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An Element‐Substituted Cyclobutadiene Exhibiting High‐Energy Blue Phosphorescence
Author(s) -
Shoji Yoshiaki,
Ikabata Yasuhiro,
Ryzhii Ivan,
Ayub Rabia,
El Bakouri Ouissam,
Sato Taiga,
Wang Qi,
Miura Tomoaki,
Karunathilaka Buddhika S. B.,
Tsuchiya Youichi,
Adachi Chihaya,
Ottosson Henrik,
Nakai Hiromi,
Ikoma Tadaaki,
Fukushima Takanori
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202106490
Subject(s) - cyclobutadiene , antiaromaticity , phosphorescence , chemistry , aromaticity , singlet state , triplet state , ring (chemistry) , excited state , derivative (finance) , ground state , computational chemistry , photochemistry , crystallography , atomic physics , molecule , fluorescence , physics , organic chemistry , quantum mechanics , financial economics , economics
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 B 2 N 2 ring adopts a planar rhombic geometry in the ground state. Yet, theoretical calculations showed that the B 2 N 2 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.