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首页> 外文期刊>Chemistry: A European journal >Steady-State and Pseudo-Steady-State Photocrystallographic Studies on Linkage Isomers of [Ni(Et_4dien)(η~2-O,ON)(η~1-NO_2)]: Identification of a New Linkage Isomer
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Steady-State and Pseudo-Steady-State Photocrystallographic Studies on Linkage Isomers of [Ni(Et_4dien)(η~2-O,ON)(η~1-NO_2)]: Identification of a New Linkage Isomer

机译：[Ni（Et_4dien）（η〜2-O，ON）（η〜1-NO_2）]的键合异构体的稳态和伪稳态光晶体学研究：鉴定一个新的键合异构体

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摘要

At temperatures below 150 K, the photoactivated metastable endo-nitrito linkage isomer [Ni(Et_4dien)(η~2- O,ON)(η~1-ONO)] (Et_4dien=N,N,N',N'-tetraethyldiethylenetriamine) can be generated with 100% conversion from the ground state nitro-(η~1-NO_2) isomer on irradiation with 500 nm light, in the single crystal by steady-state photocrystallographic techniques. Kinetic studies show the system is no longer metastable above 150 K, decaying back to the ground state nitro-(η~1-NO_2) arrangement over several hours at 150 K. Variable-temperature kinetic measurements in the range of 150–160 K show that the rate of endo-nitrito decay is highly dependent on temperature, and an activation energy of E_(act)=+48.6(4) kJmol~(-1) is calculated for the decay process. Pseudo-steady-state experiments, where the crystal is continually pumped by the light source for the duration of the X-ray experiment, show the production of a previously unobserved, exo-nitrito-(η~1-ONO) linkage isomer only at temperatures close to the metastable limit (ca. 140–190 K). This exo isomer is considered to be a transient excited-state species, as it is only observed in data collected by pseudosteady- state methods.
机译：在低于150 K的温度下，光活化的亚稳态内腈链键异构体[Ni（Et_4dien）（η〜2- O，ON）（η〜1-ONO）]（Et_4dien = N，N，N'，N'-四乙基二亚乙基三胺可以通过稳态光晶体学技术在单晶中以500 nm的光从基态硝基-（η〜1-NO_2）异构体以100％的转化率生成。动力学研究表明，该系统在150 K以上时不再亚稳态，在150 K下经过数小时后会衰减回基态硝基-（η〜1-NO_2）排列。在150–160 K范围内进行变温动力学测量表明硝化内毒素的衰变速率高度依赖于温度，并为衰变过程计算了E_（act）= + 48.6（4）kJmol〜（-1）的活化能。伪稳态实验，其中晶体在X射线实验过程中被光源连续泵浦，显示出以前未观察到的外硝化-（η〜1-ONO）键联异构体的产生温度接近亚稳极限（约140–190 K）。该exo异构体被认为是瞬态激发态物质，因为它仅在通过伪稳态方法收集的数据中观察到。

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