Deuterated Molecular Ruby with Record Luminescence Quantum Yield.

Area of Science:

• Coordination Chemistry
• Photophysics
• Materials Science

Background:

• The luminescent chromium(III) complex 1^3+ ([Cr(ddpd)2]^3+) exhibits strong near-IR emission.
• Ligand design in 1^3+ minimizes non-radiative decay pathways like photosubstitution, back-intersystem crossing, and trigonal twists.
• Energy transfer to solvent (OH) and ligand (CH) oscillators are primary decay routes in the absence of quenchers.

Purpose of the Study:

• To investigate and suppress non-radiative decay pathways in the chromium(III) complex.
• To enhance the quantum yield and excited-state lifetime of the luminescent complex.
• To probe the role of solvent and ligand vibrations in excited-state deactivation.

Main Methods:

• Synthesis and characterization of the chromium(III) complex ([Cr(ddpd)2]^3+).
• Spectroscopic studies in water under ambient conditions.
• Selective deuteration of solvents and ddpd ligands to probe energy transfer pathways.

Main Results:

• The complex exhibits strong near-IR emission at 775 nm with an initial quantum yield of 11% and microsecond lifetime.
• Selective deuteration significantly reduced energy transfer to OH and CH oscillators.
• A record 30% quantum yield and 2.3 ms lifetime were achieved for this earth-abundant metal complex in solution.

Conclusions:

• Effective suppression of non-radiative decay and energy transfer pathways is crucial for enhancing luminescence in metal complexes.
• Deuteration strategies offer a powerful method to tune excited-state dynamics and improve photophysical properties.
• This work sets a new benchmark for luminescent complexes with earth-abundant metals, paving the way for advanced applications.