Chemistry of High-Energy Content Reagents

我们将研究阳离子染料和阴离子硼酸盐形成的离子对的光化学、光物理和光谱性质。首先要考虑的问题是，由硼酸根的单电子氧化形成的硼基是否为结合物种。这将通过在皮秒和飞秒时间尺度上应用时间分辨光谱方法来解决。由于硼基自由基的寿命太短，不能用电化学方法测量氧化电位，因此将采用基于Rehm-Weller方程的动力学方法来估计它们的电位。将制备一系列的硼酸盐，以研究硼酸盐中的空间位阻对氧化电位的影响。对于光引发的电子转移反应，将制备具有不同相遇距离、取向和自由能变化的穿透离子对。利用这些不同的穿透离子对，将分析控制向前和向后电子转移的因素。来自有机动力学项目的这笔赠款支持伊利诺伊大学加里·B·舒斯特教授的继续工作。离子对将由带正电的染料和带负电的硼酸盐形成。硼酸盐总共含有四个与硼原子键合的其他含碳基(烷基或芳基)。这些离子对将受到被染料吸收的光的照射。一个电子将从染料转移到硼酸盐，进而导致烷基以自由基形式与硼解离(具有一个未配对电子的碳物种)。这种反应的效率将作为离子对结构的函数来研究，该反应的效率在一定程度上取决于电子的反向转移以产生起始离子对。这些离子对具有实际意义，因为它们可以在可见光和红外光照射下引发聚合。聚合物的广泛商业应用使这些离子对具有商业价值。

The photochemical, photophysical, and spectroscopic properties of ion pairs formed from cationic dyes and anionic borates will be studied. The first question to be considered will be whether or not the boranyl radicals formed by one electron oxidation of borates are bound species. This will be addressed by application of time-resolved spectroscopic methods on picosecond and femtosecond time-scales. Since the lifetime of boranyl radicals is too short to permit measurement of the oxidation potential by electrochemical means, a kinetic method based on the Rehm-Weller equation will be applied to estimate their potentials. A series of borates will be prepared to investigate the effect of steric crowding in the borate upon the oxidation potential. Penetrated ion pairs will be prepared that have different encounter distances, orientation, and free energy changes for photoinitiated electron transfer reactions. With these various penetrated ion pairs, factors that control forward and back electron transfer will be analyzed. This grant from the Organic Dynamics Program supports the continuing work of Professor Gary B. Schuster at the University of Illinois. Ion pairs will be formed from positively charged dyes and negatively charged borates. The borates contain a total of four other carbon containing groups ( alkyl or aryl groups) bonded to the boron atom. These ion pairs will be irradiated with light which is absorb by the dye. An electron will be transfer from the dye to the borate, which will in turn cause an alkyl group to dissociate from boron in the form of a free radical (a carbon species with one unpaired electron). The efficiency of this reaction, which depends in part on the back-transfer of an electron to give the starting ion pair, will be studied as a function of the structure of the ion pair. These ion pairs have practical importance, since they can initiate polymerization upon irradiation with visible and infrared light. The wide co mmercial application of polymers makes these ion pairs of commercial interest.