Confinement-induced aryl ring Homoconjugation in fluorescent mesoporous silica nanoparticles.

Confinement of flexible diphenylmethane (DPM) derivatives inside mesoporous silica nanoparticles (MSNs) induces through-space π-π overlap and homoconjugation without chemical modification. UV-visible and fluorescence spectroscopy reveal red-shifted excitation and emission bands, along with markedly enhanced quantum yields, paralleling rigid diphenylnorbornane (DPN) analogues. At low guest loading, DPMs remain well dispersed and homoconjugation persists even in polar solvents, whereas higher concentrations favour aggregation and further spectral shifts. This host-guest strategy provides a simple, non-covalent route to tuning molecular photophysics and generating homoconjugated fluorophores.