Magnetocaloric effect in hexacyanochromate Prussian blue analogs

We report on the magnetocaloric properties of two molecule-based hexacyanochromate Prussian blue analogs, nominally CsNi[Cr(CN)_6](H_2O) and Cr_3[Cr(CN)_6]_2x12(H_2O). The former orders ferromagnetically below Tc=90 K, whereas the latter is a ferrimagnet below Tc=230 K. For both, we find significantly large magnetic entropy changes DSm associated to the magnetic phase transitions. Notably, our studies represent the first attempt to look at molecule-based materials in terms of the magnetocaloric effect for temperatures well above the liquid helium range.Comment: 4 pages, 6 figure

Microscopic origins of the ferromagnetic exchange coupling in oxoverdazyl-based Cu(II) complex

The exchange channels governing the experimentally reported coupling constant Jexpt=6 cm−1 value in the verdazyl-ligand based Cu II complex Cu hfac 2 imvdz are inspected using wave function-based difference dedicated configuration interaction calculations. The interaction between the two spin 1/2 holders is summed up in a unique coupling constant J. Nevertheless, by gradually increasing the level of calculation, different mechanisms of interaction are turned on step by step. In the present system, the calculated exchange interaction then appears alternatively ferromagnetic/ antiferromagnetic/ferromagnetic. Our analysis demonstrates the tremendously importance of some specific exchange mechanisms. It is actually shown that both parts of the imvdz ligand simultaneously influence the ferromagnetic behavior which ultimately reaches Jcalc=6.3 cm−1, in very good agreement with the experimental value. In accordance with the alternation of J, it is shown that the nature of the magnetic behavior results from competing channels. First, an antiferromagnetic contribution can be essentially attributed to single excitations involving the network localized on the verdazyl part. In contrast, the ligand-to-metal charge transfer LMCT involving the imidazole moiety affords a ferromagnetic contribution. The distinct nature / of the mechanisms is responsible for the net ferromagnetic behavior. The intuitively innocent part of the verdazyl-based ligands is deeply reconsidered and opens new routes into the rational design of magnetic object

Single chain magnet behaviour in an enantiopure chiral cobalt(II)–copper(II) one-dimensional compound

The self-assembly of an enantiomerically pure, chiral dianionic oxamatocopper(II) complex with cobalt(II) ions leads to neutral oxamato-bridged heterobimetallic chains that combine chirality and slow magnetic relaxation, providing thus the first example of ‘‘chiral single chain magnets (CSCMs).Ruiz Garcia, Rafael, [email protected] ; Lloret Pastor, Francisco, [email protected]

Dialkyl-substituted monoamidinium-templated oxalate-based noncentrosymmetric 2D compounds

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Binuclear heterometallic M(iii)–Mn(ii) (M = Fe, Cr) oxalate-bridged complexes associated with a bisamidinium dication: a structural and magnetic study

International audienceTwo heterometallic oxalate-bridged dinuclear anions associated with a non-H-bond donor bisamidinium cation (Cat 2+), leading to compounds of formula Cat[Mn II (H 2 O) 4 M III (ox) 3 ] 2 Á6H 2 O (M = Fe (1) and Cr (2)), are presented. Their structural analysis reveals that the anion is the combination of a tris(oxalato)metallate(III) moiety with a tetra(aqua)manganese(II) entity. A 3D H-bonded network is formed between the crystallisation and coordination water molecules and the terminal and bridging oxalate ligands. The exchange interaction between both metal ions mediated by the oxalate bridge is À4.9 cm À1 for 1 and +1.6 cm À1 for 2 (H = ÀJS 1 S 2)

Organic radicals, a promising route towards original molecule-based magnetic materials

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Ontology of Law

In this entry for the Encyclopedia of the Philosophy of Law and Social Philosophy, I present the main themes related with the ontology of law. I make a distinction between two ways of conceiving the question "What is Law?": one focused on the nature of legal facts as institutional, or social facts, another focused on the peculiar character of these facts. I make a distinction between three kinds of institutional concepts relevant for an analysis of the legal domain and put forward a three-dimensional theory of legal ontolog

Magneto-chiral dichroism of chiral lanthanide complexes

International audienceMagneto-Chiral Dichroism (MChD) is an enantioselective and polarization independent light-matter interaction shown by magnetized chiral molecules and materials. This phenomenon, predicted in 1984 and experimentally demonstrated in 1997 by studying the differential visible light emission of a chiral EuIII complex, is now attracting the interest of the chemical community working with transition metal and lanthanide-based chiral complexes. This is motivated by both the information on the magnetic, electronic and chiroptical properties that can be retrieved using this unconventional spectroscopic technique and the potential technological applications that can be foreseen, such as the optical readout of magnetic data without the need for polarization-based readout devices. In particular, chiral lanthanide complexes, which intrinsically have high spin-orbit coupling (a key factor to observe MChD), a variety of electronic configurations, a multitude of electronic transitions of different characteristics, variable coordination geometries and different degrees of magnetic anisotropy, represent ideal molecules to investigate MChD in both light absorption and emission in a wide spectral range. This perspective summarizes the studies reported so far in the literature on the MChD of chiral lanthanide complexes and provides some general conclusions that will help the chemical community in designing lanthanide-based systems highly responsive to MChD. Finally, we suggest prospective experiments and studies that are needed to push forward the understanding and the use of this fascinating phenomenon. This Perspective reviews the Magneto-Chiral Dichroism (MChD) investigations performed on chiral lanthanide complexes, highlights the crucial criteria to enhance the MChD performances and presents the main perspectives of this emerging field