Systematic Modulation of the Fluorescence Brightness in Boron‐Dipyrromethene (BODIPY)‐Tagged N‐Heterocyclic Carbene (NHC)–Gold–Thiolates

Five different highly fluorescent boron‐dipyrromethene (BODIPY)‐tagged N‐heterocyclic carbene NHC–gold halide complexes were synthesized. The substitution of the halogeno ligand by 4‐substituted aryl thiolates leads to a decrease in the brightness of the complexes. This decrease depends on the electronic nature of the thiols, being most pronounced with highly electron‐rich thiols (4‐R=NMe₂). The brightness of the gold thiolates also depends on the distance between the sulfur atom and the BODIPY moiety. The systematic variation of the electron density of [(NHC–bodipy)Au(SC₆H₄R)] (via different R groups) enables the systematic variation of the fluorescence brightness of an appended BODIPY fluorophore. Based on this and supported by DFT calculations, a photoinduced electron‐transfer quenching appears to be the dominant mechanism controlling the brightness of the appended BODIPY dye.     

Tris(thioimidazolyl)borate-zinc-thiolate complexes for the modeling of biological thiolate alkylations

The S3Zn-SR coordination of thiolate-alkylating enzymes such as the Ada DNA repair protein was reproduced in tris(thioimidazolyl)borate-zinc-thiolate complexes Tti(R)Zn-SR'. Four different Tti(R) ligands and nine different thiolates were employed, yielding a total of 12 new complexes. In addition, one Tti(R)Zn-SH complex and two thiolate-bridged [Tti(R)-SEt-Tti(R)]+ complexes were obtained. A selection of six thiolate complexes was converted with methyl iodide to the corresponding methyl thioethers and Tti(R)Zn-I. According to a kinetic analysis these reactions are second-order processes, which implies that the alkylations are likely to occur at the zinc-bound thiolates. They are much faster than the alkylations of zinc thiolates with N3 or N2S tripod ligands. The most reactive thiolate, Tti(Xyl)Zn-SEt, reacts slowly with trimethyl phosphate in a nonpolar medium at room temperature, yielding methyl-ethyl-thioether and Tti(Xyl)Zn-OPO(OMe)2 which can be converted back to the thiolate complex with NaSEt. This is the closest reproduction of the Ada repair process so far.     

Building layer-by-layer a bis(dithiocarbamato)copper(II) complex on Au[111] surfaces

A bis(dithiocarbamato)copper(II) complex (CuDTC2) was built on Au{111} surfaces (sheets and electrode beads) using different building blocks in a layer-by-layer (LbL) procedure. The process was followed by AFM and cyclic voltammetry. Initially 4-piperidinemethanethiol, which was synthesized here for the first time, was self-assembled on a gold surface and a highly organized array was obtained. The resulting monolayer was treated with CS2 and NH3 to transform the NH groups of piperidine into dithiocarbamate groups (DTC) with the formation of an amphiphilic ligand (DTCpipS) with thiolate and DTC terminal anionic groups. Two reductive desorption peaks were observed in the cyclic voltammogram of self-assembled DTCpipS, a more intense peak at -0.87 V (thiolate group) and a broader, less intense peak at -0.68 V, corresponding to the desorption of the DTC group bound to the gold surface after the ligand made a approximately 180 degrees flip on the surface. Copper(II) and the morpholyldithiocarbamate anion were associated with self-assembled DTCpipS in order to complete the formation of the CuDTC2 complex on the gold surface. In the voltammogram of the LbL self-assembled CuDTC2 complex the reductive desorption peak at -0.68 V disappeared and one single peak was observed at -0.85 V. This corresponds to the reorientation of all of the DTCpipS dianions in order to coordinate to copper(II) through the DTC groups, leaving the self-assembly only through the thiolate groups. The complete formation of the LbL self-assembled CuDTC2 complex was confirmed by XPS and ToF SIMS, with a detected fragment corresponding to the whole complex.     

