Nature of Linear Spectral Properties and Fast Relaxations in the Excited States and Two-Photon Absorption Efficiency of 3-Thiazolyl and 3-Phenyltiazolyl Coumarin Derivatives

Yevgeniy O Shaydyuk; Nataliia V Bashmakova; George V Klishevich; Andriy M Dmytruk; Olexiy D Kachkovsky; Iaroslav B Kuziv; Igor Ya Dubey; Kevin D Belfield; Mykhailo V Bondar

doi:10.1021/acsomega.3c00654

Nature of Linear Spectral Properties and Fast Relaxations in the Excited States and Two-Photon Absorption Efficiency of 3-Thiazolyl and 3-Phenyltiazolyl Coumarin Derivatives

ACS Omega. 2023 Mar 16;8(12):11564-11573. doi: 10.1021/acsomega.3c00654. eCollection 2023 Mar 28.

Authors

Yevgeniy O Shaydyuk¹, Nataliia V Bashmakova², George V Klishevich¹, Andriy M Dmytruk¹, Olexiy D Kachkovsky³, Iaroslav B Kuziv⁴, Igor Ya Dubey⁴, Kevin D Belfield⁵, Mykhailo V Bondar¹

Affiliations

¹ Institute of Physics National Academy of Sciences of Ukraine, Prospect Nauki, 46, Kyiv 03028, Ukraine.
² Taras Shevchenko National University of Kyiv, Volodymyrska Street, 60, Kyiv 01601, Ukraine.
³ V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the NAS of Ukraine, Murmanskaya Street, 1, Kyiv 02660, Ukraine.
⁴ Institute of Molecular Biology and Genetics of the NAS of Ukraine, Zabolotnogo Street, 150, Kyiv 03141, Ukraine.
⁵ Department of Chemistry and Environmental Science, College of Science and Liberal Arts, New Jersey Institute of Technology, University Heights, Newark, New Jersey 07102, United States.

Abstract

Coumarin-based fluorescent agents play an important role in the manifold fundamental scientific and technological areas and need to be carefully studied. In this research, linear photophysics, photochemistry, fast vibronic relaxations, and two-photon absorption (2PA) of the coumarin derivatives, methyl 4-[2-(7-methoxy-2-oxo-chromen-3-yl)thiazol-4-yl]butanoate (1) and methyl 4-[4-[2-(7-methoxy-2-oxo-chromen-3-yl)thiazol-4-yl]phenoxy]butanoate (2), were comprehensively analyzed using stationary and time-resolved spectroscopic techniques, along with quantum-chemical calculations. The steady-state one-photon absorption, fluorescence emission, and excitation anisotropy spectra, as well as 3D fluorescence maps of 3-hetarylcoumarins 1 and 2 were obtained at room temperature in solvents of different polarities. The nature of relatively large Stokes shifts (∼4000-6000 cm^-1), specific solvatochromic behavior, weak electronic π → π* transitions, and adherence to Kasha's rule were revealed. The photochemical stability of 1 and 2 was explored quantitatively, and values of photodecomposition quantum yields, on the order of ∼10^-4, were determined. A femtosecond transient absorption pump-probe technique was used for the investigation of fast vibronic relaxation and excited-state absorption processes in 1 and 2, while the possibility of efficient optical gain was shown for 1 in acetonitrile. The degenerate 2PA spectra of 1 and 2 were measured by an open aperture z-scan method, and the maximum 2PA cross-sections of ∼300 GM were obtained. The electronic nature of the hetaryl coumarins was analyzed by quantum-chemical calculations using DFT/TD-DFT level of theory and was found to be in good agreement with experimental data.