Functional model for catecholase-like activity: Synthesis, structure, spectra, and catalytic activity of iron(III) complexes with substituted-salicylaldimine ligands

Four new mononuclear iron(III) complexes with the substituted-salicylaldimine ligands, [Fe(L¹)(TCC)] (1), [Fe(L²)(TBC)] (2), [Fe(L³)(TBC)] (3) and [Fe(L⁴)(TCC)](CH₃CN) (4) (HL¹ = N′-(5-OH-salicylaldimine)-diethylenetriamine, HL² = (N′-(5-Cl-salicylaldimine)-diethylenetriamine, HL³ N′-(5-Br-salicyl-aldimine)-dipropylenetriamine, HL⁴ = (N′-3,5-Br-salicylaldimine)-dipropylenetriamine, H₂TCC = tetrachlorocatechol, and H₂TBC = tetrabromocatechol), were prepared and characterized by XRD, EPR, and Mössbauer spectroscopy. The coordination sphere of the Fe(III) in complexes 1-4 is a distorted octahedral with N₃O₃ donors set which constructed by the Schiff-base ligands and the catecholate substrates of TBC or TCC. The in situ prepared Fe(III) complexes [Fe(L¹)Cl₂], [Fe(L²)Cl₂], [Fe(L³)(Cl₂)], and [Fe(L⁴)Cl₂] in absence of TBC or TCC show a high catecholase-like activity for the oxidation of 3,5-DTBC to the corresponding quinone 3,5-DTBQ.     

Platinum group metal complexes of bis(2-(diphenylphosphino)ethyl benzylamine and bis(2-(diphenylarsino)ethyl)benzylamine

Rh(I), Ir(I), Pd(II) and Pt(II) metal complexes of bis(2-diphenylphosphino)ethyl)benzylamine(DPBA) and bis(2-diphenylarsino)ethyl)benzylamine (DABA) have been synthesized using various starting materials. Reaction of RhCl(CO)(AsPh₃)₂ with DPBA or DABA in methanol resulted in the formation of cationic complexes of the composition, [Rh(CO)(L)]Cl (L = DPBA or DABA). Interaction of [IrCl(COD)]₂ with DPBA in benzene resulted in the formation of a neutral complex [IrCl(DPBA)]. Reaction of [PdCl₂(COD)] with the ligand DPBA in benzene resulted in a cationic complex of the composition [PdCl(DPBA)]Cl. Interaction of [PdCl(DPBA)]BPh₄ with SnCl₂ gave the complex [Pd(SnCl₃)(DPBA)]BPh₄. The ligands DPBA and DABA react with PtCl₂(COD) in acetone to give neutral, Pt(II) complexes of the type, [PtCl₂L] (L = DPBA or DABA). All the complexes were fully characterized by elemental analysis, conductivity measurements, IR and far-IR and ³¹P{¹H} NMR spectral data.     

Synthesis,DNA Binding,and Oxidative Cleavage Studies of Fe(II) and Co(III) Complexes Containing Bioactive Ligands

The two complexes containing bioactive ligands of the type and [Fe(L)] (PF₆)₂ (1) (where L = [1-{[2-{[2-hydroxynaphthalen-1-yl)methylidine]amino}phenyl)imino] methyl}naphthalene-2-ol]) and [Co(L₁L₂)] (PF₆)₃ (2) (where L₁L₂ = mixed ligand of 2-seleno-4-methylquinoline and 1,10-phenanthroline in the ratio 1:2, respectively) were synthesized and structurally characterized. The DNA binding property of the complexes with calf thymus DNA has been investigated using absorption spectra, viscosity measurements, and thermal denaturation experiments. Intrinsic binding constant K_b has been estimated at room temperature. The absorption spectral studies indicate that the complexes intercalate between the base pairs of the CT-DNA tightly with intrinsic DNA binding constant of 2.8 × 10⁵ M^?1 for (1) and 4.8 × 10⁵ M^?1 for (2) in 5 mM Tris-HCl/50 mM NaCl buffer at pH 7.2, respectively. The oxidative cleavage activity of (1) and (2) were studied by using gel electrophoresis and the results show that complexes have potent nuclease activity.     

