Tetraphenylporphyrin molecules containing heteroatoms other than nitrogen: 8—A carbon‐13 NMR study

The ¹³C NMR spectra of new hetero‐substituted tetraphenylporphyrin (TPP) molecules have been studied. It was found that most of the carbon chemical shifts are similar to those found in TPP. The similar chemical shifts of the different β‐carbons in S₂TPP and in Se₂TPP free bases and, moreover, the considerable downfield shift of the α‐carbons of the S(Se)‐rings on protonation are in agreement with the previously suggested theory of inner and outer aromaticity in these porphyrins.