Molecular Bridge Engineering for Tuning Quantum Electronic Transport and Anisotropy in Nanoporous Graphene

Recent advances on surface-assisted synthesis have demonstrated that arrays of nanometer wide graphene nanoribbons can be laterally coupled with atomic precision to give rise to a highly anisotropic nanoporous graphene structure. Electronically, this graphene nanoarchitecture can be conceived as a set of weakly coupled semiconducting 1D nanochannels with electron propagation characterized by substantial interchannel quantum interferences. Here, we report the synthesis of a new nanoporous graphene structure where the interribbon electronic coupling can be controlled by the different degrees of freedom provided by phenylene bridges that couple the conducting channels. This versatility arises from the multiplicity of phenylene cross-coupling configurations, which provides a robust chemical knob, and from the interphenyl twist angle that acts as a fine-tunable knob. The twist angle is significantly altered by the interaction with the substrate, as confirmed by a combined bond-resolved scanning tunneling microscopy (STM) and ab initio analysis, and should accordingly be addressable by other external stimuli. Electron propagation simulations demonstrate the capability of either switching on/off or modulating the interribbon coupling by the corresponding use of the chemical or the conformational knob. Molecular bridges therefore emerge as efficient tools to engineer quantum transport and anisotropy in carbon-based 2D nanoarchitectures. This research was funded by the CERCA Programme/ Generalitat de Catalunya and by Grant Nos. SEV-2017-0706, CEX2021-001214-S, PID2019-107338RB-C62, PID2019- 107338RB-C65, and PID2019-107338RB-C66 funded by MCIN/AEI/10.13039/501100011033; FLAG-ERA Grant LEGOCHIP Projects PCI2019-111890-2 and PCI2019-111933-2 funded by MCIN/AEI/10.13039/501100011033 and cofunded by the European Union; Grant Nos. TED2021- 132388B-C41, TED2021-132388B-C42, and TED2021- 132388B-C44 funded by MCIN/AEI/10.13039/ 501100011033 and the European Union NextGenerationEU/ PRTR; Xunta de Galicia (Centro de Investigación de Galicia accreditation 2019−2022, ED431G 2019/03). X.D.C., A.S., and A.G.-L. also acknowledge the financial support received from the IKUR Strategy under the collaboration agreement between Ikerbasque Foundation and DIPC on behalf of the Department of Education of the Basque Government. C.M. was supported by Grant RYC2019-028110-I funded by MICIN/AEI/10.13039/501100011033 and by the European Social Fund “ESF Investing in your future”. M.T. was supported by Grant No. BES-2017-08078 funded by MCIN/ AEI/10.13039/501100011033 and by “ESF Investing in your future”. M.B. acknowledges funding from Villum fonden (VIL 00013340).