A dozen years of N-confusion: From synthesis to supramolecular chemistry

Abstract

The chemistry of N-confused porphyrin (NCP) and its analogs started in 1994. Since then, considerable progress has been made in understanding the unique properties of NCP and its analogs, which confer characteristic reactivity and metal complex formation. The evolved isomers, multiply NCPs, and expanded N-confused derivatives, have opened up new realms of NCP chemistry. Cis- and trans-doubly N-confused porphyrin (N2CP) stabilizes higher oxidation states such as CuIII in square-planar fashion in the core. Confused isomers with five or more pyrrole rings can coordinate several cations owing to their larger cavities compared to tetrapyrrolic system. The peripheral nitrogen(s) of NCP and its analogs can serve as hydrogen-bonding donor and acceptor, and metal coordination site as well. For example, NCP forms versatile dimers with the assistance of metal ions. The square-planar divalent metal complexes of C6F5-substituted NCP act as efficient anion-binding receptors. Furthermore, CuIII complexes of N2CP, possessing both N and NH at the periphery, form self-assembled one-dimensional (1D) hydrogen-bonding networks, whose orientations differ in cis (zigzag) and trans (straight) isomers.