Porphyrins basket-handle

Iron porphyrins (containing TPP, picket fence porphyrin, or a basket handle porphyrin) catalyzed the electrochemical reduction of CO2 to CO at the Fe(I)/Fe(0) wave in DMF, although the catalyst was destroyed after a few cycles. Addition of a Lewis acid, for example Mg , dramatically improved the rate, the production of CO, and the stability of the catalyst. The mechanism was proposed to proceed by reaction of the reduced iron porphyrin Fe(Por)] with COi to form a carbene-type intermediate [Fe(Por)=C(0 )2, in which the presence of the Lewis acid facilitates C—O bond breaking. " The addition of a Bronsted acid (CF3CH2OH, n-PrOH or 2-pyrrolidone) also results in improved catalyst efficiency and lifetime, with turnover numbers up to. 750 per hour observed. ... 

In order to compare chiral recognition of the substrate p-chlorostyrene in the presence of chiral picket fences and basket handles carrying the same amino acids the porphyrins 167-169 were prepared in a straightforward manner from the known a,j8,a,j -tetra(o-aminophenyl)porphyrin 170, Fig. 28 [113]. Reaction with t-butoxycarbonyl-L-phenylalanine, removal of the protecting group and subsequent condensation with terephthaloyl chloride e.g. furnished the free base of 169. Iron was always introduced using Fe(CO)5/I2 and the... 

Recently, a new type of C-P-Q triad was reported in which the carotenoid and quinone moieties were linked to the tetraarylporphyrin via basket handle linkages between opposite aryl groups [65]. This linkage positioned the carotenoid and quinone species above and below the plane of the porphyrin, rather than to the side, as confirmed by H-NMR studies. Evidence for photoinitiated electron transfer in this molecule was provided by incorporating it into a phospholipid bilayer and detecting a light-induced photocurrent. Similar experiments had previously been reported with the other C-P-Q triads discussed above [55],... 

One approach has been to construct what are termed picket-fence or basket handle porphyrins, whereby the way the oxygen molecule can approach and leave the iron atom axially is sterically restricted by bulky groups. 

Characteristic differences in skeletal mode wavenumbers in IR spectra were seen for high- and low-spin forms of [Fe(pybzim)3](C104)3.H20, where pybzim = 2-(2 -pyridyl)benzimidazole.287 The resonance Raman spectra of cross-trans-linked iron(II) basket-handle porphyrins gave vsFe-Him2 200 209 cm, vsFe py2 182-205 cm-1 (assignments were helped by deuteriation experiments).288... 

The bis(base) (where base = tV-methylimidazole, 1,5-dicyclohexylimidazole, pyridine) complexes of FeII(TpivPP), where TpivPP = tetrakis(o-pivalamidophe-nyl)porphyrin, give characteristic porphyrinate ligand bands.218 Resonance Raman spectra were used to obtain excitation profiles for two a2g ligand modes for a range of iron(II) porphyrins.219 Ligand modes in the resonance Raman spectra of trarax-cross-linked basket-handle iron(II) porphyrins were used to characterise the ruffled, six-coordinated low-spin iron(II) porphyrin complexes.220... 

Steric encumbrance on both faces of the porphyrin ring must prevent the bimolecular oxidation pathway but often still allows ligand binding. This approach has been proposed by several groups there are the two-pocket porphyrins of Amundsen and Vaska [67], Cense and Le Quan [68] and Suslick and Fox [69] the double-sided porphyrins of Tsuchida and coworkers [70, 71] the basket-handle porphyrins of Momenteau et al. [72-75], Rose and coworkers [76], Walker and coworkers [77], Mansuy et al. [78] and Reddy and Chandrashekar [79] and the jellyfish porphyrins of Uemori and coworkers [80, 81],... 

A similar basket-handle porphyrin in which the bridges are linked to the macrocycle by means of amide groups has also been reported by Momenteau et al. (Scheme 8) [75]. The possibility of isolating the atropisomer of mesotetra(o-aminophenyl)porphyrin in pure form and acylating it with a diacid chloride at room temperature (conditions that do not cause significant isomerization of the atropisomers) allows us to obtain the desired cross-Zraui-linked porphyrin (22) in 32% yield after chromatography. 

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