Ultra‐small nanoparticles of CeO2 obtained in molecular form, so‐called molecular nanoparticles, have been limited to date to a family whose largest member is of nuclearity Ce40 with a {Ce40O58} core atom count. Herein we report that a synthetic procedure has been developed to the cation [Ce100O149(OH)18(O2CPh)60(PhCO2H)12(H2O)20]16+, a member with a much higher Ce100 nuclearity and a {Ce100O167} core that is more akin to the smallest ceria nanoparticles. Its crystal structure reveals it to possess a 2.4 nm size and high D2d symmetry, and it has also allowed identification of core surface features including facet composition, the presence and location of Ce3+and H+ (i.e. HO−) ions, and the binding modes of the ligand monolayer of benzoate, benzoic acid, and water ligands.

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.

The use of halide ions in the synthesis of Ce/O clusters diverts the reaction to two halide-containing products: Cl− gives a new Ce20 nuclearity with both a high 1 : 1 Ce3+ : Ce4+ ratio and a high percentage of (100) facet coverage, whereas F− gives a known Ce6 nuclearity.

Two new CeIV/O2- clusters, (pyH)8[Ce10-O4(OH)4(O3PPh)12(NO3)12] (1) and [Ce6O4(OH)4(O2PPh2)4(O2CtBu)8] (2), have been prepared that contain P-based ligands for the first time. They were obtained from the reaction of (NH4)2[Ce(NO3)6], PhPO3H2 or...

Ultra‐small nanoparticles of CeO2 obtained in molecular form, so‐called molecular nanoparticles, have been limited to date to a family whose largest member is of nuclearity Ce40 with a {Ce40O58} core atom count. Herein we report that a synthetic procedure has been developed to the cation [Ce100O149(OH)18(O2CPh)60(PhCO2H)12(H2O)20]16+, a member with a much higher Ce100 nuclearity and a {Ce100O167} core that is more akin to the smallest ceria nanoparticles. Its crystal structure reveals it to possess a 2.4 nm size and high D2d symmetry, and it has also allowed identification of core surface features including facet composition, the presence and location of Ce3+and H+ (i.e. HO−) ions, and the binding modes of the ligand monolayer of benzoate, benzoic acid, and water ligands.