Substantial increase of the ordering temperature for [MnII/MoIII(CN)7]-based magnets as a function of the 3d ion site geometry: example of two supramolecular materials with Tc = 75 and 106 K.

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.

Spin densities in a ferromagnetic bimetallic chain compound: polarized neutron diffraction and DFT calculations.

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.

Metal-organic compounds: a new approach for drug discovery. N1-(4-methyl-2-pyridyl)-2,3,6-trimethoxybenzamide copper(II) complex as an inhibitor of human immunodeficiency virus 1 protease.

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).

Analytical determination of the [Ln-aminoxyl radical] exchange interaction taking into account both the ligand-field effect and the spin-orbit coupling of the lanthanide ion (Ln = DyIII and HoIII).

Numerous compounds in which a paramagnetic LnIII ion is in an exchange interaction with a second spin carrier, such as a transition metal ion or an organic radical, have been described. However, except for GdIII, very little has been reported about the magnitude of the interactions. Indeed, for these ions both the ligand-field effects and the exchange interactions between the magnetic centers become relevant in the same temperature range; this makes the analysis of the magnetic behavior of such compounds more difficult.

Synthesis, Structure, and Magnetism of Mono- and Binuclear Manganese(II) Compounds of Nitronyl Nitroxide Substituted Phosphine Oxides.

Complexes of manganese(II)-containing aminoxyl radical substituted phosphine oxide ligands are reported. The compounds [(o-nitronyl nitroxide-phenyl)diphenylphosphine oxide]bis(hexafluoroacetylacetonato)manganese(II), 3, and bis{[(p-nitronyl nitroxide-phenyl) diphenylphosphine oxide]bis(hexafluoroacetylacetonato)manganese(II)}, 4, prepared by addition of the free radical phosphine oxides to Mn(hfac)(2), were structurally characterized. Complex 3 is mononuclear, containing an O,O-chelating ortho-substituted radical phosphine oxide ligand, while in 4 the para-substituted ligands bridge two Mn(hfac)(2) units to yield a binuclear molecular rectangle.

Two-Step Spin Conversion for the Three-Dimensional Compound Tris(4,4'-bis-1,2,4-triazole)iron(II) Diperchlorate.

The title compound, [Fe(btr)(3)](ClO(4))(2), has been synthesized. The investigation of its magnetic properties has revealed a low-spin <--> high-spin conversion occurring in two steps, each step involving 50% of the Fe(2+) ions. The low-temperature step is very abrupt and occurs with a thermal hysteresis whose width is about 3 K around T(1) = 184 K.

Nature of the Interaction between Ln(III) and Cu(II) Ions in the Ladder-Type Compounds {Ln(2)[Cu(opba)](3)}.S (Ln = Lanthanide Element; opba = ortho-Phenylenebis(oxamato), S = Solvent Molecules).

To date, most of the studies dealing with the magnetic properties of 4f-3d compounds have been limited to the case in which the 4f ion was Gd(III), with a pure spin ground state. For the lanthanide(III) ions with a first-order orbital momentum, the determination of the nature of the 4f-3d interaction is still a challenge. This paper addresses this problem.

Magnetic Transitions in the Cyano-Bridged Bimetallic Ferromagnet Mn(2)(H(2)O)(5)Mo(CN)(7).4.75H(2)O (beta Phase).

Slow diffusion of two aqueous solutions containing K(4)[Mo(CN)(7)].2H(2)O and [Mn(H(2)O)(6)](NO(3))(2), respectively, has afforded two kinds of single crystals whose formulas are Mn(2)(H(2)O)(5)Mo(CN)(7)].4H(2)O (alpha phase) and Mn(2)(H(2)O)(5)Mo(CN)(7)].

Structural, Magnetic, and Photomagnetic Studies of a Mononuclear Iron(II) Derivative Exhibiting an Exceptionally Abrupt Spin Transition. Light-Induced Thermal Hysteresis Phenomenon.

The new spin-crossover compound Fe(PM-BiA)(2)(NCS)(2) with PM-BiA = N-(2-pyridylmethylene)aminobiphenyl has been synthesized. The temperature dependence of chi(M)T (chi(M) = molar magnetic susceptibility and T = temperature) has revealed an exceptionally abrupt transition between low-spin (LS) (S = 0) and high-spin (HS) (S = 2) states with a well-reproducible hysteresis loop of 5 K (T(1/2) downward arrow = 168 K and T(1/2) upward arrow = 173 K). The crystal structure has been determined both at 298 K in the HS state and at 140 K in the LS state.

Ferro- and Antiferromagnetic Exchange in Decamethylbimetallocenes.

