Neutral organoantimony(III) and organobismuth(III) ligands as acceptors in transition metal complexes – role of substituents and co-ligands

This article reviews work up until mid-2014 on the synthesis and properties of transition metal complexes containing the heavier Group 15 Sb(III) and Bi(III) ligands, of general formula ER3 (E = Sb or Bi; R = alkyl, aryl etc, and may include a pendant donor group such as amine or ether) and ER(3-n)Xn (E = Sb or Bi; R is an organic substituent such as alkyl, aryl, etc.; X is an electronegative substituent such as halide; n = 0-3) in which these ligands function as a donor to a transition metal fragment, while simultaneously participating as an acceptor to another electronegative group such as an anionic or metal-coordinated halide, or an amine, ether, etc., leading to Sb/Bi centres bearing more than eight valence electrons ('hypervalent'). The Lewis acid properties of the halostibines and halobismuthines, ER(3-n)Xn, are also reviewed

Diverse structure and reactivity of pentamethylcyclopentadienyl antimony(iii) cations

The pentamethylcyclopentadienyl (Cp*) antimony(III) cations [Cp*2Sb][B(C6F5)4], [Cp2*Sb][OTf], [Cp*SbCl][B(C6F5)4] and [Cp*Sb][OTf]2 have been isolated and structurally characterised. [Cp*SbCl]+ forms dimers in the solid state via an intermolecular Sb–Cl interaction. Initial screening shows that [Cp*SbCl][B(C6F5)4] is significantly Lewis acidic and can catalyse the dimerisation of 1,1-diphenylethylene; [Cp2*Sb][B(C6F5)4] exhibits negligible Lewis acidity. Highly unstable [Cp*SbF][B(C6F5)4] could not be isolated, but stabilisation with the IMes ligand allowed isolation of [Cp*SbF(IMes)][B(C6F5)4]. Fluorodechlorination of CH2Cl2 and PhCCl3 was observed in the presence of crude [Cp*SbF][B(C6F5)4] in solution. A computational mechanistic investigation suggests that the latter proceeds via a carbocation intermediate

Nanoscale arrays of antimony telluride single crystals by selective chemical vapor deposition

Arrays of individual single nanocrystals of Sb2Te3 have been formed using selective chemical vapor deposition (CVD) from a single source precursor. Crystals are self-assembled reproducibly in confined spaces of 100 nm diameter with pitch down to 500 nm. The distribution of crystallite sizes across the arrays is very narrow (standard deviation of 15%) and is affected by both the hole diameter and the array pitch. The preferred growth of the crystals in the orientation along the diagonal of the square holes strongly indicates that the diffusion of adatoms results in a near thermodynamic equilibrium growth mechanism of the nuclei. A clear relationship between electrical resistivity and selectivity is established across a range of metal selenides and tellurides, showing that conductive materials result in more selective growth and suggesting that electron donation is of critical importance for selective deposition

Phenotypic and functional characterization of corneal endothelial cells during in vitro expansion.

The advent of cell culture-based methods for the establishment and expansion of human corneal endothelial cells (CEnC) has provided a source of transplantable corneal endothelium, with a significant potential to challenge the one donor-one recipient paradigm. However, concerns over cell identity remain, and a comprehensive characterization of the cultured CEnC across serial passages has not been performed. To this end, we compared two established CEnC culture methods by assessing the transcriptomic changes that occur during in vitro expansion. In confluent monolayers, low mitogenic culture conditions preserved corneal endothelial cell state identity better than culture in high mitogenic conditions. Expansion by continuous passaging induced replicative cell senescence. Transcriptomic analysis of the senescent phenotype identified a cell senescence signature distinct for CEnC. We identified activation of both classic and new cell signaling pathways that may be targeted to prevent senescence, a significant barrier to realizing the potential clinical utility of in vitro expansion

Mononuclear dysprosium(III) complexes with triphenylphosphine oxide ligands: controlling the coordination environment and magnetic anisotropy

We report the synthesis, structural and magnetic characterization of five mononuclear DyIII ion complexes using triphenylphosphine oxide as a monodentate ligand. They have formulae [DyIII(OPPh3)3(NO3)3] (1), [DyIII(OPPh3)4(NO3)2](NO3) (2), [DyIII(OPPh3)3Cl3] (3), [DyIII(OPPh3)4Cl2]Cl (4) and [DyIII(OPPh3)4Cl2](FeCl4) (5). These complexes are characterized using single crystal X-ray diffraction, which revealed that each complex has a unique coordination environment around the DyIII ion, which results in varying dynamic magnetic behavior. Ab initio calculations are performed to rationalize the observed magnetic behavior and to understand the effect that the ligand and coordination geometry around the DyIII ion has on the single-molecule magnet (SMM) behavior. In recent years, seven coordinate DyIII complexes possessing pseudo ~D5h symmetry are found to yield attractive blocking temperatures for the development of new SMM complexes. However, here we show that the strength of the donor ligand plays a critical role in determining the effective energy barrier and is not simply dependent on the geometry and the symmetry around the DyIII ion. Seven coordinate molecules possessing pseudo D5h symmetry with strong equatorial ligation and weak axial ligation are found to be inferior, exhibiting no SMM characteristics under zero-field conditions. Thus, this comprehensive study offers insight on improving the blocking temperature of mononuclear SMMs

