Nanovalves

Abstract

This article features both molecular and supramolecular chemistry involving: i) stimuli‐induced nanoscale movements within mechanically interlocked molecules; ii) the fabrication of mesoporous silica substrates; and iii) the integration of the mechanically interlocked molecular/supramolecular actuators to act as gatekeepers at the entrances to the silica nanopores into which guest dye molecules can be uploaded and released on demand from the mesoporous silica substrates. The supramolecular actuators are based on two [2]pseudorotaxanes—that is, 1:1 complexes that can be dissociated by external inputs, such as acid/base cycles, electrons, and light. The molecular actuators are based on bistable [2]rotaxanes and can be operated mechanically by using either redox chemistry or electrochemistry. After these pseudorotaxanes and bistable rotaxanes have been attached covalently to the orifices of the silica nanopores, stimuli‐controlled mechanical movements within these mechanically interlocked molecules can be harnessed to close and open the nanopores. Therefore, these mechanically interlocked molecules have been employed as nanovalves for controlled sequestering and release of guest dye molecules into and out of the mesoporous silica substrates. These actuators can be regarded as the prototypes of highly controllable drug‐delivery systems.

Molecules in Glass: Probes, Ordered Assemblies, and Functional Materials

“…The new generation of materials, which involves such areas as nanostructures, 13 self-assembly, 18 molecular machines, 48 and biosystems, 25 attests to the vitality of this field.…”

Efficient production of [ n ]rotaxanes by using template-directed clipping reactions

“…These molecular compounds are usually synthesized by a template-directed approach (22) that depends on molecular recognition and self-assembly processes. Recently, their potential applications as molecular switches for nanoelectronics (23, 24) and molecular actuators for constructing artificial muscles (25), for fabricating smart surface materials (26), and for controlling the nanoscale release of molecules trapped in mesoporous silica (27)(28)(29) were demonstrated. Polyrotaxanes and well defined, homogeneous oligorotaxanes, in which the recognition sites on a dumbbell (an axle terminated by bulky stoppers) are encircled by large rings or macrocycles (wheels) by dint of molecular recognition, have become (30-36) one of the most intensively investigated subjects in mechanical chemistry.…”

Enzyme-Responsive Intracellular Controlled Release Using Nanometric Silica Mesoporous Supports Capped with “Saccharides”

“…[8][9][10] Silica mesoporous supports provide unique features such as stability, biocompatibility, large load capacity, and the possibility to include gate-like scaffoldings on the external surface for the design of nanodevices for on-command delivery applications. [11][12][13][14][15][16] Most of the gated stimuli-responsive systems are based on bio-channels and bio-gates that utilize movable mechanisms triggered by specific stimuli. SMPS-based systems with control release properties have been reported.…”