Different coordination modes of a tripod phosphine in gold(i) and silver(i) complexes

The following gold(I) and silver(I) complexes of the tritertiary phosphine 1,1,1- tris(diphenylphosphinomethyl)ethane, tripod , have been synthesised: Au(3)(tripod)X(3) [X = Cl(1), Br(2), I(3)]; [Au(3)(tripod)(2)Cl(2)]Cl (4); Au(tripod)X [X = Br(5), I(6)]; Ag(3)(tripod) (NO(3))(4) (7), Ag(tripod)NO(3) (8). They were characterized by X-ray diffraction (complexes 2, 3 and 4), (31)P NMR spectroscopy, electrospray and FAB mass spectrometry and infrared spectroscopy. Complexes 2 and 3 show a linear coordination geometry for Au(I), with relatively short Au-P bond distances. Complex 3 has a Au***Au intramolecular distance of 3.326 A degrees , while complex 2 had a short Au***Au intermolecular interaction of 3.048 A degrees . Complexes 4-6 were found by (31)P NMR spectroscopy studies to contain a mixture of species in solution, one of which crystallised as [Au(3)(tripod|)(2)Cl(2)]Cl which was shown by X-ray diffraction to contain both tetrahedral and linear Au(I), the first example of a Au(I) complex containing such a mixture of geometries. The reaction of [Au(3) (tripod)Cl(3)] (1) with tripod led successfully to the formation of [Au(3)(tripod|)(2)Cl(2)](+) and [Au(3)(tripod)(2)Cl(3)](+) and [Au(3)(tripod|)(3)Cl](2+). The silver(I) complexes, 7 and 8 appear to contain linear and tetrahedral Ag(I), respectively.     

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.     

Au25(SG)18 as a fluorescent iodide sensor

The recently emerging gold nanoclusters (GNC) are of major importance for both basic science studies and practical applications. Based on its surface-induced fluorescence properties, we investigated the potential use of Au(25)(SG)(18) (GSH: glutathione) as a fluorescent iodide sensor. The current detection limit of 400 nM, which can possibly be further enhanced by optimizing the conditions, and excellent selectivity among 12 types of anion (F(-), Cl(-), Br(-), I(-), NO(3)(-), ClO(4)(-), HCO(3)(-), IO(3)(-), SO(4)(2-), SO(3)(2-), CH(3)COO(-) and C(6)H(5)O(7)(3-)) make Au(25)(SG)(18) a good candidate for iodide sensing. Furthermore, our work has revealed the particular sensing mechanism, which was found to be affinity-induced ratiometric and enhanced fluorescence (abbreviated to AIREF), which has rarely been reported previously and may provide an alternative strategy for devising nanoparticle-based sensors.     

Properties of Binuclear Rhodium(II) Complexes and Their Antibacterial Activity

Binuclear rhodium(II) complexes [Rh(2)Cl(2)(mu-OOCR)(2)(N-N)(2)], [Rh(2)(mu-OOCR)(2)(N-N)(2)(H(2)O)(2)](RCOO)(2) and [Rh(2)Cl(2)(mu-OOCCH(3))(terpy)(2)](H(3)O)Cl(2).9H(2)O (R = H, Me, Bu(n), ph, PhCHOH; N-N = 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), 2,9-dimethyl-1,10-phenanthroline (dmp) and 6,7-dimethyl-2,3- di(2-pyridyl)quinoxaline (dmpq); terpy 2,2':6',2'-terpyridine) 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 Staphylococcus aureus and Escherichia coli has been investigated. The most active antibacterial agents against S. aureus were [Rh(2)(OOCPh)(2)(phen)(2)(H(2)O)(2)](2+), [Rh(2)(OOCPh)(2)(dmpq)(2)(H(2)O)(2)](2+), [Rh(2)(OOCBu)(2)(phen)(2)(H(2)O)(2)](2+) and [Rh(2)-(OOCBu)(2)(bpy)(2)(H(2)O)(2)](2+) which were considerably more active than the appropriate nitrogen ligands. The complexes show rather low activity against E. coli.     

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.     

