Abstract

Data on the spectroscopy of photoexcitation of trans-to-cis isomerization and fragmentation of protonated trans-azobenzene (ABH⁺) in an inert gas atmosphere are analyzed. Results from gas-phase isomerization are compared to ones from a liquid-phase reaction in aqueous sulfuric acid that results in the formation of cyclic benzo[c]cinnoline. There is no cyclization upon gas-phase trans-to-cis isomerization in a rarefied nitrogen medium at T = 300 K, due to the high rate of inverse cis-to-trans isomerization. It is shown that transformations in both phases proceed with the participation of phenylaminyl type cations trans- and cis-ABH⁺, which are chromogens. Photofragmentation of trans-ABH⁺ in an atmosphere of cryogenically cooled helium (T = 40 K) proceeds with the formation of fragment phenyl and phenyl diazonium cations and the participation of phenyl amine cations. Mechanisms of photofragmentation are proposed, including intermediate acts with the participation of H atoms formed by dissociation of the NH group. A fast attack of H atoms along the phenyl ring bonded to the NH group results in the breaking of the C–N bond, eliminating the possibility of trans-to-cis isomerization in a cryogenic helium atmosphere.

中文翻译：

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质子化偶氮苯液相和气相光转化中的苯胺基阳离子

摘要

上的光激发的光谱数据的反式-到-顺式异构化和质子化的碎片反-azobenzene（ABH ⁺在惰性气体气氛中）进行了分析。将气相异构化的结果与在硫酸水溶液中进行液相反应的结果进行了比较，结果是形成了环苯并[c]肉桂酸。对于所气相环化无反式-到-顺式在一个稀薄的氮气介质异构化Ť = 300 K，由于逆率高顺式-到-反式异构化。结果表明，在这两个阶段的变换着手phenylaminyl类型阳离子的参与反式-和顺-ABH ⁺，其是发色团。在低温冷却的氦气（T = 40 K）气氛中，反式-ABH ^+的光碎化过程会导致形成苯基和苯基重氮鎓阳离子碎片，以及苯基胺阳离子参与。提出了光致碎裂的机理，包括由NH基团解离形成的H原子参与的中间作用。H原子沿着与NH基团键合的苯环的快速进攻导致C–N键的断裂，从而消除了反式的可能性至-顺式异构化在低温氦气氛。