H+ TRANSFER AND CH4 FORMATION IN METALLOENZYME MODELS

为了研究金属结合的半胱氨酸作为 生物学中的质子存储和/或转移位置，一系列新的 模拟金属酶的过渡金属硫酸盐络合物 氢酶(Ni)、乙醇脱氢酶(Zn)和氰基水合酶(Fe)， 将通过模板席夫碱反应合成。S……H 将探讨质子化介质和质子化M-(RS)-H+中的相互作用 尽可能隔离的物种。与底物H2的反应(Ni-SR)， 将研究R-OH(锌-SR)和H2O(Fe-SR)，其机理包括 将测试跨M-SR的H-H或C-H键的异质加成。 结构和反应性之间的关系也将在 为了评估与金属酶有关的特性 活动。 -(CH2)n-S-Me底物生成甲烷的机理 类似物将用甲基辅酶M还原酶模型进行检验 含共价镍(I)N4大环的化合物 连接(系)硫代乙醚的手臂。反应性(即C-S键断裂) -依赖于臂长(n=2，3)和R-基团(R=Me，Et，CH2Ph) 将考察一系列系链Ni(N_4-(CH_2)_n-S-R)大环。在……里面 为了检验我们的单电子转移机制的相关性 在Ni...SR2之间的相互作用和反应性将被考察和自由基 将探索使用冷冻淬火EPR的中间体。动力学 C-S键的断裂将通过低T UV/Vis和产物(CH4， CH3-CH3，CH3Ph)将用~1H核磁共振和GC/MS进行检测。

In order to examine the possible role of metal-bound cysteinates as proton storage and/or transfer sites in biology, a series of late transition-metal thiolate complexes which model the metalloenzymes hydrogenase (Ni), alcohol dehydrogenase (Zn), and nitrile hydratase (Fe), will be synthesized using a template schiff-base reaction. S....H interactions will be probed in protic media and protonated M-(RS)-H+ species isolated where possible. Reactions with substrates H2 (Ni-SR), R-OH (Zn-SR), and H2O (Fe-SR) will be examined and mechanisms involving heterolitic addition of H-H or C-H bonds across a M-SR will be tested. The relationship between structure and reactivity will also be probed in order to assess the features which are responsible for metalloenzyme activity. Mechanisms leading to methane formation from -(CH2)n-S-Me substrate analogues will be examined using methyl coenzyme M reductase model compounds which consist of Ni(I)N4 macrocycles containing covalently attached (tethered) thioether arms. Reactivity (i.e., C-S bond cleavage) -dependence on arm-length (n=2, 3) and R-group (R= Me, Et, CH2Ph) for a series of tethered Ni(N4-(CH2)n-S-R) macrocycles will be examined. In order to test our single electron transfer mechanism the correlation between Ni....SR2 interaction and reactivity will be examined and radical intermediates will be probed for using freeze quench EPR. The kinetics of C-S bond cleavage will be monitored by low T UV/vis and products (CH4, CH3-CH3, CH3Ph) will be detected using 1H NMR and GC/MS.