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Studies of Porphyrin Metabolism, 3. The Relation of Erythropoiesis to the Excretion of Coproporphyrin by Dogs and Rabbits, and to the Concentration of Coproporphyrin and Protoporphyrin in Rabbit Erythrocytes

Description: Report discussing studies regarding porphyrin excretion and hemoglobin metabolism in animals with phenylhydrazine anemia, and studies regarding the coproporphyrin and protoporphyrin in the red blood cells of rabbits.
Date: November 25, 1945
Creator: Schwartz, Samuel; Glickman, Marcia; Hunter, Rosie & Wallace, Jean
Partner: UNT Libraries Government Documents Department

Singlet Quenching of Tetraphenylporphyrin and its Metal Derivatives by Iron(III) Coordination Compounds

Description: This article reports on the singlet quenching of 5, 10, 15, 20-tetraphenylporphyrin (H₂TPP) and its magnesium(II) and zinc(II) derivatives (MgTPP and ZnTPP) by a series of iron(III) coordination compounds bearing different ligand systems.
Date: January 6, 1990
Creator: D'Souza, Francis & Krishnan, V.
Partner: UNT College of Arts and Sciences

Supramolecular Solar Cells

Description: Supramolecular chemistry - chemistry of non-covalent bonds including different type of intermolecular interactions viz., ion-pairing, ion-dipole, dipole-dipole, hydrogen bonding, cation-p and Van der Waals forces. Applications based on supramolecular concepts for developing catalysts, molecular wires, rectifiers, photochemical sensors have been evolved during recent years. Mimicking natural photosynthesis to build energy harvesting devices has become important for generating energy and solar fuels that could be stored for future use. In this dissertation, supramolecular chemistry is being explored for creating light energy harvesting devices. Photosensitization of semiconductor metal oxide nanoparticles, such as titanium dioxide (TiO2) and tin oxide (SnO2,), via host-guest binding approach has been explored. In the first part, self-assembly of different porphyrin macrocyclic compounds on TiO2 layer using axial coordination approach is explored. Supramolecular dye sensitized solar cells built based on this approach exhibited Incident Photon Conversion Efficiency (IPCE) of 36% for a porphyrin-ferrocene dyad. In the second part, surface modification of SnO2 with water soluble porphyrins and phthalocyanine resulted in successful self-assembly of dimers on SnO2 surface. IPCE more than 50% from 400 - 700 nm is achieved for the supramolecular self-assembled heterodimer photocells is achieved. In summary, the axial ligation and ion-pairing method used as supramolecular tools to build photocells, exhibited highest quantum efficiency of light energy conversion with panchromatic spectral coverage. The reported findings could be applied to create interacting molecular systems for next generation of efficient solar energy harvesting devices.
Date: August 2012
Creator: Subbaiyan, Navaneetha Krishnan
Partner: UNT Libraries

Conformational Diversity in (Octaethylporphinato) (trichloroacetato)iron(III) Derivatives

