@article{21986, abstract = {Over the past two decades, molecular electronics has made significant progress toward discovering nanoscale analogues of conventional electronic components, largely enabled by the development of the scanning tunneling microscope-based break-junction (STM-BJ) technique. The STM-BJ technique enables precise and highly reproducible measurement of a molecule’s electronic transport properties, making it a powerful technique to explore physiochemical and electrochemical phenomena that are otherwise difficult to access. It has gained substantial popularity in the past 20 years, with experiments becoming increasingly diverse and sophisticated. Despite the wealth of literature, an accessible, practical guide to performing STM-BJ experiments and interpreting the data is largely absent. This tutorial includes a brief background into the development of STM-BJ measurements, followed by detailed explanations of instrumentation, data collection, statistical analysis, variations on standard experiments, and some troubleshooting methods. It is aimed at researchers looking to begin or improve STM-BJ studies in their laboratories, graduate students and postdoctoral researchers learning the technique, and readers seeking to critically evaluate the growing body of STM-BJ literature.}, author = {York, Emma and Venkataraman, Latha}, issn = {2694-2445}, journal = {ACS Physical Chemistry Au}, number = {3}, pages = {408--424}, publisher = {American Chemical Society}, title = {{Scanning tunneling microscope-based break-junction technique - A tutorial}}, doi = {10.1021/acsphyschemau.6c00026}, volume = {6}, year = {2026}, } @article{21980, abstract = {Despite significant progress in the field of molecular electronics over the last two decades, the quantitative prediction of metal-molecule-metal junction conductance remains a challenge. The standard computational framework combines density functional theory (DFT) with nonequilibrium Green’s functions (NEGF) using low-rung exchange-correlation functionals such as PBE, which overestimate the conductances. More advanced correction methods exist but require complex workflows and high computational cost, limiting their accessibility. Here, we introduce a physically motivated approach that approximates results obtained with high-rung functionals. Our method fits the PBE-calculated transmission to a Breit-Wigner form and subsequently refines the fit parameters using molecular orbital energies and metal densities of states computed for the isolated subsystems with high-rung functionals. This approach is applicable to a broad range of molecular junctions yielding conductance values in quantitative agreement with experiments. Our approach is simple, low-cost, and accurate, making it well-suited for routine and large-scale prediction of single-molecule junction conductance.}, author = {Gulyaev, Artem and Hazarika, Jyotisman and Liu, Zhen-Fei and Venkataraman, Latha}, issn = {1530-6992}, journal = {Nano Letters}, number = {22}, pages = {7429–7434}, publisher = {American Chemical Society}, title = {{A computationally efficient and accurate method for predicting conductance of single-molecule junctions}}, doi = {10.1021/acs.nanolett.6c01462}, volume = {26}, year = {2026}, } @article{22711, abstract = {When charge flows through a molecular circuit, it induces a magnetic field that allows the circuit to behave as a nanoscale electromagnet. However, in single-molecule circuits this magnetic field is usually weak. Here we show that radially π-conjugated carbon structures can support amplified circulating currents that generate local magnetic fields. Within tight-binding and density functional theory (DFT) frameworks, we first study cycloparaphenylene (CPP) junctions where both electrodes are attached to the same phenylene unit on the nanohoop. We observe an energy-dependent ring current component that traverses the whole macrocycle by mapping the local current density. Importantly, we find that destructive interference near degenerate resonances can reverse the ring current direction and amplify it strongly relative to the source–drain current. We show that this interference-driven design principle is general, and also carries over to C60 junctions. In fullerene, lower-lying degenerate resonances are more easily accessible through electrostatic gating, reaching a magnetic field of 14.2 mT under a 100 mV source–drain bias. This work thus provides new insights into ring currents in radially π-conjugated carbon structures and highlights their potential as design platforms for single-molecule electromagnets.