Physical Sciences and Mathematics Commons^™

Synthesis And Characterization Of Indole-Based Zinc Dipyrrin Photosensitizers, Jean-Pierre Sanza

Electronic Theses and Dissertations

Metal complexes of dipyrromethene (dipyrrins) used as sensitizers in photocatalysis offer a way to harness solar energy in chemical bonds to create new fuels. This offers the dual role of reducing fossil fuel dependence and atmospheric CO₂ levels. Traditionally, metal dipyrrin complexes are synthesized using substituted pyrroles, aldehydes, and transition metals. Indoles have a more expanded pi-electron system and their dipyrrin-type complex may exhibit visible light absorption, suggesting that they can act as photosensitizers for CO₂ reduction processes. A novel indoledipyrromethene was synthesized using unsubstituted indole and mesitaldehyde. The complex exhibits visible light absorption at 422 nm. Its …

Investigating The Role Of Charge Separation In Triplet State Formation In Zinc Dipyrrin Photosensitizers, Irene Y. Dzaye

Electronic Theses and Dissertations

About 85% of the world’s energy is derived from non-renewable sources—coal, petroleum, and natural gas. Solar photocatalysis is one way to potentially generate cheap renewable fuels by harnessing energy from the sun using a photosensitizer and converting it into chemical energy. The efficiency of a photosensitizer depends on its capacity to form a prolonged triplet excited state. Zinc dipyrrin complexes have the potential to be efficient sensitizers for reductive photochemistry, but their ability to form long-lived triplet excited states still needs extensive research. The overall aim of this research is to probe the role charge separation plays in the formation …

Development Of Granulated Adsorbent For Clean-Up Of Water Contaminated By Cesium, Esther Alorkpa

Electronic Theses and Dissertations

A study was conducted on sol-gel synthesis of an adsorbent (phosphotungstic acid embedded in silica gel, H-PTA/SiO­₂) of radioactive cesium. A novelty of this work is covalent bonding of PTA to the surface of solid support that prevents leaching from the surface of the material. The sample was granulated with a binder, aluminium oxide (γ-Al₂O₃). Solid-state NMR and FT-IR spectroscopy were used to confirm the presence of Keggin units of PTA in the bound materials. Thermal analysis of H-PTA/SiO­₂ - γ-Al₂O₃ (50 %) showed that the water content in the …

Synthesis And Characterization Of Zinc(Ii) Dipyrrin Photosensitizers, Norah Alqahtani

Electronic Theses and Dissertations

Photocatalytic carbon dioxide reduction transforms CO2 to useful chemicals and fuels, reducing CO2 emissions and making fossil fuels more renewable. Due to a lack of earthabundant sensitizers, we want to design new earth-abundant sensitizers to go with the many known carbon dioxide reduction catalysts. Zn(II) dipyrrin complexes strongly absorb visible light, but their excited state properties have not been widely studied. To investigate their photophysical properties, two Zn dipyrrin complexes, with and without heavy atoms, were synthesized and characterized by NMR and mass spectrometry. The photophysical properties of the two complexes were measured in polar and non-polar solvents, particularly fluorescence …

Functionalized Silica Gel For Adsorption Of Cesium From Solution, Kenneth Marshall Seaton Iii

Electronic Theses and Dissertations

Mesoporous silica gel containing embedded phosphotungstic acid (PTA) was synthesized by sol-gel co-condensation of tetraethyl orthosilicate with PTA in acidic media. The obtained material had high Brunauer-Emmett-Teller Theory (BET) surface area and pore volume. A characteristic band of the Keggin structure of PTA was present in its FT-IR spectrum while its X-ray diffraction patterns were absent. This proved the embedding of PTA on a sub-molecular level and not as a second phase. Acidic sites were determined by neutralization with base in aprotic solvent, followed by titration of the remaining base with an acid. The material demonstrated high adsorption capacity of …

Synthesis And Characterization Of Imidazolo 3,1- Tetrakis (N-Phenylacetamidato) Dirhodium (Ii) And A Crystallographic Study Of A Copper And Two Molybdenum Model Cofactors, Gabriel I.G. Thompson

Electronic Theses and Dissertations

Imidazole was reacted with 3,1-tetrakis (N-phenlyacetamidato) dirhodium (II) to explore the chemistry of asymmetric dirhodium catalysts. The imidazolo 3,1-tetrakis (Nphenlyacetamidato) dirhodium (II) complex was synthesized and then characterized by Nuclear Magnetic Resonance and Ultraviolet-Visible spectroscopies as well as by single crystal X-ray Diffraction. Additionally, one copper and two molybdenum model cofactors were characterized by XRD to better understand their structure/function relationships. NMR results gave evidence of the formation of the 3,1-imidazole complex, and UV-Vis indicated that even in large excess imidazole was coordinated only to one axial site. The structure of the 3,1-imidazole complex was confirmed by XRD with the …

Synthesis And Characterization Of Five New Tetrakis(N-Phenylacetamidato) Dirhodium(Ii) Amine Complexes And One Molybdenum Cofactor Described Crystallographically, Cragin K. Harris

Electronic Theses and Dissertations

Six new crystal structures were determined using a Rigaku Mercurcy 375/MCCD(XtaLab mini) diffractometer. The structure of a molybdenum cofactor was solved resulting in an R1 (R1 = Σ ||Fo| - |Fc|| / Σ |Fo|) of 3.61% despite the presence of a disordered DMSO molecule. New Tetrakis(N-phenylacetamidato) Dirhodium(II) complexes were synthesized and characterized. Two 2,2-cis-[Rh2(NPhCOCH3)4]•(C3H4N2)x where x= 1 or 2 were successfully crystallized and solved with R1 values below 5%. Additional studies were conducted via NMR to observe formation of both products. Three potential catalysts were synthesized starting with 3,1-[Rh₂(NPhCOCH₃)₄]. The resulting compounds were a …