Description: Treatment of [Fe(OEP)]20 with trichloroacetic acid results in ruffled formation of (octaethylporphinato trichloroacetato)iron(HI). Various crystalline solvates can be isolated, depending on the crystallization solvent. Initial crystallization with CHC13/hexanes resulted in the isolation of an unsolvated form. [Fe(OEP)(02C2C13 )]. This form contains distinct porphyrin core conformations at the same site: one is domed and the other is ruffled. Crystal data for [Fe(OEP)(02C2C13 )]: Q = 14.734(4) .4. b = 13.674(1) .\. c = 17..541 [,.5] .~. 3 = 90.67(1)0, V = 35-!5.8(14) .\3. monoclinic. space group R1/ n. Z = 4. Subsequent crystallization with CHC13/hexanes resulted in a new crystalline form, [Fe(OEP)(OzC2C13 )~.- CHC13; the porphyrin core is slightly ruffled. Crystal data for [Fe(OEP)(OoC2C13 )]. CHC13: a =12.323(1) .~, 6 = 13.062(3) .\. C = 14.327(2) .$, Q = 89.32(1)", .3 = 113.36(2)0. :~ = 105.26(1)'. V = `2031.3(6) .\3. triclinic. space group Pi. Z = 2. Crystallization with CH2C12/hexanes resulted in the isolation of yet another form, [Fe(OEP) (02 C2C13)]. H02C2C13. which contains two independent molecules in the unit cell: molecule is slightly saddled and molecule B is modestly ruffled. Crystal data for [Fe(OEP)(02ClC13 )]. H02C2C13: a = 13.148(3) .\, b = 13.45.5(3) A, c = Q3.761(5) -& ~ = 90.72(3)", ~ = 91. ~4(3)". -y = 92.36(3)0, V = 4198.5(15) .\3, triclinic.space group PI, Z = 4. .+11 conformations form dimers in the solid state. Temperature-dependent manometic susceptibility measurements showed that [Fe(OEP)(02C2C13)] .CHC13 contains a high-spin iron(III) center; the data for {Fe(OEP)(02C2C13 )l.H02C2C13 are understood in terms of an admixed intermediate-spin state (S = 3/2, 5/2) and are readily fit to a faltempo model with a ground state multiplet containing about 78% S = 5/2 character and 22% S = 3/2 character. The structural data for [Fe(OEP)(02C2C13 )]. CHC13 are consistent with the observed high-spin state, while data for ...
Date: October 19, 1998
Creator: Cheng, B.; Ma, J.; Neal, T.J.; Scheidt, W.R.; Schulz, C.E. & Shelnutt, J.A.
Partner: UNT Libraries Government Documents Department

Molecular Simulations of Porphyrins and Heme Proteins

Description: An overview of the use of classical mechanical molecular simulations of porphyrins, hydroporphyrins, and heme proteins is given. The topics cover molecular mechanics calculations of structures and conformer energies of porphyrins, energies of barriers for interconversion between stable conformers, molecular dynamics of porphyrins and heme proteins, and normal-coordinate structural analysis of experimental and calculated porphyrin structures. Molecular mechanics and dynamics are currently a fertile area of research on porphyrins. In the future, other computational methods such as Monte Carlo simulations, which have yet to be applied to porphyrins, will come into use and open new avenues of research into molecular simulations of porphyrins.
Date: January 18, 2000
Partner: UNT Libraries Government Documents Department

Porphyrin Interactions with Wild Type and Mutant Mouse Ferrochelatase

Description: Ferrochelatase (EC, the terminal enzyme of the heme biosynthetic pathway, catalyzes Fe<sup>2+</sup> chelation into protoporphyrin IX. Resonance Raman and W-visible absorbance spectroscopes of wild type and engineered variants of murine ferrochelatase were used to examine the proposed structural mechanism for iron insertion into protoporphyrin by ferrochelatase. The recombinant variants (i.e., H207N and E287Q) are enzymes in which the conserved amino acids histidine-207 and glutamate-287 of murine ferrochelatase were substituted with asparagine and glutamine, respectively. Both of these residues are at the active site of the enzyme as deduced from the Bacillus subtilis ferrochelatase three-dimensional structure. Addition of free base or metalated porphyrins to wild type ferrochelatase and H207N variant yields a quasi 1:1 complex, possibly a monomeric protein-bound species. In contrast, the addition of porphyrin (either free base or metalated) to E287Q is sub-stoichiometric, as this variant retains bound porphyrin in the active site during isolation and purification. The specificity of porphyrin binding is confirmed by the narrowing of the structure-sensitive resonance Raman lines and the vinyl vibrational mode. Resonance Raman spectra of free base and metalated porphyrins bound to the wild type ferrochelatase indicate a nonplanar distortion of the porphyrin macrocycle, although the magnitude of the distortion cannot be determined without first defining the specific type of deformation. Significantly, the extent of the nonplanar distortion varies in the case of H207N- and E287Q-bound porphyrins. In fact, resonance Raman spectral decomposition indicates a homogeneous ruffled distortion for the nickel protoporphyrin bound to the wild type ferrochelatase, whereas both a planar and ruffled conformations are present for the H207N-bound porphyrin. Perhaps more revealing is the unusual resonance , 3 Raman spectrum of the endogenous E287Q-bound porphyrin, which has the structure-sensitive lines greatly upshifted relative to those of the free base protoporphyrin in solution. This could be interpreted as an equilibrium ...
Date: May 19, 1999
Creator: Ferreira, Gloria C.; Franco, Ricardo; Lu, Yi; Ma, Jian-Guo & Shelnutt, John A.
Partner: UNT Libraries Government Documents Department

