Bridge‐Controlled Excited‐State Interactions in Cofacial Phenylene–Vinylene Oligomers

Rigid cofacial π‐conjugated systems provide a well‐defined platform for investigating how molecular geometry governs excited‐state interactions in organic optoelectronic materials. Density functional theory (DFT) and time‐dependent DFT (TD‐DFT) calculations were performed on unbridged p‐phenylenevinylene‐stilbene (1PV) and oligo(p‐phenylenevinylene) (o‐PV) dimers together with xanthene‐ and dibenzofuran‐bridged cofacial analogs. Natural transition orbitals (NTOs) and fragment‐resolved transition‐density analyses were employed to characterize local excitation character, direct interstrand charge transfer, bridge participation, and the limitations of the simplified S1‐S2 splitting model. Xanthene bridges promote compact cofacial geometries with shorter interchain distances and smaller bite angles, whereas dibenzofuran bridges generate more open structures. The fragment‐resolved analysis reveals that the low‐lying excited states remain predominantly local in character, with only minor direct interstrand charge‐transfer contributions, while bridge participation is substantially greater in the 1PV systems than in the corresponding o‐PV analogs. The effective S1‐S2 half‐splitting, J _eff , ranges from 27.5 to 110.0 meV and is interpreted as a comparative descriptor of the low‐energy excited‐state separation. These results show that bridge‐dependent excited‐state behavior reflects the combined effects of molecular geometry, excitation localization, bridge participation, and multipair NTO character rather than interchain distance alone.