2O Complexes Research Articles

Elucidating the Electronic Structure and Magnetic and Conducting Properties of μ-Oxo Mn-phthalocyanine [MnPc(CN)]2O Complex

The μ-oxo phthalocyanine dimer complex [Mn(Pc)(CN)]2O has been characterized as the first single-component molecular conductor exhibiting magnetoresistance at room temperature. Herewith, we report a detailed study of the electronic structure and the magnetic and conducting properties of this μ-oxo MnPc dimer complex. A combined strategy of wave-function-based quantum chemistry calculations on the complex and plane-wave-based periodic calculations on the crystal has been employed together with semiclassical Boltzmann transport theory calculations. Our results provide information about the ligand field parameters of the Mn ions, clarify their spin states on the [Mn(Pc)(CN)]2O complex, and explain the temperature dependence of both the magnetic susceptibility and the effective magnetic moment, taking into account the presence of excited low-lying states with S = 2 and weak intermolecular magnetic interactions, as key ingredients of the magnetic behavior. The analysis of the density of states of the low-spin and high-spin density functional theory + U magnetic solutions and their respective temperature dependence of the electric resistivity give some clues about the conducting properties and the negative magnetoresistance reported for this system.

Molybdenum complex with bulky chelates as a functional model for molybdenum oxidases.

The novel bulky Schiff base chelate ligand [(4,5-diisopropyl-1H-pyrrole-2-yl)methylene]-4-(tert-butyl)aniline ((iPr2)HL) bearing two isopropyl groups close to the pyrrole nitrogen atom reacts with MoCl2(dme)O2 (dme = 1,2-dimethoxyethane) to give the sterically congested complex Mo(VI)((iPr2)L)2O2 ((iPr2)1; OC-6-4-4 configuration). In spite of the increased steric shielding of the [MoO2] unit (iPr2)1 is active in oxygen-atom transfer to PMe3 and PPh3 to give OPMe3 and OPPh3, respectively. Because of the increased steric bulk of the chelate ligand, formation of dinuclear complexes [Mo(V)((iPr2)L)2O]2(μ-O) ((iPr2)3) by comportionation is effectively prevented in contrast to the highly favored formation of [Mo(V)((H2)L)2O]2(μ-O) ((H2)3) with the less bulky ligand (H2)HL. Instead, the smaller PMe3 ligand coordinates to the resulting pentacoordinate intermediate Mo(IV)((iPr2)L)2O ((iPr2)5), giving the hexacoordinate complex Mo(IV)((iPr2)L)2O(PMe3) ((iPr2)2) with OC-6-3-3 configuration. The larger potential ligands PPh3 and OPPh3 are only able to weakly coordinate to (iPr2)5, giving labile and sensitive Mo(IV)((iPr2)L)2O(L) complexes ((iPr2)6, L = PPh3; (iPr2)7, L = OPPh3). Traces of water and dioxygen in solutions of (iPr2)6/(iPr2)7 yield the di(μ-oxido) complex [Mo(V)((iPr2)L)O]2(μ-O)2 ((iPr2)4) with reduced steric congestion due to dissociation of the bulky chelate ligands. According to electron paramagnetic resonance studies, the much more strongly bound small PMe3 ligand in (iPr2)2 can be slowly liberated by one-electron oxidation to Mo(V), with Ag(+) leaving a free coordination site at Mo(V). Hence, essentially pentacoordinate Mo(IV) and Mo(V) complexes are accessible as a result of the increased steric bulk.

