Expansion of Zirconium Oxide Clusters by 3d/4f Ions

Synthesis Strategies and Structures of Molecular Heterometallic Oxo Clusters

Multinuclear heterometallic oxo clusters, composed of two or more different metal cations bridged by oxo ligands, represent an important class of molecular complexes known for their unique magnetic, catalytic, and electrochemical properties resulting from cooperative interactions between the metal cations. If three or more types of metal cations can be arranged as designed, their chemical and physical properties can be precisely and flexibly controlled, potentially creating innovative materials. However, research on hetero-trimetallic and hetero-tetrametallic oxo clusters remains limited. This review presents an interdisciplinary search of multinuclear heterometallic oxo clusters, regardless of the type of ligand, to explain and classify their synthesis strategies and structures. By cataloging crystallographically characterized heterometallic oxo clusters using ligand-per-metal values and synthesis method notations, valuable insights have been gained into effective synthesis methods for the precise arrangement of metal cations. The advantages and disadvantages of one-pot synthesis methods and synthesis strategies for achieving precise structural control of heterometallic oxo clusters are discussed with an emphasis on the prediction of their final structures. The insights from this review are expected to drive the development of synthetic and analytical techniques for the precise synthesis of heterometallic complexes in a predictable way.

Transition metal and lanthanide modified MOF-808 for barcode design

This study explores the utilization of metal-organic frameworks (MOFs), particularly those incorporating lanthanide-based elements for their fluorescence capabilities, to create an advanced barcode system. By exploiting the modular nature of MOFs, we have developed a material capable of dynamic information encoding and robust against counterfeiting efforts. We introduce a novel barcode prototype that exhibits visible color shifts and fluorescence modulation when exposed to a specific sequence of chemical and thermal stimuli. The barcode is composed of MOF-808, which is modified with transition metals like iron or cobalt, and europium cations. These components are embedded within polyvinylidene fluoride (PVDF) to form a composite. This embedding process ensures that the MOF particles remain reactive to specific trigger molecules, enabling a distinct read-out sequence. The decoding process, involving exposure to ammonia, heating at 120 °C, and treatment with HCl, triggers observable changes in fluorescence and color, depending on the transition metal used. Our investigations with Eu,Co-MOF-808, and Eu,Fe-MOF-808 composites have resulted in the creation of a barcode prototype that demonstrates the feasibility of using europium-modified and unmodified transition metal modified MOF-808@PVDF composites for enhanced security applications.

Synthesis and structures of cobalt-expanded zirconium- and cerium-oxo clusters as precursors for mixed-metal oxide thin films

Transforming current complementary metal-oxide-semiconductor (CMOS) technology to fabricate memory chips and microprocessors into environmentally friendlier electronics requires the development of new approaches to resource- and energy-efficient electron transport and switching materials. Metal and multi-metal oxide layers play a key role in high-end technical applications. However, these layers are commonly produced through high-energy and high-temperature procedures. Herein, we demonstrate our first attempts to obtain stimuli-responsive mixed-metal oxide thin films from solution-processed molecular precursors under milder conditions. The molecular compounds of interest were prepared by one-pot reactions of a CoII carboxylate complex, triethylamine (Et3N), N-butyldiethanolamine (H2bda), and a hexanuclear complex [Ce6O4(OH)4(piv)12] (Hpiv = pivalic acid) or [Zr6O4(OH)4(ib)12(H2O)]·3Hib (Hib = isobutyric acid) in acetonitrile solution. The resulting charge-neutral, heterometallic coordination compounds display a ligand-supported pentanuclear {CeIV3CoIII2} core (in 1) and a dodecanuclear {ZrIV6CoII6} core (in 2), exhibiting thermal stability up to ca. 100 °C in air. Compound 2 was deposited and analyzed on Au(111) and SiO2/Si(100) surfaces to explore its potential as a single-molecule precursor for the preparation of atomically precise, complex mixed-metal oxide thin films. The adsorption characteristics of it demonstrate the ability to form stable agglomerates on the investigated surfaces.

Construction of zirconium/hafnium-oxo clusters based on a new protection-calix[8]arene

Calix[8]arene has been used as a promising type of macrocyclic ligand for the construction of multinuclear metal-oxo clusters (MOCs), but not for zirconium/hafnium-oxo clusters (Zr/HfOCs). In this paper, we report the first series of ZrOCs (HfOCs) based on calix[8]arene: Zr4, Zr8, Hf4, and Hf8. Zr8/Hf8 has a rhombohedral conformation and can be regarded as a derivative of the octahedral Zr6 cluster. Remarkably, I2 adsorption experiments indicate that Zr4 (Zr8) adsorbs much faster than Hf4 (Hf8). Density functional theory (DFT) calculations show that metallic Zr atoms interact more strongly with I2 than metallic Hf atoms. The successful application of calix[8]arene for the synthesis of well-defined ZrOCs (HfOCs) shows a bright future for MOCs protected by macrocyclic ligands.