Heterometallic Pentanuclear [Ni₄Ln] (Ln^III = Gd, Tb, Dy, Ho) Complexes: Accidental Orthogonality Leading to Ferromagnetic Interactions

Abstract

The reaction of 6‐formyl‐2‐(hydroxymethyl)‐4‐methylphenol (LH2) with NiII and LnIII salts afforded a series of heterometallic pentanuclear compounds [Ni4Ln(L)4(OAc)2(MeOH)4](NO3)(MeOH) [LnIII = Gd (1), Dy (2), Tb (3), Ho (4)]. Four dianionic L2– ligands and two acetate anions hold together four NiII and one LnIII ion to form a Ni4Ln core possessing a distorted tetrahedral geometry. All the NiII ions are hexacoordinate (6 O) with a distorted octahedral geometry whereas the LnIII ion is octacoordinate (8 O) with a distorted square‐antiprism geometry. All the NiII ions are connected to the central LnIII ion through μ2 bridging of one deprotonated phenolic oxygen and two deprotonated alkoxy oxygen atoms. The magnetic properties of 1–4 were investigated in the temperature range 2–300 K. The magnetic properties of 1 were fitted by using a Hamiltonian containing isotropic exchange, NiII local zero‐field‐splitting, and Zeeman effects (Ĥ = Ĥexchange + Ĥzfs + Ĥzeeman). The molecular structures of 1–4 reveal that the Ni–O–Ln angle is around 89° whereas the Ni–O–Ni angle is about 96°. Because of this accidental orthogonality, ferromagnetic interactions between the nearest‐neighbor NiII ions and between NiII and LnIII ions have been observed. The observed J values are 0.34 and 1.88 cm–1 between GdIII–NiII and NiII–NiII, respectively.

Pentanuclear Spirocyclic Ni4Ln Derivatives: Field Induced Slow Magnetic Relaxation in the Dysprosium and Erbium Analogues

“…It is well known that multi‐compartmental Schiff base ligands are an excellent host to assemble 3d‐4f hybrid molecules , . The multisite coordinating Schiff base ligand LH 3 was synthesized by condensation reaction in methanol of 2‐(hydroxymethyl)‐6‐carbaldehyde‐4‐methylphenol, with 2‐aminophenol. Recently, we and others, have utilized the above‐mentioned aldehyde or corresponding multi‐compartmental Schiff base ligands to ensemble various 3d‐4f heterometallic complexes .…”

“…The multisite coordinating Schiff base ligand LH 3 was synthesized by condensation reaction in methanol of 2‐(hydroxymethyl)‐6‐carbaldehyde‐4‐methylphenol, with 2‐aminophenol. Recently, we and others, have utilized the above‐mentioned aldehyde or corresponding multi‐compartmental Schiff base ligands to ensemble various 3d‐4f heterometallic complexes . The aldehyde [2‐(hydroxymethyl)‐6‐carbaldehyde‐4‐methylphenol] used here for Schiff base preparation is synthetically modified o ‐vanillin where terminal weakly coordinating methoxy (–OMe) group of o ‐vanillin has been substituted by alkoxy (–CH 2 OH) group.…”

“…From the knowledge base of Ni–Ln compounds, synthetic methods offer a variety of topology with different levels of control in the design. To the best of our knowledge, only six pentanuclear Ni–Ln heteronuclear complexes, (Figure ) are found whose detailed magnetic analysis has been done. Although the spirocyclic core is well known in pure 4f based compounds, the case of coordination compounds based on 3d‐4f systems, it is scare.…”

[5×1 + 1×1] Hexanuclear Lanthanide(III) Cocrystal Complexes: Syntheses, Structures, and Magnetic Properties

“…Two hexanuclear [5×1 + 1×1] lanthanide cocrystal complex [Ln 5 (L) 4 (LH 2 ) 2 (tfa) 4 ] · [Ln(tfa) 4 ] · 2CH 3 OH [Ln = Dy( 1 ) and Tb( 2 )] possessing an [2.2] spirocyclic topology were successfully derived from the ligand 2‐(hydroxymethyl)‐6‐carbaldehyde‐4‐methylphenol (LH 2 ). Although this ligand has been used previously,, but this is one of the rare example of a lanthanide cocrystal with one cationic pentanuclear [Ln 5 (L) 4 (LH 2 ) 2 (tfa) 4 ] + unit, one anionic mononuclear [Ln(tfa) 4 ] – unit along with two unit of methanol as solvent of crystallization being formed by it. The driving factor for cocrystal being supramolecular interaction, specifically hydrogen bonding is studied in detail.…”

“…Reagents and General Methods: Each of the chemicals and reagents acquired from commercial sources were used without any farther purification. The ligand 2‐(hydroxymethyl)‐6‐carbaldehyde‐4‐methylphenol (LH 2 ) has been synthesized using a formerly known procedure , . MnO 2 , 2,6‐Bis(hydroxymethyl)‐4‐methylphenol, DyCl 3 · 6H 2 O, TbCl 3 · 5H 2 O, 1,1,1‐Trifluoroacetylacetone (tfa) were purchased from Sigma Aldrich Co., India.…”