It was found for the first time that aromatic diacetylenes give strong ESR signals of stable carbon radical species in solution or in the solid state upon irradiation of UV light. The numbers of radicals reached to the order of 1020 radicals per mole of diacetylene, and the solution became red colored due to the formation of oligomers by their recombination. The radical species were stable almost indefinitely under an inert atmosphere. The unusual stability of these radicals is attributed to a resonance effect of aromatic rings linked to the butadiyne. Very slow quenching in the dark seems to be due to the recombination between them. Theoretical calculations indicated that monomeric diradicals on 1- and 4-carbons with the sp configuration, are formed, which combine to form dimeric or higher species detected by ESR spectroscopy.
首次发现芳香二炔在紫外光照射下,在溶液或固态中生成稳定的碳自由基物种,产生强烈的电子自旋共振(ESR)信号。自由基的数量达到了每摩尔二炔约10^20个,自溶液由于其
重组形成聚合物而变成红色。在惰性气氛下,这些自由基几乎无限稳定。这些自由基的不寻常稳定性归因于与
丁二炔相连的芳香环的共振效应。在黑暗中非常缓慢的湮灭似乎是由于它们之间的
重组。理论计算表明,在1-和4-碳上的单体双自由基以sp构型形成,这些自由基结合形成通过ESR光谱检测到的二聚体或更高物种。