Porphyrins supramolecular system

Mizutani, 7., Ema, T. Yoshida, T. Renn, T. Ogoshi, H. Mechanism of induced circular dichroism of amino acid ester-porphyrin supramolecular systems—Implications to the origin of the circular dichroism of hemoprotein. Inorg. Chern. 1994, 33, 3558. 

Advance in the construction and apphcation of cyclodextrin—porphyrin supramolecular system 12CJ0686. 

The transition state of concerted Diels-Alder reactions has stringent regio- and stereochemical requirements and can assume settled configurations if the reaction is carried out in a molecular cavity. Cyclodextrins, porphyrin derivatives and cyclophanes are the supramolecular systems that have been most investigated. 

The conjugation in the molecular wire may be disrupted or modulated to create systems with different properties. For example, a porphyrin Ceo donor-acceptor system linked with a conjugated binaphthyl unit, has a preference for the atropi-somer where the fullerene unit is closer to the porphyrin system, thus increasing the through space interactions [82]. The charge transfer process on a dyad containing a crown ether in the linker structure can be modulated by complexation/ decomplexation of sodium cations [83] but even more interesting is the construction of supramolecular systems where the donor and acceptor moieties are... 

A chromophore such as the quinone, ruthenium complex, C(,o. or viologen is covalently introduced at the terminal of the heme-propionate side chain(s) (94-97). For example, Hamachi et al. (98) appended Ru2+(bpy)3 (bpy = 2,2 -bipyridine) at one of the terminals of the heme-propionate (Fig. 26) and monitored the photoinduced electron transfer from the photoexcited ruthenium complex to the heme-iron in the protein. The reduction of the heme-iron was monitored by the formation of oxyferrous species under aerobic conditions, while the Ru(III) complex was reductively quenched by EDTA as a sacrificial reagent. In addition, when [Co(NH3)5Cl]2+ was added to the system instead of EDTA, the photoexcited ruthenium complex was oxidatively quenched by the cobalt complex, and then one electron is abstracted from the heme-iron(III) to reduce the ruthenium complex (99). As a result, the oxoferryl species was detected due to the deprotonation of the hydroxyiron(III)-porphyrin cation radical species. An extension of this work was the assembly of the Ru2+(bpy)3 complex with a catenane moiety including the cyclic bis(viologen)(100). In the supramolecular system, vectorial electron transfer was achieved with a long-lived charge separation species (f > 2 ms). 

The representative examples of chirogenic assemblies on the basis of achiral monomeric porphyrinoids exposed to a chiral influence clearly show their great importance and wide applicability in various fields. The major chiroptical properties of these relatively simple supramolecular systems include transferring the chiral information and controlling the induced asymmetry by different factors. However, another type of chirogenic process— modulation of inherent chirality is going to be illustrated for chiral porphyrins in the next sections. 

The aforementioned representative examples of chirogenic supramolecular systems based on monomeric porphyrinoids clearly demonstrate their vital importance and wide applicability in various fields, while many aspects of the operating mechanisms and especially chiroptical properties have yet to be comprehensively investigated and well understood. However, in many cases just a monomeric porphyrin cannot function properly without the synergetic assistance of another porphyrin unit (or several porphyrins) that give rise to chirogenic supramolecular assemblies built upon the dimeric/oligomeric porphyrinoids, which will be discussed in subsequent sections. 

Chirogenic supramolecular systems based on dimeric/oligomeric porphyrinoids can also be classified according to their complexity and structural features. First, the assemblies consisting of two or more monomeric porphyrins fixed in an asymmetrical fashion by chiral bridges via supramolecular binding will be examined. 

Supramolecular systems on the basis of dimeric and oligomeric porphyrinoids are varied depending upon the chirality of the supramolecular counterparts, type of the covalent linkage, and number of the porphyrin subunits. Firstly, we shall examine examples of the assemblies consisting of achiral and racemic bis-porphyrinoid hosts and chiral guests. 

In order to comprehensively investigate various chiroptical aspects of the bis-porphyrin-based supramolecular systems and unambiguously rationalize... 

This type of porphyrin host can also interact with achiral guests and with chiral guests to generate corresponding supramolecular systems, and interaction with the achiral supramolecular counterparts will be discussed first. 

El-Khouly ME, Ito O, Smith PM, D Souza F. Intermolecular and supramolecular photoinduced electron transfer processes of fullerene-porphyrin/phthalocyanine systems. J Photochem Photobiol C Photochem Rev 2004 5 79-104. 

D Souza F, Ito O. Photoinduced electron transfer in supramolecular systems of fuller-enes functionalized with ligands capable of binding to zinc porphyrins and zinc phthalo-cyanines. Coord Chem Rev 2005 249 1410-22. 

Recently, crown-related macrocycles have been applied to new supramolecular systems such as porphyrins, calixarenes, catenanes, and rotaxanes, and so on. To cover the widespread area in limited pages, this chapter mainly focuses on the syntheses and functions of crown-related macrocycles having 10-membered rings or larger with one or more O and S atoms. Therefore, the standard arrangement in 12 sections could not be applied in this chapter related to that of CHEC-II(1996) (Chapters 9.29 and 9.31). 

Other large supramolecular systems incorporating (circularly) linked porphyrin rings have been reported. An example of this type, 37 (see Figure 7.13), was reported by Sanders et The preparation of this novel species proceeds via the ini-... 

A large number of covalently linked systems are currently being synthesized and investigated, differing in the nature of A, B, and L, as well as in the number of functional units in the supramolecular system (nuclearity). It is common to call simple two-component donor-acceptor systems such as that of Eq. 2 dyads , and progressively more complex systems triads , tetrads , pentads , etc.. Systems where all the A and B units are organic molecules are dealt with in Chapter 1 of this section. The present chapter deals with systems where at least one of the A/B functional units is a transition metal coordination compound. From this definition, however, are excluded (a) systems where A and/or B are porphyrins or related species (dealt with in Chapter 2) and (b) systems of high nuclearity with dendritic structures (dealt with in Chapter 9). 

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