Porphyrin molecules self-assembly

A porphyrins-incorporated self-assembled monolayer (SAM) on gold, was prepared by formation of a 4-pyridinethiol SAM on gold followed by axial ligation of metalloporphyrins to it. The porphyrins-SAM was characterized by SERS and electrochemical techniques the macroplane of the porphyrin molecule assumes a nearly flat orientation with respect to the gold surface. 

In order to prepare and isolate solid-state, crystalline, oxygenated iron-heme model complexes, chemists learned to synthesize (by self-assembly methods) and oxygenate many types of hindered porphyrins. For instance, capped porphyrins were synthesized by direct condensation of a suitable tetraaldehyde with four pyrrole molecules.37 Picket-fence porphyrins such as I e(TPP)((V-MeIm) (where TPP = meso-tetraphenylporphyrin and /V-Melm = (V-methylimidazole)... 

Fig. 47 (a) Examples of polyphilic molecules with star shaped molecular topologies and (b) their mesophase morphologies [295]. (c) Janus-type porphyrin 177 [277] and (d) modes of self assembly of the completely RF-substituted porphyrin 156 left, for structure see Fig. 42, Colortho G -29 °C Colortho199 °C Iso) and the partly fluorinated porphyrin 177 right, ColTeJp2mg, Cr -22 °C Co n,Jp2mg 163 °C Iso) Colortho = orthorhombic columnar 3D phases (b) Reproduced with permission [295], copyright 2008, The Royal Society of Chemistry (RSC) (d) reproduced with permission [277], copyright 2011, American Chemical Society (ACS)...

It is also possible to study the self-assembly of individual molecules as well as networks such as 15.3. The V shaped zinc(II) bis (porphyrin) shown in Figure 15.20a self assembles into decaporphyrin pentagonic and dodecaporphyrin hexagonic assemblies. The assemblies can be fixed by alkene metathesis using Grubbs catalyst. This process represents self-assembly followed by covalent modification as described in Section 10.3.2. The assemblies can be directly imaged by high resolution STM (HRSTM)... 

FIGURE 7.26. (a) Molecular structure of compounds 42—45 (b) TEM images of a bundle of nanorods formed by compound 43 (Upper), and closer view of the bundle (Lower), (c) Pictorial representation of the nanorods formed by self-assembly of salt 43 in water, (d) Nanotubules formed by compound 45 observed at different scales. The measures of the two focused tubules are 35 x 530 and 50 x 470 nm. (e) Most stable dimeric structures of 45. Note that Upper is 6 kcal/mol per molecule more stable than Lower. (Upper) Interlayered structure (see text). (Lower) Porphyrin stacked structure. Notice that the porphyrin stacked structure is 2 kcal/mol per molecule more stable than the interlayered structure. 

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