Resonance Raman, infrared, and normal coordinate analysis of free-base tetraphenylbacteriochlorin: A model for bacteriopheophytins

Journal Article · Thu Jan 16 04:00:00 EST 1997 · Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical

DOI:https://doi.org/10.1021/jp962479g· OSTI ID:501884

Lin, C Y; Spiro, T G ^[1]

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1. Princeton Univ., NJ (United States)

Resonance Raman (RR) and FT-IR spectra are reported for free-base tetraphenylbacteriochlorin and its pyrrole-{sup 15}N{sub 4}, {beta}-D{sub 8}, meso-{sup 13}C{sub 4}, and phenyl-D{sub 20} isotopomers. A normal mode analysis is carried out in order to assign observed RR and IR modes, using a NiTPP-based force field, with bond-distance scaling of force constants and the introduction of long-range interaction constants. The modes correlate well with those of NiTPP, once due allowance is made for direct effects of pyrrole ring reduction: inequivalent C{sub {beta}}-C{sub {beta}} and C{sub {alpha}}-C{sub {beta}} bonds and extra C{sub {beta}}-H bending modes. Although the C{sub {alpha}}-C{sub m} and C{sub {alpha}}-N bonds of the 16-membered inner ring are not strictly equivalent, there is little tendency for mode localization with respect to these bonds. The absence of a central metal lowers the frequencies of C{sub {alpha}}-C{sub m} stretching and pyrrole translational modes. The RR enhancement pattern is quite different than for porphyrins. Totally symmetric modes dominate spectra in resonance with the Q{sub x} band, due to a larger transition moment than in porphyrins, while non-totally symmetric modes are strongly enhanced in the region of the close-lying B{sub x} and B{sub y} transitions, reflecting vibronic coupling between them. 38 refs., 11 figs., 7 tabs.

• DOE Contract Number: FG02-93ER14403
• OSTI ID: 501884
• Journal Information: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Journal Name: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical Journal Issue: 3 Vol. 101; ISSN 1089-5647; ISSN JPCBFK
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
99 GENERAL AND MISCELLANEOUS
BACTERIA
CHLORINS
EXPERIMENTAL DATA
INFRARED SPECTRA
MATHEMATICAL MODELS
PHOTOSYNTHETIC REACTION CENTERS
RAMAN SPECTRA
THEORETICAL DATA