Electronic effects of para substituents of 2-hydroxybenzaldehyde co-ligands in a family of hydrazonato-oxidovanadium(v) complexes

Eight mixed-ligand hydrazonato-oxidovanadium(V) complexes of the type [VVO(HL1)(A1–4)] (1–4) and [VVO(HL2)(A1–4)] (5–8) have been investigated, where (HL1)2− and (HL2)2− represent the dianionic forms of the 2-hydroxybenzoylhydrazone of acetylacetone (H3L1) and benzoylacetone (H3L2) respectively, and (A1–4)− represents the monoanionic forms of 2-hydroxybenzaldehyde (HA1), 2-hydroxy-5-methylbenzaldehyde (HA2), 2-hydroxy-5-methoxybenzaldehyde (HA3) and 5-bromo-2-hydroxybenzaldehyde (HA4) respectively. The complexes were synthesized by refluxing [VIVO(acac)2] and [VIVO(bzac)2], where acac− and bzac− are the monoanionic forms of acetylacetone (Hacac) and benzoylacetone (Hbzac) respectively with an equimolar amount of 2-hydroxybenzoylhydrazide in methanol followed by the addition of either an equivalent amount or a slight excess of each HA. 1H NMR spectra of complexes 1–3 and 5–7 in CDCl3 indicated the existence of two isomeric forms arising from the interchange of the coordinating positions of the bidentate A− ligand between axial and equatorial positions, a conclusion which is also supported by 51V NMR spectra. The vanadium atom in these complexes is in a six-coordinate distorted octahedral environment in which the dinegative hydrazone ligands in the enol form bind the vanadium in a tridentate meridional fashion utilizing their enolic-O, one imine-N and amide-O atoms, leaving the phenolic-O and other imine-N atoms unbonded although they do form intramolecular hydrogen bonds as is evident from IR, 1H NMR and X-ray diffraction studies. Analysis of electronic spectra and redox potential (E1/2) values of these complexes indicate that the λmax values for the LMCT transition and the E1/2 values are linearly related to the Hammett σ constants of the substituents in the monoanionic aryloxy ring of the A− co-ligand. On keeping in methanol for ∼5 days, the monomers 1–8 are converted to dimethoxide bridged dimeric [VVO(HL)(OCH3)]2 (9 and 10) complexes while oxido bridged dimeric [VVO(HL)]2O (11 and 12) complexes are obtained from dichloromethane or chloroform solution at room temperature after ∼5 days. On dissolution in CHCl3 or CH2Cl2, the [VVO(HL)(OCH3)]2 complexes converted to their respective monomeric [VVO(HL)(OCH3)] analogues and also to oxido bridged dimeric [VVO(HL)]2O species which is evident from their 1H NMR, 51V NMR and mass spectra.

Preparation and Optoelectronic Characteristics of ZnO/CuO-Cu₂O Complex Inverse Heterostructure with GaP Buffer for Solar Cell Applications.

This study reports the optoelectronic characteristics of ZnO/GaP buffer/CuO-Cu2O complex (COC) inverse heterostructure for solar cell applications. The GaP and COC layers were used as buffer and absorber in the cell structure, respectively. An energy gap widening effect and CuO whiskers were observed as the copper (Cu) layer was exerted under heat treatment for oxidation at 500 °C for 10 min, and arose from the center of the Cu2O rods. For preparation of the 30 nm-thick GaP buffer by sputtering from GaP target, as the nitrogen gas flow rate increased from 0 to 2 sccm, the transmittance edge of the spectra demonstrated a blueshift form 2.24 to 3.25 eV. Therefore, the layer can be either GaP, GaNP, or GaN by changing the flow rate of nitrogen gas.

Synthesis, Spectroscopic Characterization, Electrochemical and Antimicrobial Studies of Copper(II), Nickel(II), Cobalt(II) and Zinc(II) Complexes Derived from 1-Phenyl-2,3-dimethyl-4(2-iminomethylbenzylidene)-pyrozol-5-(α-imino)-indole-3-propionic Acid