Complexes of 2-acetyl-gamma-butyrolactone and 2-furancarbaldehyde thiosemicarbazones: antibacterial and antifungal activity

Cobalt, nickel, copper and zinc coordination compounds of two thiosemicarbazones with general composition ML₂ (L: monodeprotonated ligand corresponding to 2-acetyl-γ-butyrolactone thiosemicarbazone, HL¹, and 2-furancarbaldehyde thiosemicarbazone, HL²) and also complexes with general composition MCl₂(HL²) were synthesized (except [NiCl₂(HL²)] and [Co(L²)₂]). The interaction of CuCl₂ with HL² gave [CuCl(HL²)], a copper(I) complex. The ligands and metal complexes were characterized by IR, ¹H and ¹³C NMR spectroscopy, and magnetic susceptibility measurements. The crystal structure of [Ni(L²)₂] · 2dmso was determined and a trans-square planar coordination of the two κ²-N,S chelate rings forming polymeric strips through H-bonds with dmso was observed. Actually, in all the reported complexes both ligands behaved as κ²-N,S chelates, except in the case of [Co(L¹)₂] in which HL¹ is tridentate κ³-N,S,O. The antimicrobial properties of all compounds were studied using a wide spectrum of bacterial and fungal strains. The copper complexes of HL² were the most active against all strains, including dermatophytes and phytopathogenic fungi. Most of the studied compounds, especially [Cu(L¹)₂], presented good activity against Haemophilus influenzae, a very harmful bacterium to humans.     

Synthesis, structure and solution chemistry of quaternary oxovanadium(V) complexes incorporating hydrazone ligands

[V^IVO(acac)₂] reacts with an equimolar amount of benzoyl hydrazone of 2-hydroxyacetophenone (H₂L¹) or 5-chloro-2-hydroxyacetophenone (H₂L²) in the presence of excess pyridine (py) in methanol to produce the quaternary [V^VO(L¹)(OCH₃)(py)] (1) and [V^VO(L²)(OCH₃)(py)] (2) complexes, respectively, while under similar condition, the benzoyl hydrazones of 2-hydroxy-5-methylacetophenone (H₂L³) and 2-hydroxy-5-methoxyacetophenone (H₂L⁴) afforded only the methoxy bridged dimeric [V^VO(L³/L⁴)(OCH₃)]₂ complexes. The X-ray structural analysis of 1 and 2 indicates that the geometry around the metal is distorted octahedral where the three equatorial positions are occupied by the phenolate-O, enolate-O and the imine-N of the fully deprotonated hydrazone ligand in its enolic form and the fourth one by a methoxide-O atom. An oxo-O and a pyridine-N atom occupy two axial positions. Quaternary complexes exhibit one quasi-reversible one-electron reduction peak near 0.25 V versus SCE in CH₂Cl₂ and they decompose appreciably to the corresponding methoxy bridged dimeric complex in CDCl₃ solution as indicated by their ¹H NMR spectra. These quaternary VO³⁺ complexes are converted to the corresponding -complexes simply on refluxing them in acetone and to the -complexes on reaction with KOH in methanol. An equimolar amount of 8-hydroxyquinoline (Hhq) converts these quaternary complexes to the ternary [V^VO(L)(hq)] complexes in CHCl₃.     

Synthesis and characterization of bis(4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionato) strontium and barium adducts with O- and N- ancillary ligands; crystal structure of Sr(tftb)2(batcp)

Complexes of type [M(tftb)₂L_n] [M=Sr; n=1, L=tetraglyme (4), 2,3-benzo-10-aza-1,4,7,13-tetraoxacyclopentadeca-2-ene (batcp) (5), n=2, L=2,2^′-bipyridine-N,N^′ (bipy) (6); M=Ba; n=1, L=tetraglyme (7), 2,3-benzo-10-aza-1,4,7,13-tetraoxacyclopentadeca-2-ene (batcp) (8); n=2, L=2,2^′-bipyridine-N,N^′ (bipy) (9)] were prepared by in situ reactions of 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (Htftb) (1) with M(OH)₂ [M=Sr (2a); Ba (2b)] in the presence of the ancillary ligands L (3a: L=tetraglyme; 3b: L=2,3-benzo-10-aza-1,4,7,13-tetraoxacyclopentadeca-2-ene (batcp); 3c: L=2,2^′-bipyridine-N,N^′ (bipy)) in aqueous ethanol. The compounds were obtained in high yields and characterized by elemental analysis, ¹H NMR, mass spectrometry and IR analysis. Molecular structure of the [Sr(tftb)₂(batcp)] (5) has been determined by X-ray single crystal analysis.     

