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9 records were found.

## Phase Competition and Weak Hydrogen Bonding in the Giant Hysteresis of an S = 1/2 Nickel Dithiolene Complex: Combined Structural and Magnetic Studies

The room-temperature (RT) crystal structure of the colbaltocinium salt of the S = 1/2 nickel dithiolene complex [Ni(tfadt)2]-* (tfadt, 2-trifluoromethylacrylonitrile-1,2-dithiolate) is characterized by uniform one-dimensional spin chains of radical anions, separated from each other by the [Cp2Co]+ cations. Both entities exhibit disorder affecting one CF3 and one Cp ring. Upon being cooled from RT (phase A), two successive structural phase transitions lead to tetramerized spins chains with a low-temperature singlet ground state (phase C) with an associated ordering of the CF3 and Cp moieties. An intermediate tetramerized C′ phase is observed during the cooling sweep, in competition with a dimerized chain structure (phase B) upon warming, affording an apparent giant thermal hysteresis loop of 50 K. The phase succession in temperature at ...

## Order-Disorder Transition Coupled with Magnetic Bistability in the Ferricinium Salt of a Radical Nickel Dithiolene Complex

The ferricinium salt of the anionic, S = 1/2, dithiolene complex [Ni(tfadt)2]- (where tfadt is the asymmetrically substituted 2-(trifluoromethyl)acrylonitrile-1,2-dithiolate) crystallizes at room temperature (rt) into uniform chains of dithiolene complexes, separated by ferricinium cations. Both ionic entities are characterized by disorder affecting one CF3 and one Cp moiety. Above 250 K, this compound displays a Curie-type behavior. At lower temperatures, two first-order transitions around 249 and 137 K are revealed by susceptibility measurements and the observation of hysteresis effects. Crystal structure determinations performed at 230 and 120 K show that the high-temperature transition is associated with an ordering of the CF3 and Cp groups together with a dimerization of the anionic stacks that thus induces a drop of the susceptib...

## Ferromagnetic Interactions in Heterobimetallic Chains Formed through the Secondary Coordination of Dithiolene Complexes

A novel paramagnetic (S = 1/2) copper dithiolene complex based on the tfadt ligand (tfadt: 3-trifluoromethyl-acrylonitrile-2,3-dithiolate) is prepared as its n-Bu4N+ salt and crystallized with [Ni(cyclam)]2+ into infinite, one-dimensional chains through CN***Ni interactions, avoiding any direct (antiferromagnetic) overlap between the dithiolene complexes. An unprecedented ferromagnetic interaction within the heterobimetallic chains between the S = 1/2 [Cu(tfadt)2]2− and the S = 1 [Ni(cyclam)]2+ tectons is observed, despite the fact that the SOMOs of both [Cu(tfadt)2]2− (with dx2−y2 symmetry) and [Ni(cyclam)]2+ (with dx2−y2 and dz2 symmetry) have the same eg symmetry. The experimental exchange interaction deduced from the fit of the magnetic susceptibility (Jexp/kB = +5.0 K) was confirmed by theoretical calculations (Jcalc/kB = +7.3 K),...

## Synthesis, magnetic behaviour, and X-ray structures of dinuclear copper complexes with multiple bridges. Efficient and selective catalysts for polymerization of 2,6-dimethylphenol

The use of a potentially tridentate mono-anionic bridging ligand, 1,3-bis(3,5-dimethylpyrazol-1-yl)-propan-2-ol(bdmpp-H), in assembling new dimeric copper complexes with interesting magnetic properties has been investigated. The reaction of copper hydroxide or copper acetate with phenyl phosphinic acid or diphenyl phosphinic acid in the presence of bdmpp-H produces the dinuclear complexes $[Cu(bdmpp)(ppi)]_2$ (1) and $[Cu(bdmpp)(dppi-H)]_2(dppi)_2$ (2) (ppi-H = phenylphosphinic acid; dppi-H = diphenylphosphinic acid), respectively. The products have been characterized with the help of analytical, thermal, and spectroscopic (IR, UV-vis, and EPR) techniques. Single crystal X-ray diffraction studies of 1 and 2 reveal that the two bdmpp ligands hold together the dimeric copper unit in each complex through $\mu-O$ alkoxide and the pyrazolyl...

## Heterospin systems constructed from [Cu2Ln]3+ and [Ni(mnt)2]1-,2- Tectons: First 3p-3d-4f complexes (mnt = maleonitriledithiolato).

New heterospin complexes have been obtained by combining the binuclear complexes [{Cu(H(2)O)L(1)}Ln(O(2)NO)(3)] or [{CuL(2)}Ln(O(2)NO)(3)] (L(1) = N,N'-propylene-di(3-methoxysalicylideneiminato); L(2) = N,N'-ethylene-di(3-methoxysalicylideneiminato); Ln = Gd(3+), Sm(3+), Tb(3+)), with the mononuclear [CuL(1)(2)] and the nickel dithiolene complexes [Ni(mnt)(2)](q)- (q = 1, 2; mnt = maleonitriledithiolate), as follows: (1)infinity[{CuL(1)}(2)Ln(O(2)NO){Ni(mnt)(2)}].Solv.CH(3)CN (Ln = Gd(3+), Solv = CH(3)OH (1), Ln = Sm(3+), Solv = CH(3)CN (2)) and [{(CH(3)OH)CuL(2)}(2)Sm(O(2)NO)][Ni(mnt)(2)] (3) with [Ni(mnt)2]2-, [{(CH(3)CN)CuL(1)}(2)Ln(H(2)O)][Ni(mnt)(2)]3.2CH(3)CN (Ln = Gd(3+) (4), Sm(3+) (5), Tb(3+) (6)), and [{(CH(3)OH)CuL(2)}{CuL(2)}Gd(O(2)NO){Ni(mnt)(2)}][Ni(mnt)(2)].CH(2)Cl(2) (7) with [Ni(mnt))(2]*-. Trinuclear, almost linear, [...

