Search results for "Magnetism"

2017

Eight coordination compounds of formulae [FeII(L˙)2][ReIVCl6] (1a), [FeII(L˙)2][ReIVBr6] (1b), [CoII(L˙)2][ReIVCl6]·CH3CN (2a), [CoII(L˙)2][ReIVBr6] (2b), [NiII(L˙)(CH3CN)3][ReIVCl6]·CH3CN (3a), [NiII(L˙)(CH3CN)3][ReIVBr6]·3CH3CN (3b), [CuII(L˙)2][ReIVCl6] (4a) and [CuII(L˙)2][ReIVBr6] (4b), where L˙ is the aminoxyl radical chelating ligand, 4,4′-dimethyl-2,2′-di(2-pyridyl)oxazolidine-N-oxide, have been synthesised. Structural and magnetic studies reveal metal–radical intramolecular antiferromagnetic interactions in the [MII(L˙)2]2+ cations in the iron, cobalt and copper based compounds (1a, 1b, 2a, 2b, 4a and 4b) with the central metal ion low-spin in the case of iron (1a and 1b) and a gra…

Organic chelate-free and azido-rich metal clusters and coordination polymers from the use of Me3SiN3: a new synthetic route to complexes with beautif…

2019

In this Feature Article, we highlight the feasibility of a new, recently developed approach towards the synthesis of high-spin molecules and single-molecule magnets (SMMs). The key to the preparation of such molecular compounds is the organic azide precursor Me3SiN3, which fosters the formation of 3d-metal azido clusters and coordination polymers without requiring the assistance of any organic chelating/bridging group. All the isolated compounds contain metallic cores which are surrounded by end-on bridging N3− groups. Consequently, the reported molecular materials exhibit ferromagnetic exchange interactions between the spin carriers, resulting in the stabilization of the maximum possible s…

Alternating Ferro/Antiferromagnetic Copper(II) Chain Containing an Unprecedented Triple Formato/Hydroxido/Sulfato Bridge.

2016

The first example of a triple formato/hydroxido/sulfato (FHS) bridge for any metal is reported in compound [Cu2(bpym)(OH)(HCO2)(SO4)(H2O)2]·3H2O (1). Its structure shows the presence of alternating triple FHS bridges and 2,2'-bipyrimidine (bpym) ones. Although in the initial synthesis the sulfate anions were introduced accidentally, here we report the rational synthesis and the magnetic properties of this compound. The magnetic properties show that 1 is an alternating ferro/antiferromagnetic (F/AF) chain compound with predominant antiferromagnetic interactions and were fit to an alternating F/AF S = (1)/2 chain with g = 2.103, JAF = -139 cm(-1), and JF = 116 cm(-1) (α = JF/|JAF| = 0.83). Th…

Tri- and tetranuclear heteropivalate complexes with core {Fe2Ni O} (x = 1, 2): Synthesis, structure, magnetic and thermal properties

2019

Abstract The reactions of complex [Fe2Ni(O)(Piv)6(Et2O)(H2O)2] (1) with 1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy) gave the following new coordination compounds: the trinuclear complex [Fe2Ni(O)(Piv)6(phen)H2O]·(C2H5)2O (2), the tetranuclear ones [Fe2Ni2(OH)2(Piv)8(phen)2] (3) and [Fe2Ni2(OH)2(Piv)8(bpy)2] (4), depending on the crystallization conditions. According to single crystal X-ray diffraction data, all the compounds have molecular structures. The Mossbauer spectra of 1–3 correspond to high-spin Fe3+ ions in an octahedral environment consisting of oxygen atoms. The DC magnetic susceptibility studies and quantum-chemical analysis of intra- and intermolecular J pathways using…

Coordination chemistry of N,N′-bis(coordinating group substituted)oxamides: a rational design of nuclearity tailored polynuclear complexes

1999

Abstract The coordinating properties of N , N ′-bis(coordinating group substituted)oxamides have been thoroughly investigated both in aqueous solution and in the solid state. The easy cis – trans isomerization equilibria that they exhibit together with the great variety of N , N ′-substituents which can be used to play on the overall charge, complexing ability and polarity, make them very suitable ligands in designing homo- and heterometallic species. The knowledge of their complex formation in aqueous solution by potentiometry and using the hydrogen ion concentration as a probe, allowed us to settle the basis of a rational design of oxamidate-containing polynuclear species whose nuclearity…

