Resonance Raman characterization of the radical anion and triplet states of zinc tetraphenylporphine

Journal Article · Thu Nov 28 04:00:00 EST 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100177a024· OSTI ID:6770887

Reed, R A; Purrello, R; Prendergast, K; Spiro, T G ^[1]

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1. Princeton Univ., NJ (United States)

The photophysical properties of metalloporphyrins are important to a range of current research areas, ranging from solar energy conversion to photodynamic therapy. Resonance Raman (RR) spectra are reported for the anion radical and for the photoexcited triplet state of ZnTPP. RR spectra were obtained by excitation at 457.9 nm, at the anion absorption band maximum. Bands were assigned with the aid of pyrrole-d[sub 8] and phenyl-d[sub 20] isotopomers. The pattern of isotope shifts and polarizations was found to be quite similar to that of the neutral parent, ZnTPP. The frequency shift pattern is discussed in terms of the expectations for placing an electron in the e[sub g]* orbital, including the anticipated Jahn-Teller (J-T) effect. Although band overlaps make depolarization ratios difficult to quantitate, the [nu][sub 10] band is found to be essentially depolarized, indicating that the J-T effect is dynamic, rather than static in character, at least with respect to stretching of the C[sub a]C[sub m] bonds. The [nu][sub 2] and [nu][sub 10] downshifts are attributable to porphyrin core expansion upon reduction, but the [nu][sub 27] and [nu][sub 29] reductions are probably manifestations of the J-T effect. Triplet-state RR spectra were produced with 416-nm photolysis and 459-nm probe pulses (7 ns). The RR peaks were assigned via their polarizations and the d[sub 8] and d[sub 20] isotopomer shifts. The spectrum contains three strong bands of predominantly phenyl character. Their frequencies are unshifted relative to the ground state, implying negligible electronic involvement of the phenyl groups in the T[sub 1] state, but their enhancements indicate substantial involvement in the resonant T[sub n] state. This state is suggested to be produced by charge transfer from the porphyrin e[sub g]* to the phenyl [pi]* orbitals.

• DOE Contract Number: AC02-81ER10861
• OSTI ID: 6770887
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:24; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505 -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102* -- Chemical & Spectral Procedures
ANIONS
CARBOXYLIC ACIDS
CHARGED PARTICLES
COMPLEXES
DATA
ELECTRONIC STRUCTURE
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
IONS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PORPHYRINS
RADICALS
RAMAN SPECTRA
SPECTRA
VIBRATIONAL STATES
ZINC COMPLEXES