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Titolo:
Vibrational analysis of metalloporphyrins with electron-withdrawing NO2 substituents at different meso positions
Autore:
Lemke, C; Schweitzer-Stenner, R; Shelnutt, JA; Quirke, JME; Dreybrodt, W;
Indirizzi:
Univ Puerto Rico, Dept Chem, San Juan, PR 00931 USA Univ Puerto Rico San Juan PR USA 00931 Dept Chem, San Juan, PR 00931 USA Univ Bremen, Inst Phys Expt, D-28359 Bremen, Germany Univ Bremen Bremen Germany D-28359 st Phys Expt, D-28359 Bremen, Germany Sandia Natl Labs, Biomol Mat & Interfaces Dept, Albuquerque, NM 87815 USA Sandia Natl Labs Albuquerque NM USA 87815 Dept, Albuquerque, NM 87815 USA Univ New Mexico, Dept Chem, Albuquerque, NM 87131 USA Univ New Mexico Albuquerque NM USA 87131 Chem, Albuquerque, NM 87131 USA Florida Int Univ, Dept Chem, Miami, FL 33199 USA Florida Int Univ Miami FL USA 33199 Univ, Dept Chem, Miami, FL 33199 USA
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY A
fascicolo: 27, volume: 105, anno: 2001,
pagine: 6668 - 6679
SICI:
1089-5639(20010712)105:27<6668:VAOMWE>2.0.ZU;2-N
Fonte:
ISI
Lingua:
ENG
Soggetto:
RESONANCE-RAMAN; CONFORMATIONAL PROPERTIES; EXCITATION PROFILES; ISOTOPE SHIFTS; HEME-PROTEINS; FORCE-FIELD; IR-SPECTRA; PORPHYRINS; OCTAETHYLPORPHYRIN; SPECTROSCOPY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
35
Recensione:
Indirizzi per estratti:
Indirizzo: Schweitzer-Stenner, R Univ Puerto Rico, Dept Chem, Rio Piedras Campus,POB 23346, San Juan, PR 00931 USA Univ Puerto Rico Rio Piedras Campus,POB 23346San Juan PR USA 00931
Citazione:
C. Lemke et al., "Vibrational analysis of metalloporphyrins with electron-withdrawing NO2 substituents at different meso positions", J PHYS CH A, 105(27), 2001, pp. 6668-6679

Abstract

The structure of metalloporphyrins is to a major extent determined by its peripheral substituents: To explore the influence of NO2 meso substituents,we have measured polarized resonance Raman spectra of Ni(II)(5-NO2-octaethylporphyrin) and NI(II)(5,15-NO2-octaethylporphyrin) at various excitation wavelengths in the Soret and Q band region in CS2. We obtained very complexand overcrowded spectra that were self-consistently analyzed by a global fitting procedure. This revealed that numerous Raman Lines in the Raman frequency region are composed of sublines. This includes all prominent structural marker lines. Thus, we found that for both substances at least three conformers coexist in solution. The resonance excitation profiles of the corresponding sublines indicate that these conformers exhibit different degrees of nonplanarity. Altogether, the data suggest that the nitro groups destabilize the porphyrin macrocycle and increase conformational heterogeneity. Wealso performed a normal-mode calculation with a spectroscopically determined molecular mechanics force field for a nonplanar structure of Ni(II)(5,(5-NO2-octaethylporphyrin). This revealed that the NO2 substituents lower thesymmetry of some vibrations by vibrational mixing (e.g., for v(4)) and by changing the eigenvectors in particular of low-frequency modes (e.g., of v(8)).

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Documento generato il 09/08/20 alle ore 23:03:21