Synthesis,spectroscopic evaluation,molecular modelling,thermal study and biological evaluation of manganese(II) complexes derived from bidentate N,O and N,S donor Schiff base ligands

Manganese(II) complexes having the general composition Mn(L)₂X₂ (where L = 3‐bromoacetophenone semicarbazone, 3‐bromoacetophenone thiosemicarbazone, 1‐tetralone semicarbazone, 1‐tetralone thiosemicarbazone, flavanone semicarbazone or flavanone thiosemicarbazone and X = Cl^? or ½SO₄^2?) were synthesized. All the complexes were characterized using elemental analyses, molar conductance and magnetic moment measurements, and mass, ¹H NMR, infrared, electron paramagnetic resonance and electronic spectral studies. The molar conductance of the complexes in dimethylsulfoxide lies in the range 10–20 Ω^?1 cm² mol^?1 indicating their non‐electrolytic nature. All the complexes show magnetic moments corresponding to five unpaired electrons. The possible geometries of the complexes were assigned on the basis of electron paramagnetic resonance, electronic and infrared spectral studies. Some of the synthesized ligands and their complexes were screened for their antifungal activities against fungi Macrophomina phaseolina, Botrytis cinerea and Phoma glomerata using the food poison technique and their antibacterial activities against Xanthomonas campestris pv. campestris and Ralstonia solanacearum using the paper disc diffusion method. They showed appreciable activities.     

Heteroleptic Silylamido Phenolate Complexes of Calcium and the Larger Alkaline Earth Metals: β‐Agostic Ae⋅⋅⋅Si?H Stabilization and Activity in the Ring‐Opening Polymerization of L‐Lactide

The factors governing the stability and the reactivity towards cyclic esters of heteroleptic complexes of the large alkaline earth metals (Ae) have been probed. The synthesis and stability of a family of heteroleptic silylamido and alkoxide complexes of calcium [{LOⁱ}Ca? Nu(thf)_n] supported by mono‐anionic amino ether phenolate ligands (i=1, {LO¹}^?=4‐(tert‐butyl)‐2,6‐bis(morpholinomethyl)phenolate, Nu^?=N(SiMe₂H)₂^?, n=0, 4 ; i=2, {LO²}^?=2,4‐di‐tert‐butyl‐6‐{[2‐(methoxymethyl)pyrrolidin‐1‐yl]methyl}phenolate, Nu^?=N(SiMe₂H)₂^?, n=0, 5 ; i=4, {LO⁴}^?=2‐{[bis(2‐methoxyethyl)amino]methyl}‐4,6‐di‐tert‐butylphenolate, Nu^?=N(SiMe₂H)₂^?, n=1, 6 ; Nu^?=HC?CCH₂O^?, n=0, 7 ) and those of the related [{LO³}Ae? N(SiMe₂H)₂] ({LO³}^?=2‐[(1,4,7,10‐tetraoxa‐13‐azacyclopentadecan‐13‐yl)methyl]‐4,6‐di‐tert‐butylphenolate Ae=Ca, 1 ; Sr, 2 ; Ba, 3 ) have been investigated. The molecular structures of 1 , 2 , [( 4 )₂], 6 , and [( 7 )₂] have been determined by X‐ray diffraction. These highlight Ae???H? Si internal β‐agostic interactions, which play a key role in the stabilization of [{LOⁱ}Ae? N(SiMe₂H)₂] complexes against ligand redistribution reactions, in contrast to regular [{LOⁱ}Ae? N(SiMe₃)₂]. Pulse‐gradient spin‐echo (PGSE) NMR measurements showed that 1 , 4 , 6 , and 7 are monomeric in solution. Complexes 1 – 7 mediate the ring‐opening polymerization (ROP) of L ‐lactide highly efficiently, converting up to 5000 equivalents of monomer at 25 °C in a controlled fashion. In the immortal ROP performed with up to 100 equivalents of exogenous 9‐anthracenylmethanol or benzyl or propargyl alcohols as a transfer agent, the activity of the catalyst increased with the size of the metal ( 1 < 2 < 3 ). For Ca‐based complexes, the enhanced electron‐donating ability of the ancillary ligand favored catalyst activity ( 1 > 6 > 4 ≈ 5 ). The nature of the alcohol had little effect over the activity of the binary catalyst system 1 /ROH; in all cases, both the control and end‐group fidelity were excellent. In the living ROP of L ‐LA, the HC?CCH₂O^? initiating group (as in 7 ) proved superior to N(SiMe₂H)₂^? or N(SiMe₃)₂^? (as in 6 or [{LO⁴}Ca? N(SiMe₃)₂] ( B ), respectively).     

