Designing Long-Range Charge Delocalization from First-Principles

摘要

Efficient electronic communication over long distances is a desirable property of molecular wires. Charge delocalization in mixed-valence (MV) compounds where two redox centers are linked by a molecular bridge is a particularly well-controlled instance of such electronic communication, thus lending itself to comparisons between theory and experiment. We study how to achieve and control longrange charge delocalization in cationic organic MV systems by means of Kohn-Sham density functional theory (DFT) and show that a captodative substitution approach recently suggested for molecular conductance (Stuyver et al. J. Phys. Chem. C 2018, 122, 3194) greatly enhances charge delocalization in p-phenylene-based wires. To ensure the adequacy of our DFT methods, we validate different protocols for organic MV systems of different lengths. The BLYP35 hybrid functional combined with a polarizable continuum model, established by Renz and Kaupp, is indeed capable of correctly describing experimentally observed length-dependent charge delocalization, in contrast to the long-range corrected functionals omega-B97X-D and omega-PBE. We also discuss the implications of these results for a first-principles description of the transition between coherent tunneling and incoherent hopping regimes in molecular conductance.