BEGIN:VCALENDAR VERSION:2.0 PRODID:icalendar-ruby CALSCALE:GREGORIAN X-WR-CALNAME:Final Doctoral Defense for Himanshu Bhatia X-WR-TIMEZONE:Central Time (US & Canada) BEGIN:VEVENT DTSTAMP:20260605T225756Z UID:tag:localist.com\,2008:EventInstance_53054721649187 DTSTART:20260611T150000Z DTEND:20260611T180000Z DESCRIPTION:Himanshu Bhatia\, a doctoral candidate in chemistry\, will defe nd their dissertation titled “Synthesis of First-Row Transition Metal Co mplexes Supported by Tetraaza and Tetraamido Macrocyclic Ligands: Catalyst s in Nitrene Transfer Chemistry.” Their advisor\, Dr. Pericles Stavropou los is an professor in chemistry. The dissertation abstract is provided b elow.\n\n \n\nThe development of efficient and sustainable catalysts for n itrene transfer reactions remains an important objective in synthetic chem istry because these transformations provide direct access to valuable nitr ogen-containing compounds through C–N bond formation. In particular\, th e aziridination of olefins offers a versatile route to strained nitrogen h eterocycles that serve as important intermediates in pharmaceutical\, agro chemical\, and materials synthesis. This\ndissertation investigates the ro le of macrocyclic ligand architecture in controlling first-row transition- metal-mediated nitrene transfer through two complementary catalyst platfor ms: pyridinophane-supported metal complexes and chiral tetraamido macrocyc lic cobalt complexes.\nIn the first study\, a 12-membered pyridinophane li gand containing two pyridine and two tertiary amine donors (tBuN4) was emp loyed to support a series of first-row transition-metal complexes\, includ ing Mn(II)\, Fe(II)\, Co(II)\, Ni(II)\, Cu(I)\, and Cu(II) derivatives. Th ese complexes were evaluated as catalysts for the aziridination of olefins using iminoiodinane nitrene precursors. Among the metals examined\, the C u(I) and Cu(II) complexes displayed the highest catalytic activity\, affor ding efficient aziridination of styrenyl substrates\, whereas the Mn\, Fe\ , Co\, and Ni analogues exhibited only modest reactivity. Aromatic olefins proved significantly more reactive than aliphatic substrates\, while incr easing steric congestion at the α- and β-positions reduced product yield s and promoted competing ring-opening pathways. Mechanistic investigations \, including Hammett analyses\, kinetic isotope effect measurements\, and stereochemical probe\nstudies\, support a stepwise aziridination pathway i nvolving sequential formation of the two N–C bonds. Computational studie s indicate that the reactive copper nitrene intermediates derived from bot h Cu(I) and Cu(II) possess significant nitrene-centered radical character and closely spaced\nspin states\, with the greater electrophilicity of the Cu(I)-derived nitrene accounting for its enhanced catalytic performance. The second study focuses on the development of a new family of chiral tetr aamido macrocyclic ligands and their corresponding Co(III) complexes as ca talysts for nitrene transfer. These complexes are paramagnetic (S = 1) in solution and exhibit semi-reversible Co(II/III) redox processes together w ith irreversible anodic oxidation events. Evaluation of these cobalt\ncomp lexes in reactions of olefins with iminoiodinane nitrene precursors reveal ed efficient aziridination and allylic amination reactivity\, particularly for sterically unhindered styrenes. Mechanistic studies indicate that azi ridination proceeds through stepwise formation of the two N–C bonds and involves both polar and radical contributions to the reaction pathway. Thi s behavior differs from that reported for related Co(TAML) systems\, in wh ich ligand-centered redox activity and substrate-to-ligand electron transf er play a dominant role. Electrospray\nionization mass spectrometry provid es evidence for the formation of both mono- and bis-nitrene cobalt species under catalytic conditions\, although their precise electronic structures and roles in the catalytic cycle remain subjects for future investigation . Collectively\, these studies demonstrate that macrocyclic ligand design exerts a profound influence on the reactivity and mechanism of first-row t ransition-metal nitrene-transfer catalysts. The pyridinophane platform rev eals the critical role of metal identity in determining catalytic efficien cy\, while the chiral tetraamido framework illustrates how modification of the ligand\nenvironment can alter the electronic structure and mechanisti c behavior of cobalt-mediated nitrene transfer. Together\, the results pro vide new insight into the factors governing C–N bond formation and estab lish guiding principles for the future development of selective and\nsusta inable catalysts for aziridination and related nitrene-transfer transforma tions. GEO:37.952615;-91.775715 LOCATION:Bertelsmeyer Hall\, 110H Conference Room SUMMARY:Final Doctoral Defense for Himanshu Bhatia URL;VALUE=URI:https://calendar.mst.edu/event/final-doctoral-defense-for-him anshu-bhatia END:VEVENT END:VCALENDAR