TY  - JOUR
A1  - Bock, Hans
A1  - Hänel, Peter
A1  - Herrmann, Hans-Friedrich
T1  - Elektronentransfer und Ionenpaar-Bildung, 28. ESR/ENDOR-Untersuchungen an Radikalanionen und Kontakt-Ionenpaaren der Naturstoff-Chinone Mitomycin C, Streptonigrin, Entobex® und 10,11-Dioxobrucin
T1  - Electron transfer and ion pairing, 28. ESR/ENDOR studies of radical anions and contact ion pairs of the naturally occurring quinones Mitomycine C, Streptonigrine, Entobex® and 10,11-dioxobrucine
T2  - Zeitschrift für Naturforschung, B
N2  - Reduction of naturally occurring para-and ortho-benzoquinone derivatives M to their respective radical anions M·⊖ can be accomplished under largely aprotic conditions either by cautious low-temperature reaction in THF containing an excess of (2.2.2) cryptand at a potassium mirror or by using the "mild" single electron transfer reagent tetrabutylammonium boranate R4N⊕BH4⊖ in DMF. On addition of soluble alkali tetraphenylborates Me⊕[B(C6H5)4]⊖ , their hitherto unknown radical ion pairs [M·⊖ Me⊕]· and/or triple ion radical cations [Me⊕M·⊖Me⊕]·⊕ form, which might be of biological relevance in molecular carrier and "turn off -turn on" switch processes. On addition of metal perchlorates Me⊕n(ClO4⊖)n with multiply charged counter cations Me⊕n the respective paramagnetic species [M·⊖Me⊕n]·(n-1)⊕ result. Assuming exclusive one-electron transfer reductions without any redox fragmentation reac­tions, ESR, ENDOR and GENERAL TRIPLE spectra are presented and discussed for the following radical anions and radical ion pairs: mitomycin C (M·⊖ and [M·⊖Mex⊕]·(x-1)⊕ with Me⊕ = Li⊕, Na⊕), streptonigrine (M·⊖ and [M·⊖Lix⊕]·(x-1)⊕), Entobex® (M·⊖ and [M·⊖Me⊕n]·(n-1)⊕ with Me⊕n = Li⊕, Na⊕, Cd⊕⊕, (H5C6)2Tl⊕) as well as brucinequinone ([M·⊖ Me⊕n]·(n-1)⊕ with Me⊕n = Li⊕, Cd⊕⊕, Pb⊕⊕, La⊕⊕⊕).
KW  - Natural Quinones
KW  - Radical Anions
KW  - Contact Ion Pairs
KW  - ESR/ENDOR Spectra
Y1  - 2014
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/81530
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-815303
SN  - 1865-7117
SN  - 0932-0776
VL  - 47.1992
IS  - 4
SP  - 533
EP  - 546
PB  - Verlag der Zeitschrift für Naturforschung
CY  - Tübingen
ER  -