Electronic structure of dinuclear gold(i) complexes

Cyclic voltammetry (CV) experiments on LL(AuSR *)(2) complexes [LL = diphenylphosphinomethane (dppm), diphenylphosphinopentane (dpppn); R(*) = p-SC(6)H(4)CH(3)] show anodic sweeps that broaden by about 25 mV on going from the longer (dpppn) to the shorter (dppm) bidentate phosphine ligand. Changing concentrations had no effect on the shape of the waveform. The result suggests a weak intramolecular metal-metal interaction in dppm(AuSR *)(2) that correlates well with rate acceleration occurring in the reaction of dppm(AuSR *)(2) with organic disulfides. Quantum yields for cis-dppee(AuX)(2) [dppee = 1,2-bis(diphenylphosphino)ethylene; X = Cl, Br, I] complexes, (disappearance) Phi , are significantly higher in complexes with a softer X ligand, a trend that correlates well with aurophilicity. This result also suggests that electronic perturbation caused by Au(I)-Au(I) interactions is important in explaining the reactivity of some dinuclear gold(I) complexes. The crystal structure for cis-dppee(Aul)(2) shows short intramolecular Au(I)-Au(I) interactions of 2.9526 (6) A degrees , while the structure of trans-dppee(AuI)(2) , shows intermolecular Au(I)-Au(I) interactions of 3.2292 (9) A degrees . The substitution of .As for P results in a ligand, cis-diphenylarsinoethylene (cis-dpaee), that is photochemically active, in contrast to the cis-dppee ligand. The complexes, cis-dpaee(AuX)(2), are also photochemically active but with lower quantum yields than the cis-dppee(AuX)(2) complexes.     

Redox chemistry of gold(i) phosphine thiolates: sulfur-based oxidation

The redox chemistry of mononuclear and dinuclear gold(I) phosphine arylthiolate complexes was recently investigated by using electrochemical, chemical, and photochemical techniques. We now report the redox chemistry of dinuclear gold(I) phosphine complexes containing aliphatic dithiolate ligands. These molecules differ from previously studied gold(I) phosphine thiolate complexes in that they are cyclic and contain aliphatic thiolates. Cyclic voltammetry experiments of Au(2) (LL)(pdt) [pdt = propanedithiol; LL = 1,2-bis(diphenylphosphino)-ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,4-bis(diphenylphosphino)butane (dppb), 1,5-bis(diphenylphosphino)pentane (dpppn)] in 0.1 M TBAH/CH(3)CN or CH(2)Cl(2) solutions at 50 to 500 mV/sec using glassy carbon or platinum electrodes, show two irreversible anodic processes at ca. +0.6 and +1.1 V (vs. SCE). Bulk electrolyses at +0.9 V and +1.4 V result in n values of 0.95 and 3.7, respectively. Chemical oxidation of Au(2)(dppp)(pdt) using one equivalent of Br(2) (2 oxidizing equivalents) yields 1,2-dithiolane and Au(2)(dppp)Br(2). The reactivity seen upon mild oxidation /= +1.3 V) is consistent with oxidation of gold(I) to gold(III). Structural and electrochemical differences between gold(I) aromatic and aliphatic thiolate oxidation processes are discussed.     

Ag(I)(Et(2)PCH(2)CH(2)PPh(2))(2)]NO(3): An Antimitochondrial Silver Complex

The silver(I) complex [Ag(eppe)(2)]NO(3) (eppe = Et(2)PCH(2)CH(2)PPh(2)) is shown by X-ray crystallography to be tetrahedral with Ag - PEt(2) and Ag - P Ph(2) bond lengths of 2.482 and 2.518 A, respectively. The complex is selectively antimitochondrial and inhibits the growth of a number of yeast strains in non-fermentable media at concentrations as low as 2.5 muMu and induces the mitochondrial mutation petite The effect is largely reversed by the presence of aspirin. The complex is shown to be stable in the cell culture media and in the presence of glutathione, but readily reacts with disulfides of oxidized glutathione and serum albumin. Surprisingly, neither [Au(eppe)(2)]Cl nor [Au(eppe)(2)]Cl (dppe = Ph(2)PCH(2)CH(2)PPh(2)) showed any mitochondrial selectivity in the same screening protocol.     

