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Kayleigh Bemisderfer, a master's degree candidate in forensic science at Buffalo State, will present her master's thesis seminar, "Synthesis and Characterization of Pyrazole-Substituted Tetraazamacrocyclic Ligands for Contrast Enhancement in Magnetic Resonance Imaging (MRI)," at 12:30 p.m. Tuesday, April 26, in Science Building 272. Light refreshments will be served before the seminar. This seminar is supported by the Faculty-Student Association.

Abstract
Magnetic resonance imaging (MRI) has become one of the most important diagnosis tools available in medicine. Typically MRI is not capable of sensing biochemical activities. However, recently emerged activatable MRI contrast agents (CAs), whose relaxivity is variable in response to a specific parameter change in the surrounding physiological microenvironment, potentially allow for MRI to indicate biological processes. This has inspired our efforts to synthesize and characterize ligands based on the tetraazamacrocyclic framework of 1,4,8,11-tetraazacyclotetradecane (cyclam) with functional pendant arms. Cyclam possesses four nitrogen donor atoms that can be arranged to form a chelate ring, which is able to complex with a metal center. Complexes of macrocyclic ligands are of great importance in enhancing a various number of biological processes such as photosynthesis and dioxygen transport, catalytic properties, and potential applications as metal extractants, radiotherapeutic, and medical imaging agents.

The obtention of several isomers: tris(t-butyl)-1,4,8,11-tetraazacyclotetradecane-1,4,11-tricarboxylate (1,4,11-triboc cyclam), bis(t-butyl)-1,4,8,11-tetraazacyclotetradecane-1,11-dicarboxylate (1,11-diboc cyclam) and bis(t-butyl)-1,4,8,11-tetraazacyclotetradecane-1,8-dicarboxylate (1,8-diboc cyclam) was made possible from reacting cyclam with the tert-butyloxycarbonyl (Boc) protecting group. The different isomers were then each appended with pendant arms by reaction with the corresponding equivalents of either 1-(2-bromoethyl)-1H-pyrazole or 1-(2-bromoethyl)-3,5-dimethyl-1H-pyrazole. Thereafter, the protective Boc groups were removed from the compound by heating in water for an extended time to afford the unprotected macrocycles with 2 or 3 pyrazole pendant groups. The resulting ligand systems could potentially be further functionalized if desired. Synthesis of a structurally similar ligand, 5,12-methyl-7,14-bis-methyl-tetra-1,4,8,11-(pyrazoylethyl)-1,4,8,11-tetraazacyclotetradecane (Tet-A), was also carried out. A crystal structure of the Tet-A ligand was acquired having cell lengths of a 10.2359(6) b 16.9312(11) c 15.9755(10) and angles of ? 90 ? 100.170(2) ? 90. The crystals of the Tet-A ligand belong to the space group P 21/c. The proton NMR spectra of all synthesized ligand systems show highly dispersed and relatively sharp proton resonances.