Complexes of formamidines and ethyl formimidate

Formamidines and formimidates (L = (p-MeC₆H₄ NH)(p-MeC₆H₄N=)CH; L′ = (p-MeC₆H₄N=) (EtO)CH are shown to yield metal complexes, not obtained directly before. The following complexes were characterized through spectral and magnetic data: L₂Ag⁺, L₂AgNO₃, L₂ZnBr₂, L₂CdBr₂, L₃Cd₂Br₄, LHgCl₂, L₂CoCl₂, [LH]₂[CoCl₄], cis-(CO)₂RhClL as well as L′₂Ag⁺ and cis-(CO)₂RhClL′. I.r. and n.m.r. spectra allow to distinguish these complexes from the derivatives of the isomer carbene ligands, (RNH)₂C: and (RNH)(R′O)C:.     

Synthesis, structures, electrochemistry and properties of dioxo-molybdenum(VI) and -tungsten(VI) complexes with novel asymmetric N2OS, and partially symmetric N2S2, NOS2N-capped tripodal ligands

A new class of asymmetric N-capped (dianionic/trianionic) tripodal proligands [H_x(Lⁿ)] (x = 2, n = 1-6; x = 3, n = 7, 8) which possess pendant arms with N₂OS, N₂S₂ or NOS₂ donor groups and with different chelate ring sizes {5,5,5} or {5,6,5} has been prepared. Treatment of these ligands with [WO₂Cl₂(dme)] (dme = 1,2-dimethoxyethane) in the presence of base (triethylamine or KOH) leads to the formation of cis-dioxotungsten(VI) complexes of the types [WO₂(Lⁿ)] (n = 1-6) and K[WO₂(Lⁿ)] (n = 7, 8). Reaction of these tetradentate ligands with [MoO₂(acac)₂] (acac = acetylacetonate) gives the corresponding Mo(VI) analogues [MoO₂(Lⁿ)] (n = 1-6) and K[MoO₂(Lⁿ)] (n = 7, 8). Moreover, a new five coordinate dioxomolybdenum(VI) complex with an NS₂ tridentate ligand [MoO₂(L⁹)] has been synthesised using similar procedure. All these compounds have been spectroscopically characterised and the molecular structures of [MoO₂(Lⁿ)] (n = 2, 6) and [WO₂(L⁶)] have been established by X-ray diffraction analysis. The electrochemistry and the catalytic activity for oxidation of allylic and benzylic alcohols of these dioxo complexes have also been investigated.     

DNA-Binding and Photocleavage Properties of Ru(II) Polypyridyl Complexes with DNA and Their Toxicity Studies on Eukaryotic Microorganisms

Four Ru(II) polypyridyl complexes, [Ru(bpy)₂(7-NO₂-dppz)]²⁺, [Ru(bpy)₂(7-CH₃-dppz)]²⁺, [Ru(phen)₂(7-NO₂-dppz)]²⁺, and [Ru(phen)₂(7-CH₃-dppz)]²⁺ (bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline), (7-Nitro-dppz = 7-Nitro dipyrido[3,2-a:2′-3′-c]phenazine, 7-CH₃-dppz = 7-Methyl dipyrido[3,2-a:2′-3′-c]phenazine), have been synthesized and characterized by IR, UV, elemental analysis, ¹H NMR, ¹³C-NMR, and mass spectroscopy. The DNA-binding properties of the four complexes were investigated by spectroscopic and viscosity measurements. The results suggest that all four complexes bind to DNA via an intercalative mode. Under irradiation at 365 nm, all four complexes were found to promote the photocleavage of plasmid pBR 322 DNA. Toxicological effects of the selected complexes were performed on industrially important yeasts (eukaryotic microorganisms).     

