Synthesis and spectroscopic characterization of cobalt(II) thiosemicarbazone complexes

Thiosemicarbazone derivatives are formed on reaction between acetophenone, salicylaldehyde, benzophenone and/or 2-hydroxy-4-methoxybenzophenone and thiosemicarbazide or its N⁴H substituents (ethyl-, phenyl-, and p-chlorophenyl-). The ligands were investigated by elemental analysis and spectral (IR, ¹H?NMR and MS) studies. The formulas of the prepared complexes have been suggested by elemental analyses and confirmed by mass spectra. The coordination sites of each ligand were elucidated using IR spectra revealing bidentate and tridentate coordination. Different geometries for the complexes were proposed on the basis of electronic spectra and magnetic measurements. The complexes have been analyzed thermally (TG and DTG) and the kinetic parameters for some of their degradation steps were calculated.     

Co(III) and Fe(III) complexes of Schiff bases derived from 2,4-dihydroxybenzaldehyde S-allyl-isothiosemicarbazonehydrobromide

Two new complexes, [Co(L¹)(Py)₃]Cl_0.75Br_0.25 (L¹=4-hydroxy salicylaldehyde S-allyl-isothiosemicarbazonato-N,N′,O) and [Fe(L²)Cl]·C₂H₅OH (L²=S-allyl-N¹-(4-hydroxy salicylaldehyde)-N⁴-(salicylaldehyde)isothiosemicarbazide-N,N′,O,O′), have been synthesized and characterized by elemental analysis, FT-IR and UV–vis spectroscopy, and molar conductivity. The solid-state structures of the complexes were also determined by single crystal X-ray diffraction. The iron(III) and cobalt(III) complexes adopt distorted square-pyramidal and octahedral geometries, respectively. The strength of the bonding in these complexes was investigated by thermogravimetric studies with both exhibiting stability with complete decomposition not occurring until ca. 600?°C.     

Synthesis,structure and antiproliferative activity of organometallic iridium(III) complexes containing thiosemicarbazone ligands

A series of half‐sandwich iridium complexes ( 1 – 4 ) with thiosemicarbazone ligands in two types of coordination modes were synthesized and characterized. The molecular structures of compounds 1 , 2 and 3 were determined using single‐crystal X‐ray diffraction analysis. The nature of the complexes was studied using density functional theory calculations. The stability of the complexes was investigated using UV–visible absorption spectroscopy. The compounds were further evaluated for their in vitro antiproliferative activities against HeLa, HepG2, CNE‐2, SGC‐7901, KB and HEK‐293 T cell lines. Compound 2 displays the highest antiproliferative activity among the other analogues and cisplatin.     

Synthesis,structural characterization and catalytic activities of dicopper(II) complexes derived from tridentate pyrazole‐based N2O ligands

A group of a diverse family of dinuclear copper(II) complexes derived from pyrazole‐containing tridentate N₂O ligands, 1,3‐bis(3,5‐dimethylpyrazol‐1‐yl)propan‐2‐ol (Hdmpzpo), 1,3‐bis(3‐phenyl‐5‐methyl pyrazol‐1‐yl)propan‐2‐ol (Hpmpzpo) and 1,3‐bis(3‐cumyl‐5‐methylpyrazol‐1‐yl)propan‐2‐ol (Hcmpzpo), were synthesized and characterized by elemental analysis, IR spectroscopy and three of them also by single‐crystal X‐ray diffraction. Three complexes, [Cu₂(pmpzpo)₂](NO₃)₂·2CH₃OH ( 3 ·2CH₃OH), [Cu₂(pmpzpo)₂](ClO₄)₂ ( 4 ) and [Cu₂(cmpzpo)₂](ClO₄)₂·2DMF ( 7 ·2DMF), each exhibits a dimeric structure with a inversion center being located between the two copper atoms. The metal ion is coordinated in a distorted square planar environment by two pyrazole nitrogen atoms and two bridging alkoxo oxygen atoms. Both complexes 1 ·CH₃OH·H₂O and 3 ·2CH₃OH were investigated in anaerobic conditions for the catalytic oxidation of 3,5‐di‐tert‐butylcatechol (3,5‐DTBC) to the corresponding quinone (3,5‐DTBQ), for modeling the functional properties of catechol oxidase. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and structural characterization of new multiferrocenyl diyne ligands and their cobalt carbonyl complexes

