Structural and Magnetic Study of a Trinuclear MnII-GdIII-MnIIComplex

Heterobimetallic 3d-4f complexes supported by a Schiff-base tripodal ligand

Complexes featuring multiple metal centres are of growing interest regarding metal-metal cooperation and its tuneability. Here the synthesis and characterisation of heterobimetallic complexes of a 3d metal (4: Mn, 5: Co) and lanthanum supported by a (1,1,1-tris[(3-methoxysalicylideneamino)methyl]ethane) ligand is reported, as well as discussion of their electronic structure via electron paramagnetic resonance (EPR) spectroscopy, electrochemical experiments and computational studies. Competitive binding experiments of the ligand and various metal salts unequivocally demonstrate that in these heterobimetallic complexes the 3d metal (Mn, Co) selectively occupies the κ6-N3O3 binding site of the ligand, whilst La occupies the κ6-O6 metal binding site in line with their relative oxophilicities. EPR spectroscopy supported by density functional theory analysis indicates that the 3d metal is high spin in both cases (S = 5/2 (Mn), 3/2 (Co)). Cyclic voltammetry studies on the Mn/La and Co/La bimetallic complexes revealed a quasi-reversible Mn2+/3+ redox process and poorly-defined irreversible oxidation events respectively.

Magneto-thermal properties and slow magnetic relaxation in Mn(II)Ln(III) complexes: influence of magnetic coupling on the magneto-caloric effect

A family of Mn(II)Ln(III) dinuclear and tetranuclear complexes (Ln = Gd and Dy) has been prepared from the compartmental ligands N,N'-dimethyl-N,N'-bis(2-hydroxy-3-formyl-5-bromobenzyl)ethylenediamine (H₂L¹) and N,N',N''-trimethyl-N,N''-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H₂L²). The Mn(II)Gd(III) complexes exhibit antiferromagnetic interactions between Mn(II) and Gd(III) ions in most cases, which are supported by Density Functional Theory (DFT) calculations. Experimental magneto-structural correlations carried out for the reported complexes and other related complexes found in bibliography show that the highest ferromagnetic coupling constants are observed in di-μ-phenoxido bridged complexes, which is due to the planarity of the Mn-(μ-O)₂-Gd bridging fragment and to the high Mn-O-Gd angles. The effect of these angles has been studied by DFT calculations performed on a di-μ-phenoxido doubly bridged model. The magneto-thermal properties of the Mn(II)Gd(III) based complexes have also been measured, concluding that the magnitude of the Magneto-Caloric Effect (MCE) is due to the strength rather than to the nature of the magnetic coupling. Moreover, when two Mn(II)Gd(III) dinuclear units are connected by two carbonato-bridging ligands the MCE is enhanced, obtaining a maximum magnetic entropy change of 36.4 Jkg^-1 K^-1 at ΔB = 7 T and T = 2.2 K. On the other hand, one of the dinuclear Mn(II)Dy(III) complexes displays Single-Molecule Magnet (SMM) behaviour with an energy barrier of 14.8 K under an applied external field of 1000 Oe.

Syntheses, structures, and magnetic properties of a series of Mn-M-Mn trinuclear complexes with different spin configurations

A series of trinuclear complexes, [MnII2Y^III(L)₂(HL)₂(NO₃)₃][Y^III(NO₃)₅]·7H₂O (1'), [MnII2Gd^III(HL)₄(NO₃)₄]₂[MnII2Gd^III(L)(HL)₃(NO₃)₄][Gd^III(NO₃)₅]₄·2(o-Xy)·12H₂O (2') and [MnII3(L)(HL)₂(NO₃)₄](NO₃)·1.25(p-Xy) (3'), were synthesized using a β-diketone ligand HL (HL = 1,3-bis(pyridin-2-yl)propane-1,3-dione). X-ray structural analyses revealed that each complex has a trinuclear core with an Mn(II)-M-Mn(II) arrangement (M = Y^III (1), Gd^III (2), and Mn^II (3)). In 1' with a diamagnetic Y(III) ion, negligible antiferromagnetic interactions between terminal Mn(II) ions are operative. On the other hand, 2' shows ferromagnetic interactions between Mn(II) and Gd(III) ions, affording a spin ground state of S_T = 17/2. The homometallic Mn(II)₃ complex of 3' has an S_T = 5/2 spin ground state resulting from the antiferromagnetic interactions between neighboring Mn(II) ions. The maximum magnetic entropy change (-ΔS_m) of 1'-3' was estimated to be 12.3, 24.8, and 8.0 J kg^-1 K^-1, respectively.

NiII–LnIII complexes with o-vanillin as the main ligand: syntheses, structures, magnetic and magnetocaloric properties

ortho-Vanillin yields three types of heteronuclear Ni^II–Ln^III complexes, ranging from dinuclear to tetranuclear defect dicubane complexes.

Methylene spacer regulated variation in conformation of tetradentate N2O2 donor Schiff bases trapped in manganese(iii) complexes

The paper attempts to explain the distortion from planarity of tetradentate Schiff bases in octahedral manganese(iii) complexes.

Nine self-assembled nickel(ii)–lanthanide(iii) heterometallic complexes constructed from a Salamo-type bisoxime and bearing a N- or O-donor auxiliary ligand: syntheses, structures and magnetic properties

Nine Ni(ii)–Ln(iii) complexes were prepared using 3-MeOsalamo and structurally characterized, and their magnetic properties were studied.

[LnIII–MnII–LnIII] heterometallic compounds: rare linear SMMs with divalent manganese ions

The perfectly linear metal array and the introduction of strong magnetic anisotropy Tb^IIIand Dy^IIIresult in new trinuclear heterometallic Ln^III–Mn^II–Ln^IIISMMs with high energy barriers.

Nanoscopic molecular magnets

This review highlights fundamental concepts and synthetic strategies of SMMs and selected examples of 3d, 4f, 5f and mixed 3d–4f, 4d–5d and 3d–5f based SMMs are discussed.

The first heterometallic examples of 3d-4f heptanuclear [Mn(II)3Ln(III)4] complexes with planar disc-like cores and diverse magnetic properties

A family of heptanuclear [Mn(II)(3)Ln(III)(4)] clusters with planar disc-like cores have been synthesized by a solvothermal route, where Ln = La, Pr, Nd, and Gd, and such fascinating topology is unprecedented in 3d-4f complexes. Dc magnetic susceptibility data show different magnetic behaviors derived from the difference in Ln ions.