The Cu/ligand stoichiometry effect on the coordination behavior of aroyl hydrazone with copper(II): Structure,anticancer activity and anticancer mechanism

In an effort to better understand the biological efficacy of the tridentate aroyl hydrazone Cu(II) complexes, three Cu(II) complexes of acetylpyridine benzoyl hydrazone (HL), [Cu(L)(NO₃) (H₂O)]·H₂O (C1), [Cu(L)₂] (C2) and [Cu(L)(HL)]·(NO₃)(Sas) (C3) (Sas = salicylic acid) were synthesized and characterized. X-ray crystal structures and infrared (IR) spectra of the complexes reveal that the L⁻ ligand of C1 and C2 are predominantly in the enolate resonance form, while one L⁻ ligand in C3 is represented enolate resonance form and the other HL ligand exhibits keto resonance form. All Cu(II) complexes showed significantly more anticancer activity than the ligand alone. Interestingly, the Cu complexes where the ligand/metal ratio was 1:1 (C1) rather than 2:1 (C2 and C3) had higher antitumor efficacy. Moreover, the 1:1 Cu/ligand complex, C1, promotes A549 cell apoptosis possibly through the intrinsic reactive oxygen species (ROS) mediated mitochondrial pathway, accompanied by the regulation of Bcl-2 family proteins.     

Dioxouranium(VI) complexes with 2,6-acetylpyridinebenzoylhydrazones and -semicarbazones

Benzoylhydrazones and semicarbazones derived from 2,6-diacetylpyridine react with common dioxouranium(VI) compounds such as uranyl nitrate or [NBu₄]₂[UO₂Cl₄] to form air-stable complexes. 2,6-Diacetylpyridinebis(benzoylhydrazone) (H₂L¹), 2,6-diacetylpyridinebis(N4-phenylsemicarbazone) (H₂L²) and the asymmetric proligand 2,6-diacetylpyridine(benzoylhydrazone)(N4-phenylsemicarbazone) (H₂L³) give yellow products of the composition [UO₂(L)]. The neutral compounds contain doubly deprotonated ligands and possess uranium atoms with distorted pentagonal-bipyramidal coordination spheres. The equatorial coordination spheres of the metal atoms can be extended by the addition of a monodentate ligand such as pyridine or DMSO. The uranium atoms in the resulting complexes have hexagonal-bipyramidal coordination environments with the oxo ligands in axial positions.X-ray diffraction studies on [UO₂(L¹)(DMSO)], [UO₂(L²)], [UO₂(L²)(DMSO)] and [UO₂(L³)] show relatively short U-O bonds to the benzoylic oxygen atoms between 2.273(6) and 2.368(5) Å. This suggests a preference of these donor sites of the ligands over their imino and amine functionalities (U-N bond lengths: 2.502(7)-2.671(7) Å). The addition of a sixth ligand to the equatorial coordination sphere results in a lengthening of the metal-pyridine bonds.     

DNA Interaction and Photocleavage Properties of Ru (II) Complexes [Ru(bpy)2(pibi)]2+ and [Ru(phen)2(pibi)]2+

A new asymmetry ligand pibi (pibi = 2-(pyridine-2-yl)-1-H-imidazo[4,5-f]benzo[d]imidazolone) and its ruthenium complexes with [Ru(L)₂(pibi)]²⁺ (L = bpy (2, 2′-bipyridine), phen (1, 10-phenanthroline)), have been synthesized and characterized. The binding of two complexes with calf thymus DNA has been investigated by spectroscopic and viscosity measurement. The results indicate that both complexes can bind to CT-DNA through intercalative mode. Under irradiation at 365 nm, both complexes can partly promote the photocleavage of plasmid pBR322DNA. The low singlet oxygen generation abilities of the two complexes may be the factor for the low DNA photocleavage abilities.     

Synthesis, X-ray crystal structure and NMR characterisation of mononuclear Pd(II) and Pt(II) complexes of didentate ligands with NN′-donor set

Two new 3,5-dimethylpyrazolic derived ligands that are N1-substituted by diamine chains, 1-[2-(diethylamino)ethyl]-3,5-dimethylpyrazole (L1) and 1-[2-(dioctylamino)ethyl]-3,5-dimethylpyrazole (L2) were synthesised. Reaction of the ligands, L1 and L2, with [MCl₂(CH₃CN)₂] yielded [MCl₂(L)] (M = Pd(II), Pt(II)) complexes. These complexes were characterised by elemental analyses, conductivity measurements, IR, ¹H, ¹³C{¹H} and ¹⁹⁵Pt{¹H} NMR spectroscopies. The crystal structure of [PdCl₂(L1)] was determined by single-crystal X-ray diffraction methods. The structure consists of mononuclear units. The Pd(II) atom is coordinated by a pyrazolic nitrogen, an amine nitrogen and two chlorine atoms in a cis disposition. In this structure, C-H?Cl, C-H?H-C and C-H?C-H intermolecular interactions have been identified.     