Novel Dodecaarylporphyrins: Synthesis and Variable Temperature NMR Studies

Description: An investigation of the synthesis of novel dodecaarylporphyrins using the Suzuki coupling reaction of arylboronic acids with octabromotetraarylporphyrins is reported. Studies of the dynamic properties of these new porphyrins using variable temperature (VT) <SUP>1</SUP>H NMR spectroscopy and molecular mechanics provide interesting insights into their dynamic properties, including the first determination of {beta} aryl rotation in a porphyrin system.
Date: May 5, 1999
Creator: Cancilla, Mark; Lebrilla, Carlito; Ma, Jian-Guo; Medforth, Craig J.; Muzzi, Cinzia M.; Shelnutt, John A. et al.
Partner: UNT Libraries Government Documents Department

Synthesis and Characterization of a New Perhalogenated Porphyrin

Description: The first synthesis of an octahalotetraalkylporphyrin [2,3,7,8,12,13,17,18 -octabromo-5,10,15,20- tetrakis(trifluoromethyl)porphinato nickel(II)] is reported; this perhalogenated porphyrin has several novel properties including a very nonplanar ruffled structure with an unusually short Ni- N distance, an extremely red-shifted optical spectrum, and hindered rotation of the trifluoromethyl groups ({Delta}G<sub>278K</sub> =47 kJ mol<sup>-1</sup>).
Date: May 19, 1999
Creator: Jia, Songling; Medforth, Craig J.; Nelson, Nora Y.; Nurco, Daniel J.; Shelnutt, John & Smith, Kevin M.
Partner: UNT Libraries Government Documents Department

Fluorinated Dodecaphenylporphyrins: Synthetic and Electrochemical Studies Including the First Evidence of Intramolecular Electron Transfer Between an Fe(II) Porphyrin -Anion Radical and an Fe(I) Porphyrin

Description: Dodecaphenylporphyrins with varying degrees of fluorination of the peripheral phenyl rings (FXDPPS) were synthesized as model compounds for studying electronic effects in nonplan~ porphyrins, and detailed electrochemical studies of the chloroiron(HI) complexes of these compounds were undertaken. The series of porphyrins, represented as FeDPPCl and as FeFXDPPCl where x = 4, 8 (two isomers), 12, 20,28 or 36, could be reversibly oxidized by two electrons in dichloromethane to give n-cation radicals and n-dications. All of the compounds investigated could also be reduced by three electrons in benzonitrile or pyridine. In benzonitrile, three reversible reductions were observed for the unfluorinated compound FeDPPC1, whereas the FeFXDPPCl complexes generally exhibited irreversible first and second reductions which were coupled to chemical reactions. The chemical reaction associated with the first reduction involved a loss of the chloride ion after generation of Fe FXDPPC1. The second chemical reaction involved a novel intramolecular electron transfer between the initially generated Fe(H) porphyrin n-anion radical and the final Fe(I) porphyrin reduction product. In pyridine, three reversible one electron reductions were observed with the second reduction affording stable Fe(II) porphyrin o - anion radicals for ail of the complexes investigated.
Date: October 19, 1998
Creator: D'Souza, F.; Forsyth, T.P.; Fukuzumi, S.; Kadish, K.M.; Krattinger, B.; Lin, M. et al.
Partner: UNT Libraries Government Documents Department

