A break in periodicity occurs in the actinide series between plutonium and americium as the result of the localization of 5f electrons. The subsequent chemistry of later actinides is thought to closely parallel lanthanides in that bonding is expected to be ionic and complexation should not substantially alter the electronic structure of the metal ions. Here we demonstrate that ligation of californium(III) by a pyridine derivative results in significant deviations in the properties of the resultant complex with respect to that predicted for the free ion. We expand on this by characterizing the americium and curium analogues for comparison, and show that these pronounced effects result from a second transition in periodicity in the actinide series that occurs, in part, because of the stabilization of the divalent oxidation state. The metastability of californium(II) is responsible for many of the unusual properties of californium including the green photoluminescence.

Radiation dosimeters displaying conspicuous response of irradiance are highly desirable, owing to the growing demand of monitoring high-energy radiation and environmental exposure. Herein, we present a case of dosimetry based on a discrete nanocluster, [Th6(OH)4(O)4(H2O)6](TPC)8(HCOO)4∙4DMF∙H2O (Th-SINAP-100), by judiciously incorporating heavy Th6 polynuclear centers as radiation attenuator and organic linkers as photo-responsive sensor. Interestingly, dual-module photochromic transitions upon multiple external stimuli including UV, β-ray, and γ-ray are integrated into this single material. The striking color change, and more significantly, the visible color transition of luminescence in response to accumulating radiation dose allow an on-site quantitative platform for naked-eye detection of ionization radiations over a broad range (1–80 kGy). Single crystal X-ray diffraction and density functional theory calculations reveal that the dual-module photochromism can be attributed to the π(TPC) → π*(TPC) intermolecular charge transfer driven by enhanced π-π stacking interaction between the adjacent TPC moieties upon irradiation.

Twelve new lanthanide copper heterobimetallic compounds, RE 2 Cu(TeO 3 ) 2 (SO 4 ) 2 (RE = Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), with two different structural topologies, have been prepared by hydrothermal treatment. Both structure types crystallize in the triclinic space group, P1̅ , but the unit cell parameters and structures are quite different. The earlier RE 2 Cu(TeO 3 ) 2 (SO 4 ) 2 (RE = Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm) share a common structural motif consisting of edge-sharing LnO 8 chains and [Cu-(TeO 3 ) 2 (SO 4 ) 2 ] 6− units. The later lanthanide version (Yb and Lu) is composed of edge-sharing LnO 7 dimers bridged by similar [Cu(TeO 3 ) 2 (SO 4 ) 2 ] 6− units. The change in the structure type can be attributed to the decreasing ionic radii of the lanthanides. The compounds containing RE 3+ ions with diamagnetic ground states (Y 3+ and Eu 3+ ) exhibit antiferromagnetic ordering at 12.5 K and 15 K, respectively, owing to the magnetic exchange between Cu 2+ moments. No magnetic phase transition was observed in all the other phases. The lack of magnetic ordering is attributed to the competing magnetic interactions caused by the presence of paramagnetic RE 3+ ions. The magnetism data suggests that substantial 3d−4f coupling only occurs in the Yb analogue.

A unique selective crystallization approach for simple and efficient lanthanide separation has been developed by employing an iodate–sulfate mixed-anion system.