Singh Priti, Das Atanu Kumar, Sarkar Biprajit, Niemeyer Mark, Roncaroli Federico, Olabe José A, Fiedler Jan, Zális Stanislav, Kaim Wolfgang
Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany.
Inorg Chem. 2008 Aug 18;47(16):7106-13. doi: 10.1021/ic702371t. Epub 2008 Jul 23.
Experimental and computational results for different ruthenium nitrosyl porphyrin complexes [(Por)Ru(NO)(X)] ( n+ ) (where Por (2-) = tetraphenylporphyrin dianion (TPP (2 (-) )) or octaethylporphyrin dianion (OEP (2-)) and X = H 2O ( n = 1, 2, 3) or pyridine, 4-cyanopyridine, or 4- N,N-dimethylaminopyridine ( n = 1, 0)) are reported with respect to their electron-transfer behavior. The structure of [(TPP)Ru(NO)(H 2O)]BF 4 is established as an {MNO} species with an almost-linear RuNO arrangement at 178.1(3) degrees . The compound [(Por)Ru(NO)(H 2O)]BF 4 undergoes two reversible one-electron oxidation processes. Spectroelectrochemical measurements (IR, UV-vis-NIR, and EPR) indicate that the first oxidation occurs on the porphyrin ring, as evident from the appearance of diagnostic porphyrin radical-anion vibrational bands (1530 cm (-1) for OEP (-) and 1290 cm (-1) for TPP (-)), from the small shift of approximately 20 cm (-1) for nu NO and from the EPR signal at g iso approximately 2.00. The second oxidation, which was found to be electrochemically reversible for the OEP compound, shows a 55 cm (-1) shift in nu NO, suggesting a partially metal-centered process. The compounds [(Por)Ru(NO)(X)]BF 4, where X = pyridines, undergo a reversible one-electron reduction. The site of the reduction was determined by spectroelectrochemical studies to be NO-centered with a ca. -300 cm (-1) shift in nu NO. The EPR response of the NO () complexes was essentially unaffected by the variation in the substituted pyridines X. DFT calculations support the interpretation of the experimental results because the HOMO of [(TPP)Ru(NO)(X)] (+), where X = H 2O or pyridines, was calculated to be centered at the porphyrin pi system, whereas the LUMO of [(TPP)Ru(NO)(X)] (+) has about 50% pi(NO) character. This confirms that the (first) oxidation of [(Por)Ru(NO)(H 2O)] (+) occurs on the porphyrin ring wheras the reduction of [(Por)Ru(NO)(X)] (+) is largely NO-centered with the metal remaining in the low-spin ruthenium(II) state throughout. The 4% pyridine contribution to the LUMO of [(TPP)Ru(NO)(py)] (+) is correlated with the stability of the reduced form as opposed to that of the aqua complex.
报道了不同的亚硝酰钌卟啉配合物[(Por)Ru(NO)(X)] (n+)（其中Por (2-) = 四苯基卟啉二价阴离子(TPP (2 (-)))或八乙基卟啉二价阴离子(OEP (2-))，X = H₂O (n = 1, 2, 3)或吡啶、4-氰基吡啶或4-N,N-二甲基氨基吡啶(n = 1, 0)）的实验和计算结果，涉及它们的电子转移行为。[(TPP)Ru(NO)(H₂O)]BF₄的结构被确定为{MNO}物种，RuNO排列几乎呈线性，角度为178.1(3)度。化合物[(Por)Ru(NO)(H₂O)]BF₄经历两个可逆的单电子氧化过程。光谱电化学测量（红外、紫外-可见-近红外和电子顺磁共振）表明，第一次氧化发生在卟啉环上，这从诊断性的卟啉自由基阴离子振动带（OEP (-)为1530 cm (-1)，TPP (-)为1290 cm (-1)）的出现、νNO约20 cm (-1)的小位移以及giso约2.00处的电子顺磁共振信号可以明显看出。第二次氧化对于OEP化合物在电化学上是可逆的，显示出νNO有55 cm (-1)的位移，表明是部分以金属为中心的过程。化合物[(Por)Ru(NO)(X)]BF₄，其中X = 吡啶，经历一个可逆的单电子还原。还原位点通过光谱电化学研究确定为以NO为中心，νNO有大约 -300 cm (-1)的位移。NO ()配合物的电子顺磁共振响应基本上不受取代吡啶X变化的影响。密度泛函理论计算支持了对实验结果的解释，因为[(TPP)Ru(NO)(X)] (+)（其中X = H₂O或吡啶）的最高占据分子轨道被计算为以卟啉π体系为中心，而[(TPP)Ru(NO)(X)] (+)的最低未占据分子轨道具有约50%的π(NO)特征。这证实了[(Por)Ru(NO)(H₂O)] (+)的（第一次）氧化发生在卟啉环上，而[(Por)Ru(NO)(X)] (+)的还原在很大程度上以NO为中心，金属在整个过程中保持低自旋钌(II)状态。[(TPP)Ru(NO)(py)] (+)的最低未占据分子轨道中4%的吡啶贡献与水合配合物相比，与还原形式的稳定性相关。
