Effects of Carbon-Metal-Carbon Linkages on the Optical, Photophysical, and Electrochemical Properties of Phosphametallacycle-Linked Coplanar Porphyrin Dimers
Effects of Carbon-Metal-Carbon Linkages on the Optical, Photophysical, and Electrochemical Properties of Phosphametallacycle-Linked Coplanar Porphyrin Dimers
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DOI：
10.1021/ja210205v
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发表时间：
2012-01-25
影响因子：
15
通讯作者：
Imahori, Hiroshi
中科院分区：
文献类型：
--
作者：
Matano, Yoshihiro;Matsumoto, Kazuaki;Imahori, Hiroshi
5-（二苯基膦基）-10，15，20-三芳基卟啉（meso-膦基卟啉）发生络合反应。与钯（II）和铂（II）盐的反应，通过meso-膦基卟啉配体的区域选择性外围β-C-H活化，分别得到磷杂钯杂环-和磷铂杂环-稠合的共面卟啉二聚体。通过稳态紫外-可见吸收/荧光光谱、循环和差分脉冲伏安法、时间分辨光谱（荧光和瞬态吸收寿命和光谱）和磁性圆二色光谱研究了这些金属连接的卟啉二聚体及其卟啉单体/二聚体参比物的光学和电化学性质。所有观察到的数据清楚地表明，钯（II）和铂（II）的链接器在两个卟啉发色团之间的电子通信在单电子氧化态和在激发态的单线态-三线态系统间交叉过程中发挥至关重要的作用。研究还表明，C-Pt-C键对这些基本性质的影响比C-Pd-C键更显著。此外，对金属连接的卟啉二聚体的密度泛函理论计算表明，外围连接的金属和相邻的吡咯β-碳原子之间的反键d pi-p pi轨道相互作用使卟啉π-系统的最高占据分子轨道不稳定，并解释了所观察到的独特吸收性质。这些实验和理论结果的基础上，可以得出结论，线性碳-金属-碳连接弱，但肯定扰动的磷杂环连接的共面卟啉二聚体的光学，物理和电化学性质。
5-(Diphenylphosphanyl)-10,15,20-triarylporphyrins (meso-phosphanylporphyrins) underwent complex. ations with palladium(II) and platinum(II) salts to afford phosphapalladacycle- and phosphaplatinacycle-fused coplanar porphyrin dimers, respectively, via regioselective peripheral beta-C-H activation of the meso-phosphanylporphyrin ligands. The optical and electrochemical properties of these metal-linked porphyrin dimers as well as their porphyrin monomer/dimer references were investigated by means of steady-state UV-vis absorption/fluorescence spectroscopy, cyclic and differential pulse voltammetry, time-resolved spectroscopy (fluorescence and transient absorption lifetimes and spectra), and magnetic circular dichroism spectroscopy. All the observed data clearly show that the palladium(II) and platinum(II) linkers play crucial roles in the electronic communication between two porphyrin chromophores at the one-electron oxidized state and in the singlet-triplet intersystem-crossing process at the excited state. It has also been revealed that the C-Pt-C linkage makes more significant impacts on these fundamental properties than the C-Pd-C linkage. Furthermore, density functional theory calculations on the metal-linked porphyrin dimers have suggested that the antibonding d pi-p pi orbital interaction between the peripherally attached metal and adjacent pyrrolic beta-carbon atoms destabilizes the highest occupied molecular orbitals of the porphyrin pi-systems and accounts for the observed unique absorption properties. On the basis of these experimental and theoretical results, it can be concluded that the linear carbon-metal-carbon linkages weakly but definitely perturb the optical, photophysical, and electrochemical properties of the phosphametallacycle-linked coplanar porphyrin dimers.