Tetrahedral M4(µ4-O) Motifs Beyond Zn: Efficient One-Pot Synthesis of Oxido-Amidate Clusters via a Transmetalation/Hydrolysis Approach.

While zinc µ4-oxido-centered complexes are widely used as versatile precursors and building units of functional materials, the synthesis of their analogues based on other transition metals is highly underdeveloped. Herein, we present the first efficient systematic approach for the synthesis of homometallic [M4(µ4-O)L6]-type clusters incorporating divalent transition-metal centers, coated by bridging monoanionic organic ligands. As a proof of concept, we prepared a series of charge-neutral metal-oxido benzamidates, [M4(µ4-O) (NHCOPh)6] (M = Fe, Co, Zn), including iron(II) and cobalt(II) clusters not accessible before. The resulting complexes were characterized using elemental analysis, FTIR spectroscopy, magnetic measurements, and single-crystal X-ray diffraction. Detailed structural analysis showed interesting self-assembly of the tetrahedral clusters into 2D honeycomb-like supramolecular layers driven by hydrogen bonds in the proximal secondary coordination sphere. Moreover, we modeled the magnetic properties of new iron (II) and cobalt (II) clusters, which display a general tendency for antiferromagnetic coupling of the µ4-O/µ-benzamidate-bridged metal centers. The developed synthetic procedure is potentially easily extensible to other M(II)-oxido systems, which will likely pave the way to new oxido clusters with interesting optoelectronic and self-assembly properties and, as a result, will allow for the development of new functional materials not achievable before.

Applying Mechanochemistry for Bottom-Up Synthesis and Host-Guest Surface Modification of Semiconducting Nanocrystals: A Case of Water-Soluble ß-Cyclodextrin-Coated Zinc Oxide.

Mechanochemistry has recently emerged as an environmentally friendly solventless synthesis method enabling a variety of transformations including those impracticable in solution. However, its application in the synthesis of well-defined nanomaterials remains very limited. Here, we report a new bottom-up mechanochemical strategy to rapid mild-conditions synthesis of organic ligand-coated ZnO nanocrystals (NCs) and their further host-guest modification with ß-cyclodextrin (ß-CD) leading to water-soluble amide-ß-CD-coated ZnO NCs. The transformations can be achieved by either one-pot sequential or one-step three-component process. The developed bottom-up methodology is based on employing oxo-zinc benzamidate, [Zn4 (µ4 -O)(NHOCPh)6 ], as a predesigned molecular precursor undergoing mild solid-state transformation to ZnO NCs in the presence of water in a rapid, clean and sustainable process.

Supramolecular control over molecular magnetic materials: γ-cyclodextrin-templated grid of cobalt(II) single-ion magnets.

Single-ion magnets (SIMs) are potential building blocks of novel quantum computing devices. Unique magnetic properties of SIMs require effective separation of magnetic ions and can be tuned by even slight changes in their coordination sphere geometry. We show that an additional level of tailorability in the design of SIMs can be achieved by organizing magnetic ions into supramolecular architectures, resulting in gaining control over magnetic ion packing. Here, γ-cyclodextrin was used to template magnetic Co(II) and nonmagnetic auxiliary Li(+) ions to form a heterometallic {Co, Li, Li}4 ring. In the sandwich-type complex [(γ-CD)2Co4Li8(H2O)12] spatially separated Co(II) ions are prevented from superexchange magnetic coupling. Ac/dc magnetic and EPR studies demonstrated that individual Co(II) ions with positive zero-field splitting exhibit field-induced slow magnetic relaxation consistent with the SIMs' behavior, which is exceptional in complexes with easy-plane magnetic anisotropy.