Excited state dynamics and isomerization in ruthenium sulfoxide complexes

Area of Science:

• Coordination Chemistry
• Photochemistry
• Materials Science

Background:

• Molecular photochromic compounds reversibly change structure and properties upon light exposure.
• Ruthenium and osmium polypyridine sulfoxide complexes exhibit photochromism via sulfoxide isomerization.
• This light-activated switching has applications in chemical biology and materials science.

Purpose of the Study:

• To investigate the phototriggered isomerization mechanism in bis-sulfoxide metal complexes.
• To explore the potential for single-photon excitation to induce dual sulfoxide isomerizations.
• To understand the influence of chelate ring structure and R-group substituents on photochemical reactivity.

Main Methods:

• Synthesis and characterization of novel bis-sulfoxide metal complexes.
• Femtosecond pump-probe spectroscopy to study excited-state dynamics.
• High-level density functional theory (DFT) calculations to support mechanistic interpretations.

Main Results:

• Established that isomerization occurs nonadiabatically from a triplet excited state to a singlet ground state.
• Demonstrated that the photochemical reactivity is tunable by modifying the chelate ring and sulfoxide R-group.
• Observed that dual isomerizations can occur either sequentially or in a single photoexcitation event.

Conclusions:

• The study provides insights into the coupling of nuclear motion and electronic wave functions in photoisomerization.
• Design principles for controlling photochromic switching in bis-sulfoxide complexes were elucidated.
• These findings advance the development of sophisticated light-activated molecular switches.