The goal of this paper is to review briefly our endeavors to increase the dimensionality of molecular-based bimetallic species. We will successively speak about antiferromagnetically coupled Mn(II) Cu(II) binuclear species, ferrimagnetic chain compounds exhibiting three-dimensional metamagnetic or ferromagnetic behavior, two-dimensional compounds, and finally a three-dimensional compound with a fully interlocked structure. We will also emphasize the importance of the local anisotropy of the spin carriers in the coercivity of the molecular-based magnets.

Angewandte ChemieVolume 94, Issue 8 p. 647-648 Zuschriften Ferromagnetische Wechselwirkung zwischen orthogonalen „magnetischen”︁ Orbitalen in zweikernigen CuIICrIII-Komplexen Yves Journaux, Yves Journaux Laboratoire de Spectrochimie des Eléments de Transition ERA 672, Université de Paris Sud F-91405 Orsay (Frankreich)Search for more papers by this authorProf. Dr. Olivier Kahn, Prof. Dr. Olivier Kahn Laboratoire de Spectrochimie des Eléments de Transition ERA 672, Université de Paris Sud F-91405 Orsay (Frankreich)Search for more papers by this authorHubert Coudanne, Hubert Coudanne Laboratoire de Spectrochimie des Eléments de Transition ERA 672, Université de Paris Sud F-91405 Orsay (Frankreich)Search for more papers by this author Yves Journaux, Yves Journaux Laboratoire de Spectrochimie des Eléments de Transition ERA 672, Université de Paris Sud F-91405 Orsay (Frankreich)Search for more papers by this authorProf. Dr. Olivier Kahn, Prof. Dr. Olivier Kahn Laboratoire de Spectrochimie des Eléments de Transition ERA 672, Université de Paris Sud F-91405 Orsay (Frankreich)Search for more papers by this authorHubert Coudanne, Hubert Coudanne Laboratoire de Spectrochimie des Eléments de Transition ERA 672, Université de Paris Sud F-91405 Orsay (Frankreich)Search for more papers by this author First published: August 1982 https://doi.org/10.1002/ange.19820940827Citations: 6AboutPDF ToolsRequest permissionAdd to favorites ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume94, Issue8August 1982Pages 647-648 This is the German version of Angewandte Chemie. Note for articles published since 1962: Do not cite this version alone. Take me to the International Edition version with citable page numbers, DOI, and citation export. We apologize for the inconvenience. RelatedInformation

Abstract[Cu(hyetrz)3](CF3SO3)2·H2O [hyetrz = 4‐(2′‐hydroxyethyl)‐1,2,4‐triazole] represents the first structurally characterised ferromagnetically coupled CuII chain compound containing triple N1,N2‐1,2,4‐triazole bridges. catena‐[μ‐Tris{4‐(2′‐hydroxyethyl)‐1,2,4‐triazole‐N1,N2}copper(II)] bis(trifluoromethanesulfonate) hydrate (C14H23F6S2O10CuN9) crystallises in the triclinic space group P$\bar 1$ , a = 13.54(3), b = 14.37(3), c = 15.61(4) Å, α = 95.9(1), β = 104.9(1), γ = 106.5(1)°, V = 2763(11) Å3, Z = 4 (CuII units). The CuII ions are linked by triple N1,N2‐1,2,4‐triazole bridges yielding an alternating chain with Cu1−Cu2 = 3.8842(4) Å and Cu2−Cu3 = 3.9354(4) Å. Analysis of the magnetic data according to a high‐temperature series expansion gives a J value of +1.45(3) cm−1. The nature and the magnitude of the ferromagnetic exchange have been discussed on the basis of the structural features. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

