Novel semiconducting biomaterials derived from a proline ester and tetracyanoquinodimethane identified by handpicked selection of individual crystals

Complex mixtures of cation : anion stoichometries often result from the syntheses of tetracyanoquinodimethane (TCNQ) salts, and often these cannot be easily separated. In this study, the reaction of N,N-dimethyl-D-proline-methylester (Pro(CH3)(3)(+)) with LiTCNQ resulted in a mixture of crystals. Hand selection and characterisation of each crystal type by X-ray, infrared, Raman and electrochemistry has provided two stoichometries, 1 : 1 [Pro(CH3)(3)TCNQ] and 2 : 3 ([(Pro (CH3)(3))(2)(TCNQ)(3)]). A detailed comparison of these structures is provided. The electrochemical method provides an exceptionally sensitive method of distinguishing differences in stoichiometry. The room temperature conductivity of the mixture is 3.1 x 10(-2) S cm(-1), which lies in the semiconducting range.