Deciphering and quantifying linear light upconversion in molecular erbium complexes.

Area of Science:

• Materials Science
• Photochemistry
• Coordination Chemistry

Background:

• Light upconversion, the process of converting low-energy photons to higher energies, is typically observed in lanthanide-doped solids.
• Miniaturizing upconversion in molecular complexes presents challenges due to high-energy vibrations limiting excited-state absorption (ESA) efficiency.
• Existing methods often rely on sophisticated supramolecular assemblies.

Purpose of the Study:

• To develop highly efficient molecular systems for light upconversion.
• To overcome the limitations of vibrational energy loss in coordination complexes for upconversion.
• To establish a benchmark for molecular-based excited-state absorption (ESA) mechanisms.

Main Methods:

• Synthesized mononuclear coordination complexes of trivalent erbium with polyaromatic ligands, denoted as [Er(L)3]3+.
• Investigated light upconversion from near-infrared (801 nm or 966 nm) to visible green (522 nm and 545 nm) emission.
• Operated the complexes in both solid-state and non-deuterated solution conditions.

Main Results:

• Achieved efficient room-temperature light upconversion in the synthesized mononuclear erbium complexes.
• Observed upconversion at low excitation power, comparable to cooperative upconversion in complex supramolecular systems.
• Calculated upconversion quantum yields establish a baseline for molecular ESA mechanisms.

Conclusions:

• Successfully engineered molecular complexes for efficient light upconversion, overcoming vibrational damping issues.
• Demonstrated the potential of molecular design in tuning upconversion mechanisms and performance.
• These findings pave the way for advanced applications in optical programming and miniaturized photonic devices.