Dipyrromethene complexes

The spectra of 69a and 69b exhibited only small nonequivalence in the presence of Yb(hfc)3, whereas addition of Ag(fod) caused larger nonequivalence of methyl and methoxy resonances of the R-groups at 500 MHz . The binuclear dipyrromethene complex with Zn(n) (70) has a helical structure that renders it chiral. This was confirmed by a doubling of certain resonances in the H NMR spectrum of the zinc complex in the presence of Eu(tfc)3/Ag(fod) or Yb(tfc)3/Ag(fod). Splitting of the resonances was not observed in the presence of the lanthanide chelate alone and was only observed on addition of the silver reagent . 

Numerous planar complexes are known. With a few exceptions such as the salicylaldiminato and dipyrromethene complexes mentioned above, neutral four-coordinate complexes containing chelating ligands have planar... 

Dipyrromethenes (dipyrrins) can be deprotonated to form 7t-conjugated biden-tate monoanionic ligands (dipyrrinates) that readily form bis- and tris(dipyrrinato) metal complexes with a variety of transition metal ions. An excellent recent review of these ligands was recently published (79). The overall symmetry of meso-substituted dipyrrins is quite similar to that of the previously discussed acac ligands that were used to create MOFs. Indeed, dipyrrin ligands with donor atoms in the meso position were used in the construction of 1,2, and 3D strucmres. 

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. ... 

A second area of optoelectronic materials are the BODIPY (boron-dipyrromethene) fluorescent dyes. These materials are prepared by condensation of pyrroles with aldehydes, followed by complexation of boron. Attempts to prepare the mesityl-substituted pyrroles via the hindered mesitylketoximine 67 were unsuccessful due to difficulty in generating 67 under standard conditions (NH2OH HCI, heat). However, reaction of the mesityl Grignard reagent with proprionitrile followed by reaction with NH2OH HCI provided ketoximine 67, which was successfully converted to the corresponding pyrrole in 23% yield. The cesium salt of ketoximine 67 was also converted to the same pyrrole in 41%. ... 

An epoch-making discovery in heterofulvene chemistry was the metallic conductivity in the charge-transfer complex formed from tetrathiafulvalene (TTF) 24 and tetracyanoquinodimethane (TCNQ) 25 in 1973 [12]. Upon this discovery, various functional dyes have been designed and constructed on the basis of electronic character of TTF however, this chapter only describes the functional dyes involving a fulvene moiety, because TTF chemistry is considerably larger (see Chapter 8) and many good books and reviews have already been published to date [13]. For the same reason, this chapter does not refer to the chemistry of porphyrins 26 and boron dipyrromethenes (BODIPY) 27, although they formally possess azafulvene moieties in their n-systems [14, 15]. 

The reaction comprises the following steps reduction of 2-trifluoroacetylpyrroles, condensation of the alcohols formed with pyrroles to dipyrromethanes (Scheme 2.187, Table 2.18), their oxidation to dipyrromethenes, and complex formation of the latter with boron trifluoride. The last two stages proceed in a one-pot manner. 

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