Yee Seng Tan

Molecular mechanisms of apoptosis and cell selectivity of zinc dithiocarbamates functionalized with hydroxyethyl substituents.

In the solid state each of three binuclear zinc dithiocarbamates bearing hydroxyethyl groups, {Zn[S2CN(R)CH2CH2OH]2}2 for R = iPr (1), CH2CH2OH (2), and Me (3), and an all alkyl species, [Zn(S2CNEt2)2]2 (4), features a centrosymmetric {ZnSCS}2 core with a step topology; both 1 and 3 were isolated as monohydrates. All compounds were broadly cytotoxic, specifically against human cancer cell lines compared with normal cells, with greater potency than cisplatin. Notably, some selectivity were indicated with 2 being the most potent against human ovarian carcinoma cells (cisA2780), and 4 being more cytotoxic toward multidrug resistant human breast carcinoma cells (MCF-7R), human colon adenocarcinoma cells (HT-29), and human lung adenocarcinoma epithelial cells (A549). Based on human apoptosis PCR-array analysis, caspase activities, DNA fragmentation, cell apoptotic assays, intracellular reactive oxygen species (ROS) measurements and human topoisomerase I inhibition, induction of apoptosis in HT-29 cells is demonstrated via both extrinsic and intrinsic pathways. Compounds 2-4 activate the p53 gene while 1 activates both p53 and p73. Cell cycle arrest at the S and G2/M phases correlates with inhibition of HT-29 cell growth. Cell invasion is also inhibited by 1-4 which is correlated with down-regulation of NF-κB.

Persistence of C–H⋯π(chelate ring) interactions in the crystal structures of Pd(S2COR)2. The utility of Pd(S2COR)2 as precursors for palladium sulphide materials

The crystallographic structures of 12 palladium xanthates, Pd(S2COR)2 (R = alkyl) show a uniform adoption of square-planar PdS4 geometries. Supramolecular aggregation in 1 (R = Me), 2 (Et) and 3 (n-Pr) is based on secondary Pd⋯S interactions, which are “turned off” when the bulk of R increases. In 4 (i-Pr), C–H⋯S hydrogen bonding is present. In each of 2–4, C–H⋯π(PdS2C) interactions are incorporated within the architecture, stabilised by Pd⋯S secondary- or C–H⋯S hydrogen-bonding. In 5–12 (R = n-Bu, i-Bu, n-Pent, i-Pent, neoPent, n-Hex, i-Hex, neoHex), varying numbers of stand-alone C–H⋯π(PdS2C) interactions involving different hydrogen donors uniformly stabilise supramolecular chains in their crystal structures. In order to determine the relative importance of the various intermolecular interactions and packing effects, a computational study using dispersion-corrected density-functional theory was performed on 3 (R = n-Pr). The results showed that the most significant contributors to the stability of the crystal structure are Pd⋯S interactions followed closely by C–H⋯π(PdS2C) interactions. Two non-specific hydrophobic interactions also contribute to the overall packing to a lesser extent. The utility of Pd(S2COR)2 to function as synthetic precursors for PdS nanoparticles and thin films was also investigated. Aerosol-assisted-CVD on representative examples generated PdS films with either matted, needle-like or granular morphologies depending on temperature and substrate. Solvothermal (ethylene glycol) decomposition generated sulphur-rich PdS nanoparticles with diameters 120 nm (7 and 10)–400 nm (8). When dodecanethiol was employed as a capping agent, PdS1.75 nanoparticles <10 nm were generated from 1.

Bis[bis(N-2-hydroxyethyl,N-isopropyl-dithiocarbamato)mercury(II)]2: crystal structure and Hirshfeld surface analysis

Abstract The presence of both κ2-chelating and μ2,κ2-tridentate bridging dithiocarbamate ligands in centrosymmetric {Hg[S2CN(iPr)CH2CH2OH]2}2 (1) leads to globular aggregates that are linked into a three-dimensional architecture via hydroxyl-O–H···O(hydroxy) hydrogen bonding. The structure contrasts that of Hg[S2CN(CH2CH2OH)2]2 (2; this is a literature structure) in which square planar units are connected into supramolecular chains via Hg···S secondary bonding; chains are connected in the crystal structure by hydroxyl-O–H···O(hydroxy) hydrogen bonding. A Hirshfeld surface analysis on 1 and 2 reveal the influence of O–H···O and Hg···S interactions on the molecular packing as well as the distinctive interactions, such as C–H···S interactions in 1 and C–H···π (HgS2C) contacts in 2. A bibliographic survey shows the different structural motifs observed for 1 and 2 are complimented by an additional five motifs for binary mercury(II) dithiocarbamates revealing a fascinating structural diversity for this class of compound.

