on the absorption onset of the novel dye, promotes the formation of a ligand‐centred lowest triplet state of large spatial extension, potentially interesting for boosting interactions with electron scavengers. These results reveal a design strategy for broadening the applicability of porphyrin‐based dyes in optoelectronics.

A Nanographene‐Porphyrin Hybrid for Near‐Infrared‐Ii Phototheranostics

“…Negligible reactive oxygen species were detected during the irradiation process (Figure S7 , Supporting Information), which is presumably due to the low‐lying excited states of the NGP molecules, prohibiting efficient energy transfer to oxygen molecules. [ 57 , 74 ] In addition, the heavy atom effect of the central Ni 2+ ion [ 58 , 75 ] can also account for the favored non‐radiative relaxation to generate heat, contributing to the outstanding photothermal conversion performance of these NGP‐NPs. Moreover, NIR‐II light irradiation of NGP‐2‐NPs dispersions in a capillary tube also generated a PA signal (Figure 2g ), which increased proportionally to their concentration (Figure 2h ).…”