[Cu(hyetrz)(3)](CF3SO3)(2)(H2O)-H-. thyetrz = 4-(2'-hydroxyethyl)-1,2,4-triazole] represents the first structurally characterised ferromagnetically coupled Cull chain compound containing triple N-1,N-2-1,2,4-triazole bridges. catena-[mu-Tris(4-(2'-hydroxyethyl)-1,2,4-triazole-N-1,N-2}copper(II)] bis(trifluorome-thanesulfonate) hydrate (C14H23F6S2O10CuN9) crystallises in the triclinic space group P1, a = 13,54(3), b = 14.37(3), c = 15.61(4) Angstrom alpha = 95,9(1), beta = 104.9(1) gamma = 106.5(1)degrees V = 2763(11) Angstrom(3), Z = 4 (Cu-II units), The Cu-II ions are linked by triple N-1,N-2-1,2,4-triazole bridges yielding an alternating chain with Cu1-Cu2 = 3,8842(4) A and Cu2-Cu3 = 3.9354(4) Angstrom. Analysis of the magnetic data according to a [high-temperature series expansion gives a J value of +1 45(3) cm. The nature and the magnitude of the ferromagnetic exchange have been discussed on the basis of the structural features. (C) Wiley-VCH Verlag GmbH & Co, KGaA, 69451 Weinheim, Germany, 2003.

Two molecule-based magnets, [Mn(2)(tea)Mo(CN)(7)].H(2)O, 1, and [Mn(2)(tea)Mo(CN)(7)], 2 (tea stands for triethanolamine), formed with the 4d ion building block, [Mo(CN)(7)](4)(-), Mn(II) ions, and an additional ligand, tea, have been prepared and structurally characterized by single-crystal X-ray analyses. Whereas 1 is obtained by a self-assembling process in solution, compound 2 is quantitatively formed through a smooth thermal treatment of 1. Their magnetic properties revealed that these compounds exhibit magnetic ordering at T(c) = 75 and 106 K respectively for compounds 1 and 2. The difference for their critical temperature is attributed to the geometry of the coordination sphere of a Mn(II) site found to be square-pyramidal for 1 and tetrahedral for 2.

Electron paramagnetic resonance (EPR) investigations were carried out on two bimetallic molecular magnets (NBu4)2Co2[Cu(opba)]3·S, where S=3DMSO·3H2O and 2H2O, known to exhibit long-range magnetic order below 32 and 34 K, respectively, in the temperature range 300–15 K. Temperature dependence of the intensity of the EPR signal arising from Cu2+ in these compounds showed a rapid decrease in intensity upon cooling below 65 K, which was accompanied by a disappearance of the super-hyperfine structures, observed on the Cu2+ signal at higher temperatures, pointing to a Co2+Cu2+ spin–spin interaction following the slowing down of Co2+ spin–lattice relaxation. The appearance of a new signal at zero field (ZFS) below 40 K is attributed to the onset of long-range magnetic ordering in both the compounds.

The use of metal-organic complexes is a potentially fruitful approach for the development of novel enzyme inhibitors. They hold the attractive promise of forming stronger attachments with the target by combining the co-ordination ability of metals with the unique stereoelectronic properties of the ligand. We demonstrated that this approach can be successfully used to inhibit the protease of the human immunodeficiency virus (type 1). Several ligands bearing substituents designed to interact with the catalytic site of the enzyme when complexed to Cu2+ were synthesised. The inhibition pattern of the resulting copper(II) complexes was analysed. We showed that the copper(II) complex of N1-(4-methyl-2-pyridyl)-2,3,6-trimethoxybenzamide (C1) interacts with the active site of the enzyme leading to competitive inhibition. On the other hand, N2-pyridine-amide ligands and oxazinane carboxamide ligand were found to be poor chelators of the cupric ion under the enzymatic assay conditions. In these cases, the observed inhibition was attributed to released cupric ions which react with cysteine residues on the surface of the protease. While unchelated metal cations are not likely to be useful agents, metal chelates such as C1 should be considered as promising lead compounds for the development of targeted drugs.

