Ferrocenyl chalcones versus organic chalcones: a comparative study of their nematocidal activity.

A series of 30 organic chlacones and 33 ferrocenyl (Fc) chalcones were synthesized and characterized by melting point, elemental analysis, spectroscopy ((1)H NMR and FTIR) and, in two cases, by X-ray crystallography. The biological activity of each compound (10(-4)M in DMSO) against the model nematode Caenorhabditis elegans was examined in terms of % mortality (percent nematodes that died) and % fecundity (percent nematodes that reproduced) and compared to that obtained for the control medium (1% DMSO) over a 14-day period. Detailed conformational analyses for two Fc-chalcones (studied also by X-ray crystallography) were performed via molecular modeling studies. In general, the organic chalcones were found to be less polar than their Fc analogs. Some structure-activity relationships (SARs) were determined: (a) The nematocidal activities of the organic chalcones in this series were found to be much greater than those of their ferrocenyl analogs. (b) The position of the carbonyl group played a central role in the biological activity of both classes of chalcones studied. (c) For both classes of chalcones, lipophilicity of a compound seemed to play a significant role in its nematocidal activity. (d) The planarity of a ferrocenyl-chlacone seems to play a role in its activity.

Development of five-coordinate zinc mono- and dithiolates as S-donor metalloligands: formation of a Zn-W coordination polymer.

The synthesis and isolation of mono- and dithiolate-bridged Zn(mu-SR)(n)W(CO)(m) (where n = 1, m = 5; n = 2, m = 4) species from the dimeric N,N'-bis(2-mercaptoethyl)-1,4-diazacycloheptanezinc(II), [Zn-1'](2), and the monomeric [N-(3-thiabutyl)-N'-(3-thiapentaneoate)-1,5-diazacycloheptane]zinc(II), Zn-1'-Ac, are described. Upon cleavage of the dimeric [Zn-1'](2) with Na(+)[ICH(2)CO(2)](-), the resulting Zn-1'-Ac product is isolated as a monomeric, five-coordinate Zn(N(2)SS'O) complex equipped with one available Zn-bound thiolate for further reactivity. Cleavage of [Zn-1'](2) with [Et(4)N](+)Cl(-) afforded a monomeric intermediate, [Zn-1'-Cl](-), containing two Zn-bound thiolates. The zinc mono- and dithiolato complexes demonstrated reactivity toward labile-ligand tungsten carbonyl species, (THF)W(CO)(5) and (pip)(2)W(CO)(4), to yield respectively [(Zn-1'-Ac)W(CO)(5)](x) and [(Zn-1'-Cl)W(CO)(4)](-) complexes that were isolated and characterized spectroscopically and via X-ray diffraction. Upon binding to W(CO)(5), the five-coordinate Zn(N(2)SS'O) complex becomes six-coordinate within the coordination polymer [(Zn-1'-Ac)W(CO)(5)](x), in which the acetate tether of each molecule provides an O donor to occupy the octahedral axial position of a neighboring moiety. The [(Zn-1'-Cl)W(CO)(4)](-) dithiolate-bridged complex maintains a five-coordinate, square-pyramidal [Zn(N(2)S(2)Cl)](-) center, utilizing a chloride as the apical donor and resulting in an overall anionic complex. The addition of CO(g) to the [(Zn-1'-Cl)W(CO)(4)](-) complex was monitored by IR spectroscopy, which showed the emergence of [(Zn-1'-Cl)W(CO)(5)](-).

Capture of Ni(II), Cu(I) and Z(II) by thiolate sulfurs of an N2S2Ni complex: a role for a metallothiolate ligand in the acetyl-coenzyme A synthase active site.

The metal binding affinity of an (N2S2)Ni bridging metallothiolate ligand (Zn2+ < Ni2+ < Cu+) gives precedent for the observed heterogeneity in ACS/CODH.

N2S2Ni metallodithiolate complexes as ligands: structural and aqueous solution quantitative studies of the ability of metal ions to form M-S-Ni bridges to mercapto groups coordinated to nickel(II). implications for acetyl coenzyme A synthase.

The nickel(II) complex of an N2S2 ligand, derived from a diazacycle, N,N'-bis(mercaptoethyl)-1,5-diazacycloheptane, (bme-dach)Ni, Ni-1', serves as a metallodithiolate ligand to NiII, CuI, ZnII, Ag, and PbII. The binding ability of the NiN2S2 ligand to the metal ions was established through spectrochemical titrations in aqueous media and compared to classical S-donor ligands. For M = Ni, Zn, Pb, binding constants, log K = ca. 2. were computed for 1:1 Ni-1'/M(solvate) adducts; for Ag+ and Cu+, the 3:2 (Ni-1')3M2 adducts were the first formed products even in water with log beta3,2 values of 26 and >30, respectively. In all cases, the binding ability of Ni-S-R is intermediate between that of a free thiolate and a free thioether. The great specificity for copper over nickel and zinc by N2S2Ni, which serves as a reasonable structural model for the distal nickel of the acetyl CoA synthase active site, relates to biochemical studies of heterogeneity (metal content and type) in various preparations of acetyl CoA synthase enzyme.

Characterization of steric and electronic properties of NiN2S2 complexes as S-donor metallodithiolate ligands.

