Pt(II)- and Pt(IV)-bridged cofacial diporphyrins via carbon-transition metal sigma-bonds.
ABSTRACT A directly Pt(IV)-bridged cofacial diporphyrin has been synthesized by the cyclometalation reaction of beta-pyridylporphyrin with a Pt(IV) salt. Upon treatment with methylhydrazine, the Pt(IV) bridge is reduced to the Pt(II) center, resulting in a Pt(II)-bridged cofacial dimer with a helicity inversion of the complex as well as change in electronic communication through the metal bridge.
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ABSTRACT: Borylated functional π-systems are useful building blocks to enable efficient synthesis of novel molecular architectures with beautiful structures, intriguing properties and unique functions. Introduction of boronic ester substituents to a variety of extended π-systems can be achieved through either iridium-catalyzed direct C-H borylation or the two-step procedure via electrophilic halogenation followed by palladium-catalyzed borylation. This review article focuses on our recent progress on borylation of large π-conjugated systems such as porphyrins, perylene bisimides, hexabenzocoronenes and dipyrrins.Proceedings of the Japan Academy Ser B Physical and Biological Sciences 01/2014; 90(1):1-11. · 2.77 Impact Factor
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ABSTRACT: A meso-bromidoplatiniobis(triphenylphosphine) η(1) -organometallic porphyrin monomer was prepared by the oxidative addition of meso-bromoZnDPP (DPP=dianion of 5,15-diphenylporphyrin) to a platinum(0) species. The meso-meso directly linked dimeric porphyrin (5) was prepared from this monomer by silver(I)-promoted oxidative coupling and planarized to give a triply linked dizinc(II) porphyrin dimer (8). Acidic demetallation of 8 afforded the bis(free base) 9. Dimer 5 was demetallated then remetallated with nickel(II) to give the dinickel(II) analogue 10, the X-ray crystal structure of which showed a twisted molecule with ruffled, orthogonal NiDPP rings, terminated by square-planar trans-[Pt(PPh3 )2 Br] units. New compounds were fully characterized spectroscopically, and the fused diporphyrin exhibited a broad, low-energy, near-IR electronic absorption band near 1100 nm. Electrochemical measurements of this series indicate that the organometallic fragment is a strong electron donor towards the porphyrin ring. The triply linked organometallic diporphyrin has a substantially lowered first one-electron oxidation potential (-0.35 V versus the ferrocene/ferrocenium couple (Fc/Fc(+) )) and a narrow HOMO-LUMO gap of 0.96 V. Solutions prepared for NMR spectroscopy slowly decompose with degradation of the signals, which is attributed to partial oxidation to the cation radical. This paramagnetic species can be reduced in situ by hydrazine to restore the NMR spectrum to its former appearance. The combined influence of the two [Pt(PPh3 )2 Br] electron-donating substituents is sufficient to make dimer 5 too aerobically unstable to allow further elaboration.Chemistry - An Asian Journal 07/2013; · 4.57 Impact Factor
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ABSTRACT: 2,18-Bis(diphenylphosphino)porphyrins undergo peripheral cyclometalation with group 10 transition-metal salts to afford the corresponding porphyrin-based PCP pincer complexes. The porphyrinic plane and the PCP-pincer unit are apparently coplanar, with small strain. The catalytic activities of the porphyrin-based pincer complexes at the periphery were investigated in the allylation of benzaldehyde with allylstannane and in the 1,4-reduction of chalcone to discover the electronic interplay between the inner metal and the outer metal in catalysis.Angewandte Chemie International Edition 12/2013; · 11.34 Impact Factor