New isoindoline electron acceptors analogous to benzo-TCNQ
Conway, Shane P. (1996) New isoindoline electron acceptors analogous to benzo-TCNQ. PhD thesis, Dublin City University.
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Interest in novel heterocyclic derivatives analogous to TCNQ in which the nelectrons of a carbon-carbon double bond are replaced by a lone pair of electrons on a heteroatom has led to investigation of the synthesis o f A/-alkyl
derivatives of 2,2'-(isoindolin-1,3-diylidene)bispropanedinitrile.
Knoevenagel condensation of A/-methylphthalimide with malononitrile under a number of conditions yielded complex product mixtures from which the sodium and méthylammonium salts of o-(2 ,2-dicyanoethenyl-1 -olate-)/Vmethylbenzamide
and 3-(dicyanomethylidene)phthalide were isolated as minor
Reaction of malononitrile with diiminoisoindoline and 1-phenylimino-3- iminoisoindoline in dimethylformamide yielded the ammonium salt of 2 ,2'- (isoindolin-1,3-diylidene)bispropanedinitrile. In methanol the highly insoluble mono-condensation product was obtained and this was also the product obtained by reaction o f sodio-malononitrile with phthalonitrile in methanol. 2 ,2'-
(lsoindolin-1,3-diylidene)bispropanedinitrile was obtained from its ammonium salt by acidification.
Reaction of 2,2'-(isoindolin-1,3-diylidene)bispropanedinitrile or its ammonium salt with a variety of acylating and alkylating agents did not yield the
desired compounds. A very low yield of 2,2'-(2-methyl-isoindolin-1,3-diylidene)bispropanedinitrile was obtained on reaction with dimethylsulphate.
Reaction of the ammonium salt with a variety of amines yielded products which X-ray crystallography showed to arise from amine addition across a cyano group. 2,2'-(2-Methyl-isoindolin-1,3-diylidene)bispropanedinitrile was
successfully synthesised by heating the tétraméthylammonium salt of 2 ,2'-(isoindolin-1,3-diylidene)bispropanedinitrile in 1,2-dichlorobenzene.
Cyclic voltammetry measurements of the 2,2'-(isoindolin-1,3-diylidene) bispropanedinitriles show they are electrochemically irreversible. UV studies of the charge-transfer complexing abilities of 2,2'-(isoindolin-1,3-
diylidene)bispropanedinitrile and its A/-methyl derivative with a variety of electron donors were carried out and a number of charge-transfer complexes have been synthesised. X-ray crystallography of the 1:1 complex between
2,2'-(isoindolin-1,3-diylidene)bispropanedinitrile and N,N,N',N'-teiramethy\-pphenylenediamine shows that it crystallises in a mixed stacking arrangement.
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