Bright luminescent lithium and magnesium carbene complexes

Area of Science:

• Organometallic Chemistry
• Materials Science
• Photophysics

Background:

• Development of novel ligands is crucial for advancing coordination chemistry and materials science.
• Mesoionic carbenes (MICs) and carbazole units are important building blocks in ligand design.
• Luminescent s-block metal complexes offer potential in various optical applications.

Purpose of the Study:

• To report a convenient synthesis of a carbazole-mesoionic carbene (CNC) pincer ligand.
• To synthesize and characterize lithium and magnesium complexes of the CNC ligand.
• To investigate the photophysical properties, particularly luminescence, of the tri-deprotonated s-block complexes.

Main Methods:

• Synthesis of the CNC pincer ligand and its lithium/magnesium complexes.
• Spectroscopic characterization including absorption and luminescence spectroscopy.
• Quantum-chemical calculations to rationalize emissive properties.

Main Results:

• Successful synthesis of the CNC pincer ligand and its lithium/magnesium complexes.
• Tri-deprotonated s-block complexes exhibit bright luminescence with a 16% quantum yield in solution.
• Quantum-chemical calculations identified an Intra-Ligand-Charge-Transfer (ILCT) mechanism responsible for luminescence.

Conclusions:

• The CNC pincer ligand and its s-block metal complexes are readily accessible.
• The tri-deprotonated complexes display significant luminescence, attributed to ILCT.
• Alkali metals play a key role in stabilizing the excited state, preventing non-radiative decay and enhancing luminescence.