Dept. of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
Phys Chem Chem Phys. 2021 Feb 28;23(8):4555-4568. doi: 10.1039/d0cp05650b. Epub 2021 Feb 19.
We study the primary photolysis dynamics of aqueous lactate induced by photo-excitation at λ = 200 nm. Our calculations indicate that both decarboxylation and dehydroxylation are energetically possible, but decarboxylation is favoured dynamically. UV pump - IR probe transient absorption spectroscopy shows that the photolysis is dominated by decarboxylation, whereas dehydroxylation is not observed. Analysis of the transient IR spectrum suggests that photo-dissociation of lactate primarily produces CO and CHCHOH through the lowest singlet excited state of lactate, which has a lifetime of τ = 11 ps. UV pump - VIS probe transient absorption spectroscopy of electrons from the dissociating lactate anion indicates that the anionic electron from the CO˙ fragment is transferred to the CHCHOH˙ counter radical during the decarboxylation process, and CO˙ is consequently only observed as a minor photo-product. The photo-dissociation quantum yield after the full decay of the excited state is Φ(100ps) = 38 ± 5%.
我们研究了在 λ = 200nm 光激发下，水合乳酸盐的初级光解动力学。我们的计算表明，脱羧和脱氢都是在能量上可行的，但动态上更有利于脱羧。紫外泵-红外探针瞬态吸收光谱表明，光解主要由脱羧作用主导，而未观察到脱氢作用。瞬态红外光谱分析表明，乳酸盐通过其最低的单线态激发态主要产生 CO 和 CHCHOH，其寿命为 τ = 11 ps。从解离的乳酸盐阴离子产生的电子的紫外泵-可见探针瞬态吸收光谱表明，在脱羧过程中，来自 CO˙ 碎片的阴离子电子被转移到 CHCHOH˙ 自由基上，因此仅观察到 CO˙ 作为次要光产物。激发态完全衰减后的光解量子产率为 Φ(100ps) = 38 ± 5%。
