Quantum Interference and Aromaticity Control in Triazine-Based Molecular Junctions: A Combined Green's Function and...

Molecular electronics provides a powerful platform to explore quantum transport phenomena at the single-molecule level, where charge transport is governed by molecular structure, connectivity, and electronic delocalization. In this work, we present a comprehensive computational study of electron transport through triazine-based molecular junctions inspired by graphitic carbon nitride motifs. Using a bottom-up approach, we investigate a hierarchy of molecular models ranging from triazine monomers to heptazine and tri-heptazine scaffolds. Electron transport properties are analyzed within the nonequilibrium Green's function formalism combined with density functional theory (DFT), focusing on transmission spectra, local transmission pathways, and quantum interference effects. We show that nitrogen-rich conjugated frameworks exhibit a rich variety of interference patterns, including constructive, destructive, and shifted destructive quantum interference, which are highly sensitive to molecular connectivity and substitution patterns. Orbital selection rules and pathway analyses are employed to rationalize the emergence and position of interference features. Furthermore, we demonstrate that substituent effects modulate molecular conductance in a topology-dependent manner, and that changes in electronic delocalization, quantified through aromaticity descriptors such as HOMA, MCI, AV1245, and AV_min, correlate with transmission behavior. In extended triazine-based architectures, the interplay between competing transmission pathways leads to nontrivial aromaticity-conductance relationships.