Tetraphenylporphine

Iron Porphyrins. Porphyrias (15—17) are aromatic cycHc compouads that coasist of four pyrrole units linked at the a-positions by methine carbons. The extended TT-systems of these compounds give rise to intense absorption bands in the uv/vis region of the spectmm. The most intense absorption, which is called the Soret band, falls neat 400 nm and has 10. The TT-system is also responsible for the notable ring current effect observed in H-nmr spectra, the preference for planar conformations, the prevalence of electrophilic substitution reactions, and the redox chemistry of these compounds. Porphyrins obtained from natural sources have a variety of peripheral substituents and substitution patterns. Two important types of synthetic porphyrins are the meso-tetraaryl porphyrins, such as 5,10,15,20-tetraphenylporphine [917-23-7] (H2(TPP)) (7) and P-octaalkylporphyrins, such as 2,3,7,8,12,13,17,18-octaethylporphine [2683-82-1] (H2(OEP)) (8). Both types can be prepared by condensation of pyrroles and aldehydes (qv). 

Cobalt (II) meso-5.10,15,20-tetraphenylporphine complex [14172-90-8] M 671.7. Brown crystals from Et20 or CHCl3-MeOH (cf iron chloride complex). Recrystd by extraction (Soxhlet) with CgHg. Sol in most organic solvents except MeOH and pet ether. [UV, IR J Am Chem Soc 70 1808 7948 81 5111 7959.]... 

Iron (III) meso-5,10,15,20-tetraphenylporphine chloride complex [16456-81-8] M 704.0. Crystallise by extraction from a thimble (Soxhlet) with CHCI3. Concentrate the extract to ca lOmL and add ca 80mL of hot MeOH. Dark blue crystals separate on cooling. It can be recrystallised several times from CHCl3-MeOH. Avoid prolonged heating. It is quite soluble in organic solvents but insoluble in pet ether. [J Am Chem Soc 70 1808 1948 UV 73 4315 7957.]... 

We will perform an AMI calculation on tetraphenylporphin (TPP), pictured at right, in order to examine the four important molecular orbitals for this molecule the second-highest and highest occupied MO s and the lowest and second-lowest unoccupied MO s (which we denote HOMO-1, HOMO, LUMO and LUMO-ll, respectively). 

The Methylene Blue sensitized photoaddition of singlet oxygen to ethyl l//-azepine-l-car-boxylate was reported originally to yield only a C2-C5 adduct 269 however, a reinvestigation with the methyl ester, and using tetraphenylporphine as a sensitizer, revealed that in addition to adduct 46 the [6 + 2] cycloadduct 47 is also produced.270... 

Irradiation of the bis-alkene 210 brings about the formation of the bishomocubane 211 in good yield98. The triene 212 is of interest and has been shown to be photochemically reactive, yielding the adduct 213 on irradiation. Several approaches to 212 have been reported over the years. One such approach follows the path of photocyclization of 214 to yield 215 that can be converted to the desired product 21299. A variety of sensitizers can be used for the excitation of alkenes to bring about the (2 + 2)-cycloaddition. Commonly, acetone has been used but, in at least one case, the formation of the cage compound 216 from the diene 217, tetraphenylporphine has been found to be of use100. 

MI1 55CRV9, p.99). It was later prepared by coupling of 4-isopropyl-p-tropoquinone with 5-hydroxyhinokitiol or by a biomimetic photooxidation of hinokitiol (161) sensitized by tetraphenylporphin (83CL1371). These reactions exemplify the phenol oxidation in troponoid chemistry. 

Reduction of p-oxo-bis[tetraphenylporphin iron(iii)] with sodium amalgam gives several products sequentially. The first reduction product is the radical-anion [(tpp)Fe ] , which has a spin state of - at 77 K and at 300 K. This is the first reported study of an Fe -porphyrin.Mossbauer data on a range of tetra-aryl-substituted iron-porphines and their p-oxo-bridged derivatives have been reported. A crystallographic study on bis(imidazole) otPy -tetraphenylporphinatoiron(iii) chloride-methanol solvate shows the [FeN ] core to be quasitetragonal. An n.m.r. study has been made of the related... 

Table II gives calculated results for copper porphine and experimental values for copper tetraphenylporphine. Results at the non-relativistic limit (c = >) were obtained from the same program by setting the speed of light to a very large number (10 a.u.) ...

