Molecular junctions formed by a few (down to one) molecules bonded between two metallic electrodes bare the promise of maximal circuit miniaturization and scalability. In addition, single-molecule circuits allow the direct investigation of the electrical properties of organic materials at the ultimate level of a single molecule, including non-trivial quantum effects at room temperature. At the molecular electronics laboratory of IMDEA Nanoscience, we investigative different of these quantum effects by exploring the dependence of the conductance, thermopower and stability of single-molecule circuits on the composition of the studied organic compound, within a variety of molecular families. Our junctions are based on the break junction technique using scanning tunneling microscopes developed in house. In this presentation, I will summarize several of our last results covering the effect of B-N substitutions in nanographene compounds (L. Palomino-Ruiz et al. Angew. Chem. Int. Ed. 2021, 60, 6609 – 6616.), the development of molecular potentiometers (L. Palomino-Ruiz et al. J. Mater. Chem. C, 2021, 9, 16282), the evolution of molecular wires properties at the onset of the symmetry breaking transition (W. Xu et al. J. Am. Chem. Soc. 2021, 143, 20472−20481), the tunning of properties of diradical compounds (R. Casares et al. J. Mater. Chem. C, 2022, 10, 11775) or the properties of chiral helical compounds (A. M. Ortuño et al. Angew. Chem. Int. Ed. 2023, e202218640).
