Strong, Mode-Selective Evxciton-Photon Coupling Driven by Polariton Scattering in the Mo2 Complexes at Ambient Conditions

Abstract

Quadruply bonded Mo2 complexes provide a distinctive molecular platform in which multiple two-level electronic transitions interact with quantized scattering modes under ambient conditions. Here we show that, in the Mo2 complexes, the intrinsic photonic modes selectively couple to molecular excitations, including the characteristic delta-delta(star), ligand to metal charge transfer (LMCT) and metal to ligand charge transfer (MLCT) transitions, to form the well-resolved exciton-photon hybrid states. By combining steady-state absorption, resonance fluorescence, and ultrafast transient spectroscopies, we identify distinct polaritonic branches associated with these electronic manifolds, with coupling strengths spanning the strong and ultrastrong regimes (g/omega0 up to 0.1). Mode-selective coupling accounts for the pronounced spectral reorganization for the singly oxidized complexes, including the emergence of absorption valleys and sidebands of the associated resonances in the steady-state spectra, characteristic polaritonic emissions in the photoluminescence spectra, and long-lived low-energy hybrid states in the transient spectra. These results support the picture that the Mo2 unit functions as an integrated molecular resonator whose intrinsic quantized field selectively drives and redistributes molecular excitations. This work strengthens the emerging view of bonded dimetal complexes as ambient-condition molecular quantum systems and provides a chemically defined platform for exploring polaritonic chemistry.