Redox Reactions of Metalloporphyrins and their Role in Catalyzed Reduction of Carbon Dioxide

Description: Pulse radiolysis and laser photolysis are used to study redox processes of metalloporphyrins and related complexes in order to evaluate these light absorbing molecules as sensitizers and intermediates in solar energy conversion schemes. The main thrust of the current studies is to investigate the role of reduced metalloporphyrins as intermediates in the catalyzed reduction of carbon dioxide. Studies involve cobalt and iron porphyrins, phthalocyanines, corroles, and corrins as homogeneous catalysts for reduction of carbon dioxide in solution. The main aim is to understand the mechanisms of these photochemical schemes in order to facilitate their potential utilization.
Date: September 1, 2002
Creator: Neta, P.
Partner: UNT Libraries Government Documents Department

Structural mechanisms of nonplanar hemes in proteins

Description: The objective is to assess the occurrence of nonplanar distortions of hemes and other tetrapyrroles in proteins and to determine the biological function of these distortions. Recently, these distortions were found by us to be conserved among proteins belonging to a functional class. Conservation of the conformation of the heme indicates a possible functional role. Researchers have suggested possible mechanisms by which heme distortions might influence biological properties; however, no heme distortion has yet been shown conclusively to participate in a structural mechanism of hemoprotein function. The specific aims of the proposed work are: (1) to characterize and quantify the distortions of the hemes in all of the more than 300 hemoprotein X-ray crystal structures in terms of displacements along the lowest-frequency normal coordinates, (2) to determine the structural features of the protein component that generate and control these nonplanar distortions by using spectroscopic studies and molecular-mechanics calculations for the native proteins, their mutants and heme-peptide fragments, and model porphyrins, (3) to determine spectroscopic markers for the various types of distortion, and, finally, (4) to discover the functional significance of the nonplanar distortions by correlating function with porphyrin conformation for proteins and model porphyrins.
Date: May 1, 1997
Creator: Shelnutt, J.A.
Partner: UNT Libraries Government Documents Department

Molecular structure determination for photogenerated intermediates in photoinduced electron transfer reactions using steady-state and transient XAFS

Description: Many photoinduced electron transfer reactions are accompanied by nuclear rearrangements of the molecules involved. In order to understand the reactivities of the molecules and the reaction mechanisms, precise information on the molecular structural changes accompanying the electron transfer is often required. We present here conventional XAFS and transient energy dispersive XAFS studies on structures of excited and photoinduced charge separated state of porphyrin and porphyrin based supermolecules, and structures of TiO{sub 2} colloid and the heavymetal ions that bind to the colloid surfaces during photocatalytic reductions.
Date: October 1, 1996
Creator: Chen, L.X.; Wasielewski, M.R. & Rajh, T.
Partner: UNT Libraries Government Documents Department

Novel metalloporphyrin catalysts for the oxidation of hydrocarbons

Description: Work was done for developing biomimetic oxidation catalysts. Two classes of metalloporphyrin catalysts were studied. The first class of catalysts studied were a novel series of highly substituted metalloporphyrins, the fluorinated iron dodecaphenylporphyrins. These homogeneous metalloporphyrin catalysts were screened for activity as catalysts in the oxidation of hydrocarbons by dioxygen. Results are discussed with respect to catalyst structural features. The second type of catalysts studied were heterogeneous catalysts consisting of metalloporphyrins applied to inorganic supports. Preliminary catalytic testing results with these materials are presented.
Date: November 1, 1996
Creator: Showalter, M.C.; Nenoff, T.M. & Shelnutt, J.A.
Partner: UNT Libraries Government Documents Department

