Pnictogen-Bridged Sulfoximines: Effects of Element and N-Substituent on Excited-State Dynamics

Pnictogen (Pn=As, Sb, Bi)-bridged sulfoximines were synthesized by introducing phenyl (Ph) and benzyl (Bn) groups onto the nitrogen atom. Single-crystal X-ray diffraction analysis and density functional theory (DFT) calculations revealed a weak closed-shell interaction between Pn and N or O. As- and Sb-bridged sulfoximines with a Bn group exhibited dual fluorescence in solution, while the others primarily showed a single emission. The viscosity and polarity of the solvent significantly affected dual-emission behavior. DFT calculations demonstrated the excited-state dynamics, showing that Pn⋅⋅⋅N (or Pn⋅⋅⋅O) interactions were either elongated or shortened upon photo-excitation, depending on the Pn type and the substituent on N.