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Many of the well established media used for C. elegans studies are unsuitable for work involving silver ions and silver nanoparticles. The use of silver with such media may lead to precipitation of silver salts, or aggregation of silver nanoparticles, due to high chloride and/or phosphate concentrations, and high ionic strength. The use of solid (agar) media is complicated by the antimicrobial effects of silver, which make the growth of the E. coli nutrient source impossible at high exposure concentrations. We have developed a new liquid medium of low ionic strength with no chloride and very low phosphate concentrations. The medium contains major ions at environmentally realistic concentrations, and fulvic acid may be added to simulate natural organic matter. The concentration of the ions and fulvic acid can be adjusted to explore the influence of medium composition on toxicity.The medium has been successfully used in trials with silver nitrate and silver nanoparticles. Control responses of C. elegans compared favourably with those seen in the standard M9 medium. The levels of variation among replicates in these trials was low, allowing subtle differences such as potential hormesis effects to be detected and analysed with a high degree of statistical rigour.

The syntheses of the arylphosphonic esters 3-Br-5-tBu-1-{P(O)(OiPr) 2}C 6H 3 (1), 5-tBu-1,3-{P(O)(OiPr) 2} 2C 6H 3 (2), of the heteroleptic intramolecularly coordinated organostannylenes [4-tBu-2,6-{P(O)(OiPr) 2} 2C 6H 2]SnX (3, X = Cl; 4, X = Br; 5, X = I; 6, X = SPh), the organoplumbylene [4-tBu-2,6-{P(O)(OiPr) 2} 2C 6H 2]PbCl (7), and the transition metal complex [4-tBu-2,6-{P(O)(OiPr) 2} 2C 6H 2]Sn(Cl)Cr(CO) 5 (8) are reported. The compounds were characterized by 1H, 13C, 31P, 31P MAS (3), 119Sn, and 119Sn MAS (3) NMR spectroscopy, electrospray ionization mass spectrometry (3), Mössbauer spectroscopy (3-5, 8) and single-crystal X-ray diffraction analyses (2, 3-5, 6-8). In contrast to its ethoxy-substituted analogue [4-tBu-2,6-{P(O)(OEt) 2} 2C 6H 2]SnCl, compound 3, like the thiophenolate derivative 6, is monomeric in solution as well as in the solid state. This difference is also manifested by the Mössbauer as well as solid state NMR spectroscopic data. On the other hand, the corresponding organoplumbylene 7 shows a similar chlorido-bridged polymeric structure as its ethoxy-substituted analogue. Variable-temperature and concentration-dependent 1H and 31P NMR spectra reveal, on the respective time scales, the tin atom in compound 3 to be configurationally unstable and those in compounds 6 and 8 to be configurationally stable. DFT calculations support a chlorido-bridged dimer to account for the configurational instability in compound 3. Surprisingly and in contrast to compounds 3 and 6, the organobromido- and organoiodidostannylenes 4 and 5, respectively, show intermolecular Sn⋯Sn distances of 3.6809(4) and 3.5953(4) Å being shorter than twice the van der Waals radius of tin (2.20 Å). Quantum chemical calculations were performed on monomeric and dimeric model compounds, which revealed a weak Sn⋯Sn bonding interaction for dimer 3 (16 kJ·mol -1) as well as for dimer 5 (20 kJ·mol -1) whereas the hypothetical model compound p-tBuC 6H 4SnI showed an iodido-bridged dime

The heteroleptic organotin(II) halides {2,6-[P(O)(OEt)(2)](2)-4-tert-Bu-C6H2}SnX (1, X = Cl; 2, X = Br) have been prepared starting from {2,6-[P(O)(OEt)(2)](2)-4-tert-Bu-C6H2}Li and SnX2 and have been used as precursors for the preparation of the heteroleptic stannylenes {2,6[P(O)(OEt)(2)](2)-4-tert-Bu-C6H2}SnX (4, X = SPh; 5, X = CH(SiMe3)(2); 6, X = SiPh3; 7, X = SnPh3; 7a, X = SnMe3), the tetravalent monorganotin derivatives {{2,6-[P(O)(OEt)(2)](2)-4-tert-Bu-C6H2}SnCl(mu -S)}(2) (8) and {2,6-[P(O)(OEt)(2)](2)-4-tert-Bu-C6H2}SnBr3 (9), the diorganotin cation {2,6-[P(O)(OEt)(2)](2)-4-tert-Bu-C6H2}(Ph3C)(Cl)Sn+PF6- (10), and the metal-stannylene complexes {2,6-[P(O)(OEt)(2)](2)-4-tert-Bu-C6H2}(Cl)Sn[M(CO)(n)] (11, M = W, n = 5; 12, M = Cr, n = 5; 13, M = Fe, n = 4). Multinuclear (H-1, C-13, P-31, Sn-119) NMR of all compounds, Sn-119 Mossbauer spectra of 1 and 10, and single-crystal X-ray structure analyses of 6, 8, and 12 are reported. The derivatives 6, 7, and 7a are rare examples of compounds containing Sn(II)-Si(IV) and Sn(II)-Sn(IV) bonds, respectively.

