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Experimental Observation of Thermally Excited Triplet States of Heavier Group 15 Element‐Centered Diradical Dianions

One‐electron reductions of Mes*As=Fl* (1; Fl* = 2,7‐di‐tert‐butylfluorenylidene, Mes* = 2,4,6‐tBu3C6H2) 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 2K2 and 3K2 were afforded by the reduction of 2 and 2,8‐tBu2‐[2,1‐b]‐IF(=AsMes*)2 (3) with an excess amount of KC8. 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 2K2 and 3K2 feature open‐shell singlet ground states with singlet‐triplet energy gaps of 2.1 and 1.0 kcal mol‐1, respectively. They are readily to be 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.

Authors:   Yong Fang, Li Zhang, Cheng Cheng, Yue Zhao, Manabu Abe, Gengwen Tan, Xinping Wang
Journal:   Chemistry - A European Journal
Year:   2018
Pages:   n/a
DOI:   10.1002/chem.201706060
Publication date:   19-Jan-2018
Facts, background information, dossiers
  • dianions
  • crystallography
  • absorption spectroscopy
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