Cyclodextrin-Templated Co(II) Grids: Symmetry Control over Supramolecular Topology and Magnetic Properties

Abstract

While inherent complexation properties and propensity for self-organization of cyclodextrins (CDs) render them potentially promising scaffolds of magnetic materials, this research area is still at an embryonic stage. We report on the synthesis and structure characterization of a new sandwich-type complex, [(α-CD) 2 Co 3 Li 6 (H 2 O) 9 ] ( α-1 ), which represents a smaller analogue of the previously characterized [(γ-CD) 2 Co 4 Li 8 (H 2 O) 12 ] ( γ-1 ) cluster. A comprehensive structural analysis of α-1 and a careful reinvestigation of γ-1 reveal how the symmetry of CD ligands determines the molecular composition and supramolecular arrangements of Co/Li sandwich-type complexes. Furthermore, the first comparative studies of the magnetic properties in this type of system point to subtle differences in the magnetic behavior of both compounds. The sandwich-type complexes α-1 and γ-1 exhibit field-induced slow magnetic relaxation, defining a new family of magnetic materials with a pillared grid-like supramolecular structure composed of weakly interacting Co II centers forming an SMM.

Synthesis, polymorphism, and shape complementarity-induced co-crystallization of hexanuclear Co(ii) clusters capped by a flexible heteroligand shell

“…40,41,[58][59][60] Furthermore, while the selective formation of co-crystals directed by specific noncovalent interactions between co-formers is widely recognized, similar phenomena based on specific shape and/or size complementarity of building units, are rarely explored. 61 Based on our longstanding experience in the design and development of synthetic approaches for main-group and transition metal multinuclear clusters [62][63][64][65][66][67][68][69] as well as the studies on the noncovalent interactions-driven self-assembly of metal complexes, 63,64,68,[70][71][72][73][74] Remarkably, the proper purification of a starting Co(II) acetate reagent played a pivotal role in the selective formation of clusters 1 or 2. Comprehensive structural analysis of new compounds demonstrated intriguing crystal structure diversity of hydroxido-acetato cluster 1, which represents a rare example of both conformational and packing polymorphism in one compound.…”

“…Based on our longstanding experience in the design and development of synthetic approaches for main-group and transition metal multinuclear clusters 62–69 as well as the studies on the noncovalent interactions-driven self-assembly of metal complexes, 63,64,68,70–74 herein, we present the synthesis and comprehensive structural characterization of two new heteroleptic hydroxido-acetato and acetato Co( ii ) clusters [Co 6 (OH) 2 (OAc) 4 ( pyret ) 6 ] ( 1 ) and [Co 6 (OAc) 6 ( pyret ) 6 ] ( 2 ) incorporating an auxiliary 2-pyrrolidinoethoxylate ( pyret ) ligand. Remarkably, the proper purification of a starting Co( ii ) acetate reagent played a pivotal role in the selective formation of clusters 1 or 2 .…”