A five-membered PdSbn coordination series

Five complexes of the general formula PdCl2(SbMe2Cl)n (n = 1-5) have been synthesised by combining [PdCl2(MeCN)2] and SbMe2Cl in different molar ratios in toluene. Their solid-state structures have been determined by X-ray crystallography. The complexes display considerable structural diversity: [Pd4Cl8(SbMe2Cl)4] (1, n = 1) is a chloride bridged tetramer, [Pd2Cl4(SbMe2Cl)4] (2, n = 2) is a dimer, [PdCl(SbMe2Cl)2(SbMe2Cl2)] (3, n = 3) is a supramolecular polymer, [Pd2(SbMe2Cl)8]Cl4¬ (4, n = 4) is a loosely associated dimer and [Pd(SbMe2Cl)5]Cl2 (5, n = 5) is a monomer with square pyramidal PdSb5 coordination geometry. Each structure contains secondary interactions between coordinated Sb centres and chloride ligands or anions, resulting in five-coordinate Sb in all cases with a range of Sb∙∙∙Cl bond lengths. The electronic structures of these complexes have been investigated using DFT methods including NBO and Pipek-Mezey localised orbital methods in order to interrogate both the Sb-Pd and secondary Sb∙∙∙Cl bonding

Crystal structure and Hirshfeld surface analysis of diethyl (6-methyl-2-pyridyl)aminoethylenemalonate

The title compound, diethyl (6-methyl-2-pyridyl)aminoethylenemalonate (1), crystallises in in the monoclinic space group P21/c (No.14). The unit cell parameters are a= 10.5657(7) Å, b= 9.1784(5) Å, c= 14.5681(7) Å, β= 101.636(6)°, Z’=1 and Z=4 at 150 K. The extended structure forms approximately orthogonal columns of stacked molecules. All bond lengths and angles are unremarkable. No disorder, twinning or co-crystallised solvent is present in the structure. An intramolecular hydrogen bond exists between the enamine nitrogen and carbonyl oxygen. Hirshfeld surface analysis reveals a short contact between a carbonyl oxygen and neighbouring aryl hydrogen, as well as a carbonyl-carbonyl interaction

Can we continue research in splenectomized dogs? Mycoplasma haemocanis: Old problem - New insight

We report the appearance of a Mycoplasma haemocanis infection in laboratory dogs, which has been reported previously, yet, never before in Europe. Outbreak of the disease was triggered by a splenectomy intended to prepare the dogs for a hemorrhagic shock study. The clinical course of the dogs was dramatic including anorexia and hemolytic anemia. Treatment included allogeneic transfusion, prednisone, and oxytetracycline. Systematic follow-up (n=12, blood smears, antibody testing and specific polymerase chain reaction) gives clear evidence that persistent eradication of M. haemocanis is unlikely. We, therefore, had to abandon the intended shock study. In the absence of effective surveillance and screening for M. haemocanis, the question arises whether it is prudent to continue shock research in splenectomized dogs. Copyright (C) 2004 S. Karger AG, Basel

CDK-dependent nuclear localization of B-Cyclin Clb1 promotes FEAR activation during meiosis I in budding yeast

Cyclin-dependent kinases (CDK) are master regulators of the cell cycle in eukaryotes. CDK activity is regulated by the presence, post-translational modification and spatial localization of its regulatory subunit cyclin. In budding yeast, the B-cyclin Clb1 is phosphorylated and localizes to the nucleus during meiosis I. However the functional significance of Clb1's phosphorylation and nuclear localization and their mutual dependency is unknown. In this paper, we demonstrate that meiosis-specific phosphorylation of Clb1 requires its import to the nucleus but not vice versa. While Clb1 phosphorylation is dependent on activity of both CDK and polo-like kinase Cdc5, its nuclear localization requires CDK but not Cdc5 activity. Furthermore we show that increased nuclear localization of Clb1 during meiosis enhances activation of FEAR (Cdc Fourteen Early Anaphase Release) pathway. We discuss the significance of our results in relation to regulation of exit from meiosis I