Benzylic amide catenane

Other types of rotary motors can be constructed using catenanes, that is, species minimally composed of two mechanically interlocked macrocycles. In appropriately designed systems, the rotation of one ring around the other can be achieved by external stimulation. If suitable control elements are introduced in the structure, such a rotation can be performed unidirectionally. This concept was cleverly realized with benzylic amide catenanes by exploiting the isomerization of fumaramide to maleamide caused by UV light. Chiral C=N compounds such as imines also fulfill the criteria of two-step light-driven unidirectional molecular... 

Scheme8 Translational isomerism in an amphibilic benzylic amide [2]catenane 16 [55]...

Fig. 12 Examples of the use of color in depictions of various types of MIMs. Note how the colors and positions of constituent parts in the three-dimensional structures reflect those in the structural drawings to enhance clarity between representations of (a) a donor-acceptor [2]catenane [75] and (b) an ammonium-binding [2]rotaxane [76] from our group, (c) a transition metal-templated Solomon Knot from the Sauvage and Fujita groups [77], and (d) a benzylic amide [2]catenane from the Leigh group [78]. Reproduced with permission from [75] (copyright 1991 Royal Society of Chemistry), [76] (copyright 2000 Wiley-VCH), [77] (copyright 1999 Royal Society of Chemistry), [78] (copyright 1995 Wiley-VCH)...

Fig. 27 Examples of thermodynamically controlled reactions employed in the near-quantitative synthesis of MIMs. (a) Disulfide-exchange reaction permits equilibration between a bis(ammo-nium) disulfide dumbbell and a crown ether macrocycle to yield a mixture of [2]- and [3]rotaxanes quantitatively [194], (b) Olefin metathesis at high concentration on a benzylic amide macrocycle greatly favors the catenated species [196]. (c) Self-correcting imine bonds allow for nearly quantitative selection of a [2]rotaxane from an appropriate dynamic combinatorial library [76], (d) A weak nucleophile (E) equilibrates the components of a donor-acceptor [2]catenane in a dynamic Sn2 reaction [205]...

The simplest catenanes and rotaxanes such as benzylic amide [2] catenanes, fumrots and norots were successfully processed into thin films by using 3 techniques ... 

Figure 6. Edge of the absorption. spectrum (in log scale) of benzylic amide [2] catenane as function of solution concentration. The increasing number correspond to decreasing concentration. The spectra 1-5 were recorded in solutions with a concentration of 7.5, 4.0, 1.5, 0.88, and 0.36 g/1 respectively. The dashed line (7) is the spectrum of a solution in methanol with a concentration of about 0.04 g/1. Its optical density of 7 is multiplied by a factor of 10...

Figure 8. Absorption spectra of thin films the benzylic amide [2] catenane obtained by vacuum evapo-ration and by solution cast...

The measured refractive index dispersions for benzylic amide [2] catenane, fumrot and norot are displayed in Figs. 15-17, respectively. In all cases we observe a birefringence due to the order created during the thin film deposition and favored by... 

Figure 15. Refractive index dispersion in a vacuum evaporated thin film of benzylic amide [2] catenane...

The optical propagation losses in the vacuum evaporated benzylic amide [2] catenane thin films, measured in planar waveguide configuration [47, 48] were found to be PL = 2.8 0.1 dB/cm at A = 1.32 (xm and PL = 4.0 0.1 dB/cm at A = 1.55 (xm, respectively. These values were determined by a two prism method [49]. As for polycrystalline thin films these value are significantly smaller han usually observed. It shows the ability of these molecules to form good optical quality thin films by using these technologically friendly technique. It shows also that the crystallites are very small, tens to a few hundreds of nanometers size. 

In conclusion, we have reviewed the linear and nonlinear optical properties of simplest benzylic acide [2] catenanes and benzylic amide [2] rotaxanes. These molecules can be processed into good optical quality thin films with a high refractive index, which can be modified by a subsequent functionalization, as it was shown in the case of rotaxanes. 

R. CaciufFo, A.D. Esposti, M.S. Deleuze, D.A. Leigh, A. Murphy, B. Paci, S.F. Parker F. Zerbetto (1998). J. Chem. Phys., 109, 11094-11100. Inelastic neutron scattering of large molecular systems The case of the original benzylic amide [2]catenane. 

Facile synthesis and solid-state structure of a benzylic amide [2]catenane, A. G. Johnson, D. A. Leigh, R. J. Pritchard and M. D. Deegan, Angew. Chem. Int. Ed. Engl, 1995, 34, 1209. 

Leigh. D.A. Troisi. A. Zesbetto. F. A quantum-mechanical description of macrocyclic ring rotation in benzylic amide [2]catenanes. Chem. Eur. J. 2002. 7. 1450-1454. 

Benzylic amide[2]catenanes were studied on HOPG by air Molecular adsorption is supposed to take place on the surface through the carbonyl groups present in the backbone. The authors comment on the possibility of molecular diffusion during imaging and also on molecular degradation upon adsorption as contributor factors to the very few features observed with submolecular resolution in the STM images. 

Figure 25 (a) Synthesis of mixed benzylic amide esto catenane 93 by template-directed synthesis and (b) magic-ring catenane 95... 

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