Synthesis,crystal structures and DNA/human serum albumin binding of ternary Cu(II) complexes containing amino acids and 6‐(pyrazin‐2‐yl)‐1,3,5‐triazine‐2,4‐diamino

Two water‐soluble 6‐(pyrazin‐2‐yl)‐1,3,5‐triazine‐2,4‐diamino (pzta)‐based Cu(II) complexes, namely [Cu(l ‐Val)(pzta)(H₂O)]ClO₄ ( 1 ) and [Cu(l ‐Thr)(pzta)(H₂O)]ClO₄ ( 2 ) (l ‐Val: l ‐valinate; l ‐Thr: l ‐threoninate), were synthesized and characterized using elemental analyses, molar conductance measurements, spectroscopic methods and single‐crystal X‐ray diffraction. The results indicated that the molecular structures of the complexes are five‐coordinated and show a distorted square‐pyramidal geometry, in which the central copper ions are coordinated to N,N atoms of pzta and N,O atoms of amino acids. The interactions of the complexes with DNA were investigated using electronic absorption, competitive fluorescence titration, circular dichroism and viscosity measurements. These studies confirmed that the complexes bind to DNA through a groove binding mode with certain affinities (K_b = 4.71 × 10³ and 1.98 × 10³ M^?1 for 1 and 2 , respectively). The human serum albumin (HSA) binding properties of the complexes were also evaluated using fluorescence and synchronous fluorescence spectroscopies, indicating that the complexes could quench the intrinsic fluorescence of HSA in a static quenching process. The relevant thermodynamic parameters revealed the involvement of van der Waals forces and hydrogen bonds in the formation of complex–HSA systems. Finally, molecular docking technology was also used to further verify the interactions of the complexes with DNA/HSA.     

p‐Toluate‐bridged dinuclear Cu(II) complexes in combination with tridentate chelating ligand: Crystal structure,density functional theory calculation,DNA/protein binding and catecholase activity

The dinuclear Cu(II) complexes [Cu₂(L¹)₂(mb)]?ClO₄ ( 1 ) and [Cu₂(L²)₂(mb)]?ClO₄ ( 2 ) (HL¹ = 2‐[(2‐diethylaminoethylimino)methyl]phenol; HL² = 2‐[1‐(2‐diethylaminoethylimino)propyl]phenol; mb = 4‐methylbenzoate) were synthesized and characterized using X‐ray crystal structure analysis and spectroscopic methods. Complexes 1 and 2 are dinuclear with distorted square pyramidal Cu (II) geometries, where Schiff base coordinates with tridentate (N,N,O) chelating mode and mb bridges two metal centres. Optimized structures and photophysical properties of ligands and complexes were calculated using density functional theory and time‐dependent density functional theory methods using B3LYP functional with 6‐31G (d,p) and LanL2MB basis sets. Interactions of the complexes with bovine serum albumin (BSA) and human serum albumin (HSA) were studied using UV–visible absorption and fluorescence spectroscopies and the calculated values of association constants (M^?1) are 1.7 × 10⁵ ( 1 –BSA), 5.7 × 10⁵ ( 2 –BSA), 1.6 × 10⁵ ( 1 –HSA) and 6.9 × 10⁵ ( 2 –HSA). Interactions of the complexes with calf thymus DNA were also investigated and the binding affinities are 1.4 × 10⁵ and 1.6 × 10⁵ M^?1 for 1 and 2 , respectively. Both complexes catalytically oxidize 3,5‐di‐tert‐butylcatechol to 3,5‐di‐tert‐butylbenzoquinone in the presence of molecular oxygen.     

