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Experimental Observation of Thermally Excited Triplet States of Heavier Group 15 Element Centered Diradical Dianions
Author(s) -
Fang Yong,
Zhang Li,
Cheng Cheng,
Zhao Yue,
Abe Manabu,
Tan Gengwen,
Wang Xinping
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.201706060
Subject(s) - diradical , electron paramagnetic resonance , chemistry , singlet state , excited state , crystallography , radical , spectroscopy , photochemistry , main group element , atomic physics , nuclear magnetic resonance , catalysis , transition metal , organic chemistry , physics , quantum mechanics
One‐electron reductions of Mes*As=Fl* ( 1 ; Fl*=2,7‐di‐ tert ‐butylfluorenylidene, Mes*=2,4,6‐ t Bu 3 C 6 H 2 ) and diarsaalkenes [1,2‐ b ]‐IF(=AsMes*) 2 ( 2 ; IF=indenofluorene) with potassium led to the isolation of the arsenic‐centered radical anion salts 1K and 2K , respectively. The diradical dianion salts 2K 2 and 3K 2 were afforded by the reduction of 2 and 2,8‐ t Bu 2 ‐[2,1‐ b ]‐IF(=AsMes*) 2 ( 3 ) with an excess amount of KC 8 . The radicals have been investigated by single‐crystal X‐ray crystallography, EPR, and UV/Vis absorption spectroscopy, along with theoretical calculations. The calculations revealed that 2K 2 and 3K 2 feature open‐shell singlet ground states with singlet‐triplet energy gaps of 2.1 and 1.0 kcal mol −1 , respectively. They are readily thermally excited to triplet states as demonstrated by EPR spectroscopy. The obtained diradicals represent the first examples of heavier Group 15 element centered diradicals with experimentally observable triplet states.