Search results for "metallacrown"

High-frequency EPR study on Cu4Cu- and Co4Co-metallacrown complexes

2019

Abstract High-frequency/high-field electron paramagnetic resonance studies on two homonuclear 12-MC-4 metallacrown complexes Cu4Cu and Co4Co are presented. For Cu4Cu, our data imply axial-type g-anisotropy with g x = 2.03 ± 0.01 , g y = 2.04 ± 0.01 , and g z = 2.23 ± 0.01 , yielding g = 2.10 ± 0.02 . No significant zero field splitting (ZFS) of the ground state mode is observed. In Co4Co, we find a m S = ± 3 / 2 ground state with g = 2.66 . The data suggest large anisotropy D of negative sign.

Filling the Gap in the Metallacrown Family: The 9‐MC‐3 Chromium Metallacrown

2021

Abstract In this work, we report on a long‐sought missing complex in the metallacrown family. We synthesized and characterized the novel chromium metallacrown (MC) complex {CrIII(μ 2‐piv)3[9‐MCCr(III)N(shi)‐3](morph)3}⋅MeOH (in which shi3−=salicyl hydroxamate, piv=pivalate, and morph=morpholine). The MC with a 9‐MC‐3 cavity of kinetically inert chromium(III) ions was synthesized by a solvothermal reaction. Magnetization measurements reveal a high spin ground state.

Complex formation of copper( ), nickel( ) and zinc( ) with ethylophosphonoacetohydroxamic acid: solution speciation, synthesis and structural charac…

2019

We present herein the thermodynamic and X-ray characterisation of a novel ethyl phosphonohydroxamic acid-based Cu( ) metallacrown, predominating in solution in a broad pH range.

Front Cover: Filling the Gap in the Metallacrown Family: The 9‐MC‐3 Chromium Metallacrown (Chem. Eur. J. 13/2021)

2021

12-MC-4 metallacrowns as versatile tools for SMM research

2015

Abstract The outstanding chemical and structural features of 12-MC-4 metallacrowns allow for versatile applications in magneto-chemical research. Herein, we present three novel approaches. The heterometallic, or magnetic director approach, provides a targeted way to attain unusual high-spin ground states in 12-MC-4 complexes. Further, the first cobalt metallacrowns of salicylhydroxamic acid have been established. They comprise a diamagnetic scaffold which facilitates an engineering of the magnetism of the central guest ion and thus three novel SMMs based on single Co(II) ions have been established. Finally, click chemistry has been utilized to realize a linkage of an azide-functionalized mo…

Enforcement of a high-spin ground state for the first 3d heterometallic 12-metallacrown-4 complex.

2014

Cu(II)(DMF)2Cl2[12-MC(Fe(III)N(Shi))-4](DMF)4·2DMF was synthesized as the first heterometallic transition metal 12-MC-4 complex. The purposeful placement of specific metal ions in the different sites of the metallacrown attains the establishment of a high-spin ground state. Inducing the anticipated superior exchange interactions, the central Cu(II) guest ion averts the common mutual cancellation of the spins, as is observed in the corresponding homometallic compounds.

3d/4f Sandwich Complex Based on Metallacrowns.

2021

A novel lanthanide double-decker complex with nickel metallacrowns (MCs) as coordinating ligands has been synthesized. In the 3d/4f metallacrown complex TbIII[12-MCNiIIN(shi)-4]2, the central lanthanide ion is sandwiched between two [12-MC-4] units, forming an almost ideal square-antiprismatic coordination sphere. The resulting zenithal angles at the central lanthanide ion are smaller than those for previously reported sandwich compounds. Magnetic measurements reveal an energy barrier of 346 K under zero field and up to 585 K under 3200 Oe, the highest reported for metallacrowns with D4d symmetry.

A three-dimensional copper(ii) 12-metallacrown-4 complex with malonomonohydroxamic acid (H3mmh) as a ligand

2011

Slow diffusion of an ethanolic solution of copper(ii) into an aqueous solution of partially deprotonated malonodihydroxamic acid (H4mdh) affords the pentanuclear complex of formula {[K(H2O) 2]2[Cu5(mmh)4]}n (1) (H3mmh = malonomonohydroxamic acid) which is formed by 12-MC-4 metallacrown units with the fifth copper(ii) ion being placed at the center of the square metallacrown unit. The dianionic pentacopper(ii) planar entity interacts with diaquapotassium(i) counterions through the carboxylate-oxygen atoms resulting in a neutral three-dimensional structure. Magnetic susceptibility measurements in the temperature range 1.9-300 K for 1 show the occurrence of relatively strong antiferromagnetic …

Field-Induced Slow Magnetic Relaxation In the First Dy(III)-centered 12-Metallacrown-4 Double-Decker

2019

The reaction of Dy(O2CMe)3·xH2O and Ga(NO3)3·xH2O led to the isolation of (nBu4N)[GaIII8DyIII(OH)4(shi)8] (1). The compound possesses a unique chemical structure enclosing the central magnetic DyIII ion between diamagnetic GaIII-based metallacrown 12-MC-4 ligands. The double-decker complex exhibits field-induced single-molecule magnet (SMM) behaviour with an effective energy barrier (Ueff) of 39 K (27.1 cm−1). Consistent with the observed slow relaxation of magnetization, theoretical calculations suggest a ground state mainly determined by |±11/2> in the easy axis direction.

Solvent-induced high-spin transition in double-decker 3d–4f metallacrowns

2019

Element-specific magnetic spin and orbital magnetic moments of $3d\text{\ensuremath{-}}4f$ double-decker metallacrown molecules have been investigated using x-ray magnetic circular dichroism. The double-decker metallacrowns comprise one rare-earth Gd(III) or Tb(III) ion embedded between two squared scaffolds of four Ni(II) ions. We observe a strong increase of the Ni(II) moments if the molecules are dissolved in methanol, indicating a spin crossover from a low-spin to a high-spin state. In contrast, dichloromethane does not change the spin state. This result is explained by a change of the coordination environment of nickel. The comparison of charge-transfer multiplet calculations with the …