Factorizing the Nephelauxetic Effect in Heteroleptic Molecular Rubies

Area of Science:

• Inorganic Chemistry
• Materials Science
• Photochemistry

Background:

• Chromium(III) complexes are gaining interest for phosphorescent emitters and photocatalysts.
• Spin-flip emitters offer potential for red-to-near-infrared light applications.
• Tuning excited state properties is crucial for designing efficient light-emitting materials.

Purpose of the Study:

• To synthesize and characterize novel heteroleptic bis(tridentate) polypyridine chromium(III) complexes.
• To investigate the energy tuning of spin-flip excited states in these complexes.
• To establish a predictive model for spin-flip emission energies based on ligand effects.

Main Methods:

• Synthesis of labile triflato chromium(III) complexes from chlorido precursors.
• Spectroscopic analysis (vis/near-infrared absorption and emission) to detect spin-flip energies.
• Multireference computational calculations to derive excited state properties.

Main Results:

• Successful synthesis of three series of heteroleptic chromium(III) complexes.
• Experimental and computational determination of spin-flip excited state energies.
• Delineation of an additive nephelauxetic effect of ligands on chromium(III) ions.

Conclusions:

• The synthesized complexes exhibit tunable spin-flip emission properties.
• The additive nephelauxetic effect provides a method to predict emission energies.
• These findings advance the design of earth-abundant chromium-based light emitters.