Coordination and Metalation Bifunctionality of Cu with 5,10,15,20-Tetra(4-pyridyl)porphyrin: Toward a Mixed-Valence Two-Dimensional Coordination Network
Coordination and Metalation Bifunctionality of Cu with 5,10,15,20-Tetra(4-pyridyl)porphyrin: Toward a Mixed-Valence Two-Dimensional Coordination Network
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DOI：
10.1021/ja300593w
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发表时间：
2012-04-11
影响因子：
15
通讯作者：
Lin, Nian
中科院分区：
文献类型：
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作者：
Li, Yang;Xiao, Jie;Lin, Nian
我们通过扫描隧道显微镜、X射线光电子能谱和密度泛函理论计算研究了Cu与5,10,15,20-四(4-吡啶基)卟啉(2HTPyP)在Au(111)表面上的配位自组装和金属化反应。发现 2HTPyP 通过外围吡啶基和卟啉核心与 Cu 相互作用。来自相邻分子的成对吡啶基与 Cu(0) 原子配位，从而形成超分子金属有机配位网络。网络形成发生在室温下； 450 K 退火可增强该工艺。 Cu 与卟啉核心的相互作用更为复杂。在室温下，观察到初始复合物 Cu(0)-2HTPyP 的形成。 450 K 退火会激活分子内氧化还原反应，配位的 Cu(0) 被氧化为 Cu(II)，并形成复合物 Cu(II)TPyP。配位网络由 Cu(0) 原子连接的 Cu(II) 配合物组成；也就是说，它表示由 Cu(II) 和 Cu(0) 中心的有序阵列组成的混合价二维配位网络。超过 520 K 时，网络降解，连接位置的 Cu 原子扩散到基底中，而 Cu(II)TPyP 配合物形成密堆积结构，通过弱分子间相互作用稳定。密度泛函理论研究表明，与 Cu(0) 的反应是通过金属原子和卟啉之间形成初始络合物进行的，然后在反应过程中形成 Cu(II) 卟啉。根据所使用的方法，限速步骤的活化屏障为 24-37 kcal mol(-1)。此外，两个 CuTPyP 分子对 Cu 原子的线性配位：根据气相计算，这是有利的。
We investigated the coordination self-assembly and metalation reaction of Cu with 5,10,15,20-tetra(4-pyridyl)porphyrin (2HTPyP) on a Au(111) surface by means of scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory calculations. 2HTPyP was found to interact with Cu through both the peripheral pyridyl groups and the porphyrin core. Pairs of pyridyl groups from neighboring molecules coordinate Cu(0) atoms, which leads to the formation of a supramolecular metal-organic coordination network. The network formation occurs at room temperature; annealing at 450 K enhances the process. The interaction of Cu with the porphyrin core is more complex. At room temperature, formation of an initial complex Cu(0)-2HTPyP is observed. Annealing at 450 K activates an intramolecular redox reaction, by which the coordinated Cu(0) is oxidized to Cu(II) and the complex Cu(II)TPyP is formed. The coordination network consists then of Cu(II) complexes linked by Cu(0) atoms; that is, it represents a mixed-valence two-dimensional coordination network consisting of an ordered array of Cu(II) and Cu(0) centers. Above 520 K, the network degrades and the Cu atoms in the linking positions diffuse into the substrate, while the Cu(II)TPyP complexes form a close-packed structure that is stabilized by weak intermolecular interactions. Density functional theory investigations show that the reaction with Cu(0) proceeds via formation of an initial complex between metal atom and porphyrin followed by formation of Cu(II) porphyrin within the course of the reaction. The activation barrier of the rate limiting step was found to be 24-37 kcal mol(-1) depending on the method used. In addition, linear coordination of a Cu atom by two CuTPyP molecules it: favorable according to gas-phase calculations.