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A Dicyanomethylene‐Substituted Triangulene: Effects of Molecular‐Symmetry Reduction and Electron‐Accepting Substituents on a Fused Polycyclic Neutral π‐Radical System
Author(s) -
Ueda Akira,
Wasa Hideki,
Nishida Shinsuke,
Kanzaki Yuki,
Sato Kazunobu,
Takui Takeji,
Morita Yasushi
Publication year - 2013
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.201300471
Subject(s) - chemistry , delocalized electron , conjugated system , homo/lumo , molecular symmetry , molecular orbital , photochemistry , symmetry (geometry) , degenerate energy levels , redox , electrochemistry , electron , crystallography , molecule , polymer , organic chemistry , physics , electrode , geometry , mathematics , quantum mechanics
Abstract A triangulene‐based C 2 ‐symmetric 33 π‐conjugated stable neutral π‐radical, 2 . , which possesses two dicyanomethylene groups and one oxo group, has been designed, synthesized, and isolated as an analogue of tris(dicyanomethylene) derivative 1 . and trioxo derivative TOT . with C 3 symmetry. Effects of molecular‐symmetry reduction and electron‐accepting substituents on this fused polycyclic neutral π‐radical system were studied in terms of their molecular structure, electronic‐spin structure, and electrochemical and optical properties with the help of theoretical calculations. Interestingly, this system ( 2 . ) has a four‐stage redox ability, like TOT . , as well as low frontier energy levels and a small SOMO–LUMO gap, similar to 1 . , in spite of the loss of the degenerate LUMOs in symmetry‐lowered 2 . , which is associated with the attachment of the weaker electron‐accepting oxo group instead of the dicyanomethylene group in 1 . . These prominent results are attributable to the structural and electronic properties in the triangulene‐based highly delocalized fused polycyclic neutral π‐radical system.