The Zinc(II) Complexes of Four Constitutional Isomers of the Octaethyl‐ <i>β</i> , <i>β</i> ′‐dioxo‐bacterio‐ and ‐Isobacteriochlorin Series

Treatment of β ‐octaethylporphyrin with H 2 O 2 /conc. H 2 SO 4 to convert it to, inter alia, into all five constitutional isomers of the corresponding β , β ′‐dioxo‐derivatives—two bacteriochlorin‐type isomers and three isobacteriochlorin‐type isomers—is well‐known, as is the ability of some of the dioxo‐derivatives to form transition metal complexes. However, no comparative description of their zinc complexes has become known.This gap is closed here, and a description of the optical (UV–vis absorption and fluorescence emission) properties of their zinc(II) complexes is provided as the basis for their further study and utilization. The strong β ‐oxo auxochromes determine their optical properties that are distinctly different from archetype metallo‐bacteriochlorin or ‐isobacteriochlorin spectra. Herein, a description of the crystal X‐ray structures of three diketone isomer zinc complexes, including a detailed analysis of their macrocycle conformations, is presented. A new pictorial representation of the in‐ and out‐of‐plane distortions observed in the macrocycles of these complexes is taken advantage of to highlight their subtle but important differences.