Consistent porphyrin force field. 2. Nickel octaethylporphyrin skeletal and substituent mode assignments from sup 15 N, meso-d sub 4 , and methylene-d sub 16 Raman and infrared isotope shifts

Journal Article · Thu Jan 11 00:00:00 EST 1990 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100364a008· OSTI ID:6730026

Li, Xiaoyuan; Czernuszewicz, R S; Spiro, T G ^[1]; Kincaid, J R ^[2]; Stein, P ^[3]

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1. Princeton Univ., NJ (USA)
2. Marquette Univ., Milwaukee, WI (USA)
3. Duquesne Univ., Pittsburgh, PA (USA)

Resonance Raman spectra with variable-wavelength excitation are reported for nickel octaethylporphyrin and its isotopomers containing {sup 15}N, and {sup 2}H at the methine (meso-d{sub 4}) and methylene (methylene-d{sub 16}) carbon atoms. The {sup 15}N, meso-d{sub 4} double isotopomer is also examined. The infrared spectrum of the methylene-d{sub 16} isotopomer is reported, and the frequencies are combined with recently published infrared results for the other isotopomers. Essentially all of the porphyrin skeletal modes have been assigned and have been allocated to local coordinates which recognize the pyrrole rings as cooperative vibrational units. The assignments are supported by a normal-coordinate analysis with a valence force field involving standard ethyl force constants and porphyrin in-plane force constants which are transferred nearly intact from Ni porphine and Ni tetraphenylporphine. Many vibrational modes of the NiOEP ethyl substituents have also been located in the spectra and assigned. Bands assignable to ethyl C-C stretching and C-H bending modes are surprisingly strong in the resonance Raman spectra and suggest appreciable involvement of the ethyl groups in the porphyrin {pi}-{pi}{sup *} excited states. The conformations of the ethyl substituents have a marked influence on the low-frequency vibrational spectra.

• OSTI ID: 6730026
• Journal Information: Journal of Physical Chemistry; (USA), Vol. 94:1; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
59 BASIC BIOLOGICAL SCIENCES
PORPHYRINS
RAMAN SPECTRA
DATA ANALYSIS
EXPERIMENTAL DATA
INFRARED SPECTRA
ISOTOPE EFFECTS
MEASURING INSTRUMENTS
MEASURING METHODS
NICKEL
STRUCTURAL CHEMICAL ANALYSIS
CARBOXYLIC ACIDS
DATA
ELEMENTS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
METALS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
SPECTRA
TRANSITION ELEMENTS
400202* - Isotope Effects
Isotope Exchange
& Isotope Separation
550200 - Biochemistry