The spin population distribution in the ferromagnetically coupled hetero-bimetallic chain compound [MnNi(NO(2))(4)(en)(2)] (en = 1,2-ethanediamine) has been investigated by means of polarized neutron diffraction experiments, and the results compared with those from theoretical estimates obtained via calculations based on density functional theory on dinuclear molecular models of the chain. The spin distributions obtained from experiment and from theory are consistent and reflect a larger spin delocalization from the Ni atom due to the more covalent character of the Ni-N bonds compared to the Mn-O ones. Also a nearly isotropic spin distribution is observed for the more ionic d(5) Mn(2+) ion and a clearly anisotropic distribution for the d(8) Ni(2+) ion. The use of dinuclear molecular models for the calculation of the exchange coupling constant between Ni and Mn provide upper and lower limits (+17.6 and -4.2 cm(-)(1)) for the experimentally determined value (+1.3 cm(-)(1)), depending on how the missing part of the chain is simulated, but yield essentially the same spin distribution. The Mn(II)-Ni(II) weak ferromagnetic coupling in the chain is interpreted in a spin delocalization mechanism as resulting from the weakness of the overlap between the magnetic orbitals centered on nickel and those centered on manganese which are only weakly delocalized on the ligands.

We report the synthesis of the compound [Mn(tacn)]2[Mo(CN)7]·5H2O, another addition to the family of MnMo-heptacyanates. It is obtained by capping the Mn(II) with the ligand ‘tacn’ (triazacyclononane) and reacting it with the [MoIII(CN)7]4− precursor. It exhibits ferromagnetic behavior below 90 K.

The syntheses and structural and physical characterization of the compounds [Cu(bipy)2]2[Mo(CN)8]·5H2O· CH3OH (1) with bipy = 2,2'-bipyridine and MII2[MoIV(CN)8]·xH2O (2 with M = Cu, x = 7.5; 3 with M = Mn, x = 9.5) are presented. 1 crystallizes in the triclinic space group P1̄ (a = 11.3006(4) Å, b = 12.0886(5) Å, c = 22.9589(9) Å, α = 81.799(2)°, β = 79.787(2)°, γ = 62.873(2)°, Z = 2). The structure of 1 consists of neutral trinuclear molecules in which a central [Mo(CN)8]4- anion is linked to two [Cu(bipy)2]2+ cations through two cyanide bridges. 2 crystallizes poorly, and hence, structural information has been obtained from the wide-angle X-ray scattering (WAXS) technique, by comparison with 3 and FeII2(H2O)4[MoIV(CN)8]·4H2O whose X-ray structure has been previously solved. 2, 3, and FeII2(H2O)4[MoIV(CN)8]·4H2O form extended networks with all the cyano groups acting as bridges. The magnetic properties have shown that 1 and 2 behave as paramagnets. Under irradiation with light, they exhibit important modifications of their magnetic properties, with the appearance at low temperature of magnetic interactions. For 1 the modifications are irreversible, whereas they are reversible for 2 after cycling in temperature. These photomagnetic effects are thought to be caused by the conversion of MoIV (diamagnetic) to MoV(paramagnetic) through a photooxidation mechanism for 1 and a photoinduced electron transfer in 2. These results have been correlated with the structural features.

The synthesis and crystal structure of a novel one-dimensional Cu(II) compound [Cu(1,2-bis(tetrazol-1-yl)ethane)3](ClO4)2 are described. The single-crystal X-ray structure determination was carried out at 298 K. The molecular structure consists of a linear chain in which the Cu(II) ions are linked by three N4,N4′ coordinating bis(tetrazole) ligands in syn conformation. The Cu(II) ions are in a Jahn–Teller distorted octahedral environment (Cu(1)N(11)=2.034(2) Å, Cu(1)N(21)=2.041(2) Å and Cu(1)N(31)=2.391(2) Å). The Cu⋯Cu separations are 7.420(3) Å.

Single-crystal magnetization, heat capacity and neutron diffraction studies of the bimetallic regular chain MnIINiII(NO2)4(en)2 (en = ethylenediamine) are presented. This compound exhibits ferromagnetic interactions between the Mn and Ni ions within the chains. The onset of long-range antiferromagnetic ordering below TN = 2.45 K is associated with weaker antiferromagnetic interactions between neighbouring chains. The magnetization studies reveal an easy axis anisotropy of the susceptibility at low T with a preferred orientation ∥c. This anisotropy results from the low local symmetry around the Mn ions. Below TN, the susceptibility drop observed for H∥c is much larger than for H⊥c, pointing to a moment orientation parallel to the c axis in the ordered state. At 1.8 K, the metamagnetic transition is observed to proceed in two steps for H∥c, with Hc1 = 1.5 kOe and Hc2 = 2.5 kOe. This is associated with the familiar spin flop state at the intermediate field values. For H⊥c, at 1.8 K the ordered state is suppressed only in fields larger than 6 kOe. \mbox{Low-$T$} heat capacity data exhibit a pronounced anomaly at the antiferromagnetic transition. The reduced entropy at TN points to significant short-range ordering effects above TN associated with the ferromagnetic intrachain interactions. The ordered magnetic structure is an antiferromagnetic stacking of ferromagnetic sheets.