Self-Assembly of Polymers through Dynamic Coordination Chemistry and Hydrogen Bonding: Polymers from Mercury(II) Halides and Bis(amidopyridine) Ligands

The synthesis of hybrid organic–inorganic polymers by combination of mercury(II) halides with the ligand 1,5-bis(isonicotinamido)naphthalene, C₁₀H₆(NHCO-4-C₅H₄N)₂, 1. The compounds of formula [HgX₂(1)] form either linear (X = Cl, Br) or zig-zag (X = I) polymers and contain tetrahedral mercury(II) centers with bridging ligands 1. The polymers are further assembled by hydrogen bonding between amide groups. When X = Cl or Br, two-dimensional sheet structures are formed whereas, when X = I, a three-dimensional network is formed. A new polymeric form of [HgCl₂(Me₂SO)] is also described. Dedicated to Ian Manners for his pioneering research on organometallic polymers     

Synthesis, Characterisation and Anti-Fungal Activities of Some New Copper(II) Complexes of Octamethyl Tetraaza-Cyclotetradecadiene

The ligand Me(8)[14]diene, L, in its free state as well as in the dihydroperchlorate form, L.2HClO(4), coordinates copper(ll) in different salts to yield a series of [CuLX(x)] X(y)(H(2)O)(z) complexes where X = NO(3), ClO(4), NCS, Cl and Br; x and y may have values of 0 or 2 and z = 0, 1 or 2. The complex, [CuL(ClO(4))(2)].2H(2)O is found to undergo axial ligand substitution reactions with SCN(-), NO(3) and Cl(-) to give a variety of substitution derivatives: [CuL(ClO(4))(m) X(n)] where X = NCS, NO(3) and Cl; m = 0 or 1, and n = 1 or 2. The complexes .have been characterised on the basis of analytical, spectroscopic, magnetic and conductance data. The anti-fungal activities of the ligand and its complexes have been investigated against a range of phytopathogenic fungi.     

Synthesis, Characterisation and Antifungal Activities of Some New Copper(II) Complexes of Isomeric 3,5,7,7,10,12,14,14-Octamethyl-1,4,8,11-Tetraazacyclotetradecanes

Three isomeric Me(8)[14]anes, L(A), L(B) and L(C), undergo complexation with copper(II) salts to form a series of [CuLX(n)(H(2)O)(x)]X(y).(H(2)O)(z) complexes where L = L(A), L(B) and L(C); X = Cl, Br, NO(3); n, x, y and z may have values of 0, 1 or 2. The complexes have been characterised on the basis of analytical, spectroscopic, magnetic and conductance data. Further, the X-ray crystal structure of one complex, [CuL(B)(OH(2))(2)](NO(3))(2), has been determined. The antifungal activity of all three isomeric ligands and their complexes has been investigated against a range of phytopathogenic fungi.     

Antibacterial and Antifungal Activity of Zinc(II) Carboxylates With/Without N-Donor Organic Ligands

The antibacterial and antifungal activity of zinc(II) carboxylates with composition Zn(RCOO)(2)*nH(2)O(R =H-, CH(3) (-), CH(3)CH(2)CH(2) (-), (CH(3))(2)CH-, XCH(2) (-), X=Cl, Br, I, n=0 or 2), [ZnX(2)(Nia(+)CH(2)COO(-))(2)](Nia=nicotinamide, X=Cl, Br, I) and [Zn(XCH(2)COO)(2)(Caf)(2)]*2H(2)O (Car=caffeine, X=Cl, Br) is studied against bacterial strains Staphylococcus aureus, Escherichia coli and yeast Candida albicans. The structural types are assigned to the prepared compounds and the influence of (i) carboxylate chain length, (ii) substitution of hydrogen atom of carboxylate by halogen and (iii) presence of N-donor organic ligands on the biological activity is discussed.     

