Multiscale Modeling Reveals Synergistic Rectification in DNA-Coralyne Complexes by Environmental Symmetry Breaking...

Molecular rectification, as one of the earliest proposed device functions based on intrinsic molecular properties, is typically realized by structural or interfacial asymmetry of the junction. Surprisingly, DNA-coralyne complexes (cor-DNA) have been reported to exhibit pronounced rectification despite an apparently symmetric molecular structure, posing a challenge to prevailing physical pictures of charge transport in symmetric systems. We investigate this behavior using a multiscale computation framework coupled with electrostatics, molecular dynamics, and quantum transport that explicitly accounts for electrode geometry and the ionic environment, besides molecules in the laboratory study. We find that the cor-DNA itself does not create an intrinsically oriented transport pathway that breaks symmetry. Instead, symmetry breaking is imposed by the nonuniform electric field in the sharp-tip and planar-substrate configuration and the resultant asymmetric electric-double-layer response that localizes the voltage drop at the tip interface. Crucially, the intercalated coralyne molecule functions as a resonant bridge that enables long-range connectivity within the junction. Rectification arises from a cooperative synergy between the extrinsic potential profile and the electronic states of the intercalator, which are selectively shifted into resonance to hybridize with the DNA base stack. This mechanism explains why rectification is absent in pristine DNA and persists in cor-DNA regardless of molecular orientation. A reduced multilevel model further demonstrates that this synergistic rectification is a tunable property governed by the energy alignment of the intercalator and its coupling strength to the DNA backbone. These findings offer a robust pathway to realize functional molecular devices by exploiting the active interplay between symmetric molecular scaffolds and asymmetric environments.