Direct and Sensitized Photoprocesses of Bis‐benzimidazole Dyes and the Effects of Surfactants and DNA ¶
Direct and Sensitized Photoprocesses of Bis‐benzimidazole Dyes and the Effects of Surfactants and DNA ¶
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双苯并咪唑染料的直接和敏化光处理以及表面活性剂和 DNA 的影响 ¶
DOI：
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发表时间：
2001
影响因子：
3.3
通讯作者：
H. Görner
中科院分区：
文献类型：
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作者：
H. Görner
研究了两种双苯并咪唑染料Hoechst 33258(1)和类似物的光处理过程，其中p位的酚基被乙氧基Hoechst 33342(2)取代。对于水溶液中的1和2，荧光量子产率强烈依赖于pH值；从pH 5时的最大值Φf= 0.4降至pH 8时的Φf= 0.02。十二烷基硫酸钠表面活性剂低于和高于临界胶束浓度以及双链DNA诱导的吸收和荧光效应，通过假设在大量水溶液中染料基本上以单体形式存在来解释。当染料与双链DNA结合或在胶束中溶解时，Φf的强增强被认为是由于苯并咪唑环上不同的环境。在中性pH下，λexc= 248或308 nm，形成了吸收最大为380 nm的醌类中间体。在193 nm和248 nm波长（单光子和双光子）的电子喷射后，用激光光解法观察了水溶液中N中心的1或2自由基。前体自由基阳离子未被观察到，但通过去质子作用转化为上述自由基。电子从水溶液中的1转移到三态丙酮，随后的去质子化被认为会产生N中心自由基。此外，丙酮向1的能量转移导致了T-T吸收，在700 nm处达到最大值。讨论了光分解的过程，并与脉冲辐射分解的结果进行了比较。
The photoprocesses of two bis‐benzimidazole dyes, Hoechst 33258 (1) and an analog, where the phenolic group in p‐position is replaced by an ethoxy group, Hoechst 33342 (2), were studied. For 1 and 2 in aqueous solution the quantum yield of fluorescence is strongly pH dependent; it decreases from a maximum value of Φf= 0.4 at pH 5 to Φf= 0.02 at pH 8. The effects of absorption and fluorescence, induced by sodium dodecyl sulfate surfactants below and above the critical micelle concentration and by double‐stranded DNA, are interpreted by assuming that in bulk aqueous solution the dyes are essentially present as monomers. The strong enhancement of Φf, when the dye is bound to double‐stranded DNA or solubilized in micelles, is suggested to be due to different environments at the benzimidazole rings. A quinoid intermediate with absorption maximum at 380 nm is formed for 1 at neutral pH using λexc= 248 or 308 nm. N‐centered radicals of 1 or 2 in aqueous solution were observed by laser flash photolysis after electron ejection using wavelengths of 193 or 248 nm (mono and biphotonic, respectively). The precursor radical cation escaped observation but is transformed into the above radicals by deprotonation. Electron transfer from 1 in aqueous solution to triplet acetone takes place, and subsequent deprotonation is proposed to yield N‐centered radicals. In addition, energy transfer from acetone to 1 is suggested, leading to T–T absorption with the maximum at 700 nm. The photoprocesses are discussed and the results compared with those known from pulse radiolysis.