Premium
Figure‐eight Octaphyrin Bis‐Ge(IV) Complexes: Synthesis, Structures, Aromaticity, and Chiroptical Properties
Author(s) -
Izawa Mondo,
Suito Taisuke,
Ishida Shinichiro,
Shimizu Daiki,
Tanaka Takayuki,
Mori Tadashi,
Osuka Atsuhiro
Publication year - 2020
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.202000159
Subject(s) - aromaticity , antiaromaticity , porphyrin , circular dichroism , enantiomer , chemistry , chirality (physics) , germanium , crystallography , stereochemistry , molecule , chiral symmetry , photochemistry , organic chemistry , silicon , physics , nambu–jona lasinio model , quantum mechanics , quark
Highly twisted structures of expanded porphyrin provide a prominent basis to unravel the relationship between aromaticity and chirality. Here we report the synthesis of bis‐Ge(IV) complexes of [38]octaphyrin that display rigid figure‐eight structures. Two bis‐Ge(IV) [38]octaphyrin isomers with respect to the stereochemistry of the axial hydroxy groups on the germanium ions were obtained and found to be aromatic. Upon oxidation with MnO 2 , these [38]octaphyrin complexes were converted to a single syn ‐type isomer of [36]octaphyrin with retained figure‐eight conformation. The enantiomers have been successfully separated by HPLC equipped with a chiral stationary phase. While aromatic [38]octaphyrin Ge(IV) complexes showed quite large molar circular dichroism of up to Δϵ =1500 M −1 cm −1 with a dissymmetry factor g abs of 0.035, weakly antiaromatic [36]octaphyrin Ge(IV) complexes underscored moderate values; Δϵ =540 M −1 cm −1 with g abs of 0.023. Thus, the figure‐eight octaphyrin scaffold has been proved to be an attractive platform for novel chiroptical materials with tunable aromaticity.