Catenane-based Devices

When conferred with a hydrophilic head (in this case a substituted trityl unit), and a hydrophobic (benzylic alcohol) tail, rotaxanes - branched [55] or otherwise - can be formed into Langmuir films in a manner similar to catenanes. Rotaxane 224+ - synthesized from its corresponding thread via the slipping approach - when incorporated into a device in a manner similar to the catenane 214+ also exhibited interesting electron-transport properties [56], Unlike the catenane-based device, there is no switching element built into the molecule. However, like the switchable catenane, the rotaxane 224+ has electroactive bipyridinium sites, whose presence can mediate the tunneling of... 

Two-terminal devices might seem more natural for the molecular-scale systems than three-terminal ones because of the technological difficulties in manipulating small structures. Furthermore, chemical assembly of molecular devices usually results in a periodic structure. This observation resulted in the idea to have a two-terminal switch, electronically reconfigurable, where a relatively high voltage (e.g. —2V or +2V in [62], which uses a 2-catenane-based molecule) (Fig. (7a)) is applied to close or open the switch, but a relatively low voltage to read (M). 1 V) [60]. These molecular switches [62], a mono-layer of rotaxane molecules, are not field-activated but can be described as small electro-chemical cells, which are characterized by... 

Figure 3.42 A model for a catenane-based molecular device. The two orientations of the catenane are redox-switchable by control of the copper oxidation state, (a) The tetrahedral Cu(i) complex and (b) the square-pyramidal Cu(ii) complex.

Balzani, V., Venturi, M., Credi, A. Molecular Devices and Machines. A Jorney into the Nanoworld, Wiley-VCH, Weinheim, 2003 b) Feringa, B.L. (ed.), Molecular Switches, Wiley-VCH, Weinheim, 2001 c) Raehm, L., Sauvage, J.-P. Molecular machines and motors based on transition metal-containing catenanes and rotaxanes, Struct. Bond. 99 (2001), 55-78. 

Figure 17.14 Schematic representation of a solid-state device based on junctions consisting of a monolayer of catenane [ 131 [ I ) 11 A 11 sandwiched between polysilicon and Ti/Al electrodes.115 The structures of 134+ and DMPA- are shown in Fig. 17.12. (Adapted with permission from V. Balzani et al., ChemPhysChem 2008, 9, 202—220. Copyright Wiley-VCH Verlag GmbH Co. KGaA.)...

Fig. 7. The electronically reconfigurable molecular devices based on the [2]catenane 10-4DMPA.

Expected limitations of the miniaturization of silicon based electronics (top-down approach) have led to various attempts to build electronic devices with components of molecular scale (in a bottom-up approach) [169], in particular with complex interconnected supermolecules such as rotaxanes or catenanes [170, 171]. 

Switching devices based on interlocked molecules, catenanes with heterocyclic fragments 01ACR433. 

DNA- and porphyrin-based, linked-ring molecular chains (catenanes) as information storage devices [28, 29]... 

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