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One phenoxo–hydroxo bridged tetranuclear cluster and one phenoxo-µ1,1-azido-µ1,3-azido bridged one-dimensional coordination polymer of copper(ii) derived from a Schiff base ligand are described.

The present report deals with the syntheses, crystal structures, dc/ac magnetic properties and DFT/ab initio CASSCF calculations of two isomorphous bis(η1:η2:μ2-acetate)GdIII2/DyIII2 compounds of the formula [LnIII2L2(acetate)4(MeOH)2] (1, Ln = Gd; 2, Ln = Dy), where HL is (E)-N'-(3-ethoxysalicylidene)acetohydrazide. The two lanthanide(iii) centres in each compound are symmetry-related owing to the presence of an inversion centre. Both compounds exhibit intramolecular ferromagnetic exchange interactions. The DyIII2 analogue is a single-molecule magnet (SMM) with Ueff = 52.8 cm-1 and τ0 = 1.52 × 10-6 s. DFT calculations for 1 and ab initio calculations for 2 also reveal ferromagnetic interactions. Ab initio calculations of the SMM behaviour of 2 and two other reported and structurally related compounds reveal the importance of the weak exchange interaction present between the two DyIII ions, and a relaxation mechanism has been developed to take into account the magnetic exchange interaction and to rationalize the observed difference in the Ueff values.

The work in this report describes the syntheses, electrospray ionization mass spectromtery, structures, and experimental and density functional theoretical (DFT) magnetic properties of four tetrametallic stars of composition [M(II)(Cu(II)L)3](ClO4)2 (1, M = Mn; 2, M = Ni; 3, M = Cu; 4, M = Zn) derived from a single-compartment Schiff base ligand, N,N'-bis(salicylidene)-1,4-butanediamine (H2L), which is the [2 + 1] condensation product of salicylaldehyde and 1,4-diaminobutane. The central metal ion (Mn(II), Ni(II), Cu(II), or Zn(II)) is linked with two μ2-phenoxo bridges of each of the three [Cu(II)L] moieties, and thus the central metal ion is encapsulated in between three [Cu(II)L] units. The title compounds are rare or sole examples of stars having these metal-ion combinations. In the cases of 1, 3, and 4, the four metal ions form a centered isosceles triangle, while the four metal ions in 2 form a centered equilateral triangle. Both the variable-temperature magnetic susceptibility and variable-field magnetization (at 2-10 K) of 1-3 have been measured and simulated contemporaneously. While the Mn(II)Cu(II)3 compound 1 exhibits ferromagnetic interaction with J = 1.02 cm(-1), the Ni(II)Cu(II)3 compound 2 and Cu(II)Cu(II)3 compound 3 exhibit antiferromagnetic interaction with J = -3.53 and -35.5 cm(-1), respectively. Variable-temperature magnetic susceptibility data of the Zn(II)Cu(II)3 compound 4 indicate very weak antiferromagnetic interaction of -1.4 cm(-1), as expected. On the basis of known correlations, the magnetic properties of 1-3 are unusual; it seems that ferromagnetic interaction in 1 and weak/moderate antiferromagnetic interaction in 2 and 3 are possibly related to the distorted coordination environment of the peripheral copper(II) centers (intermediate between square-planar and tetrahedral). DFT calculations have been done to elucidate the magnetic properties. The DFT-computed J values are quantitatively (for 1) or qualitatively (for 2 and 3) matched well with the experimental values. Spin densities and magnetic orbitals (natural bond orbitals) correspond well with the trend of observed/computed magnetic exchange interactions.