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 acheived. 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) commensuarte 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.

Chemical synthesis gets a fillip from molecular recognition and self-assembly processes

“…We speculated that this superstructural order, present in the solid state, might be transferrable by using the LangmuirBlodgett (LB) technique to interfaces and surfaces. And so it transpired that, provided the hexaf luorophosphate counterions are exchanged for dimyristoylphosphatidyl (DMPA Ϫ ) anions (2), catenanes like 5 4ϩ can be introduced into Langmuir films and LB monolayers (17). The (2)catenane tetracations in these multilayers can be considered to reside in a liquid-crystalline-like environment, following what is essentially a simple act of supramolecular synthesis!…”

Single‐Walled Carbon Nanotube Based Molecular Switch Tunnel Junctions

“…Although this original bistable [2]catenane was partially water-soluble as its tetrakis(hexafluorophosphate) salt, when dimyristoylphosphatidyl (DMPA À ) anions were used as the counterions, the [2]catenane tetracations formed high quality Langmuir ± Blodgett (LB) films. [23] We similarly found that the [2]catenane NDC 4 could be prepared [24] as a stable LB monolayer when DMPA À counterions were employed (stoichiometry: 1 NDC 4 :6 DMPA À :2 Na ). We also prepared four control devices.…”

Templated Synthesis of Interlocked Molecules

“…The linear motions of the moving components in a large number of controllable molecular machines distributed randomly in the solution state can be expressed coherently in a mechanical context by organizing them at interfaces [273,[282][283], either as Langmuir-Blodgett (LB) films [284][285][286][287][288] or as self-assembled monolayers (SAMs). Before any multi-scale and integrated devices based on molecular machines become viable for real technological applications, the conditions required to ensure that mechanical switching persists when the molecules are mounted onto solid supports are currently being investigated.…”