A structure-based analysis of the vibrational spectra of nitrosyl ligands in transition-metal coordination complexes and clusters

The vibrational spectra of nitrogen monoxide or nitric oxide (NO) bonded to one or to several transition-metal (M) atom(s) in coordination and cluster compounds are analyzed in relation to the various types of such structures identified by diffraction methods. These structures are classified in: (a) terminal (linear and bent) nitrosyls, [M(σ-NO)] or [M(NO)]; (b) twofold nitrosyl bridges, [M₂(μ₂-NO)]; (c) threefold nitrosyl bridges, [M₃(μ₃-NO)]; (d) σ/π-dihaptonitrosyls or “side-on” nitrosyls; and (e) isonitrosyls (oxygen-bonded nitrosyls).Typical ranges for the values of internuclear N–O and M–N bond-distances and M–N–O bond-angles for linear nitrosyls are: 1.14–1.20 Å/1.60–1.90 Å/180–160° and for bent nitrosyls are 1.16–1.22 Å/1.80–2.00 Å/140–110°. The [M₂(μ₂-NO)] bridges have been divided into those that contain one or several metal–metal bonds and those without a formal metal/metal bond (M?M). Typical ranges for the M–M, N–O, M–N bond distances and M–N–M bond angles for the normal twofold NO bridges are: 2.30–3.00 Å/1.18–1.22 Å/1.80–2.00 Å/90–70°, whereas for the analogous ranges of the long twofold NO bridges these are 3.10–3.40 Å/1.20–1.24 Å/1.90–2.10 Å/130–110°. In both situations the N–O vector is approximately at right angle to the M–M (or M?M) vector within the experimental error; i.e. the NO group is symmetrical bonded to the two metal atoms. In contrast the threefold NO bridges can be symmetrically or unsymmetrically bonded to an M₃-plane of a cluster compound. Characteristic values for the N–O and M–N bond-distances of these NO bridges are: 1.24–1.28 Å/1.80–1.90 Å, respectively. As few dihaptonitrosyl and isonitrosyl complexes are known, the structural features of these are discussed on an individual basis.The very extensive vibrational spectroscopy literature considered gives emphasis to the data from linearly bonded NO ligands in stable closed-shell metal complexes; i.e. those which are consistent with the “effective atomic number (EAN)” or “18-electron” rule. In the paucity of enough vibrational spectroscopic data from complexes with only nitrosyl ligands, it turned out to be very advantageous to use wavenumbers from the spectra of uncharged and saturated nitrosyl/carbonyl metal complexes as references, because the presence of a carbonyl ligand was found to be neutral in its effect on the ν(NO)-values. The wide wavenumber range found for the ν(NO) values of linear MNO complexes are then presented in terms of the estimated effects of net ionic charges, or of electron-withdrawing or electron-donating ligands bonded to the same metal atom. Using this approach we have found that: (a) the effect for a unit positive charge is [plus 100 cm^?1] whereas for a unit negative charge it is [minus 145 cm^?1]. (b) For electron-withdrawing co-ligands the estimated effects are: terminal CN [plus 50 cm^?1]; terminal halogens [plus 30 cm^?1]; bridging or quasi-bridging halogens [plus 15 cm^?1]. (c) For electro donating co-ligands they are: PF₃ [plus 10 cm^?1]; P(OPh)₃ [?30 cm^?1]; P(OR)₃ (R = alkyl group) [?40 cm^?1]; PPh₃ [?55 cm^?1]; PR₃ (R = alkyl group) [?70 cm^?1]; and η⁵-C₅H₅ [?60 cm^?1]; η⁵-C₅H₄Me [?70 cm^?1]; η⁵-C₅Me₅ [?80 cm^?1]. These values were mostly derived from the spectra of nitrosyl complexes that have been corrected for the presence of only a single electronically-active co-ligand. After making allowance for ionic charges or strongly-perturbing ligands on the same metal atom, the adjusted ‘neutral-co-ligand’ ν(NO)*-values (in cm^?1) are for linear nitrosyl complexes with transition metals of Period 4 of the Periodic Table, i.e. those with atomic orbitals (…4s3d4p): [ca. 1750, Cr(NO)]; [1775,Mn(NO)]; [1796,Fe(NO)]; [1817,Co(NO)]; [ca. 1840, Ni(NO)]. Period 5 (…5s4d5p): [1730 Mo(NO)]; [—, Tc(NO)]; [1745,Ru(NO)]; [1790,Rh(NO)]; [ca. 1845, Pd(NO)]. Period 6 (…6s4f5d6p), [1720,W(NO)]; [1730,Re(NO)]; [1738,Os(NO)]; [1760,Ir(NO)]; [—, Pt] respectively. Environmental differences to these values, e.g. data taken in polar solutions or in the crystalline state, can cause ν(NO)* variations (mostly reductions) of up to ca. 30 cm^?1.Three spectroscopic criteria are used to distinguish between linear and bent NO groups. These are: (i) the values of ν(¹⁴NO) themselves, and (ii) the isotopic band shift – (IBS) – parameter which is defined as [ν(¹⁴NO)–ν(¹⁵NO)], and, (iii) the isotopic band ratio – (IBR) – given by [ν(¹⁵NO/ν¹⁴NO)]. The former is illustrated with the ν(¹⁴NO)-data from trigonal bipyramidal (TBP) and tetragonal pyramidal (TP) structures of [M(NO(L)₄] complexes (where M = Fe, Co, Ru, Rh, Os, Ir and L = ligand). These values indicate that linear (180–170°) and strongly bent (130–120°) NO groups in these compounds absorb over the 1862–1690 cm^?1 and 1720–1525 cm^?1-regions, respectively. As was explicitly demonstrated for the linear nitrosyls, these extensive regions reflect the presence in different complexes of a very wide range of co-ligands or ionic charges associated with the metal atom of the nitrosyl group. A plot of the IBS parameter against M–N–O bond-angle for compounds with general formulae [M(NO)(L)_y] (y = 4, 5, 6) reveals that the IBS-values are clustered between 45 and 30 cm^?1 or between 37 and 25 cm^?1 for linear or bent NO groups, respectively. A plot of IBR shows a less well defined pattern. Overall it is suggested that bent nitrosyls absorb ca. 60–100 cm^?1 below, and have smaller co-ligand band-shifts, than their linear counterparts.Spectroscopic ν(NO) data of the bridging or other types of NO ligands are comparatively few and therefore it has not been possible to give other than general ranges for ‘neutral co-ligand’ values. Moreover the bridging species data often depend on corrections for the effects of electronically-active co-ligands such as cyclopentadienyl-like groups. The derived neutral co-ligand estimates, ν(NO)*, are: (a) twofold bridged nitrosyls with a metal–metal bond order of one, or greater than one, absorb at ca. 1610–1490 cm^?1; (b) twofold bridged nitrosyl ligands with a longer non-bonding M?M distance, ca. 1520–1490 cm^?1; (c) threefold bridged nitrosyls, ca. 1470–1410 cm^?1; (d) σ/π dihaptonitrosyl, [M(η²-NO)], where M = Cr, Mn and Ni; ca. 1490–1440 cm^?1. Isonitrosyls, from few examples, appear to absorb below ca. 1100 cm^?1.To be published DFT calculations of the infrared and Raman spectra of complexes with formulae [M(NO)_4?n(CO)_n] (M = Cr, Mn, Fe, Co, Ni, and n = 0, 1, 2, 3, 4, respectively) are used as models for the assignments of the ν(MN) and δ(MNO) bands from more complex metal nitrosyls.     

