A low spin manganese(IV) nitride single molecule magnet

Structural, spectroscopic and magnetic methods have been used to characterize the tris(carbene) borate compound PhB(MesIm)(3)Mn equivalent to N as a four-coordinate manganese(IV) complex with a low spin (S = 1/2) configuration. The slow relaxation of the magnetization in this complex, i.e. its single-molecule magnet (SMM) properties, is revealed under an applied dc field. Multireference quantum mechanical calculations indicate that this SMM behavior originates from an anisotropic ground doublet stabilized by spin-orbit coupling. Consistent theoretical and experiment data show that the resulting magnetization dynamics in this system is dominated by ground state quantum tunneling, while its temperature dependence is influenced by Raman relaxation

Cyanomethylene-bis(phosphonate)-Based Lanthanide Complexes: Structural, Photophysical, and Magnetic Investigations

10 pagesInternational audienceThe syntheses, structural investigations, magnetic and photophysical properties of a series of 10 lanthanide mononuclear complexes, containing the heteroditopic ligand cyanomethylene-bis(5,5-dimethyl-2-oxo-1,3,2λ5-dioxa-phosphorinane) (L), are described. The crystallographic analyses indicate two structural types: in the first one, [LnIII(L)3(H2O)2]*H2O (Ln = La, Pr, Nd), the metal ions are eight-coordinated within a square antiprism geometry, while the second one, [LnIII(L)3(H2O)]*8H2O (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er), contains seven-coordinated LnIII ions within distorted monocapped trigonal prisms...

Coexistence of long-range antiferromagnetic order and slow relaxation of the magnetization in the first lanthanide complex of a 1,2,4-benzotriazinyl radical

The first lanthanide complex of a 1,2,4-benzotriazinyl radical (1), Dy(1)(tbacac)3 (2, tbacac = 2,2,6,6-tetramethyl-3,5-heptane-dionato), was synthesised and found to have an antiferromagnetically ordered ground state with a metamagnetic phase diagram and a critical field of 0.91 T at 1.85 K. The application of a small dc field revealed the single-molecule magnet behaviour of 2, illustrating the coexistence of long-range antiferromagnetic order and slow relaxation of the magnetization.peerReviewe

From a mononuclear NiII precursor to antiferromagnetically coupled trinuclear double-stranded helicates

Reaction of the mononuclear NiII complex [Ni{2-Py(6-NH 2)NHC(S)NP(S)(OiPr)2}2] with different salicylaldehydes leads to new antiferromagnetically coupled trinuclear double-stranded helicates 1-3, where NiII metal ions are coordinated by two bis-anionic thiourea ligands and two deprotonated molecules of the corresponding aldehyde. © 2013 The Royal Society of Chemistry

Magnetic blocking in extended metal atom chains: a pentachromium(II) complex behaving as a single-molecule magnet

Compound [Cr5(tpda)4Cl2] (H2tpda = N2,N6-di(pyridin-2-yl)pyridine-2,6-diamine), an Extended Metal Atom Chain complex featuring two quadruply-bonded {Cr2} units, exhibits field-induced slow relaxation of its magnetization arising from the terminal chromium(II) ion and provides the first example of a chromium(II)-based Single-Molecule Magnet

A linear metal-metal bonded tri-iron single-molecule magnet

The linear trinuclear complex cation [Fe3(DpyF)4] 2+ was prepared as [Fe3(DpyF)4](BF4)22CH3CN. With large Fe–Fe distances of 2.78 Å, this complex demonstrates intramolecular ferromagnetic coupling between the anisotropic FeII centers (J/kB = +20.9(5) K) giving an ST = 6 ground state and exhibits single-molecule magnet properties

Materials Today: Proceedings

The glasses with formula 2AO-CoO-B2O3 (A = Ba, Sr) were prepared successfully by the conventional melting method. The amorphous state of these glasses was confirmed by X-ray diffraction. The thermal investigation conducted by differential scanning calorimetry (DSC) confirms their vitreous nature. Infrared spectroscopy approves the existence of both BO3 and BO4 groups. The transmittance shows the different optical transitions of the Co2+ in 2AO-CoO-B2O3 (A = Ba, Sr) glasses. The calculated gap energy shows that these glasses have wide-band-gaps and can be classified as semiconductor materials. The magnetic measurements were studied as a function of the field and temperature. The predominant interactions in these glasses are antiferromagnetic

