Organic-Inorganic Molecular Composites as Possible Low-Dimensional Conductors: Photo-Polymerization of Organic Moieties Intercalated in Inorganic Layer Compounds

Abstract

We wish to draw attention to the potential for unusual electronic behaviour in composites formed on a molecular scale between organic and inorganic layer materials. Intercalation of organic molecules in inorganic layer compounds by Van der Waals or donor-acceptor interaction is common but defined stoichiometry and orientation of the organic molecules may be obtained by making salts in which organic cations are bound electrostatically to infinite inorganic anions. Many transition and non-transition metal ions M form halide (X) salts (RNH₃)₂MX₄ where R is a long thin organic moiety, most simply alkyl, and the MX⁴ form infinite layers like a single layer of the cubic perovskite structure. A brief overview of the structures is given but we concentrate on efforts to extend the series to organic cations containing functional groups. Simplest among these are isolated double and triple bonds, e.g. CH₂=CHCH₂NH⁺ ₃ and CH≡CCH₂NH⁺ ₃ but diacetylenic cations have also been employed to give such salts as (CICH₂C≡C-C≡CH₂NH₃)₂CdCl₄ and (-C≡C-CH₂O₂CCH₂NH₃)₂ CdCl₄. The latter polymerize in the solid state, the mono-amino salt much more rapidly than the di-amino.