Resonance Raman and electronic absorption study of free‐base tetraphenylporphine diacid dispersed in polymethylcyanoacrylate

Abstract

We report a resonance Raman study on free-base tetraphenylporphine (H 2 TPP) and its chemically prepared diacid dispersed in polymethylcyanoacrylate (PMCA). Photoexcitation of the neutral porphine by laser light leads irreversibly to the formation of the diacid, with the p-cation radical as intermediate species.Resonance Raman (RR) spectra of the diacid dispersed in the polymer obtained with 441.6 nm in the wavenumber region of 100-1650 cm −1 are recorded. Wavenumbers with other excitation lines are also reported for the diacid species. Some bands assigned to out-of-plane vibrational modes and forbidden under ideal D 2h symmetry are also observed in the resonance Raman spectra of the diacid. These bands arise from the out-of-plane distortions, which reduce the symmetry of the molecule. These findings are supported by the electronic absorption studies of the diacid in the polymer.

Resonance Raman spectroscopy and density functional theory calculation study of photodecay dynamics of tetra(4-carboxyphenyl) porphyrin

“…The notations and assignments of the vibrations are based on the visualization MOLDEN/MIX software and previous well studied Raman spectra of TCPP were used as valuable references. 18,19 The overall agreement between the DFT calculated vibrational frequencies and the experimental values is good for TCPP. We shall assume in our discussion that the symmetry of the molecule is effectively C 2v , and with this background we are ready to discuss our Raman spectra.…”

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

“…Table 2 B3LYP/6-31G(d) calculated vibrational frequencies with experimental FT-Raman and FT-IR values. The notations and assignments of the vibrations are based on the visualization MOLDEN/MIX software, and those previously studied on the Raman spectra of OEP were used as valuable references [3,14]. The overall agreement between the linear regression scaled DFT calculated vibrational frequencies and the experimental values is good for OEP.…”

“…Among techniques for studying porphyrins in solution, resonant Raman techniques have been widely used [3][4][5][6][7][8][9][10][11]. Resonance Raman Spectroscopy provides overwhelming superiorities over the other spectroscopy techniques with the vibrational mode-specific dynamic information and electronic state-specific information.…”

Short‐time photodecay dynamics of meso‐tetra(p‐hydroxyphenyl)porphine in the condensed phase explored via resonance Raman spectroscopy and density functional theory calculation

“…Table 2 gives a comparison of the B3LYP/6‐31G(d)‐calculated vibrational wavenumbers with the experimental 514‐nm excited micro‐Raman and FT‐IR values. The notations and assignments of the vibrations are based on the visualization MOLDEN/MIX software and on the previous well‐studied Raman spectra of THPP 20, 31. The overall agreement between the linear‐regression‐scaled, DFT‐calculated vibrational wavenumbers and the experimental values is good for THPP.…”

“…The notations and assignments of the vibrations are based on the visualization MOLDEN/MIX software and on the previous well-studied Raman spectra of THPP. [20,31] The overall agreement between the linearregression-scaled, DFT-calculated vibrational wavenumbers and the experimental values is good for THPP. The dihedral angle between the porphyrin mean plane and the phenyl group in the crystalline state is 81.5 • , thereby making the crystal structure of free-base porphin of a lower symmetry with the C 2v point group instead of D 2h .…”