Yuan Li’s and Enrique del Barco’s teams demonstrated a giant molecular rectification mechanism driven by redox-coupled conformational switching in π-extended tetrathiafulvalene (exTTF) molecular junctions. Under negative bias, exTTF undergoes a two-electron oxidation, changing from a buckled, cross-conjugated structure to a planar, fully conjugated aromatic state, resulting in unidirectional charge delocalization and rectification ratios up to 5.0 × 10⁴ even in symmetric molecules. Combined experimental (EGaIn junctions, CV, UPS, XRD) and DFT-NEGF analyses confirmed that field-driven electron delocalization triggers this transition, leading to thermally activated hopping under negative bias and tunneling under positive bias. The work establishes electric-field-induced topology control as a new design strategy for high-performance molecular diodes, eliminating the need for structural asymmetry and expanding the potential of symmetric SAM-based electronic devices.