Chemistry Commons^™

Allosteric Tuning Of Ruthenium 2,2’-Bipyridyl Luminescent Sensor Systems, Daqing Gan

Masters Theses

A series of new ruthenium bipyridyl crown supramolecular sensor systems containing two binding sites were synthesized. The crystal structure and photophysical properties of the developed sensor systems were thoroughly studied using x-ray, nuclear magnetic resonance and photoscopy methods. It turned out that the chelation of transition metal on the remote sites of the bipyridyl crown ligands greatly reduced the reactivity of the crown cavity. It is believed that the chelation of transition metal on the nitrogen atoms forces the bipyridyl function towards coplanarity and restricts the conformational freedom of the crown ring. The conformational rigidity in turn influences the binding …

Photophysical Study Of Linked 1,4,7-Triazacyclonane Cr (Iii) Complexes, Weizhen Tu

Masters Theses

A series of mono and bimetallic Cr(III) complexes based on the 1,4,7- triazacyclonoane(TACN) were prepared. Complexes of the Cr(TACN)X₃ , and Cr₂(DTNE)X₆ demonstrated marked difference of photophysical properties on the nature of X. In cases where X is more easily oxidized, enhanced extinction coefficient in the ⁴A₂ ➔ ²T, absorption and larger quantum yield of emission at 77K were observed in the dimer complexes. Shorter lifetime and enhanced decay rate were also found in the dimer complexes suggests that there might exists weak coupling behavior between the two Cr(III) metal cents in the …

Reaction Of Caffeic Acid With Amino Acids, Yonggang Wang

Masters Theses

The reaction of caffeic acid with tryptophan was studied as a model for the reaction of caffeic acid with amino acids in the aquatic environment. Although the autoxidation reaction of caffeic acid in aqueous solution with subsequent dimerization had been previously studied, it was examined as well for comparison purposes. The present studies demonstrate that oxidized caffeic acid would react with tryptophan. The reaction, like the dimerization reaction, was catalyzed by the presence of iron(III) ions at low pH ( <4) and by hydroxide ions at high pH (10). The reaction of caffeic acid with itself yielded six products, four of which were identified by mass spectroscopy as dimers, with the other two being trimers. The reaction of caffeic acid with tryptophan yielded three product peaks. Two of the product peaks had similar retention times to the dimers from the self-reaction of caffeic acid; the third was a new product resulting from the reaction of caffeic acid with the tryptophan.

A mechanism for the reaction of caffeic acid with tryptophan has been proposed. This mechanism was based on the analysis …

Photodegradation Of Pcbs In Natural Waters, Adriana R. Nicolaescu

Masters Theses

PCBs are widely distributed in the environment and they are biologically refractory and toxic compounds. There is great interest in understanding their fate in the environment, and also for finding safe and effective degradation methods.

This study is concerned with the photodegradation of four PCB congeners: PCB 5, PCB 18, PCB 77, PCB 128 in natural waters. Natural waters contain humic substances which can greatly influence the environmental fate of the PCBs. The different degradation of the four congeners was studied in standardized systems and in humic acid or nitrate solutions, under environmental conditions. DMDE and Methoxyclor (whose environmental half-lifetimes …

Equilibrium And Kinetic Studies Of Isomerization Of (Co)5w[Η1-Pph2ch2p(P-Tol)2] And (Co)5w[Η1-P(P-Tol)2ch2pph2], Deliang Chen

Masters Theses

Unsymmetrical diphosphine tungsten complexes, (CO)₅W[η¹-PPh₂CH₂P(p-tol)₂] and (CO)₅W[η¹-P(p-tol)₂CH₂PPh₂], were prepared from (CO)₅W(NH₂Ph) and Ph₂PCH₂P(p-tol)₂. Two approaches were successfully used to synthesize Ph₂PCH₂P(p-tol)₂. The first utilized PPh₂CH₂Cl, prepared from PPh₂H, CH₂Cl₂, and KOH under phase transfer conditions, from which Ph₂PCH₂P(p-tol)₂ was …

A Time Resolved Laser Spectroscopy Study Of Resonance Energy Transfer Between Tb(Iii) And An Organic Dye: 6-Hydroxy-5-[(2-Methoxy-5-Methyl-4-Sulfophenyl)Azo]-2-Naphthalenesulfonic Acid Disodium Salt, Ronald Wesley Tennis

Masters Theses

Intermolecular energy transfer is a process of crucial importance to photochemistry and photophysics. Complexed lanthanide ions are well suited as energy transfer donors because they display dependable absorption and luminescence qualities with narrow rare-earthion emission in addition to relatively long excited-state lifetimes.

This project used a pulsed nitrogen laser and high speed digital techniques to study energy transfer dynamics between excited state Tb(acac)₃ and an ionic organic dye called Red 40. Luminescence decay profiles of excited terbium atoms in the presence of the quencher were measured in both high and low viscosity solvents. The effects of solvent viscosity and …

Investigations Into The Synthesis And Transformations Of An Epoxy Β-Lactone, John Farrell

Masters Theses

In connection with the continuing interests in the stereoselective rearrangements of β-lactones, an investigation of the synthesis and transformations of the epoxy β-lactone 4-(1,2-epoxypentyl)-3-trimethylsilyloxetan-2-one was undertaken. Two synthetic strategies to the desired epoxy β-lactone were studied. The first route was a two-step reaction sequence involving the aldol reaction of trimethylsilylacetic acid with (2R,3S)-epoxyhexanal, followed by lactonization of the resulting β-hydroxy acid with benzenesulfonyl chloride. Complications in preparing the requisite β-hydroxy acids under typical aldol reaction conditions rendered this route unworkable. The complexity and intractability of the aldol reaction mixtures was attributed to the multiple possibilities of …

Degradation Of Trazine Compounds Via Metallic Iron Under Acidic Conditions, Tracy Dombek

Masters Theses

The degradation of dissolved dimethoxyatrazine (2-chloro-4,6-dimethoxy-1,3,5-triazine), terbutylazine (2-chloro-4-ethylamino-6-terbutylamino-1,3 ,5-triazine) and deisopropylatrazine (2-amino-4-chloro-6-ethylamino-1,3,5-triazine) via metallic iron was studied as a function of solution pH. Generally, degradation was more rapid the lower the solution pH and higher the compound pKa. For dimethoxyatrazine k_SA (k_SA= k' (min^-1)* V (L) / M (g) I SA(m²/g)) was found to be 1.33 (± 0.07) E-4 min^-1 m^-2 L at pH 2, 6.1 (± 0.6) E-5 min^-1 m^-2 L at pH 3 and 4.4 (± 0.6) E-5 min^-1 m^-2 L at pH 4. For …

Validation Of The Thermochemical Cycle Used In Computing Absolute Gas Phase Acidities And A Molecular-Orbital Study Of Protonated Ammonia-Water Cluster Ions, Jeremiah Aeschleman

Masters Theses

This work is comprised of two separate computational projects, an evaluation of the validity of an assumption made when computing absolute gas phase acidities with a thermochemical cycle and a molecular-orbital study of protonated ammonia-water clusters ions.

Relative gas phase acidities are measured experimentally and then adjusted using Hess' law to align them with an absolute scale. In the Hess' law calculation it is assumed that the electron affinity of A• and the ionization energy of H• are independent of temperature. To test this assumption, absolute enthalpies were computed for the anion (A^-) and the radical (A•) at …