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Titolo:
STRUCTURAL HETEROGENEITY AND COORDINATION CHEMISTRY OF NICKEL(II) OCTAETHYL-MESO-NITROPORPHYRINS
Autore:
HOBBS JD; MAJUMDER SA; LUO L; SICKELSMITH GA; QUIRKE JME; MEDFORTH CJ; SMITH KM; SHELNUTT JA;
Indirizzi:
SANDIA NATL LABS,DEPT FUEL SCI,POB 5800 ALBUQUERQUE NM 87185 UNIV NEW MEXICO,DEPT CHEM ALBUQUERQUE NM 87131 FLORIDA INT UNIV,DEPT CHEM MIAMI FL 33199 LAWRENCE LIVERMORE NATL LAB,DEPT CHEM DAVIS CA 95616
Titolo Testata:
Journal of the American Chemical Society
fascicolo: 8, volume: 116, anno: 1994,
pagine: 3261 - 3270
SICI:
0002-7863(1994)116:8<3261:SHACCO>2.0.ZU;2-4
Fonte:
ISI
Lingua:
ENG
Soggetto:
RESONANCE RAMAN-SPECTRA; NUCLEAR MAGNETIC-RESONANCE; N-15 SUBSTITUTED DERIVATIVES; LIGHT-ABSORPTION PROPERTIES; PORPHYRIN FORCE-FIELD; PHOTOSYNTHETIC CHROMOPHORES; METAL-COMPLEXES; ZINC-COMPLEXES; NMR-SPECTRA; MODELS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
57
Recensione:
Indirizzi per estratti:
Citazione:
J.D. Hobbs et al., "STRUCTURAL HETEROGENEITY AND COORDINATION CHEMISTRY OF NICKEL(II) OCTAETHYL-MESO-NITROPORPHYRINS", Journal of the American Chemical Society, 116(8), 1994, pp. 3261-3270

Abstract

The role of steric crowding of peripheral substituents in causing nonplanar distortions of the porphyrin macrocycle has been investigated in a series of nickel(II) meso-nitrooctaethylporphyrins as models for protein-induced nonplanar distortions of metal-tetrapyrrole cofactors. UV-visible absorption spectra, resonance Raman spectra, nuclear magnetic resonance spectra, and molecular mechanics calculations are given for nickel(II) derivatives of 5-mono-, 5,15-di-, 5,10-di-, 5,10,15-tri-, and 5,10,15,20-meso-nitro-substituted octaethylporphyrins. The frequencies of the structure-sensitive Raman lines are found to shift to lower energies in response to sterically induced nonplanar distortion ofthe porphyrin macrocycle rather than in response to the addition of astrong electron-withdrawing nitro substituent. The Raman spectra of all except tetranitrooctaethylporphyrin show spectroscopic evidence of heterogeneity resulting from the presence of conformers with differingdegrees of nonplanarity. Evidence from UV-visible absorption spectra,nuclear magnetic resonance spectra, and molecular mechanics calculations suggests that nickel tetranitrooctaethylporphyrin in solution may exhibit conformers with different types of nonplanar distortions whichhowever do not differ in the relative degree of distortion. We find that the effect of increasing distortion on the chemical reactivity with axial ligating agents, which normally acts to lower the affinity, isovercome in the case of the nitrooctaethylporphyrin series by the increasing electron depletion of the porphyrin ring as the number of nitro substituents increases.

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Documento generato il 18/09/20 alle ore 09:43:53