Aiko Nakano

WINDMILL-LIKE PORPHYRIN ARRAYS AS POTENT LIGHT-HARVESTING ANTENNA COMPLEXES

Up to 14 porphyrin rings are present in the title compounds 1, which are readily available with high regioselectivity from linear nickel-zinc porphyrins. Upon irradiation with light a rapid energy transfer from the peripheral porphyrin rings to the diporphyrin core takes place.

Doubly meso‐β‐Linked Diporphyrins from Oxidation of 5,10,15‐Triaryl‐Substituted NiII– and PdII – Porphyrins

Lower oxidation potentials than for the monomeric starting materials are displayed by the diporphyrins obtained by one-electron oxidation with tris(4-bromophenyl)ammonium hexachloroantimonate [see, for example, Eq. (1)]. This and the strong red shift observed for the Soret bands of the product are indicative of extensively delocalized π-electron systems in the fused diporphyrin. Ar=3,5-di-tert-butylphenyl.

Three-dimensionally arranged windmill and grid porphyrin arrays by AgI-promoted meso-meso block oligomerization

The syntheses of soluble windmill and grid porphyrin arrays through the AgI-promoted coupling reaction of 1,4-phenylene-bridged linear porphyrin arrays, which are comprised of a central ZnII beta-free porphyrin and flanking peripheral NiII beta-octaalkylporphyrins, are described. The coupling reaction is advantageous in light of its high regioselectivity occurring only at the meso-position of the ZnII beta-free porphyrin as well as its easy extension to large porphyrin arrays. The windmill porphyrin arrays in turn serve as an effective substrate for further coupling reactions, to give three-dimensionally arranged grid porphyrin arrays. Further the grid porphyrin 12-mer (a tetramer of the linear porphyrin trimer) was also coupled to afford grid porphyrins (24-mer, 36-mer, and 48-mer). These porphyrin arrays were isolated in a discrete form by repetitive GPC/HPLC (GPC= gel-permiation chromatography). Competitive experiments with three linear porphyrin trimers bearing different peripheral metalloporphyrins (ZnII, NiII, and Cull), and the trapping experiment of the radical cation at the peripheral porphyrin with AgNO2, suggested that an initial one-electron oxidation of the easily oxidizable peripheral ZnII beta-octaalkylporphyrin with an AgI ion and a subsequent endothermic hole transfer assist the generation of the radical cation at the central ZnII beta-free porphyrin. In all ZnII-metallated windmill porphyrin arrays, the energy level of the S1 state of the meso-meso-linked diporphyrin core is lower than that of the peripheral porphyrins, thereby allowing an energy flow from the peripheral porphyrins to the central diporphyrin core; this has been confirmed by measurements of fluorescence lifetimes and picosecond time-resolved fluorescence spectra. The excitation energy transfer in the arrays encourages their potential use as an light-harvesting antenna.

FACILE REGIOSELECTIVE MESO-IODINATION OF PORPHYRINS

Abstract Treatment of 5, 15-diaryl zinc-porphyrins with AgPF 6 and iodine in a mixture of CHCl 3 and pyridine (60:1) resulted in meso-iodination of porphyrins with high regioselectivity.

Windmühlenartige Porphyrinaggregate als lichtsammelnde Antennenkomplexe

Bis zu 14 Porphyrinringe enthalten die Titelverbindungen 1, die einfach und regioselektiv aus linearen Nickel-Zink-Porphyrinoiden zuganglich sind. Nach Bestrahlung mit Licht findet ein rascher Energietransfer von den auseren Porphyrinringen auf die zentrale Diporphyrineinheit statt.

Imido transfer of sulfonylimino-lambda3-bromane makes possible the synthesis of sulfonylimino-lambda3-iodanes.

Sulfonylimino-lambda(3)-bromane functions as a reactive nitrenoid, because of the hyperleaving group ability of aryl-lambda(3)-bromanyl groups, and undergoes transimidations to iodobenzenes at room temperature under metal-free conditions probably via an S(N)2-type nitrenoid transition state, yielding sulfonylimino-lambda(3)-iodanes.

Directly linked dehydropurpurin–porphyrin dyads from Ag(I)-promoted oxidation of meso-phenylethynyl substituted zinc(II) porphyrins

Ag(I)-promoted oxidation of (5,15-diaryl-10-phenylethynyl-porphyrinato)zinc(II) complexes in CHCl3 gave directly linked 12,13-dehydropurpurin-porphyrin dyads, the structures of which were revealed by X-ray analysis.

Electric Field Effects on Absorption and Emission Spectra of End-Phenylethynylated Meso-Meso Linked Porphyrin Arrays in a Polymer Film

Supramolecular chemistry based on a porphyrin building block has attracted much attention in light of a biomimetic construction of biologically functional networks as well as a scientific investigation of new materials applicable as a molecular-scale devise.1-6

Directly Linked and Fused Oligoporphyrin Arrays

The design and preparation of linear, rigid, rod-like, conjugated molecules with precise length and constitution have attracted much interest in light of their potential applications as liquid crystals, optical devices, sensors, molecular machines, and conductive molecular wires.1 With these backgrounds, numerous attempts have been made to prepare the linear, rod-like, conjugated molecules.2 In most cases, aromatic groups or chromophores are connected with rigid spacer molecules or directly without spacer, thereby to construct large π-electronic arrays in a repetitive manner.

Excitation delocalization and relaxation in linear and circular arrays of porphyrins

Photophysical processes such as excitation energy transfer and electron transfer are expected to occur very fast in organized molecular systems in which reactant molecules are arranged with close proximity and optimal orientation, and they can be coupled to an adjacent molecule with relatively strong molecular interaction. In an extreme of such strongly interconnected molecular systems, the photoinduced reaction can compete with or exceed the vibrational relaxation from vibrational levels initially photoexcited. We have investigated ultrafast excitation migration and relaxation in circular and linear arrangements of zinc porphyrin (ZnP) with a femtosecond fluorescence up-conversion method and a ps time-correlated photon-counting method. The time-resolved fluorescence spectra revealed non-equilibrium processes of excitation delocalization and transport in femtosecond and picosecond time scales.