A novel azocompound, 2‐(4‐phenylazoaniline)‐4‐phenylphenol: Spectroscopic and quantum‐chemical approach

A novel azocompound with two nonequivalents azo groups, 2‐(4‐phenylazoaniline)‐4‐phenylphenol, was synthesized and characterized by spectroscopic and computational analysis. An intramolecular hydrogen bonding (HB), ? O₁? H₁ ··· N₁? , involving the ? N₁?N₂? group and the proton in a neighbor hydroxyl moiety, was identified. It was found responsible for a characteristic π‐conjugated H₁? O₁? C₁₈?C₁₃? N₂?N₁? six‐membered cyclic fragment. It is worth noting that this azo group is involved in an azo‐hydrazo equilibrium, being the azo form the most stable one. This resonance‐assisted HB was characterized using the OH‐related infrared bands and the corresponding signals in ¹H NMR. In addition, conformational studies and geometrical and electronic parameter calculations were performed using the density functional theory, at B3LYP/6‐311++G** level. Bond and ring critical points were identified using the atoms in molecules theory, which allowed confirming the intramolecular HB. The second azo‐group cannot be involved in HB, but it also presents two stereoisomerics forms corresponding to cis (Z) and trans (E) configurations, with the later being the one with the lowest energy. © 2013 Wiley Periodicals, Inc.     

