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Transient Absorption Spectroscopy of a Carbazole-Based Room-Temperature Phosphorescent Molecule: Real-Time Monitoring of Singlet-Triplet Transitions. | LitMetric

Transient Absorption Spectroscopy of a Carbazole-Based Room-Temperature Phosphorescent Molecule: Real-Time Monitoring of Singlet-Triplet Transitions.

J Phys Chem Lett

Henan Key Laboratory of Infrared Materials & Spectrum Measures and Applications, School of Physics, School of Environment, Henan Normal University, 46# East of Construction Road, Xinxiang 453007, Henan, China.

Published: October 2022

AI Article Synopsis

  • Real-time monitoring of singlet-triplet transitions helps analyze room-temperature phosphorescent molecules, particularly using femtosecond transient absorption spectroscopy on a specific molecule in DMSO.
  • The study found that stimulated emission and excited-state absorption signals peaked at 397 fs, followed by a decay and an increase in triplet-triplet absorption, indicating intersystem crossing occurred within 2.5 ns.
  • Additionally, the TTA signal faded over time, with phosphorescence observed lasting 4.1 μs, while changes in solvent polarity affected the duration of intersystem crossing and phosphorescence lifetimes.

Article Abstract

Real-time monitoring of singlet-triplet transitions is an effective tool for studying room-temperature phosphorescent molecules. For femtosecond transient absorption (TA) spectroscopy of a 2,6-di(9-carbazol-9-yl) pyridine molecule in dimethyl sulfoxide (DMSO), the stimulated emission signal (380 nm) and the excited-state absorption signal (650 nm) reach their maximum intensity within 397 fs. Subsequently, the two signals decay with time and the triplet-triplet absorption (TTA) signal (400 nm) is enhanced synchronously, accompanied by an isosbestic point at 491 nm. These results confirm intersystem crossing (ISC) within 2.5 ns. Moreover, the TTA signal (400 nm) in nanosecond TA spectroscopy gradually disappeared, accompanied by a phosphorescence lifetime of 4.1 μs. As the solvent polarity decreases (DMSO > ,-dimethylformamide > 1,4-dioxane > toluene), similar spectral dynamic processes are observed, while the durations of ISC processes and phosphorescence lifetimes are shortened. This combined femtosecond and nanosecond transient absorption spectroscopy study presents the ultrafast excited-state dynamics of organic phosphorescent molecules.

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Source
http://dx.doi.org/10.1021/acs.jpclett.2c02519DOI Listing

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