PAHs, electron-poor

Films prepared by co-deposition of a polycyclic aromatic hydrocarbon (PAH) and an electron-poor PAH (EPPAH) (Fig. 27) exhibit an oblique arrangement reflecting the formation of epitaxial composite layers of the electron donors and acceptors [81]. Interestingly, on top of a layer of donor molecules, within the same layer between two physisorbed donor molecules, acceptor molecules are co-adsorbed in a well-defined arrangement. When the acceptor co-crystallizes, the second PAH layer is stabilized (Fig. 27). These studies were extended to covalently linked electron donor-acceptor systems [82,83]. 

The two molecules forming such a Ti-complex consist of a donor molecule with a low ionization potential so that an electron can be readily lost (a delocalized TT-electron of the PAH) and an acceptor molecule with a high affinity for electrons (the aromatic ring of trinitrobenzene which is electron-poor because the three nitro groups pull electrons out of it). As a result, stacks of alternating donor and acceptor molecules are found in the crystal. The relative orientations within the parallel planes of these donor and acceptor molecules are determined, to a considerable extent, by the orientations of charge distributions of the... 

Robins and Cass also employed a range of electron-rich and electron-poor benzylamines to react with 6-fluoropurine thionucleoside in high yield [95]. Sterically congested aminotriols of relevance to the study of poly aromatic hydrocarbons (PAHs) have also been incorporated in modest to excellent yields (50-93 %, dependent on the bulk of the amine) [105, 115]. Similarly, aminoesters [116] and amino alcohols [117] have been incorporated via a SnAt reaction with 6-(fluoro)-2 -deoxyadenosine analogs in modest yield. Glutathione (70) has also been shown to... 

Whereas GC methods for PAHs are commonly based on mass spectrometric detection with electron ionization, MS detection is less common for LC methods for PAHs. Poor ionization efficiencies reportedly result from the application of traditional MS sources (e.g., particle beam El and ESI) due to the relatively high ionization energies (lEs) for PAHs... 

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