Synthesis and characterization of Ni (II) complexes supported by phenoxy/naphthoxy‐imine ligands with pendant N‐ and O‐donor groups and their use in ethylene oligomerization

A series of new Ni(II) complexes of general formula Ni{ZNO} Br ( 2a‐i ) (ZNO = phenoxy/naphthoxy‐imine with pendant N‐ and O‐donor groups) were prepared and characterized by elemental analysis, IR spectroscopy, ESI‐HRMS, and by X‐ray crystallography for 2e . In the solid state, 2e features a monomeric structure with κ³ coordination of the monoanionic naphthoxy‐imine‐quinoline ligand onto the nickel center. Upon activation with MAO, both classes of nickel catalysts were able to produce selectively 1‐butene (81.5–92.1 wt%) with turnover frequencies (TOFs) varying from 3,100 to 24,300 mol(C₂H₄) mol (Ni)^?1 h^?1. Nickel precatalysts bearing phenoxy‐imine ligands were much more active than its naphthoxy analogous under the same conditions. The use of a mixture of cocatalysts (MAO/TMA or MAO/TiBA) resulted in poor activities; however the presence of TiBA in the milieu led to a significant improvement on selectivity for 1‐hexene (25.5 wt%). Under optimized conditions ([Ni] = 10 μmol, 30 °C, oligomerization time = 5 min, 20 bar ethylene, [Al]/[Ni] = 600), precatalyst 2c led to TOF = 59,900 mol(C₂H₄) mol(Ni)^?1 h^?1 and selectivity for 1‐butene of 89.5 wt%.     

Synthesis,characterization, DNA binding,cytotoxicity and molecular docking properties of Cu (II) and Mn (II) complexes with 1,4‐bis (pyrazol‐1‐yl) terephthalic acid

Two novel complexes, [Cu (L)(H₂O)]?H₂O ( 1 ) and [Mn (H₂O)₆] ?L ?H₂O ( 2 ) (L = 1,4‐bis (pyrazol‐1‐yl) terephthalic acid), were synthesized under hydrothermal conditions. They were characterized using elemental analysis, infrared spectroscopy and single‐crystal X‐ray diffraction. Intramolecular weak interactions, such as hydrogen bonds, and intermolecular interactions play important roles in the construction of the complexes. The interaction of these complexes with fish sperm DNA (FS‐DNA) was monitored and binding constants were determined using UV–visible spectroscopy, which revealed their ability to bind to FS‐DNA, with binding constants for the two complexes of 1.88 × 10⁴ M^?1 ( 1 ) and 1.06 × 10⁴ M^?1 ( 2 ). Viscosity experiments further demonstrated the binding of the complexes to DNA. The complexes were further studied using gel electrophoresis assay with supercoiled plasmid pBR322 DNA. In addition, anticancer activities of the metal complexes investigated through MTT assays in vitro indicated good cytotoxic activity against cancer cell lines. Flow cytometry and apoptosis experiments showed that these complexes induced apoptosis of two different cancer cell lines (HeLa and KB cells), demonstrating a significant cancer cell inhibitory rate. Finally, a further molecular docking technique was employed to confirm the binding of the complexes towards the molecular target DNA.     

Synthesis,Spectroscopic and Electrochemical Studies of Isomeric Dichloro-bis-[ N (1)-Alkyl-2-(Arylazo)Imidazole]-Osmium(II). Single Crystal X-ray Structures of Blue-Violet Dichloro-Bis-[ N (1)-Methyl-2-(Arylazo)Imidazole]-Osmium(II) Species

