Porphyrin ladders

Taylor, P. N. Anderson, H. L. Cooperative self-assembly of double-strand conjugated porphyrin ladders./. Am. Chem. Soc. 1999,121, 11538-11545. 

As to multicyclic hetero-assemblies, Anderson and Taylor investigated the formation of a series of ladder complexes 32 (f = 3-6) and determined their stabihty constants in both toluene and CHCI3 as reported in Table 2 [38]. They claimed that ladder formation exhibit many indications of positive coopera-tivity. In contrast, Ercolani pointed out that the self-assembly of porphyrin ladders occurs without cooperative effects because the stabihty constants follow the expected statistical behavior [31]. The analysis of Ercolani was based on the apphcation of Eq. 25 to the self-assembly equihbria of 32 (z = 3-6), yielding Eq. 28. 

An example of cooperative metal coordination is Anderson s double-stranded porphyrin ladder (Fig. 4). This complex is formed by association of a conjugated porphyrin dimer with DABCO. 

Figure 4 (A) Anderson s double-stranded porphyrin ladder and (B) the reference system (R are solubilizing groups).

Anderson HL. Conjugated porphyrin ladders. Inorg Chem. 1994 33 972-981. 

Anderson has produced a range of improved zinc porphyrin-DABCO ladder complexes where an aromatic substituent in the meso position reduces aggregation (57). The 1H NMR spectra show a characteristic... 

The bis-dienes 13-15 form ladder-type bis-fullerene adducts. Cycloadditions proceed in good yields also with electron-deficient dienes such as 21-23. Porphyrin donor systems such as 25 or 30 or quinoidal acceptor systems such as 19 and 20 were introduced to study the properties of the charge transfer in Cjq donor-acceptor systems. 

Fig. 7.35 Construction of edge to edge ladder oligomeric porphyrins. Ar = an aromatic tetrammine.

Figure 27. A ladder-like supramolecular assembly (48) made from two rod-shaped Zn(ll) bis-porphyrins...

In few cases linear chain structured polymeric metal complexes were prepared. A linear polymeric phthalocyanine 60 was obtained as film by the electrochemical polymerization of the corresponding monomer [260]. The synthesis of structural uniform ladder polymers 61 based on the hemiporphyrazine structures was achieved by a repetitive Diels-Alder reaction [261,262]. Recently, linear oligomeric porphyrines covalently connected via meso-meso-positions up to 128 units were synthesized [263]. 

Anderson and coworkers [81] have extended this approach of metal-ligand mediated self-assembly of dyes to construct double-stranded, conjugated ladders 30 through cofacial bridging of metalloporphyrins. The zinc porphyrin polymer 29, which is soluble in chloroform even in aggregated form, is transformed into the ladder complex by the addition of the ditopic hgand 4,4 -... 

Linearly expanded porphyrin oligomers and polymers with enhanced third-order susceptibilities have also been reported. In solution the conjugation lengths of single-strand chains can be strongly limited by rotation and disorder. The self-assembly of double-strand ladder complexes of porphyrin butadiyne oligomers 21 achieves amplification in the nonlinearity... 

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