Reactions of organic disulfides and gold(i) complexes

Gold-thiolate/disulfide exchange reactions of (p-SC(6)H(4)Cl)(2) with Ph(3)PAu(SC(6)H(4)CH(3)), dppm(AuSC(6)H(4)CH(3))(2), and dppe(AuSC(6)H(4)CH(3)) (2) were investigated. The rate of reactivity of the gold-thiolate complexes with (p-SC(6)H(4)Cl)(2) is: dppm(AuSC(6)H(4)CH(3))(2)> dppe(AuSC(6)H(4)CH(3))(2)>Ph(2)PAu (SC(6)H(4)CH(3)). This order correlates with conductivity measurements and two ionic mechanisms have been evaluated. (1)H NMR experiments demonstrate that in the reaction of dppm(AuSC(6)H(4)CH(3))(2) with (p-SC(6)H(4)Cl)(2), the mixed disulfide, ClC(6)H(4)SSC(6)H(4)CH(3), forms first, followed by the formation of (p-SC(6)H(4)CH(3))(2). The rate law is first order in (pp-SC(6)H (4)Cl)(2) and partial order in dppm(AuSC(6)H(4)CH(3))(2). Results from electrochemical and chemical reactivity studies suggest that free thiolate is not involved in the gold-thiolate/disulfide exchange reaction. A more likely source of ions is the dissociation of a proton from the methylene backbone of the dppm ligand which has been shown to exchange with D(2)O. The implications of this are discussed in terms of a possible mechanism for the gold-thiolate/disulfide exchange reaction.     

Progress in the chemistry of metallabenzynes

The synthesis and chemical and structural properties of metallabenzynes are reviewed. Reaction of [OsCl(2)(PPh(3))(3)] with HC(triple bonded)CSiMe(3) produces the osmabenzyne [Os((triple bonded)CC(SiMe(3))=C(CH(3))C(SiMe(3))=CH)Cl(2)(PPh(3))(2)], which undergoes electrophilic substitution reactions with HBF(4) and Br(2) to give new osmabenzynes. The reactivities and the X-ray diffraction data of osmabenzynes indicate that these metallacycles have aromatic properties. Unlike benzyne, which is thermally unstable, osmabenzynes are thermally much more stable and can be stored for months at room temperature without decomposition. The higher thermal stability of osmabenzynes compared to benzyne can be related to the relatively smaller ring strain and larger conjugation energy.     

Analysis of platinum adducts with DNA nucleotides and nucleosides by capillary electrophoresis coupled to ESI-MS: indications of guanosine 5'-monophosphate O6-N7 chelation

DNA is the ultimate target of platinum-based anticancer therapy. Since the N7 of guanine is known to be the major binding site of cisplatin and its analogues, adduct formation with model nucleotides, especially 2'-deoxyguanosine 5'-monophosphate (dGMP), has been studied in detail. During the last few years a coupled capillary eletrophoresis/electrospray-ionization mass spectrometry (CE/ESI-MS) method has been advantageously used in order to separate and identify platinum adducts with nucleotides in submillimolar concentrations in aqueous solutions. Beside the bisadduct, [Pt(NH(3))(2)(dNMP)(2)](2-) (NMP=2'-deoxynucleoside 5'-monophosphate), and the well-known monochloro and monohydroxo adducts, [Pt(NH(3))(2)Cl(dNMP)](-) and [Pt(NH(3))(2)(dNMP)OH](-), respectively, a third kind of monoadduct species with a composition of [Pt(NH(3))(2)(dNMP)](-) can be separated by CE and detected through the m/z values measured with ESI-MS. Different experimental setups indicate the existence of an O(6)-N7 chelate, whereas the formation of N7-alphaPO(4) macrochelates or dinuclear species is unlikely. Additionally, offline MS experiments with 2'-deoxyguanosine (dG) and stabilization of the controversially discussed O(6)-N7 chelate by oxidation with hydrogen peroxide support the assumption of the existence of O(6)-N7 chelation.     

