title: C,C- and N,C-coupled dimers of 2-aminotetraphenylporphyrins: regiocontrolled synthesis, spectroscopic properties, and quantum-chemical calculations.
abstract: β,β'-Bisporphyrins are intrinsically chiral porphyrin dimers with fascinating properties. The configurational stability at their axes can be directed by variation of the central metal atoms. Herein, we present a regioselective functionalization of the monomeric 2-amino-tetraphenyl-porphyrin as a versatile substrate for dimerization by oxidative coupling. By simple variation of the reaction conditions (solvent and oxidant), the oxidation selectively gave either the axially chiral C,C-coupled diaminobisporphyrin in high yields or, under Ullmann conditions, the twofold N,C-linked achiral dimer, also in good yields. A generalized mechanism for the coupling reaction is proposed based on DFT calculations. The axially chiral β,β'-coupled porphyrin dimers were isolated as racemic mixtures, but can be resolved by HPLC on a chiral phase. TDDFT and coupled-cluster calculations were used to explain the spectroscopic properties of the aminoporphyrins and their dimers and to elucidate the absolute configurations of the C,C-coupled bisporphyrins.
authors.affiliation: Institute of Organic Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg (Germany), Fax: (+49) 931-31-84755.
authors.forename: Torsten
authors.initials: T
authors.lastname: Bruhn
authors.forename: Franziska
authors.initials: F
authors.lastname: Witterauf
authors.forename: Daniel C G
authors.initials: DC
authors.lastname: Götz
authors.forename: Carina T
authors.initials: CT
authors.lastname: Grimmer
authors.forename: Max
authors.initials: M
authors.lastname: Würtemberger
authors.forename: Udo
authors.initials: U
authors.lastname: Radius
authors.forename: Gerhard
authors.initials: G
authors.lastname: Bringmann
keywords: atropisomerism; configuration determination; oxidative coupling; porphyrins; quantum-chemical calculations