Indenofluorene congeners: Biradicaloids and beyond

Akihiro Shimizu, Shunpei Nobusue, Hirokazu Miyoshi, Yoshito Tobe*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


Singlet biradicaloids are certainly one of the most frequently discussed topics at ISNA-15. In this review our own work on the synthesis, molecular structures, and physical properties relevant to biradical character of indenofluorene isomers are described. These include indeno[2,1-a]fluorene with an o-quinodimethane substructure, benz[c]indeno[2,1-a]fluorene which is the first 2,3-naphthoquinodimethane derivative isolated, and indeno[2,1-b]fluorene with an m-quinodimethane (m-xylylene) subunit. The observed physical properties are explained in terms of the theoretically derived biradical factors (y), HOMO-LUMO energy gaps, and singlettriplet energy gaps in the ground state electronic configurations. In addition, we discuss here two perspectives in the biradicaloid chemistry, (i) two-and three-dimensional indenofluorene congeners arranged in a macrocyclic form and (ii) macrocyclic indenofluorenes having multiple radical characters.

Original languageEnglish
Pages (from-to)517-528
Number of pages12
JournalPure and Applied Chemistry
Issue number4
StatePublished - 17 Apr 2014


  • Aromatic compounds
  • ISNA-15
  • Indenofluorenes
  • Quinodimethanes
  • Singlet biradicals


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