O ‐confusion approach in construction of carbaporphyrinoids

Carbaporphyrinoids provide a suitable macrocyclic platform for organometallic investigations providing unique capabilities for reversible modifications of a macrocyclic structure. Alteration of a coordination core is the route of choice for stabilizing unusual metal ion oxidation states and coordination geometries. This concise review presents the general characteristic of carbaporphyrinoid focusing, however, on oxaporphyrin derivatives. Incorporation of a furan ring into a porphyrin frame results in the formation of 21‐oxaporphyrin or its O ‐confused counterpart. This particular couple, constructed applying the O ‐confusion concept, was selected to illustrate the developments in the field of carbaporphyrinoids. The coordination chemistry in the O ‐confused porphyrin surrounding takes advantage of the unique set of four meridional donor atoms ( C NNN) constrained in the regular porphyrin‐like framework. The subtle interplay between their structural flexibility, perimeter substitution, coordination, and aromaticity was detected for oxacarbaporphyrinoids. The oxidation state of a central metal ion is a factor, which determines the ligand molecular structure. The adjacency of the metal and carbon atom provides the unprecedented route for activation of the carbocyclic moiety, which is built into a metalloporphyrin‐like structure. The perspectives of the field have also been briefly discussed including feasible applications as a new class of building blocks applied to control both the architecture and electronic properties of oligoporphyrinic nanostructures. © 2006 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 6: 64–78; 2006: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20072