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.