THE SOLVENT EXTRACTION OF ZINC FROM LITHIUM CHLORIDE BY ALIQUAT 336 CHLORIDE,BROMIDE AND IODIDE IN CHLOROFORM: AN ANALYTICAL INVESTIGATION

ABSTRACT

The extraction of zinc by Aliquat CI in chloroform is studied as a function of LiCl concentration. A plot of log D versus total [Cl] shows that log D increases sharply from 0-2 M LiCl, then remains constant over a considerable range of concentrations ( 2-8 M ), before shooting up again from 8-14 M. Further work is carried out at 4 M LiCl to determine the extraction equation, and quantitative aspects determined such as a plot of log D versus log [Aliquat Cl]_free, giving a ratio of 2:1 for extractant: metal, and the ratio [Cl / Zn]_extracted, which is 2.

In order to follow the exchange of halides across the interface, Aliquat Br and Aliquat I are used as extractants in chloroform to study the extraction of zinc chloride from 4 M LiCL Organic and aqueous phases are analysed for halides and zinc, and the ratio [ΔCl] / [Zn] in the organic phase determined to be 3 for both Aliquat Br and I at 4M LiCl, indicating extraction of ZnCl₃,' and not ZnCl₄ ² at this concentration. Further work with these extractants based on plots of log D versus log [Aliquat X]_free ( X = Br, I ) is presented and extraction equations are proposed for these extractants, which fit the data.

Extraction of zinc at 4 M LiCl by Aliquat Cl is then considered in terms of the extraction of the trichlorozincate (II) species, ZnCl₃,“, and the extraction constant determined.     

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.     

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.     

CH3Cl在ZnO(001)和ZnO(100)表面吸附的第一性原理计算

基于密度泛函理论的第一性原理方法,建立ZnO(100)和ZnO(001)表面的吸附模型,计算了吸附能、电荷密度、态密度以及过渡态等参数,研究了CH3Cl在ZnO不同表面、不同位点、不同吸附方式的吸附情况。结果表明,CH3Cl在ZnO(100)和ZnO(001)表面的吸附过程均为化学吸附。当CH3Cl整体吸附时,CH3Cl分子中的Cl原子可以与ZnO表面的Zn(2a)原子生成Zn-Cl键,CH3Cl在ZnO(100)表面的吸附能比在ZnO(001)表面的吸附能更低(-0.57 eV vs. -0.42 eV),体系更稳定;并且CH3Cl在ZnO(100)面吸附后,Cl原子的3p轨道态密度峰向左移动,且靠近费米能级处的峰值降低,表明Cl原子在吸附过程中提供电子,与Zn形成更稳定的相互作用。当CH3Cl解离吸附时,甲基自由基中的C原子可以分别与ZnO(100)表面的O(2a)和O(3a)吸附,CH3Cl解离吸附在Zn(2a)和O(2a)原子处的吸附能为-1.09 eV,在费米能级左侧O 2p轨道和C 2p轨道存在3个共振峰,证明C原子和O原子有较强的相互作用,而在Zn(2a)和O(3a)原子处的吸附能为-1.02 eV,且费米能级右侧O 2p轨道和C 2p轨道存在1个共振峰,表明C和O原子存在反键作用。过渡态的计算结果表明,CH3Cl解离吸附在Zn(2a)和O(2a)位点的过渡态能垒比在Zn(2a)和O(3a)位点更低(1.69 eV vs. 2.06 eV),因此CH3Cl解离吸附反应倾向于在ZnO(100)表面上相邻的Zn和O原子之间发生。     

1, 2-苯并-异噻唑啉-3-酮与锌(Ⅱ)、铜(Ⅱ)配合物的合成及其抑菌性

1,2-苯并-异噻唑啉-3-酮(BIT)与醋酸锌、醋酸铜反应得到配合物[Zn(BIT-H)2](1)及[Cu(BIT)(BIT-H)(CH3COO)](2);通过元素分析、核磁共振、红外光谱和紫外可见分析等手段对配合物结构进行表征。将配合物1和配合物2分别做抑菌实验,它们对大肠杆菌的最小抑菌质量浓度分别为2.344×10-3、1.172×10-3 g/L,对金黄色葡萄球菌的最小抑菌质量浓度分别为5.86×10-4、5.86×10-4 g/L,配合物的抑菌性能很好。     

