Irregular porphyrins

Mercury(II) porphyrins seem to be rather irregular, since various types of Hg11 complexes have been reported (Scheme 25).174... 

The porphyrin tweezers method is now well established and has allowed a successful determination of AC of some natural products, such as isotomenoic acid 36, an irregular diterpene,58 and bovidic acid 37, an 18-carbon... 

Regular metalloporphyrin complexes fluoresce, with their fluorescence quantum yield modified by the heavy-atom effect. The complexes tend to be purple in the solid state and wine red in solution. The normal absorption spectra of regular porphyrins is indicative of little or no interaction between atomic orbitals on the metal and ir-molecular orbitals on the porphyrin. Thus, the absorption and emission spectra of regular metalloporphyrins are largely determined by the porphyrin s ir-electrons. This is not the case with irregular metalloporphyrins. They show three main types of spectra called normal, hypso, and hyper. 

The nidcel and nitrogen atoms are coplanar in nickel deoxophylloerythrin methyl ester (13), a model compound for chlorophyll, and the porphyrin nucleus shows only the usual slight ruffling from planarity. The presence of a fifth ring manifests itself principally in irregularities in the Ni-N... 

---