Tetraphenylporphyrin molecule

A more general synthesis of selenophene derivatives, starting from diacetylenes and sodium hydrogen selenide, was investigated by Curtis.48 In the synthesis of new tetraphenylporphyrin molecules containing heteroatoms other than nitrogen, Ulman et al.49 used in principle the method of Curtis for the synthesis of the starting material (17). 

Until recently, despite the number of the examples of the formation of cobalt(II)- and iron(II)-tetraphenylporphyrins (MTPP) (107,108) from the direct reaction of the bare metal atoms (Co or Fe) and adsorbed tetraphenylporphyrin molecules (2HTPP), it was only possible to speculate (107-110) about the reaction mechanism, since the reaction is fast at 300 K, and thus no intermediates could be observed. 

By complexing phthalocyanine or tetraphenylporphyrin molecules with different bivalent metal ions, their oxidation potential may be changed, and this also appeared to change their catalytic activity. In Fig. 3 this is shown graphically. 

Gopakumar TG, Tang H, MoriUo J, Bemdt R (2012) Transfer of Q ligands between adsorbed iron tetraphenylporphyrin molecules. J Am Chem Soc 134 11844-11847. doi 10.1021/ja302589z... 

LB Films of Porphyrins and Phthalocyanines. The porphyrin is one of the most important among biomolecules. The most stable synthetic porphyrin is 5,10,15,20-tetraphenylporphyrin (TPP). Many porphyrin and phthalocyanine (PC) derivatives form good LB films. Both these molecules are important for appHcations such as hole-burning that may allow information storage using multiple frequency devices. In 1937 multilayers were built from chlorophyll (35). 

Dye-Sensitized Photoisomerization. One technological appHcation of photoisomerization is in the synthesis of vitamin A. In a mixture of vitamin A acetate (all-trans stmcture) and the 11-cis isomer (23), sensitized photoisomerization of the 11-cis to the all-trans molecule occurs using zinc tetraphenylporphyrin, chlorophyU, hematoporphyrin, rose bengal, or erythrosin as sensitizers (73). Another photoisomerization is reported to be responsible for dye laser mode-locking (74). In this example, one metastable isomer of an oxadicarbocyanine dye was formed during flashlamp excitation, and it was the isomer that exhibited mode-locking characteristics. 

When multiple peripheral substituents, as in [Ni(2,3,5,7,8,10,12,13,15,17,18,20-dodecaphenyl-porphyrin)], [Ni(5,10,15,20-tetra(/-butyl)porphyrin)], [Ni(2,3,7,812,13,17,18-tetracyclohexenyl-5,10,15,20-tetraphenylporphyrin)], and [Ni(OETPP)], cause the macrocycles to become nonplanar,283,284 the HOMOs of the porphyrins are destabilized and the molecules become easier to oxidize.283,285 In accord with the general discussion above, these compounds are oxidized to tt cation radicals and remain so even at low temperatures in CH2C12. However, upon addition of... 

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)... 

An interesting variant of the deposition of disc-type molecules on surfaces and of the single molecule detection is to increase the distance between the adsorbate molecule and the surface by introducing bulky 3,5-di-tert-butylphenyl substituents. This has been done for the tetraphenylporphyrin... 

Polymerization of methyl methacrylate (MMA) was initiated with methylalumi-num tetraphenylporphyrin (1, X=Me) under irradiation with visible light. At a monomer conversion less than 10%, Lewis acids such as methylaluminum diphenolates 3a-i and methylaluminum dialcoholates 4a,b were added to the system in order to examine whether they could accelerate the polymerization (Scheme 2) (Table 1). For example, a CH2CI2 solution (10 ml) of a mixture of MMA and 1 (X=Me) with a mole ratio of 217 was irradiated at 35 °C with xenon arc light (k>420 nm) to initiate the polymerization. During 2.5-h irradiation, all the molecules of the initiator 1 (X=Me) were transformed into the growing enolate species 2 (R=Me), where the conversionof the monomer was 6.1%, as estimated by NMR. 

Zinc-5,10,15,20-tetraphenylporphyrin (ZnTPP) has been used as a coating material in ammonia sensors by immobilizing it on the surface of silicone rubber. Absorbance and fluorescence emission were the modes of detection. A spectral change is caused by the coordination of NH3 molecules to the Zn11 ion in the immobilized metalloporphyrins. Sensing films made from the ZnTPP immobilized in silicone rubber were found to be the most sensitive for NH3 sensing (20). 

