Alkylenedithiophosphate derivatives of arsenic(III), antimony(III) and bismuth(III)

Tris(alkylenedithiophosphates) of arsenic(III), antimony(III) and bismuth(III),

have been synthesized by the reactions of alkylenedithiophosphoric acids with metal oxides and chlorides and of their ammonium salts with metal chlorides in suitable solvents. Mixed chloride alkylenedithiophosphates of arsenic(III) and antimony(III),

have been obtained by the reactions of metal chlorides with ammonium alkylenedithiophosphates at 1 : 1 and 1 : 2 molar ratios or alternatively by the co-disproportionations reactions of metal chlorides with metal tris(alkylenedithiophosphates) at different (2 : 1 and 1 : 2) molar ratios. These new compounds have been characterized by elemental analyses, molecular weight measurements and spectroscopic (IR, and ¹H and ³¹P NMR) data. Chelated structures with bidentate alkylenedithiophosphate groups have been proposed for all these derivatives.     

Unsymmetrical 1-naphthyltellurium(IV) dihalides: the interplay of Te···Br,C–H···Br and C–H···π interactions in the crystal structure of (1-naphthyl)(4-methylphenyl)tellurium(IV) dibromide

The crystal structure of (1-naphthyl)(4-methyl- phenyl)tellurium(IV) dibromide, the first unsymmetrical naphthyl containing diorganotellurium(IV) dibromide, shows the formation of one-dimensional supramolecular arrays where Te···Br secondary bonds link two parallel rows of molecules in a gear-teethed fashion. The weaker C–H···Br and C–H···π hydrogen bonds play important role in the formation of three-dimensional crystal lattice by cross linking these supramolecular motifs.     

Synthesis, characterization and interaction of a new chiral trinuclear complex [bis(aquodiaminotryptophanato) CuII–Sn2IV]chloride with calfthymus DNA

The new chiral trinuclear complex, [bis(aquodiaminotryptophanato)Cu^II–Sn₂^IV] chloride (1) was synthesized by employing a well-designed three-step pathway under anhydrous conditions. Interaction of the complex (1) with calf-thymus DNA was studied by spectrophotometry, cyclic voltammetry and viscosity measurements. The kinetic studies of calf-thymus DNA binding were carried out at 260 nm (λ_max of calf-thymus DNA) under pseudo-first order conditions. The rate constants, k_obs, were evaluated by the linear least squares regression method. The absorption spectra of the complex with calf-thymus DNA shows ‘hyperchromism’ which is attributed to the electrostatic interaction with calf-thymus DNA. The electrochemical behavior of complex (1) was studied in DMSO/H₂O (5:5) solution and showed a quasireversible Cu^II/Cu^I redox couple. The voltammetric studies of the complex in the absence and in the presence of DNA exhibit a shift in the formal potential E ⁰ and ratio of cathodic to anodic peak currents i_pa/i_pc indicating strong binding of the complex to calf-thymus DNA. The viscosity of DNA decreases with increasing concentration of the complex, suggesting that complex (1)binds to calf-thymus DNA by electrostatic association.     

Separation of charged colloids by a combination of pulsating lateral electric fields and poiseuille flow in a 2D channel

Separation of colloidal particles of different sizes is becoming increasingly important due to rapid developments in the area of proteomics, genetic engineering, drug discovery, etc. In particular, there is a need to accomplish these separations on a microscale in 'lab-on-a-chip' devices. In this paper, we propose a new method for accomplishing separation of charged colloids of different sizes in a microchannel. This method involves a combination of pulses of lateral electric fields and Poiseuille flow in the axial direction. We develop a model for this separation technique and obtain closed form solutions for the mean velocity and the dispersion coefficient for a pulse of molecules introduced into the channel. These expressions are then utilized to determine the channel length and the separation time. For reasonable value of design constants, the proposed technique can separate molecules of different sizes that have diffusivities of 10(-10) and 0.5 x 10(-10) m2/s in 15.7 s in a 3.7 mm long channel. The length and the time increase to 5.45 cm and 231 s if the ratio of the diffusivities is reduced from 2 to 1.2, i.e., the latter diffusivity is increased to 0.835 x 10(-10) m2/s, while keeping all the other parameters the same. If the diffusivities are about 10(-9) m(2)/s, the length and the time for separation are 1 cm and 17.5 s for D1/D2=2, and 16 cm and 269 s for D1/D2=1.2.     

Physico-chemical studies on samarium soaps in solid state

Summary The physico-chemical characteristics of samarium soaps (caproate and caprate) in solid state were investigated by IR, X-ray diffraction and TGA measurements. The IR results revealed that the fatty acids exist in dimeric state through hydrogen bonding and samarium soaps possess partial ionic character. The X-ray diffraction measurements were used to calculate the long spacings and the results confirmed the double layer structure of samarium soaps. The decomposition reaction was found kinetically of zero order and the values of energy of activation for the decomposition process for caproate and caprate were found to be 8.0 and 7.8 kcal mol^–1, respectively.