1-Alkyl-2-(arylazo)imidazoles (p-R-C₆H₄-N=N-C₃H₂N₂X, abbreviated as RaaiX, R = H(a), CH₃(b), Cl(c); X = N(1)-CH₃ (1), N(1)-CH₂-C₆H₅ (2)) have been reacted with (NH₄)₂[OsCl₆] and OsCl₂(RaaiX)₂ species isolated in two isomeric forms, blue-violet (3, 5) and red-violet (4, 6). IR spectra show two x (Os-Cl) modes and support a cis-OsCl₂ configuration. X-ray diffraction methods were used to determine structures of blue-violet isomers. In terms of the three coordination pairs around Os(II), Cl, Cl, N, N (N(imidazole), N) and N', N' (N(azo), N') the blue-violet isomers have a cis-trans-cis (ctc) configuration. ¹H NMR data for the red-violet complexes (isomers B) and results concerning analogous ruthenium(II) complexes indicate isomer B to have cis-cis-cis (ccc) configuration. Absorption spectra show an intense MLCT band at ca 580 nm along with two weak bands at 800 and 1000 nm. Cyclic voltammetry shows quasi-reversible Os(III)/Os(II) and Os(IV)/Os(III) couples at 0.4-0.6 V and 1.3-1.5 V versus SCE and ill-defined azo reductions. The X-Ray structures show unusually long N=N bond lengths, 1.31-1.32 Å, elongated by some 0.06 Å compared to the free ligand value. Os(II) prefers to bind N(azo) (Os-N(azo), 1.98 Å) rather than N(imidazole) (Os-N(imidazole), 2.03 Å). EHMO calculations of ctc-OsCl₂ (MeaaiMe) and comparison with the ruthenium(II) complex account for the MLCT transitions in terms of a metal-dominated HOMO to a ligand-dominated LUMO shift.     

Synthesis,Crystal Structure,and Magnetic Property of New Trispin Ln(III)‐Nitronyl Nitroxide Complexes

Four Ln(III) complexes based on a new nitronyl nitroxide radical have been synthesized and structurally characterized: {Ln(hfac)₃[NITPh(MeO)₂]₂} (Ln = Eu( 1 ), Gd( 2 ), Tb( 3 ), Dy( 4 ); NITPh(MeO)₂ = 2‐(3′,4′‐dimethoxyphenyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide; hfac = hexafluoroacetylacetonate). The single‐crystal X‐ray diffraction analysis shows that these complexes have similar mononuclear trispin structures, in which central Ln(III) ion is eight‐coordinated by two O‐atoms from two nitroxide groups and six O‐atoms from three hfac anions. The variable temperature magnetic susceptibility study reveals that there exist ferromagnetic interactions between Gd(III) and the radicals, and antiferromagnetic interactions between two radicals (J_Gd‐Rad = 3.40 cm^?1, J_Rad‐Rad = ?9.99 cm^?1) in complex 2 . Meanwhile, antiferromagnetic interactions are estimated between Eu(III) (or Dy(III)) and radicals in complexes 1 and 4 , and ferromagnetic interaction between Tb(III) and radicals in complex 3 , respectively.     

Antioxidative vs cytotoxic activities of organotin complexes bearing 2,6‐di‐tert‐butylphenol moieties

Two series of organotin(IV) complexes with Sn–S bonds on the base of 2,6‐di‐tert‐butyl‐4‐mercaptophenol ( L ¹ SH ) of formulae Me₂Sn(L¹S)₂ ( 1 ); Et₂Sn(L¹S)₂ ( 2 ); Bu₂Sn(L¹S)₂ ( 3 ); Ph ₂ Sn(L¹S)₂ ( 4 ); (L¹)₂Sn(L¹S)₂ ( 5 ); Me₃Sn(L¹S) ( 6 ); Ph₃Sn(L¹S) ( 7 ) (L¹ = 3,5‐di‐tert‐butyl‐4‐hydroxyphenyl), together with the new ones [Me₃SnCl(L²)] ( 8 ), [Me₂SnCl₂(L²)₂] ( 9 ) ( L ²  = 2‐(N‐3′,5′‐di‐tert‐butyl‐4′‐hydroxyphenyl)‐iminomethylphenol) were used to study their antioxidant and cytotoxic activity. Novel complexes 8 , 9 of Me_nSnCl_4 ? n (n = 3, 2) with Schiff base were synthesized and characterized by ¹H, ¹³C NMR, IR and elemental analysis. The crystal structures of compounds 8 and 9 were determined by X‐ray diffraction analysis. The distorted tetrahedral geometry around the Sn center in the monocrystals of 8 was revealed, the Schiff base is coordinated to the tin(IV) atom by electrostatic interaction and formation of short contact Sn–O 2.805 Å. In the case of complex 9 the distorted octahedron coordination of Sn atom is formed. The antioxidant activity of compounds as radical scavengers and reducing agents was proved spectrophotometrically in tests with stable radical DPPH, reduction of Cu²⁺ (CUPRAC method) and interaction with superoxide radical‐anion. Moreover, compounds have been screened for in vitro cytotoxicity on eight human cancer cell lines. A high activity against all cell lines with IC₅₀ values 60–160 nM was determined for the triphenyltin complex 7 , while the introduction of Schiff base decreased the cytotoxicity of the complexes. The influence on mitochondrial potential and mitochondrial permeability for the compounds 8 and 9 has been studied. It is shown that studied complexes depolarize the mitochondria but don't influence the calcium‐induced mitochondrial permeability transition.     