Complexes With Biologically Active Ligands. Part 7 Synthesis and Fungitoxic Activity of Metal Complexes Containing 1,3,5-tris-(8-Hydroxyquinolino)- Trichlorocyclo-Triphosphazatriene

Complexes containing 1,3,5-tris-(8-hydroxyquinolino)-trichlorocyclotriphosphazatriene, a new cyclophosphazene ligand, and Co(II), Cu(II) and Ni(II) were prepared. The new complexes, having the general formula [MLCl(2)], [ML(2)]Cl(2), (M=Cu, Co, Ni); [NiLAc], [NiL(2)Ac]Ac and [ML(3)]X(3) (M=Ni, Co, X=Cl, Ac) were characterised by elemental analysis, electronic-, IR spectroscopy, and electrical conductivity measurements. Some of them inhibited the growth of several fungi species (Aspergillus and Candida spp.).     

Synthesis, Characterization and Biological Evaluation of Co(II), Cu(II), Ni(II) and Zn(II) Complexes With Cephradine

Some Co(II), Cu(II), Ni(II) and Zn(II) complexes of antibacterial drug cephradine have been prepared and characterized by their physical, spectral and analytical data. Cephradine acts as bidentate and the complexes have compositions, [M(L)(2)X(2)] where [M = Co(II), Ni(II) and Zn(II), L = cephradine and X = Cl(2)] showing octahedral geometry, and [M(L)(2)] where [M = Cu(II), L = cephradine] showing square planar geometry. In order to evaluate the effect of metal ions upon chelation, eephradine and its complexes have been screened for their antibacterial activity against bacterial strains, Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa.     

Structural Diversity of Mercury(II) Halide Complexes Containing Bis-pyridyl-bis-amide with Bulky and Angular Backbones: Ligand Effect and Metal Sensing

Hg(II) halide complexes [HgCl₂] 2L¹ [L¹ = N,N’-bis(3-pyridyl)bicyclo(2,2,2,)oct-7-ene-2,3,5,6-tetracarboxylic diamide), 1, [HgBr₂(L¹)]_n, 2, [HgI₂(L¹)], 3, [Hg₂X₄(L²)₂] [X = Cl, 4, Br, 5, and I, 6; L² = N,N’-bis(4-pyridylmethyl)bicyclo(2,2,2,)oct-7-ene-2,3,5,6-tetracarboxylic diamide] and {[HgX₂(L³)]⋅H₂O}_n [X = Cl, 7, Br, 8 and I, 9; L³ = 4,4′-oxybis(N-(pyridine-3-yl)benzamide)] are reported and structurally characterized using single-crystal X-ray diffraction analyses. The linear HgCl₂ units of complex 1 are interlinked by the L¹ ligands through Hg---N and Hg---O interactions, resulting in 1D supramolecular chains. Complex 2 shows 1D zigzag chains interlinked through the Br---Br interactions to form 1D looped supramolecular chains, while the mononuclear [HgI₂L²] molecules of 3 are interlinked through Hg---O and I---I interactions, forming 2D supramolecular layers. Complexes 4–6 are isomorphous dinuclear metallocycles, and 7–9 form isomorphous 1D zigzag chains. The roles of the ligand type and the halide anion in determining the structural diversity of 1–9 is discussed and the luminescent properties of 7–9 evaluated. Complexes 7–9 manifest stability in aqueous environments. Moreover, complexes 7 and 8 show good sensing towards Fe³⁺ ions with low detection limits and good reusability up to five cycles, revealing that the Hg-X---Fe³⁺ (X = Cl and Br) interaction may have an important role in determining the quenching effect of 7 and 8.     