This paper concerns the chemistry and the magnetic properties of a family of compounds with a fully interlocked structure. The general formula is [Etrad]2[M2{Cu(opba)}3]·S, with M=Mn2+, Co2+, Mg2+, Ni2+, where Etrad stands for a radical cation, and opba stands for ortho-phenylenebis(oxamato). The structure consists of two interpenetrating graphite-like networks with edge sharing hexagons. The magnetic properties of the four compounds have been investigated in detail. The Mg2+ derivative behaves as a paramagnet with weak ferromagnetic interactions between Cu2+ and Etrad+ ions. The three other compounds are molecule-based magnets with a spontaneous magnetization below 22.8 K for the Mn2+ derivative, 28 K for the Ni2+ derivative and 37 K for the Co2+ derivative. While the Mn2+ derivative is a soft magnet, the Ni2+ and Co2+ derivative display hysteresis loops, with coercive fields higher than 1 kOe depending on the temperature and the size of the particles. The Ni2+ derivative presents also an inversion of the magnetic poles as the temperature varies under a small external field. For higher field, the magnetization reverses two times. These original results can be properly reproduced using the molecular-field theory adapted to the system and the magnetic anisotropy.

The synthesis and characterization of the new spin crossover mononuclear complex [Fe-II(DPEA)(bim)](ClO4)2 .0.5H(2)O, where DPEA = (2-aminoethyl)bis(2-pyridylmethyl)amine and bim. = 2,2-bisimidazole, are reported. Variable-temperature magnetic susceptibility measurements (77-295 K) reveal the occurrence of a two-step spin transition. Two steps on the magnetic curve are separated by an inflection point at 200 K, corresponding to about 50% of the complexes that have undergone a thermal spin transition. The first step is centered at 171 K and the second one at 218 K. Mossbauer spectroscopy and X-ray analysis show that the profile of the magnetic curve is a consequence of the presence of two inequivalent iron(II) molecules in the crystal lattice. The crystal structure was resolved at 293 K (high-spin form) and at 123 K (low-spin form). Both spin-state isomers belong to the monoclinic space group P2(1)/c (Z = 4). The main differences between high-spin and low-spin isomers are found in the geometry of the [FeN6] core, the shorter Fe-N distances are seen at lower temperatures. Two inequivalent HS molecules at lattice sites I and 2 successively undergo a thermal spin transition. The analysis of the mean Fe-N distances for functionally different nitrogen donor atoms show that the two steps of the spin transition can be assigned to the inequivalent lattice sites. The gradual character of the spin transition at both lattice sites is accounted for in terms of intermolecular H-bonding via the perchlorate ions, At 10 K the light-induced excited spin state trapping (LIESST) effect is observed within the SQUID magnetometer cavity, Two critical temperatures T-c(LIESST) were recorded (36 K and 21 K) and are attributed to the lattice sites I and 2.

