A Triplet Label Extends Two-Dimensional Infrared Spectroscopy from Pico- to Microseconds

Area of Science:

• Physical Chemistry
• Spectroscopy
• Materials Science

Background:

• Conventional two-dimensional infrared (2D-IR) spectroscopy is limited to picosecond timescales due to short vibrational lifetimes.
• Complex molecular dynamics in systems like polymers and proteins occur over broader femto- to microsecond ranges.
• Observing these slower dynamics requires techniques that extend beyond vibrational lifetimes.

Purpose of the Study:

• To overcome the timescale limitations of conventional 2D-IR spectroscopy for studying molecular dynamics.
• To introduce a novel probe and technique for extending the observation window of spectral diffusion.
• To enable the monitoring of molecular dynamics on microsecond timescales.

Main Methods:

• Development and application of Vibrationally Promoted Electronic Resonance (VIPER) 2D-IR spectroscopy.
• Utilizing 2-Isopropylthioxanthone as a novel VIPER probe that exploits intersystem crossing.
• Implementation of a Fourier-transform approach to enhance signal-to-noise ratio and resolution in VIPER 2D-IR.

Main Results:

• Demonstrated VIPER 2D-IR spectroscopy with 2-Isopropylthioxanthone, extending observation to the microsecond timescale.
• Achieved sufficient signal-to-noise ratio and resolution for monitoring spectral diffusion over extended periods.
• Successfully monitored dynamics orders of magnitude beyond conventional 2D-IR vibrational lifetimes.

Conclusions:

• VIPER 2D-IR spectroscopy, using 2-Isopropylthioxanthone, significantly expands the accessible timescale for studying molecular dynamics.
• This advancement allows for the investigation of slower processes in complex molecular systems previously inaccessible.
• The Fourier-transform approach enhances the practicality and applicability of VIPER 2D-IR for broad scientific research.