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Physikochemische Untersuchungen an Samariumseifen in festem Zustand

Zusammenfassung Die physikochemischen Charakteristika von Samariumseifen (Caproat und Caprat) wurden im festen Zustand mittels IR, Röntgendiffraktion und TGA-Messungen untersucht. Die IR-Ergebnisse zeigten, daß die Fettsäuren durch Wasserstoffbrücken dimer vorliegen und daß die Samariumseifen partiell ionischen Charakter besitzen. Die Röntgenuntersuchungen bestätigen die Doppelschichtstruktur der Seifen. Die Zersetzungsreaktion verlief nach nullter Ordnung, und die Aktivierungsenergien für den Zersetzungsprozeß für Caproat und Caprat waren 8.0 und 7.8 kcal mol^–1.

     

E.s.r., magnetic, optical and biological (SOD and antimicrobial) studies of imidazolate bridged Cu(II)-Zn(II) and Cu(II)-Ni(II) complexes with tris(2-amino ethyl)amine as capping ligand: a plausible model for superoxide dismutase

X-band e.s.r. and optical absorption spectra of the imidazolate bridged heterobimetallic complexes [(tren)Cu-E-Im-Zn-(tren)](ClO(4))(3) and [(tren)Cu-E-Im-Ni-(tren)](ClO(4))(3), where trentris(2-aminoethyl)amine, E-Im=2-ethylimidazolate ion and the related mononuclear complexes [Cu(tren)](ClO(4))(2) and [(tren)Cu-E-ImH)](ClO(4))(2) have been described. Biological activities (superoxide dismutase and antimicrobial) have also been measured and compared with reported complexes.     

Adducts of tellurium and organotellurium(IV) chlorides with transition metal chelates of tetradentate schiff bases

Summary Coordinative interaction between tellurium tetrachloride or aryltellurium trichloride and transition metal chelates of tetradentate Schiff bases has yielded bimetallic molecular adducts of the general formula R_nTeCl_4–n · ML [n = 0 or 1, R = Ph,p-MeOC₆H₄ orp-EtOC₆H₄, M = nickel(II) or copper(II) and L^2– dianion of the Schiff bases derived from salicylaldehyde oro-hydroxyacetophenone and ethylenediamine]. The i.r. spectral and magnetic measurements on the complexes in the solid state indicate coordination of the metal chelates to tellurium(IV)via two phenolic oxygens. Planarity about the transition metal ion is thus retained.     

Self-assembly of the 3-aminopropyltrimethoxysilane multilayers on Si and hysteretic current–voltage characteristics

We report the deposition of 3-aminopropyltrimethoxysilane (APTMS) multilayers on SiO_x/Si(p⁺⁺) substrates by a layer-by-layer self-assembly process. The multilayers were grafted in a glove box having nitrogen ambient with both humidity and oxygen contents <1 ppm using APTMS solutions prepared in an anhydrous toluene. Deposition of the multilayers has been carried out as a function of solution concentration and grafting time. Characterization of the multilayers using static de-ionized water contact angle, ellipsometry, X-rayphotoelectron spectroscopy and atomic force microscope measurements revealed that self-assembling of the multilayers takes place in two distinct stages: (i) the first APTMS monolayer chemisorbs on a hydroxylated oxide surface by a silanization process and, (ii) the surface amino group of the first monolayer chemisorbs the hydrolyzed silane group of other APTMS molecules present in the solution, leading to the formation of a bilayer. The second stage is a self-replicating process that results in the layer-by-layer self-assembly of the multilayers with trapped NH₃ ⁺ ions. The current–voltage characteristics of the multilayers exhibit a hysteresis effect along with a negative differential resistance, suggesting their potential application in the molecular memory devices. A possible mechanism for the observed hysteresis effect based on filling and de-filling of the NH₃ ⁺ acting as traps is presented. PACS 73.30.+y     

Synthetic,spectral, thermal and antimicrobial studies on some bis(N,N′‐dialkyldithiocarbamato) antimony(III) alkylenedithiophosphates

Bis(N, N′‐dialkyldithiocarbamato)antimony(III) alkylenedithiophosphates of the type [R₂NCS₂]₂ SbS(S)POGO [where NR₂ = N(CH₃)₂, N(C₂H₅)₂ and N(CH₂)₄; G = ? CH₂? C(C₂H₅)₂? CH₂? , ? CH₂? C(CH₃)₂? CH₂? , ? CH(CH₃)? CH(CH₃)? and ? C(CH₃)₂? C(CH₃)₂? ] were synthesized and characterized by physico‐chemical, spectral [UV, IR and NMR (¹H, ¹³C and ³¹P)] and thermal (TG, DTA and DSC) analysis. The TG decomposition analysis step of the complex indicated the formation of Sb₂S₃ as the final product. The first endothermic peak in DSC indicated the melting point of the complexes. These complexes were screened for their antimicrobial activities using the disk diffusion method. All the complexes showed good activity as antibacterial and antifungal agents on some selected bacterial and fungal strains, which increased on increasing the concentration. Chloroamphenicol and terbinafin were used as standards for comparison. Copyright © 2007 John Wiley & Sons, Ltd.