FLWIN, info:eu-repo/semantics/published

The synthesis or in situ. formation of the new stannasiloxanes (RRSi)-R-1-Si-2(OSn-t-Bu-2)(2)E (2, R-1 = R-2 = t-Bu, E = O; 22, R-1 = t-Bu, R-2 = F, E = O; 23, R-1 = R-2 = Ph, E = O; 24, R-1 = R-2 = t-Bu, E = S; 25, R-1 = t-Bu, R-2 = F, E S; 26, R-1 = R-2 = Ph, E S), t-Bu2Si[OSn(Cl)-t-Bu-2]2 (3), t-Bu-2(Cl)SnOSi(X)-t-Bu-2 (4,X = Cl; 12, X = H), t-Bu2Sn((OSiRRO)-R-1-O-2)(2)M (5, R-1 = R-2 = t-Bu, M = Sn-t-Bu-2; 7, R-1 = R-2 = Ph, M = Sn-t-Bu-2; 9, R-1 = R-2 = Ph, M = SiPh2; 1.8, R-1 = t-Bu, R-2 = Cl, M = Sn-t-Bu-2; 21, R-1 = t-Bu, R-2 = F, M = Sn-t-Bu-2), t-Bu2Sn(OSiXR2)(2) (10, X = H, R = t-Bu; 11, X = F, R = t-Bu; 13, X = F, R = Et; 14, X = F,R = i-Pr; 15, X = F, R = Ph), t-Bu2Sn(OSiX2-t-Bu)(2) (16, X = Cl; 19, X = Fl, t-Bu2ClSnOSiCl2-t-Bu (17), [R1R2Si(OSn-t-Bu-2)(2)O.t-Bu2SnX2] (20, R-1 = t-Bu, R-2 = F; X = F; 27, R-1 = t-Bu, R-2 = F, X = OR; 28, R-1 = R-2 = Ph, X = OH), O(t-Bu2SnOSiPh2)(2)O (29), t-Bu2Sn(OSiMe2CH2)(2) (30), and t-Bu-2-SnOSiF-t-BuOSn-t-Bu(2)OSit-Bu2O (31) is described. The compounds were characterized by means of multinuclear NMR spectroscopy and Mossbauer spectroscopy. The molecular structures of the eight-membered stannasiloxane rings 5, 7,, 21, and 29 were determined by X-ray analysis, On the basis of NMR and electrospray mass spectrometry a mechanism is proposed involving protonated Species for the redistribution reaction between 5 and 21.

The complex [Ph2Si(OSnt-Bu-2)(2)Ot-Bu2Sn(OH)(2)] (2) was obtained in high yield by reaction of Ph2Si(OH)(2) with (t-Bu2SnO)(3) (1). Reaction of t-Bu2Si(OH)(2) with 1 gave [t-Bu2Si(OSnt-Bu-2)(2)O] (4a) instead. The compounds were investigated by means of NMR, IR, Mossbauer spectroscopy, and in case of 2 by X-ray analysis. In solution, 2 is in equilibrium with [Ph2Si(OSnt-Bu-2)(2)O] (2a), 1, and water. t-Bu2Sn(OH)(2) (3) was prepared by controlled hydrolysis of t-Bu2Sn(OMe)(2) and was shown to undergo condensation with formation of 1. Mossbauer studies as well as Sn-119 CP MAS NMR including side band analysis suggest 3 to exhibit a dimeric structure with pentacoordinate tin. Similar studies on 1 suggest fast rotation of the molecule in the crystal lattice.

The crystal structure of the reaction product of the 2:3 condensation of salicylaldoxime with di-n-butyltin(IV) oxide, [(Bu2Sn)(Bu2SnO)(Bu2SnOH)(HONZO)(ONZO)], where HONZOH represents HON=CHC6H4OH (salicylaldoxime), was determined by single-crystal X-ray diffraction; it belongs to the monoclinic system, space group P2(1)/c, with a = 20.995(3) angstrom, b = 17.394(4) angstrom, c = 12.254(2) angstrom, beta = 94.43(2)degrees, and Z = 4. The compound contains two five-coordinate trigonal-bipyramidal tin atoms with the two butyl groups in equatorial positions; the third tin atom has a seven-coordinate pentagonal-bipyramidal geometry with the two butyl groups in apical positions. The bonds of the salicylaldoxime ligands to the metal atoms are inequivalent. Both ligands are bound to the seven-coordinate tin atom through the oxygen atom originating from the phenolic function and through the nitrogen atom of the aldoxime function. In the ligand that binds as HONZO, the phenolate oxygen atom further coordinates a five-coordinate tin atom. In the ligand that coordinates as ONZO, the NO oxygen is bonded to the other five-coordinate atom. The H-1, C-13, and Sn-119 NMR data are in agreement with such a structure existing as a major species M in solution. However, the NMR spectra also reveal the presence of three other minor species in solution, m1, m2, and m3. These species could not be isolated as pure compounds, as crystallization from any solution of this compound led systematically to crystals of M. The H-1 and Sn-119 spectra, the (n)j(Sn-119-Sn-119/Sn-117) coupling satellite patterns observed in Sn-119 spectra, and the two-dimensional proton detected H-1-Sn-119 heteronuclear multiple bond correlation (2D H-1-Sn-119 HMBC) maps allow us to propose a structure for each species.

SCOPUS: ar.j, info:eu-repo/semantics/published