Zinc porphyrin guest

Similar types of interactions have been used by Kuroda to assemble, in a dimer fashion, two free base porphyrins around two zinc porphyrin guests, as shown in array 69 in Figure 13.44. ... 

Macrocyclic receptors made up of two, four or six zinc porphyrins covalently connected have been used as hosts for di- and tetrapyridyl porphyrins, and the association constants are in the range 105-106 M-1, reflecting the cooperative multipoint interactions (84-86). These host-guest complexes have well-defined structures, like Lindsey s wheel and spoke architecture (70, Fig. 27a), and have been used to study energy and electron transfer between the chromophores. A similar host-guest complex (71, Fig. 27b) was reported by Slone and Hupp (87), but in this case the host was itself a supramolecular structure. Four 5,15-dipyridyl zinc porphyrins coordinated to four rhenium complexes form the walls of a macrocyclic molecular square. This host binds meso-tetrapyridyl and 5,15-dipyridyl porphyrins with association constants of 4 x 107 M-1 and 3 x 106 M-1 respectively. 

The open-isomer of DTE having two zinc porphyrin moieties could form coordination complex with 4,4-bipyridyl like a tweezer (see Scheme 4), but the closed isomer could not bind cooperatively because of its structural rigidity. The different binding behavior of ZnP-DTE-ZnP with 4,4-bipyridyl was though to make the photo-control of affinity to guest molecules possible. 

The supramolecular approach mentioned above employs a dimeric zinc porphyrin reagent, now available under the name Zn-tweezer . The latter is capable of forming 1 1 host-guest complexes upon adding a solution of A7,A-bidentate conjugate, prepared by reacting the chiral substrate with an achiral trifiinctional bidentate carrier as shown in Figure 20.55 56... 

Huang, X. Rickman, B.H. Borhan. B. Berova. N. Nakanishi. K. Zinc porphyrin tweezer in host-guest complexation—Determination of absolute configurations of diamines, amino acids, and amino alcohols by circular dichroism. J. Am. Chem. Soc. 1998. 120. 6158. 

For the binding in organic solvents, zinc porphyrins are used in a number of studies, where a 1 1 complex is predominantly formed and a single equilibrium can describe the host-guest system. 

An example of a microreactor coupled to ESI-MS is the glass chip developed by Brivio et al, who studied the kinetics of different types of reactions, for example, metal-ligand interactions of zinc porphyrin with different pyridines and imidazoles and host-guest complexations of P-cyclodextrin with several compounds [69], and the... 

The molecular scissors can be further developed as molecular pliers (Figure 94), which can twist guest molecules by incorporating a zinc porphyrin unit at each cyclopentaduenyl ring of the ferrocene module. Owing... 

Zinc. Al NMR spectroscopy has been used to examine ethyl exchange between [Et2Zn] and [EtsAl] in the presence of crown ethers and azacrowns and has demonstrated the formation of [Et4Al]. " Some cavitand zinc porphyrins have been studied as receptors for a series of adamantyl- and pyridyl-containing guests. " The self-assembly of a cychc zinc porphyrin trimer has been studied by... 

Porphyrin-based molecular capsules 38 were obtained from two moles of respective tetra-pyridylporphyrin derivatives and four moles of cfs-Pd(II) dppp complexes through pyridine-Pd(II) coordinative interaction [95]. The structures of 38 were confirmed by H NMR and CSI-MS. NMR studies revealed that the capsules 38 have a highly symmetrical 4 structure with a large vacant cavity. The zinc porphyrin assemblies are able to accommodate large dipyridine guests such as 4,4 -trimethylenedipyridine with high affinity = 2.6 x 10 by a two-point simvdtaneous pyridine-zinc(II) interaction. 

Kurtan T, Nesnas N, Koehn FE, Li Y-Q, Ntikanishi K, Berova N (2001) Chiial recognition by CD-sensitive dimeric zinc porphyrin host. 2. Structural studies of host-guest complexes with chiral alcohol and monoamine conjugates. J Am Chem Soc 123(25) 5974-5982... 

Borovkov, V. V., Lintuluoto, J. M., Inoue, Y. Supramolecular chirogenesis in zinc porphyrins Mechanism, role of guest structure, and application for the absolute configuration determination./. Aw. Chem. 5 oc., 123,2979-2989 (2001). 

In addition to metal coordination bonds, hydrogen bondings, electrostatics, and 7T-7T interactions, the attractive interaction between the curved r-surface of a fullerene and the flat rr-surface of a porphyrin was recently reported [8,9]. When the fullerene and the porphyrin were linked covalently in the single molecule (see 6), the two functions interacted with each other to form a supramolecular assembly in the solid state. In contrast to this divergent system, macrocycle 7 was prepared from the fused zinc porphyrins for the convergent interaction with specific guests. Since 7 had space to accommodate two fuUerenes, this kind of interaction operated well in the supramolecular assembly and moleciflar recognition systems. 

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