Previous investigations of the potential of metal–organic compounds as inhibitors of human immunodeficiency virus type I protease (HIV-1 PR) showed that the copper(II) complex diaqua [bis(2-pyridylcarbonyl)amido] copper(II) nitrate dihydrate and the complex bis[N2-(2,3,6-trimethoxybenzyl)-4-2-pyridinecarboxamide] copper(II) behaved as inhibitors of HIV-1 PR. In a search for similar readily accessible ligands, we synthesised and studied the structural properties of N2-(2-pyridylmethyl)-2-pyridinecarboxamide (L) copper(II) complexes. Three different crystal structures were obtained. Two were found to contain ligand L simultaneously in a tridentate and bidentate conformation [Cu(LtriLbi)]. The other contained two symmetry-related ligands, coordinated through the pyridine nitrogen and the amide oxygen atoms [Cu(Lbi)2]. A search of the Cambridge Structural Database indicated that Ltri resulting from nitrogen bound amide hydrogen metal substitution is favoured over chelation through the amide oxygen atom. In our case, we calculated that the conformation of Ltri is 11 kcal/mol more favourable than that of Lbi. ESI-MS experiments showed that the Cu(Lbi)2 structure could not be observed in solution, while Cu(LtriLbi)-related complexes were indeed present. The lack of protease inhibition of the pyridine carboxamide copper(II) complexes was explained by the fact that the Cu(LbiLtri) complex could not fit into the HIV-1 active site.

A series of novel polymeric compounds of formula [M(btzb)(3)][ClO4](2) (M-II=Fe, Ni or Cu) with btzb=1,4-bis(tetrazol-1-yl)butane have been prepared and their physical properties investigated. The btzb ligand has been prepared and its crystal structure determined, together with a tentative crystal structure of the 3-D compound [Fe(btzb)(3)][ClO4](2). The model of the latter shows two symmetry-related, interpenetrating Fe-btzb networks in which the iron(II) ions approach each other as close as 8.3 and 9.1 Angstrom. This supramolecular catenane undergoes a sharp thermal spin transition around 160 K with hysteresis (20 K) along with a pronounced thermochromic effect. The spin crossover behaviour has been followed by magnetic, DSC, optical spectroscopy and Fe-57 Mossbauer spectroscopy measurements. Irradiation with green light at low temperature leads to population of the metastable high-spin state for the thermally active iron(II) ions. The nature of the spin crossover behaviour has been discussed in detail.

The compounds Ln2[Cu(opba)]3·S (where opba stands for ortho-phenylenebis(oxamato) and S for solvent molecules) with Ln=Tb, Dy, Ho are spin ladder molecular magnets. Specific heat measurements down to 0.1K show that these compounds undergo three-dimensional magnetic ordering, with TC=0.81K and TC=0.74K for the Tb- and the Dy-containing compounds, respectively. For the Ho-containing compound, only the high temperature tail of the λ anomaly is detected by a specific heat measurement. In combination with a low-temperature susceptibility measurement (not presented here), it can be concluded that its ordering temperature is between 0.05 and 0.1K. These results are compared with the magnetic properties of the isostructural compound Gd2[Cu(opba)]3·S, which is a ferromagnet.

The first two-dimensional molecular material Nd(III)−Cu(II) has been synthesized by reaction in DMF of [Cu(opba)]2- and Nd3+. The compound {Nd2[Cu(opba)0.5(ox)]3·9DMF}·4.5DMF has been structurally characterized. Its crystalline structure can be described as the superposition of honeycomb-like molecular motifs. This material exhibits a quasi nonmagnetic ground state at low temperature.

This article derails the local spin density determination in the cyano-bridged, two-dimensional, molecular based magnet K2Mn3(H2O)(6)[Mo(CN)-](2). 6H(2)O (T-2 = 39 K). The crystal structure. determined at room temperature by X-ray diffraction. nas redetermined at 50 K using unpolarised neutron diffraction. The importance of intermolecular hydrogen bonding interactions is clearly demonstrated in this study. previously characterised with X-rays. The local spin density was determined from polarised neutron diffraction data at 4 K with an applied field of 3 T. Positive spin densities were observed on the manganese sites, consistent with high-spin d(5) ions in octahedral fields. whilst a negative spin density was found on the molybdenum sites. signifying delocalisation onto the cyano ligands. The alternating sign of the spin populations on the metal sites. suggests that the primary Mo-III-Mn-II interactions are antiferromagnetic in nature and rile delocalisation onto the cyano-bridges clearly demonstrates the role of the ligand bridges in the magnetic exchange pathway. (C) 2001 Academic des sciences/Editions scientifiques et medicales Elsevier SAS.