## OS vs. NS intramolecular nonbonded interactions in neutral and radical cation salts of TTF-oxazoline derivatives: synthesis, theoretical investigations, crystalline structures, and physical properties

Racemic and enantiopure ethylenedithio-tetrathiafulvalene-thiomethyl-oxazoline (EDT-TTF-(SMe)-OX) derivatives have been synthesized. Single-crystal X-ray diffraction analyses reveal the establishment of OS nonbonded interactions, unprecedented in the TTF series, characterized by short SO distances and linear OSMe motifs. Theoretical calculations at the DFT/B3LYP level on a model molecule demonstrate that both possible planar s-trans (OS interaction) and s-cis (NS interaction) conformations are energy minima, separated by an extremely weak energy gap. The energy barrier corresponding to the equilibrium between the two forms has been also estimated from DFT calculations, as well as their relative stability in the radical cation state of the TTF. According to the latter, there is a slight tendency towards the enhancement of the NS interac...

## Heterospin Systems Constructed from [Cu2Ln]3+ and [Ni(mnt)2]1-,2- Tectons: First 3p-3d-4f Complexes (mnt = maleonitriledithiolato)

Unprecedented heterospin complexes have been obtained as crystalline compounds, by combining the binuclear complexes [{CuL1(2)}Ln(O2NO)3] (L1 = N,N’-propylene-di(3-methoxysalicylideneiminato; L2 = N,N’-ethylene-di(3-methoxysalicylideneiminato; Ln = Gd3+, Sm3+, Tb3+), with the mononuclear [CuL1(2)] and the nickel dithiolene complexes [Ni(mnt)2]q– (q = 1, 2; mnt = maleonitriledithiolate), as follows: 1∞[{CuL1}2Ln(O2NO){Ni(mnt)2}]•Solv•CH3CN (Ln = Gd3+, Solv = CH3OH (1), Ln = Sm3+, Solv = CH3CN (2)) and [{(CH3OH)CuL2}2Sm(O2NO)][Ni(mnt)2] (3) with [Ni(mnt)2]2–, and [{(CH3CN)CuL1}2Ln(H2O)][Ni(mnt)2]3•2CH3CN (Ln = Gd3+ (4), Sm3+ (5), Tb3+ (6)) and [{(CH3OH)CuL2}{CuL2}Gd(O2NO){Ni(mnt)2}][Ni(mnt)2]•CH2Cl2 (7) with [Ni(mnt)2]•–Trinuclear, almost linear, [CuLnCu] motifs are found in all the compounds. In the isostructural 1 and 2, two trans cyan...

## Spin relaxation in antiferromagnetic Fe–Fe dimers slowed down by anisotropic DyIII ions

By using Mössbauer spectroscopy in combination with susceptibility measurements it was possible to identify the supertransferred hyperfine field through the oxygen bridges between DyIII and FeIII in a {Fe4Dy2} coordination cluster. The presence of the dysprosium ions provides enough magnetic anisotropy to “block” the hyperfine field that is experienced by the iron nuclei. This has resulted in magnetic spectra with internal hyperfine fields of the iron nuclei of about 23 T. The set of data permitted us to conclude that the direction of the anisotropy in lanthanide nanosize molecular clusters is associated with the single ion and crystal field contributions and 57Fe Mössbauer spectroscopy may be informative with regard to the the anisotropy not only of the studied isotope, but also of elements interacting with this isotope.

## Air oxygenation chemistry of 4-TBC catalyzed by chloro bridged dinuclear copper(II) complexes of pyrazole based tridentate ligands: synthesis, structure, magnetic and computational studies

Four dinuclear bis(mu-Cl) bridged copper(II) complexes, Cu-2(mu-Cl)(2)(L-X)(2)](ClO4)(2) (L-X = N,N-bis(3,5-dimethylpyrazole-1-yl)-methyl]benzylamine with X = H(1), OMe(2), Me(3) and Cl(4)), have been synthesized and characterized by the single crystal X-ray diffraction method. In these complexes, each copper(II) center is penta-coordinated with square-pyramidal geometry. In addition to the tridentate L-X ligand, a chloride ion occupies the last position of the square plane. This chloride ion is also bonded to the neighboring Cu(II) site in its axial position forming an SP-I dinuclear Cu(II) unit that exhibits small intramolecular ferromagnetic interactions and supported by DFT calculations. The complexes 1-3 exhibit methylmonooxygenase (pMMO) behaviour and oxidise 4-tert-butylcatechol (4-TBCH2) with molecular oxygen in MeOH or MeCN to...