Studies in the Cycloproparene Series. The Formation of Charge-Transfer Complexes from 1-Aryl- and 1-Diarylmethylidene-1H-cyclopropa[b]naphthalenes

Abstract

The only charge-transfer (CT) complex formed from (p-dimethylaminophenyl)methylidene-1H-cyclopropa[b]naphthalene 7a is with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) 1 in acetonitrile. The methoxy-, thiomethyl-, and unsubstituted-phenyl analogues 7b–7d complex only with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-1,4-benzoquinodimethane (TCNQF4) 2, and then only in dichloromethane; TCNQ 3, TCNE 4, and the o-CA 5 and p-CA 6 are without effect on any of 7a–7j. In contrast, the bis(dimethylaminophenyl)methylidene homologue 9a complexes with each of 1–5 but is the only diaryl derivative to do so. The polar parent, 1H-cyclopropa[b]naphthalene, does not form a CT complex with any of the acceptors employed.