Asymmetric {Dy4} metallogrid and double-layered {Dy8} cage clusters from carboxylic decorated o-vanillin Schiff bases: syntheses, topological variation, and single molecule magnet behaviors?

New Journal of Chemistry Pub Date: 2022-12-22 DOI: 10.1039/D2NJ04701B

Abstract

There is still great potential to be tapped for polynuclear lanthanide single-molecule magnets (Ln-SMMs) for performance. Toward this goal, the exploration of polynuclear lanthanide clusters (PLnCs) with novel special topologies is critical. Herein, two novel PLnCs, [Dy4(ov6ca)6(CH3OH) (H2O)2]·6CH3OH·CH3CN·H2O (1) and [Dy8(ov5ca)6(a5ca)4(ov)2(μ-OH)6]·6CH3OH (2), have been synthesized, where ov6ca2?, ov5ca2?, a5ca?, ov? represent the ions of 2-[(o-vanillidene)amino]-6-chlorobenzoic acid, 2-[(o-vanillidene)amino]-5-chlorobenzoic acid, 2-amino-5-chlorobenzoic acid and o-vanillin, respectively. Carboxylic decorated o-vanillin Schiff base ligands H2ov6ca and H2ov5ca, were constructed as 1 and 2, respectively, and only differ in the position of a Cl-substituent. However, this tiny difference has induced great variation in the nuclearity and topology between 1 and 2. Cluster 1 features a {Dy4} metallogrid core, where four DyIII ions are bridged by two Ophenol and two carboxylate groups from ov6ca2? ligands but show different coordination geometries. To our knowledge, it is the first {Ln4} cluster with such an asymmetric metallogrid topology. While 2 displays a rare double-layered cage cluster topology, in which a pair of butterfly-shaped {Dy4} units were linked together by four carboxylate groups from ov5ca2? ligands. Magnetic measurements revealed that both 1 and 2 exhibit slow magnetic relaxation behavior, with efficient energy barrier (Ueff) values of 93.06 and 66.92 K, respectively.

Graphical abstract: Asymmetric {Dy4} metallogrid and double-layered {Dy8} cage clusters from carboxylic decorated o-vanillin Schiff bases: syntheses, topological variation, and single molecule magnet behaviors
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