ISSN:
0377-0486
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The resonance Raman spectra of side-on type dioxygen adducts of Mn(TMP), Mn(TPP) and Mn(OEP), where TMP, TPP and OEP denote the dianions of tetramesityl-, tetraphenyl- and octaethyl-porphines, respectively, were measured in O2-Ar(1 : 30) matrices at ca. 15 K. The bands near 990, 710 and 430 cm-1 were assigned to ν(O2), νs(Mn—O) and νa(Mn—O), respectively, based on 16O2/18O2 isotopic shifts and normal coordinate calculations on an isosceles MnO2 moiety. Vibrational coupling between the νs (Mn—O) and porphyrin modes obscured the location of the former mode in the spectra of Mn(TPP)O2 and Mn(OEP)O2. The bands near 825 cm-1 which appear in all three porphyrins are shifted 34-36 cm-1 on 16O2/18O2 substitution. Evidence is presented to show that this band is due to the ν(Mn=O) of oxomanganese(IV) porphyrin, which was produced by photo-cleavage of the O—O bond of the dioxygen adduct. These ν(Mn=O) are ca. 70 cm-1 higher than those observed in acetonitrile solution. This has been attributed to the difference in the spin state; the oxomanganese(IV) porphyrins in acetonitrile solution are of high spin whereas those produced in O2-Ar matrices are of low spin.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jrs.1250220603
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