Anthraquinone 1,5-dimethoxy

C-NMR. The structures of the leuco derivatives of l,4-bis(butylamino)-anthraquinone (14) and l-butylamino-4-hydroxyanthraquinone (15) have been shown to be l,4-bis(butylamino)-2,3-dihydroanthracene-9,10-dione (16a) and l-butylamino-10-hydroxy-2,3-dihydroanthracene-4,9-dione (17a), respectively. On the other hand, leuco-1,4-dimethoxyanthraquinone has been assigned the structure, 1,4-dimethoxy-9,10-dihydroxyanthracene (18). 

V in both methanol and acetonitrile. These values, combined with the doping density and the band gap of 1.12 eV for p-Si places the conduction band edge in methanol and acetonitrile at -0.85V (vs SCE). The supraband edqe redox couples chosen for the two electrolytes were 1,3 dimethoxy-4-nitrobenzene (8,=-l -0V vs SCE)for methanol, and 1 nitronaphthalene (E0=-l. 08), 1, 2 dichloro 4-nitrobenzene (E0= -0.95), and anthraquinone (Eo=-0.95) for acetonitrile. These redox couples lie from 0.IV to 0.24V above the conduction band edge of p-Si, and hence, in the conventional model, could not be photoreduced by p-Si. 

Figure 3. Photoreduction on p-Si or redox couples with redox potentials lying above the conduction band edge as determined by dark flat-band potential measurements. (a) Photoreduction of 1,3 dimethoxy-4-nitrobenzene in methanol (E0 = —1.0V vs. SCE) (b) photoreduction of anthraquinone in acetonitrile (E0 = —0.95 V vs. SCE) Ec for p-Si in both cases in the dark is —0.85 V vs. SCE (------------------------------) dark (---) light (5).

Treatment of 1,2-. 1,4-, 1,5-, and 1,8-dimethoxyanthra-quinone with BF, etherate in Cf,H (reflux) result.s in difluoroboron chelates, which are hydrolyzed to the corresponding l-hydroxy-2-methoxy-, -4-methoxy-, -5-methoxy-, and -8-methoxyanthraquinones when heated in CH,OH. This selective dealkylation can be used to convert 1,4,5-trimethoxyanthraquinone (1) into either 4-hydroxy-1,5-dimethoxy-anthraquinone (4) or l,4-dihydroxy-5-methoxyanthraquinone (5). 

Continuous irradiation at 400 nm of a solution of [Ru(bipy)3p and PhCHjS in dry oxygen-free MeCN has been observed to give a quantitative yield of [Ru(bipy)3]. In the presence of BU4NQO4, this same system can act as a two-compartment cell if coupled with the reduction of a weak electron-acceptor such as 9,10-anthraquinone, 1,3-dinitrobenzene, or 2,6-dimethoxy-p-benzoquinone. The temperature dependence of the reductive quenching of electronically excited [RuLj] (where L = bipy or 4,7-dimethyl-l,10-phenanthroline) by aromatic amines in MeOH has been studied and fitted by theoretical expressions. Activation parameters for a series of quenching reac-... 

Rubiaceaous plants are usually rich in anthraquinones. The first four anthraquinones, 2-methyl-3-methoxyanthraquinone (7), 2-methyl-3-hydroxyanthraquinone (8), 2-methyl-3-hydroxy-4-methoxyanthraquinone (9) and 2,3-dimethoxy-6-methylanthra-quinone (10) reported in genus Hedyotis were isolated from H. diffusa [26]. All the compounds except for (10) are substituted only in ring C. The structure of (10) has been later confirmed by synthesis based on Diels-Alder reaction. This anthraquinone has been the only one reported from a natural source until today. Other anthraquinones possessing the same substitution pattern are synthetic products [27]. 

Stimulated by these results, a prototypical single-molecule field-effect transistor with nanometer-sized gates was realized. Adsorption of dimethoxy-anthracene (an electron donor) on anthraquinone (an electron acceptor), which is covalently linked to HBC 23, induces an interface dipole which shifts the substrate work function by approximately 120 meV, as revealed by STS experiments (Fig. 41) [161]. 

Despite the drawbacks often encountered in photosubstitution reactions, the synthesis of l-methoxy-4-methylamino-9,10-anthraquinone was successfully carried out starting from the corresponding dimethoxy analogue in more than 90% yield [178],... 

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