Alternating copolymerization of carbon dioxide and propylene oxide by single-component cobalt salen complexes with various axial group

A series of single-component cobalt salen complexes, N,N′-bis(salicylidene)-1,2phenylenediamino cobaltIII X (X = Cl (1a), Br (1b), NO3 (1c), CF3COO (1d), BF4 (1e), and N3 (1f)) (SalphCoX), were prepared for alternating copolymerization of carbon dioxide and propylene oxide(PO) under mild condition. The axial anion X group of the SalenphCoX played important role in tailoring the catalytic activity, polymeric/cyclic carbonate selectivity, as well as stereochemistry of carbonate unit sequence in the polymer chain. SalenphCoX with an electron-withdrawing axial X group (complex 1c) was an ideal catalyst for the copolymerization of CO2 and PO to selectively produce polycarbonate with ∼99% carbonate linkage and over 81% head-to-tail structure.     

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.     

Oxidative addition of Se–X bonds and reductive elimination of Se–C bonds in platinum compounds containing hydrocarbyl ligands

The oxidative addition of PhSe–X molecules (X=Cl or Br) to Pt(II) complexes of formula [PtR(R^′)(N,N-chelate)] [R, R^′=Me, CH(CO₂Me)₂, CH(CO₂Me)(CN); N,N-chelate=4,4^′-(tert-butyl)₂-2,2^′-bipyridine] is described. The reaction quantitatively affords octahedral products [PtR(R^′)(SePh)(X)(N,N-chelate)], and is highly selective, since only the isomers with -X and -SePh in trans position are obtained. When R=R^′=CH(CO₂Me)₂ or R=R^′=CH(CO₂Me)₂(CN) an irreversible reductive elimination takes place in solution, giving rise to Pt(II) compounds [PtR(X)(N,N-chelate)] and organoselenium molecules PhSeR^′.     

Antibacterial Role of SO(4), NO(3), C(2)O(4) and CH(3)CO(2) Anions on Cu(II) and Zn(II) Complexes of a Thiadiazole-derived Pyrrolyl Schiff Base

A condensation reaction of 2-amino-1,3,4-thiadiazole with 2-pyrrolecarboxaldehyde to form tridentate NNN donor Schiff base has been performed. The prepared Schiff base was further used for the formation of metal complexes having stoichiometry [M(L)(2)]X(n), where M=Cu(II) or Zn(II), L=N-(2-pyrrolylmethylene)-2-amino-1,3,4-thiadiazole, X=SO(4) (2-), NO(3) (-), C(2)O(4) (2-) or CH(3)CO(2-) and n=1 or 2. The new compounds described here have been characterized by their physical, spectral and analytical data, and have been screened against several bacterial strains such as Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. The antibacterial potency of the Schiff base increased upon chelation/complexation, having the same metal ion (cation) but different anions opening up a novel approach in finding new ways to fight against antibiotic resistant strains.     

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(-).     

Synthesis, In vitro Antifungal and Antitumour Activity of Some Triorganotin(IV) N,C,N-Chelates

The in vitro antifungal activity of compounds 1-3 ({[(CH3)2NCH2]2C6H3}R2SnX; (where X=Cl, R=n-Bu for 1, X=Br, R=n-Bu for 2 and x=PF6, R=n=Bu for 3)) was estimated with the help of a modified microdilution format of the M27-A guidelines and was compared with in vitro activity of their diphenyltin(IV) analogues 4 and 5 (where X=Br, R=Ph for 4 and X=PF6, R=Ph for 5), and of drugs currently in clinical use (ketoconazole, fluconazole and amphotericin B). It was found that in coordinating solvents the more soluble derivative 2 is less active than the phenyl one (4), and compounds 1 and 3 are even inactive.In this paper, the in vitro antitumour activity of ionic diphenyltin(IV) complexes 4 and 5 against seven tumoural cell lines of human origin is also reported. The preparation and characterization (H1, C13 and Sn119 NMR spectroscopy and electrospray ionization mass spectrometry) of the novel compound 3 is mentioned too.