Catalytic conversion of light alkanes-proof-of-concept stage - Phase IV. Topical report, February 1, 1994--January 31, 1995

Description: This report details the research performed on Phase IV of the extended Cooperative Agreement. This Phase, entitled C{sub 1}-C{sub 4} Research, provides the research support which accompanies the C{sub 4} Proof-of-Concept Phase (Phase V) as the two major activities of the Cooperative Agreement during calendar 1993. It is the objective of this phase to understand the nature of the catalysts and catalytic activity of perhaloporphyrin complexes uncovered during Phases I-III in order that superior catalytic materials can be made and tested which meet commercial criteria for the oxidation of the C{sub 1}-C{sub 4} light alkane gases found in natural gas and other available hydrocarbon streams. During Phase IV, we have examined the physical and electronic structures of the very active perhaloporphyrin catalysts which we have developed, and have gained an understanding of the properties which make them active. This has led us to design and synthesize materials which are cheaper, more active, more robust and, in general superior for carrying out practical catalysis. Our early generation perhaloporphyrin catalysts, while exhibiting unprecedented catalytic activity, were far too expensive for use in converting natural gas or its C{sub 1}-C{sub 4} components.
Date: December 31, 1998
Partner: UNT Libraries Government Documents Department

A nonplanar porphyrin-based receptor molecule for chiral amine ligands

Description: A novel porphyrin-based receptor molecule for chiral amine ligands is described in which nonplanarity of the porphyrin macrocycle is used to orient the ligand and to enhance porphyrin-ligand interactions. The porphyrin macrocycle provides a versatile platform upon which to build elaborate superstructures, and this feature coupled with a rich and well-developed synthetic chemistry has led to the synthesis of many elegant models of heme protein active sites and numerous porphyrin-based receptor molecules. One design feature which is not usually considered in the design of porphyrin-based receptor molecules is nonplanarity of the porphyrin ring, although there are a few systems such as the pyridine sensitive Venus Flytrap and the chirality-memory molecule which illustrate that nonplanar porphyrin-based receptors can display unique and interesting behavior. Given the novel properties of these receptors and the continuing interest in the effects of nonplanarity on the properties of porphyrins the authors decided to investigate in more detail the potential applications of nonplanarity in the design of porphyrin-based receptors. Herein, they describe the design, synthesis, and characterization of a new kind of nonplanar porphyrin-based receptor molecule for chiral amines.
Date: March 6, 2000
Partner: UNT Libraries Government Documents Department

Normal-Coordinate Structural Decomposition and the Vibronic Spectra of Porphyrins

Description: The connection is made between the normal-coordinate structural decomposition (NSD) and the vibronic molecular states and spectra of porphyrins. NSD is a procedure that provides a description of the distortion of a porphyrin from a D{sub 4h} symmetric reference structure in terms of equivalent displacements along the normal coordinates. Expressions for the optical absorption spectra with vibrational structure are developed with these NSD-determined deformations as parameters, and the expressions are applied to the UV-visible absorption spectra porphyrins.
Date: November 9, 1999
Partner: UNT Libraries Government Documents Department

Nonplanarity and the protonation behavior of porphyrins

Description: {sup 1}H NMR studies of the protonation of highly nonplanar porphyrins with strong acids reveal the presence of the previously elusive monocation, and show that its stability can be related to the amount of saddle distortion induced by protonation; the amount of saddle distortion for a porphyrin dication is also found to correlate well with the rate of intermolecular proton transfer.
Date: March 21, 2000
Partner: UNT Libraries Government Documents Department

Structure-function relationships of second hyperpolarizabilities in two-dimensional molecules