Preparation,characterization and biological evaluation of copper(II) and zinc(II) complexes with Schiff bases derived from amoxicillin and cephalexin

Copper(II) and zinc(II) complexes of Schiff bases obtained by condensation of amoxicillin and cephalexin with salicylaldehyde/pyridoxal were prepared and characterized by microanalytical, thermogravimetric, magnetic and spectroscopic data. All the complexes were found to be six‐coordinate and containing two water molecules. The electron paramagnetic resonance spectral lines exhibited rhombic distortion from axial symmetry, with g_|| > g_? > g_e, in the copper(II) complexes. The geometry of the zinc(II) complexes appears to be octahedral. All the compounds under investigation showed antibacterial activity. The antibacterial activity showed the following trend: copper(II) complexes > zinc(II) complexes > Schiff base ligands > parent drugs. The copper(II) complexes with the Schiff bases derived from cephalexin showed substantially enhanced activity against Pseudomonas aeruginosa compared with the parent drug. All the copper complexes were also found to be active against kaolin paw oedema, whereas the parent drugs were inactive. Copyright © 2005 John Wiley & Sons, Ltd.     

Iron(I)-Based Carbonyl Complexes with Bridging Thiolate Ligands as Light-Triggered CO Releasing Molecules (photoCORMs)

A series of thiolate ligands were used to synthesize diiron(I) hexacarbonyl bis(thiolates) for structural studies. Conversion of the corresponding thiols with triiron(0) dodecacarbonyl yields complexes of the type [{(CO)₃Fe(μ-SR)}₂] [R = C₆H₅ ( 1 ), C₆H₄-4-CH₃ ( 2 ), C₆H₄-4-F ( 3 ), C₆F₅ ( 4 ), C₆H₄-4-CF₃ ( 5 ), C₆H₂-2,4,6-(CH₃)₃ ( 6 ), CH₂–C₆H₄-4-Cl ( 7 )]. These complexes were isolated and fully characterized, including X-ray crystal structures of complexes 2 – 7 . The bridging thiolate ligands mainly influence the Fe–CO bond which is trans-positioned to the second iron(I) center. In solution, the anti-isomer with one axially and one equatorially oriented thiolate is the major species; severe steric strain induced by mesityl groups only allows the formation of syn-endo-isomeric molecules of 7 . Furthermore, light-induced CO release at solid material at the three representative complexes 1 , 3 , and 6 verify suitability as photoCORMs.     

Transformation of the {Fe(NO)2}9 dinitrosyl iron complexes (DNICs) into S-nitrosothiols (RSNOs) triggered by acid-base pairs

S‐Nitrosation of the coordinated thiolate of dinitrosyl iron complexes (DNICs) to generate S‐nitrosothiols (RSNOs) was demonstrated. Transformation of [{(NO)₂Fe(μ‐StBu)}₂] ( 1‐tBuS ) into the {Fe(NO)₂}⁹ DNIC [(NO)₂Fe(StBu)(MeIm)] ( 2‐MeIm ) occurs under addition of 20 equiv of 1‐methylimidazole (MeIm) into a solution of 1‐tBuS in THF. The dynamic interconversion between {Fe(NO)₂}⁹ [(NO)₂Fe(S‐NAP)(dmso)] ( 2‐dmso ) (NAP=N‐acetyl‐D ‐penicillamine) and [{(NO)₂Fe(μ‐S‐NAP)}₂] ( 1‐NAP ) was also observed in a solution of complex 1‐NAP in DMSO. In contrast to the reaction of complex 2‐MeIm and bis(dimethylthiocarbamoyl) disulfide ((DTC)₂) to yield {Fe(NO)}⁷ [(NO)Fe(DTC)₂] ( 3 ) (DTC=S₂CNMe₂) accompanied by (tBuS)₂ and NO_(g), transformation of {Fe(NO)₂}⁹ 2‐MeIm ( 2‐dmso ) into RSNOs (RS=tBuS, NAP‐S) along with complex 3 induced by the Brønsted acid solution of (DTC)₂ demonstrated that Brønsted acid may play a critical role in triggering S‐nitrosation of the coordinated thiolate of DNICs 2‐MeIm (or 2‐dmso ) to produce RSNOs. That is, DNIC‐mediated S‐nitrosation requires a Brønsted acid–Lewis base pair to produce RSNO. Transformation of DNICs into RSNOs may only occur on the one‐thiolate‐containing {Fe(NO)₂}⁹ DNICs, in contrast to protonation of the two‐thiolate‐containing DNICs [(NO)₂Fe(SR)₂]^? by Brønsted acid to yield [{(NO)₂Fe(μ‐SR)}₂]. These results might rationalize that the known protein‐Cys‐SNO sites derived from DNICs were located adjacent to acid and base motifs, and no protein‐bound SNO characterized to date has been directly derived from [protein–(cysteine)₂Fe(NO)₂] in biology.     

