Periodic Reporting for period 4 - NANOGRAPHOUT (Design, synthesis, study and applications of distorted nanographenes)
Période du rapport: 2020-10-01 au 2022-09-30
This methodology has proved to be very efficient and been exploited for the preparation of a completely new family of NGs, namely saddle-helix hybrid compounds, leading to the first NG described as chiral emitter. Remarkably, unprecedented combination of optical properties in graphene-related materials have been presented: upconversion based on two-photon absorption (TPA-UC) together with circularly polarized luminescence (CPL). We have demonstrated the effect of the saddle geometry on the TPA response enhancement in nanographenes. This fact could be extended to GQDs and might be one of the cause of their high TPA levels.
We have presented the first fully π-extended [7]helicene, namely, a fully helical ribbon. Fine structural tuning can modulate the optical response, leading to the first superhelicene that exhibits near-infrared NIR-CPL emission both in solution and thin-film.
We have studied the supramolecular chemistry of saddle-shaped NG where low self-association constants are observed and C70 is one of the best guests. In this sense, the incorporation of saddle-NGs into a flexible macrocycle allows their assembly with fullerenes, with selectivity for C70 vs C60. Furthermore the supramolecular assembly of saddle NGs with Ru complexes leads to stabilized Ru-nanoparticles acting as efficient aromatic hydrogenation catalyst.
The incorporation of heptagonal carbocycles as end-groups with [3]cumulene as spacers results in the aggregation-induced emission of [3]cumulenes and their incorporation as end-groups in typical diradical PAHs allows the establishment of a clear correlation between electronic and molecular structures. The first examples of organic radicals as CPL emitters in solution have been reported, including a new derivative acting as magnetic CPL emitter with a high racemization barrier.
The influence of the presence of defects on the electron transport through PAHs has also been studied in particular cases leading to interesting conclusions: i) BN-doping does not affect the electron transport through acene-like derivatives while stabilizing highly reactive all-carbon analogues; ii) N-doping of conjugated OPEs leads to the generation of additional conduction pathways in a single molecule.
We have also focused on the on-surface synthesis (OSS) of distorted graphene nanostructures as a way to modulate the optoelectronic/magnetic properties of the final assemblies. In this sense, heptagonal rings as tropone moieties are thermally transformed into hexagonal or pentagonal rings.
thus creating a new family of well-defined saddle-helix hybrid PAHs with high solubility and an outstanding combination of optical, chiroptical and electrochemical properties.