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Planar Antiaromatic Core‐Modified 24π Hexaphyrin(1.0.1.0.1.0) and 32π Octaphyrin(1.0.1.0.1.0.1.0) Bearing Alternate Hybrid Diheterole Units
Author(s) -
Ajay Jayaprakash,
Shirisha Sriram,
Ishida Masatoshi,
Ito Kosuke,
Mori Shigeki,
Furuta Hiroyuki,
Gokulnath Sabapathi
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201805861
Subject(s) - antiaromaticity , pyrrole , chemistry , porphyrin , crystallography , ring (chemistry) , furan , thiophene , aromaticity , computational chemistry , stereochemistry , photochemistry , molecule , organic chemistry
The Lewis acid catalyzed self‐condensation of hybrid diheterole (furan‐pyrrole and thiophene‐pyrrole) precursors has afforded novel Hückel antiaromatic 24π hexaphyrin(1.0.1.0.1.0) and 32π octaphyrin(1.0.1.0.1.0.1.0) structures without β‐annulated bridges. Single‐crystal X‐ray diffraction analysis of the hybrid porphyrinoids ( S 3 N 3 ‐ox and O 4 N 4 ‐ox ) revealed a nearly planar conformation and the 1 H NMR spectra suggest the presence of paratropic ring currents. These antiaromatic macrocycles show characteristic optical features and underwent reversible two‐electron reduction to Hückel aromatic 26π‐ and 34π‐electron species, respectively, as is evident from the results of spectroscopic and theoretical studies (nucleus‐independent chemical shift (NICS) and anisotropy of the current‐induced density (ACID) calculations). The incorporation of hybrid diheteroles alternately into expanded porphyrin skeletons provides a novel approach to the fine‐tuning of the electronic structures of planar antiaromatic macrocycles.