Neutral tridentate N 2O complexes of Cu(II), Ni(II), Co(II) and Zn(II) have been synthesized using the 1-phenyl-2,3-dimethyl-4(2-iminomethylbenzylidene)-pyrozol-5-(�-imino)-indole-3-propionic acid (H 2L). All the complexes were characterized by elemental analysis, molar conductivity, magnetic susceptibility data, IR, 1 H-NMR, UV-Vis, FAB-Mass and EPR spectral studies. The physicochemical studies and spectral data indicate that the ligand acts as a divalent tridentate chelating agent. All the complexes have the general composition (ML 2) (M= Cu(II), Ni(II), Co(II) and Zn(II); L = Schiff base). The IR, UV-Vis., magnetic susceptibility measurements and EPR spectral data of the complexes suggest that all the complexes are octahedral geometry. The lower conductivity data confirm the non-electrolytic nature of the complexes. The effect of redox potential on Cu(II) and Ni(II) ions by the ligand environment is studied by cyclic voltammetric measurements. The Schiff base and its metal complexes were utilized to test the in vitro antimicrobial activities, which gave good results in the presence of metal ion than the free ligand environment against the different species of microorganisms.

Solid-state thermal decomposition of the [Co(NH 3) 5CO 3]NO 3·0.5H 2O complex: A simple, rapid and low-temperature synthetic route to Co 3O 4 nanoparticles

Co 3O 4 nanoparticles were easily prepared via the decomposition of the pentammine(carbonato)cobalt(III) nitrate precursor complex [Co(NH 3) 5CO 3]NO 3·0.5H 2O at low temperature (175 °C). The product was characterized by thermal analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV–visible spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, Brunauer–Emmett–Teller (BET) specific surface area measurements and magnetic measurements. The FT-IR, XRD, Raman and EDX results indicated that the synthesized Co 3O 4 nanoparticles are highly pure and have a single phase. The TEM analysis revealed nearly uniform and quasi-spherical Co 3O 4 nanoparticles with an average particle size of approximately 10 nm. The optical absorption spectrum of the Co 3O 4 nanoparticles showed two direct band gaps of 2.18 and 3.52 eV with a red shift in comparison with previous reported values. The prepared Co 3O 4 nanoparticles showed a weak ferromagnetic behaviour that could be attributed to uncompensated surface spins and/or finite-size effects. Using the present method, Co 3O 4 nanoparticles can be produced without expensive organic solvents and complicated equipment. This simple, rapid, safe and low-cost synthetic route can be extended to the synthesis of other transition-metal oxides.

Novel palladium(II) and platinum(II) complexes with 1H-benzimidazol-2-ylmethyl-N-(4-bromo-phenyl)-amine: Structural studies and anticancer activity

[MLCl 2] (L = (1H-benzimidazol-2-ylmethyl)-N-(4-bromo-phenyl)-amine; M = Pd & Pt) and [PdL(OH 2) 2]∙2X∙zH 2O (X = Br, I, z = 2; X = SCN, z = 1; X = NO 3, z = 0) complexes have been synthesized as potential anticancer compounds and their structures were elucidated using elemental analysis, spectral, thermal analysis and X-ray powder diffraction. The benzimidazole (L) crystallizes in the space group P2 1/c with a = 8.6660(3) Å, b = 16.6739(7) Å, c = 9.8611(4) Å and β = 113.505(3) ° and forms an infinite chain structure with a trans-zigzag type along the crystallographic axis "a", through the intermolecular H–bond. FT-IR and 1H NMR studies revealed that the ligand L is coordinated to the metal ion via the pyridine-type nitrogen (N py) of the benzimidazole ring and secondary amino group (NH sec). Quantum mechanical calculations of energies, geometries, vibrational wavenumbers, and 1H NMR of the benzimidazole L and its complexes were carried out by DFT/B3LYP method combined with 6–31G(d) and LANL2DZ basis sets. Natural bond orbital (NBO) analysis and frontier molecular orbitals (FMO) were performed at B3LYP/LANL2DZ level of theory. The benzimidazole L, in comparison to its metal complexes was screened for its antibacterial activity. The complexes showed cyctotoxic effects against human breast cancer (MCF7), hepatocarcinoma (HepG 2) and colon carcinoma cells (HCT). The platinum complex (6) exhibited a moderate antitumor activity against MCF7 with IC 50 = 10.2 μM comparing to that reported for cis-platin 9.91 μM.

