Benjamin T. R. Littlefield

Bio: Benjamin T. R. Littlefield is an academic researcher from University of Southampton. The author has contributed to research in topics: Trigonal bipyramidal molecular geometry & Bridging (networking). The author has an hindex of 5, co-authored 6 publications receiving 62 citations. Previous affiliations of Benjamin T. R. Littlefield include University of Reading.

Synthesis, chemistry and structures of complexes of the dioxovanadium(V) halides VO2F and VO2Cl

Abstract: [VO2F(L–L)] (L–L = 2,2′-bipyridyl, 1,10-phenanthroline, Me2N(CH2)2NMe2) and [VO2F(py)2] (py = pyridine) have been prepared from the corresponding [VOF3(L–L)] or [VOF3(py)2] and O(SiMe3)2 in MeCN solution. VO2F (itself made from VOF3 and O(SiMe3)2 in MeCN) forms [Me4N][VO2F2] with [Me4N]F, but does not react with neutral N- or O-donor ligands. VO2Cl, prepared from VOCl3 and ozone, reacts with 2,2′-bipyridyl or 1,10-phenanthroline to form [VO2Cl(L–L)], with pyridine or pyridine-N-oxide (L) to produce [VO2Cl(L)2], and with OPPh3 or OAsPh3 (L′) gives [VO2Cl(L′)]. A second product from the OPPh3 system is the ionic [VO2(OPPh3)3][VO2Cl2] containing a trigonal bipyramidal cation. Neither VO2F nor VO2Cl form isolable complexes with MeCN, thf or MeO(CH2)2OMe, and both are reduced by P-, As-, S- or Se-donor ligands. [Ph4As][VO2X2] (X = F or Cl) react with 2,2′-bipyridyl to form [VO2X(2,2′-bipyridyl)], but similar reactions with weaker O-donor ligands fail. The complexes have been characterised by IR, multinuclear NMR (1H, 19F, 51V or 31P) and UV-visible spectroscopy. X-ray crystal structures are reported for [VO2F(py)2], [VO2Cl(L)2] (L = py or pyNO) and [VO2(OPPh3)3][VO2Cl2].

Lightweight nanoporous metal hydroxide-rich zeotypes

Abstract: Nanoporous materials have important industrial applications as molecular sieves, catalysts and in gas separation and storage. They are normally produced as moderately dense silicates (SiO(2)) and aluminosilicates making their specific capacities for the uptake and storage of gases, such as hydrogen, relatively low. Here we report the synthesis and characterization of lightweight, nanoporous structures formed from the metal hydroxide Be(OH)(2) in combination with relatively low levels of framework phosphate or arsenate. Three new zeotype structures are described, constructed mainly of Be(OH)(4) tetrahedra bridged through hydroxide into three-membered rings; these units link together to produce several previously unknown zeotype cage types and some of the most structurally complex, nanoporous materials ever discovered. These materials have very low densities between 1.12 and 1.37 g cm(-3) and theoretical porosities of 63-68% of their total volume thereby yielding very high total specific pore volumes of up to 0.60 cm(3) g(-1).

An operationally simple sonogashira reaction for an undergraduate organic chemistry laboratory class

Abstract: An operationally simple, reliable, and cheap Sonogashira reaction suitable for an undergraduate laboratory class that can be completed within a day-long (8 h) laboratory session has been developed. Cross-coupling is carried out between 2-methyl-3-butyn-2-ol and various aryl iodides using catalytic amounts of bis(triphenylphosphine)palladium(II) dichloride, with copper(I) iodide as a cocatalyst, in triethylamine at room temperature, so a range of products can be prepared within a single group and results compared. The coupling itself is usually complete within 1.5 h and is easily monitored by TLC, leaving up to 6 h for purification and characterization. Purification is by “mini flash column chromatography” through a plug of silica encased in the barrel of a plastic syringe, so the procedure is amenable to large class sizes.

Structure of the Be(OH)42− anion

Abstract: Sr[Be(OH)4] has been synthesised and its structure determination contains the first definitive characterisation of the discrete Be(OH)42− anion.

Introduction to zeolite science and practice

Abstract: "Introduction to Zeolite Molecular Sieves, 3rd Edition" presents a collection of the most important results and ideas in the field of molecular sieve chemistry and technology, the most important experimental techniques related to the research activities in molecular sieves, and identifies new areas of molecular sieve chemistry Chapters start at a reasonably simple entry level, but also covers the present state-of-the-art in the field Topics covered include structure, synthesis, characterization, ion exchange, adsorption, diffusion, separations, and natural zeolites 6 years since the last edtion, this book brings together the rapid development within the field of molecular sieve chemistry and applications It is accessible to newcomers to the field, also containing valuable information for experienced researchers It contains 27 chapters written by renowned scientists in their field, including updates on some 2nd edition chapters

Immune Modulation by Human Secreted RNases at the Extracellular Space

Abstract: The ribonuclease A superfamily is a vertebrate-specific family of proteins that encompasses eight functional members in humans. The proteins are secreted by diverse innate immune cells, from blood cells to epithelial cells and their levels in our body fluids correlate with infection and inflammation processes. Recent studies ascribe a prominent role to secretory RNases in the extracellular space. Extracellular RNases endowed with immuno-modulatory and antimicrobial properties can participate in a wide variety of host defense tasks, from performing cellular housekeeping to maintaining body fluid sterility. Their expression and secretion are induced in response to a variety of injury stimuli. The secreted proteins can target damaged cells and facilitate their removal from the focus of infection or inflammation. Following tissue damage, RNases can participate in clearing RNA from cellular debris or work as signaling molecules to regulate the host response and contribute to tissue remodeling and repair. We provide here an overall perspective on the current knowledge of human RNases' biological properties and their role in health and disease. The review also includes a brief description of other vertebrate family members and unrelated extracellular RNases that share common mechanisms of action. A better knowledge of RNase mechanism of actions and an understanding of their physiological roles should facilitate the development of novel therapeutics.

Trigonal Bipyramidal or Square Pyramidal Coordination Geometry? Investigating the Most Potent Geometry for Vanadium Phosphatase Inhibitors

Abstract: The five-coordinate geometry is an important factor in phosphoryl group transfer, particularly for phosphate ester hydrolysis. In the following review we analyze the five-coordinate geometries for a range of VO4X coordination spheres with regard to their structure from the point of view of square pyramidal or trigonal bipyramidal geometries. The actual differences for the coordination environment of the reported small molecule structures are compared to the coordination environment of vanadate complexed to a protein tyrosine phosphatase (PTP) with four coordinating O atoms and one S atom. These considerations demonstrate that actual differences between the coordination environments are very small and presumably less critical than generally anticipated. This analysis suggests that it is a combination of structural and electronic properties leading to the perfect combination of reactivity and stability for the potent protein phosphatase inhibitor complex, thus confirming the fact that some other geometries have been reported.