Synthesis, characterization and X-ray crystal structure of [Re(L4)(CO)3]Br · 2CH3OH (L4 = N,N-bis[(2-diphenylphosphino)ethyl]methoxyethylamine): A model compound for novel cationic Tc(I)-tricarbonyl radiotracers useful for heart imaging

This report describes synthesis and evaluation of cationic complexes, [^99mTc(CO)₃(L)]⁺ (L = N-methoxyethyl-N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]amine (L1), N-[(15-crown-5)-2-yl]-N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]amine (L2) and N-[(18-crown-6)-2-yl]-N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]amine (L3)) as potential radiotracers for heart imaging. Preliminary results from biodistribution studies in female adult BALB-c mice indicated that the cationic ^99mTc(I)-tricarbonyl complex, [^99mTc(CO)₃(L2)]⁺, has a significant localization in the heart at 60 min post-injection. To understand the coordination chemistry of these bisphosphine ligands with the ^99mTc(I)-tricarbonyl core, we prepared [Re(CO)₃(L4)]Br (L4: N,N-bis[(2-diphenylphosphino)ethyl]methoxyethylamine) as a model compound. [Re(CO)₃(L4)]Br has been characterized by elemental analysis, IR, ESI-MS, NMR (¹H, ¹³C, ¹H-¹H COSY, and ¹H-¹³C HMQC) methods, and X-ray crystallography. In solid state, [Re(CO)₃(L4)]⁺ has a distorted octahedron coordination geometry with PNP occupying one facial plane. The chelator backbone adopts a “chair” conformation with phosphine-P atoms at equatorial positions and the amine-N at the apical site. In solution, [Re(CO)₃(L4)]⁺ is able to maintain its cationic nature with no dissociation of carbonyl ligands or any of the three PNP donors.     

Transition metal nitrosyls as nitrosylation agents. IV. 51V NMR characteristics of dinitrosyl and carbonylmononitrosyl vanadium complexes

The action of [Co(X)(NO)₂]₂ (X = Cl, Br, L) on [V(H)(CO)_6?nL_n] (L = 1/ndi- and tritertiary phosphine; n = 2, 3) in thf yields [V(CO)_5?n(NO)L₂] and [V(NO)₂(thf)₄]X as the two main products. Thf is easilty replaced by other ligands L′, leading to the complexes cis-[V(NO)₂(thf)_4?nL′_n]X, where n = 1 to 4. In the case of L′= CNR (R = Cy, iPr, tBu), the species [VX(NO)₂L′₃] are formed. The presence of X in the first coordination sphere is established by the normal halogen dependence (Cl < Br < I) of ⁵¹V shielding.δ(⁵¹V) values have been obtained for the two series of complexes and compared with δ of other nitrosylvanadium species, including [VX(NO)L′₄]X. for [V(NO)₂L′₄]br, ⁵¹V shielding increases in the sequence {O} < {S} < NR₃ < NCMe < AsEt₃ < SbEt₃ < PEt₂Ph < P(OMe)₃ < CNR, reflecting a general increase of shielding as the polarizability of the ligand function increases and its electronegativity decreases. Superimposed effects arising from electronic influences (PEtPh₂) < PMe₃ < P(OMe)₃ and steric conditions (chelate-4 ring < 7 ring < 6 ring < 5 ring) are also discussed. Steric factors are especially pronounced in the [V(CO)₃(NO)Ph₂P(CH₂)_mPPh₃] series (m = 1–4). The thermo-labile parent compound, [V(CO)₅NO], has been characterized by its δ(⁵¹V) = ?1489 ppm at 245 K.     