Complexation of formaldoxime with water. Infrared matrix isolation and theoretical studies

The 1:1, 1:2 and 2:1 formaldoxime-water complexes isolated in the argon matrices have been studied by help of FTIR spectroscopy and MP2/6-311++G(2d,2p) method. The calculations predicted the stability of the three CH 2NOH⋯H 2O isomeric complexes, three CH 2NOH⋯(H 2O) 2 ones and one (CH 2NOH) 2⋯H 2O complex. The analysis of the experimental spectra and their comparison with theoretical ones indicated that both the 1:1 and 1:2 complexes trapped in solid argon have the most stable cyclic structures stabilized by the O–H⋯O and O–H⋯N bonds between the formaldoxime and water molecules. In the 1:2 complex formaldoxime interacts with the water dimer, one H 2O molecule acts as a proton acceptor for the OH group of formaldoxime whereas the second H 2O molecule acts as a proton donor toward the nitrogen atom of the formaldoxime molecule. In the (CH 2NOH) 2⋯H 2O complex the OH group of the water molecule acts as a proton donor toward one of the oxygen atoms of the formaldoxime cyclic dimer.

Synthesis, spectral and structural studies of 1-ethoxycarbonyl-piperazine-4-carbodithioate and its Co(III), Zn(II) and Cd(II) complexes

The new complexes [Co(ecpzdtc) 3] ( 2) [Zn(ecpzdtc) 2(py)] ( 3) and [Cd(ecpzdtc) 2(py)]·H 2O ( 4) have been synthesized from sodium 1-ethoxycarbonyl-piperazine-4-carbodithioate [(Na +(ecpzdtc) −]. The ligand and the complexes have been characterized by elemental analyses, IR, magnetic susceptibility and single crystal X-ray data. The [Zn(ecpzdtc) 2(py)] and [Cd(ecpzdtc) 2(py)]·H 2O complexes contain pyridine as the co-ligand. [Co(ecpzdtc) 3] ( 2) crystallizes in the monoclinic system, whereas [Zn(ecpzdtc) 2(py)] ( 3) and [Cd(ecpzdtc) 2(py)]·H 2O ( 4) crystallize in the triclinic system. The sulfur donor sites of the bidentate ligand chelate the metal center, forming a four-membered CS 2M ring. The cobalt complex has a distorted octahedral geometry, the zinc complex is almost between trigonal bipyramidal and square pyramidal, whereas the cadmium complex is square pyramidal. The crystal structures of all the complexes are stabilized by various types of inter and intramolecular hydrogen bonding.

Bioinspired Fe IIICd II and Fe IIIHg II complexes: Synthesis, characterization and promiscuous catalytic activity evaluation

In this work we report on the synthesis, crystal structure, and physicochemical characterization of the novel dinuclear [Fe IIICd II(L)(μ-OAc) 2]ClO 4·0.5H 2O ( 1) complex containing the unsymmetrical ligand H 2L = 2-bis[{(2-pyridyl-methyl)-aminomethyl}-6-{(2-hydroxy-benzyl)-(2-pyridyl-methyl)}-aminomethyl]-4-methylphenol. Also, with this ligand, the tetranuclear [Fe 2 IIIHg 2 II(L) 2(OH) 2](ClO 4) 2·2CH 3OH ( 2) and [Fe IIIHg II(L)(μ-CO 3)Fe IIIHg II(L)](ClO 4) 2·H 2O ( 3) complexes were synthesized and fully characterized. It is demonstrated that the precursor [Fe III 2Hg II 2(L) 2(OH) 2](ClO 4) 2·2CH 3OH ( 2) can be converted to ( 3) by the fixation of atmospheric CO 2 since the crystal structure of the tetranuclear organometallic complex [Fe IIIHg II(L)(μ-CO 3)Fe IIIHg II(L)](ClO 4) 2·H 2O ( 3) with an unprecedented {Fe III(μ-O phenoxo) 2(μ-CO 3)Fe III} core was obtained through X-ray crystallography. In the reaction 2 → 3 a nucleophilic attack of a Fe III-bound hydroxo group on the CO 2 molecule is proposed. In addition, it is also demonstrated that complex ( 3) can regenerate complex ( 2) in aqueous/MeOH/NaOH solution. Magnetochemical studies reveal that the Fe III centers in 3 are antiferromagnetically coupled ( J = − 7.2 cm − 1 ) and that the Fe III–OR–Fe III angle has no noticeable influence in the exchange coupling. Phosphatase-like activity studies in the hydrolysis of the model substrate bis(2,4-dinitrophenyl) phosphate (2,4-bdnpp) by 1 and 2 show Michaelis–Menten behavior with 1 being ~ 2.5 times more active than 2. In combination with k H/ k D isotope effects, the kinetic studies suggest a mechanism in which a terminal Fe III-bound hydroxide is the hydrolysis-initiating nucleophilic catalyst for 1 and 2. Based on the crystal structures of 1 and 3, it is assumed that the relatively long Fe III…Hg II distance could be responsible for the lower catalytic effectiveness of 2.

