A Vanadium(III) Complex with Blue and NIR-II Spin-Flip Luminescence in Solution

Area of Science:

• Inorganic Chemistry
• Materials Science
• Photophysics

Background:

• Luminescence from Earth-abundant first-row transition metals at room temperature is challenging due to weak ligand field splitting and efficient nonradiative decay.
• Achieving luminescence in the near-infrared (NIR) region is particularly difficult due to additional nonradiative pathways.
• No Earth-abundant first-row transition metal complexes have previously shown emission above 1000 nm at room temperature in solution.

Purpose of the Study:

• To explore the luminescence properties of Earth-abundant metal complexes, specifically vanadium(III) complexes.
• To investigate the potential of vanadium(III) complexes as blue and NIR-II luminophores.
• To develop new luminescent materials that are cost-effective alternatives to precious metal and rare-earth element complexes.

Main Methods:

• Synthesis and characterization of the vanadium(III) complex, mer-[V(ddpd)2][PF6]3.
• Photoluminescence spectroscopy to measure emission spectra, quantum yields, and lifetimes.
• Studies conducted in solution (acetonitrile) at room temperature and in glass (valeronitrile) at 77 K.

Main Results:

• The vanadium(III) complex, mer-[V(ddpd)2][PF6]3, exhibits phosphorescence around 1100 nm (NIR-II region) at room temperature in acetonitrile with a quantum yield of 1.8 × 10⁻⁴%.
• The complex also displays strong blue fluorescence with a 2% quantum yield in acetonitrile at room temperature.
• These findings demonstrate the viability of vanadium(III) complexes as dual-mode luminophores.

Conclusions:

• Vanadium(III) complexes with a d² electron configuration represent a new class of blue and NIR-II luminophores.
• These complexes offer a promising, cost-effective alternative to traditional luminophores based on expensive precious metals and rare-earth elements.
• The study opens new avenues for the development of functional materials for various optical applications.