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The control of spin multiplicity and magnetic properties by molecular architecture

Yi Liao, University of Massachusetts - Amherst

Abstract

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

Yi Liao, "The control of spin multiplicity and magnetic properties by molecular architecture" (January 1, 2001). Doctoral Dissertations Available from Proquest. Paper AAI3000318.
http://scholarworks.umass.edu/dissertations/AAI3000318

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