Antiferromagnetic Co–Gd Interactions in a Tetranuclear [CoGd]₂ Complex with Low‐Spin Square‐Planar Co Ions – Role of the Singly Occupied 3d Co Magnetic Orbital

Abstract

A trianionic ligand H 3 L [2-hydroxy-N-(2-{[(2-hydroxyphenyl)-methylene]amino}-2-methylpropyl)benzamide] with an inner N 2 O 2 coordination site and an oxygen atom coming from an amide function not involved in this site yields a monoanionic LCo-pipH + complex, in which the Co II ion is in a squareplanar environment and a low-spin state S = 1/2. Further reaction with GdCl 3 ·6H 2 O and tetramethylheptanedione (Hthd) yields a dinuclear Co-Gd complex that self-assembles into a tetranuclear species, as demonstrated by the structural determination of the [LCoGd(thd) 2 (MeOH)] 2 complex. This

Syntheses of Coordination Compounds of (±)-2-Amino-3-(4-Hydroxyphenyl)Propionic Acid, Mixed Ligand Complexes and Their Biological Activities

“…Absorption at 259 and 318 nm is associated with π → π* transition of the ligand [43] [44] Its magnetic moment of 1.066 BM is lower than that expected for Co(II) ion may be ascribed to antiferromagnetism which is due to the interaction between electron spins on neighbouring metal ions or polymerization. This is similar to that obtained for compound 1 [34] [35] [36].…”

Does the Sign of the Cu–Gd Magnetic Interaction Depend on the Number of Atoms in the Bridge?

“…Furthermore, a powerful example is also given by the Co–Gd complexes in which Co II ions are in a high‐spin state and penta‐coordinate or in a low‐spin state and square‐planar coordinate . So the complex [L 3 CoGd(thd) 2 (MeOH)] 2 (thd=tetramethylheptanedionato), in which the Co ion is in a low‐spin state, presents an antiferromagnetic interaction ( J (Co,Gd)=−0.9 cm −1 ) through the double phenoxo bridge . And the complex [L 5 Co(MeOH)Gd(thd)(MeCOO)] 2 , with its penta‐coordinate and high‐spin state Co ion, gives ferromagnetic interactions through the double phenoxo ( J (Co,Gd)=0.40 cm −1 ) and amidato ( J ′(Co,Gd)=0.24 cm −1 ) bridges .…”

“…And the complex [L 5 Co(MeOH)Gd(thd)(MeCOO)] 2 , with its penta‐coordinate and high‐spin state Co ion, gives ferromagnetic interactions through the double phenoxo ( J (Co,Gd)=0.40 cm −1 ) and amidato ( J ′(Co,Gd)=0.24 cm −1 ) bridges . In the low‐spin case the 3d cobalt orbitals are unoccupied and the Co–Gd interaction is antiferromagnetic, whereas the Co–Gd interaction becomes ferromagnetic in the high‐spin case with a single occupation of the 3d orbital . Moreover, the entire set of dinuclear M–Gd complexes in which the M ions do possess singly occupied d orbitals (M=Cu II , Ni II , Co II (high‐spin state), Fe II (high‐spin state), or Mn II (high‐spin state) do present ferromagnetic interactions through the double phenoxo bridge.…”

Square and Butterfly Tetranuclear [Co2Ln2] Clusters Built from the Same Building Blocks but Displaying Different Magnetic Properties: Structural Variation by Means of Solvent and the Radii of Ln3+ Ions

“…Tetranuclear [M 2 Ln 2 ] complexes display diverse topology such as tetrahedron, line, “butterfly”, and μ 4 ‐oxygen‐bridged square‐planar,6–8 and are good models to gain more insight into the magnetic properties of 3d–4f complexes. A butterfly core is characterized by its tetranuclear metal skeleton bridged by two oxygen atoms (maybe O 2– , OH – , and alkoxide oxygen) with μ 3 ‐κ 1 :κ 1 :κ 1 connectivity 6,9. Although such a structure has been thoroughly reported in transition‐metal chemistry, similar 3d–4f complexes are rare 6,10–13.…”

“…A butterfly core is characterized by its tetranuclear metal skeleton bridged by two oxygen atoms (maybe O 2– , OH – , and alkoxide oxygen) with μ 3 ‐κ 1 :κ 1 :κ 1 connectivity 6,9. Although such a structure has been thoroughly reported in transition‐metal chemistry, similar 3d–4f complexes are rare 6,10–13. In these heterometallic complexes, 4f ions usually act as the “wings” and 3d ions as the “body” of the butterfly except for [Dy 2 Cu 2 (OH) 2 ]11 and [Ln 2 Fe 2 (OH) 2 ] (Ln = Y 3+ , Dy 3+ , and Ho 3+ ),12 in which two Ln 3+ ions are used as the “body”.…”