Cyclophanes structures

When Illb is heated with p-phenylenediamine at 200-300°C under conditions similar to the other phenylenediamines, mainly insoluble, probably crosslinked, oligomers (rubber-like solid) are formed. On the other hand, p-phenylenediamine with bis(diethylamino)dimethylsilane at 180°C yielded a toluene-soluble solid whose molecular weight and elemental analysis agree well with the probable cyclophane structure IX for C32H48NsSi4 Mcaic. 657.16, found Mcryoscopic 648, m/e 657.16 calc. % C, 58.49 H, 7.36 N, 17.05 Si, 17.10 found % C, 58.40 H, 7.42 N, 17.10 Si, 17.16. The structure of this compound is being further investigated. 

Cyclic thiourea derivatives having three different types of cyclophane structure (ortho-meta, meta-meta and meta-para) and a lariat-type thiourea have been synthesized, using reaction of isothiocyanate with amine.230 Cyclic thioureas have been obtained from formaldehyde aminals and sulfur (Sg) (Scheme 77).231... 

Strong additional support for the assignment of the metapara-cyclophane structure 129 was obtained from dynamic NMR studies The temperature dependence of the proton resonance of this compound is analogous to that of the parent [2.2]metaparacyclophane 3>. The multiplets observed for the protons of the p-phenyl nucleus gradually broaden with increasing temperature, disappear completely at 150 °C, and reappear at 180 °C as a midway peak. The isomer of 129, the 13-methoxy[2]paracyclo[2](l,4)naphthalenophane (132), formation of which by the mechanism outlined above seems equally feasible, does not appear to occur. 

As seen, cyclophane structures shown in Schemes 1.4b through 1.4e have the following unique feature The through-bond distance within the paracyclophane fragment is held constant, whereas the spatial distance between the ion-radicalized and neutral moieties is changed. Therefore, the relative importance of through-bond and through-space mechanisms for intramolecular electron transfer can be learned directly from experimental data on these molecules. 

Wurster in 1879 had already prepared crystalline salts containing radical cation 23 (equation 12). Subsequently, radical cations of many different structural types have been found, especially by E. Weitz and S. Hunig, and recently these include a cyclophane structure 24 containing two radical cations (Figure 3). Leonor Michaelis made extensive studies of oxidations in biological systems, " and reported in 1931 the formation of the radical cation species 25, which he designated as a semiquinone. Michaelis also studied the oxidation of quinones, and demonstrated the formation of semiquinone radical anions such as 26 (equation 13). Dimroth established quantitative linear free energy correlations of the effects of oxidants on the rates of formation of these species. ... 

In contrast to cyclodextrins, there is no parent cyclophane structure available in nature. Therefore, the design of the host molecule starts from the... 

Formulae 330-333 represent various interesting cyclophane structures [5]. 

Yip and co-workers recently isolated a trinuclear gold(I) complex with 9,10-bis(diphenylphosphino)anthracene ligand, [Au3(/x-Ph2PAnPPh2)3] (0104)3, with a cyclophane structure and interesting cyclohexane-like flux-ional behavior [22]. The complex also exhibits intense emission with a structureless band maximized at 475 nm in MeCN at 298 K. The absence of any structural features in the emission band and the large Stokes shift of 4000 cm-1 suggested the excimeric nature of the emission. 

Donor-acceptor cyclophanes have been extensively investigated as models for intermolecular charge transfer (CT) complexes. The [m.n]cyclophane structure provides the adjustable well-defined distance and orientation for the donor and acceptor units incorporated in its framework. These systems have been systematically investigated by Staab et al. using absorption spectroscopy [34]. 

Moreover, chromophores 77 and 78 can be considered as twin chromo-phores that are connected through cr-bonds. While 77 represents a triplebond chromophore, 78 incorporates a distyrylbenzene moiety. In particular, the strong alignment of the 7i-chromophores through the cyclophane structure results in an increase of both OP and TP properties. 

Over the years, this particular class of compounds has mushroomed to give an enormous variety of compounds all having the characteristic feature of a cyclophane. Not only do cyclophanes enjoy great popularity in general, but they have also invaded many areas of chemistry. There is almost no chemical branch where cyclophane structures are not met, mostly at a central point whether in a scientific or an application sense. 

Fig. 1 Selected cyclophane structures and their nomenclature according to Vdgtle/Neumann and to lUPAC ...

Connection of two cinnamate chromophores has frequently been used to attain high local concentrations of reactants, thereby circumventing the inefficiency of the above-mentioned bimolecular dimerization reactions. An extreme example of this approach is embodied in the cyclophane structures 3, in which two cinnamate moieties undergo photodimerization to give quantitatively the P-truxinate dimer with a quantum yield of Similarly, the bis-cinnamamide 4 furnished 48% of P-truxinimide upon... 

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