We report a new cyanide-bridged Cs⊂{FeCo} box, a soluble model of photomagnetic Prussian blue analogues (PBAs). The Cs ion has a high affinity for the box and can replace the K ion in the preformed K-cube. This exchange is kinetically impeded at room temperature but is accelerated by heating and using the 18-crown-6 ether. The inserted Cs ion confers a high robustness to the cube, which withstands boiling, as shown by variable-temperature NMR studies. The stability of this model complex in solution allows the probing of the electronic interaction between the alkali ion and the cyanide cage by using various techniques. These interactions are known to play a role in the photomagnetic behaviour of PBAs. Firstly, the Cs NMR spectroscopy proves that there is an electronic communication between the encapsulated alkali ion and the cyanide cage. The measured up-field signal, observed at ca. -200 ppm at 300 K, reveals that a certain amount of spin density is transferred through the bonds from the paramagnetic Co(ii) ion to the encapsulated cation. Secondly, cyclovoltammetric studies show that the nature of the inserted ions affects the redox properties of the cage and influences the electronic communication between the metal ions. However, the differences in the electrochemical properties of the K-cube and the Cs-cube remain moderate. As the switching properties are influenced by the redox potential of the Fe and Co centers, similar photomagnetic behaviour is observed, with both of them being highly photomagnetic. This result contrasts strikingly with previous studies on the 3D polymeric PBAs, where the PBAs with a high amount of Cs show poor photomagnetic behaviour. In that case, cooperative behaviour likely influences the switching properties. Finally, EPR spectroscopy shows that the K-cube is more anisotropic than the Cs-cube. This difference is reflected in the changes occurring in the slow magnetic relaxation (single molecule magnet behaviour) observed in the two cubes.

Divalent lanthanide organometallics are well‐known highly reducing compounds usually used for single electron transfer reactivity and small molecule activation. Thus, their very reactive nature prevented for many years the study of their physical properties, such as magnetic studies on a reliable basis. Herein, the access to rare organometallic sandwich compounds of TmII with the cyclooctatetraenyl (Cot) ligand impacts on the use of divalent organolanthanide compounds as an additional strategy for the design of performing Single Molecule Magnets (SMM). The first divalent thulium sandwich complex with f13 configuration behaving as a single‐molecule magnet in absence of DC field is highlighted.

Over more than 50 years, intermediate valence states in lanthanide compounds have often resulted in unexpected or puzzling spectroscopic and magnetic properties. Such experimental singularities could not be rationalised until new theoretical models involving multiconfigurational electronic ground states were established. In this minireview, the different singularities that have been observed among lanthanide complexes are highlighted, the models used to rationalise them are detailed and how such electronic effects may be adjusted depending on energy and symmetry considerations is considered. Understanding and tuning the ground‐state multiconfigurational behaviour in lanthanide complexes may open new doors to modular and unusual reactivities.

This article presented the synthesis and characterization of original heterobimetallic species combining a divalent lanthanide fragment and a divalent nickel center bridged by the bipyrimidine ligand, a redox-active ligand. X-ray crystal structures were obtained for the Ni monomer (bipym)NiMe2, 1, as well as the heterobimetallic dimer compounds, Cp*2Yb(bipym)NiMe2, 2, along with 1H solution NMR, solid-state magnetic data, and DFT calculations only for 1. The reactivity with CO was investigated on both compounds and the stoichiometric acetone formation is discussed based on kinetic and mechanistic studies. The key role of the lanthanide fragment was demonstrated by the relatively slow CO migratory insertion step, which indicated the stability of the intermediate.