[Cp2Ln(m-h1:h2-OC(SR)=CPh2 )]2 的合成和表征

[Cp2Ln（μ-SR）]2 was reacted with Ph2C=C=O to yield ketene mono-insertion products [Cp2Ln（μ-η1：η2-OC（SR）=CPh2）]2 [R=Bn, Ln=Yb （1）, Er （2）, Y （3） and R--Ph, Ln=Yb （4）], indicating that the reactions of organolanthanide thiolates with ketenes are independent of the nature of the thiolate ligand and the ketene as well as the reaction condition. These reactions could provide an efficient method for the synthesis of organolanthanide complexes with the a-thiolate-substituted enolate ligand. All these complexes were characterized by elemental analysis and spectroscopic properties and the structure of complex 1 was determined through X-ray single crystal diffraction analysis.     

Copper (II)-thiolate complexes with novel tripodal- and tetrapodal-like benzimidazoles

Summary The tripodal copper(II) thiolate complexes Cu(L1)(Cl)-2H₂O and Cu(L1)(mim)(Cl) [H(L1) = N-(2-mercaptoethyl)-N,N-bis (pyrid-2-ylmethyl)amine and mim = N-methylimidazole] have been isolated. Both contain monomeric copper(II) and display two ligand field bands and axial cryogenic e.p.r. spectra, suggesting a squarebased geometry. A copper(II) thiolate complex Cu(L2)(Cl)-H₂O [H(L2) = N-(2-mercaptoethyl)-N,N,N-tris(benzimidazol-2-ylmethyl)-1,2-ethanediamine] with a CuN₅S chromophore has been also isolated. It exhibits only one ligand field band and an axial cryogenic e.p.r. spectrum, consistent with a distorted tetragonal coordination geometry. All the thiolates display intense S^– Cu^II charge transfer bands in the u.v. region, suggesting equatorial thiolate coordination. All of the complexes exhibit irreversible electrochemical behaviour.     

Reactions of 2-pyridylphenylacetonitrile and 1,2-dicyano-1,2-diphenyl-1,2-di(2-pyridyl)ethane with cobalt(II), nickel(II), copper(II) and zinc(II) chlorides and copper(II) bromide

Summary 2-Pyridylphenylacetonitrile (ppa) is oxidized by copper(II) halides in 1,2-dichloroethane to 1,2-dicyano-1,2-diphenyl-1,2-di(2-pyridyl)ethane (dcppe), yielding 41 complexes of dcppe with copper(II) dihalide, [CuX₂(dcppe)₄] (green). Nickel(II) and zinc(II) chlorides react with ppa giving complexes of a general formula [MCl₂(ppa)₂].Dcppe reacts with copper(II), zinc(II) chlorides and copper(II) bromide yielding complexes of formulae [CuCl₂(dcppe)₄] (yellow), [ZnCl₂(dcppe)₂] and [CuBr₂(dcppe)]. No reaction is observed with cobalt(II) and nickel(II) chlorides.     

