Polyoxometalates (POMs) are a subset of metal oxides that represent a diverse range of molecular clusters with an almost unmatched range of physical properties and the ability to form dynamic ...structures that can range in size from the nano- to the micrometer scale. Herein we present the very latest developments from synthesis to structure and function of POMs. We discuss the possibilities of creating highly sophisticated functional hierarchical systems with multiple, interdependent, functionalities along with a critical analysis that allows the non-specialist to learn the salient features. We propose and present a "periodic table of polyoxometalate building blocks". We also highlight some of the current issues and challenges that need to be addressed to work towards the design of functional systems based upon POM building blocks and look ahead to possible emerging application areas.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The discovery of new gigantic molecules formed by self‐assembly and crystal growth is challenging as it combines two contingent events; first is the formation of a new molecule, and second its ...crystallization. Herein, we construct a workflow that can be followed manually or by a robot to probe the envelope of both events and employ it for a new polyoxometalate cluster, Na6Mo120Ce6O366H12(H2O)78⋅200 H2O (1) which has a trigonal‐ring type architecture (yield 4.3 % based on Mo). Its synthesis and crystallization was probed using an active machine‐learning algorithm developed by us to explore the crystallization space, the algorithm results were compared with those obtained by human experimenters. The algorithm‐based search is able to cover ca. 9 times more crystallization space than a random search and ca. 6 times more than humans and increases the crystallization prediction accuracy to 82.4±0.7 % over 77.1±0.9 % from human experimenters.
Robo‐prof: The formation and crystallization of a new polyoxometalate cluster Na6Mo120Ce6O366H12(H2O)78⋅200 H2O (1) is performed using a robot with an active machine‐learning algorithm and the results compared to human experimenters in terms of efficiency and prediction accuracy. The robot is able to explore and discover new areas of interest not found by the humans.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
A design approach for the preparation of the {(DMAH)7H2SbW18O60} (DMAH-2) and {(DMAH)7H2BiW18O60} (DMAH-3) (DMAH = dimethylammonium) systems in a highly pure crystalline form is presented, and the ...latter is characterized by electrospray ionization mass spectrometry (ESI-MS) methods for the first time. These, together with the archetypal W10O32 cluster, are used as precursors for the formation of unique framework materials incorporating Ag(I) as a linking species. The systems are fully characterized by X-ray crystallography, elemental analysis, IR and thermogravimetric analysis (TGA), and the pyrolysis of the {Ag4-W10O32} system (1) leads to the formation of silver microparticles embedded in the resulting tungsten oxide and this has been observed by us previously with other systems. In contrast, the carefully controlled decomposition of the antimony and bismuth systems {Ag418O60} (Ag-2) and {Ag4-SbW18O60} (Ag-3) gives rise to the formation of highly pure, discrete silver microparticles as confirmed by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis. These unique materials may be interesting for applications such as catalysis, antimicrobial agents, or electroactive/photoactive coatings, and this work demonstrates how the molecular organization of the building blocks on the nanoscale can affect the assembly of materials over a range of length scales.
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IJS, KILJ, NUK, PNG, UL, UM
Polyoxometalates are clusters of metal-oxide units, comprising a large diversity of nanoscale structures, and have many common building blocks; in fact polyoxometalate clusters are perhaps the ...largest non-biologically derived molecules structurally characterised. Not only can polyoxometalates have gigantic nanoscale molecular structures, but they also a have a vast array of physical properties, many of which can be specifically 'engineered-in'. Here we describe how building block libraries of polyoxometalates can be used to construct systems with important catalytic, electronic, and structural properties. We also show that it is possible to construct complex chemical systems based upon polyoxometalates, manipulating the templating/self templating rules to exhibit emergent processes from the molecular to the macroscopic scale.
Polyoxometalates represent a diverse range of molecular clusters with an almost unmatched range of physical properties and the ability to form structures that can bridge several length scales. The ...new building block principles that have been discovered are beginning to allow the design of complex clusters with desired properties and structures and several structural types and novel physical properties are examined. In this critical review the synthetic and design approaches to the many polyoxometalate cluster types are presented encompassing all the sub-types of polyoxometalates including, isopolyoxometalates, heteropolyoxometalates, and reduced molybdenum blue systems. As well as the fundamental structure and bonding aspects, the final section is devoted to discussing these clusters in the context of contemporary and emerging interdisciplinary interests from areas as diverse as anti-viral agents, biological ion transport models, and materials science.
