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Two new Ce IV /O 2− clusters, (pyH) 8 [Ce 10 O 4 (OH) 4 (O 3 PPh) 12 (NO 3 ) 12 ] (1) and [Ce 6 O 4 (OH) 4 (O 2 PPh 2 ) 4 (O 2 C t Bu) 8 ] (2), have been prepared that contain P-based ligands for the first time. They were obtained from the reaction of (NH 4 ) 2 [Ce(NO 3 ) 6 ], PhPO 3 H 2 or Ph 2 PO 2 H, and t BuCO 2 H in a 2 : 1 : 2 molar ratio in pyridine/MeOH (10 : 1 mL). Both compounds contain a {Ce 6 O 4 (OH) 4 } face-capped octahedral core, with 1 containing an additional four Ce IV on the outside to give a supertetrahedral Ce 10 topology; the {Ce 6 O 8 } unit is the smallest recognizable fragment of the fluorite structure of CeO 2 . The HO˙ radical scavenging activities of 1 and 2 were measured by UV/vis spectral monitoring of methylene blue oxidation by HO˙ radicals in the presence and absence of the Ce/O clusters, and the results compared with those for larger Ce 24 and Ce 38 molecular nanoparticles of CeO 2 prepared in previous work. 1 and 2 are both very poor HO˙ radical scavengers compared with Ce 24 and Ce 38 , a result that is consistent with reports in the literature that PO 4 3− ions inhibit the radical scavenging ability of traditional CeO 2 nanoparticles and putatively assigned to PO 4 3− binding to the surface. 

Abstract Ultra‐small nanoparticles of CeO₂obtained in molecular form, so‐called molecular nanoparticles, have been limited to date to a family whose largest member is of nuclearity Ce₄₀with 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 Ce₁₀₀nuclearity 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 D_2dsymmetry, 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. 

Abstract Ultra‐small nanoparticles of CeO₂obtained in molecular form, so‐called molecular nanoparticles, have been limited to date to a family whose largest member is of nuclearity Ce₄₀with 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 Ce₁₀₀nuclearity 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 D_2dsymmetry, 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.