Molecular Materials
How do the electronic properties of molecular building blocks influence the electrical conductivity of structurally analogous extended materials? Molecule-based materials such as covalent organic and metal-organic frameworks (COFs and MOFs) are of great interest for applications in energy storage, electrocatalysis, and sensing, and offer enormous structural and chemical tunability. However, understanding their bulk electronic properties remains challenging. Electrical measurements of bulk samples can be strongly influenced by defects and grain boundaries, crystallite orientation, and the nature of the electrical contacts, making it difficult to assess how the molecular elements from which these materials are assembled contribute to their intrinsic electronic properties.
Our group seeks to connect charge transport through molecule-based structures across length scales, from individual molecules to oligomers to extended materials. Our goal is to uncover structure-property relationships that can guide the design of permanently porous molecule-based materials with targeted electrical properties. By combining molecular synthesis and electrochemistry with single-molecule conductance, large-area junction conductivity, and bulk conductivity measurements, we aim to determine which transport properties are intrinsic to the molecular components and how these properties evolve as increasingly complex structures are assembled.
Figure 1. Relating charge transport across different length scales. (a) Molecular building blocks can be mapped onto structural elements of extended materials. (b) Comparing transport through structurally related molecular-scale and bulk systems provides a strategy for identifying electronic properties that persist across length scales.
Connecting molecular and bulk charge transport
Can measurements of individual molecular components help us understand and predict the conductivity of extended materials? We use single-molecule junctions as atomically precise model systems for probing charge transport through molecular building blocks and the chemical linkages used to connect them. Such studies can provide information on the length dependence of charge transport at the nanoscale, allowing us to identify potentially predictive molecular-scale design metrics. For example, trends in intersite electronic coupling are expected to correlate with trends in band dispersion in extended materials. If transport behavior at the single-molecule level can be shown to correlate with that of oligomers and extended structures, we hope to establish a bottom-up framework for the rational design of molecule-based conductors across multiple length scales.
Designing electronically active molecular building blocks
We seek to identify new molecular families whose structures and properties may be well suited for use as building blocks for extended two- and three-dimensional materials. We first develop their synthetic chemistry, characterize their electronic properties (e.g., through single-molecule conductance measurements), and then explore strategies for incorporating them into extended crystalline structures. One such family we are developing is metal(IV) tetraaryl complexes, which may provide electronically transparent, redox-active building blocks for three-dimensional COFs. These contrast with conventional tetrahedral nodes based on carbon or silicon central atoms, which interrupt π-conjugation between the σ-bound aryl ligands.
To date, we have developed improved synthetic routes to Os(IV) tetraaryl complexes, which we consider tetrahedral analogues of the prototypical organometallic compound ferrocene. We have investigated how the molecular structure, redox chemistry, and electronic properties of these complexes change with chemical modification. Our molecular-level studies support the hypothesis that the aryl ligands are more strongly electronically coupled through osmium than through carbon or silicon central atoms, providing strong motivation to incorporate these species into larger assemblies for testing.
Figure 2. Developing electronically active molecular building blocks. (a) Improved synthetic routes provide access to chemically tunable Os(IV) tetraaryl complexes that can be further elaborated into more complex redox-active molecular architectures. (b) Representative Os(IV) tetraaryl compounds synthesized in our laboratory, shown in the solid state (left) and in solution.
Selected publications
Enhanced electronic coupling in tetraaryl molecular junctions with osmium(IV) centers
Chem. Sci., 2026, 17, 14745
Intervalence Charge Transfer in an Osmium(IV) Tetra(ferrocenylaryl) Complex
Inorg. Chem., 2025, 64, 2312
Charge transport across dynamic covalent chemical bridges
Nano Lett., 2022, 22, 8331