Fluorescence enhancement of Tb(III) complex with a new β-diketone ligand by 1,10-phenanthroline

A novel β-diketone, 1-(3,4,5-trisbenzyloxy)benzoyl-5-benzoyl acetylacetone (TBAA), and its corresponding binary Tb(III) complex Tb(TBAA) 3·2H 2O and ternary complex Tb(TBAA) 3Phen with 1,10-phenanthroline (Phen) were prepared. The ligand was characterized based on elemental analysis, FT-IR, and 1H NMR. The complexes were characterized with elemental analysis, FT-IR and thermogravimetry and derivative thermogravimetry (TG-DTG). Photoluminescence measurements indicated that the energy absorbed by the organic ligand was efficiently transferred to the central Tb 3+ ions, and the complex showed intense and characteristic emissions due to the 5D 4→ 7F J transitions of the central Tb 3+ ions. Both complexes showed longer fluorescence lifetimes. After the introduction of the second ligand Phen group, the relative emission intensities and fluorescence lifetimes of the ternary complex Tb(TBAA) 3Phen enhanced more obviously than that of the binary complex Tb(TBAA) 3·2H 2O. This indicated that the presence of the ligand TBAA and the second ligand Phen could sensitize fluorescence intensities of Tb(III) ions, and the introduction of Phen group resulted in the enhancement of the fluorescence properties of the Tb(III) ternary rare earth complex.

Structural, optical and electrical properties of europium picrate tetraethylene glycol complex as emissive material for OLED

A new europium complex [Eu(Pic) 2(H 2O)(EO4)](Pic)·0.75H 2O was synthesized and used as the emission material for the single layer device structure of ITO/EO4–Eu–Pic/Al, using a spin-coating technique. Study on the optical properties of the [Eu(Pic) 2(H 2O)(EO4)](Pic)·0.75H 2O complex where EO4=tetraethylene glycol and Pic=picrate anion, had to be undertaken before being applicable to the study of an organic light emitting diode (OLED). The electrical property of an OLED using current–voltage ( I– V) measurement was also studied. In complex, the Eu(III) ion was coordinated with the EO4 ligand as a pentadentate mode, one water molecule, and with two Pic anions as bidentate and monodentate modes, forming a nine-coordination number. The photoluminescence (PL) spectra of the crystalline complex in the solid state and its thin film showed a hypersensitive peak at 613.5–614.9 nm that assigned to the 5D 0→ 7F 2 transition. A narrow band emission from the thin film EO4–Eu–Pic was obtained. The typical semiconductor I– V curve of device ITO/EO4–Eu–Pic/Al showed the threshold and turn on voltages at 1.08 and 4.6 V, respectively. The energy transfer process from the ligand to the Eu(III) ion was discussed by investigating the excitation and PL characteristics. Effect of the picrate anion on the device performance was also studied.

