Chemical Bonding Descriptors in Metal–Benzenedithiol–Metal Systems

This computational study investigates benzenedithiol (BDT) as a molecular junction between two silver contacts, modeled as atomic clusters, in non-conductive (OFF) and conductive (ON) binding conformations. Geometry optimizations and harmonic vibrational frequency calculations were performed using ORCA 6 at the ωB97X-D3/def2-TZVP level of theory. QTAIM and overlap density descriptors (OP/TOP) were analyzed to evaluate C–S chemical bonding across conformations. Results reveal that coordinating three Ag atoms to a single sulfur in the ON state decreases the covalent character of the adjacent C–S bond. Through-ring electronic influence similarly reduces covalency in the para C–S bond, indicating that multi-atom Ag coordination hinders sulfur lone-pair resonance into the ring and redistributes electron density toward the para contact. The effect of benzene substituents on junction properties will also be presented.