Effects of Carbon鈥揗etal鈥揅arbon Linkages on the Optical, Photophysical, and Electrochemical Properties of Phosphametallacycle-Linked Coplanar Porphyrin Dimers

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• 作者：Yoshihiro Matano ; Kazuaki Matsumoto ; Hironobu Hayashi ; Yoshihide Nakao ; Tatu Kumpulainen ; Vladimir Chukharev ; Nikolai V. Tkachenko ; Helge Lemmetyinen ; Soji Shimizu ; Nagao Kobayashi ; Daisuke Sakamaki ; Akihiro Ito ; Kazuyoshi Tanaka ; Hiroshi Imahori
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：January 25, 2012
• 年：2012
• 卷：134
• 期：3
• 页码：1825-1839
• 全文大小：717K
• 年卷期：v.134,no.3(January 25, 2012)
• ISSN：1520-5126

文摘

5-(Diphenylphosphanyl)-10,15,20-triarylporphyrins (meso-phosphanylporphyrins) underwent complexations with palladium(II) and platinum(II) salts to afford phosphapalladacycle- and phosphaplatinacycle-fused coplanar porphyrin dimers, respectively, via regioselective peripheral 尾-C鈥揌 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鈥搗is 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鈥搕riplet intersystem-crossing process at the excited state. It has also been revealed that the C鈥揚t鈥揅 linkage makes more significant impacts on these fundamental properties than the C鈥揚d鈥揅 linkage. Furthermore, density functional theory calculations on the metal-linked porphyrin dimers have suggested that the antibonding d蟺鈥損蟺 orbital interaction between the peripherally attached metal and adjacent pyrrolic 尾-carbon atoms destabilizes the highest occupied molecular orbitals of the porphyrin 蟺-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鈥搈etal鈥揷arbon linkages weakly but definitely perturb the optical, photophysical, and electrochemical properties of the phosphametallacycle-linked coplanar porphyrin dimers.