Comparisons of zinc with cadmium in N2S2 coordination and as S-bonded adducts to tungsten carbonyls

The synthesis and characterization of bis-mercaptoethanediazaheptane cadmium(II) is reported and compared to the analogous zinc complex. Of significance is the dimeric form of the [Zn(N(2)S(2))](2) complex achieves penta-coordination about zinc through a bridging thiolate whereas cadmium engages two thiolate as S-bridges resulting in hexa-coordination about cadmium within a coordination polymer whose X-ray crystal structure is reported here. In the presence of W(CO)(5), this polymer breaks up, generating dimeric [Cd(N(2)S(2))](2) with two W(CO)(5) units appended to the terminal thiolates, a feat that is not observed for the zinc dimer analogue. The greater thiophilicity of cadmium over zinc is noted in several features of these complexes.     

Synthesis and characterisation of nickel(II), cobalt(II), manganese(II), copper(II), zinc(II), dioxouranium(VI) and dioxomolybdenum(VI) complexes of tridentate dibasic ONO donor Schiff bases derived from 2-benzothiazolecarbohydrazide and salicylaldehyde/2-hydroxy-1-naphthaldehyde

Summary The syntheses of several new coordination complexes of nickel(II), cobalt(II), manganese(II), copper(II), zinc(II), dioxouranium(VI) and dioxomolybdenum(VI) with new Schiff bases derived from 2-benzothiazolecarbohydrazide and salicylaldehyde or 2-hydroxy-1-naphthaldehyde are described. These complexes have been characterised by elemental analyses, electrical conductance, magnetic susceptibility, molecular weight, i.r. and electronic spectra. The Schiff bases behave as dibasic and tridentate ligands coordinating through the ONO donor system and form complexes of the types NiL · 3H₂O, MnL · 2H₂O, CoL · 2H₂O, CuL, ZnL · H₂O, UO₂L · MeOH and MoO₂L · MeOH (where LH₂ = Schiff base). The copper(II) complexes exhibit subnormal magnetic moments indicating the presence of an antiferromagnetic exchange interaction, whereas the nickel(II), cobalt(II) and manganese(II) complexes behave normally at room temperature. Zinc(II), dioxouranium(VI) and dioxomolybdenum(VI) complexes are diamagnetic; the zinc (II) complexes are tetrahedral, the copper(II) complexes are square planar, all the other complexes are octahedral. Thev(C=N),v(C-O),v(N-N) andv(C-S) shifts have been measured in order to locate the Schiff base coordination sites.     

Metal ion complexes of 2-acetylpyridine 3-(4-methyl)piperazinyl-thiosemicarbazone

Metal complexes of stoichiometries, [M(HLppz4M)X₂] and [M(Lppz4M)X], are formed from nickel(II) and copper(II) halides and 2-acetylpyridine 3-(4-methyl)piperizinylthiosemicarbazone, HLppz4M. The [M(Lppz4M)X] complexes involve tridentate N(pyridyl), N(azomethinyl) and S(thiolate) coordination with a halo ligand completing the bonding. Neutral HLppz4M coordinatesvia the two nitrogen donors. Spectral evidence indicates the presence of a thiol hydrogen in Hppz4M complexes, the first to be reported for a coordinated thiosemicarbazone.     

Synthesis, characterization, and reactivity of new copper(II) complexes of 2-methylthio-N-(2-pyridylmethyl)acetamide

Copper(II) complexes were prepared with the new N(2)S(thioether) ligand 2-methylthio-N-(2-pyridylmethyl)acetamide (2-HL(N2S)). [Cu(2-L(N2S))Cl(MeOH)], which formed in the presence of excess triethylamine, is a distorted square pyramidal complex containing the ligand with the amide nitrogen deprotonated. The structurally analogous complex, [Cu(2-HL(N2S))Cl(2)], which formed in the absence of triethylamine, contains 2-HL(N2S) in the tautomeric imidic acid form. Neutral copper(II) N(2)S(thioether)S(thiolate) species were generated by addition of alkyl or aromatic thiolates to [Cu(2-L(N2S))Cl(MeOH)] and an unusual decomposition pathway was discovered.     