Structural diversity and magnetic properties of copper(II) quinaldinate compounds with amino alcohols

The reactions between [Cu(quin)$_2$(H$_2$O)] (quin$^–$ = the anionic form of quinoline-2-carboxylic acid) and a series of aliphatic amino alcohols have yielded structurally very diverse copper(II) complexes, labelled a–g. Single-crystal X-ray structure analysis has revealed either intact amino alcohol molecules or amino alcoholate ions serving as ligands. In type a complexes, the amino alcohols are bound in a monodentate manner via NH$_2$. Engagement of both functional groups in coordination was observed for types b and e (a bidentate chelating mode) and type c (a bidentate bridging one) complexes. In view of the strong bidentate chelating coordination of quinaldinate in [Cu(quin)$_2$(H$_2$O)], the formation of homoleptic amino alcohol complexes e was not anticipated. Equally surprising was the transformation of a mononuclear starting material into a one-dimensional (1D) coordination polymer, [Cu(quin)$_2$]$_n$ (g). Spontaneous deprotonation of some amino alcohols and coordination of, thus formed, amino alcoholates via both donors also took place. Dinuclear complexes (d) contained two bridging amino alcoholates, whilst bidentate chelating mode was observed for type f. Interestingly, the dinuclear complex exists as two isomers which differ in the position of quinaldinates with respect to the Cu(μ-OR)$_2$Cu core. DFT calculations on isolated syn- and anti-[Cu$_2$(quin)$_2$(3a1pO)$_2$] (3a1pO$^–$ = anion of 3-amino-1-propanol) have shown the syn isomer to be more stable. The explanation lies in the intramolecular π⋯π stacking of quinaldinates, possible only in this isomer. Magnetic susceptibility measurements revealed antiferromagnetic interactions between S = 1/2 copper(II) spins in all the studied compounds except in [Cu(quin)$_2$]$_n$ (g) for which weak ferromagnetic couplings are detected

Temperature dependence of the spin state and geometry in tricobalt paddlewheel complexes with halide axial ligands

Trinuclear cobalt paddlewheel complexes, [Co3(dpa)4X2] (dpa = the anion of 2,2'-dipyridylamine, X = Cl-, Br-, -NCS-, -CN-, (NC)2N-), are known to demonstrate a thermally-induced spin-crossover (SCO). Despite a wealth of structural and magnetic information about such complexes, the role of the axial ligand on the characteristic SCO temperature (T1/2) remains ambiguous. The situation is complicated by the observation that the solid state geometry of the complexes, symmetric or unsymmetric, with respect to the central cobalt ion, also appears to influence the SCO behavior. In order to seek trends in the relationship between the nature of the axial ligand, geometry and magnetic properties, we have prepared the first examples of tricobalt paddlewheel complexes with axial fluorido and iodido ligands, as well as two new chlorido and bromido solvates. Their SCO properties are discussed in the context of an examination of previously reported chlorido and bromido adducts. The main conclusions are: (1) T1/2 values follow the trend I- < Br- ≈ Cl- < F-; (2) while the molecular geometry is predominantly guided by crystal packing for the Cl-, Br- and I- derivatives, the presence of an axial fluoride may favor a more symmetric core; (3) the magnetic characterization of a second example of an unsymmetric complex supports the observation that they display dramatically lower T1/2 values than their symmetric analogues; and (4) SCO in crystallographically symmetric compounds apparently occurs without loss of molecular or crystallographic symmetry, while a gradual geometric transformation linking the temperature dependence of quasi-symmetric to unsymmetric in crystallographically unconstrained compounds was found

Partial Nitrogen Atom Transfer: A New Synthetic Tool to Design Single-Molecule Magnets

Incomplete nitrogen atom transfer from the iron(IV) nitride complex PhB(MesIm)3Fe=N to the vanadium-(III) complexV(Mes)3(THF) quantitatively provides the bimetallic complex PhB(MesIm)3Fe-N=V(Mes)3. Structuraland spectroscopic characterizations reveal that the nitride ligand forms a linear bridge between V(V) and high-spin Fe(II) metalions, confirming that atom transfer is accompanied by electron transfer. In the presence of an applied dc field, the complexdisplays slow relaxation of the magnetization, revealing its singlemolecule magnet properties with an estimation of the energybarrier at about 10 K. This complex establishes a synthetic principle for the assembly of paramagnetic complexes bridged by nitride ligands