Porphyrins carboxylate-functionalized

We fabricated the modified ITO electrodes4 by a combination of SAM formation with a terpyridine derivative and stepwise metal-terpyridine coordination reactions in a similar manner as that described in the previous section (Fig. II).11,13 A cleaned ITO was immersed in a 0.1 M solution of 4-[2,2 6, 2"-terpyridin]-4 -yl-benzoic acid (tpy-BzA) in chloroform for 12 h to anchor the carboxyl group to ITO. Subsequently, the modified ITO was immersed in an aqueous solution of 0.1 M CoCl2, Fe(BF4)2 or Zn(BF4)2 for 2—3 h to form metal-terpyridine coordination reactions. Finally, the metal-coordinated ITO was immersed in a 0.1 M acetonitrile solution of a terpyridine-functionalized porphyrin, tpy-ZnTPP, providing the target molecular wires, [M-ZnTPP], on electrodes (Fig. 11). In addition, a cleaned ITO was immersed in a 0.1 M ethanol solution of carboxylate-functionalized porphyrin, C10ZnTPP, to afford a modified ITO as a reference. 

In a recent example, aryl-carboxylic solubilization was used to solubilize core-modified porphyrins. Solubilizing aryl carboxylic functions were also replaced by their tetra-zole or 1,2,4-oxadiazolone bioisosteres in the design of second generation, benzodiazepine-derived, CCK-B antagonists (Figure 38.2). °... 

Fig. 6 Zinc porphyrin 7 functionalized with six carboxylic acid groups...

Similar to the intramolecular insertion into an unactivated C—H bond, the intermolecular version of this reaction meets with greatly improved yields when rhodium carbenes are involved. For the insertion of an alkoxycarbonylcarbene fragment into C—H bonds of acyclic alkanes and cycloalkanes, rhodium(II) perfluorocarb-oxylates 286), rhodium(II) pivalate or some other carboxylates 287,288 and rhodium-(III) porphyrins 287 > proved to be well suited (Tables 19 and 20). In the era of copper catalysts, this reaction type ranked as a quite uncommon process 14), mainly because the yields were low, even in the absence of other functional groups in the substrate which would be more susceptible to carbenoid attack. For example, CuS04(CuCl)-catalyzed decomposition of ethyl diazoacetate in a large excess of cyclohexane was reported to give 24% (15%) of C/H insertion, but 40% (61 %) of the two carbene dimers 289). 

Another interesting work conducted by Wamser and co-workers in the field of porphyrin monomer sensitizers is the functionalization of tetraphenylporphyrin at the para positions of -phenyl with one amino group and three carboxylic acid groups. The resulted asymmetrical porphyrin (45) can be successfully fabricated into a modified solid Gratzel type cell with polyaniline as the solid electrolyte. The overall energy conversion efficiency of this cell is about 2% with a number of opportunities to optimize the efficiency remaining [81]. 

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