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The control of spin multiplicity and magnetic properties by molecular architecture

Yi Liao, University of Massachusetts - Amherst


Various heterospin oligoradicals were prepared. The intramolecular spin coupling of these radicals was studied by ESR spectroscopy. Oligonitroxides and oligophenoxys were synthesized and investigated as potential molecular magnetic materials. ^ Heterospin biradical 3,5-di-tert-butyl-3-(N-tert-butyl-N-aminoxy)-4-oxybiphenyl was synthesized by Suzuki reaction. It showed reversible temperature dependent behaviors in both ESR and UV-vis spectra. Heterospin radicals 3-( N-tert-butyl-N-aminoxy)-nitrenobenzene and 4-(N-tert-butyl-N-aminoxy)-nitrenobenzene were prepared by photolysis of the corresponding azido precursors. The relationship between the intramolecular exchange coupling and the geometry of the molecular structures was studied by ESR spectroscopy. ^ Trinitroxide 2,4,6-tris(4-N-tert-butyl- N-aminoxylphenyl)-s-trazine was synthesized by either Suzuki reaction or direct coupling of aromatic anions with cyanuric chloride. This triradical has a quartet ground state and is stable in air. The crystalline trinitroxide was studied by magnetic analysis and showed a intramolecular ferromagnetic exchange with J/kB = 9.0 K and a intermolecular antiferromagnetic exchange with J/kB = −1.45 K. Oligophenoxys 2,3,5-tris(3,5-di-tert-butyl-4-oxyphenyl)- s-triazine and 2,3-bis(3,5-di-tert-butyl-4-oxyphenyl)-5-( N,N-dimethylamino)-s-triazine were prepared to investigate the properties of s-triazine as an exchange linker. ^ Tetraradical tetrakis(4-N-tert-butyl- N-aminoxylphenyl)silane was designed and synthesized as a potential organic magnet. This tetraradical has a tetrahedral geometry with a silicon atom at its center. Its solution shows a clean nonet in ESR spectrum at room temperature. Its crystal structure was also studied. Black precipitates were observed immediately after it was added in a solution of Mn(II)(hfac) 2 in heptane. ^

Subject Area

Chemistry, Organic|Physics, Electricity and Magnetism

Recommended Citation

Liao, Yi, "The control of spin multiplicity and magnetic properties by molecular architecture" (2001). Doctoral Dissertations Available from Proquest. AAI3000318.