}, author = {Shi, Wanzhuo and Korytár, Richard and Evers, Ferdinand and Tovar, John D. and Venkataraman, Latha}, issn = {2041-1723}, journal = {Nature Communications}, publisher = {Springer Nature}, title = {{Designing effective single-molecule electromagnets with radially π-conjugated carbon structures}}, doi = {10.1038/s41467-026-74365-6}, volume = {17}, year = {2026}, } @article{22975, abstract = {Conjugated molecules with diradical character have emerged as promising building blocks for high-conductance single-molecule electronics because of their behavior as 1D topological insulators. However, the impact of antiaromaticity on these radical-based edge states has not been explored. Here, we introduce thiophene-based molecular wires that exhibit intrinsic diradical character in their ground state under ambient conditions and systematically investigate how their conductance responds to changes in aromaticity upon the oxidation of fluorene-based flanking moieties. Using scanning tunneling microscopy-based break junction (STM-BJ) techniques, we show that the conductance increases with molecular length in the neutral state, supporting one-dimensional topological behavior. We further examine the effect of oxidation on conductance through three complementary methods, revealing substantial conductance enhancements that we attribute to an increase in the antiaromatic character of the wires. Together, these findings establish a rational design strategy for highly conducting, electrochemically switchable molecular junctions, with implications for single-molecule electronics.}, author = {Lee, Woojung and Shi, Wanzhuo and Kwon, Junho and Low, Jonathan and Wei, Sujun and Yin, Xiaodong and Campos, Luis M. and Venkataraman, Latha}, issn = {1520-5126}, journal = {Journal of the AmericanChemical Society}, number = {37}, pages = {40536–40542}, publisher = {American Chemical Society}, title = {{Redox-driven antiaromaticity enables multistate conductancein 1D topological insulators}}, doi = {10.1021/jacs.6c15721}, volume = {148}, year = {2026}, } @article{23111, abstract = {In single-molecule electronics, 4,4′-bipyridine is a well-characterized molecule that serves both as a fundamental testbed for developing experimental methodologies and showcases the complex behaviors expected from molecular electronic components. In break junction experiments, it is generally understood to exhibit a high- and a low-conductance state that are attributed to a tilted and stretched single-molecule configuration. Despite this established view, we suggest a supramolecular origin for these conductance states that has not previously been considered. Our findings indicate that the high- and low-conductance states may arise from the presence of two molecules and one molecule, respectively, challenging the conventional interpretation. Using a state-of-the-art machine learning force field called the neuroevolution potential, we find that the conventional interpretation of a tilted and stretched configuration is inconsistent with our simulations. Instead, our results suggest that the presence of two molecules promotes junction geometries and gold rearrangements that stabilize a high-conductance state whose transmission exceeds twice that of the low-conductance state. Furthermore, we compare this interpretation to the existing literature of diverse experimental data on 4,4′-bipyridine in break junctions and find that it is consistent with the broader body of experimental evidence. Our results highlight the structural complexity of molecular behavior within break junctions, suggesting even more complex dynamics than originally anticipated. In this light, a broader examination of the dynamics of molecules in single-molecule break junctions with machine learning-assisted molecular dynamics is warranted.}, author = {Bro-Jørgensen, William and Lin, Junfeng and Hamill, Joseph M. and Solomon, Gemma C.