Dimethoxynaphthalene units

In the same way, the displacement of the unpaired electron over the whole molecules was observed for cation-radicals from Scheme 1.4d and 1.4e, in which 1,4-dimethoxynaphthalene units are syn- or anti-annealed to [2.2]paracyclophane (Wartini et al. 1998a, 1998b). In another study, the electron transfer between 1,4-dimethoxybenzene and 7,7-dicyanobenzoquinone methide moieties... 

Figure 2 shows the structures of the bifunctional model systems l(n), (n=4,6,8,10,12), investigatedThe synthesis of these systems and a discussion of their electrochemical properties as well as of their electronic absorption and emission spectra have been given elsewhere (Oevering et al., 1987). These molecules contain a 1, 4-dimethoxynaphthalene unit as the photoexcitable electron donor (E./2 =+1.1 V vs. see in acetonitrile) and a 1,1-dicyano-vinyl moiety as a moderately powerful electron acceptor (Ev=-. l V) separated by an array of at least n C-C sigma-bonds. The centre-to-centre separation (Rc) and the edge-to-... 

The strength of the hydrogen bonds in the protonated amines can be increased by the use of larger and additional groups to provide further steric strain. For example, the difference in strain between l,8-bis(dimethylamino)-naphthalene [33] and 1,8-bis(diethylamino)naphthalene leads to a piC,-value for the ethyl derivative enhanced by 0.5 units (Hibbert, 1974), and a similar difference is also observed in the fluorene series for [41] and [42]. Further strain can be introduced into the naphthalene series by the use of 2- and 7-methoxyl groups as substituents. This is illustrated by the pA -values of 1,8-bis(dimethylamino)naphthalene [piC, = 12.1 (Hibbert, 1974)] and l,8-bis(di-methylamino)-2,7-dimethoxynaphthalene [p, = 16.1 (Hibbert and Simpson, 1987a)] and by the piC,-values of [35] pK = 7.49 (Hibbert and Hunte,... 

Interestingly, the second reduction of the two bipyridinium units splits in the case of catenane 144+ (Fig. 13.15) obtained by interlocking cyclophane 124+ with a symmetric macrocycle containing two electron donor dimethoxynaphthalene (DMN)... 

As already pointed out in the case of rotaxanes, mechanical movements can also be induced in catenanes by chemical, electrochemical, and photochemical stimulation. Catenanes 164+ and 174+ (Fig. 19) are examples of systems in which the conformational motion can be controlled electrochemically [82, 83], They are made of a symmetric electron acceptor, tetracationic cyclophane, and a desymmetrized ring comprising two different electron donor units, namely a tetrathiafulvalene (TTF) and a dimethoxybenzene (DOB) (I64 1) or a dimethoxynaphthalene (DON) (174+) unit. Because the TTF moiety is a better electron donor than the dioxyarene units, as witnessed by the potentials values for their oxidation, the thermodynamically stable conformation of these catenanes is that in which the symmetric cyclophane encircles the TTF unit of the desymmetrized macrocycle (Fig. 19a, state 0). 

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