Molecular structure of porphyrins

Figure 5.12 Molecular structures of porphyrin PDF and its manganese complex PDP-Mn.

Fig.4 Molecular structures of porphyrin host (3) and clip guest molecule (4)...

Fig. 22 Molecular structure of porphyrin 35 and molecular packing of 35a-2Ceo-toluene (reprinted with permission from [90]. (2006) WILEY-VCH)...

An unusual porphyrin-supported hafnium guanidinate was obtained from the reaction of (TTP)Hf=NAr (TTP = meso-tetra-p-tolylporphyrinato dianion, Ar = 2.6-diisopropylphenyl) with 1,3-diisopropylcarbodiimide. The molecular structure of the product, (TTP)Hf[Pr NC(NPr )(NAr)] is shown in Figure 24. ° ... 

Fk . 7. Molecular structures of selected organomctallic rhodium and iridium porphyrin com-... 

Figure 13 Molecular structure of a co-facial zinc porphyrin dimer with a xanthene spacer.784...

The out-of-plane orientation of chromophores can be more easily controlled in LB films as compared with the in-plane orientation. Many chromophores are known to show anisotropic orientation in the surface normal direction. The molecular structure of chromophores and their position in amphiphile molecules, the surface pressure, the subphase conditions are among those affect their out-of-plane orientation. The out-of-plane orientation has been studied by dichroic ratio at 45° incidence, absorbance ratio at normal and 45° incidence, and incident angle dependence of p-polarized absorption [3,4,27,33-41]. The evaluation of the out-of-plane orientation in LB films is given below using amphipathic porphyrin (AMP) as an example [5,10,12]. 

An important class of porphyrins is that constituted by confor-mationally distorted porphyrins, which mimic the non-planar geometry of the porphyrins present in photosynthetic systems.89 Obtainment of such non-planar distortions is associated with the introduction into the macrocyclic frame of proper crowding substituents, which therefore not only cause structural distortion but also affect, through their electronic effects, the redox potentials. A typical case is that constituted by [Cun(OETPP)] (OETPP = 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin), the saddle-distorted molecular structure of which is illustrated in Figure 56.102... 

The molecular structure of a Co(II) macrocycle complex that in some way mimics the strapped-type metal-porphyrin complexes is illustrated in Figure 13.18 19... 

Rg. 5. Molecular structures of selected Group 13 organometallic porphyrin complexes (a) AKOEPXCHs), (b) InfEtioPcXCeHslJ (c) Ga(TAP)(CH=CH2) (TAP = tetraanisylpor-... 

Fig. 7. Molecular structures of selected Group 15 organometallic porphyrin cations and complexes (a) [P(0EP)(C6H5)(0H)]PF6, (b) P(OEP)(C2H5)(=0), 5 [P(OETPP)(CH3)2]PF6, ...

Fig. 9. Molecular structures of selected metal—metal bonded main group porphyrin complexes (a) (OEP)InMn(CO)5, 54 (b) (OEP)SnFe(CO)4, (c) (TPP)SnMn(CO)4HgMn(CO)5. ...

As already mentioned, the coordination type of the Ru, Os, Rh and Ir porphyrins is C (Fig. 2), i.e. distorted octahedral about the metal which is in most cases a d6 system occasionally, d5, d4, or d2 systems are encountered. Table 2 gives a compilation of compounds the molecular structures of which have been determined by X-ray crystallography. The numbers of entries given for the individual noble metals approximately reflects the intensity of research done for the respective metal. For details and special structural aspects, the reader is referred to the original literature and a previous review by Scheidt and Lee [143]. Here, just a few general notes will be made. Phthalocyanine systems are not incorporated. 

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. 

The first silylene complexes of osmium porphyrin, (TTP)Os=SiR2-THF, were prepared by treating K2[Os(TTP)] with Cl2SiR2 or the reaction of [Os(TTP)]2 with hexamethylsilacyclopropane (116). The molecular structure of (TTP)Os=SiEt2-2THF is stabilized by coordination of THF to the silicon, as shown by X-ray crystallography (Fig. 5). The measured Os—Si distance of 2.325(8) A is the shortest ever reported (116). 

Figure 2.5 Molecular structures of zinc-iron porphyrin complexes across (a) hydrogen, (b) aliphatic and (c) aromatic bridges, and the corresponding rates of photoinduced electron transfer for each species, as reported by Rege et al. [12]...

In the next example, a mixed SAM is discussed which aims to utilize photoinduced energy and electron transfer processes to create a photocurrent in an approach which is reminiscent of the natural photosynthetic process. Figure 5.33 illustrates the molecular structures of the components of interest, i.e. the molecular triad ferrocene-porphyrin-fullerene (Fc-P-C6o) and a boron dipyrrin thiol (BoDy) [67]. Mixed monolayers were generated by coadsorption onto vacuum-deposited gold... 

Figure 5.44 (a) General molecular structure of the porphyrin disulfides, PDSn, described by Ishida and Majima [76]. (b) Changes in the surface plasmon enhanced fluorescence spectra for the exchange reaction of a decane thiol SAM with a 50 mmol dm-31,2-dichloroethane solution of PDS10 (Xem = 725 nm Xex = 425 nm). From A. Ishida and T. Majima, /. Chem. Soc., Chem. Commun., 1299-1300 (1999). Reproduced by permission of The Royal Society of Chemistry... 

Figure 5.52 General molecular structure of the surface active porphyrin-ferrocene-thiol supra-molecular complexes reported by Uosaki and co-workers [82]. (b) Energy diagram illustrating the mechanism behind photocurrent generation in SAMs of such complexes at cathodic electrode potentials of the Fc/Fc+ couple P, porphyrin Fc, ferrocene MV2+, methyl viologen...

Imahori et al. reported on the energy transfer in mixed self-assembled monolayers of pyrene and porphyrin [83]. The molecular structures of the disulfide-terminated chromophores are illustrated in Figure 5.53. Porphyrin and pyrene dimers were coadsorbed onto Au(lll) mica substrates in different ratios. The ratios of pyrene to porphyrin were experimentally determined from absorption spectroscopy and the pyrene dimer was observed to adsorb preferentially, possibly due to its strong... 

Figure 5.53 Molecular structures of the (a) pyrene and (b) porphyrin monolayer components in the mixed self-assembled monolayers reported by Imahori et al. [83]...

Fig. 7 Molecular structures of monomeric porphyrins used as semiconductor of OFETs...

Given the similarities in chemical shifts and linewidths, as well as the contributions of symmetry to the appearance of the spectrum, the electronic and molecular structure of new iron complexes of N-alkyl-porphyrins may be ascertained, to a first approximation, from NMR data. Thus for low-spin iron(III) complexes one would expect at least four sharp resonances upfield of the diamagnetic region. Iron(IV) complexes should have at least four resonances upfield of the diamagnetic region. Iron(III) can be differentiated from iron(IV) by measurement of the solution susceptibility (51). 

Maranon, M. J. R., Stillman, M. J., and van Huystee, R. B., 1993, CD analysis of co-dependency of calcium and porphyrin for the integrate molecular structure of peanut peroxidase, Biochem. Biophys. Res. Comm. 194 326n333. 

Figure 4 Molecular structure of O2-bound picket fence iron porphyrin complex. The iron porphyrin has four pivalamide groups forming a hydrophobic cavity for the ligand O2. The axial ligand is 1,2-dimethylimidazole. X-ray crystal structure shows the end-on and bent coordination of O2 to the heme-iron...

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