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Light-emitting materials from cyclometalated heteroleptic iridium(III) complexes--A physicochemical study
Jayaraman Jayabharathi1, Venugopal Thanikachalam, Natesan Srinivasan
1Department of Chemistry, Annamalai University, Annamalainagar 608002, Tamilnadu, India. jtchalam2005@yahoo.co.in
Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
|December 14, 2011
Summary
Researchers studied phosphorescent iridium(III) complexes. These complexes exhibit metal-to-ligand charge transfer and π-π* excited states, with emission properties influenced by solvent polarity and increasing with emission wavelength.
Area of Science:
- Organometallic Chemistry
- Photophysics
- Coordination Chemistry
Background:
- Heteroleptic cyclometalated iridium(III) complexes are investigated for their photoluminescent properties.
- Picolinic acid serves as a key ancillary ligand in these iridium complexes.
- Understanding excited states is crucial for tuning luminescence.
Purpose of the Study:
- To investigate the phosphorescent properties of 2-arylimidazole heteroleptic cyclometalated iridium(III) complexes.
- To elucidate the nature of the excited states and their solvent dependence.
- To explore the relationship between emission kinetics and emission wavelength.
Main Methods:
- Synthesis and characterization of iridium(III) complexes.
- Photoluminescence spectroscopy (emission and excitation spectra).
- Solvatochromism studies using Reichardt-Dimroth and Marcus solvent functions.
- Emission kinetic measurements.
Main Results:
- The complexes exhibit dominant (3)MLCT (metal-to-ligand charge transfer) and (3)π-π* excited states.
- Solvent shifts were successfully interpreted using established solvent functions, indicating sensitivity to solvent polarity.
- Emission kinetic studies revealed a positive correlation between radiative transition rate (k(r)) and emission wavelength (λ(em)).
Conclusions:
- The studied iridium(III) complexes possess tunable photophysical properties.
- The excited state character and solvent effects are well-described by theoretical models.
- Emission kinetics provide insights into the radiative decay pathways, influenced by the emission energy.
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