We hereby report a dinuclear Dy(III) complex, [Dy(LH3)Cl2]2·2Et2O (1) (LH4 = 2,3-dihydroxybenzylidene)-2-(hydroxyimino)propanehydrazide) where both the metal centres are in a pentagonal bipyramidal (PBP) geometry with the axial positions being occupied...

The synthesis, structure, and magnetic properties of three DyIII complexes of different nuclearity, [Dy2(H2L)2(NO3)] [NO3]·2H2O·CH3OH (1), [Dy4(HL)2(piv)4(OH)2] (2), and [Dy6(H2L)3(μ3–OH)­(μ3–CO3)3(CH3OH)4(H2O)8] 5Cl·3H2O (3) [(H4L) = 6-((bis­(2-hydroxyethyl)­amino)-N′-(2-hydroxybenzylidene)­picolinohydrazide)], are described. This variety of complexes with the same ligand could be obtained by playing with the metal-to-ligand molar ratio, the type of DyIII salt, the kind of base, and the presence/absence of coligand. 1 is a dinuclear complex, while 2 is a tetranuclear assembly with a butterfly-shaped topology. 3 is a homometallic hexanuclear complex that exhibits a propeller-shaped topology. Interestingly, in this complex 3, three atmospheric carbon dioxide molecules are trapped in the form of carbonate ions, which assist in holding the hexanuclear complex together. All of the complexes reveal a slow relaxation of magnetization even in zero applied field. Complex 1 is a zero-field SMM with an effective energy barrier (U eff) of magnetization reversal equal to 87(1) K and a relaxation time of τ0 = 6.4(3) × 10–9 s. Under an applied magnetic field of 0.1 T, these parameters change to U eff = 101(3) K, τ0 = 2.5(1) × 10–9 s. Complex 2 shows zero-field SMM behavior with U eff = 31(2) K, τ0 = 4.2(1) × 10–7 s or τ01 = 2(1) × 10–7 s, U eff1 = 37(8) K, τ02 = 5(6) × 10–5 s, and U eff2 = 8(4) by considering two Orbach relaxation processes, while 3, also a zero-field SMM, shows a double relaxation of magnetization [U eff1 = 62.4(3) K, τ01 = 4.6(3) × 10–8 s, and U eff1 = 2(1) K, τ02 = 4.6(2) × 10–5 s]. The ab initio calculations indicated that in these complexes, the Kramer’s ground doublet is characterized by an axial g-tensor with the prevalence of the m J = ±15/2 component, as well as that due to the weak magnetic coupling between the metal centers, the magnetic relaxation, which is dominated by the single DyIII centers rather than by the exchange-coupled states, takes place via Raman/Orbach or TA-QTM. Moreover, theoretical calculations support a toroidal magnetic state for complex 2.

Four new dinuclear complexes, [Co­(μ-L)­(μ-CCl3COO)­Y­(NO3)2]·2CHCl3·CH3CN·2H2O (1), [Co­(μ-L)­(μ-CH3COO)­Y­(NO3)2]·CH3CN (2), [Co­(μ-L)­(μ-PhCOO)­Y­(NO3)2]·3CH3CN·2H2O (3), and [Co­(μ-L)­(μ-tBuCOO)­Y­(NO3)2]·CHCl3·2H2O (4), having a CoIIYIII core, have been synthesized by employing a ferrocene based compartmental ligand which was synthesized by the reaction of diacetyl ferrocene with hydrazine hydrate followed by a condensation reaction with o-vanillin. A general synthetic protocol was employed to synthesize complexes 1–4, where the metallic core was kept the same with changing the bridging carboxylate groups. In all the complexes, the main structural motif is kept similar by only slightly varying the substitution on the bridging acetate groups. This variation has resulted in a small but subtle influence on the magnetic relaxation of all these four compounds. Ab initio CASSCF/NEVPT2 calculations were carried out to assess the effect of the different substitutions of the bridging ligands on the magnetic anisotropy parameters and on orbital arrangements. Ab initio calculations yield a very large positive D value, which is consistent with the geometry around the CoII ion and easy plane anisotropy (g xx , gyy > g zz ), with the order of the calculated D in the range of 72.4 to 91.7 cm–1 being estimated in this set of complexes. To ascertain the sign of zero-field splitting in these complexes, EPR spectra were recorded, which support the sign of D values estimated from ab initio calculations.

We predict a 2D ferromagnetic half-metal based on vanadium porphyrin (V–PP) using first-principles density functional theoretical analysis. We establish the dynamical stability of its planar structure and magnetic ground state through determination of energetics and phonon dispersion. We find that the exchange interaction between spins of nearest neighbor V atoms is mediated by delocalized states of porphyrin and determine its strength from the relative energies of states with ferromagnetic and antiferromagnetic ordering. Using it in an Ising model, our estimate of its Curie temperature (T c) is 197 K, which is higher than that of 2D manganese phthalocyanine (Mn–Pc) and 2D Cr–PP. With estimated work function of 4.9 eV, moderate in-plane stiffness, and a branch of very low energy flexural modes evident in its phonon dispersion, we find that 2D V–PP is quite suitable for use in flexible spintronic devices.

Three pentacoordinate CoII complexes were synthesized using a common tridentate ligand and varying the halide/pseudohalide ligand. The effect of the latter on the geometry and magnetic properties of the three complexes has been analysed.