Masked Thiol Sugars: Chemical Behavior and Synthetic Applications of S‐Glycopyranosyl‐N‐monoalkyl Dithiocarbamates

The chemical behavior of S‐glycopyranosyl‐N‐monoalkyl dithiocarbamates (DTCs) as masked 1‐glycosyl thiols, easily prepared by the nucleophilic displacement of 1‐halo sugars with dithiocarbamate salts of primary amines, has been studied and synthetically exploited. This behavior relies on the abstraction of the proton of the carbamate functionality that allows controlled access to thiolate sugar intermediates. The basic character of the DTC salts used as reagents leads to thiolates that evolve in situ to symmetrical diglycosyldisulfides (DGDSs) when long reaction times are allowed. Alternatively, controlled unmasking of the thiolate function can be efficiently attained by treatment with an external base of isolated anomeric glycosyl DTCs, the formation of which is prevalent when using short reaction times. In this manner, a second methodology for the preparation of symmetrical DGDSs and a chemical protocol for the S‐glycosylation of any electrophilic substrate are established. The applications of this last strategy for the preparation of thioglycosyl vinyl sulfones, thiodisaccharides, and S‐linked homo‐ and heterodivalent neoglycoconjugates are described as a proof‐of‐concept of the great potential of the sugar DTCs in any chemical scenario in which the covalent attachment of a thiol sugar is required. The evaluation of the biological functionality of some divalent sulfurated sugar systems is also described.     

Synthesis,characterization and anticancer studies of bis-(N-methyl-1-phenyldithiocarbamato) Cu(II), Zn(II), and Pt(II) complexes: single crystal X-ray structure of the copper complex

Abstract

Cu(II), Pt(II), and Zn(II) complexes of N-methyl-1-phenyldithiocarbamate were synthesized and characterized by FTIR, NMR, UV-visible spectroscopy and elemental analysis. The complexes were formulated as [Cu(L)₂], [Zn(L)₂] and [Pt(L)₂] (where L?=?N-methyl-1-phenyldithio­carbamate) in which two molecules of the ligands coordinate to the metal ions in a bidentate chelating fashion. This is confirmed by elemental analysis and the presence of strong single bands at 952, 951, and 955?cm^?1 for Cu(II), Pt(II), and Zn(II) complexes, respectively, in the FTIR spectra. The electronic spectra of Pt(II) and Cu(II) complexes are consistent with four-coordinate square planar geometry. Single crystal X-ray of [Cu(N-mpDTC)₂] confirmed square planar structural arrangement (CuS₄) in which the ligands are asymmetrically bonded to the Cu(II) ion building a centrosymmetric monomer entity. The S-Cu-S bite angle is 77.95° (3) whereas the intramolecular N–C bond length is 1.318 Å and trans S1¹-Cu-S1?=?S2¹-Cu-S2 is 180°, which are consistent with reported copper thiolates in square planar environment. In vitro antiproliferative activity of the complexes against three human cancer cell lines showed that the zinc complex has better activity compared to Cu and Pt complexes, with IC₅₀ values of 14.28, 22.74 and 20.10?μM against TK10, UACC62, and MC7 cell lines, respectively.     

Synthesis and spectral characterization of zinc(II), copper(II), nickel(II) and manganese(II) complexes derived from <Emphasis Type="Italic">bis</Emphasis>(2-hydroxy-1-naphthaldehyde) malonoyldihydrazone

The present study shows that the reaction of different salts of the same metal with sterically crowded dihydrazone bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone (CH₂LH₄) in ethanol/aqueous media gives complexes of different stereochemistry. While the reaction of zinc(II) and copper(II) sulphate with dihydrazone yields tetrahedral complexes, the zinc(II) and copper(II) chlorides give square pyramidal and distorted octahedral complexes, respectively. On the other hand, nickel(II) sulphate and chloride, both give high-spin octahedral complexes with dihydrazone, manganese sulphate gives low-spin octahedral and manganese(II) chloride gives high-spin octahedral complexes. The reaction of these complexes with KF has been investigated. All of the products have been characterized by analytical, magnetic moment and molar conductivity data. The structures of the complexes have been established by spectroscopic studies.     