}, issn = {2694-2496}, journal = {ACS Nanoscience Au}, number = {4}, pages = {662--673}, publisher = {American Chemical Society}, title = {{Machine learning-enhanced molecular dynamics of 4,4′-bipyridinein a break junction: A supramolecular origin of the high conductance}}, doi = {10.1021/acsnanoscienceau.6c00052}, volume = {6}, year = {2026}, } @article{20010, abstract = {Chirality-induced spin selectivity (CISS), which refers to the ability of chiral molecules to preferentially select spins during electron transfer, has attracted great attention during the past two decades. However, the theoretical and experimental understanding of the CISS effect remains preliminary. In this study, we demonstrate that there is no distinguishable CISS effect in the case of coherent electron transport through single chiral molecular junctions for a set of four molecule studied here. Our conclusion is based on statistical evaluations of thousands of single-molecule junctions across four different molecules with different origins of chirality measured by the scanning tunneling microscope-based break-junction technique. The experimental results for all molecules show no dependence on external magnetic field or chirality in both conductance and current–voltage measurements. In addition, ab initio Hartree-Fork calculations combined with the nonequilibrium Green’s function method reveal that the spin–orbit coupling within chiral junctions bound to a few gold atoms is generally too weak to induce detectable spin polarizations from spin flipping or spin filtering during the ultrafast electron-transport time scale. The absence of an observable CISS effect in the coherent electron-transport regime suggests that the effect may only be found in other electron-transfer regimes and requires further experimental and theoretical efforts to achieve a comprehensive understanding.}, author = {Li, Liang and Shi, Wanzhuo and Mahajan, Ankit and Zhang, Junxiang and Gómez-Gómez, Marta and Labella, Jorge and Louie, Shayan and Torres, Tomás and Barlow, Stephen and Marder, Seth R. and Reichman, David R. and Venkataraman, Latha}, issn = {1520-5126}, journal = {Journal of the American Chemical Society}, number = {28}, pages = {25043--25051}, publisher = {American Chemical Society}, title = {{Too fast for spin flipping: Absence of chirality-induced spin selectivity in coherent electron transport through single-molecule junctions}}, doi = {10.1021/jacs.5c08517}, volume = {147}, year = {2025}, } @article{20221, abstract = {We describe the design, synthesis, and single-molecule junction conductance of π-electron molecules bearing both radial and linear π-conjugation pathways, whereby cycloparaphenylene (CPP) radial cores are π-extended linearly with aryl alkyne substituents as models for previously reported CPP-arylene ethynylene conjugated polymers. Although radially and linearly conjugated molecules have been studied previously in isolation as junction-bridging molecular electronic units, this is the first study to examine molecules where both topologies are operative. Our results reveal that the presence of radial CPP components within the junction-spanning pathway leads to a reduction in the conductance of the backbone compared to model linear phenyl substituents. Through tight-binding and DFT-based calculations, we attribute this conductance change to intramolecular van der Waals (vdW) interactions between the CPP ring and the junction-spanning arylene-ethynylene molecular backbone. These interactions induce changes in the dihedral angles of the backbone, leading to a reduced overlap of π orbitals within the molecular junction.}, author = {Shi, Wanzhuo and Wang, Mengjiao and Venkataraman, Latha and Tovar, John D.}, issn = {1530-6992}, journal = {Nano Letters}, number = {31}, pages = {12101--12106}, publisher = {American Chemical Society}, title = {{Single-molecule conductance through hybrid radially and linearly π-conjugated macromolecules reveals an unusual intramolecular π-interaction}}, doi = {10.1021/acs.nanolett.5c03693}, volume = {25}, year = {2025}, } @article{20331, abstract = {Here, we present a foundational investigation of charge transport through three BODIPY-based molecules using the scanning tunneling microscope–break junction (STM-BJ) technique. We demonstrate that molecular conductance through the BODIPY core can be measured by introducing aurophilic linkers at the 2,6-positions. By varying these linkers, we systematically modulate the frontier molecular orbital energies and fine-tune transport behavior. Our experimental results are supported by DFT-based calculations, which feature a new computationally efficient correction to standard PBE-level transmission predictions. Together, these findings establish the viability of BODIPY-based systems for molecular junction applications and lay the groundwork for future studies of their single-molecule optoelectronic properties.}, author = {York, Emma and Stone, Ilana and Shi, Wanzhuo and Roy, Xavier and Venkataraman, Latha}, issn = {1530-6992}, journal = {Nano Letters}, number = {36}, pages = {13697--13702}, publisher = {American Chemical Society}, title = {{Tuning conductance in BODIPY-based single-molecule junctions}}, doi = {10.1021/acs.nanolett.5c03764}, volume = {25}, year = {2025}, }