2010 年 35 巻 2 号 p. 319-322
The molecular arrangement and surface morphology of organized molecular films of alkylammonium-M bis(1, 3-dithiole-2-thione-4, 5-dithiolate) ((dmit)2, M = Ni, Au, and Pd) charge-transfer complexes were investigated by using the surface pressure-area isotherm, in-plane and out-of plane X-ray diffractions (XRD), and atomic force microscopy. In the bulk state, several alkylammonium-M(dmit)2 molecules could not form a highly ordered layer structure along the c-axis and a sub-cell structure of the alkyl chain in the ab-plane; however, almost all molecules formed a layer structure in the film multilayers. Monolayers of alkylammonium-M(dmit)2 salts on the water surface were relatively condensed. Out-of plane and in-plane XRD measurements revealed that over a long period, systematic changes occurred in the two-dimensional lattice of alkylammonium-M(dmit)2 salts and not in their bulk state. These structural changes appear to be caused by enhancement of the van der Waals interaction among long hydrocarbons and the π-π interaction among M(dmit)2 units arranged two-dimensionally. In addition, both the molecular arrangement and the morphology of the films showed dependence on the hydrocarbon length, number of alkyl chains, and kind of central metal. In particular, the molecular arrangement of materials having didecyl chains changed drastically and M(dmit)2 units were highly oriented in the ab-plane.
