Exhaustive oxidation of a nickel dithiolate complex Balwant S. Chohan 1, Erik R. Hosler 2, Robert W. Herbst 3, and Michael J. Maroney 3. (1) Department of Chemistry and Biochemistry, Susquehanna University, 514 University Avenue, Selinsgrove, PA 17870, (2) Department of Chemistry & Biochemistry, Susquehanna University, 514 University Avenue, Selinsgrove, PA 17870, (3) Department of Chemistry, University of Massachusetts, Amherst, MA 01003 The formation of cysteine S-oxygenates is important in redox biology. These roles include the oxidative metabolism of cysteine that is controlled by cysteine-dioxygenase, roles in signaling, transcriptional regulation, and in tuning the properties of metal cofactors. In order to understand the formation and role of S-oxygenates in metalloenzymes, we have have used nickel-aminothiolate complexes because of the ability to control the oxidation of these complexes, and to isolate stable oxidation products. We report oxygenations and peroxidations of a Ni(II) complex of a N 2S 2-donor ligand, (N,N'-dimethyl-N-N'-bis(2-mecaptoethyl)-1,3-propanediaminato) Oxidation of this complex gives a series of S-oxygenates, that have been characterized by ESI-MS and X-ray diffraction. We also report the first example of a mixed sulfonate/thiolate ligated complex. The production of this complex using either O 2 or H 2O 2 as an oxidant demonstrates that S-oxidation can occur preferentially at one of the sulfurs in this system, leading to complexes with widely different S-oxidation states. Undergraduate Research Poster Session: Inorganic Chemistry Erik Hosler is a member of the Class of 2007.

Relative nucleophilicity of a series of zinc aminothiolate complexes Balwant S. Chohan and Suzanne T. Thomas. Department of Chemistry and Biochemistry, Susquehanna University , 514 University Avenue , Selinsgrove , PA 17870 A series of aminothiolate zinc complexes are reported. These complexes vary in the number of N and S-donors in the aminothiolate, and in the degree of steric bulk in the neigborhood of the thiolate functionalities. How these structural factors effect the nucleophilic reactivity of the zinc complexes towards alkylation is reported. Many of the complexes are simple alkylthiolates, others incorporate aryl groups so as to provide steric bulk at the carbon adjacent to the thiolates, others have imine functionalities, and thus the effect of ligand rigidity on thiolate reactivity is also investigated. In cases where there was more than one sulfur donor in the ligand set, the influence of alkylating one thiolate on the ability of the other thiolate(s) was explored. The appropriate kinetics parameters were calculated, and mechanistic interpretations made. The use of X-ray crystallography and ESI-MS allowed for full characterization of the zinc complexes and the alkylated products. Undergraduate Research Poster Session: Inorganic Chemistry Suzanne Thomas is a member of the Class of 2006.

Disruption of intermolecular hydrogen-bonding in fluorenone-alcohol systems by various indoles Crystal M. Schneck , Adam J. Poncheri, and Swarna Basu. Department of Chemistry, Susquehanna University , 514 University Avenue , Selinsgrove , PA 17870 Various substituted indoles have been used to disrupt the hydrogen-bonding between fluorenones and polar solvents such as methanol and ethanol. Indoles are known to quench the fluorescence of fluorenones in highly polar solvents such as dimethyl sulfoxide and acetonitrile but in relatively less polar solvents this mechanism competes with the fluorescence quenching that arises from the hydrogen-bonding and results in a disruption of the hydrogen-bonds and subsequent fluorescence enhancement. This competition has been investigated as a function of solvent polarity using a binary solvent system (acetonitrile and methanol) and the minimum solvent polarity at which indoles quench fluorenone, irrespective of indole concentration, has been determined. Quantum chemical calculations using Gaussian03 have also been carried out to calculate binding energies and orientations of these bimolecular systems. These experiments are serving as a model for the study of similar interactions between proteins and fluorenone-type photoactivators used for cross-linking. Undergraduate Research Poster Session: Physical Chemistry Crystal Schneck is a member of the Class of 2007.

Chemical constituents of Hypericum punctatum Megan Janssen , Heather Matta, and Geneive E Henry. Department of Chemistry, Susquehanna University , 514 University Ave , Selinsgrove , PA 17870 There has been widespread interest in the study of the Hypericum genus owing to the diverse range of structural types and biological properties of the chemical constituents of St. John's wort, Hypericum perforatum. Hypericum punctatum is a closely related species that has not previously been the subject of any phytochemical studies. In an effort to compare the natural products found in the two plant species, we have investigated the acetone extract of the aerial parts of H. punctatum and have identified triterpenes and acylphloroglucinol derivatives. The compounds were purified using silica gel column chromatography and preparative thin layer chromatography, and their structures were determined on the basis of 2D NMR, IR, and GC-MS analyses. Undergraduate Research Poster Session: Organic Chemistry Megan Janssen is a member of the Class of 2006.

New acylphloroglucinol derivatives from Hypericum prolificum Smita Raithore 1 , Geneive E Henry 1 , Yanjun Zhang 2, and Navindra P. Seeram 3. (1) Department of Chemistry, Susquehanna University, 514 University Ave, Selinsgrove, PA 17870, (2) Center for Human Nutrition, David Geffen School of Medicine, University of California, Los Angeles, 900 Veteran Avenue, Los Angeles, CA 90095, (3) Center for Human Nutrition, David Geffen School of Medicine, University of California, 900 Veteran Avenue, Los Angeles, CA 90095 The Hypericum genus (Clusiaceae) is a rich source of interesting natural products, including the acylphloroglucinol derivatives. The acylphloroglucinols comprise a group of structurally diverse and bioactive compounds which have been identified in only a few plant families. Our phytochemical investigation of the hexane extract of the aerial parts of Hypericum prolificum has afforded three new acylphloroglucinol derivatives: prolificin A, B and C. The compounds were purified by silica gel column chromatography, and the structural elucidation was achieved by detailed two-dimensional NMR analysis. Undergraduate Research Poster Session: Organic Chemistry Smita Raithore is a member of the Class of 2007.

Secondary metabolites of Hypericum canadense Robert Crotchfelt and Geneive E Henry. Department of Chemistry, Susquehanna University , 514 University Ave , Selinsgrove , PA 17870 The Hypericum genus is a rich source of structurally diverse natural products which possess a wide array of biological properties. We will discuss the isolation and characterization of the chemical constituents of an acetone extract of Hypericum canadense, a plant which has not previously been studied. The crude plant extract was purified using silica gel column chromatography and preparative thin layer chromatography. The structures of the pure compounds were elucidated using GC-MS, IR and 2D NMR data. Undergraduate Research Poster Session: Organic Chemistry Robert Crotchfelt is a member of the Class of 2006.