Institute of Physical and Theoretical Chemistry, University of Bonn, Germany.
Photochem Photobiol Sci. 2006 Oct;5(10):970-8. doi: 10.1039/b611963h. Epub 2006 Sep 15.
Triplet energies play a considerable role in optical spectroscopy, and can be determined from phosphorescence or the quenching thereof. Their role in spin chemistry may not be as obvious, but the triplet state has always had an important function or utility, namely of reaction intermediates such as radical pairs, their precursors, of carbenes, and of the final products. In situ NMR spectroscopy represents a useful tool to explore certain properties of the triplet state, especially in cases with no phosphorescence. The 'phase' of CIDNP resonances, i.e., emission or enhanced absorption, reflects the spin selectivity of electron transfer reactions. In radical ion pairs the spin selectivity is determined by the relation between the change of the standard free enthalpy DeltaG degrees during the electron back transfer and the triplet energies (E(T)) of the products. If triplet recombination is energetically feasible (DeltaG degrees > E(T)), it is typically the more efficient process in agreement with the Marcus theory.
三重态能量在光学光谱学中起着相当大的作用，可以通过磷光或磷光猝灭来确定。它们在自旋化学中的作用可能不那么明显，但三重态一直具有重要的功能或用途，例如自由基对、它们的前体、卡宾和最终产物等反应中间体。原位 NMR 光谱学是探索三重态某些性质的有用工具，特别是在没有磷光的情况下。CIDNP 共振的“相位”，即发射或增强吸收，反映了电子转移反应的自旋选择性。在自由基离子对中，自旋选择性由电子反向转移过程中标准自由焓ΔG°的变化与产物的三重态能量(E(T))之间的关系决定。如果三重态复合在能量上是可行的（ΔG°>E(T)），根据 Marcus 理论，它通常是更有效的过程。
