Discrete unusual mixed-bridged trinuclear Co^III₂Co^IIand pentanuclear Ni^IIcoordination complexes supported by a phenolate-based ligand: theoretical and experimental magneto-structural study

Two new complexes [Co^III₂Co^II(μ-OL)₂(μ-OOCCH₃)₂(μ-N₃)₂(N₃)₂]·Et₂O (1·Et₂O) and [Ni^II₅(μ-OL)₄(μ-OOCCH₃)₂(OOCCH₃)₂(μ-N₃)₂]·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 that1is a discrete trinuclear and2is a discrete pentanuclear coordination complex. In complex1, terminal metal (Co^III) is in a distorted octahedral MN₄O₂environment 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 MN₂O₄environment 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 complex2, each Ni is in a distorted octahedral MN₂O₄/MN₃O₃environment 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 of1·Et₂O and2were carried out in the temperature range of 1.8-300 K. The magnetic behaviour of1·Et₂O indicates the presence of magnetic anisotropy of the cobalt(ii) ion. The magnetic data of2reveal the coexistence of antiferromagnetic and ferromagnetic interactions within the Ni₅unit. Theoretical calculations made from the crystal structures reveal a very good agreement with the experimental findings.