New multiferrocenyl diyne ligands FcC(CH₃)₂Fc′–C≡C–C≡C–Fc [L ₁ ; Fc?=?C₅H₅FeC₅H₄; Fc′?=?C₅H₅Fe(1,3-disubstituted)C₅H₃], FcC(CH₃)₂Fc′–C≡C–C≡C–Fc′C(CH₃)₂Fc (L ₂ ) and their complexes [FcC(CH₃)₂Fc′–C≡C–C≡C–Fc][Co₂(CO)₆] _n [n?=?1, (1); n?=?2, (2)], [FcC(CH₃)₂Fc′–C≡C–C≡C–Fc′C(CH₃)₂Fc][Co₂(CO)₆] _n [n?=?1, (3); n?=?2, (4)] have been synthesized by the coupling reaction of terminal ferrocenylacetylene and the reaction of ligands L₁ and L₂ with Co₂(CO)₈. The composition and molecular structure of the ligands L₁ , L₂ and their cobalt complexes were characterized by element analysis, IR, ¹H(¹³C)NMR and MS. The electrochemical properties of compounds L₁ , L₂ , 1, 2, 3, 4 were studied by cyclic voltammetry(CV). The results of the electrochemical research reveal that all three ferrocenyl groups in L₁ become redox active centers, but there are only two (not four) ferrocenyl redox active centers in L₂ .     

Synthesis,spectral, thermal and electrochemical characterization of metal(II) complexes with 1-S-methylcarbodithioate-4-substituted thiosemicarbazides

1-S-Methylcarbodithioate-4-substituted thiosemicarbazides (L¹-L³) have been prepared and confirmed by spectral data and elemental analysis. Co(II), Ni(II), Cu(II), Cd(II) and Zn(II) complexes with L¹-L³ have been prepared and characterized by elemental and thermal analyses, molar conductance, magnetic moment, as well as spectral data (IR, ¹H NMR, mass and electronic spectra). The molar conductance data reveal that the chelates are non-electrolytes. The IR and ¹H NMR spectra showed that L¹-L³ are deprotonated in the complexes and act as binegative SNNS donors. The electronic spectra of the complexes as well as their magnetic moments provide information about geometries. Thermogravimetric analysis of some complexes suggests different decomposition steps and ending with metal sulfide as final product. The redox properties of the complexes are explored by cyclic voltammetry.     

Synthesis and characterization of uranium (IV) complexes with various amino acids

Complexes of uranium in its IV oxidation state, using cysteine, glycine, serine and aspartic acid as ligands, have been synthesized. Semi-microanalysis of the complexes indicate 1:1 metal to ligand ratio for all the synthesized complexes. Infrared spectra of solid complexes have been employed to establish the groups, coordinated to the metal ion. Effective magnetic moment of the complexes were also estimated.     

Spectral,magnetic, thermal and electrochemical studies on new copper(II) thiosemicarbazone complexes

The chelation behavior of some =N(1) and NH(4) thiosemicarbazones towards copper(II) ions has been investigated. The isolated complexes are characterized by elemental analysis, magnetic moment, electronic, IR, ESR and ms spectra, and by thermal and voltammetric measurements. The substituents on =N(1) and/or NH(4) thiosemicarbazones and the log K values of the ligands play an important role in complex formation. The IR spectra showed that the reagents HAT, HAET, HAPT, HApClPT, H₂ST and HBT are deprotonated in the complexes and act as mononegative SN donors; H₂SET, H₂SpClPT, H₂HyMBPT and H₂HyMBpClPT, as binegative NSO donors while H₂SPT is a mononegative NSO donor. The ESR spectra of the complexes are quite similar and exhibit axially symmetric g-tensor parameters with g _‖?>?g _⊥?>?2.0023. The loss of thiol and/or hydroxyl hydrogen was confirmed from potentiometric titrations of the ligands and their copper(II) complexes. The protonation constants of the ligands as well as the stability constants of their Cu(II) complexes were calculated. Thermogravimetric analysis of the complexes suggests different decomposition steps. The Coats–Redfern and Horowitz–Metzger equations have been used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. The redox properties, nature of the electroactive species and the stability of the complexes towards oxidation are strongly dependent on the substituents on the precursor NH(4) thiosemicarbazone. The redox data are discussed in terms of the kinetic parameters and the reaction mechanism.     

