Monofluorination, lateral

Lateral monofluorination of the p-alkoxyphenyl isocyanide system [XAu (CNC6H40C H2 +i)] (X = C1, Br, I), in ortho-(3-F) (6a) and meta-(2-F) (6b) positions relative to the alkoxy chain was also studied [18]. None of the free fluorinated ligands is a LC, but their gold complexes display mesomorphic properties. This is a typical case of a promesogenic ligand which yields a mesogen upon coordination to a metal. 

If the molecular dipole moment is oriented perpendicularly to the long molecular axis, a material with negative Ae is obtained [31b]. For steric reasons simple lateral monofluorination of an aromatic moiety within the mesogenic core structure does not result in a perpendicular orientation of the molecular dipole moment. This can be achieved only by pair-wise lateral difluorination, which results in mutual cancellation of the respective longitudinal components of the dipole moment vector leaving only the perpendicular contribution. Examples of the most commonly used dielectrically negative materials based on this concept are listed in Table 4.10. 

In general, the melting points followed the series Clclearing points was not so easily interpreted. Lateral monofluorination of complexes 7, in the ortho (3-F) or meta (2-F) position relatively to the alkoxy chain, has also been investigated... 

KF/DCNB = 3). This difference, concerning the kinetics of monofluorination, will be discussed later. 

In the later work, Coward and coworkers carried out a study of electrophilic fluorination of pyroglutamic acid derivatives. The results provided an alternative route to fluorinated pyroglutamic acids and derived fluoroglutamic acids." " Conditions were found that led to diastereoselective monofluorination to produce 40, but attempts to carry out difluorination of the substrate were unsuccessful. The bicyclic... 

Fluorinated analogues of these and related porphyrins were later used to reconstitute myoglobins that contain fluorinated hemes. These were used for NMR studies of the effects of distortion of the porphyrin 7t-system by the chemical properties of the peripheral side chains. A similar strategy involving the oxidative coupling of similar dipyrromethenes and monofluorodipyrromethenes produced 6-monofluorinated porphyrins. Reconstituted myoglobins and iron complexes prepared from these were studied. ... 

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