Octanuclear Ni4 Ln4 Coordination Aggregates from Schiff Base Anion Supports and Connecting of Two Ni2 Ln2 Cubes: Syntheses, Structures, and Magnetic Properties.

Abstract

A family of 3d-4f aggregates have been reported through guiding the dual coordination modes of ligand anion (HL- ) and in situ generated ancillary bridge driven self-assembly coordination responses toward two different types of metal ions. Reactions of lanthanide(III) nitrate (Ln=Gd, Tb, Dy, Ho and Yb), nickel(II) acetate and phenol-based ditopic ligand anion of 2-[{(2-hydroxypropyl)imino}methyl]-6-methoxyphenol (H2 L) in MeCN-MeOH (3 : 1) mixture and LiOH provided five new octanuclear Ni-4f coordination aggregates from two Ni2 Ln2 cubanes. Single-crystal X-ray diffraction analysis reveals that all the members of the family are isostructural, with the central core formed from the coupling of two distorted [Ni2 Ln2 O4 ] heterometallic cubanes [Ni2 Ln2 (HL)2 (μ3 -OH)2 (OH)(OAc)4 ]+ (Ln=Gd (1), Tb (2), Dy (3), Ho (4) and Yb (5)). Higher coordination demand of 4f ions induced the coupling of the two cubes by (OH)(OAc)2 bridges. Variable temperature magnetic study reveals weak coupling between the Ni2+ and Ln3+ ions. For the Tb (2) and Dy (3) analogs, the compounds are SMMs without an applied dc field, whereas the Gd (1) analogue is not an SMM. The observation revealed thus that the anisotropy of the Ln3+ ions is central to display the SMM behavior within this structurally intriguing family of compounds.