A Reinvestigation of Salvarsan and Related Arsenic Chemistry.

In 1910 the first deliberately targeted search for a new chemotherapeutic agent came to fruition when Paul Ehrlich introduced Salvarsan for the treatment of syphilis. This thesis presents a detailed review of the history and literature leading up to and following on from Ehrlich’s discovery and thoroughly investigates the chemistry of Salvarsan and related species. A series of arylarsonic acids was prepared and fully characterised by electrospray mass spectrometry, NMR and X-ray crystallography for six examples. A detailed analysis of the hydrogen bonding in crystals of these molecules showed that they adopt several characteristic motifs which govern the packing in the crystals. Two of the examples containing NH2 groups crystallised as zwitterions while one NH2 containing example containing other bulky groups was is its molecular form. Salvarsan (cyclo 3-amino-4-hydroxyphenylarsenic(I)) was prepared by several different methods and analysed in detail using high resolution electrospray mass spectroscopy. This showed that Salvarsan consists of small cyclic species of the type (RAs)n where R is 3-NH2-4-OHC6H3 and n is three or greater. The dominant species in an aqueous solution of Salvarsan were found to be (RAs)3 and (RAs)5 . A detailed analysis is presented of impurities in Salvarsan prepared by different methods and also in a sample of original commercial Salvarsan. Mixtures of (RAs)n and (R’As)n exchange R groups in aqueous solution at room temperature, as shown by ESI-MS. ESI-MS studies are reported for the oxidation product of Salvarsan, RAs(OH)2 (commercially known as Mapharsen) and related As(III) compounds. Oligomers involving As-O-As linkages were found in solution and one tetrameric example (R = 3-NO2-4-OHC6H3) was isolated and structurally characterised. Preliminary ESI-MS studies showed that As(III) species bind to thioredoxin, a possible target for the pharmaceutical activity of Salvarsan and its derivatives

Chebfun and numerical quadrature

Chebfun is a Matlab-based software system that overloads Matlab’s discrete operations for vectors and matrices to analogous continuous operations for functions and operators. We begin by describing Chebfun’s fast capabilities for Clenshaw–Curtis and also Gauss–Legendre, –Jacobi, –Hermite, and –Laguerre quadrature, based on algorithms of Waldvogel and Glaser, Liu, and Rokhlin. Then we consider how such methods can be applied to quadrature problems including 2D integrals over rectangles, fractional derivatives and integrals, functions defined on unbounded intervals, and the fast computation of weights for barycentric interpolation

cyclo-Tetra-μ-oxido-tetrakis[3-nitro-4-hydroxyphenylarsenic(III)]

The title compound, [As₄O₄(C₆H₄NO₃)₄], has an eight-membered As₄O₄ ring with a slightly twisted boat-chair conformation. The aryl groups complete the threefold coordination for each As atom. Each OH group forms a strong intramolecular O-H⋯O hydrogen bond to the adjacent NO₂ group, with only weak C-H⋯O, O⋯As [3.036 (6)-3.184 (6) Å] and O⋯O [2.921 (10)-2.930 (10) Å] interactions between tetramers

Nicholas Lloyd’s Master Conducting Recital Program Notes

American Riversongs by Pierre La Plante Make Our Garden Grow by Leonard Bernstein, Arr. by Joseph Kreines Armed Forces Salute by Bob Lowden Be Thou My Vision by Travis Cross Creed by William Himes Two Movements from Lincolnshire Posy by Percy Grainger, Arr. by Michael Sweeney Incidental Suite by Claude T. Smith Symphony in Bb by Paul Hindemit

Six-coordinate organotin(IV) complexes formed using the Kläui ligands; [CpCo{P(OR′)2O}3]SnR3 − nCln

The complexes [CpCo{P(OR′)2O}3]SnR3 − nCln [R′ = Me, Et; R = Ph, Me] are readily prepared from the corresponding organotin chloride and the sodium salt of the Kläui ligands. The X-ray crystal structures of the full series are reported for R = Ph, n = 0-3, and these show that they are all six-coordinate, including the Ph3Sn derivative which is the first example of a SnC3O3 coordination sphere. 1H, 13C, 31P and 119Sn NMR spectra are reported, and interpreted in terms of significant second-order effects and fluxional processes

Substituted phenylarsonic acids; structures and spectroscopy

Full NMR and ESI-MS spectra, and differential scanning calorimeter data are presented for 15 substituted phenylarsonic acids, including two new fluoro-substituted examples. X-ray crystal structure determinations of five examples (phenylarsonic acid and the 4-fluoro-, 4-fluoro-3-nitro-, 3-amino-4-hydroxy- and 3-amino-4-methoxy-substituted derivatives) were determined and the H-bonding crystal-packing patterns analysed

A six-coordinate aryl-germanium complex formed by the Kläui ligand

PhGeCl₃ reacts with Na{[OP(OEt)₂]₃CoCp} to give the six-coordinate complex PhCl₂Ge{[OP(OEt)₂]₃CoCp}, characterised spectroscopically and by an X-ray crystal structure determination which showed a firmly-attached tridentate ligand [Ge–O 1.973(2) Å]

Novel six-coordinate Aryl- and Alkyltin complexes

Organo-tin compounds have wide applications as pesticides and as intermediates for organic synthesis.¹ They are invariably Sn(IV) derivatives and are generally four-coordinate.² The mixed organo/chioro compounds of the type RnSnCI4-n do however have the ability to expand their coordination numbers to five or six. This depends critically on the substituents - with four organic groups, R₄Sn, there is no tendency at all to coordinate extra ligands, while at the other extreme SnCl₄ readily forms six-coordinate [SnC1₄L₂] complexes since the electronegative halo groups increase the Lewis acidity of the tin centre