Role of hydrogen peroxide in the synthesis of nitrogen heterocycle containing cobalt complexes

The reactions of Co(O 2CCH 3) 2·4H 2O with the sodium salt of p-toluene sulfonic acid (NapTS) and pyridine (py) or 4-methylpyridine (4mepy) in the presence of hydrogen peroxide in methanol led to the formation of [Co(py) 3(H 2O) 3](pTS) 2 or [Co(4mepy) 2(H 2O) 4](pTS) 2·MeOH, respectively. The coordination polymer [{Co(44′bpy)(H 2O) 4}(pTS) 2] n (4,4′-bipyridine = 44′bpy) was obtained from the reaction of Co(O 2CCH 3) 2·4H 2O with 44′bpy in the presence of NapTS. The reaction of Co(O 2CCH 3) 2·4H 2O, 2,2′-bipyridine (22′bpy) and NapTS with hydrogen peroxide resulted in the formation of the dinuclear complex [Co 2(μ-OH) 2(μ-O 2CCH 3)(O 2CCH 3) 2(22′bpy) 2](pTS). Characterization of these complexes and the role of hydrogen peroxide in these reactions are discussed. Similar reactions with sodium sulfamate gave the mononuclear [Co(22′bpy) 2(O 2CCH 3)]NH 2SO 3·2H 2O complex and [Co 2(μ-OH) 2(μ-O 2CCH 3)(O 2CCH 3) 2(22′bpy) 2](NH 2SO 3).

Structural and in vitro cytotoxicity studies on 1H-benzimidazol-2-ylmethyl-N-phenyl amine and its Pd(II) and Pt(II) complexes

[MLCl 2]· zH 2O (L = (1H-benzimidazol-2-ylmethyl)-N-phenyl amine; M = Pd, z = 0; M = Pt, z = 1) and [PdL(OH 2) 2]·2X·zH 2O (X = Br, I, NO 3, z = 0; X = SCN, z = 1) complexes were synthesized as potential anticancer compounds and characterized by elemental analysis, spectral and thermal methods. FT-IR and 1H NMR studies revealed that the benzimidazole L is coordinated to the metal ions via the pyridine-type nitrogen (N py) of the benzimidazole ring and secondary amino group (NH sec). Quantum mechanical calculations of energies, geometries, vibrational wavenumbers, and 1H NMR of the benzimidazole L and its complexes were carried out by density functional theory using B3LYP functional combined with 6-31G(d) and LANL2DZ basis sets. Natural bond orbitals (NBOs) and frontier molecular orbitals were performed at B3LYP/LANL2DZ level of theory. The synthesized ligand, in comparison to its metal complexes was screened for its antibacterial activity. The benzimidazole L is more toxic against the bacterium Staphylococcus aureus (MIC = 58 μg/mL) than the standard tetracycline (MIC = 82 μg/mL). The complexes showed cytotoxicity against breast cancer, Colon Carcinoma, and human heptacellular Carcinoma cells. The platinum complex ( 6) displays cytotoxicity (IC 50 = 12.4 μM) against breast cancer compared with that reported for cis-platin 9.91 μM.

Synthesis, characterization and X-ray diffraction of [Cu(malonate)(phen) 2] 2·17H 2O complex

Mixed ligand complex, [Cu(malonate)(phen) 2] 2 ·17H 2O (phen = 1,10-phenanthroline), was synthesized and characterized by elemental analyses, infrared spectrum, thermo-gravimetric analyses and single X-ray crystallography. In the complex, copper atom displayed a five coordinated environment. It bonded with four nitrogen atoms of 1,10-phenanthroline and one oxygen atom of malonate group in a distorted square pyramidal arrangement. The crystal structure of the complex was determined by X-ray single crystallography using X-ray diffraction technique 100(2) K with a AXS SMART APEX (Bruker) diffractometer, Mo Kα radiations ( λ = 0.71073 Å), R = 0.0642 and 0.0989. Orthorhombic unit cell parameters are: a = 13.1888(11) Å, b = 14.8458(12) Å, c = 16.7159(14) Å, V = 2975.8(4) Å, Dx = 2, 1.516 Mg/m 3 and Mr = 1358.26. Thermal decomposition of the complex was studied under inert atmosphere.

