Coordination Complexes of 1,2,3,5-Dithiadiazolyl Radical Ligands: Magneto-Structural Correlations of Molecule Based Magnets




Maahs, Adam

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University of Guelph


This thesis presents examples of lanthanide and transition metal complexes of 1,2,3,5-dithiadiazolyl radical ligands. Three-dimensionally ordered complexes and complexes demonstrating single molecule magnet (SMM) behaviour are reported. The radical ligand 4-(2ʹ-benzoxazolyl)-1,2,3,5,-dithiadiazolyl (boaDTDA) has been coordinated to several lanthanide ions (CeIII, PrIII, NdIII, EuIII) forming 1D coordination polymers of the formula [Ln(hfac)3(boaDTDA)]n (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato). Lanthanide-radical coupling in [Ln(hfac)3(boaDTDA)]n complexes is ferromagnetic (FM). Due to FM interchain interactions, [Nd(hfac)3(boaDTDA)]n orders FM below 2.2 K. 1D lanthanide-radical chains are also obtained for the radical ligand 4-(2ʹ-pyrimidyl)-1,2,3,5-dithiadiazolyl (pymDTDA). [Ln(hfac)3(pymDTDA)]n complexes (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb) exhibit antiferromagnetic (AF) lanthanide-radical coupling. As a result of interchain interactions, [Tb(hfac)3(pymDTDA)]n orders AF below 3.2 K. A series of new substituted pymDTDA radical ligands is presented in this thesis. The synthesis and characterization of 4-(2ʹ-4-(2ʹʹ-R)-pyrimidyl)-1,2,3,5-dithiadiazolyl (R = furyl, pyridyl, thiophenyl) ligands is presented along with a diamagnetic analogue, 4-(2ʹ-furyl)-2,2ʹ-bipyrimidine (furylbipym). Dysprosium complexes of 4-(2ʹ-4-(2ʹʹ-furyl)-pyrimidyl)-1,2,3,5-dithiadiazolyl (furylpymDTDA) and furylbipym exhibit SMM behaviour. By design, DyIII ions bridged by furylpymDTDA and furylbipym are coordinated in unique environments unrelated by symmetry and are magnetically coupled to each other. The complexes [Dy(hfac)3]2(furylpymDTDA) and [Dy(hfac)3]2(furylbipym) therefore fulfill the basic requirements to function as a CNOT quantum computing gate. The transition metal complexes Ni(hfac)2(furylpymDTDA) and Co(hfac)2(furylpymDTDA) are isomorphous and form intermolecular contacts through π-stacking of furylpymDTDA ligands which lead to FM intermolecular coupling. As a result of further FM intermolecular interactions, Co(hfac)2(furylpymDTDA) orders FM below 4.6 K.