Dual conformational emission and vibrational coherence in a sulfone-embedded narrowband emitter

oscillates along the excited-state potential energy surface of the boat conformation. This mode, which involves the bending vibration of sulfone and out-of-plane bending of carbonyl and peripheral phenyl groups, mainly drives the structural reorganization during the electronic transition. These findings provide mechanistic insights into conformation-dependent emission in narrowband emitters and underscore the crucial vibrational information in guiding the molecular design toward high color-purity organic fluorophores.