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

The formation of Langmuir films comprised of (i) dimyristoylphosphatidic ac id and a [2] catenane composed of a bisparapheylene-34-crown-10 with its tw o pi-electron-rich hydroquinone rings and the pi-electron-deficient cycloph ane 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 pi-electron-deficient cyclophane bis(p araquat-p-phenylene), has been acheived. Utilizing Pi-A isotherms and isoch ore measurements, it is possible to determine the optimum ratio of phosphol ipid to [2]catenane for good Langmuir film formation and to interpret these experimental findings in terms of intermolecular pi-pi interactions betwee n the [2]catenane tetracations in the Langmuir films. They have been transf erred via the Langmuir-Blodgett technique to hydrophobized quartz supports, and, through a combination of W-vis spectroscopy and small-angle X-ray sca ttering (SAXS), it has been established that the Langmuir films are deposit ed onto the support without loss of the [2]catenane tetracations (UV-vis) a nd that the transfer results in a periodic layer structure (SAXS) commensua rte with the expected bilayer thickness of the phospholid and the [2]catena ne. It is proposed that such films containing mechanically interlocked mole cules, which have switchable characteristics, at least in the solution stat e, may be suitable candidates for spatially addressable information storage materials.