An Element-Substituted Cyclobutadiene Exhibiting High-Energy Blue Phosphorescence

Yoshiaki Shoji, Yasuhiro Ikabata, Ivan Ryzhii, Rabia Ayub, Ouissam El Bakouri, Taiga Sato, Qi Wang, Tomoaki Miura, Buddhika S.B. Karunathilaka, Youichi Tsuchiya, Chihaya Adachi, Henrik Ottosson, Hiromi Nakai, Tadaaki Ikoma, Takanori Fukushima*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


1,3,2,4-Diazadiboretidine, an isoelectronic heteroanalogue of cyclobutadiene, is an interesting chemical species in terms of comparison with the carbon system, whereas its properties have never been investigated experimentally. According to Baird's rule, Hückel antiaromatic cyclobutadiene acquires aromaticity in the lowest triplet state. Here we report experimental and theoretical studies on the ground- and excited-state antiaromaticity/aromaticity as well as the photophysical properties of an isolable 1,3,2,4-diazadiboretidine derivative. The crystal structure of the diazadiboretidine derivative revealed that the B2N2 ring adopts a planar rhombic geometry in the ground state. Yet, theoretical calculations showed that the B2N2 ring turns to a square geometry with a nonaromatic character in the lowest triplet state. Notably, the diazadiboretidine derivative has the lowest singlet and triplet states lying at close energy levels and displays blue phosphorescence.

Original languageEnglish
Pages (from-to)21817-21823
Number of pages7
JournalAngewandte Chemie - International Edition
Issue number40
Publication statusPublished - 2021 Sept 27


  • DFT calculations
  • aromaticity
  • luminescence
  • main-group elements
  • reaction mechanisms

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)


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