Document Type

Dissertation

Degree

Doctor of Philosophy

Major

Chemistry, Inorganic

Date of Defense

4-21-2017

Graduate Advisor

Stephen M. Holmes, Ph.D.

Committee

Eike Bauer, Ph.D.

Alicia M. Beatty, Ph.D.

Janet Braddock-Wilking, Ph.D.

Abstract

To investigate the hypotheses, that systematically changing the electronic and relative sizes of tricyanido building blocks will tune magnetic properties of their cluster derivatives, we prepared two new tricyanido pyrazolylborate complexes, [NEt4][(Tp*Me)­Fe(CN)3]­·H2O and [NEt4]­[(Tp*Bn)­FeIII(CN)3]­·H2O·MeOH, and investigated their self-assembly. The new building blocks were prepared, structurally characterized, and their coordination chemistry explored to prepare small molecule-based magnetic materials.

Three bent trinuclear ferromagnetic cluster derivatives of {[(Tp*Me)­FeIII(CN)3][NiII(L)2]}·n(solvent) [L = 2,2′-bipyridine or bpy, diethylenetriamine or DETA and tris(2-aminoethyl)amine or tren] stoichiometry were prepared and their properties compared to other magnetic analogues. Another building block, [NEt4]­[(Tp*Bn)­FeIII(CN)3]­·H2O·MeOH, was also used to prepare two linear trinuclear derivatives of {(Tp*Bn)­Fe(CN)3}2­­MII(DMF)4]}­×2DMF (MII = Mn, Ni) stoichiometry.

Under similar synthetic conditions two tetranuclear derivatives, {[(Tp*Me)­FeIII(CN)3]2­­[NiII(DMF)4]2[OTf]2}­×2DMF and {[(Tp*Me)FeIII(CN)3][NiII(bpy)2][ClO4]2}­×3MeCN­­×2H2O×MeOH were obtained. Systematic alter­ation of the reaction conditions also allowed for the isolation of a new hexanuclear analogue, {[(Tp*Me)FeIII(CN)3][NiII(DMF)3]2}­­×4DMF­×H2O, and octa- and nonanuclear ones, {[(Tp*Me)FeIII(CN)3][NiII(tren)]4­­[ClO4]4}·7H2O­·4MeCN and {[(Tp*Me)­FeIII(CN)3]6­[NiII3(MeOH)8]3}­­×3H2O­×8MeOH, respectively. Each of these clusters display ferromagnetic coupling of their paramagnetic nickel (S = 1) and iron (S = ½) spin centers.

Overall, we find that magnetic interactions may be predicted using molecular orbital symmetry arguments and that the electronic and magnetic properties of cluster derivatives (ten total) are directly related to those of the chosen building blocks. Slow magnetic relaxation is generally seen for polynuclear analogues when the magnetic anisotropy axes are parallel.

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