Organotin(IV) complexes derived from N-ethyl-N-phenyldithiocarbamate: Synthesis,characterization and thermal studies

Organotin(IV) dithiocarbamate complexes, RSnClL₂ and R₂SnL₂ (R = Me, Bu, Ph, and L = N-ethyl-N-phenyldithiocarbamate), have been synthesized by the reaction of mono- and disubstituted organotin(IV) with ammonium dithiocarbamate. The complexes were characterized by elemental analyses, and spectroscopic techniques (¹H, ¹³C NMR and FTIR). The structures of Me₂SnL₂ and Bu₂SnL₂ were further established by single crystal X-ray diffraction technique. The crystal structure analysis showed that both complexes (Me₂SnL₂ and Bu₂SnL₂) exist as monomers. One of the dithiocarbamate ligands formed a chelate, while the other dithiocarbamate bonded to the central tin atom through one of the sulfur atoms and the second sulfur atom existed as a pendant to form distorted trigonal bipyramidal geometry. The thermal stability of all the complexes was studied using simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC). The TG-DSC results showed that Me₂SnL₂, BuSnClL₂, Bu₂SnL₂, and PhSnClL₂ displayed similar decomposition pathway via isothiocyanate intermediate, while MeSnClL₂ and Ph₂SnL₂ showed decomposition pathways different from the rest of the complexes. All the complexes resulted in SnS as the final product of the thermal decomposition process.     

Synthesis, characterization, reactivity and computational studies of new rhenium(I) complexes with thiosemicarbazone ligands derived from 4-(methylthio)benzaldehyde

N-thioamide thiosemicarbazone derived from 4-(methylthio)benzaldehyde (R = H, HL¹; R = Me, HL² and R = Ph, HL³) have been prepared and their reaction with fac-[ReX(CO)₃(CH₃CN)₂] (X = Br, Cl) in methanol gave the adducts [ReX(CO)₃(HLⁿ)] (1a X = Cl, n = 1; 1a′ X = Br, n = 1; 1b X = Cl, n = 2; 1b′ X = Br, n = 2; 1c X = Cl, n = 3; 1c′ X = Br, n = 3) in good yield.All the compounds have been characterized by elemental analysis, mass spectrometry (ESI), IR and ¹H NMR spectroscopic methods. Moreover, the structures of HL², HL³, HL³·(CH₃)₂SO and 1b′·H₂O were also elucidated by X-ray diffraction. In 1b′, the rhenium atom is coordinated by the sulphur and the azomethine nitrogen atoms (κS,N³) forming a five-membered chelate ring, as well as three carbonyl and bromide ligands. The resulting coordination polyhedron can be described as a distorted octahedron.The structure of the dimers is based on rhenium(I) thiosemicarbazonates [Re₂(L¹)₂(CO)₆] (2a), [Re₂(L²)₂(CO)₆] (2b) and [Re₂(L³)₂(CO)₆] (2c) as determined by X-ray studies. Methods of synthesis were optimized to obtain amounts of these thiosemicarbazonate complexes. In these compounds the dimer structures are achieved by Re-S-Re bridges, where S is the thiolate sulphur from a κS,N³-bidentate thiosemicarbazonate ligand.Some single crystals isolated in the synthesis of 2b contain [Re(L⁴)(L²)(CO)₃] (3b) where L⁴ (=2-methylamine-5-(para-methylsulfanephenyl)-1,3,4-thiadiazole) is originated in a cyclization process of the thiosemicarbazone. Furthermore, the rhenium atom is coordinate by the sulphur and the thioamidic nitrogen of the thiosemicarbazonate (κS,N²) affording a four-membered chelate ring.     

Synthesis,crystal structure,spectroscopy, and electrochemistry of a uranium complex

A uranium coordination compound with pyridine-2,6-dicarboxylic acid in deionized water has been synthesized and characterized by IR, UV, XPS, and X-ray single-crystal diffraction. The crystal belongs to the monoclinic system, space group C2/c with a?=?1.8427(4)?nm, b?=?0.6886(16)?nm, c?=?1.5442(4)?nm, α?=?90°, β?=?94.082(2)°, γ?=?90°, Z?=?4, and V?=?1.9544(8)?nm³. The structure shows an eight-coordinate uranium forming a hexagonal bi-pyramidal 3-D geometry with pyridine-2,6-dicarboxylate as building units. Fluorescent studies show several strong emissions. Cyclic voltammetric measurement of the compound reveals that uranium(VI) is reduced irreversibly at E _1/2?=?927?mV with ΔE _p?=?77?mV, E _1/2?=??289?mV with ΔE _p?=?113?mV. The electron transfer number (n) involved in reduction processes could be calculated to be approximately two and one, which corresponded to the unusual U(VI)/U(IV) and U(IV)/U(III) couples.     

