Altering the Spectroscopy, Electronic Structure, and Bonding of Organometallic Curium(III) Upon Coordination of 4,4-bipyridine

Structural and electronic characterization of (Cp\u273Cm)2(4,4\u27-bpy) (Cp\u27 = trimethylsilylcyclopentadienyl, 4,4\u27-bpy = 4,4\u27-bipyridine) is reported and provides a rare example of curium-carbon bonding. Cp\u273Cm displays unexpectedly low energy emission that is quenched upon coordination by 4,4\u27-bipyridine. Electronic structure calculations on Cp\u273Cm and (Cp\u273Cm)2(4,4\u27-bpy) rule out significant differences in the emissive state, rendering 4,4\u27-bipyridine as the primary quenching agent. Comparisons of (Cp\u273Cm)2(4,4\u27-bpy) with its samarium and gadolinium analogues reveal atypical bonding patterns and electronic features that offer insights into bonding between carbon with f-block metal ions

Synthesis, characterization, and high-pressure studies of a 3D berkelium(iii) carboxylate framework material

A berkelium(iii) mellitate, Bk-2[C-6(CO2)(6)](H2O)(8)center dot 2H(2)O, was synthesized and rapidly crystallized by reacting mellitic acid, C-6(CO2H)(6), and BkBr3 center dot nH(2)O in an aqueous medium. Single crystal X-ray diffraction shows that the compound crystallizes as a three-dimensional framework isostructural with Pu(iii), Am(iii), and Cm(iii) mellitates. UV-vis-NIR spectroscopic studies as a function of pressure were performed using a diamond anvil cell and show that the 5f -> 5f transitions of Bk3+ display enhanced hypsochromic shifting when compared to other An(iii) mellitates

Isolation of a Californium(II) Crown-Ether Complex

Californium (Z = 98) is the first member of the actinide series displaying metastability of the 2+ oxidation state. Understanding the origin of this chemical behavior requires characterizing Cf(II) materials, but isolating a complex with this state has remained elusive. The source of its inaccessibility arises from the intrinsic challenges of manipulating this unstable element as well as a lack of suitable reductants that do not reduce Cf(III) to Cf(0). Herein we show that a Cf(II) crown-ether complex, Cf(18-crown-6)I2, can be prepared using an Al/Hg amalgam as a reductant. While spectroscopic evidence shows that Cf(III) can be quantitatively reduced to Cf(II), rapid radiolytic re-oxidation back to the Cf(III) parent occurs and co-crystallized mixtures of Cf(II) and Cf(III) complexes are isolated if the crystallization is not conducted over the Al/Hg amalgam. Quantum chemical calculations show that the Cf‒ligand interactions are highly ionic and that 5f/6d mixing is absent, resulting in remarkably weak 5f→5f transitions and an absorption spectrum dominated by 5f→6d transitions

Two Neptunium(III) Mellitate Coordination Polymers: Completing the Series Np-Cf of Trans-Uranic An(III) Mellitates

Two neptunium(III) mellitates, 237Np2(mell)(H2O)9 center dot 1.5H2O (Np-1 alpha) and 237Np2(mell)(H2O)8 center dot 2H2O (Np-1 beta), have been synthesized from 237NpCl4(dme)2 by reduction with KC8 and subsequent reaction with an aqueous solution of mellitic acid (H6mell). Characterization by single-crystal X-ray crystallography and UV-vis-NIR spectroscopy confirms that the neptunium is in its +3 oxidation state and both polymorphs are isostructural to the previously reported plutonium mellitates. Of the two morphologies, Np-1 alpha is indefinitely stable in air, while Np-1 beta slowly oxidizes over several months. This is due to the change in the energy of the metal-ligand charge-transfer absorption exhibited by these compounds attributed to differing numbers of carboxylate bonds to Np(III), where in Np-1 beta the energy is low enough to result in spontaneous oxidation