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TY  - THES
AU  - Sturm, Lisa
TI  - Einfluss von Pseudohalogeniden und Carboxylaten auf die Komplexierung zweiwertiger Metallionen durch Tris(2-pyridinylen-N-oxid)triaminoguanidin
PB  - RWTH Aachen University
VL  - Dissertation
CY  - Aachen
M1  - RWTH-2022-09881
SP  - 1 Online-Ressource : Illustrationen
PY  - 2022
N1  - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University
N1  - Dissertation, RWTH Aachen University, 2022
AB  - C3-symmetric triaminoguanidine based ligands are established as triangular building blocks in supramolecular compounds like polymers or discrete monomers, dimers, and polyhedra. The reaction of tris(2-pyridinylene-N-oxide)triaminoguanidine with zinc(II) carboxylates in presence of (pseudo)halides results in protein-sized metallocycles consisting of twelve ligands linked by octahedrally coordinated zinc(II) centers. Besides crystals of the metallocycles, the crystallization of carboxylate-bridged coordination di/polymers is observed in the same reaction vessel. To address this issue, the influence of the solvent, the chain length of the carboxylate, the co-ligands and their stoichiometry is investigated, while other factors are kept as constant as possible. In this way, a sensitive dependence of the binding motif on the stoichiometric pseudohalide-carboxylate ratio was revealed. Small or no amounts of pseudohalide combined with sufficient equivalents of carboxylate lead to the formation of carboxylate-bridged di/polymers. Increasing the pseudohalide stoichiometry results in the crystallization of mixed compounds and finally of metallocycles. By adjusting the co-ligand stoichiometry, crystallization of a desired compound can be predicted and selectively induced. Applying this principle to the chemically related cadmium(II) yields in a series of carboxylate-bridged di/polymers, whereas the addition of thiocyanate gives a cadmium(II)-bridged structure, which can be considered as metallocycle fragment. Cadmium(II) prefers coordination numbers of six and higher due to its ionic radius, which inhibits the formation of a metallocycle. Cobalt(II) ions instead built up polymers and metallocycles showing the same co-ligand dependence as zinc(II). Magnetic measurements revealed predominantly antiferromagnetic behavior of these compounds due to short Co(II)-Co(II) distances. In heterometallic metallocycles, zinc(II) ions may isolate the cobalt(II) centers, which could probably result in very large discrete molecules with interesting magnetic properties.
LB  - PUB:(DE-HGF)11
DO  - DOI:10.18154/RWTH-2022-09881
UR  - https://publications.rwth-aachen.de/record/854946
ER  -