Synthesis,characterization and magnetostructural correlation studies on three binuclear copper complexes of pyrimidine derived Schiff base ligands

Three binuclear Cu(II) complexes of two pyrimidine derived Schiff base ligands, 2-S-methyl-6-methyl-4-formyl pyrimidine-N(4)-ethyl thiosemicarbazone (HL₁) and salicyl hydrazone of 2-hydrazino-4,6-dimethylpyrimidine (HL₂), have been prepared. HL₁ produces a bis(μ-thiolato) Cu(II) complex co-crystallizing with its mononuclear analog, [Cu₂(L₁)₂(NO₃)₂][Cu(L₁)(NO₃)] (1). On the other hand HL₂ shows versatility by producing two different classes of binuclear Cu(II) complexes, a bis(μ-phenoxo) complex [Cu₂(L₂)₂(NO₃)₂] (2) and another a (μ-4,4′-bipyridyl) complex, [Cu₂(L₂)₂(μ-4,4′-bipyridyl)(NO₃)₂] (3) under suitable conditions. All the three complexes show distorted square pyramidal geometry around each Cu atom but to a varied extent. Magnetic behavior of complex 1 shows that it is strongly ferromagnetic in nature whereas compounds 2 and 3 are weakly antiferromagnetic in nature. A magnetostructural correlation study combined with molecular modelling on complexes 1 and 2 has thrown light on the difference on magnetic interaction between the Cu atoms in these two complexes. Various factors that may be responsible for such differences are also explored. A novel and potentially useful pH dependant conversion of 3 to 2 has also been noticed.     

三联苯基配体稳定的锇-锗配合物合成及表征

研究了锇-锗单键双金属配合物[OsGe(ArTrip)(PPh₃)(H) Cl₂] (1)的反应性, 其中 ArTrip=C₆H₃-2-(η⁶-Trip)-6-Trip, Trip=2, 4,6-ⁱPr₃-C₆H₃。通过与不同试剂反应, 成功合成并表征了 3个新型锇-锗双金属配合物。通过配合物 1与 EtMgBr反应合成了锗原子上氯原子被溴原子取代的产物[OsGe(ArTrip)(PPh₃)(H)Br₂] (2); 1 与 LiHBEt₃反应合成了锗原子上氯原子被乙基取代的产物[OsGe(ArTrip)(PPh₃)(H) Et₂] (3); 1 与 HBF₄ 作用合成了加成产物[OsGe(ArTrip)(PPh₃)(H)₂Cl₂]BF₄ (4)。配合物 4 不稳定, 在 H₂O(n_H2O/n₄=1)作用下能转化为配合物 1。     

三联苯基配体稳定的锇-锗配合物合成及表征

研究了锇-锗单键双金属配合物[OsGe(ArTrip)(PPh₃)(H)Cl₂] (1)的反应性,其中ArTrip=C₆H₃-2-(η⁶-Trip)-6-Trip,Trip=2,4, 6-ⁱPr₃-C₆H₃。通过与不同试剂反应,成功合成并表征了3个新型锇-锗双金属配合物。通过配合物1与EtMgBr反应合成了锗原子上氯原子被溴原子取代的产物[OsGe(ArTrip)(PPh₃)(H)Br₂] (2);1与LiHBEt₃反应合成了锗原子上氯原子被乙基取代的产物[OsGe(ArTrip)(PPh₃)(H)Et₂] (3);1与HBF₄作用合成了加成产物[OsGe(ArTrip)(PPh₃)(H)₂Cl₂]BF₄ (4)。配合物4不稳定,在H₂O (n_H2O/n₄=1)作用下能转化为配合物1。     

Bent and linear trinuclear nickel complexes with ligands derived from N -acylsalicylhydrazide ligands: structural characterization and bioactivity

