Planar-nonplanar conformational equilibrium in metal derivates of octaethylporphyrin and meso-nitrooctaethylporhyrin

Journal Article · Wed Dec 29 04:00:00 EST 1993 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00079a015· OSTI ID:5116975

Anderson, K K; Shelnutt, J A ^[1]; Hobbs, J D ^[1]; Luo, L; Stanley, K D; Quirke, J M.E. ^[2]

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1. Sandia National Lab., Albuquerque, NM (United States)
2. Florida International Univ., Miami, FL (United States)

The planar and nonplanar conformers of metal derivatives of 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) and 5-nitro-2,3,7,8,12,13,17,18-octaethylporphyrin (NO[sub 2]-OEP) are investigated using resonance Raman spectroscopy. The structural heterogeneity is assessed by analysis of the line shapes of the structure-sensitive Raman lines. First, heterogeneity in the conformation of the macrocycle has been detected in solutions of the nickel and cobalt derivatives of OEP, that is, both planar and nonplanar conformers are found to coexist at room temperature for these metal porphyrins but not for the Cu and Zn derivatives. The latter metals expand the porphyrin core, shifting the equilibrium entirely to the planar conformer. Second, we find that substitution with a single NO[sub 2] group at one of the methine-bridge carbons shifts this planar-nonplanar equilibrium substantially toward the nonplanar conformer. Thus, both crowding of the peripheral substituents and contracting of the porphyrin core (Ni(II) < Co(II) < Cu(II) < Zn(II)) displace the equilibrium toward the nonplanar conformer. Finally, the frequencies of several Raman lines correlate with structural parameters such as core size (obtained either from molecular mechanics calculations or from X-ray crystallographic studies). 30 refs., 6 figs., 3 tabs.

• DOE Contract Number: AC04-76DP00789
• OSTI ID: 5116975
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 115:26; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical &amp; Physicochemical Properties
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CHLOROPHYLL
COBALT COMPLEXES
COMPLEXES
CONFORMATIONAL CHANGES
COPPER COMPLEXES
CRYSTAL STRUCTURE
DATA
DERIVATIZATION
EQUILIBRIUM
EXPERIMENTAL DATA
HEME
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
MATHEMATICAL MODELS
MOLECULAR STRUCTURE
NICKEL COMPLEXES
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PHYTOCHROMES
PIGMENTS
PORPHYRINS
PROTEINS
RAMAN SPECTRA
SPECTRA
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
ZINC COMPLEXES