Salerno Elvin V, Miller Nicholas A, Konar Arkaprabha, Li Yan, Kieninger Christoph, Kräutler Bernhard, Sension Roseanne J
Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, United States.
Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States.
J Phys Chem B. 2020 Jul 30;124(30):6651-6656. doi: 10.1021/acs.jpcb.0c04886. Epub 2020 Jul 21.
Cobalamins are cobalt-centered cyclic tetrapyrrole ring-based molecules that provide cofactors for exceptional biological processes and possess unique and synthetically tunable photochemistry. Typical cobalamins are characterized by a visible absorption spectrum consisting of peaks labeled α, β, and sh. The physical basis of these peaks as having electronic origin or as a vibronic progression is ambiguous despite much investigation. Here, for the first time, cobalamin fluorescence is identified in several derivatives. The fluorescence lifetime is ca. 100-200 fs with quantum yields on the order of 10-10 because of rapid population of "dark" excited states. The results are compared with the fluorescent analogue with zinc replacing the cobalt in the corrin ring. Analysis of the breadth of the emission spectrum provides evidence that a vibrational progression in a single excited electronic state makes the dominant contribution to the visible absorption band.
钴胺素是以钴为中心的基于环状四吡咯环的分子，它们为特殊的生物过程提供辅因子，并具有独特且可通过合成调节的光化学性质。典型的钴胺素的特征在于其可见吸收光谱由标记为α、β和sh的峰组成。尽管进行了大量研究，但这些峰的物理基础是源于电子还是振动跃迁仍不明确。在此，首次在几种衍生物中鉴定出钴胺素荧光。由于“暗”激发态的快速填充，荧光寿命约为100 - 200飞秒，量子产率约为10^-10。将结果与在卟啉环中用锌取代钴的荧光类似物进行了比较。对发射光谱宽度的分析提供了证据，表明单一激发电子态中的振动跃迁对可见吸收带起主要作用。
