Metal assisted cyclodimerization of doubly N-confused dipyrrins into planar aza-heptalenes

Abstract

Metal salts cyclodimerize doubly N-confused dipyrrin into a nornorrole type macrocycle, with a bipyrrolic unit at its center. It also represents an unusual aza-heptalene structure with fused bicyclic seven membered rings. The fused rings can have one or two C–N bonds between the dipyrrin units in the cyclodimer. The ¹H NMR spectrum of these molecules displays aromatic character, rather than antiaromatic behaviour expected of nornorrole, and planar conformation in the solid state.