Color-Tunable Upconversion-Emission Switch Based on Cocrystal-to-Cocrystal Transformation

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Photophysics

Background:

• Cocrystal engineering is key for tuning photophysical properties of solid-state materials.
• Achieving reversible transformations and controlled assembly/disassembly of multicomponent cocrystals remains a significant challenge.
• Upconversion emission, particularly two-photon excited, is crucial for advanced optical applications.

Purpose of the Study:

• To develop a color-tunable upconversion-emission switch.
• To demonstrate reversible cocrystal-to-cocrystal transformations.
• To explore the role of intermolecular charge transfer in tuning emission properties.

Main Methods:

• Synthesis of two distinct cocrystals using a naphthalenediimide-based macrocycle and different electron donors.
• Characterization of cocrystal structures and their solid-state properties.
• Investigation of reversible transformations triggered by electron donor exchange.
• Measurement of two-photon excited upconversion emission spectra.

Main Results:

• Two cocrystals with red and yellow emission were successfully synthesized.
• Reversible interconversion between the red- and yellow-emissive cocrystals was achieved by exchanging electron donors.
• The cocrystals exhibited strong two-photon excited upconversion emission due to intermolecular charge transfer.
• A dual-color upconversion-emission switch was demonstrated through cocrystal interconversion.

Conclusions:

• Precise control over cocrystal-to-cocrystal transformation is achievable.
• This work provides a novel dual-color upconversion-emission switch.
• The findings offer a valuable reference for designing color-tunable nonlinear optical materials.