Two trinuclear Ni(II) complexes Ni₃(L₁)₂(py)₂(DMF)(H₂O) (1) and Ni₃(L₂)₂(py)₂(DMF)₂ (2) with two new trianionic pentadentate ligands N-(3,5-dimethylbenzoyl)-salicylhydrazide (H₃L₁) and N-(phenylacetyl)-5-nitrosalicylhydrazide (H₃L₂) have been synthesized and characterized by X-ray crystallography. Nickel ions in the two complexes have square-planar/octahedral/square-planar coordination. Central metal ion and two terminal metal ions in the two complexes are combined by two bridging deprotonated ligands, forming a trinuclear structural unit with an M–N–N–M–N–N–M core. Studies on the trinuclear Ni(II) complexes show that the β-branched N-acylsalicylhydrazide ligands with sterically flexible Cα methylene groups yield linear trinuclear Ni(II) complexes, while α-branched N-acylsalicylhydrazide ligands tend to form bent trinuclear Ni(II) complexes. Antibacterial screening data in a previous study indicates that bent trinuclear Ni(II) compound 1 is more active than linear compound 2 and less active than a tetranuclear nickel compound.     

Synthesis and thermal behavior of dimethyl scandium complexes featuring anilido-phosphinimine ancillary ligands

A family of N,N donor ligands [1-(NHAr)-2-(PR₂NAr′)C₆H₄] (1a-d; Ar = 2,6-ⁱPr₂-C₆H₃, R = Me, Ph, Ar′ = 2,4,6-Me₃-C₆H₂, 2-ⁱPr-C₆H₄, 2,6-ⁱPr₂-C₆H₃) has been prepared and fully characterized by multinuclear NMR spectroscopy and X-ray crystallography. Lithiation of the N-H unit and subsequent salt metathesis protocols with ScCl₃THF₃ provides an avenue to organometallic scandium complexes. The resultant base-free monomeric dichlorides LScCl₂, 3a-d, have been fully characterized by NMR spectroscopy as well as X-ray crystallography (3a,c,d). Alkylation of the dichlorides using LiMe results in clean formation of dialkyl complexes LScMe₂4a-c. Thermolysis of these materials under argon and hydrogen leads to decomposition products as a result of C-H activation of the ligand. Analysis of these results provides a qualitative assessment of the metalative resistance of each ligand framework.     

Synthesis,structural studies and antimicrobial evaluation of nickel (II) complexes of NNS tridentate thiosemicarbazone based ligands

Synthesis and characterization of three nickel complexes [NiCl(L¹)] 1 , [NiCl(L²)] 2 and [NiCl(L³)] 3 are described {HL¹ = 4‐(2,5‐dimethoxyphenyl)‐1‐((pyridin‐2‐yl)methylene)thiosemicarbazide, HL² = 4‐(3‐nitrophenyl)‐1‐((pyridin‐2‐yl)methylene)thiosemicarbazide and HL³ = 4‐(2,4‐dimethoxyphenyl)‐1‐((pyridin‐2‐yl)methylene)thiosemicarbazide} and among the tridentate ligands HL³ is reported for the first time. The structures of the complexes were assigned based on CHNS microanalysis, spectroscopic (IR & UV–Vis.) data and solution conductivity studies. The absence of any magnetism for the complexes proved their square planar geometry. Single crystals of complex 1 were grown and analyzed by XRD analysis which confirmed the complex planarity as each Ni atom connects to three (two nitrogen and one sulfur) atoms from the thiosemicarbazone ligand and an additional chlorine atom. Packing of the complex 1 in the crystal lattice was proved to stabilize via intermolecular hydrogen bonds. Antimicrobial activities of 1 – 3 were studied in vitro against fungal and bacterial species and, in several instances, the complexes possessed improved antibacterial behavior in comparison to chloramphenicol.     

Synthesis,structural characterization,and thermal properties of alkaline (earth) compounds derived from 2,4-dinitroimidazole

Eight alkaline and alkaline-earth compounds derived from 2,4-dinitroimidazole (2,4-HDNI) were synthesized and characterized by elemental analysis, FT-IR, and TG–DSC, of which K(2,4-DNI) (1), Rb(2,4-DNI)(2,4-HDNI)(H₂O)₂ (2), and Ba(2,4-DNI)₂(H₂O)₄ (3) were characterized by single-crystal X-ray diffraction analysis. All the three compounds were crystallized from water, but 1 was an anhydrate. The coordination number in 1 and 3 is 10, but in 2 is 9. The 2,4-DNI adopts either η³, η², or η¹ coordination modes depending on the metal cation. In 3, there is an inversion center located on the metal. Only in 2 does water play an important role for the construction of the structure; in 3 it is a hydrogen bonding participant. TG–DSC analyses of 1 were also performed, and non-isothermal decomposition reaction kinetics were obtained.