Deprotonation of nonaromatic octakis-(pentafluorophenyl)-substituted [36]octaphyrin(1.1.1.1.1.1.1.1) with tetrabutylammonium fluoride (TBAF) afforded monoanionic twisted Möbius aromatic species and dianinonic square Hückel antiaromatic species, depending upon the amount of TBAF.
[52]Dodecaphyrin(1.1.0.1.1.0.1.1.0.1.1.0) was quantitatively oxidized with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to the corresponding [50]dodecaphyrin. Further oxidation of [50]dodecaphyrin with MnO2 quantitatively afforded [48]dodecaphyrin. Of the three, [50]dodecaphyrin showed Hückel aromatic character as the largest aromatic molecule reported to date. Protonation of [50]dodecaphyrin with methanesulfonic acid (MSA) led to the formation of a planar tetraprotonated species that displayed a sharp and intense Soret-like band at 906 nm with ε=6.5×10(5) M(-1) cm(-1) and Q-band-like bands at 1346 and 1600 nm.
A rectangular [28]hexaphyrin bearing outer straps at the long side has been synthesized by SN Ar reaction of [26]hexaphyrin with allyl alcohol, intramolecular olefin metathesis by using Hoveyda-Grubbs second-generation catalyst, and reduction with NaBH4 . The peripheral straps enforce a rectangular conformation for the [28]hexaphyrin, which shows Hückel antiaromatic character, as confirmed by its planar X-ray structure, a strong paratropic ring current, characteristic UV/Vis/NIR absorption features, small electrochemical HOMO-LUMO gap, and very fast S1 decay.
Molecular topology of p-conjugated circuits becomes increasingly important in the chemistry of aromatic and antiaromatic compounds.m eso-Pentafluorophenyl-substituted 5,35-(1,4-phenylene)bridged [56]dodecaphyrin was synthesized by condensation of 1,4-phenylene-bridged dicarbinol dimer and 5,10,15-tris-(pentafluorophenyl)tetrapyrrane followed by oxidation with DDQ and was oxidized to its [54]and [52]congeners in as tepwise manner.M etalation of the [52]dodecaphyrin with Pd 2 (dba) 3 gave two bis-Pd II complexes that are isomers of metalation sites:anti and syn with regardto the 1,4-phenylene bridge.T he anti-isomer was easily oxidized to its N-fused form, aq uadruply twisted non-aromatic or weakly aromatic macrocycle.O nt he other hand, the synisomer was revealed to be the first example of Hückel aromatic molecule with aquadruply twisted structure.
A coiled structure of meso-pentafluorophenyl-substituted [62]tetradecaphyrin 1 was revealed by X-ray structural analysis. Synthetic protocols were devised to form mono- and bis-Zn(II) complexes, 1 Zn and 1 Zn2 , selectively. The former displayed a trigonal-bipyramidal pentacoordinated Zn(II) ion as a rare case and a cyclic voltammogram exhibiting eleven reversible redox waves. The latter showed a Ci-symmetric structure with modest Hückel aromaticity owing to a 62 π-electronic circuit as the largest aromatic molecule to date.
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