A Thermally Populated, Perpendicularly Twisted Alkene Triplet Diradical

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• 作者：Prof. Dr. Curt Wentrup ; Dr. Michè ; le J. Regimbald-Krnel ; Dr. Dennis Mü ; ller and Prof. Dr. Peter Comba
• 刊名：Angewandte Chemie International Edition
• 出版年：2016
• 出版时间：November 14, 2016
• 年：2016
• 卷：55
• 期：47
• 页码：14600-14605
• 全文大小：1115K
• ISSN：1521-3773

文摘

Variable-temperature NMR and ESR spectroscopic studies reveal that bis(dibenzo[a,i]fluorenylidene) 1 possesses a singlet ground state, 1(S₀), while the 90° twisted triplet 1(T₁) is populated to a small extent already at room temperature. Analysis of the increasing amount of paramagnetic 1(T₁) at temperatures between 300 and 500 K yields the exchange interaction J_ex/h c=3351 cm⁻¹ and a singlet–triplet energy splitting of 9.6 kcal mol⁻¹, which is in excellent agreement with calculations (9.3 kcal mol⁻¹ at the UKS BP86/B3LYP/revPBE level of theory). In contrast, the zero-field splitting parameter D is very small (calculated value −0.018 cm⁻¹) and unmeasurable.