Phenothiazine donor

For some reviews, see (a) Majoral J-P (2007) Influence of cationic phosphorus dendrimers on the surfactant-induced synthesis of mesostructured nanoporous silica. New J Chem 31 1259-1263 (b) Puntoriero F, Nastasi F, Cavazzini M et al (2007) Coupling synthetic antenna and electron donor species a tetranuclear mixed-metal Os(II)-Ru(II) dendrimer containing six phenothiazine donor subunits at the periphery. Coord Chem Rev... 

For time-resolved studies, the hole can be injected in a laser flash experiment by a tethered (excited) electron acceptor and a sink (an electron donor) at a given distance (e.g., pyrene/phenothiazine Ru-complexes/methylindole). Many of the... 

It is known from electrochemical studies that fullerenes are easily reduced. Up to 6 electrons can be added reversibly [19], and, as mentioned earlier, the excited states are even more easily reduced. A large number of electron donors were investigated including aromatic and alkyl amines [29,43,79,119-140,152,161], ni-troxide radicals [57,117], suspensions of Ti02 [118], polyaromatic compounds, [19,127] organo-silicon compounds, [133,158] phenothiazine, [133] acridine [145,154], (3-carotene [141], tetrathiafulvalenes [146], tetraethoxyethene [147], phthalocyanines [148], porphyrines [151,153], NADH and analogues [150,154, 155], borates [156,159], and naphtoles [23] to name a few representative cases. 

The Eisenberg group has been investigating the utility of the Pt(NAN) (-C=C-Ar)2 unit as the central chromophore in such systems. Thus the complex 14 was prepared, incorporating phenothiazine (PTZ) donor groups... 

We will review here work wherein several types of species incorporate the Ir-bis-terpy unit and derivatives. The search for multicomponent arrays, including metal-based photoactive centres in combination with electron donor and acceptor components, was started a couple of decades ago, and one of the first systems, compound 14+, was studied by Meyer et al. (Fig. 1) [5]. In this multicomponent system, the electron donor phenothiazine (PTZ) and the bridged 2,2/-bipyridinium (DQ) units are linked to the photoactive unit by flexible methylene connections. In this early example, excitation at the Ru-based chromophore ultimately yields a PTZ+-DQ" CS state which lives 165 ns and for which the transiently stored energy is 1.29 eV. 

In the design of such supramolecular dyads, a number of prerequisites should to be considered. In order to obtain a true supramolecular assembly there needs to be substantial interaction between the different components of the assembly. There should, however, not be any substantial changes in the physical properties of these components, but their combination should lead to some new and novel characteristics. The combination of components should have properties over and above those of the separate components, without destroying their individual characters. Molecular dyads may, for example, contain a photosensitizer and an electron or energy donor or acceptor. An example of such a combination of a sensitizer and an electron donor is the Ru-PTZ dyad [14] shown in Figure 6.21. In this assembly, the ruthenium center is the sensitizer, S, and the phenothiazine... 

It is now well established that a variety of organic molecules such as polynuclear aromatic hydrocarbons with low ionization energies act as electron donors with the formation of radical cations when adsorbed on oxide surfaces. Conversely, electron-acceptor molecules with high electron affinity interact with donor sites on oxide surfaces and are converted to anion radicals. These surface species can either be detected by their electronic spectra (90-93, 308-310) or by ESR. The ESR results have recently been reviewed by Flockhart (311). Radical cation-producing substances have only scarcely been applied as poisons in catalytic reactions. Conclusions on the nature of catalytically active sites have preferentially been drawn by qualitative comparison of the surface spin concentration and the catalytic activity as a function of, for example, the pretreatment temperature of the catalyst. Only phenothiazine has been used as a specific poison for the butene-1 isomerization on alumina [Ghorbel et al. (312)). Tetra-cyaonoethylene, on the contrary, has found wide application as a poison during catalytic reactions for the detection of active sites with basic or electron-donor character. This is probably due to the lack of other suitable acidic probe or poison molecules. 

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