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Published on: July 27, 2022
Excited-state dynamics in fac-[Re(CO)3(Me4phen)(L)]+.
Antonio Otavio T Patrocinio1, M Kyle Brennaman, Thomas J Meyer
1Laboratory of Photochemistry and Energy Conversion, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, 05508-900, São Paulo, SP, Brazil.
The Journal of Physical Chemistry. A
|October 30, 2010
Summary
This study investigates excited-state dynamics in rhenium(I) polypyridyl complexes, revealing a complex equilibrium between excited states. Photoreactions like cis-to-trans isomerization compete with emission, influencing quantum yields and phosphorescence.
Area of Science:
- Photochemistry and Photophysics
- Coordination Chemistry
- Materials Science
Background:
- Rhenium(I) polypyridyl complexes are crucial in photochemistry due to their tunable photophysical properties.
- Understanding excited-state dynamics is key to controlling their light-emitting and photochemical behavior.
- Isomerization of ligands within these complexes can significantly alter their properties.
Purpose of the Study:
- To investigate the excited-state dynamics of fac-[Re(CO)(3)(Me(4)phen)(cis-L)](+) complexes.
- To elucidate the interplay between photoisomerization and excited-state energy transfer.
- To determine the energy barriers governing interconversion between different excited states.
Main Methods:
- Steady-state and time-resolved spectroscopic techniques were employed.
- Temperature-dependent emission measurements were conducted in solution and solid films (PMMA).
- Quantum yield measurements were performed to assess photochemical and photophysical processes.
Main Results:
- A complex equilibrium was established among three closely lying excited states: (3)IL(cis-L), (3)MLCT(Re→Me(4)phen), and (3)IL(Me(4)phen).
- UV irradiation induced cis-to-trans isomerization of the coordinated ligand (L) with a quantum yield of 0.15.
- Energy barriers for interconversion between MLCT and IL excited states were quantified, influencing internal conversion rates and enabling room-temperature phosphorescence.
Conclusions:
- The observed energy barriers are sufficient to reduce internal conversion rates, facilitating intraligand phosphorescence even in fluid media.
- Photoreactions, such as isomerization, compete with radiative decay pathways, impacting emission quantum yields.
- These findings highlight the critical role of energy gaps and excited-state dynamics in dictating the photochemical and photophysical properties of Re(I) polypyridyl complexes.
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