The physical properties and structures of a series of six complexes of the type (NiN(2)S(2))W(CO)(4) have been used to establish electronic and steric parameters for square planar NiN(2)S(2) complexes as bidentate, S-donor ligands. According to the nu(CO) stretching frequencies and associated computed Cotton-Kraihanzel force constants of the tungsten carbonyl adducts, there is little difference in donor abilities of the five neutral NiN(2)S(2) metallodithiolate ligands in the series. The dianionic Ni(ema)(2)(-) (ema = N,N'-ethylenebis(2-mercaptoacetamide)) complex transfers more electron density onto the W(CO)(4) moiety. A ranking of donor abilities and a comparison with classical bidentate ligands is as follows: Ni(ema)(=) > {[NiN(2)S(2)](0)} > bipy approximately phen > Ph(2)PCH(2)CH(2)PPh(2) > Ph(2)PCH(2)PPh(2). Electrochemical data from cyclic voltammetry find that the reduction event in the (NiN(2)S(2))W(CO)(4) derivatives is shifted to more positive potentials by ca. 0.5 V compared to the ca. -2 V Ni(II/I) redox event in the free NiN(2)S(2) ligand, consistent with the electron drain from the nickel-dithiolate ligands by the W(CO)(4) acceptor. Differences in Ni(II/I) DeltaE(1/2) values appear to have a ligand dependence which is related to a structural feature of the hinge angle imposed by the (mu-SR)(2) bridges. Thus the angle formed by the intersection of NiN(2)S(2)/WS(2)C(2) planes has been established by X-ray diffraction analyses as a unique orientational feature of the nickel-dithiolate ligands in contrast to classical diphosphine or diimine ligands and ranges in value from 136 to 107 degrees . Variable-temperature (13)C NMR studies show that the spatial orientations of the ligands remained fixed with respect to the W(CO)(4) moiety to temperatures of 100 degrees C.

Accommodation of the irregular coordination geometry of lead(II) by a square planar N2S2 ligand and its preference for zinc(II).

The N2S2 ligand, bis-mercaptoethanediazacyclooctane, coordinates to Pb(II) largely through sulfur donors, enlisting a second unit to fulfill an irregular, hemispherical N2S3 coordination environment in which a void suggests the location of a stereochemically active lone pair on Pb(II). That the highly exposed lead is vulnerable to metal ion displacement is demonstrated on reaction with zinc which results in a regular square pyramidal coordination about zinc within a [N2S2Zn]2 dimer. Analysis of the two dimeric structures finds different connectivities of the monomeric subunits account for the stability of the zinc structure over that of the lead.

Adamantane-like cluster complexes of mixed-valent copper-copper and nickel-copper thiolates.

Square-planar copper(II) and nickel(II) derivatives of the cis-dithiolate N(2)S(2) ligand bis(N,N'-2-mercapto-2-methylpropyl)-1,5-diazocyclooctane, (bme*daco)M, nucleate four Cu(I)Cl moieties, forming M(II)(2)Cu(I)(4)S(4) clusters with unusual triply bridging thiolates, mu(3)-SR, in the topological form of adamantane. As determined by X-ray crystallography, the (bme*daco)M (M = Cu or Ni) metallothiolate serves as a bidentate ligand that bridges four Cu(I) ions, utilizing all lone pairs on sulfurs. Further characterization by electrochemical and electronic spectral measurements suggests greater electron delocalization in the all-copper complex as compared to the NiCu heterometallic complex. Mass spectral data imply that the mixed-metal Ni(II)(2)Cu(I)(4)S(4) is more stable toward CuCl loss than Cu(II)(2)Cu(I)(4)S(4), a result that is corroborated by extraction of Cu(I) by 1,2-bis(diphenylphosphino)ethane in the latter but not the former.

Sensing of sulfur dioxide by base metal thiolates: structures and properties of molecular NiN2S2/SO2 adducts.

The cis-dithiolate N2S2Ni complex bismercaptoethanediazacycloheptanenickel(II), (bme-dach)Ni or Ni-1', takes up two equivalents of sulfur dioxide in which thiolate-sulfur to SO2-sulfur interactions are well-defined by X-ray crystallography. Ni-1' x 2SO2, C9H18N2NiO4S4, yields monoclinic crystals belonging to the P2(1)/c space group: a = 10.308(4) angstroms, b = 13.334(5) angstroms, c = 10.842(4) angstroms, alpha = 90 degrees, beta = 91.963(6) degrees, gamma = 90 degrees, and Z = 4. Further characterization by nu(SO) IR spectroscopy, thermal gravimetric analysis, electronic spectroscopy, and visual color changes upon reversible SO2 adduct formation establish Ni-1' and the analogous bismercaptoethanediazacyclooctane derivative, (bme-daco)Ni, Ni-1, to be viable candidates for technical development as chemical sensors of this noxious gas. Visual SO2 detection limits of Ni-1 and Ni-1' are established at 25 and 100 ppm, respectively. Both the Ni-1' x 2SO2 adduct and the Ni-1' reactant are air stable. In addition, the stability of Ni-1' x SO2 to vacuum and removal of SO2 by heating make Ni-1' a possible storage/controlled release complex for SO2 gas.