With the aim of studying next-neighbor magnetic interactions in polymeric metallocenes the paramagnetic decamethylbimetallocenes (M'M') have been chosen as most simple model compounds. They have been synthesized for vanadium, cobalt, and nickel (to yield V'V', Co'Co', and Ni'Ni', respectively) by starting from dilithium and dithallium salts of the fulvalene dianion. The latter have been characterized by (13)C NMR spectroscopy.

Ferromagnetic Interactions in the Mn(N(3))(4)[Ni(en)(2)(NO(2))](2) Trinuclear Compound. Crystal Structure and Physical Properties.

The goal of this work was to design a ferromagnetically coupled Mn(2+)Ni(2+) species. For this, we attempted to combine nitro-nitrito and end-on azido bridges which are both known to be ferromagnetic couplers. This has led us to the compound of formula Mn(N(3))(4)[Ni(en)(2)NO(2)](2) (en = ethylenediamine).

Polymorphism in Spin Transition Systems. Crystal Structure, Magnetic Properties, and Mössbauer Spectroscopy of Three Polymorphic Modifications of [Fe(DPPA)(NCS)(2)] [DPPA = (3-Aminopropyl)bis(2-pyridylmethyl)amine].

Three polymorphic modifications A-C of [Fe(II)(DPPA)(NCS)(2)], where DPPA = (3-aminopropyl)bis(2-pyridylmethyl)amine is a new tetradentate ligand, have been synthesized, and their structures, magnetic properties, and Mössbauer spectra have been investigated. For polymorph A, variable-temperature magnetic susceptibility measurements as well as Mössbauer spectroscopy have revealed the occurrence of a rather gradual HS if LS transition without hysteresis, centered at about 176 K. The same methods have shown that polymorph B is paramagnetic over the temperature range 4.

Spin Transition in [Fe(DPEA)(NCS)(2)], a Compound with the New Tetradentate Ligand (2-Aminoethyl)bis(2-pyridylmethyl)amine (DPEA): Crystal Structure, Magnetic Properties, and Mössbauer Spectroscopy.

The new spin transition compound [Fe(II)(DPEA)(NCS)(2)], where DPEA [(2-aminoethyl)bis(2-pyridylmethyl)amine] is a new tetradentate ligand, has been synthesized, and its structure, magnetic properties, and Mössbauer spectra have been investigated. The crystal structure has been determined by X-ray diffraction at 298 K. The compound crystallizes in the monoclinic system, space group is P2(1)/c, with Z = 4,a = 9.

Optical Absorption Spectroscopy of the Tetranuclear Compound [Mn{Cu(oxpn)}(3)](ClO(4))(2).2H(2)O (oxpn = N,N'-Bis(3-aminopropyl)oxamide): Complementarity with Magnetic Properties.

The optical absorption spectroscopy of the tetranuclear compound [Mn{Cu(oxpn)}(3)](ClO(4))(2).2H(2)O, with oxpn standing for N,N'-bis(3-aminopropyl)oxamide, has been investigated in the 4-300 K temperature range. The central Mn(II) ion is linked to three Cu(oxpn) complex ligands, so the molecular symmetry may be defined as D(3).

New Metal Oxamates as Precursors of Low-Dimensional Heterobimetallics.

The goal of this work was to synthesize new molecular bricks which could be used as precursors of heterobimetallic low-dimensional compounds. Along this line, four compounds have been synthesized and structurally characterized, namely (NBu(4))(2)[Ni(Cl(2)opba)] (1), (NBu(4))(2)[Cu(Cl(2)opba)] (2), (NBu(4))(5)[Mn(Cl(2)opba)(DMSO)(2)](4) (3), and Cu(en)(2)[Mn(Cl(2)opba)(H(2)O)(2)](2).2DMSO (4), with Cl(2)opba = (4,5-dichloro-o-phenylene)bis(oxamato), NBu(4) = tetra-n-butylammonium, en = ethylenediamine, and DMSO = dimethyl sulfoxide.

Crystal Structure and Magnetic Properties of [Cu(4-Me-3-Nit-trz)(4)](ClO(4))(2), with 4-Me-3-Nit-trz = 2-(3-[4-Methyl-1,2,4-triazolyl])-4,4,5,5-tetramethylimidazoline-1-oxyl 3-Oxide. Intra- and Intermolecular Spin Interactions.

The first two transition metal compounds incorporating triazole-nitronyl-nitroxide radicals as ligands have been synthesized. These compounds are [Cu(4-Me-3-Nit-trz)(4)](ClO(4))(2) (1) and [Ni(4-Me-3-Nit-trz)(4)](ClO(4))(2) (2) with 4-Me-3-Nit-trz = 2-(3-[4-methyl-1,2,4-triazolyl])-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide. Compound 1 crystallizes in the triclinic system, space group P&onemacr;.