Selective Photocatalytic Hydroxylation of Inert Hydrocarbons Such as Methane Using Air as the Oxidant

碳氢化合物的低温转化为更活跃的中间体，如醇，对催化来说是一个巨大的挑战。相比之下，自然界已经证明，这种类型的反应可以在环境条件下使用基于活性中心中的铁或铜离子的甲烷单加氧酶等酶来进行。到目前为止，以低分子量铁或铜配合物作为这些酶的模型化合物的选择性氧化研究主要是以热过程进行的。相反，在我们的合作项目中，我们现在希望包括光化学关键步骤，原因如下：a)激发态分子比相应的基态物种具有更强的氧化剂(以及还原剂)。因此，例如，在环境条件下不会氧化特定碳氢化合物的过氧金属络合物，很可能能够在辐射时进行这种反应。B)有可能以光化学方式产生新的氧络合物，作为活性物种，否则很难通过正常的化学反应获得。C)光吸收可以影响和控制金属氧碎片和相关活性中间体的电子分布和自旋特性。因此，我们计划研究一些反应，比如金属臭氧化合物在光激活下形成单核金属氧络合物，释放出氧气。这类络合物被认为是极强的氧化剂，可用于选择性原位氧化。此外，众所周知，几种过氧基配合物是光敏的。同样，将进行调查，以找出这种过氧化氢是否可以通过光诱导过程直接转化为金属氧络合物。甲烷和其他碳氢化合物会在单色和多色光的照射下与不同的氧络合物反应，如双核过氧铜、双氧加合物或金属氧杂化合物。

The low-temperature conversion of hydrocarbons into more reactive intermediates, e.g. alcohols, is a great challenge for catalysis. In contrast nature has already proved that reactions of this type can be performed under ambient conditions using enzymes such as methane monooxygenases that are based on iron or copper ions in the active site. Studies on selective oxidations, using low molecular weight iron or copper complexes as model compounds for these enzymes thus far mainly have been performed as thermal processes. In contrast, in our collaborative project, we now want to incorporate photochemical key-steps for the following reasons: a) Excited state molecules are much more powerful oxidants (as well as reductants) than the corresponding ground state species. Thus, a peroxo metal complex for example, that will not oxidize a certain hydrocarbon under ambient conditions, might well be able to perform this reaction upon irradiation. b) It could be possible to photochemically generate new oxygen complexes as reactive species that are otherwise very difficult to obtain through a normal chemical reaction. c) The electron distribution and spin characteristics of metal-oxo fragments and related reactive intermediates may be influenced and controlled by light absorption. Therefore, we plan to study reactions such as the reaction of metal ozonides to form a mononuclear metal-oxo complex releasing dioxygen if activated by light. Such complexes are regarded as extremely powerful oxidants and could be used for selective oxidations in situ. Furthermore, it is well known that several peroxo complexes are light sensitive. Again, investigations will be performed to find out, if such a peroxide can be directly transformed into a metal oxo complex by photoinduced processes. Methane and other hydrocarbons will be reacted with different oxygen complexes , e.g. dinuclear copper peroxo species, dioxygen adducts or metal oxo compounds under exposure to mono- and polychromatic light.