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Inne
Iron complexes of C- and N-methylated 2-aza-21-carbaporphyrin: NMR studies.
Autorzy
Rok wydania
2006
Czasopismo
Numer woluminu
45
Strony
9742-9747
DOI
10.1021/ic061092h
Kolekcja
Język
Angielski
Typ publikacji
Artykuł
Insertion of iron(II) into methylated derivatives of N-confused porphyrins 2-aza-2-methyl-5,10,15,20-tetraphenyl-21-carbaporphyrin (MeCTPPH)H, 2-aza-5,10,15,20-tetraphenyl-21-methyl-21-carbaporphyrin (CTPPMe)H2, and 2-aza-2-methyl-5,10,15,20-tetraphenyl-21-methyl-21-carbaporphyrin (MeCTPPMe)H yielded N- or C-methylated high-spin iron(II) complexes (MeCTPPH)FeIIBr, (HCTPPMe)FeIIBr, and (MeCTPPMe)FeIIBr. One electron oxidation of (Me-CTPPH)FeIIBr using Br2, accompanied by deprotonation of a C(21)−H(21) fragment and formation of an Fe−C(21) bond, produces an intermediate-spin, five-coordinate iron(III) complex (MeCTPP)FeIIIBr. Simultaneously, a high-spin complex [(MeCTPPH)FeIIIBr]+ was formed which preserved the side-on interaction between the metal ion and the inverted pyrrole ring. [(MeCTPPH)FeIIIBr]+ was also obtained by titration of (MeCTPP)FeIIIBr with TFA due to the C(21) protonation. A titration of (HCTPPMe)FeIIBr and (MeCTPPMe)FeIIBr with Br2 yielded solely corresponding high-spin iron(III) species [(HCTPPMe)FeIIIBr]+ and [(MeCTPPMe)FeIIIBr]+. Dioxygen reacts cleanly with (MeCTPPH)FeIIBr carbaporphyrin to form solely (MeCTPP)FeIIIBr. The 1H NMR spectra of paramagnetic iron(II) and iron(III) complexes were examined. The characteristic patterns of pyrrole, C-methyl, and N-methyl resonances were found diagnostic of the ground electronic state of iron and the coordinating nature of the N-confused pyrrole. The characteristic C−Me resonances occur in a unique window (520−420 ppm) for iron(III) C-methylated N-confused porphyrins which remains in contrast with relatively small values found for iron(II) C-methylated derivatives (50−80 ppm).
Słowa kluczowe
Iron, Nuclear magnetic resonance spectroscopy, Oxidation, Pyrroles, Resonance structures
Adres publiczny
https://doi.org/10.1021/ic061092h
Strona internetowa wydawcy
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