Insertion reactions of beta-diketiminate-stabilised calcium amides with 1,3-dialkylcarbodiimides

A series of heteroleptic beta-diketiminate-stabilised calcium amides of the form [{ArNC(Me)CHC(Me)NAr}Ca{NR(1)R(2)}(THF)] (Ar = 2,6-diisopropylphenyl; R(1) = H, R(2) = Ar; R(1) = H, R(2) = CH(2)CH(2)OMe; R(1) = R(2) = Ph) react with 1,3-dialkylcarbodiimides, R(3)N[double bond, length as m-dash]C[double bond, length as m-dash]NR(3) (R(3) = Cy, (i)Pr), to yield the corresponding insertion products [{ArNC(Me)CHC(Me)NAr}Ca{(R(3)N)(2)CNR(1)R(2)}(THF)] at room temperature in hydrocarbon solutions. These latter compounds contain both beta-diketiminate and guanidinate ligands bound to calcium. Solid-state data are consistent with the guanidinate ligands adopting a number of binding modes including kappa(2) through kappa(3) coordination, with varying degrees of delocalisation of the non-bound guanidinate nitrogen lone-pair across the pi-framework of the ligand. DFT computational studies have been conducted to address these variations in coordination behaviour.     

Synthesis and Evaluation of Novel 1,2,6-Thiadiazinone Kinase Inhibitors as Potent Inhibitors of Solid Tumors

A focused series of substituted 4H-1,2,6-thiadiazin-4-ones was designed and synthesized to probe the anti-cancer properties of this scaffold. Insights from previous kinase inhibitor programs were used to carefully select several different substitution patterns. Compounds were tested on bladder, prostate, pancreatic, breast, chordoma, and lung cancer cell lines with an additional skin fibroblast cell line as a toxicity control. This resulted in the identification of several low single digit micro molar compounds with promising therapeutic windows, particularly for bladder and prostate cancer. A number of key structural features of the 4H-1,2,6-thiadiazin-4-one scaffold are discussed that show promising scope for future improvement.     

The Other Face of Bunsen's Cacodyl Disulfide,Me2As(S)‐S‐AsMe2: The Lewis‐Base Behaviour Towards Heavy Metal Cations

The reaction of Bunsen's cacodyl disulfide, Me₂As(S)‐S‐AsMe₂, with heavy metal cations in methanol produces insoluble salts (complexes) of dimethyldithioarsinic acid, Me₂AsS₂H, and dimethyl arsenium ion, Me₂As:⁺. This arsenium ion prefers to react with Me₂As(S)‐S‐AsMe₂, when in excess, compared to AcO^? or MeOH/H₂O and it is also reactive towards sulfur (S_x, x = 1‐8) producing the stabilized dimethylarsino sulfenium cation, . The complexes (Me₂AsS₂)_xM (x = 1 or 2) are unstable in the presence of their own heavy metal cations decomposing to colored solids. In an attempt to prepare salts of Me₂AsSH, the reactions of (Me₂AsS₂)_xM with triphenylphosphine and trimethyl phosphite gave the metal sulfide and Me₂As‐S‐AsMe₂ instead.     

An improved grid method for the computation of the pseudospectra of matrix polynomials

Pseudospectra of matrix polynomials have been systematically investigated in recent years, since they provide important insights into the sensitivity of polynomial eigenvalue problems. An accurate approximation of the pseudospectrum of a matrix polynomial $P\left(\lambda \right)$ by means of the standard grid method is highly demanding computationally. In this paper, we propose an improvement of the grid method, which reduces the computational cost and retains the robustness and the parallelism of the method. In particular, after giving two lower bounds for the distance from a point to the boundary of the pseudospectrum of $P\left(\lambda \right)$, we present two algorithms for the estimation of the pseudospectrum, using exclusion discs. Furthermore, two illustrative examples and an application of pseudospectra on elliptic (quadratic) eigenvalue problems are given.     

Ferromagnetic interactions in a 1D alternating linear chain of π-stacked 1,3-diphenyl-7-(thien-2-yl)-1,4-dihydro-1,2,4-benzotriazin-4-yl radicals

X-ray studies show that 1,3-diphenyl-7-(thien-2-yl)-1,4-dihydro-1,2,4-benzotriazin-4-yl (6) adopts a distorted, slipped π-stacked structure of centrosymmetric dimers with alternate short and long interplanar distances (3.48 and 3.52 ?). Cyclic voltammograms of 7-(thien-2-yl)benzotriazin-4-yl 6 show two fully reversible waves that correspond to the -1/0 and 0/+1 processes. EPR and DFT studies on radical 6 indicate that the spin density is mainly delocalized over the triazinyl fragment. Magnetic susceptibility measurements show that radical 6 obeys Curie-Weiss behavior in the 5-300 K region with C=0.378 emu K mol(-1) and θ=+4.72 K, which is consistent with ferromagnetic interactions between S=1/2 radicals. Fitting the magnetic susceptibility revealed the behavior is consistent with an alternating ferromagnetic chain (g=2.0071, J(1) =+7.12 cm(-1), J(2) =+1.28 cm(-1)).     