Synthesis,characterization and in vitro biological activity of cobalt(II), copper(II) and zinc(II) Schiff base complexes derived from salicylaldehyde and D,L‐selenomethionine

New cobalt(II), copper(II) and zinc(II) complexes of Schiff base derived from D,L ‐selenomethionine and salicylaldehyde were synthesized and characterized by elemental analysis, IR, electronic spectra, conductance measurements, magnetic measurements and biological activity. The analytical data showed that the Schiff base ligand acts as tridentate towards divalent metal ions (cobalt, copper, zinc) via the azomethine‐N, carboxylate oxygen and phenolato oxygen by a stoichiometric reaction of M:L (1:1) to form metal complexes [ML(H₂O)], where L is the Schiff base ligand derived from D,L ‐selenomethionine and salicylaldehyde and M = Co(II), Cu(II) and Zn(II). ¹H NMR spectral data of the ligand and Zn(II) complex agree with proposed structures. The conductivity values between 12.87 and 15.63 S cm² mol^?1 in DMF imply the presence of non‐electrolyte species. Antibacterial and antifungal results indicate that the metal complexes are more active than the ligand. Copyright © 2010 John Wiley & Sons, Ltd.     

Charge-transfer spectra of structurally characterized mixed-valence thiolate-bridged Cu(I)/Cu(II) cluster complexes

A series of Cu(II) and Cu(I)/Cu(II) complexes containing the cis-N(amine)(2)S(thiolate)(2) copper complex rac-2 has been synthesized to provide a basis for understanding the charge-transfer spectra of mixed-valence thiolate-bridged Cu(I)/Cu(II) complexes. In combination with Cu(Me(2)-13-N(4)ane), rac-2 yields a monobridged dinuclear homovalent adduct, rac-5, while reaction with CuCl yields the mixed-valance pentanuclear complex rac-6. In the presence of Cu(II)(acac)(2), chiral R,R-1 reacts to form a mixed-valence pentanuclear cation R,R-7. rac-6 exhibits a relatively short Cu(I). Cu(II) contact [2.8231(9) A] and associated structural features that suggest the presence of a weak Cu(I).Cu(II) interaction in a valence-trapped system. Additional structural features in rac-6 and R,R-7 include singly and doubly bridging thiolates, three- and four-coordinated Cu(I) ions, and varying Cu(I) ligand sets. These features extend the types and complexities of electronic absorptions significantly. Spectra of rac-6 and R,R-7 exhibit multiple overlapping absorptions over the entire visible and ultraviolet spectral regions studied, consonant with these observations. Trends resulting from variations in structure type and oxidation state permit a first approach toward developing a detailed assignment of the individual ligand Rydberg, LF, LMCT, MLCT, and possible MMCT absorptions in these complexes.     

Synthesis and Characterization of Copper(II) and Zinc(II) Tricyanomethanide (tcm) Complexes with Di(2‐pyridyl)amine (dpyam) as Co‐ligands: [Cu(dpyam)(tcm)2], [Cu(dpyam)(tcm)(OAc)] and Zn(dpyam)2(tcm)2

Three new transition metal tricyanomethanide complexes [Cu(dpyam)(tcm)₂] ( 1 ), [Cu(dpyam)(tcm)(OAc)] ( 2 ) and Zn(dpyam)₂(tcm)₂ ( 3 ) were synthesized and characterized by single crystal X‐ray diffraction analysis. In 1 each copper(II) atom is coordinated to three tcm anions and one dpyam molecule to form a square pyramide geometry. In 2 the coordination geometry around the central metal is also square pyramidal, and each copper atom is surrounded by two tcm anions, one dpyam ligand and one OAc. Both 1 and 2 display a µ_1,5‐tcm bridged infinite chain structure. In 3 each zinc(II) atom is coordinated by two tcm anions and two dpyam molecules to form a distorted octahedral geometry. Different from the former two complexes, 3 shows a mononuclear structure. Magnetic susceptibility measurement in the range 2–300 K indicates that there are weak antiferromagnetic couplings between adjacent copper(II) ions in 1 (J=?0.03 cm^?1) and 2 (J=?0.11 cm^?1) respectively.