Expansion of the Family of Molecular Nanoparticles of Cerium Dioxide and Their Catalytic Scavenging of Hydroxyl Radicals

Abstract

The syntheses, crystal structures, and catalytic radical scavenging activity are reported for four new molecular clusters that have resulted from a bottom-up molecular approach to nanoscale CeO2. They are [Ce6O4(OH)4(dmb)12(H2O)4] (dmb– = 2,6-dimethoxybenzoate), [Ce16O17(OH)6(O2CPh)24(HO2CPh)4], [Ce19O18(OH)9(O2CPh)27(H2O)­(py)3], and [Ce24O27(OH)9(O2CPh)30(py)4]. They represent a major expansion of our family of so-called “molecular nanoparticles” of this metal oxide to seven members, and their crystal structures confirm that their cores all possess the fluorite structure of bulk CeO2. In addition, they have allowed the identification of surface features such as the close location of multiple Ce3+ ions and organic ligand binding modes not seen previously. The ability of all seven members to catalytically scavenge reactive oxygen species has been investigated using HO• radicals, an important test reaction in the ceria nanoparticle biomedical literature, and most have been found to exhibit excellent antioxidant activities compared to traditional ceria nanoparticles, with their activity correlating inversely with their surface Ce3+ content.

Quick and robust PDF data acquisition using a laboratory single-crystal X-ray diffractometer for study of polynuclear lanthanide complexes in solid form and in solution

“…Polynuclear lanthanide complexes are of high interest owing to wide possible applications for luminescence sensors (Kreno et al, 2012), thermometers (D'Vries et al, 2013) and markers (Ga ´lico et al, 2021), for magnetic data storage (Xiong et al, 2017) and magnetic refrigeration (Wang et al, 2019;, as secondary building blocks for metal-organic framework (MOF) design (Feng et al, 2020), and as nanoparticles with atomic-precision size control (Russell-Webster et al, 2020) and catalytic properties (Mitchell et al, 2021;Arumugam et al, 2020).…”

Snapshots of Ce70 Toroid Assembly from Solids and Solution

“…Of special note, Zr/Hf MOFs are built of the M6(OH,O)8 hexamer (M6), and these MOFs are widely exploited for virtually every application that has been developed to date including catalysis and separations. 37 The M6 cluster is contained within most M IV -oxoclusters, as well as in fluorite-type MO2; but it is not possible to simply build MO2 (and intermediate size clusters such as M38 [38][39][40][41][42][43][44] ) from M6-units, since the M6-units share M2 edges in the larger assemblies. In fact, M6 is shown to co-exist in solution with monomers, dimers and hexamers, [45][46] likely in dynamic equilibrium.…”

“…Gaining importance and attention is the Ce-oxo clusters, as molecular models of nano-CeOx catalysts, as well as functional catalysts themselves. The Ce III/IV redox activity distinguishes this family of metal-oxo clusters: Ce10, Ce22, and Ce40 oxoclusters have distinct Ce III and Ce IV sites, 44,47 while Ce38 reports mixed Ce III/IV -sites. 48 The M IV 70 sulfate ring structure, originally described for U IV 70, followed by Ce IV 70 and Zr70, [49][50][51][52] is the only M IV -topology besides M6 that spans transition metals, lanthanides, and actinides, and is also the largest.…”

“…Ce-oxo clusters have been gaining importance and attention as molecular models of nano-CeO x catalysts as well as functional catalysts themselves. The Ce III/IV redox activity, without changes in coordination geometry, distinguishes this family of metal-oxo clusters: Ce 19 , Ce 22 , Ce 24 , Ce 40 and Ce 100 oxoclusters have distinct Ce III and Ce IV sites, ,, while Ce 38 reports mixed Ce III/IV sites . Given the rapidly growing interest in large molecular Ce-oxo clusters, we provide a summary of those of nuclearity >10 (plus brief synthesis information) in Table S21, including those reported here.…”

Cerium-oxo clusters for photocatalytic aerobic oxygenation of sulfides to sulfoxides

“…[29][30][31] As a subclass of molecular metal oxides, cerium-oxo clusters (COCs), also termed ceria nanoclusters, have experienced rapid development in the past decade. [32][33][34][35][36][37][38][39] Owing to their unique cluster scaffold and atomically precise structural arrangement, they could be regarded as nanosized assemblies consisting of multiple metal centers that bridge between Cebased coordination compounds and bulk CeO 2 , thus rendering them ideal candidates as structure and reaction model compounds of CeO 2 . [33][34][35]39 As such, the structure diversity of such clusters has been extensively expanded from the simple {Ce 6 } to milestone {Ce 38 } and {Ce 40 } discovered by Christou, 33,35 and to the high nuclearity of {Ce 70 } and {Ce 100 } reported by Nyman 36,37 and Christou, 34 respectively.…”