Confinement-induced aryl ring Homoconjugation in fluorescent mesoporous silica nanoparticles

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Photophysics

Background:

• Flexible organic molecules often lack desirable photophysical properties.
• Mesoporous silica nanoparticles (MSNs) offer a versatile platform for molecular confinement.
• Achieving molecular self-assembly and tuning photophysics typically requires chemical modification.

Purpose of the Study:

• To investigate the non-covalent induction of homoconjugation in diphenylmethane (DPM) derivatives within MSNs.
• To explore the impact of host-guest confinement on the photophysical properties of DPMs.
• To establish a simple strategy for generating novel fluorophores with tunable emission.

Main Methods:

• Synthesis and characterization of DPM derivatives.
• Encapsulation of DPMs within MSNs.
• UV-visible and fluorescence spectroscopy to analyze photophysical changes.
• Varying guest loading concentrations to study aggregation effects.

Main Results:

• Confinement in MSNs induced through-space π-π overlap and homoconjugation in DPMs without chemical alteration.
• Spectroscopic analysis showed red-shifted excitation/emission bands and significantly enhanced quantum yields.
• Homoconjugation persisted in polar solvents at low guest loading, while higher concentrations led to aggregation and further spectral shifts.
• Observed photophysical changes paralleled those of rigid diphenylnorbornane (DPN) analogues.

Conclusions:

• Host-guest encapsulation in MSNs is an effective non-covalent strategy to induce homoconjugation.
• This method allows for tuning the photophysical properties of flexible molecules like DPMs.
• The approach provides a facile route to generating tailored homoconjugated fluorophores for various applications.