Molecular solids of actinide hexacyanoferrate: Structure and bonding

Abstract

Abstract. The hexacyanometallate family is well known in transition metal chemistry because the remarkable electronic delocalization along the metal-cyano-metal bond can be tuned in order to design systems that undergo a reversible and controlled change of their physical properties. We have been working for few years on the description of the molecular and electronic structure of materials formed with [Fe(CN) 6 ] n-building blocks and actinide ions (An = Th, U, Np, Pu, Am) and have compared these new materials to those obtained with lanthanide cations at oxidation state +III. In order to evaluate the influence of the actinide coordination polyhedron on the threedimensional molecular structure, both atomic number and formal oxidation state have been varied : oxidation states +III, +IV. EXAFS at both iron K edge and actinide L III edge is the dedicated structural probe to obtain structural information on these systems. Data at both edges have been combined to obtain a three-dimensional model. In addition, qualitative electronic information has been gathered with two spectroscopic tools : UV-Near IR spectrophotometry and low energy XANES data that can probe each atom of the structural unit : Fe, C, N and An. Coupling these spectroscopic tools to theoretical calculations will lead in the future to a better description of bonding in these molecular solids. Of primary interest is the actinide cation ability to form ioniccovalent bonding as 5f orbitals are being filled by modification of oxidation state and/or atomic number.

Americium(III) coordination chemistry: An unexplored diversity of structure and bonding

“…In a previous article, we have provided a first estimate of the Cf-O aq average distance with no a priori restriction on the coordination polyhedron [22]. Recently, we have recorded the data with an extended k range [23]. It has been fitted according to two typical distinct models: square antiprism (SA, CN = 8) and tricapped trigonal prism (TTP, CN = 6 + 3) with no clear distinction between the two results: eight oxygen atoms at 2.42 Å for SA, nine oxygen atoms at 2.41 Å for the average of TTP, keeping in mind that a difference of one unit in coordination number over nine (i.e.…”