title: Effects of carbon-metal-carbon linkages on the optical, photophysical, and electrochemical properties of phosphametallacycle-linked coplanar porphyrin dimers.
abstract: 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 β-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 dπ-pπ orbital interaction between the peripherally attached metal and adjacent pyrrolic β-carbon atoms destabilizes the highest occupied molecular orbitals of the porphyrin π-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.
authors.affiliation: Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan. matano@scl.kyoto-u.ac.jp
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Matano
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Hironobu
authors.initials: H
authors.lastname: Hayashi
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Nakao
authors.forename: Tatu
authors.initials: T
authors.lastname: Kumpulainen
authors.forename: Vladimir
authors.initials: V
authors.lastname: Chukharev
authors.forename: Nikolai V
authors.initials: NV
authors.lastname: Tkachenko
authors.forename: Helge
authors.initials: H
authors.lastname: Lemmetyinen
authors.forename: Soji
authors.initials: S
authors.lastname: Shimizu
authors.forename: Nagao
authors.initials: N
authors.lastname: Kobayashi
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sakamaki
authors.forename: Akihiro
authors.initials: A
authors.lastname: Ito
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Tanaka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Imahori
mesh_terms: D002244:Carbon / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D019281:Dimerization; D055664:Electrochemical Techniques; D008958:Models, Molecular; D010165:Palladium / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D056831:Coordination Complexes; D011166:Porphyrins; D010984:Platinum; D010165:Palladium; D002244:Carbon