Studying pigments on painted plaster in Minoan,Roman and Early Byzantine Crete. A multi-analytical technique approach

Wall paintings spanning two millennia of Cretan painting history and technology were analysed in an effort to determine similarities and evolutions of painting materials and technology. A multi-technique approach was employed that combined the use of (a) laser-induced breakdown spectroscopy (LIBS) and Raman microspectroscopy, based on mobile instrumentation, appropriate for rapid, routine-level object characterization, and (b) non-destructive X-ray diffractometry (XRD), performed directly on the wall painting fragment, which provides detailed information on the minerals constituting the paint. Elemental analysis data obtained through LIBS were compared with molecular and crystal structure information from Raman spectroscopy and XRD. Cross-sections from selected samples were also investigated by means of optical microscopy and scanning electron microscopy coupled to micro-probe analysis and X-ray mapping that enabled identification of several mineral components of the paint confirming the results of the XRD analysis. In parallel, replica wall paintings, created with known pigments and binding media for reference purposes, were examined with optical microscopy and stain tested for organic materials. The overall study shows that the LIBS and Raman techniques offer key advantages, such as instrument mobility and speed of data collection and interpretation that are particularly important when dealing with on-site investigations. Thus, they are capable of providing important compositional information in an effective manner that enables quick surveying of wall paintings and permit targeted sample selection for further analysis by advanced laboratory techniques.     

Antiferromagnetic Interactions in 1D Heisenberg Linear Chains of 7‐(4‐Fluorophenyl) and 7‐Phenyl‐Substituted 1,3‐Diphenyl‐1,4‐dihydro‐ 1,2,4‐benzotriazin‐4‐yl Radicals

7‐(4‐Fluorophenyl) and 7‐phenyl‐substituted 1,3‐diphenyl‐1,4‐dihydro‐1,2,4‐benzotriazin‐4‐yl radicals were characterized by X‐ray diffraction analysis and variable‐temperature magnetic susceptibility studies. The radicals pack in 1D π stacks of equally spaced slipped radicals with interplanar distances of 3.59 and 3.67 Å and longitudinal angles of 40.97 and 43.47°, respectively. Magnetic‐susceptibility studies showed that both radicals exhibit antiferromagnetic interactions. Fitting the magnetic data revealed that the behavior is consistent with 1D regular linear antiferromagnetic chain with J=?12.9 cm^?1, zJ′=?0.4 cm^?1, g=2.0069 and J=?11.8 cm^?1, zJ′=?6.5 cm^?1, g=2.0071, respectively. Magnetic‐exchange interactions in benzotriazinyl radicals are sensitive to the degree of slippage, and inter‐radical separation and subtle changes in structure alter the fine balance between ferro‐ and antiferromagnetic interactions.     

An improved multi-staged algorithmic process for the solution of the examination timetabling problem

The efficient creation of examination timetables is a recurring and important problem for universities worldwide. Good timetables typically are characterized by balanced distances between consecutive exams for all students. In this contribution an approach for the examination timetabling problem as defined in the second International Timetabling Competition () is presented. The solution approach is managed on the top level by GRASP (Greedy Randomized Adaptive Search Procedure) and it involves several optimization algorithms, heuristics and metaheuristics. A construction phase is executed first producing a relatively high quality feasible solution and an improvement phase follows that further ameliorates the produced timetable. Each phase consists of stages that are consumed in a circular fashion. The procedure produces feasible solutions for each dataset provided under the runtime limit imposed by the rules of the ITC07 competition. Results are presented and analyzed.     

Dimethylphosphinato and dimethylarsinato complexes of Sb(III) and Bi(III) and their chemistry

Abstract  

The reaction of Me₂PO₂H and Me₂AsO₂H with SbCl₃, BiCl₃, and Bi(NO₃)₃·5H₂O gave the complexes Sb(Me₂PO₂)₃, Sb(Me₂AsO₂)₃, (Me₂PO₂)₂Bi-Cl, Bi(Me₂AsO₂)₃, (Me₂PO₂)₂Bi(NO₃), and (Me₂AsO₂)₂Bi(NO₃)·H₂O, respectively. The arsinato complexes did not react with the Lewis bases pyridine, Ph₃P, and Ph₃As in acetone. The compounds Sb(Me₂AsO₂)₃ and (Me₂AsO₂)₂Bi(NO₃)·H₂O reacted to a small extent with nicotinic acid in methanol but Bi(Me₂AsO₂)₃ gave (Me₂AsO₂-BiO) _x in good yields. (Me₂AsO₂)₂Bi(NO₃)·H₂O in methanol quantitatively rearranged to new complexes with the same composition, [(Me₂AsO₂)₂Bi(NO₃)·H₂O]′ and [(Me₂AsO₂)₂Bi(NO₃)·H₂O]″ in the presence of pyridine. With thiophenol in air, Sb(Me₂AsO₂)₃ gave PhSSPh and Me₂As-SPh (1:1 mol ratio), (Me₂AsO₂-SbO) _x and some Sb(Me₂AsO₂)₃ was reformed, Bi(Me₂AsO₂)₃ gave (Me₂AsO₂-BiO) _x , PhSSPh, and Me₂As-SPh (1:0.6 mol ratio), whereas (Me₂AsO₂)₂Bi(NO₃)·H₂O quantitatively gave PhSSPh, thus acting as a catalyst for the air oxidation of thiophenol.