Bis(10-oxacorrole) with Fused Pyridine as a Linker: Synthesis, Structure, and Interaction between the Subunits in the Neutral, Mono-, and Dicationic States.

Pyridine-fused bis(oxacorrole)s are obtained by a Hantzsch-type cyclization using arylaldehydes and 3-amino-10-oxacorrole. Spectroscopic characteristics, corroborated by density functional theory (DFT) calculations, indicate aromaticity of the dimer and strong interaction between the subunits. Electrochemical and spectroelectrochemical analyses indicate facile access to cation radicals and dicationic species. The oxidized forms are characterized by electronic and electron spin resonance (ESR) spectroscopies as well as by DFT calculations. Monocations give rise to strong absorption bands in the near infra-red (NIR) region between 1500 and 2500 nm, while dications are characterized by a series of absorptions between 1000 and 2200 nm. ESR and variable temperature (VT) nuclear magnetic resonance (NMR) experiments indicate the presence of singlet-triplet spin equilibria for the solution of the dication. For the dication of bis(oxacorrole) in the singlet ground state, neither aromaticity nor antiaromaticity has been detected by low-temperature H NMR and gauge independent atomic orbital (GIAO) calculations despite delocalization of π-electrons.