Polarization‐sensitive CARS spectroscopy on free‐base porphyrins: coproporphyrin I tetramethyl ester

Abstract

The application of polarization-sensitive (PS) coherent anti-Stokes Raman scattering (CARS) spectroscopy for the investigation of highly luminescent free-base porphyrins under Q x band resonance is discussed. For coproporphyrin I tetramethyl ester (CP-I-TME), PS CARS spectra involving resonances with the electronic Q x absorption band as well as polarized spontaneous Raman spectra involving B band resonance are presented. A quantitative evaluation of the CP-I-TME spectra is performed and the results are compared to our previously presented data on free-base octaethylporphine (OEP) and mesoporphyrin IX dimethyl ester (MP-IX-DME), which were obtained under identical excitation conditions. This comprehensive analysis reveals several spectral differences that can be attributed to the different b-substitution pattern of the porphyrin macrocycle. Additionally, the strong resonance enhancement of totally symmetric modes under Q x band excitation is identified as a common property for OEP, CP-I-TME, and MP-IX-DME; this enhancement selectivity distinguishes the investigated substances from what is generally observed for metallo porphyrins.

Photodecay dynamics of octaethylporphine in the condensed phase explored via resonance Raman spectroscopy and density functional theory calculation

“…Under this condition, the amount of fluorescence overlaying the spectra is tolerable. Pre-resonance Raman spectra have already been obtained in previous studies for MP-IX-DME with B-and Q yband excitation [15,16]. In contrast to the study [17][18][19][20] which focuses on the investigation of low-wavenumber vibrations to monitor out-of-plane distortions of the porphyrin macrocycle, our study intends to examine the 500-2000 cm −1 spectral region in detail and to report a preliminary resonance Raman analysis of the short-time excited state dynamics of octaethylporphine (OEP) in its B-and Q-band absorptions and to find higher energy excited state that vibronically coupled to B x -band.…”

Label-Free Imaging of Lipophilic Bioactive Molecules during Lipid Digestion by Multiplex Coherent Anti-Stokes Raman Scattering Microspectroscopy

“…It has proven to be an invaluable tool to investigate problems across a range of scientific disciplines. [15][16][17][18] Recent efforts to extend the spectral bandwidth of multiplex CARS using supercontinuum sources 19,20 or pulse shaping 21,22 further extend the applicability of this technique. Raman microspectroscopy and single-frequency CARS microscopy have also been used extensively in cell and tissue biology to acquire images based on vibrational contrast exhibited by different chemical species.…”

“…Multiplex CARS microspectroscopy is a chemically specific, label-free, non-invasive form of hyperspectral imaging with submicrometer spatial resolution in which the contrast in an image is derived from molecular vibrations. − As such, one is able to identify different chemical species directly due to the unique vibrational fingerprints shown by different molecules. It has proven to be an invaluable tool to investigate problems across a range of scientific disciplines. − Recent efforts to extend the spectral bandwidth of multiplex CARS using supercontinuum sources , or pulse shaping , further extend the applicability of this technique. Raman microspectroscopy and single-frequency CARS microscopy have also been used extensively in cell and tissue biology to acquire images based on vibrational contrast exhibited by different chemical species. − …”

Editorial

“…These include: a study on polarization-sensitive CARS spectroscopy of free-base porphyrins; [1] a study on the ultrafast bimolecular radical reaction between S 1 p-terphenyl and carbon tetrachloride; [2] a time-resolved resonance Raman and density functional theory study of the deprotonation reaction of the triplet state of para-hydroxybenzophenone in mixed acetonitrile/water solutions; [3] an investigation of femtosecond Raman-induced Kerr effect spectroscopy; [4] a paper on ultrafast vibrational dynamics and solvation complexes of methyl acetate in methanol studied by sub-picosecond infrared spectroscopy; [5] an ultrafast dynamics and photochemistry study of π − π * excited trans-azobenzene; [6] a paper on ultrafast dynamics in Cu(I)bisdiimine complexes from resonance Raman intensities; [7] a three-state model for femtosecond broadband stimulated Raman scattering; [8] a picosecond time-resolved ultraviolet resonance Raman study on photoinduced electron transfer in glucose oxidase; [9] a study on molecular vibrational imaging of a human cell by multiplex coherent anti-Stokes Raman scattering microspectroscopy using a supercontinuum light source; [10] a paper on characteristic wavenumber shifts of the stimulated Raman scattering from interfacial water molecules induced by laser-induced plasma generation at air-water and water-silver interfaces; [11] a study on the identification of chemical species of fluorescein isothiocyanate isomer-I (FITC) monolayers on platinum by doubly resonant sum-frequency generation spectroscopy; [12] a work on coherent acoustic phonons in a thin gold film probed by femtosecond surface plasmon resonance; [13] a review of recent advances in linear and nonlinear Raman spectroscopy; [14] an investigation of the halide-ion-assisted increase of surfaceenhanced hyper-Raman scattering; [15] and finally a study on ultrafast Raman loss spectroscopy [16] . …”