Chemistry of the f-elements division

---

Polymer and Cluster Chemistry of f-Elements

Because of their strong tendency towards hydrolysis, the cationic species of f-elements (i.e. actinides and lanthanides) have an intrinsic nature to form poly-oxo polymer/cluster complexes in aqueous systems. These polymer/cluster complexes of f-elements are of particular interest in terms of not only their fundamental coordination chemistry, but also their potential implications for engineered- (e.g. nuclear fuel reprocessing) or environmental systems (e.g. geological disposal of radioactive wastes). Based on this background, we are aiming to understand the basic physical/chemical properties of the polymer/cluster complexes of f-elements under a wide range of aqueous conditions. Our research activities involve;

1. synthesis of new polymer/cluster complexes of f-elements, and characterisation of the synthesised complexes by single-crystal X-ray diffraction and other spectroscopic techniques, and
2. characterisation of the polymer/cluster complexes in solution by X-ray absorption spectroscopy, X-ray and light scattering, etc.

Figure: Molecular structure of the hexanuclear Ce(IV) complex synthesised from an aqueous solution of formic acid. Six Ce(IV) atoms are linked with the oxo/hydroxo groups produced via the hydrolysis, and the exterior of the hexanuclear core is further enclosed with bidentately coordinating formate ligands to stabilise the hexanuclear structure. Similar hexanuclear complexes can be found for tetravalent actinides (Th(IV), U(IV), Np(IV) and Pu(IV)) as well as other transition metals, such as Zr(IV).

Core techniques involved

• Single-crystal X-ray diffraction
• Powder X-ray diffraction
• X-ray absorption spectroscopy
• Quantum chemical calculations

Collaboration partners

• Université de Lille (Unité de Catalyse et Chimie du Solide)
• European Synchrotron Radiation Facility (ROBL beamline)

Recent key publications

• “Synthesis of coordination polymers of tetravalent actinides (uranium and neptunium) with a phthalate or mellitate ligand in an aqueous medium”,
  Inorg. Chem., ASAP (2017).
• “An in-situ Spectroscopic Study of Nanocrystal Evolution: Hydrolysis of Tetravalent Cerium for a Simple Route to Nanocrystalline Cerium Dioxide”,
  Chem. Eur. J., 19(23), 7348-7360 (2013).
• “Crystal Structure and Solution Species of Ce(III) and Ce(IV) Formates – From Mononuclear to Hexanuclear Complexes”,
  Inorg. Chem., 52(20), 11734-11743 (2013).
• “Dinuclear Complexes of Tetravalent Cerium in an Aqueous Perchloric Acid Solution”,
  Dalton Trans., 41(24), 7190-7192 (2012).

---