Positively and Negatively Charged Porphyrin Metal Complexes That Form Ion-Pairing Assemblies

Abstract

An ordered arrangement of π-electronic species is crucial for the fabrication of functional organic materials such as organic electronic devices including field-effect transistors, light-emitting diodes, and photovoltaic cells. Synergetic uses of electrostatic interactions and other noncovalent interactions, including π–π stacking, is very important for the alignment of π-electronic charged species (cations and anions) and the formation of dimension-controlled assemblies including fiber and sheet solid materials, supramolecular gels, and liquid crystals.[1,2] An advantage of using electrostatic interactions is the formation of various ion-pairing materials by combining constituent π-electronic ions: for example, ten kinds of cations and ten kinds of anions are mixed to ideally provide one hundred kinds of ion pairs. Furthermore, assembling modes can be modulated by constituent ions as well as by the environment, thus exhibiting particular properties according to the arrangement of charged building units even in an ion pair. In this study, porphyrin–AuIII complexes were found to act as π-electronic cations which can combine with various counteranions, including π-electronic anions such as negatively charged porphyrin metal complexes. In the solid-state and soft materials, the formation of assemblies with contributions of charge-by-charge and charge-segregated assemblies, whose ionic components were highly organized by π–π stacking and electrostatic interactions, depended on the geometries and electronic states of constituent ionic species.[3,4]