Magnetic hysteresis up to 80 kelvin in a dysprosium metallocene single-molecule magnet

Abstract

Single-molecule magnets (SMMs) containing only one metal center may represent the lower size limit for molecule-based magnetic information storage materials. Their current drawback is that all SMMs require liquid-helium cooling to show magnetic memory effects. We now report a chemical strategy to access the dysprosium metallocene cation [(CpiPr5)Dy(Cp*)]+ (CpiPr5, penta-iso-propylcyclopentadienyl; Cp*, pentamethylcyclopentadienyl), which displays magnetic hysteresis above liquid-nitrogen temperatures. An effective energy barrier to reversal of the magnetization of Ueff = 1541 wave number is also measured. The magnetic blocking temperature of TB = 80 kelvin for this cation overcomes an essential barrier toward the development of nanomagnet devices that function at practical temperatures.

Two Four‐Coordinate and Seven‐Coordinate CoII Complexes Based on the Bidentate Ligand 1, 8‐Naphthyridine Showing Slow Magnetic Relaxation Behavior

“…However,f or compound 2,a ss hown in Figure 2(b), the Co II centre is seven-coordinated, with seven Na toms (N1, N2, N3, N5, N6, N7 and N8) from four ligands napy.T he CoÀNb ond lengths for 2 are in the range of 2.122(3)-2.468 (4) .E specially, the bond distance of Co1···N4 is 2.974(4) ,w hich is beyond the scope of CoÀNbond length.Furthermore, the coordination mode of napy in 1 acts as am onodentate mode, while it acts as three bidentate and one monodentate ligand for 2.The coordination geometry of the Co II centre for both complexes 1 and 2 was determined by the continuous shape measures (CShMs) and was calculated by using the SHAPE software. [43] As ar esult, the Co II centrea dopts tetrahedral geometry (T d )w ith the value of 1.561 for complex 1 and adopts capped trigonal prism geometry (C 2v )w ith the value of 4.033 for complex 2 (Figure 2(c) and (d), and Table S3 and S4 in detail).…”

“…[3] And also, SIMs have become the pursuit and drive to obtain the high performance of energy barriers (U eff )a nd blocking temperature (T B )a nd make it easier to potentially applicate. Till now,t he 4f SIM of [(Cp*)Dy(Cp iPr5 )][B(C 6 F 5 ) 4 ]h as arrived at the largest U eff of 2217 Kw ith the highest T B of 80 K, [4] and the 3d SIM of [Co(C-(SiMe 2 Ph) 3 )] 2 also has achieved the large U eff of 647 K. [5] Considerable effortsh ave also been devotedt ot he research of 3d SIMs. [6] The magnetic anisotropyb arrier( U eff )i sd escribed as j D j ·S 2 or j D j ·(S 2 À1/4) for integerspins or half-integer spins, re-spectively.T he magnetic anisotropyo f3 dS IMs is mainly ascribe to the axial and rhombic zero-field splitting (ZFS, Da nd E).…”

“…

For al ong time, the cobalt(II) complex ([Co(napy) 4 ](ClO 4 ) 2 )( napy = 1, 8-naphthyridine) has been considered as an eight-coordinate complex without any structuralp roof. After careful considerations, two complexes [Co(napy) 2 Cl 2 ] (1)a nd [Co(napy) 4 ](ClO 4 ) 2 (2)b ased on the bidentate ligand napy were synthesized and structurally characterized.

…”

Magnetic Relaxation Studies on Trigonal Bipyramidal Cobalt(II) Complexes

“…[4] The success of such an approach allowed reporting large energy barriers and zero-field open magnetic hysteresis loops at high temperatures in Dy III containing complexes. [5,6] Chemicalc ontrol of the crystal field of d 7 transition metal ions in al inear Fe I complex, al inear Co II complex, at etrahedral Co II complex,a nd trigonal bipyramidal Co II complexes led to slow relaxation of the magnetization and to an opening of the hysteresis loop at zero field, even above liquid helium temperature in some cases. [7] Actually,i fw ew ant to employ SMMs for potentiala pplications, mononuclear complexes are excellent candidates because they can be easily manipulated in solution and assembled on surfaces keeping their integrity,inparticular when chelating ligands are used as for the complexes reported here.…”

Drastische Verlangsamung der magnetischen Relaxation durch starke Austauschkopplungen in einem luftstabilen, radikalverbrückten Cobalt(II)‐Einzelmolekülmagneten

“…[3] Die Konstante D eines Spinzustandes ist eine Linearkombination der Nullfeldaufspaltungen der einzelnen Ionen. Derzeit sind Verbindungen mit Dysprosocenium [5][6][7] und niederkoordinierten Übergangsmetallionen [8,9] die geeignetsten Systeme,w obei vierfach koordinierte Cobalt(II)-Komplexe Beispiele der zuletzt genannten Verbindungsklasse darstellen. Derzeit sind Verbindungen mit Dysprosocenium [5][6][7] und niederkoordinierten Übergangsmetallionen [8,9] die geeignetsten Systeme,w obei vierfach koordinierte Cobalt(II)-Komplexe Beispiele der zuletzt genannten Verbindungsklasse darstellen.…”