The discovery of chemical reactions is an inherently unpredictable and time-consuming process
. An attractive alternative is to predict reactivity, although relevant approaches, such as ...computer-aided reaction design, are still in their infancy
. Reaction prediction based on high-level quantum chemical methods is complex
, even for simple molecules. Although machine learning is powerful for data analysis
, its applications in chemistry are still being developed
. Inspired by strategies based on chemists' intuition
, we propose that a reaction system controlled by a machine learning algorithm may be able to explore the space of chemical reactions quickly, especially if trained by an expert
. Here we present an organic synthesis robot that can perform chemical reactions and analysis faster than they can be performed manually, as well as predict the reactivity of possible reagent combinations after conducting a small number of experiments, thus effectively navigating chemical reaction space. By using machine learning for decision making, enabled by binary encoding of the chemical inputs, the reactions can be assessed in real time using nuclear magnetic resonance and infrared spectroscopy. The machine learning system was able to predict the reactivity of about 1,000 reaction combinations with accuracy greater than 80 per cent after considering the outcomes of slightly over 10 per cent of the dataset. This approach was also used to calculate the reactivity of published datasets. Further, by using real-time data from our robot, these predictions were followed up manually by a chemist, leading to the discovery of four reactions.
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KISLJ, NUK, SBMB, UL, UM, UPUK
Polyoxometalates represent a diverse range of molecular clusters with an almost unmatched range of physical properties and the ability to form structures that can bridge several length scales. The ...new building block principles that have been discovered are beginning to allow the design of complex clusters with desired properties and structures; several structural types and novel physical properties are examined herein. The overall message that is presented throughout is the possibility that polyoxometalate clusters could be excellent candidates to be exploited in the development of functional nanosystems or nanodevices. The concepts that underpin the development of nanoscale devices are discussed briefly, as are the considerable challenges that must be overcome to realise polyoxometalate‐based functional nanosystems.
The diverse physical properties and complex structural hierarchy that underpins polyoxometalate chemistry is explored to develop the conceptual basis of routes to design polyoxometalate‐based functional nanosystems (see scheme) that could be utilised in molecular electronics and nanoscale devices.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Understanding the process of the self‐assembly of gigantic polyoxometalates and their subsequent molecular growth, by the addition of capping moieties onto the oxo‐frameworks, is critical for the ...development of the designed assembly of complex high‐nuclearity cluster species, yet such processes remain far from being understood. Herein we describe the molecular growth from {Mo150} and {Mo120Ce6} to afford two half‐closed gigantic molybdenum blue clusters {Mo180} (1) and {Mo130Ce6} (2), respectively. Compound 1 features a hat‐shaped structure with the parent wheel‐shaped {Mo150} being capped by a {Mo30} unit on one side. Similarly, 2 exhibits an elliptical lanthanide‐doped wheel {Mo120Ce6} that is sealed by a {Mo10} unit on one side. Moreover, the observation of the parent uncapped {Mo150} and {Mo120Ce6} clusters as minor products during the synthesis of 1 and 2 strongly suggests that the molecular growth process can be initialized from {Mo150} and {Mo120Ce6} in solution, respectively.
Big building blocks: Two half‐closed gigantic polyoxometalate (POM) clusters {Mo180} and {Mo130Ce6} have been constructed by molecular growth from {Mo150} and {Mo120Ce6}, respectively, demonstrating the concept of using gigantic clusters as “big building blocks” to build high‐nuclearity clusters.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The assembly of nanoscale polyoxometalate (POM) clusters has been dominated by the highly reduced icosahedral {Mo132} “browns” and the toroidal {Mo154} “blues” which are 45 % and 18 % reduced, ...respectively. We hypothesised that there is space for a greater diversity of structures in this immediate reduction zone. Here we show it is possible to make highly reduced mix‐valence POMs by presenting new classes of polyoxomolybdates: MoV52MoVI12H26O20042− {Mo64} and MoV40MoVI30H30O21520− {Mo70}, 81 % and 57 % reduced, respectively. The {Mo64} cluster archetype has a super‐cube structure and is composed of five different types of building blocks, each arranged in overlayed Archimedean or Platonic polyhedra. The {Mo70} cluster comprises five tripodal {MoV6} and five tetrahedral {MoV2MoVI2} building blocks alternatively linked to form a loop with a pentagonal star topology. We also show how the reaction yielding the {Mo64} super‐cube can be used in the enrichment of lanthanides which exploit the differences in selectivity in the self‐assembly of the polyoxometalates.
Novel types of highly reduced Mo polyoxometalates, the {Mo64} cube and {Mo70} star, are obtained through near‐hydrothermal conditions with incorporations of nickel and lanthanide ions and possess a set of building blocks different to those present in Mo blues and browns. With a few of other rare structures, this group of polyoxomolybdates is redefined as Mo reds based on the major differences in building blocks and reduction degrees.
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