Synthesis, spectroscopic characterization and thermal behavior of metal complexes formed with N′-(1-(4-hydroxyphenyl) ethylidene)-2-oxo-2-(phenylamino) acetohydrazide (H 3OPAH)

Complexes of Co(II), Ni(II), Cu(II), Mn(II), Cd(II), Zn(II), Hg(II) and U(IV)O 2 2+ with N′-(1-(4-hydroxyphenyl) ethylidene)-2-oxo-2-(phenylamino) acetohydrazide (H 3OPAH) are reported and have been characterized by various spectroscopic techniques like IR, UV–visible, 1H NMR and ESR as well as magnetic and thermal (TG and DTA) measurements. It is found that the ligand behaves as a neutral bidentate, monoanionic tridentate or tetradentate and dianionic tetradentate. An octahedral geometry for [Mn(H 3OPAH) 2Cl 2], [Co 2(H 2OPAH) 2Cl 2(H 2O) 4] and [(UO 2) 2(HOPAH)(OAc) 2(H 2O) 2] complexes, a square planar geometry for [Cu 2(H 2OPAH)Cl 3(H 2O)]H 2O complex, a tetrahedral structure for [Cd(H 3OPAH)Cl 2], [Zn(H 3OPAH)(OAc) 2] and [Hg(H 3OPAH)Cl 2]H 2O complexes. The binuclear [Ni 2(HOPAH)Cl 2(H 2O) 2]H 2O complex contains a mixed geometry of both tetrahedral and square planar structures. The protonation constants of ligand and stepwise stability constants of its complexes at 298, 308 and 318 K as well as the thermodynamic parameters are being calculated. The bond lengths, bond angles, HOMO, LUMO and dipole moments have been calculated to confirm the geometry of the ligand and the investigated complexes. Also, thermal properties and decomposition kinetics of all compounds are investigated. The interpretation, mathematical analysis and evaluation of kinetic parameters ( E a, A, Δ H, Δ S and Δ G) of all thermal decomposition stages have been evaluated using Coats–Redfern and Horowitz–Metzger methods.

Bivalent transition metal complexes of o-hydroxyacetophenone [N-(3-hydroxy-2-naphthoyl)] hydrazone: Spectroscopic, antibacterial, antifungal activity and thermogravimetric studies

Schiff base complexes of Cu(II), Ni(II) and Zn(II) with the o-hydroxyacetophenone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H 2 o-HAHNH) containing N and O donor sites have been synthesized. Both ligand and its metal complexes were characterized by different physicochemical methods, elemental analysis, molar conductivity ( 1H NMR, 13C NMR, IR, UV–visible, ESR, MS spectra) and also thermal analysis (TG and DTG) techniques. The discussion of the outcome data of the prepared complexes indicates that the ligand behave as a bidentate and/or tridentate ligand. The electronic spectra of the complexes as well as their magnetic moments suggest octahedral geometries for all isolated complexes. The room temperature solid state ESR spectrum of the Cu(II) complex shows d x2− y2 as a ground state, suggesting tetragonally distorted octahedral geometry around Cu(II) centre. The molar conductance measurements proved that the complexes are non-electrolytes. The kinetic thermodynamic parameters such as: E #, Δ H #, Δ G #, Δ S # are calculated from the DTG curves, for the [Ni(H O -HAHNH) 2] and [Zn(H 2 O -HAHNH)(OAc) 2]·H 2O complexes using the Coats–Redfern equation. Also, the antimicrobial properties of all compounds were studied using a wide spectrum of bacterial and fungal strains. The [Cu(H o-HAHNH)(OAc)(H 2O) 2] complex was the most active against all strains, including Aspergillus sp., Stemphylium sp. and Trichoderma sp. Fungi; E. coli and Clostridium sp. Bacteria.

