Discrete unusual mixed-bridged trinuclear CoIII2CoII and pentanuclear NiII coordination complexes supported by a phenolate-based ligand: theoretical and experimental magneto-structural study

Two new complexes [(Co2CoII)-Co-III(mu-OL)(2)(mu-OOCCH3)(2)(mu-N-3)(2)(N-3)(2)]center dot Et2O (1 center dot Et2O) and [Ni-5(II)(mu-OL)(4)(mu-OOCCH3)(2)(OOCCH3)(2)(mu-N-3)(2)]center dot CH3CN (2) (HOL = 2-((2-(pyridin-2-yl)ethylamino)methyl)phenol) have been synthesized and characterized by elemental analysis, IR, and UV/Vis spectroscopy. Structural analysis revealed that 1 is a discrete trinuclear and 2 is a discrete pentanuclear coordination complex. In complex 1, terminal metal (Co-III) is in a distorted octahedral MN4O2 environment where coordination is satisfied by two nitrogen atoms and one oxygen atom of the ligand, and an oxygen atom from the acetate group and two nitrogen atoms from azide (one each from the bridging and terminal ones). The central metal (Co-II) is also in a distorted octahedral MN2O4 environment where coordination is satisfied by two oxygen atoms from the phenoxo bridge, two oxygen atoms from the acetate bridge and two nitrogen atoms from the azide bridge. In complex 2, each Ni is in a distorted octahedral MN2O4/MN3O3 environment where coordination is satisfied by different donor atoms (amine, pyridine, acetate, phenolate and azide). Direct current (DC) variable-temperature magnetic susceptibility measurements on polycrystalline samples of 1 center dot Et2O and 2 were carried out in the temperature range of 1.8-300 K. The magnetic behaviour of 1 center dot Et2O indicates the presence of magnetic anisotropy of the cobalt(ii) ion. The magnetic data of 2 reveal the coexistence of antiferromagnetic and ferromagnetic interactions within the Ni-5 unit. Theoretical calculations made from the crystal structures reveal a very good agreement with the experimental findings.

Automated summary

Two new metal complexes, a trinuclear and a pentanuclear coordination structure, have been synthesized and characterized. The structural analysis reveals different coordination environments for the metals in each complex. Magnetic susceptibility measurements show the presence of magnetic anisotropy for the cobalt ion in one complex and a coexistence of antiferromagnetic and ferromagnetic interactions within the nickel pentanuclear unit in the other complex. Theoretical calculations based on crystal structures are in good agreement with experimental findings.