W BAND EPR SPECTRA OF SEMIQUINONES

半醌自由基的超高频EPR(95 GHz)谱 报道了冰冻溶液。在这个频率下，增加的塞曼 交互作用可以很容易地解决 G-矩阵。自由基与溶剂的相互作用在 了解g矩阵中的结构变化。我们已经使用了 各种溶剂，包括极性和非极性，以生成 从不同的对苯二酚中分离出半对苯二酚，并测量了 G-各向异性。在很大程度上，超精细的分裂仍然存在 未溶解，即使在氢化溶剂中也是如此。G-矩阵的比较 半醌自由基在不同溶剂中的相互作用是非常重要的 氢键已被认为对 G-矩阵的特定成分。因此氢键的作用 在半喹酮反应中，自由基的形成尤为重要 以了解它们在体内系统中的形成。确实有 G-矩阵各分量变化的一致趋势 关于溶剂的性质和结构。这些 根据SCF-MO(从头算和从头算)可以理解趋势 半经验)计算的g张量，这表明 G张量对氢键和离子对的形成都很敏感。 这些计算在以下方面变得更加准确和高效 这一年的拨款。这是一个持续多年的项目。

Very high frequency EPR (95GHz) spectra of semiquinone radicals in frozen solution are reported. At this frequency, the increased Zeeman interaction readily resolves the anisotropic components of the g-matrix. The radical-solvent interactions are important in understanding the structural variations in the g-matrix. We have used a variety of solvents, both polar and nonpolar, to generate semiquinone radicals from various quinones and have measured the g-anisotropy. For the most part, the hyperfine splittings remain unresolved, even in deuterated solvents. Comparison of the g-matrix of semiquinone radicals in different solvents is quite important and hydrogen-bonding has been known to play a remarkable effect on specific components of the g-matrix. Thus the role of hydrogen bonds during the semiquinone radical formation is of particular importance to understand their formation in in vivo systems. There are consistent trends in the variation of the components of the g-matrix with respect to the nature of the solvents and structure. These trends can be understood in the light of SCF-MO (both ab initio and semi-empirical) calculations of the g-tensor, which show that the g-tensor is sensitive to both hydrogen bonding and ion-pair formation. These computations have become much more accurate and efficient during this grant year. This is an ongoing multi-year project.