Windmill-shaped octanuclear Zn II4/Ln III4 (LnIII = Dy, Tb, Ho) heterometallic ensembles supported by a tetraferrocene scaffold

Abstract

Utilizing a new ferrocene-based compartmental ligand, H₄L (1), a series of novel heterometallic complexes [{LZn(μ-OAc)Dy}₄(μ₄-H₂O)] (2), [{LZn(μ-OAc)Tb}₄(μ₄-H₂O)] (3), [{LZn(μ-OAc)Ho}₄(μ₄-H₂O)] (4), [L = Fe[(C₅H₄){–C(Me)N–NC₆H₃-(o-O)(m-O)}]₂] were synthesized and characterized. 2 and 3 crystallize in the monoclinic crystal system in the I2/m space group, whereas 4 crystallizes in the tetragonal crystal system in the I4/m space group. The tetra deprotonated ligand L⁴⁻ has two distinct coordination compartments: one pocket (2N, 2O) suitable for the transition metal (3d) ions and another pocket (4O) suitable for lanthanide (4f) metal ions. Additionally, the terminal phenoxo group can be utilized for cluster expansion. In all the complexes, the Zn^II ion is in a perfect square pyramidal (2N, 3O) geometry whereas the lanthanide ion has a coordination number of eight (8O) in a distorted biaugmented trigonal-prism geometry. The electrochemical properties of 2 and 3 along with ligand H₄L (1) were studied by cyclic voltammetry (CV). All the complexes display a similar type of electrochemical behavior viz., one quasi-reversible oxidation typical of a ferrocene/ferrocenium motif. The magnetic properties of all the complexes have also been investigated.