Charge-transfer dynamics in bowl-shaped imide-functionalized corannulenes at ensemble and single-molecule levels

Curved aromatic hydrocarbons provide unique platforms for tailoring charge-transfer (CT) excited states for functional optoelectronic and photonic materials. However, tuning CT behavior in bowl-shaped chromophores through molecular design and understanding their excited-state dynamics at the single-molecule level remain challenging. Herein, we investigate CT state engineering in bowl-shaped corannulene chromophores equipped with one (C-NMI) or two (C-NBI) annulated naphthalimide units. Pronounced solvatochromic shifts in fluorescence emission and a substantial change in dipole moment, upon photoexcitation, corroborate the enhanced CT character in C-NBI relative to C-NMI at the ensemble level. To probe the influence of local polarity at the single-molecule level, the chromophores were embedded in nonpolar polystyrene (PS) and polar poly(methyl methacrylate) (PMMA) matrices. The resulting fluorescence intensity trajectories (FITs) distinctly resolved locally excited (LE), hybrid LE-CT, and CT emissive states in C-NMI and C-NBI at the single-molecule level. Subsequently, femtosecond transient absorption spectroscopy captured the evolution of LE and CT states together with triplet-state population dynamics in C-NMI and C-NBI, while theoretical investigations further supported the observed triplet-state population behavior. Overall, this work demonstrates the role of molecular architecture and local dielectric environments in dictating excited-state pathways in bowl-shaped corannulene chromophores, opening new avenues for environment-sensitive probes and nanoscale photonic technologies.