Paramagnetic rare-earth porphyrins, TPPErOH (TPP 5,10,15,20-tetraphenylporphin) and TPPEr(dpm) (dpm 2,2,6,6-tetramethyl-3,5-heptanedionate), emit not only but also S2 fluorescence even if a sequence of the... 

We have carried out a comparative study of state fluorescence emitted from several metalloporphyrins Zn -tetraphenylporphin (Zn TPP), Zn - tetrabenzporphin (Zn T6P) and Cd TBP for direct one-quantum excitation and for annihilating two-quantum excitation. Low concentration (C = 1 - 2 X lO- M)... 

S2 - Sq fluorescence and radiationless transitions from the state of porphyrins have been studied in order to reveal photodynaunics of porphyrins. The S2 state fluorescence of zinc(II)-tetraphenylporphin is caused even by the excitation to the state. Two-photon absorption and optical-optical double resonance studies show that a stepwise two-photon absorption through the state is a main process populating the S2 state. 

The absorption cross sections of the Sn Si transition are determined from the kinetic analyses based on the two-photon absorption measurement. In contrast, tetraphenylporphin scarcely show the S2 state fluorescence. In order to elucidate the effect of the imino hydrogens on the radiationless transitions, deuterium isotope effect on the relaxation processes from the lowest excited singlet state of metal free porphyrins has been investigated. 

Recently, it was shown that in deuterated tetraphenylporphin the fluorescence quantum yield and lifetime, and the triplet yield increase in a similar manner relative to the undeuterated one (24). Such a deuterium isotope effects on the state suggested the participation of Sq internal conversion in the energy dissipating... 

Tetraphenylporphin (H2TPP) was prepared from pyrrole and benzaldehyde (25). The tetraphenylchlorin contamination was oxidized by use of 2,3-dichloro-5,6-dicyano-p-benzoquinone (26). Octaethylporphin (H2-OEP)was prepared by the method of Paine et al.(27) from 3,4-diethyl-2-ethoxy-carbony1-5-methyl-pyrrole (28). Zinc(II)-tetraphenylporphin (ZnTPP) was prepared by refluxing H2TPP and zinc acetate in dimethyl-formamide (29). ZnTPP was dissolved at a concentration of 10 -10 ... 

Beside xanthene dyes, methylene blue,127 porphyrins and por-phins,128-130 zinc-tetraphenylporphin,128 a-hydroxyanthraquinones in alkaline alcoholic or pyridine solutions,112,131 vitamin A, /9-carotene, hypericin, rubrene, 3,4-benzpyrene, 20-methylcholanthrene, chlorophyll, and many other compounds have been found to be sensitizers of photooxygenation reactions.70,132,133 Some groups of dyes, however, such as porphyrins and porphins containing transition metals (e.g., Co), azo dyes, cyanine dyes, and triphenylmethane dyes either did not show any or only very poor sensitizer capabilities in the photooxygenation of a-terpinene.128,134... 

Thiophene, diphenylsulfide, diphenyldisulfide, and the disulfides 423 and 424 have been found to be inert in the sulfoxidation reaction.277 However, the production of the sulfoxide 426 from trimethylene disulfide (425) was reported by Calvin and co-workers278 as a result of irradiation of 425 in the presence of oxygen and Zn-tetraphenylporphin. 

The photooxygenation of both (E,E) and ( ,i0 l-aryl-13-pentadienes sensitised by tetraphenylporphine leads almost exclusively to ds-3-aryl-6-methyl-l,2-dioxines. A photo-... 

Pyridines are also well known as ligands in transition metal complexes, and if the equilibrium constants for the formation of such complexes can be related to base strength, it is expected that such constants would follow the Hammett equation. The problem has been reviewed,140 and a parameter S, formulated which is a measure of the contribution of the additional stabilization produced by bond formation to the stabilization constants of complexes expressed in terms of a.141 The Hammett equation has also been applied to pyridine 1 1 complexation with Zn(II), Cd(II), and Hg(II) a,/3,y,<5-tetraphenylporphins,142 143 the a values being taken as measures of cation polarizing ability. Variation of the enthalpy of complexation for adducts of bis(2,4-pentanediono)-Cu(II) with pyridines plotted against a, however, exhibited a curved relationship.144... 

---