Homonuclear correlation spectroscopy (COSY) experiments (see Chapter 9) substantiate the theoretical predictions, based on molecular orbital calculation, of the pattern of spin delocalization in the 3e orbitals of low-spin Fe(III) complexes of unsymmetrically substituted tetraphenylporphyrins [46]. Furthermore, the correlations observed show that this n electron spin density distribution is differently modified by the electronic properties of a mono-orf/io-substituted derivative, depending on the distribution of the electronic effect over both sets of pyrrole rings or only over the immediately adjacent pyrrole rings [46]. No NOESY cross peaks are detectable, consistently with expectations of small NOEs for relatively small molecules and effective paramagnetic relaxation [47]. 

Figure 11. 15N NMR MAS NMR spectra and tensor results for [15N4]-ring labeled metalloporphyrins. A, 8.45 Tesla 15N MAS NMR spectrum of Fe(tetraphenylporphyrinate)(PhNO)( 1 -methylimidazole), vr = 2.6 kHz. B, graph showing correlation between experimental and DFT computed I5N tensor elements for Fe(TPP)(PhNO)( 1 -Melm) ( ) and Fe(TPP)(CO)(l-MeIm) (O). The mean experimental and theoretical shieldings over the four non-equivalent sites in each molecule are shown since the solid state shifts are not specifically assigned. Slope = 0.847, R2 = 0.995.

Acetylrhodium(III) tetraphenylporphyrin was formed on warming N,N-dimethylacetamide solutions of RhH(TPP) [319]. Obviously, an acetyl group had been abstracted from a solvent molecule. 

As in the case of the ZSM-5 zeolite sample [160], in substrate in Nafion-DCA in CH2C12, due to the isolation of the sensitizer in solution from the substrate in Nafion, only the products derived from the energy-transfer pathway were detected. The sensitized photo-oxidation of DPB gave 6 as the unique product (Fig. 18), whereas that of TS yielded 10 and 13 (Fig. 19). The oxidation products of TS with 102 in this mode are the same as in solution sensitized by HA or tetraphenylporphyrin, but different from that in ZSM-5 zeolite, where benzaldehyde 1 is the unique product. This observation suggests that the constrained space in the water-containing pocket of Nafion membranes can accommodate the molecules of 10 and 13. In contrast, irradiation of the water-swollen... 

Most of the porphyrinoid molecules synthesized so far possess a number of peripheral substituents. In fact, many of the important macrocyclic systems were obtained with several distinct substitution patterns. Usually they correspond to one of the generic substitution types of regular porphyrins meso-aryl or p-alkyl, as exemplified by 5,10,15,20-tetraphenylporphyrin and 2,3,7,8,12,13,17,18-octaethylporphy-rin, respectively (Fig. 2). For the sake of brevity we will assume the following conventions in the entire manuscript ... 

The 18 7r-electron structure has the stability of an aromatic ring according to the Hiickel 4n + 2 rule, while the others may be considered to be active like the semiquinone or quinone. So, when an oxidizing agent can be found to oxidize the aromatic molecule, a structure is formed which may abstract a hydrogen atom, by which it is reduced again. A mixture of nitrobenzene and cyclohexadiene-1,4 suited this purpose, and complexes of phthalocyanine and tetraphenylporphyrin were found to catalyze the oxidative dehydrogenation of cyclohexadiene by nitrobenzene t00> ... 

In a supramolecular approach to fullerene-porphyrin hybrids, the assembly of a rigidly connected dyad, in which a zinc tetraphenylporphyrin, Zn(TPP), is noncovalently linked to a C60 derivative via axial pyridine coordination to the metal, was reported [219-222]. Photo excitation of the dyad Zn-complex led to electron transfer with very long lifetimes of the charge-separated pairs, as revealed by optical spectroscopy and confirmed by time-resolved electron paramagnetic resonance spectroscopy. Accordingly, two different solvent-dependent pathways can be considered for the electron-transfer processes. Either the excitation of the porphyrin chromophore is followed by fast intramolecular electron transfer inside the complex, or alternatively the free porphyrin is excited undergoing intermolecular electron transfer when the acceptor molecules ap-... 

Tsuchiya has succeeded in controlling intramolecular electron transfer through photoisomerization by employing a molecule in which two tetraphenylporphyrin units (free-base and/or Zn complex) are connected at... 

Continuing our current studies on porphyrin Mn complexes (31, 32, 33), some Mn(II) complexes have been found to activate the oxygen molecule very efficiently under certain conditions, and this chapter reports the oxidation of olefins using molecular oxygen activated by a tetraphenylporphyrin-Mn(II) complex. 

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