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Metalation Control of Open‐Shell Character in meso‐meso Linked Porphyrin meso ‐Oxy Radical Dimers
Author(s) -
Juni Yuta,
Fukui Norihito,
Furukawa Ko,
Osuka Atsuhiro
Publication year - 2018
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.201705769
Subject(s) - diradical , porphyrin , dimer , chemistry , crystallography , metalation , molecule , photochemistry , imidazole , proton nmr , magnetic circular dichroism , singlet state , stereochemistry , spectral line , atomic physics , physics , organic chemistry , astronomy , excited state
Control of open‐shell character of meso‐meso linked porphyrin meso ‐oxy radical dimers has been demonstrated by core metalation. Namely, Ni II ‐porphyrin dimer 6Ni exhibits a clear 1 H NMR spectrum and a distorted but rather coplanar quinonoidal structure consisting of two ruffled porphyrin rings, in accordance with the previous report. Freebase dimer 6H 2 shows a similar quinonoidal structure in the solid state but displays slightly broader and temperature‐dependent 1 H NMR spectra, indicating a partial diradical character in solution that increases at high temperature. In sharp contrast, bis‐imidazole‐coordinated Zn II ‐porphyrin dimer 6ZnIm 2 exhibits a perpendicular structure consisting of two planar Zn II ‐porphyrins and has been characterized as a distinct open‐shell diradical on the basis of its non‐observable 1 H NMR signals, a clear ESR signal, and a characteristic absorption spectrum reaching about 1700 nm. Despite the distinct diradical character, 6ZnIm 2 is an extremely stable molecule.