Multidentate ligand kinetics. XIV. Formation and dissociation kinetics of rare earth-cyclohexylenediaminetetraacetate complexes
About: This article is published in Inorganic Chemistry.The article was published on 1970-08-01. It has received 70 citations till now. The article focuses on the topics: Ligand & Denticity.
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TL;DR: This hypothesis predicts that subtle changes in formulation can further enhance the intrinsic safety of these complexes and is supported by acute toxicity experiments, which demonstrate that despite a 50-fold range of LD50 values for four Gd complexes, all become lethally toxic when they release precisely the same quantity of Gd3+.
431 citations
TL;DR: This review aims to examine the strategic design of ligands synthesised for this purpose, provide an overview of recent successes in gadolinium-based contrast agent development and assess the requirements for clinical translation.
Abstract: Gadolinium(III) complexes have been widely utilised as magnetic resonance imaging (MRI) contrast agents for decades. In recent years however, concerns have developed about their toxicity, believed to derive from demetallation of the complexes in vivo, and the relatively large quantities of compound required for a successful scan. Recent efforts have sought to enhance the relaxivity of trivalent gadolinium complexes without sacrificing their stability. This review aims to examine the strategic design of ligands synthesised for this purpose, provide an overview of recent successes in gadolinium-based contrast agent development and assess the requirements for clinical translation.
174 citations
TL;DR: Kumar et al. as discussed by the authors used ab initio quantum chemistry methods (B3LYP/LACVP*) to predict structures and energetics of the DOTA conjugate.
Abstract: A promising cancer therapy involves the use of the macrocyclic polyaminoacetate DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) attached to a tumor-targeting antibody complexed with the β emitter 90Y3+. However, incorporation of the 90Y into the DOTA conjugate is too slow. To identify the origins of this problem, we used ab initio quantum chemistry methods (B3LYP/LACVP* and HF/LACVP*) to predict structures and energetics. We find that the initial complex YH2(DOTA)+ is 4-coordinate (the four equivalent carboxylate oxygens), which transforms to YH(DOTA) (5-coordinate with one ring N and four carboxylate oxygens), and finally to Y(DOTA)-, which is 8-coordinate (four oxygens and four nitrogens). The rate-determining step is the conversion of YH(DOTA) to Y(DOTA)-, which we calculate to have an activation free energy (aqueous phase) of 8.4 kcal/mol, in agreement with experimental results (8.1−9.3 kcal/mol) for various metals to DOTA [Kumar, K.; Tweedle, M. F. Inorg. Chem. 1993, 32, 4193−4199; Wu...
69 citations
01 Jan 2008
TL;DR: In this article, the authors focus on aqueous actinide chemistry, reflecting the wide variety of studies on actinides reactions in non-aqueous solvents.
Abstract: The solution chemistry of the actinide elements has been explored in aqueous and organic solutions. While the relative stabilities of the actinide oxidation states and the types of complexes formed with the actinide cations in these states vary between solvents, the fundamental principles governing their redox reactions and their complexation strengths are the same regardless of the solvent. This chapter focuses on aqueous actinide chemistry, reflecting the wide variety of studies on actinide reactions in aqueous solutions. However, three factors that are important for actinides in non–aqueous solvents should be noted. First, in non–aqueous solvents, the formation of neutral cation–anion ion pairs is often dominant due to the lower (as compared to water) dielectric constants of the solvents. Second, non–aqueous conditions also allow the formation of complexes between actinide cations and ligands containing soft Lewis base groups, such as sulfur. Third, non–aqueous solvents are often useful for stabilizing redox–sensitive actinide complexes, as oxidation states that are unstable in aqueous solution may be stable in non–aqueous solutions (Mikheev et al., 1977; Hulet et al., 1979).
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