Photosensitized dissociation of di-tert-butyl peroxide. Energy transfer to a repulsive excited state
Photosensitized dissociation of di-tert-butyl peroxide. Energy transfer to a repulsive excited state
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二叔丁基过氧化物的光敏解离。
DOI：
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发表时间：
1981
期刊：
影响因子：
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通讯作者：
G. G. Wubbels
中科院分区：
文献类型：
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作者：
J. Scaiano;G. G. Wubbels
利用纳秒激光闪光光解技术研究了多种芳烃和酮类化合物与过氧化二叔丁基的能量传递。三重态能量转移到过氧化物导致其有效裂解成两个叔丁氧基自由基。对于对甲氧基苯丙酮、二苯甲酮和苯并（a）蒽，在25/sup 0/C下苯中三重态猝灭的代表性速率常数分别为7.9 x 10/sup 6/、3.4 x 10/sup 6/和7.0 x 10/sup 4/M/sup-1/s/sup-1/。对甲氧基苯丙酮（E/sub T/ = 72.5 kcal/mol）的转移速率与温度无关; 0.17三重态能量每降低1千卡需要1千卡/摩尔活化能。没有证据表明激基复合物intermediacyfound.A模型的能量转移到一个排斥态的过氧化物提出了在没有活化能是必需的，如果敏化剂满足能量要求在0-0平衡距离。对于较低的三重态能量的敏化剂，能量转移到一个排斥状态，提出发生从热激活基态具有大于平衡氧-氧键长。相同的机制可以应用于受体缺乏低位激发态的其他系统。还通过使用荧光技术确定了用于猝灭单重态敏化剂的几个速率常数。«少
Energy transfer from a variety of aromatic hydrocarbons and ketones to di-tert-butyl peroxide has been examined by using nanosecond laser flash photolysis techniques. Triplet energy transfer to the peroxide leads to its efficient cleavage into two tert-butoxy radicals. Representative rate constants for triplet quenching in benzene at 25/sup 0/C are 7.9 x 10/sup 6/, 3.4 x 10/sup 6/, and 7.0 x 10/sup 4/M/sup -1/s/sup -1/ for p-methoxypropiophenone, benzophenone, and benz(a)anthracene, respectively. The rate of transfer for p-methoxypropiophenone (E/sub T/ = 72.5 kcal/mol) is approximately temperature independent; for lower energy sensitizers ca. 0.17 kcal/mol activation energy is required for each kilocalorie per mole decrease in triplet energy. No evidence indicating exciplex intermediacy was found. A model for energy transfer to a repulsive state of the peroxide is proposed in which no activation energy is required if the sensitizer meets the energy requirements at the 0-0 equilibrium distance. For sensitizers of lower triplet energy, energy transfer to a repulsive state is proposed to occur from a thermally activated ground state having a greater than equilibrium oxygen-oxygen bond length. The same mechanism may apply in other systems where the acceptor lacks low-lying excited states. A few rate constants for the quenching of singletmore » sensitizers have also been determined by using fluorescence techniques.« less