Double-decker porphyrins

Typical sigmoid isotherms are shown in Fig. I for cooperative binding of dicarboxylic acids 16 and 17 to a double-decker porphyrin with pyridine substituents 15a (see below. Fig. 5/ The Hill coefficient for these systems h=4 equals the total number of bound guests as a result of a strong positive allosteric effect. 

Sugasaki developed the cerium(IV) Z)A(porphyrinate) double decker porphyrin 247 as a scaffold for the recognition of oligosaccharides such as sialyl Lewis Binding of the first guest species suppresses the rotational... 

Coordination compounds composed of tetrapyrrole macrocyclic ligands encompassing a large metal ion in a sandwich-like fashion have been known since 1936 when Linstead and co-workers (67) reported the first synthesis of Sn(IV) bis(phthalocyanine). Numerous homoleptic and heteroleptic sandwich-type or double-decker metal complexes with phthalocyanines (68-70) and porphyrins (71-75) have been studied and structurally characterized. The electrochromic properties of the lanthanide pc sandwich complexes (76) have been investigated and the stable radical bis(phthalocyaninato)lutetium has been found to be the first example of an intrinsic molecular semiconductor (77). In contrast to the wealth of literature describing porphyrin and pc sandwich complexes, re-... 

Other homoleptic Lu(III) sandwich complexes 23, 25 (78), and 27 (34), have been prepared accordingly, as in Scheme 6. Zirconium sandwich complexes have been prepared by the method employed by Kim et al. (80) for the synthesis of zirconium porphyrin double deckers reaction of Zr(lV-Et2)4 with the pz ligands 24 (35%) and 26 (61%) produced the corresponding sandwich complexes (28 and 29) (Scheme 6). 

To construct such a porphyrin-based positive allosteric system, we chose a cerium(iv) bis(porphyrinate) double decker compound 184-861 namely the tetrakis(4-pyridyl)porphyrin derivative 38.[871 This molecule satisfies the aforementioned requirements firstly, slow rotation of the two porphyrin planes with respect to one another should be possible at room temperature,1881 in analogy to similar cerium(iv) bis(diarylporphyrin) and bis(tetraarylporphyrin) complexes studied by Aida et al/861 Secondly, tilting of two porphyrin planes is more difficult than in 37, and thirdly, four pairs of 4-pyridyl groups are available as hydrogen bond acceptor sites for diols, hydroxycarboxylic acids, and dicarboxylic acids. Compound 39, which has only one pair of pyridyl groups, was used as a reference. 

The importance of these two factors can be easily understood by the following examples. Shinkai and coworkers widely employed a double-decker architecture of the center-to-center bound bis-porphyrins 32-39 designed on the basis of //-oxo dimers and Ce complexes to sense the chirality of... 

Yarasir MN, Kandaz M, Koca A, Salih B (2006) Functional alcohol-soluble double-decker phthalocyanines synthesis, characterization, electrochemistry and peripheral metal ion binding. J Porphyrins Phthalocyanines 10(8) 1022-1033... 

Except for the homoleptic bi(porphyrinato) and tri(porphyrinato) rare earth complexes, complexes with different porphyrin macrocycles were also investigated. To date, some sandwich type heteroleptic bis(porphyrinato) rare earth double-deckers have been synthesized. However, few have been structurally characterized via single crystal X-ray diffraction analysis [47]. Among these, Ce(IV)(OEP)(TPP) is the only structurally characterized neutral heteroleptic bis(porphyrinato) rare earth double-decker complex [48]. Using an improved short route, Coutsolelos and coworkers prepared and isolated a series of heteroleptic bis(porphyrinato)... 

Figure 4.32 The structure of complex Sm(III)H(OEP)(TPP) [48]. (Reprinted with permission from G. A. Spyroulias, etah, Synthesis, characterization, and X-ray study of a heteroleptic samarium(III) porphyrin double decker complex, Inorganic Chemistry, 34, no. 9,2476-2479, 1995. 1995 American Chemical Society.)...

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