Unexpected reactivity of Au25(SCH2CH2Ph)18 nanoclusters with salts

We report some interesting results of the chemical reactivity of thiolate-protected [Au(25)(SCH(2)CH(2)Ph)(18)](0) nanoclusters with two types of salts, including tetraoctylammonium halide (TOAX) and NaX. At the early stage of the reaction, [Au(25)(SCH(2)CH(2)Ph)(18)](0) was found to spontaneously convert to its anionic form ([Au(25)(SCH(2)CH(2)Ph)(18)](-)) in the presence of either type of salt. However, a large difference was observed in the second stage of the reaction. With NaX, we observed decomposition of anionic clusters, while with TOAX, the clusters show excellent stability. We have gained some insight into the reaction mechanism. The X(-) ions seem to attack [Au(25)(SCH(2)CH(2)Ph)(18)](q) surface and displace some thiolates, evidenced by the observation of halide-bound clusters such as Au(25)(SCH(2)CH(2)Ph)(18-x)Br(x) in mass spectrometry analysis. These halide-bound clusters show a reduced stability, and their decomposition into Au(I) complexes leads to the release of gold valence electrons of the clusters; concurrently, the non-halide-bound [Au(25)(SCH(2)CH(2)Ph)(18)](0) clusters are reduced into [Au(25)(SCH(2)CH(2)Ph)(18)](-). For the second stage of reaction with organic salts such as TOA-Br, after [Au(25)(SCH(2)CH(2)Ph)(18)](0) clusters are converted to [Au(25)(SCH(2)CH(2)Ph)(18)](-)) the TOA(+) counterions surprisingly protect the anionic clusters from further attack by halide ions, hence, TOA(+) cations can stabilize [Au(25)(SCH(2)CH(2)Ph)(18)](-) clusters. In contrast, with NaX salts the Na(+) ions do not provide any steric stabilization of the [Au(25)(SCH(2)CH(2)Ph)(18)](-) clusters, hence, degradation occurs when being further attacked by halide ions, especially Br(-) and I(-).     

Bone Repair Stimulation in Rat Mandible by New Chitosan Silver(I) Complexes

Two new chitosan silver(I) complexes, [Ag(2CS)(H₂O)(NO₃)] and [Ag(2CS)(ahmp)(H₂O)] (CS = chitosan, Hahmp = 4-amino-6-hydroxy-2-mercaptopyrimidine) were synthesized and characterized on the basis of elemental analysis, spectral (FT-IR and solid-state ¹³C-NMR), morphological (SEM, matrix analysis, XRD, and XRPE), and thermal measurements. Chitosan behaves as a neutral ligand, coordinates Ag(I) through half of amino nitrogen centers, with the pendant glucose amine hydroxy functionality playing no role in coordination, while 4-amino-6-hydroxy-2-mercaptopyrimidine functions as mononegative bidentate, chelating through the deprotonated cyclic nitrogen and thione sulfur atoms. [Ag(2CS)(ahmp)(H₂O)] displays a significant potential bone regenerator in rat mandible. Forty male rats were divided into two groups: bone defect (control) and bone defect with [Ag(2CS)(ahmp)(H₂O)] (treated). The bone defects were stained with hematoxylin and eosin, and Masson's trichrome for histological analysis. The treated group shows faster and well organized bone formation in the defect in comparison to the control group which shows little new bone trabeculae and wide marrow cavities.     

Comparative Analysis of [Au(en)(2)] and [Pt(en)(2)] non Covalent Binding to Calf Thymus DNA

Reactions of the complexes bisethylendiammine gold(III) and bisethylendiammine platinum(II) with calfthymus DNA were comparatively analysed. Both complexes bind DNA non-covalently most probably on the basis of electrostatic interactions. Binding of either complex at low ratios results into modest modifications of B-type DNA conformations, as detected by CD. Far larger CD alterations are observed at high ratios. The gold(III) chromophore is scarcely perturbed by DNA addition Binding of [Au(en)(2)]Cl(3) to calf thymus DNA is reversed by sodium cyanide. By analogy with the case of [Pt(en)(2)]Cl(2) it is suggested that Auen acts as a minor groove binder.     

