The properties of 1-hydroxy-4,5-arene-fused tropyliums were assessed based on experimental and theoretical investigations. An X-ray crystallographic analysis revealed a decrease of bond alternation in the seven-membered ring of 1-hydroxy-4,5-benzotropylium derivatives compared with that of the parent 4,5-benzotropones, which is indicative of an increase in aromaticity upon protonation. NICS and AICD calculations also supported the increased aromaticity of 1-hydroxy-4,5-arene-fused tropylium. The pK_a values for a series of 1-hydroxy-4,5-arene-fused tropylium derivatives were also determined.

中文翻译：

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1-Hydroxy-4,5-Arene-Fused Tropylium 衍生物的合成与表征

基于实验和理论研究评估了 1-羟基-4,5-芳烃稠合的 tropyliums 的性质。X 射线晶体学分析显示，与母体 4,5-苯并托酮相比，1-羟基-4,5-苯并托鎓衍生物的七元环中的键交替减少，这表明芳香性增加质子化。NICS 和 AICD 计算也支持 1-羟基-4,5-芳烃稠合的 tropylium 的芳香性增加。还测定了一系列 1-羟基-4,5-芳烃稠合的托鎓衍生物的 p K _a值。