Open AccessThree-Photon Spectroscopy of Porphyrins
Author(s) -
Luca Ravotto,
Stephen L. Meloni,
Tatiana V. Esipova,
Artëm E. Masunov,
Jessica M. Anna,
Sergei A. Vinogradov
Publication year - 2020
Publication title -
the journal of physical chemistry. a/the journal of physical chemistry. a.
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.756
H-Index - 235
eISSN - 1520-5215
pISSN - 1089-5639
DOI - 10.1021/acs.jpca.0c08334
Subject(s) - chromophore , chemistry , spectroscopy , phosphorescence , time dependent density functional theory , density functional theory , chemical physics , photochemistry , computational chemistry , optics , fluorescence , physics , quantum mechanics
Recent advances in laser technology have made three-photon (3P) microscopy a real possibility, raising interest in the phenomenon of 3P absorption (3PA). Understanding 3PA of organic chromophores is especially important in view of those imaging applications that rely on exogenous probes, whose optical properties can be manipulated and optimized. Here, we present measurements and theoretical analysis of the degenerate 3PA spectra of several phosphorescent metalloporphyrins, which are used in the construction of biological oxygen probes. The effective 3PA cross sections (σ (3) ) of these porphyrins near 1700 nm, a new promising biological optical window, were found to be on the order of 1000 GM3 (1 GM3 = 10 -83 cm 6 s 2 ), therefore being among the highest values reported to date for organic chromophores. To interpret our data, we developed a qualitative four-state model specific for porphyrins and used it in conjunction with quantitative analysis based on the time-dependent density functional theory (TDDFT)/ a posteriori Tamm-Dancoff approximation (ATDA)/sum-over-states (SOS) formalism. The analysis revealed that B (Soret) state plays a key role in the enhancement of 3PA of porphyrins in the Q band region, while the low-lying two-photon (2P)-allowed gerade states interfere negatively and diminish the 3PA strength. This study features the first systematic examination of 3PA properties of porphyrins, suggesting ways to improve their performance and optimize them for imaging and other biomedical applications.