Cyclometallated iridium and platinum complexes with noninnocent ligands

Area of Science:

• Organometallic Chemistry
• Materials Science
• Photophysics

Background:

• Cyclometalated iridium and platinum complexes are crucial in various applications.
• Catechol ligands are known for their redox activity and potential for electronic tuning.
• Understanding the interplay between metal centers and noninnocent ligands is key to designing novel functional materials.

Purpose of the Study:

• To synthesize and characterize novel cyclometalated iridium and platinum complexes featuring a 3,5-di-tert-butylcatechol ligand.
• To investigate the electronic and photophysical properties of these complexes.
• To elucidate the role of the catechol ligand in the overall electronic structure and behavior of the metal complexes.

Main Methods:

• Synthesis and characterization of iridium- and platinum-cyclometalated complexes.
• X-ray crystallography for structural determination.
• UV-Vis-NIR absorption spectroscopy.
• Electrochemical studies (cyclic voltammetry).
• Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations.

Main Results:

• Successful synthesis of air-stable, paramagnetic iridium and platinum complexes with the semiquinone form of the catechol ligand.
• Observation of intense, low-energy electronic transitions in the visible to near-infrared region.
• Electrochemical studies revealed reversible reduction and irreversible oxidation of the catechol ligand.
• Computational analysis indicated spin density predominantly on the catechol ligand and identified the origin of the intense transitions.

Conclusions:

• The noninnocent catechol ligand significantly influences the electronic properties of the cyclometalated iridium and platinum complexes.
• The observed electronic transitions are attributed to ligand-centered electronic excitations.
• These findings provide insights into the design of novel organometallic materials with tunable electronic and optical properties.