engleski

A molecular syringe

The control of motion on the molecular scale is of fundamental importance for living organisms, but the construction of synthetic molecular machines able to operate autonomously and perform a specific task remains one of the most intriguing challenges in supramolecular chemistry and nanoscience.[1, 2] Mechanically interlocked architectures, in which the molecular components are held together by noncovalent interactions, provide a convenient platform for design of such molecular machines, especially those containing two or more different recognition sites. In such systems, the fine interplay of variations in relative stabilities of recognition sites and energy barriers for movements within the system due to external stimulus can lead to directed translational motion.[3] Based on these considerations, we have designed a rotaxane system that utilizes light as the external energy source (Figure 1). The axle comprises two ammonium stations for the crown ether and two photoswitchable azobenzene moieties whose photoisomerization triggers the desired molecular motion. The behaviour of the system was investigated in detail by recording the 1H NMR spectra in situ, while irradiating the system, which provided direct insight into changes on the molecular level occurring upon irradiation. It was shown that the system behaves as a molecular syringe: in the absence of light, the axle uptakes the ring molecules, but once the light is shined on the system, the ring molecules are pushed out of the axle.

molekulski strojevi ; svjetlost ; usmjereno gibanje ; samoudruživanje

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