Introduction of [2]catenanes into Langmuir films and Langmuir-Blodgett multilayers. A possible strategy for molecular information storage materials

Abstract

The formation of Langmuir films comprised of (i) dimyristoylphosphatidic acid and a [2]catenane composed of a bisparapheylene-34-crown-10 with its two π-electron-rich hydroquinone rings and the π-electron-deficient cyclophane bis(paraquat-p-phenylene) and (ii) dimyristoylphosphatidic acid and a [2]catenane composed of a macrocyclic polyether containing two hydroquinone rings and an azobenzene unit and the π-electron-deficient cyclophane bis(paraquat-p-phenylene), has been achieved. Utilizing Π-A isotherms and isochore measurements, it is possible to determine the optimum ratio of phospholipid to [2]catenane for good Langmuir film formation and to interpret these experimental findings in terms of intermolecular π-π interactions between the [2]catenane tetracations in the Langmuir films. They have been transferred via the Langmuir-Blodgett technique to hydrophobized quartz supports, and, through a combination of UV-vis spectroscopy and small-angle X-ray scattering (SAXS), it has been established that the Langmuir films are deposited onto the support without loss of the [2]catenane tetracations (UV-vis) and that the transfer results in a periodic layer structure (SAXS) commensurate with the expected bilayer thickness of the phospholid and the [2]catenane. It is proposed that such films containing mechanically interlocked molecules, which have switchable characteristics, at least in the solution state, may be suitable candidates for spatially addressable information storage materials.