Nonanuclear Heterometal Five-Layer Sandwich-Type Polyoxometalate

Abstract

A new nonanuclear heterometal five-layer sandwich silicotungstate [H 2 N(CH 3 ) 2 ] 6 H 5 NaK{[NaMn 8 O 6 (OAc) 6 ][A-α-SiW 9 O 34 ] 2 }•34H 2 O (1) has been made under hydrothermal reactions of MnCl 2 •4H 2 O, KMnO 4 , trivacant [A-α-SiW 9 O 34 ] 10− {SiW 9 } fragment, and [H 2 N(CH 3 ) 2 ]• Cl in NaOAc-HOAc buffer (pH = 4.8). The polyoxoanion of 1 is a sandwich architecture, in which the nonanuclear heterometal cluster [Na-Mn 8 O 6 (OAc) 6 ] 7+ made of two triangular pyramid clusters [Mn 4 O 3 (OAc) 3 ] 3+{Mn 4 } via a hexacoordinate antitrigonal prism Na + linkage is encapsulated by two trivacant fragments of {SiW 9 }. Furthermore, magnetic measurements of compound 1 reveal the existence of antiferromagnetic exchange interactions between the metal centers.

A μ-AsO4-Bridging Hexadecanuclear Ni-Substituted Polyoxotungstate

“…Polyoxometalates (POMs), a unique and attractive class of nanoscale metal-oxo clusters, are constituted by the condensation of the edge-, corner-, and face-sharing MO 6 polyhedral building units of early transition metals (e.g., W, Mo, V, and Nb). − The characteristic negative charges endow them the merits of acting as multidentate O-donor inorganic ligands. Especially for lacunary POM fragments, the high reactivity of the exposed surface oxygen atoms facilitates the integration with versatile metal cations, thereby generating the functionalized metal-substituted POMs with huge potential applications. − …”

{Ti6}/{Ti10} Wheel Cluster Substituted Silicotungstate Aggregates

“…Polyoxometalates (POMs), as types of classic metal–oxygen clusters, have a history of nearly 200 years and present diversiform architectures of different sizes and shapes. − The design and synthesis of novel POM materials have always been very valuable works due to their extensive potential applications in various fields such as photophysics, electrochemistry, magnetism, catalysis, medicine, and so on. − In the enormous family of POMs, the synthetic chemistry of transition-metal-substituted POMs (TMSPs) has experienced rapid development and generally has become the leading subject of POM science. − So far, a feasible strategy for making new TMSPs is using lacunary POM fragments as the structure-directing agents (SDAs) to induce the TM cations into the lacunary sites of POMs. − During the process of assembly, under the influence of experimental conditions such as pH and temperature, the lacunary fragments undergo a configuration transformation to form one or more types of building units that can cooperate each other to induce TM cation aggregation, resulting in the emergence of novel TMSP species with structural diversity and unique physicochemical properties. − …”

A {Ti6W4}-Cluster-Substituted Polyoxotungstate: Synthesis, Structure, and Catalytic Oxidation Properties

“…1 to 6 nm and metal centers spanning from 6 to 368, possess extensive applications in various domains, such as catalysis, medicine, photophysics, magnetism, and so forth. − In particular, the selective oxidation catalysis by POMs has aroused widespread concern because of their abundant catalytic active sites and relative stability under thermal and oxidation conditions compared with organometallic catalysts. In recent years, with the further in-depth exploitation and utilization of POMs, the design and synthesis of novel POMs with polynuclear functional metals (transition metals and lanthanides) have been strongly promoted and rapidly developed. − …”