Zirconium and Hafnium

Polyazamacrocycle Ligands Facilitate 89Zr Radiochemistry and Yield 89Zr Complexes with Remarkable Stability

“…The distances between the Zr 4+ ions of each monomer subunit and the bridging O atom were observed to be 1.9809(3)­Å, while the Zr–O–Zr angle was observed to be 167.32(7)°. These values are similar to published literature describing other Zr-μ-oxo complexes, and several observations may explain these results. − The pyridyl ring of the PCTA ligand most likely increases the rigidity and preorganization of the resulting Zr-PCTA complex. In addition, numerous inter- and intramolecular hydrogen bonding motifs are observed in the solid state.…”

Periodates of Tetravalent Titanium, Zirconium, Hafnium and Thorium: Synthesis, Characterisation and EXAFS Study

“…The small reduction in the M-O distance is consistent with ionic radii [25] and the agreement between the Hf···I and I···Hf distances, though poorer than with Zr, is still within error. The M-O bond lengths for the Zr and Hf compounds are in excellent agreement with those in the [M 4 (OH) 8 (H 2 O) 16 ] 8+ ions. [17] Interestingly, even accepting their lower reliability, the fits to the data collected on the protonated and potassium-exchanged thorium periodates are also compellingly similar to ZrHIO 6 ·4H 2 O.…”

“…In large part, this is a result of the complex and only partially understood solution chemistry of the group 4 M IV ions in which oxo-or hydroxo-bridge oligomeric hydrolysis products are common features. [16,17] Often this results in rather intractable chemistry. Our general approach was to carry out a variety of exploratory syntheses, examine the products formed by energy dispersive X-ray analysis (EDX) to establish the elements present and their ratios, and use IR spectroscopy to examine the form ([IO 4 ] -or [H 5-n IO 6 ] n-) of any periodate present.…”

Recent Advances in Zirconium-89 Chelator Development

“…Zirconium (II) complexes are known, but they typically require p-donor ligands to enhance stability even under inert atmosphere conditions, and even fewer reports describing the Zirconium (III) oxidation state exist. A significant portion of knowledge regarding this element’s reactivity has been extrapolated from hafnium (Hf) chemistry since their atomic and ionic properties yield similar chemistries with a variety of ligands, and much of what is known about zirconium coordination chemistry has been discovered in the context of solid-state material or catalysis development [ 52 , 53 ]. While research in these areas has provided numerous societal benefits including heat and corrosion resistant coatings; fracture resistant ceramics; and the development of catalysts that play a role in the petroleum, plastics, and pharmaceutical industries, it has been difficult to translate this knowledge into the research fields of radiochemistry and molecular imaging.…”