Synthesis and Anti-Candida Activity of Cobalt(II) Complexes of Benzene-1,2-Dioxyacetic Acid (bdoaH(2)). X-Ray Crystal Structures of [Co(bdoa)(H(2)O)(3)] 3.5H(2)O and {[CO(phen)(3)](bdoa)}(2)24H(2)O (phen = 1,10-Phenanthroline)

Co(CH(3)CO(2))(2)4H(2)O reacts with benzene-1,2-dioxyacetic acid (bdoaH(2)) to give the Co(2+) complexes [Co(bdoa)(H(2)O)(3)]H(2)O (1a) and [Co(bdoa)(H(2)O)(3)] 3.5H(2)O (1b). Subsequent reaction of 1a with 1,10- phenanthroline produces [CO(phen)(3)] bdoa10H(2)O (2a) and {[CO(phen)(3)](bdoa)}(2)24H(2)O (2b). Molecular structures of 1b and 2b were determined crystallographically. In 1b the bdoa(2-)- ligates the metal by two carboxylate oxygens and two ethereal oxygens, whereas in 2b the bdoa(2-) is uncoordinated. The Mn(2+) and Cu(2+) complexes [Mn(bdoa)(phen)(2)]H(2)O (3) and [Cu(pdoa)(imid)(2)] (4) were also synthesised, 1a-4 and other metal complexes of bdoa H(2) (metal = Mn(2+), Co(2+) ,Cu(2+), Cu(+) ) were screened for their ability to inhibit the growth ofhe yeast Candida albicans. Complexes incorporating the 1,10-phenanthroline ligand were the most active.     

Facile synthesis and optical properties of magic-number Au13 clusters

Synthesis of molecular gold clusters through a post-synthetic scheme involving HCl-promoted nuclearity convergence was examined with various phosphine ligands. Systematic studies with a series of bis(diphenylphosphino) ligands (Ph(2)P-(CH(2))(m)-PPh(2)) using electrospray ionization mass spectrometry (ESI-MS) and electronic absorption spectroscopy demonstrated that the use of dppp (m = 3), dppb (m = 4) and dpppe (m = 5) as the ligands resulted in the formation of [Au(13)P(8)Cl(4)](+) type clusters, whereas the [Au(13)P(10)Cl(2)](3+) type cluster was formed with dppe (m = 2). The cluster species did not survive the HCl treatment step when monophosphines PPh(3), PMe(2)Ph, and POct(3) were employed, but [Au(13)(POct(3))(8)Cl(4)](+) was isolated as a minor product in the NaBH(4) reduction of Au(POct(3))Cl in aqueous THF. Electronic absorption and photoluminescence studies of a series of Au(13) clusters revealed that their optical properties are highly dependent on the phosphine/chloride composition ratio, but are far less so on the phosphine structure.     

Interaction of [Rh(2)(O(2)CCH(3))(4)(H(2)O)(2)] and [Rh(2)(O(2)CCH(OH)Ph)(2)(phen)(2)(H(2)O)(2)](O(2)C-CH(OH)Ph)(2) With Sulfhydryl Compounds and Ceruloplasmin

The interaction of binuclear rhodium(II) complexes [Rh(2)(OOCCH(3))(4)(H(2)O)(2)], [Rh(2){OOCCH(OH)Ph}(2)(phen)(2)(H(2)O)(2)] {OOCCH(OH)Ph}(2), [Rh(2)(OOCCH(3))(2)(bpy)(2)(H(2)O)(2)](OOCCH(3))(2) and [Rh(2)Cl(2)(OOCMe)(2)(bpy)(2)](3H(2)O) with ceruloplasmin, cysteine, glutathione and coenzyme A have been investigated using. UV-Vis and CD spectroscopies. The complexes containing phen or bpy at pH = 7.4 and 4.0 are readily reduced with sulfhydryl compounds, while rhodium(II) acetate is relatively stable in these conditions. Complex [Rh(2){OOCCH(OH)Ph}(2)(phen)(2)(H(2)O)(2)] strongly changes structure of ceruloplasmin leading to the decrease of of alpha-helix content and loss of oxidase activity.     