Synthesis, crystal structure and spectroscopy studies of a novel five-coordinated Zn(II) ion complex with l-tyrosine and imidazole

The new five-coordination zinc(II) complex of formula [Zn(Im)( l-tyr) 2] 2·5H 2O consisting of l-tyrosine ( l-tyr) and imidazole (Im) molecules as ligands was prepared as crystals and characterized by X-ray diffraction, IR-FIR vibrational and UV–Vis electronic spectroscopy. The [Zn(Im)( l-tyr) 2] 2·5H 2O complex crystallizes in the orthorhombic crystal system and P2 12 12 space group. The [ZnN 2N′O 2] chromophore has distorted bipiramidal geometry with value of τ parameter 0.7. The sensitive intra and inter-molecular hydrogen bonds created the layers arrangement and the “pseudo-baskets” fashion. The intraligand charge transfer (ILCT) π– π ∗ and π– π ∗ transitions in the ligands molecule are corresponded to the intensity bands in the UV–Vis region.

Microwave spectrum and structure of C 6H 5CCH⋯H 2S complex

Rotational spectra of C 6H 5CCH⋯H 2S, C 6H 5CCH⋯H 2 34S, C 6H 5CCH⋯HDS, C 6H 5CCH⋯D 2S and C 6H 5CCD⋯H 2S complexes have been observed using a pulsed nozzle Fourier transform microwave spectrometer. The observed spectrum is consistent with a structure in which hydrogen sulfide is located over the phenyl ring π cloud and the distance between the centers of masses of the two monomers is 3.74 ± 0.01 Å. In the complex, the H 2S unit is shifted from the phenyl ring center towards the acetylene group. The vibrationally averaged structure has an effective C s symmetry. Ab initio calculations were performed at MP2/aug-cc-pVDZ level of theory to locate the possible geometries of the complex. The calculations reveal the experimentally observed structure to be more stable than a coplanar arrangement of the monomers, which was observed for the C 6H 5CCH⋯H 2O complex. Atoms in molecule theoretical analysis shows the presence of S–H⋯π hydrogen bond. For the parent isotopologue, each transition frequency was found to split into two resulting from an interchange of the equivalent hydrogens of H 2S unit in the complex.

Effect of the central metal ion on the cleavage of DNA by [M(TPA)Cl]ClO 4 complexes (M = Co II, Cu II and Zn II, TPA = tris(2-pyridylmethyl)amine): An efficient artificial nuclease for DNA cleavage

[M(TPA)Cl]ClO 4· nH 2O complexes ( 1: M = Co II, n = 0; 2: M = Cu II, n = ½; 3: M = Zn II, n = 0) where TPA = tris(2-pyridylmethyl)amine, were synthesized and structurally characterized. The molecular structure of [Cu(TPA)Cl]ClO 4·½H 2O was determined by single crystal X-ray crystallography. In aqueous solution, the complex ions [M(TPA)Cl] + (M = Co II or Cu II) are hydrolyzed to the corresponding aqua species [M(TPA)(H 2O)] 2+. In contrast to the TBP [Cu(TPA)(H 2O)] 2+, the corresponding TBP cobalt(II) species showed severe distortion towards tetrahedral geometry. The interactions of the three complexes with DNA have been investigated at pH 7.0 (1.0 mM Tris–Cl buffer) and 37 °C. Significant DNA cleavages were obtained for complexes 1 and 2, whereas complex 3 did not show any detectable cleavage for DNA. Under pseudo Michaelis–Menten kinetic conditions, the kinetic parameters k cat and K M were determined as k cat = 6.59 h −1 and K M = 2.20 × 10 −4 M for 1 and the corresponding parameters for 2 are k cat = 5.7 × 10 −2 h −1 and K M = 6.9 × 10 −5 M, and the reactivity of the complexes in promoting the cleavage of DNA decreases in the order 1 > 2 ≫ 3. The rate enhancements for the DNA cleavage by 1 and 2 correspond to 1.8 × 10 8 and 1.6 × 10 6, respectively, over the non-catalyzed DNA. The reactivity of the two complexes was discussed in relation to other related artificial nucleases.