Exploring the crystallization landscape of cadmium bis(N-hydroxyethyl, N-isopropyldithiocarbamate), Cd[S2CN(iPr)CH2CH2OH]2

Abstract Crystallization of Cd[S2CN(iPr)CH2CH2OH]2 from ethanol yields the coordination polymer [{Cd[S2CN(iPr)CH2CH2OH]2}·EtOH]∞ (1) within 3 h. When the solution is allowed to stand for another hour, the needles begin to dissolve and prisms emerge of the supramolecular isomer (SI), binuclear {Cd[S2CN(iPr)CH2CH2OH]2}2·2EtOH (2). These have been fully characterized spectroscopically and by X-ray crystallography. Polymeric 1 has 2-fold symmetry and features dithiocarbamate ligands coordinating two octahedral Cd atoms in a μ2κ2-tridentate mode. Binuclear 2 is centrosymmetric with two ligands being μ2κ2-tridentate as for 1 but the other two being κ2-chelating leading to square pyramidal geometries. The conversion of the kinetic crystallization product, 1, to thermodynamic 2 is irreversible but transformations mediated by recrystallization (ethanol and acetonitrile) to related literature SI species, namely coordination polymer [{Cd[S2CN(iPr)CH2CH2OH]2}3·MeCN]∞ and binuclear {Cd[S2CN(iPr)CH2CH2 OH]2}2·2H2O·2MeCN, are demonstrated, some of which are reversible. Three other crystallization outcomes are described whereby crystal structures were obtained for the 1:2 co-crystal {Cd[S2CN(iPr)CH2CH2OH]2}2:2[3-(propan-2-yl)-1,3-oxazolidine-2-thione] (3), the salt co-crystal [iPrNH2(CH2CH2OH)]4[SO4]2{Cd[S2CN(iPr)CH2CH2OH]2}2 (4) and the salt [iPrNH2(CH2CH2OH)]{Cd[S2CN(iPr)CH2CH2OH]3} (5). These arise as a result of decomposition/oxidation of the dithiocarbamate ligands. In each of 3 and 4 the binuclear {Cd[S2CN(iPr)CH2CH2OH]2}2 SI, as in 2, is observed strongly suggesting a thermodynamic preference for this form.

Serendipitous compositional and structural diversity in urotropine adducts of binary cadmium xanthates

Abstract Three new compounds, Cd(S2COMe)2(hmta) (1), Cd(S2COEt)2(hmta)0.5 (2) and Cd(S2COiPr)2(hmta) (3), have been isolated from a systematic study of adduct formation between Cd(S2COR)2, R=Me, Et and iPr, precursors and potentially polydentate hmta; hmta is urotropine (hexamethylenetetramine). The compounds have been characterised by a variety of spectroscopic techniques including a photoluminescence study in both solution and the solid-state, as well as by thermal methods. Crystallography shows 1 to have μ2-bridging hmta leading to a one-dimensional coordination polymer. This framework is essentially repeated in 2 but with a μ3-bridging hmta so that Cd(S2COEt)2 entities decorate the chain. By contrast, a binuclear zero-dimensional aggregate with terminally bound hmta is found in 3. The influence of steric bulk of the alkyl substituents in Cd(S2COR)2 is pivotal in determining the ultimate structural outcome.

Crystal structure of bis(μ-N-i-propyl-N-n-propyldithiocarbamato-κ2S:S′) bis(N-i-propyl-N-n-propyldithiocarbamato-κ2S,S′)dizinc(II), C28H56N4S8Zn2

Abstract C28H56N4S8Zn2, monoclinic, P21/n (no. 14), a = 9.4123(2) Å, b = 19.2708(4) Å, c = 11.5228(3) Å, β = 107.202(2)°, V = 1996.54(8) Å3, Z = 2, Rgt(F) = 0.0254, wRref(F2) = 0.0572, T = 100(2) K.

Crystal structure of bis(μ-N-i-propyl-N-n-propyldithiocarbamato-κ3S,S′:S)bis(N-i-propyl-N-n-propyldithiocarbamato-κ2S,S′)dicadmium(II), C28H56Cd2N4S8

Abstract C28H56Cd2N4S8, monoclinic, P21/n (no. 14), a = 9.9003(3) Å, b = 11.7373(3) Å, c = 17.4539(5) Å, β = 102.999(3)°, V = 1976.22(10) Å3, Z = 2, Rgt(F) = 0.0243, wRref(F2) = 0.0582, T = 100 K.

Crystal structures of 5-amino-N-phenyl-3H-1,2,4-di­thia­zol-3-iminium chloride and 5-amino-N-(4-chloro­phen­yl)-3H-1,2,4-di­thia­zol-3-iminium chloride monohydrate

The five-membered 1,2,4-dithiazole rings in the cations of (I) and (II) are almost planar, but in each case the overall cation is twisted with dihedral angles between the planes of the heterocycle and the pendant aryl ring of 9.05 (12) and 15.60 (12)° in (I) and (II), respectively. In both compounds, the bond lengths in the H2N—C—N—C—N backbones imply considerable delocalization of π-electron density.

A new monoclinic polymorph of 1,1′-bis­(di­phenyl­thio­phosphor­yl)ferrocene

In 1,1′-bis(diphenylthiophosphoryl)ferrocene, the S atoms lie to the same side of the molecule. By contrast to this almost syn disposition, in a previous form, the Fe atom lies on a centre of inversion so that the S atoms are strictly anti.

Crystal structure of (N-(3-ethoxy-2-oxidobenzylidene)-4-fluorobenzohydrazonato-κ3N,O,O′)-diphenyltin(IV), C28H23FN2O3Sn

Abstract C28H23FN2O3Sn, orthorhombic, Pbca (no. 61), a = 16.0887(2) Å, b = 14.5333(2) Å, c = 20.5550(2) Å, V = 4806.21(10) Å3, Z = 8, Rgt(F) = 0.0199, wRref(F2) = 0.0596, T = 100(2) K.