Die unterschiedlichen Strukturen des im Kristall verdrillten 1,4-Bis(tricyanvinyl)- benzols sowie des eingeebneten 1-Tricyanvinylbenzols, Dichtefunktional- Berechnungen und cyclovoltammetrisch sowie ESR/ENDOR-spektroskopisch charakterisiertes Reduktionsverhalten

H an s B o ck 3*, W olfgang Seitz3, N o rb e rt N agel3, R ü d ig er B a u rb, Jan W. B a ts3, Z d e n e k H av la sc, R odney F. C. C laridged a Chemische Institute der Universität Frankfurt, Marie-Curie-Str. 11, D-60439 Frankfurt am Main b Hoechst AG, Postfach 800320, D-65926 Frankfurt/Main c Institut für Organische Chemie und Biochemie, Tschechische Akademie der Wissenschaften, Flemingova Nam 2, CZ-11610 Prag 6, Tschechien d Chemie-Department, Universität Canterbury, Christchurch, Neuseeland Z. Naturforsch. 52b, 1125-1138 (1997); eingegangen am 2. Juni 1997 Tricyanovinyl Benzene Derivatives, Crystal Structure, Density Functional Calculations, ESR/ENDOR Measurements The attem pted crystal growth of l,4-bis(tricyanovinyl)benzene dianion salts, although wi­ thout success so far, has provided information of general interest. The crystal structures of the related mono and l,4-bis(tricyanovinyl)benzene derivatives differ considerably in their substituent group twisting angles: The two tricyanovinylbenzenes in split-positions exhibit dihedral angles of only 6° or 11°, whereas the two C2(CN)3 groups of the disubstituted benzene are conrotationally twisted by 48° out of the benzene plane. Density functional calculations with 6-311++G** basis sets, however, predict identical values of 32° for both compounds and, therefore, their crystal arrangements are discussed in detail for packingenforced additional interactions. Cyclovoltammetric and ESR/ENDOR-measurements pro­ vide information on the redox behaviour, a prerequisite for attempts to crystallize molecular anion salts: The 1,4-disubstituted derivative with a cyclovoltammetrically determined half­ wave reduction potential of +.14 V in aprotic THF solution proves to be one of the strongest polycyano-substituted ^--acceptors and its radical anion can be selectively generated by T1 metal reduction as confirmed by its ESR/ENDOR spectra. Wechselwirkungen in Molekülkristallen, 127 [1]