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Cyano disubstituted tetrabenzoindeno[2,1-a]fluorene: open-shell or closed-shell?
Priyank Kumar Sharma1, Palash Jana2, Subhajit Bandyopadhyay2
1Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar 140001, Punjab, India. chmsdas@iitrpr.ac.in.
Abstract:
Organic diradicaloids have lately emerged as potential spintronic materials. We report the unprecedented synthesis of a near-IR absorbing indeno[2,1-a]fluorene derivative that displays remarkably low LUMO (-4.15 eV) and a small HOMO-LUMO gap (0.85 eV). NMR/EPR studies indicated its open-shell diradical property, which was supported by DFT calculations while suggesting a 30% diradical character and a small singlet (S)-triplet (T) gap (-2.52 kcal mol-1). A large bond length alternation of the as-indacene core for its single-crystals indicated a quinoidal contribution with greater antiaromaticity, which is in line with the small diradical character despite showing a small S-T gap.
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