Synthesis And Characterization Of 2,2-Cis-[Rh2(Nphcoch3)4]•Ncc6h4r Where R = H, 2-Ch3, 3-Ch3, 4-Ch3 And [Rh2(O2cch3)(Nphcocf3)3], Fredricka F. Quarshie

Electronic Theses and Dissertations

Five novel compounds were synthesized and characterized. Crystal structures were determined using Rigaku Mercury 375/MCCD(XtaLAB mini) diffractometer with graphite monochromated MoKα radiation. The crystal structures of [Rh₂(NPhCOCH₃)₄•xNCC₆H₄R where x = 1 or 2 and R=H, 2-CH₃,3-CH₃ and 4-CH₃ were solved to an R₁ value of less than 5 (R₁= Σ||F_o| - |F_c|| / Σ |F_o|). In each of the nitrile complexes, the rhodium is five or six coordinate and possesses pseudo D_4h symmetry. The complexes were …

Synthesis And Characterization Of Three New Tetrakis(N-Phenylacetamidato) Dirhodium(Ii) Nitrile Complexes, Nkongho Atem-Tambe

Electronic Theses and Dissertations

Three new tetrakis [Rh₂(PhNCOCH₃)₄·xNCR] (R = {2-CH₃}C₆H₄ (x=2), R = {3-CH₃}C₆H₄ (x=1), R = (3-CN)C₆H_4∞ (x=1)) complexes have been synthesized and characterized. These complexes were characterized by IR and ¹H NMR spectroscopies and X-ray crystallography which solved with R₁<0.05.

[Rh₂(PhNCOCH₃)₄·2NC{2-CH₃}C₆H₄] was triclinic (a=9.79Å, b=14.79Å, c=16.36Å, α=103.84⁰, β=99.17⁰, γ=99.77⁰, P-1(#2), μCN=2227.78cm^-1, Rh-Rh=2.42Å, N-C=1.13Å, 1.14Å, Rh-N=2.34Å, 2.35Å, Rh-N-C=151.6⁰, 152.5⁰, Rh-Rh-N=173.0⁰, 174.6⁰).

[Rh₂(PhNCOCH₃)_{4 …}

Synthesis And Characterization Of A New Cyano-Substituted Tris(Pyrazolyl)Borate And Its Thallium(I) Complex, Bozumeh Som

Electronic Theses and Dissertations

A new cyanoscorpionate - tris(4-cyano-3,5-diphenylpyrazolyl)borate (Tp^Ph2,4CN) has been synthesized and characterized. The thallium complex of this ligand TlTp^Ph2,4CN has also been prepared and characterized by FT-IR, ¹H NMR, and single-crystal X-ray-diffraction. The complex TlTp^Ph2,4CN crystalized in the monoclinic space group C2/c with unit cell a = 14.6697(10) Å, b = 13.9493(10) Å, c = 19.3347(12) Å, and b= 91.761(2)°. Structural comparison of TlTp^Ph2,4CN with analogous complexes demonstrated the effects of both steric and electron-withdrawing substituents on coordination geometry and the electronic properties of the metal ion. There were short contacts between the cyano groups …

X-Ray Crystal Structures Of: [Rh2(N-{2,4,6-Ch3}C6h2)Coch3)4]•2ncc6h4 And Ba1.5[Fe(C10h13n2o7)][Co(Cn)6]•9h2o; Two Crystallographic Challenges, Kenneth K. Kpogo

Electronic Theses and Dissertations

The novel compound, [Rh₂(N-{2,4,6-CH₃}C₆H₂)COCH₃)₄] was synthesized. Crystal structures of [Rh₂(N-{2,4,6-CH₃}C₆H₂)COCH₃)₄]·2NCC₆H₅ and Ba_1.5[Fe(C₁₀H₁₃N₂O₇)][Co(CN)₆]·9H₂O were determined employing a Rigaku Mercury375R/M CCD (XtaLAB mini) diffractometer with graphite monochromated Mo-Kα radiation. For [Rh₂(N-{2,4,6-CH₃}C₆H₂)COCH₃)₄]·2NCC₆H₅, the space group was P-421c(#114) with unit cell dimensions: a =11.0169(14)Å, c =21.499(3)Å, V …

Quenching Of The Fluorescence Of Tris (2 2-Bipyridine) Ruthenium(Ii) [Ru(Bipy)3]2+ By A Dimeric Copper(Ii) Complex., Kevin E. Cummins

Electronic Theses and Dissertations

The quenching of the [Ru(bipy)₃]²⁺ by Cu₂L²⁺ was studied and the data were plotted with the Stern-Volmer equation. The plot showed a break and was divided into 2 regions, <0.5 and >0.5 Cu₂L²⁺: [Ru(bipy)₃]²⁺ molar ratio. Quenching above the 0.5 Cu₂L²⁺: [Ru(bipy)₃]²⁺ molar ratio was slower (330 x 10^-6 M^-1s^-1) than the quenching rate reaction below 0.5 ratio (387 x 10^-6 M^-1s^-1).

With Cu₂L²⁺ being a dimeric complex the …

Cyanoscorpionates And Transition Metal Complexes., Donald Martin Johnson

Electronic Theses and Dissertations

The new dihydrobis(4-cyano-3-tert-butylpyrazolylborate) ligand has been synthesized. Isolated crystals of the thallium complex were collected and structurally characterized by X-ray diffraction. Transition metal complexes of the ligand are currently under investigation.