2D and 3D bimetallic oxalate-based ferromagnets prepared by insertion of MnIII-salen type complexes

2013

The syntheses, structures and magnetic properties of the compounds of formulae [Mn((R)-salmen)(CH3OH)(CH3CN)][MnCr(ox)3](CH3OH)0.5(CH3CN)1.25 ((R)-1), [Mn((S)-salmen)(CH3OH)(CH3CN)][MnCr(ox)3](CH3OH)0.5(CH3CN)1.25 ((S)-1), [Mn((R)-salmen)(CH3OH)2][MnCr(ox)3](CH2Cl2)0.375(CH3OH)0.125(H2O)0.375 ((R)-2) and [Mn((S)-salmen)(CH3OH)2][MnCr(ox)3](CH2Cl2)0.375(CH3OH)0.375(H2O)0.125 ((S)-2) (ox = oxalate, salmen2− = N,N′-(1-methylethylene)bis(salicylideneiminate)), [Mn(salpn)(CH3OH)1.5(CH3CN)0.5][MnCr(ox)3](CH3OH)0.82(H2O)0.93 (3) (salpn2− = N,N′-(propane)bis(salicylideneiminate)) and [Mn(saltmen)(CH3OH)(CH3CN)][MnCr(ox)3](CH3OH) (4) (saltmen2− = N,N′-(1,1,2,2-tetramethylethylene)bis(salicylideneimi…

Role of residual water hydrogen bonding in sugar/water/biomolecule systems: a possible explanation fortrehalose peculiarity

2007

We report on the set of experimental and simulative evidences which enabled us to suggest how biological structures embedded in a non-liquid water–saccharide solvent are anchored to the surrounding matrix via a hydrogen bond network. Such a network, whose rigidity increases by decreasing the sample water content, couples the degrees of freedom of the biostructure to those of the matrix and gives place to protein–saccharide–water structures (protein–solvent conformational substates). In particular, the whole set of data evidences that, while the protein–sugar interaction is well described in terms of a water entrapment hypothesis, the water replacement hypothesis better describes the sugar–m…

Synthesis, structure and physical characterization of the dimer {[(bpy)2Co]2(TPOA)}4+ (bpy=2,2′-dipyridyl; H2TPOA=N,N′,N′′,N′′′-tetraphenyl oxalamidi…

2008

Abstract The reaction between CoCl 2 , 2,2′-dipyridyl (bpy) and N , N ′, N ′′, N ′′′-tetraphenyl oxalamidine (H 2 TPOA) in a water/ethanol mixture yields the {[(bpy) 2 Co] 2 (TPOA)} 2+ dimer, that is immediately oxidized in aerobic conditions leading to the Co III species {[(bpy) 2 Co] 2 (TPOA)} 4+ . This cation was isolated as the {[(bpy) 2 Co] 2 (TPOA)}(PF6) 4 ( 1 ) salt, that was characterized by X-ray diffraction on single crystals. The dimer is formed by two Co III ions in octahedral coordination bridged by a deprotonated μ 2 -TPOA ligand. The Co III ions appear in its low spin configuration. Thus, the dimers are essentially diamagnetic, as shown by 1 H NMR and magnetic measurements.

Syntheses, crystal structures and magnetic properties of tricyanomethanide-containing bis(2-pyrimidylcarbonyl)amidate copper(II) complexes

2008

Abstract Three new copper(II) complexes of formulae [Cu(bpcam)(tcm)(H2O)] · 2H2O (1), [Cu(bpcam)(tcm)(H2O)] (2) and [Cu(bpcam)(tcm)]n (3) [bpcam = bis(2-pyrimidylcarbonyl)amidate and tcm = tricyanomethanide] have been prepared and their structures determined by single crystal X-ray diffraction. Complexes 1 and 2 are mononuclear species where each copper atom is five-coordinated in a somewhat distorted square pyramidal environment with a tridentate bpcam ligand and a terminally bound tcm group building the basal plane and a water molecule in the apical position. Compound 3 is a uniform copper(II) chain where the [Cu(bpcam)]+ units are connected through single μ-1,5-tcm bridges which link one…

Double and triple calix[4]arenis connected via the oxygen functions

1990

New macrocyclic molecules are described containing two or three p-tert-butylcalix[4]arene subunits connected via their oxygen atoms. These macrocycles are available by two general methods which are capable of producing assemblies with bridges of varying rigidity and length.