Electron parmagnetic resonance studies on cobalt (II) porphycene and its monomeric oxygen adduct
Electron parmagnetic resonance studies on cobalt (II) porphycene and its monomeric oxygen adduct
复制标题
钴(II)卟啉及其单体氧加合物的电子顺磁共振研究
DOI：
10.1016/s0162-0134(97)80003-7
复制
发表时间：
1997
影响因子：
3.9
通讯作者：
Y. Hisaeda
中科院分区：
文献类型：
--
作者：
H. Shimakoshi;Y. Hisaeda
金属氧配合物由于其在生物体内的重要作用以及人工氧化催化剂而受到化学和生物学的关注。结合分子氧的钴配合物可用于多种配体系统，例如席夫碱、四氮杂大环、酮亚胺和卟啉。卟啉，由Vogel等人合成的卟啉的结构异构体，与卟啉相比，由于其不寻常的性质而引起了相当大的关注。本文用紫外-可见光谱和电子顺磁共振光谱研究了四正丙基卟啉钴配合物1的氧反应活性。1在二氯甲烷中的电子光谱在-70 ° C和-10 ° C下显示出可逆的变化（图1）。这种行为对应于中心金属随其氧化态的变化，Co（II）到Co（III）。在77 K下，1与二氧在二氯甲烷中的EPR谱在g= 2.027处表现出对称信号，并归因于超氧化物。图1中存在四个等吸光度点，再加上EPR数据，清楚地表明了1和1：1氧加合物之间的简单平衡，符号为[Co（III）-O 2]。在吡啶作为轴向配体的存在下，通过EPR证实了六配位超氧物种的形成（gCHARACTER OMITTED= 2.076，gCHARACTER OMITTED= 1.989，ACHARACTER OMITTED= 20 G，ACHARACTER OMITTED= 11 G）。在室温下放置几天后，该化合物被自动氧化成Co（III）络合物，其结构通过X射线分析确定（图2）。在该配合物中，两个吡啶分子在轴向位置配位。钴卟啉对分子氧的反应性以及其氧化能力将通过与钴（II）卟啉的比较进行讨论。
Metal-Dioxygen complexs are of chemical and biological interest because of its importance role in living organisms as well as artificial oxidation catalysts. Cobalt complexes that bind dioxygen are available in a large variety of ligand systems such as schiff base, tetraazamacrocycle, ketoimine and porphyrin. Porphycenes, structural isomer of porphyrins synthesized by Vogel et al., are attracting considerable attention in view of its unusual properties by comparison to those of porphyrins. In this study, we investigated the oxygen reactivitiy of tetra-n-propyl porphycene cobalt (II) complex 1 by means of UV-vis and EPR spectroscopies. Electronic spectra of 1 in dichloromethane under dioxygen atmospher exhibites a reversible change at-70 o C and-10 o C (Figure 1). This behavior was correspond to the change of central metal with its oxidation state, Co (II) to Co (III). The EPR spectrum of 1 with dioxygen in dichloromethane at 77 K exhibits a symmetrical signal at g= 2.027, and was ascribed to superoxide. The presence of four isobestic points in Figure 1, coupled with the EPR data, clearly demonstrates a simple equilibrium between 1 and the 1: 1 oxygen adduct, symbolyzed [Co (III)-O 2]. In the presence of pyridine as axial ligands, formation of six-cooridinate superoxide species was confirmed by EPR (gCHARACTER OMITTED= 2.076, gCHARACTER OMITTED= 1.989, ACHARACTER OMITTED= 20 G, ACHARACTER OMITTED= 11 G). On standing for a few days at room temperature, the compound was autoxidized to a Co (III) complex, which was structurally determined by X-ray analysis (Figure 2). In this complex, two pyridine molecules are cooridinated at axial positions. The reactivity of cobalt porphycene toward dioxygen as well as its oxygenation ability will be discussed by comparison to those of cobalt (II) porphyrin.