The synthesis of molecular uranium complexes in oxidation states lower than +3 remains a challenge despite the interest for their multielectron transfer reactivity and electronic structures. Herein, we report the one-and two-electron reduction of a U(III) complex supported by an arene-tethered tris(siloxide) tripodal ligand leading to the mono-reduced complexes, [K(THF)-U((OSi(O t Bu) 2 Ar) 3 -arene. EPR and UV/vis/NIR spectroscopies, magnetic, cyclic voltammetry, and computational studies provide strong evidence that complex 2-crypt is best described as a U(II), where the U(II) is stabilized by δ-bonding interactions between the arene anchor and the uranium frontier orbitals, whereas complexes 3 and 3-crypt are best described as having a U(III) ion supported by the direduced arene anchor. Three quasi-reversible redox waves at E 1/2 = −3.27, −2.45, and −1.71 V were identified by cyclic voltammetry studies and were assigned to the U(IV)/U(III), U(III)/U(II), and U(II)/U(III)−(arene) 2− redox couples. The ability of complexes 2 and 3 in transferring two-and three-electrons, respectively, to oxidizing substrates was confirmed by the reaction of 2 with azobenzene (PhNNPh), leading to the U(IV) complex, [K(Et 2 O)U((OSi(O t Bu) 2 Ar) 3 -arene)(PhNNPh)(THF)] (4), and of complex 3 with cycloheptatriene, yielding the U(IV) complex, [(K(Et 2 O) 2 )U((OSi(O t Bu) 2 Ar) 3 -arene)(η 7 -C 7 H 7 )] ∞ (6). These results demonstrate that the arene-tethered tris(siloxide) tripodal ligand provides an excellent platform for accessing low-valent uranium chemistry while implementing multielectron transfer pathways as shown by the reactivity of complex 3, which provides the third example of a U(I) synthon.

Herein, we report a cross-electrophile coupling of benzonitrile derivatives and aryl halides with a simple cobalt-based catalytic system under mild conditions to form biaryl compounds. Even though the cobalt catalyst is able to activate the C(sp 2 )-CN bond alone, the use of the AlMe3 Lewis acid enhances the reactivity of benzonitriles and improves the cross-selectivity with barely any influence on the functional group compatibility. X-Ray structure determination of an original low-valent cobalt species combined with catalytic and stoichiometric reactions reveal a catalytically active cobalt(I) species towards the aryl halide partner. On the other hand, experimental insights, including cyclic voltammetry experiments, suggest the involvement of a cobalt complex of a lower oxidation state to activate the benzonitrile derivative. Finally, DFT calculations support the proposed mechanistic cycle involving two low-valent cobalt species of different oxidation states to perform the reaction.

The base-free divalent samarium complex Cptt 2Sm (1; Cptt = 1,3-( t Bu)2(C5H3)) has been synthesized in diethyl ether by salt metathesis of SmI2. Crystals of 1 suitable for X-ray study have been obtained by sublimation at 116 °C under reduced pressure. The dissolution of 1 in thf and pyridine solution leads to the solvent adducts Cptt 2Sm­(thf)2 (3) and Cptt 2Sm­(py) (4), respectively, while drying 3 under reduced pressure yields CpttSm­(thf) (5). The reaction of CO2 with the base-free divalent samarium complexes Cptt 2Sm (1) and Cpttt 2Sm (2; Cpttt =1,2,4-( t Bu)3(C5H2)) leads to the clean formation of bridged carbonate samarium dimers [Cpttt 2Sm]2(μ-CO3) (7) and [Cptt 2Sm]2(μ-CO3) (8). This is indicative of the reductive disproportionation of CO2 in both cases with release of CO. This contrasts with the formation of the oxalate-bridged samarium dimer reported from the reaction of CO2 with the Cp*2Sm­(thf)2 complex. Otherwise, the reaction with CO does not proceed with the bulky complexes, while traces of O2 have led to the formation of the original bridged peroxo samarium dimer [Cpttt 2Sm]2(μ-O2) (6). The mechanism for these reactions is studied herein by experiments and also by theoretical computations. The key result is that the different pathways are rather close in energy, which also explains why the nature of the final product, if only one is present, is difficult to predict a priori in this chemistry.

Solvation of [(CNT)Ln(η8‐COT)] (Ln=La, Ce, Nd, Tb, Er; CNT=cyclononatetraenyl, i.e., C9H9−; COT=cyclooctatetraendiid, i.e., C8H82−) complexes with tetrahydrofuran (THF) gives rise to neutral [(η4‐CNT)Ln(thf)2(η8‐COT)] (Ln=La, Ce) and ionic [Ln(thf)x(η8‐COT)][CNT] (x=4 (Ce, Nd, Tb), 3 (Er)) species in a solid‐to‐solid transformation. Due to the severe distortion of the ligand sphere upon solvation, these species act as switchable luminophores and single‐molecule magnets. The desolvation of the coordinated solvents can be triggered by applying a dynamic vacuum, as well as a temperature gradient stimulus. Raman spectroscopic investigations revealed fast and fully reversible solvation and desolvation processes. Moreover, we also show that a Nd:YAG laser can induce the necessary temperature gradient for a self‐sufficient switching process of the Ce(III) analogue in a spatially resolved manner.