Controlled distortion of planar porphyrin by intramolecular N-alkylation

[Display omitted] •Alkylation using silver tetrafluoroborate afforded two types of intramolecularly cross-linked N-alkylporphyrins.•The porphyrin with a tetraethylene glycol chain afforded two types of distorted compound by the N-alkylated substitution.•The angle between the N-alkyl pyrrole rings and the mean plane consisting of four meso carbon atoms was controlled.•The differences in the chemical shifts of the N-alkyl compounds are explained by the ring current effect of the porphyrin. The distortion of aromatic macrocycle is of significant interest for understanding of the π-conjugated system. Herein, porphyrin rings with different distortions were synthesized due to intramolecular N-alkylation by introducing a tetraethylene glycol chain. After binding of the cross-linking group of tetraethylene glycol chain to the porphyrin phenyl group, intramolecular cyclization using silver tetrafluoroborate afforded two types of intramolecularly cross-linked N-substituted porphyrins that were alkylated at the N21, (22) or N23, (24) positions. We found that intramolecularly cross-linked N-substituted porphyrins in which the pyrrole nitrogen was connected by a tetraethylene glycol chain afforded different distortions of the porphyrin ring depending on the N-alkylated substitution position.