DFT Calculations,Spectroscopic Studies,Biological Activity and Non Linear Optical Properties (NLO) of Novel Ternary Cu(II)‐Chelates Derived from 5‐Acetyl‐4‐hydroxy‐2H‐1,3‐thiazinedione

New ternary Cu(II)‐chelates with the general formula [ML L′(H₂O)_x] (NO₃)_y x (H₂O), x = 0–2 and y = 0–1, (L) = 5‐acetyl‐4‐hydroxy‐2H‐1,3‐thiazine‐2,6(3H)‐dione with in the presence of a secondary ligand (L′) [N,O‐donor; 8 hydroxyquinoline or N,N‐donor; 1,10‐phenanthroline and diethethylendiamine]. Characterization of the synthesized complexes was established based on elemental analysis, molar conductance, magnetic susceptibility measurements, spectral (infrared, electronic, mass, ¹H‐NMR and ESR) as well as thermal gravimetric analysis (TGA). The complexes exhibited octahedral and square planer geometry. The antimicrobial activity for the studied complexes was tested for different kind of organisms. The geometrical and non‐linear optical parameters of the studied complexes 1–3 are investigated theoretically at the B3LYP/GENECP level of theory. The optimized geometries of the studied complexes are non‐planner as indicated from the dihedral angles. The natural charge population (core, valence and Rydberg), exact electronic configuration, total Lewis, and total non‐Lewis is computed and discussed in terms of natural bond orbitals (NBO) analysis. The calculated E_HOMO and E_LUMO energies at the same level of theory of the studied complexes were used to calculate the global properties; hardness (η), global softness (S), electrophilicity (ω) and electronegativity (χ). The total dipole moment (μ_tot), total and anisotropy of polarizability (? α ?), (Δα) and first hyperpolarizability (? β ?) values were calculated and compared with urea as a reference compound. From the values of the computed first hyperpolarizability (? β ?), the ligand and the studied complexes show promising optical properties.     

Complexation Properties of N,N′,N″,N′′′‐[1,4,7,10‐Tetraazacyclododecane‐1,4,7,10‐tetrayltetrakis(1‐oxoethane‐2,1‐diyl)]tetrakis[glycine] (H4dotagl). Equilibrium,Kinetic, and Relaxation Behavior of the Lanthanide(III) Complexes

Eu³⁺, Dy³⁺, and Yb³⁺ complexes of the dota‐derived tetramide N,N′,N″,N′′′‐[1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetrayltetrakis(1‐oxoethane‐2,1‐diyl)]tetrakis[glycine] (H₄dotagl) are potential CEST contrast agents in MRI. In the [Ln(dotagl)] complexes, the Ln³⁺ ion is in the cage formed by the four ring N‐atoms and the amide O‐atom donor atoms, and a H₂O molecule occupies the ninth coordination site. The stability constants of the [Ln(dotagl)] complexes are ca. 10 orders of magnitude lower than those of the [Ln(dota)] analogues (H₄dota=1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid). The free carboxylate groups in [Ln(dotagl)] are protonated in the pH range 1–5, resulting in mono‐, di‐, tri‐, and tetraprotonated species. Complexes with divalent metals (Mg²⁺, Ca²⁺, and Cu²⁺) are also of relatively low stability. At pH>8, Cu²⁺ forms a hydroxo complex; however, the amide H‐atom(s) does not dissociate due to the absence of anchor N‐atom(s), which is the result of the rigid structure of the ring. The relaxivities of [Gd(dotagl)] decrease from 10 to 25°, then increase between 30–50°. This unusual trend is interpreted with the low H₂O‐exchange rate. The [Ln(dotagl)] complexes form slowly, via the equilibrium formation of a monoprotonated intermediate, which deprotonates and rearranges to the product in a slow, OH^?‐catalyzed reaction. The formation rates are lower than those for the corresponding Ln(dota) complexes. The dissociation rate of [Eu(dotagl)] is directly proportional to [H⁺] (0.1–1.0M HClO₄); the proton‐assisted dissociation rate is lower for [Eu(H₄dotagl)] (k₁=8.1?10^?6 M ^?1 s^?1) than for [Eu(dota)] (k₁=1.4?10^?5 M ^?1 s^?1).     

