The analogous incorporation of a pyridine moiety yielded a class of pyriporphyrins.
The organometallic derivatives of m-benziporphyrins and pyriporphyrins are reminiscent of the large family of pincer ligand complexes, in which the metal–arene
bond is supported by two amine or phosphine arms. This chapter relates the
chemistry of the pincer ligand and that of the m-benziporphyrin (aza-mbenziporphyrin) emphasizing the fact that both groups have been structurally and
functionally based on common dominators, i.e., on m-phenylene (aza-m-phenylene)
rings.
Keywords Carbaporphyrin · Contraction · Metalloporphyrins · Pincer ligand ·
Porphyrin
1 The Convolution of Pincer Ligands
and m-Benziporphyrins: Outlook
The multiple biochemical roles played by iron protoporphyrin IX have inspired
many diverse studies of fundamental scientific significance, triggering a search for
suitable porphyrins and metalloporphyrins prearranged to act as biomimetic models.
The activation of dioxygen, oxygen atom transfer, and the direct functionalization of
C–H bonds via metal-catalyzed atom/group transfer reactions are ground-breaking,
attractive areas of exploration. All of them require porphyrin or metalloporphyrin
participation.
In general, advances in metalloporphyrin chemistry are evidently convoluted with
developments in porphyrin synthetic methods. In light of these, it is quite clear why
chemists in sophisticated explorations in principle mostly apply meso-arylsubstituted porphyrin 1 and its complexes 1-M as their fundamental macrocycle.
Evidently, these molecules preserve the essential features of natural porphyrins.
Fortunately, they can be easily synthesized in impressive varieties and readily
manipulated by virtue of the appropriate external substitution, which in addition
provides the required steric protection, taking on the shape of a porphyrinic cauldron
to enable, for example, control over catalytic stereoselectivity.
Along the road, a unique class of core-modified porphyrins emerged, founded on
the replacement of a single pyrrole ring in the parent meso-aryl-substituted porphyrin
1 by a carbocycle or heterocarbocyle [1–11], including meso-tetraaryl-2-aza-21carbaporphyrin (N-confused porphyrin) 2 [12, 13] and meso-tetraaryl
21-carbaporphyrin 3 (Scheme 1) [14]. The well-defined subclass of
carbaporphyrinoids has been exemplified here by meso-tetraaryl-m-benziporphyrin
5 and alternatively by its appropriate complexes 5-M, which are the fundamental
structures for this review [2, 5]. The isomeric meso-tetraaryl-p-benziporphyrin 4 will
be only briefly addressed particularly in relation to contraction processes [4, 15–
20]. The related 3-aza and 22-aza derivatives, i.e., meso-tetraaryl-22-aza-m182
K. Hurej and L. Latos-Grażyński
The organometallic derivatives of m-benziporphyrins and pyriporphyrins are reminiscent of the large family of pincer ligand complexes, in which the metal–arene
bond is supported by two amine or phosphine arms. This chapter relates the
chemistry of the pincer ligand and that of the m-benziporphyrin (aza-mbenziporphyrin) emphasizing the fact that both groups have been structurally and
functionally based on common dominators, i.e., on m-phenylene (aza-m-phenylene)
rings.
Keywords Carbaporphyrin · Contraction · Metalloporphyrins · Pincer ligand ·
Porphyrin
1 The Convolution of Pincer Ligands
and m-Benziporphyrins: Outlook
The multiple biochemical roles played by iron protoporphyrin IX have inspired
many diverse studies of fundamental scientific significance, triggering a search for
suitable porphyrins and metalloporphyrins prearranged to act as biomimetic models.
The activation of dioxygen, oxygen atom transfer, and the direct functionalization of
C–H bonds via metal-catalyzed atom/group transfer reactions are ground-breaking,
attractive areas of exploration. All of them require porphyrin or metalloporphyrin
participation.
In general, advances in metalloporphyrin chemistry are evidently convoluted with
developments in porphyrin synthetic methods. In light of these, it is quite clear why
chemists in sophisticated explorations in principle mostly apply meso-arylsubstituted porphyrin 1 and its complexes 1-M as their fundamental macrocycle.
Evidently, these molecules preserve the essential features of natural porphyrins.
Fortunately, they can be easily synthesized in impressive varieties and readily
manipulated by virtue of the appropriate external substitution, which in addition
provides the required steric protection, taking on the shape of a porphyrinic cauldron
to enable, for example, control over catalytic stereoselectivity.
Along the road, a unique class of core-modified porphyrins emerged, founded on
the replacement of a single pyrrole ring in the parent meso-aryl-substituted porphyrin
1 by a carbocycle or heterocarbocyle [1–11], including meso-tetraaryl-2-aza-21carbaporphyrin (N-confused porphyrin) 2 [12, 13] and meso-tetraaryl
21-carbaporphyrin 3 (Scheme 1) [14]. The well-defined subclass of
carbaporphyrinoids has been exemplified here by meso-tetraaryl-m-benziporphyrin
5 and alternatively by its appropriate complexes 5-M, which are the fundamental
structures for this review [2, 5]. The isomeric meso-tetraaryl-p-benziporphyrin 4 will
be only briefly addressed particularly in relation to contraction processes [4, 15–
20]. The related 3-aza and 22-aza derivatives, i.e., meso-tetraaryl-22-aza-m182
K. Hurej and L. Latos-Grażyński