Zinc porphyrins dimerization

A novel zinc porphyrin dimer (52) with a boronic ester linkage was prepared by Shinkai (Fig. 18) (65). The authors introduced an additional... 

If the free-base porphyrin is tetrasubstituted at the meso positions with 3- or 4-pyridyl ligands, pentamers are obtained on coordination to zinc porphyrin dimers (79) (65,66, Fig. 24). With the 3-pyridyl derivative all the porphyrin planes are coplanar, whereas in the case of the 4-pyridyl derivative the ligand porphyrins are approximately perpendicular to the plane of the zinc porphyrins. Quenching of the zinc porphyrin... 

Crossley (89) described the self-assembly of a spherical cage-like structure made up of two zinc porphyrin dimers bound to a tetramine ligand. The 2 1 complex is stable at 10-6m concentrations, but addition of excess of ligand causes dissociation of the capsule with formation of a 1 1 complex. 

Figure 13 Molecular structure of a co-facial zinc porphyrin dimer with a xanthene spacer.784...

Figure 1-6 Template efficiency parameters for the tetrapyridylporphyrin templated Glaser coupling of two zinc porphyrin dimers, in dichloromethane.

Fig. 16 Cyclotetramerization of alkynylene-bridged pyridyl zinc porphyrin dimer 30 and trimer 32...

Osuka has also designed a system comprised of a zinc porphyrin dimer (DP), a zinc porphyrin monomer (ZnP), and a pyromellitimide (pm) in place of the quinone (Figure 41). The pyromellitimide anion absorbs at... 

Porphyrin tweezer 51 was used to determine the absolute configuration of chiral diamines by measuring the CD spectrum of the diamine-51 complex. - Upon com-plexation, the two porphyrins adopt a chiral configuration, which leads to a coupled CD. The absolute configuration of amino acids and amino alcohols can be similarly detennined after derivatization to diamines. Ji and coworkers also reported CD smdies of the binding of diamine to a zinc porphyrin dimer. ... 

As we have just seen, electrostatic interactions can reinforce the formation of axial base complexes in metalloporphyrins, but other thermodynamically favored processes, such as chelation around a bidentate base like pyrazine, can be used. This approach has led Kuroda to the preparation of self-assembled dendrimer-type structures 86-89 represented in Figure 13.50 ". In these structures, the zinc porphyrin dimer formed by multihydrogen bonding of tetracar-boxylate derivatives of TPP is considered as a chelate. 

Figure 13.50. Dendrimer-like antenna structure formed by H-bonded zinc porphyrin dimers bound to pendant pyrazines on a free base porphyrin.

Yamaguchi, Y, Y. Yokomichi, S. Yokoyama, and S. Mashiko (2001). Time-dependent density functional calculations of the g-like bands of phenylene-linked free-base and zinc porphyrin dimers. Int. J. Quantum Chem. 84(3), 338-347. 

Yagi, S., M. Ezoe, I. Yonekma, T. Takagishi, and H. Nakazumi (2003). Diarylurea-linked zinc porphyrin dimer as a dual-mode artificial receptor Supramolecular control of complexation-faciUtated photoinduced electron transfer. J. Am. Chem. Soc. 125(14), 4068-4069. 

Because of space limitations, we will only briefly discuss the most basic application in the area of porphyrin optical spectra. Much work has already been done in this area, both with TDDFT and related methods. The TDDFT applications include free base porphin and its ss-octahalogenated derivatives, the porphyrinato-porphyrazinato-zirconiumhV) complex, NiP, NiPz, NiTBP, and NiPc, zinc phthalocyanine, chlorophyll a, zinc complexes of porphyrin, tetraazaporphyrin, tetrabenzoporphyrin, phthalocyanine, phenylene-linked free-base and zinc porphyrin dimers, metal bis(porphyrin) complexes a series of porphyrin-type molecules, and many more. We refer to ref. 75 for an extensive discussion of TDDFT calculations on the spectra of porphyrins and porphyrazines, as well as their interpretation. For further theoretical work on porphyrines, we mention ref. 76 and other papers in that special issue. 

Through coor nation motif, a tetra-pyrazinyl porphyrin-based assembly with four dimeric [meso-tetrakis(2-carboxy-4-nonylphenyl)porphyrinato]-zinc(II) as the antenna moiety was constructed by Kuroda et al. [113]. The efficiency of energy transfer from the zinc porphyrin-pyrazine complex to the free base porphyrin has been determined to be 82%. Also for this system, the observed efficiency of energy transfer is not so high compared with those reported for covalently finked multi-porphyrin systems [114]. Himter s group has designed a pentameric porphyrin array, wtiich was built up by the complementary coordination of a tetra-pyridyl porphyrin and two zinc-porphyrin dimers [115]. Steady-state and time-resolved fluorescence spectroscopic studies revealed that the energy transfer efficiency of this array is around 70%. 

Imahori et al. have reported the electron transfer assemblies 43, in which a zinc porphyrin dimer acts as the electron donor and benzoquinone or py-romellitimide serves as the electron acceptor [117,118]. Because of the two-sites binding of the electron acceptors with high stabilities, the assembhes 43a and 43b may form exclusively even at low concentrations typically used for spectroscopic studies. The electron transfer rate constants were found to be 1.6 X 10 ° s for 43a [117] and 2.1 x 10 ° s for 43b [118]. These nearly identical values suggest similar barriers for electron transfer at a comparable distance between chromophore and quencher. As the shortest through-space and through-bond pathways between the chromophore and the quencher in... 

Henderson J, Kubiak CP (2014) Photoinduced mixed valency in zinc porphyrin dimer of trimthenium cluster dyads. Inorg Chem 53(20) 11298-11306... 

Dime AKD, Devillers CH, Cattey H, Habermeyer B, Lucas D (2012) Control over the oxidative reactivity of metalloporphyrins. Efficient electrosynthesis of meso, meso-linked zinc porphyrin dimer. Dalton Trans 41 929-936... 

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