Synthesis, structure and solution chemistry of mixed-ligand oxovanadium(IV) and oxovanadium(V) complexes incorporating tridentate ONO donor hydrazone ligands

In the title family, the ONO donor ligands are the acetylhydrazones of salicylaldehyde (H₂L¹) and 2-hydroxyacetophenone (H₂L²) (general abbreviation, H₂L). The reaction of bis(acetylacetonato)oxovanadium(IV) with a mixture of tridentate H₂L and a bidentate NN donor [e.g., 2,2′-bipyridine(bpy) or 1,10-phenanthroline(phen), hereafter B] ligands in equimolar ratio afforded the tetravalent complexes of the type [V^IVO(L)(B)]; complexes (1)-(4) whereas, if B is replaced by 8-hydroxyquinoline(Hhq) (which is a bidentate ON donor ligand), the above reaction mixture yielded the pentavalent complexes of the type [V^VO(L)(hq)]; complexes (5) and (6). Aerial oxygen is most likely the oxidant (for the oxidation of V^IV → V^V) in the synthesis of pentavalent complexes (5) and (6). [V^IVO(L)(B)] complexes are one electron paramagnetic and display axial EPR spectra, while the [V^VO(L)(hq)] complexes are diamagnetic. The X-ray structure of [V^VO(L²)(hq)] (6) indicates that H₂L² ligand is bonded with the vanadium meridionally in a tridentate dinegative fashion through its phenolic-O, enolic-O and imine-N atoms. The general bond length order is: oxo < phenolato < enolato. The V-O (enolato) bond is longer than V-O (phenolato) bond by ∼0.07 Å and is identical with V-O (carboxylate) bond. ¹H NMR spectrum of (6) in CDCl₃ solution indicates that the binding nature in the solid state is also retained in solution. Complexes (1)-(4) display two ligand-field transitions in the visible region near 820 and 480 nm in DMF solution and exhibit irreversible oxidation peak near +0.60 V versus SCE in DMSO solution, while complexes (5) and (6) exhibit only LMCT band near 535 nm and display quasi-reversible one electron reduction peak near −0.10 V versus SCE in CH₂Cl₂ solution. The VO³⁺-VO²⁺E_1/2 values shift considerably to more negative values when neutral NN donor is replaced by anionic ON donor species and it also provides better VO³⁺ binding via phenolato oxygen. For a given bidentate ligand, E_1/2 increases in the order: (L²)²⁻ < (L¹)²⁻.     

Cobalt and nickel complexes of versatile imidazole- and pyrrole-2-carbaldehyde thiosemicarbazones. Synthesis, characterisation and antimicrobial activity

Ni(II), Co(II) and Co(III) complexes of imidazole- and pyrrole-2-carbaldehyde thiosemicarbazone ligands (H₂L¹ and H₂L², respectively) have been prepared. The X-ray crystal structures of [Co(L¹)(HL¹)], [Ni(H₂L¹)₂]Cl₂ · 3.5H₂O and [Ni(HL²)₂] have been solved. The Co(III) ion assumes a slightly distorted octahedral coordination geometry, involving both N₂S binding domain of di- and monoanionic ligand molecules. Whereas in [Ni(HL²)₂] the metal ion is tetracoordinated in a square planar geometry by two pyrrole-2-carbaldehyde thiosemicarbazone molecules acting as NS-donor, the spatial array of non deprotonated H₂L¹ ligand molecules in [Ni(H₂L¹)₂]Cl₂ · 3.5H₂O is equivalent to that found for [Co(L¹)(HL¹)]. The in vitro antimicrobial properties of the ligands and their complexes were tested against representative bacterial and fungal strains in broth culture. The compounds H₂L² and [Co(L²)(HL²)(H₂L²)] · 1.5H₂O exhibit a moderate inhibitory effect on the microbial proliferation and only against some Gram positive bacteria.     

