Rotor azimuthal

Figure 17.1 Azimuthal (a) and altitudinal (b) surface-mounted molecular rotors.33 (Reprinted with permission from V. Balzani et al., ChemPhysChem 2008, 9, 202-220. Copyright Wiley-VCH Verlag GmbH Co. KGaA.)...

Light-driven unidirectional molecular rotary motors based on photoisomerization around a C=C bond51 have been successfully immobilized on nanoparticle gold surfaces by two thiol-functionalized legs to yield an azimuthal rotary motor (compound 1 in Fig. 17.2).52 Repetitive and unidirectional 360-degree rotary motion of the rotor moiety with respect to the surface-immobilized stator part was observed to occur on... 

Nonpolar and dipolar altitudinal rotors (compounds 2 and 3 in Fig. 17.3) have been synthesized. 19F NMR spectroscopy showed that the barrier to rotation in 3 was extremely low in solution. Both systems have then been immobilized on Au(l 11) surfaces and studied with a variety of techniques.57 The results obtained indicated that for a fraction of molecules the static electric field from the scanning tunneling microscopy (STM) tip could induce an orientation change in the dipolar rotor but not in the nonpolar analog (for a recent example of an azimuthal molecular rotor controlled by the STM tip, see Reference 58). Compound 3 can exist as three pairs of helical enantiomers because of the propeller-like conformation of the tetra-arylcyclobutadienes. For at least one out of the three diastereomers, an asymmetric potential energy surface can be predicted by molecular dynamics simulations on application of an alternating electric field.55... 

If an incoherent mixture of j n-states is populated Ap(Ya 9a) adequately weighted i Yj jxi(Ya 9a)i should be sfressed that the quantization axis with respect to the preparation process is not necessarily parallel to v. In case v and this axis include the angje B a simple rotation of the coordinate system by the angle B has to be carried out and the squares of the resulting coherent superpositions of rotor eigenfunctions have to be used to calculate Ap(Ya %). The desired distribution Ap(Ya) is then obtained by an integration of Ap(Yat%) over the azimuthal angle 9a ... 

The vector fluid velocity v in the centrifuges of Figs. 2a and 2b consists of radial, azimuthal, and axial components w, v, and w. As will be shown in Section III, the radial component is zero, the azimuthal component is approximately equal to the solid body rotational speed rQ, and the axial component is a function of radial position alone. Axial fluid motion is generated inside the spinning rotor by two means. 

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