Preparation of mono(dimethylglyoxime)(triphenylphosphine)-halogenocobalt(I) complexes and their application as homogeneous catalysts in reduction of aromatic nitrocompounds

The complexes [Co(I)(DMGH)(PPh₃)X].C₂H₅OH (X? Cl/Br) have been prepared and characterised by elemental analysis, infrared and electronic spectral studies and magnetic measurements. These compounds have been used as homogeneous catalysts for the reduction of nitrobenzene at atmospheric and higher pressures. From a study of various operational parameters, it has been observed that the reduction at atmospheric pressure was only possible in a basic ethanolic medium and resulted in 64% of azobenzene on input nitrobenzene basis whereas at higher pressure (4.2 × 10³ kN/m²), 60% of aniline on the same basis could be obtained in neutral ethanolic medium. The optimum conditions were established both under normal pressure and under high pressure.     

用XRD研究半胱氨酸与砷、锑、铋配合物的固相合成反应

用固相反应法合成了半胱氨酸与碘化砷、氯化锑、碘化锑、氯化铋、碘化铋的配合物 ,其组成为 :ML3X3(M =As、Sb、Bi,L =Cys ,X =I、Cl) ,通过XRD谱的研究说明配合物的形成。这些配合物在空气中稳定 ,不吸湿 ,微溶于水。As(Cys) 3I3配合物的晶胞参数为 :a=1.1743nm ,b =0 .6945nm ,c=1.682 2nm ,β =95 .2 8° ,V =1.3 661nm3;Sb(Cys) 3Cl3配合物的晶胞参数为 :a =1.2 0 5 1nm ,b =0 .6792nm ,c =1.685 0nm ,β =95 .79° ,V =1.3 72 1nm3,其晶体结构均属于单斜晶系     

Synthesis,characterization, and catalytic applications of Ru(III) complexes containing N-[di(alkyl/aryl)carbamothioyl]benzamide derivatives and triphenylphosphine/triphenylarsine

Six coordinated ruthenium(III) complexes of the type [RuX₂(L)(PPh₃)₂] or [RuX₂(L)(AsPh₃)₂] {where L = N-[di(alkyl/aryl)carbamothioyl]benzamide derivatives, X = Cl or Br} have been prepared by the reaction between [RuX₃(PPh₃)₃] or [RuX₃(AsPh₃)₃] (where X = Cl or Br) and N-[di(alkyl/aryl)carbamothioyl]benzamide derivatives in toluene and characterized by elemental analysis, spectral data (electronic, IR and EPR) and magnetic moment studies. The complexes act as efficient catalysts for the oxidation of alcohols in presence of N-methylmorpholine-N-oxide as oxidant at room temperature.     

Binuclear Rhodium(II) Complexes With Selective Antibacterial Activity

Binuclear rhodium(II) complexes [Rh(2)Cl(2)(mu-OOCR)(2)(N-N)(2)] {R = H, Me; N-N = 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen)} and [Rh(2)(mu-OOCR)(2)(N-N)(2)(H(2)O)(2)](RCOO)(2) (R = Me, Et;) have been synthesized and their structure and properties have been studied by electronic, IR and (1)H NMR spectroscopy. Antibacterial activity of these complexes against Escherichia coli and Staphylococcus aureus has been investigated. The most active antibacterial agents against E. coli were [Rh(2)Cl(2)(mu-OOCR)(2)(N-N)(2)] and [Rh(2)(mu-OOCR)(2)(N-N)(2)(H(2)O)(2)](RCOO)(2) {R = H and Me} which were considerably more active than the appropriate nitrogen ligands. The complexes show low activity against S. aureus. The activity of the complexes [Rh(2)(OOCR)(2)(N-N)(2)(H(2)O)(2)](OOCR)(2) against E. coli decreases in the series: R=H congruent withCH(3)>C(2)H(5)>C(3)H(7) congruent withC(4)H(9). The reverse order was found in the case of S. aureus.