Novel dioxomolybdenum(VI) and oxomolybdenum(V) complexes with pyridoxal thiosemicarbazone ligands: Synthesis and structural characterisation

New molybdenum complexes were prepared by the reaction of [Mo^VIO₂(acac)₂] or (NH₄)₂[Mo^VOCl₅] with different N-substituted pyridoxal thiosemicarbazone ligands (H₂L¹ = pyridoxal 4-phenylthiosemicarbazone; H₂L² = pyridoxal 4-methylthiosemicarbazone, H₂L³ = pyridoxal thiosemicarbazone). The investigation of monomeric [MoO₂L¹(CH₃OH)] or polymeric [MoO₂L^1-3] molybdenum(VI) complexes revealed that molybdenum is coordinated with a tridentate doubly-deprotonated ligand. In the oxomolybdenum(V) complexes [MoOCl₂(HL^1-3)] the pyridoxal thiosemicarbazonato ligands are tridentate mono-deprotonated. Crystal and molecular structures of molybdenum(VI) [MoO₂L¹(CH₃OH)]·CH₃OH, and molybdenum(V) complexes [MoOCl₂(HL¹)]·C₂H₅OH, as well as of the pyridoxal thiosemicarbazone ligand methanol solvate H₂L³·MeOH, were determined by the single crystal X-ray diffraction method.     

Phosphane effects on formation and reactivity of [Ru(L)(PR3)(`N2Me2S2')] complexes with L=N2, N2H4, NH3, and CO

Metal-sulfur complex fragments, to which small molecules like N₂, N₂H₂, N₂H₄, NH₃, or CO can bind, are desirable model compounds concerning enzymatic N₂ fixation.This paper reports on the effects of the phosphane co-ligand on formation and reactivity of [Ru(L)(PR₃)(`N<sub>2</sub>Me<sub>2</sub>S<sub>2</sub>')] [`N₂Me₂S₂'²⁻=1,2-ethanediamine-N,N^′-dimethyl-N,N^′-bis(2-benzenethiolate)(2−)] complexes with nitrogenase relevant ligands, especially N₂, N₂H₄, NH₃, and CO.Treatment of [Ru(NCCH₃)₄Cl₂] with Li₂`N<sub>2</sub>Me<sub>2</sub>S<sub>2</sub>', excessive LiOMe, bulky PPh<sub>3</sub> or PCy<sub>3</sub>, respectively, led to the formation of two series of [Ru(L)(PR<sub>3</sub>)(`N₂Me₂S₂')] complexes [for R=Ph: 1b, 1c (L=NCCH₃), 6b (L=N₂H₄), 7b (L=N₂), 8b_1-3 (L=CO), 9b (L=NH₃); for R=Cy: 1a (L=NCCH₃), 6a (L=N₂H₄), 7a (L=N₂), 8a (L=CO), 9a (L=NH₃)]. While the use of PPh₃ (θ=145°) yielded cis,trans and cis,cis isomers of [Ru(NCCH₃)(PPh₃)(`N<sub>2</sub>Me<sub>2</sub>S<sub>2</sub>')] (1b, 1c), no isomer formation was observed with the bulkier phosphane PCy<sub>3</sub> (θ=170°). Sterically less demanding phosphanes (θ=118-132°) afforded bisphosphane complexes [Ru(PR<sub>3</sub>)<sub>2</sub>(`N₂Me₂S₂')] [2d (R=Me), 2e (R=Et), 2f (R=nPr), and 2g (R=nBu)], which were practically inert and could only be converted in two cases and under drastic reaction conditions into the CO complexes [Ru(CO)(PR₃)(`N<sub>2</sub>Me<sub>2</sub>S<sub>2</sub>')] [4e (R=Et), 4f (R=nPr)]. The chelating bidentate phosphane dppe (bisdiphenylphosphanoethane) yielded exclusively the mononuclear complex [Ru(dppe)(`N₂Me₂S₂')] (3).     

Synthesis, crystal structure and spectroscopic behaviors of Co(II) and Cu(II) complexes with Salen-type bisoxime ligands

Two Salen-type ligands (H₂L¹, 4,4′-dichloro-2,2′-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol and H₂L², 4,4′-dinitro-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol) and their corresponding complexes ({[CoL¹(MeOH)]₂(OAc)₂Co} · 2MeOH and [CuL²]₂) have been synthesized and characterized by element analyses, ¹H NMR, FT-IR and UV-Vis spectra, TG-DTA and single crystal X-ray crystallography. Crystallographic data suggests the octahedral geometry for Co(II) complex and square-pyramidal geometry for Cu(II) complex. Furthermore, the fluorescence behavior of Cu(II) complex in DMSO is discussed.