A General Design Strategy Enabling the Synthesis of Hydrolysis‐Resistant, Water‐Stable Titanium(IV) Complexes

Despite its prevalence in the environment, the chemistry of the Ti4+ ion has long been relegated to organic solutions or hydrolyzed TiO2 polymorphs. A knowledge gap in stabilizing molecular Ti4+ species in aqueous environments has prevented the use of this ion for various applications such as radioi...

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Published in:Angewandte Chemie International Edition 2022-05, Vol.61 (22), p.e202201211-n/a
Main Authors: Koller, Angus J., Saini, Shefali, Chaple, Ivis F., Joaqui‐Joaqui, M. Andrey, Paterson, Brett M., Ma, Michelle T., Blower, Philip J., Pierre, Valérie C., Robinson, Jerome R., Lapi, Suzanne E., Boros, Eszter
Format: Article
Language:English
Subjects:
Aqueous environments
Aqueous solutions
Benzene
Catalysis
Catechol
Chelates
Chelating Agents
Chelation
Computer applications
Coordination Chemistry
Hydrolysis
Metal-organic frameworks
Organometallic Compounds - chemistry
Positron emission
Positron emission tomography
Radiochemistry
Titanium
Titanium - chemistry
Titanium dioxide
Tomography
Water - chemistry
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Summary:Despite its prevalence in the environment, the chemistry of the Ti4+ ion has long been relegated to organic solutions or hydrolyzed TiO2 polymorphs. A knowledge gap in stabilizing molecular Ti4+ species in aqueous environments has prevented the use of this ion for various applications such as radioimaging, design of water‐compatible metal–organic frameworks (MOFs), and aqueous‐phase catalysis applications. Herein, we show a thorough thermodynamic screening of bidentate chelators with Ti4+ in aqueous solution, as well as computational and structural analyses of key compounds. In addition, the hexadentate analogues of catechol (benzene‐1,2‐diol) and deferiprone (3‐hydroxy‐1,2‐dimethyl‐4(1H)‐pyridone), TREN‐CAM and THPMe respectively, were assessed for chelation of the 45Ti isotope (t1/2=3.08 h, β+=85 %, Eβ+=439 keV) towards positron emission tomography (PET) imaging applications. Both were found to have excellent capacity for kit‐formulation, and [45Ti]Ti‐TREN‐CAM was found to have remarkable stability in vivo. The thorough characterization of aqueous stable bidentate chelate systems with Ti4+ including speciation, DFT, and structural characterization of key complexes is reported. Hexadentate analogs of the high‐performing bidentate chelators were also assessed and were assessed for the potential use in kit‐based PET imaging with 45Ti4+.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.202201211