Description: The enhancement of the third order susceptibilities X{sup (3)} and second order molecular hyperpolarizabilities <{gamma}> in a series of covalently stacked dimer and trimer macrocycles (SiPc and SiNc) was observed through the phase conjugated signals from DFWM measurements at both 1064 and 532 nm. The FWHM of the phase conjugated signals at 532 nm is much smaller than those at 1064 nm and those of the reference compound CS{sub 2}. The <{gamma}> values at both wavelengths as a function of number of the monomer units (n) have an approximate n{sup 3} dependence, differing only in the scaling constant. The origin of such enhancement is discussed and compared to those in one-dimensional {pi}-conjugated systems.
Date: July 1, 1995
Creator: Chen, L.X.; Mandal, B.K. & Bihari, B.
Partner: UNT Libraries Government Documents Department

Catalytic conversion of light alkanes -- research and proof-of-concept stages

Description: Objective is to find new catalysts for direct reaction of methane, ethane, propane, butanes with O{sub 2} to form alcohols, and to develop practical processes for direct oxidative conversion of natural gas and its C{sub 1}-C{sub 4} components to produce alcohol-rich liquid oxygenates for use as alternative transportation fuels/environmentally superior reformulated gasolines. The proposed mechanism for oxidation activity of cytochrome P-450 and methane monoxygenase suggested that a catalyst able to reductively bind oxygen, not between Fe(III) center and a proton, but between two Fe(III) centers, might give the desired dioxygenase activity for alkane hydroxylation. Selective oxidation of light alkanes could be done by oxidation-active metal (Fe) centers in electron-deficient prophyrin-like macrocycles, polyoxoanions, and zeolites. In the isobutane conversion to tert-butanol proof-of-concept, it was found that nitro groups on the periphery of Fe porphyrin complexes give the greatest increase in Fe(III)/(II) reduction potential. 8 figs, 6 tabs, 40 refs.
Date: December 31, 1993
Creator: Lyons, J. E. & Hancock, A. W. II
Partner: UNT Libraries Government Documents Department

Nonlinear optical properties of porphyrin and chlorophyll dimers studied by degenerated four wave mixing

Description: As one of the important elements in natural and artificial electron transfer and energy transfer processes, porphyrin and its derivatives have received much attention in photoelectronics and photoelectronic materials. As our first attempt to relate the {pi}-{pi} electronic couplings between porphyrin macrocycles to apparent third order nonlinear susceptibilities, we measured {chi}({sup 3}) for several porphyrin and chlorophyll a derivatives, including dimers with different configurations. Our preliminary results show that the dimers have enhanced {chi}({sup 3}) compared to those of the monomer. This enhancement is related to the relative orientations between the two macrocycles in the dimers. The parallel dimers with close face-to-face distances seem to have the highest enhancement in {chi}({sup 3}). Thus, we believe that {chi}({sup 3}) is strongly related to the {pi}-{pi} electronic coupling between the two conjugated ring systems.
Date: December 31, 1992
Creator: Chen, L. X. Q.
Partner: UNT Libraries Government Documents Department


Description: The solution photochemistry of chlorophyll and chlorophyll analogs is described. Many cases of electron transfer to or from the porphyrin macrocycle have been found, but in no case has any very large degree of energy storage been achieved. Because of the very rapid back-reaction for products with a {Delta}F of approximately -30 kcal, some solid state models in which such an energy storage might be achieved are described and their possible relation to the natural photosynthetic apparatus is given. We can see that while the solid state model (phthalocyanine) allows an approach from a somewhat different point of view, the net result is the same as what was sought, but so far not found, when we looked at the solution chemistry of chlorophyll (and chlorophyll model substances), namely, the transfer of an electron, or hydrogen atom, from the excited porphyrin to an electron acceptor at a high reduction level which can be used to reduce the ultimate carbon dioxide reducers, followed by the donation of an electron ultimately from water to the remaining radical ion, or lattice, which produces the net results of the transfer of the hydrogen from water to carbon dioxide.
Date: April 11, 1960
Creator: Calvin, Melvin
Partner: UNT Libraries Government Documents Department