Switchable Molecular Devices: From Rotaxanes to Nanoparticles

Abstract

Rotaxanes have been used as molecular frameworks for the preparation of switchable or bistable systems. The properties of a rotaxane that can be switched by electrochemical and chemical means are described in detail and used as an example in this discussion. The advantages of the rotaxane framework compared to systems containing the individual active components mixed together are considered. A series of practical problems hindering the application of single-molecule devices in actual circuits are discussed. Finally, some emerging alternatives to single-molecule devices based on the quickly growing ®eld of metal and semiconductor nanoparticles are brie¯y described.

Origin of Co-Conformational Selectivity in a [3]rotaxane

“…Given that the functionality of molecular nano devices is embodied in their gross structural features, the ability to reliably reproduce these gross features suggest that the modeling technique may be useful to accelerate iterative molecular design and refinement for targeted mechanical properties. a Each [2]rotaxane is formed by deleting one ring from the full [3]rotaxane complex. pos3 denotes a co-conformation with one ring binding at position 3, and pos7 denotes a co-conformation with one ring binding at position 7…”

Artificial Molecular Rotors

“…The important and popular subject of rotation in catenanes and rotaxanes has been reviewed elsewhere, − and we will only briefly mention a few isolated examples. The reader is referred to review articles dealing with catenanes and rotaxanes of the Stoddart type, − of the Sauvage type, − of the amide type, − with catenated cyclodextrins, , and with dendrimeric rotaxanes .…”

“…The important and popular subject of rotation in catenanes and rotaxanes has been reviewed elsewhere, [24][25][26] and we will only briefly mention a few isolated examples. The reader is referred to review articles dealing with catenanes and rotaxanes of the Stoddart type, [27][28][29][30][31][32][33][34][35][36] of the Sauvage type, [37][38][39][40][41][42][43][44][45] of the amide type, [46][47][48][49][50] with catenated cyclodextrins, 51,52 and with dendrimeric rotaxanes. 53 A useful article by Willner and collaborators touches on many issues concerning the use of photoisomerization in possible molecular devices, with an emphasis on rotaxanes and catenanes.…”

Integrated Nanoparticle–Biomolecule Hybrid Systems: Synthesis, Properties, and Applications

“…Composite layered or aggregated structures of (macro)molecule-cross-linked NPs on surfaces have been prepared, [13] and specific sensing of substrates, [13a] tunable electroluminescence, [13b] and enhanced photoelectrochemistry [14] have been observed. The assembly of NP architectures on surfaces has also led to the fabrication of nanoscale devices such as single-electron transistors, [15] NPbased molecular switches, [16] and metal-insulator-nanoparticle-insulator-metal (MINIM) capacitors. [17] Several reviews have addressed the recent advances in the synthesis and properties of nanoparticles [7,18] and the progress made in the integration of composite nanoparticle systems with surfaces.…”