Synthesis,Structural, Biological Evaluation,Molecular Docking and DFT Studies of Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) Complexes bearing Heterocyclic Thiosemicarbazone ligand

A new ligand, 2‐aminonicotinaldehyde N‐methyl thiosemicarbazone (ANMTSC) and its metal complexes [Co(II) ( 1 ); Ni(II) ( 2 ); Cu(II) ( 3 ); Zn(II) ( 4 ); Cd(II) ( 5 ) or Hg(II) ( 6 )] were synthesized. The compounds were characterized by analytical methods and various spectroscopic (infrared, magnetic, thermal, ¹H, ¹³C NMR, electronic and ESR) tools. The structure of ANMTSC ligand was confirmed by single crystal X‐ray diffraction study. The spectral data of metal complexes indicate that the ligand acts as mononegative, bidentate coordination through imine nitrogen (N) and thiocarbonyl sulphur (S^?) atoms. The proposed geometries for complexes were octahedral ( 1 – 2 ), distorted octahedral ( 3 ) and tetrahedral ( 4 – 6 ). Computational details of theoretical calculations (DFT) of complexes have been discussed. The compounds were subjected to antimicrobial, antioxidant, antidiabetic, anticancer, ROS, studies and EGFR targeting molecular docking analysis. Complex 5 has shown excellent antibacterial activity and the complexes 2 and 5 have shown good antifungal activity. The complexes 1 and 4 displayed good antioxidant property with IC₅₀ values of 11.17 ± 1.92 μM and 10.79 ± 1.85 μM, respectively compared to standard. In addition, in vitro anticancer activity of the compounds was investigated against HeLa, MCF‐7, A549, IMR‐32 and HEK 293 cell lines. Among all the compounds, complex 4 was more effective against HeLa (IC₅₀ = 10.28 ± 0.69 μM), MCF‐7 (IC₅₀ = 9.80 ± 0.83 μM), A549 (IC₅₀ = 11.08 ± 0.57 μM) and IMR‐32 (10.41 ± 0.60 μM) exhibited superior anticancer activity [IC₅₀ = 9.80 ± 0.83 ( 4 ) and 9.91 ± 0.37 μM ( 1 )] against MCF‐7 compared with other complexes.     

Alcohol oxidation reactions catalyzed by ruthenium–carbonyl complexes of thioarylazoimidazoles

Alcohols are oxidized by N‐methylmorpholine‐N‐oxide (NMO), Bu^tOOH and H₂O₂ to the corresponding aldehydes or ketones in the presence of catalyst, [RuH(CO)(PPh₃)₂(SRaaiNR′)]PF₆ ( 2 ) and [RuCl(CO)(PPh₃)(S_κRaaiNR′)]PF₆ ( 3 ) (SRaaiNR′ ( 1 ) = 1‐alkyl‐2‐{(o‐thioalkyl)phenylazo}imidazole, a bidentate N(imidazolyl) (N), N(azo) (N′) chelator and S_κRaaiNR′ is a tridentate N(imidazolyl) (N), N(azo) (N′), S_κ‐R is tridentate chelator; R and R′ are Me and Et). The single‐crystal X‐ray structures of [RuH(CO)(PPh₃)₂(SMeaaiNMe)]PF₆ ( 2a ) (SMeaaiNMe = 1‐methyl‐2‐{(o‐thioethyl)phenylazo}imidazole) and [RuH(CO)(PPh₃)₂(SEtaaiNEt)]PF₆ ( 2b ) (SEtaaiNEt = 1‐ethyl‐2‐{(o‐thioethyl)phenylazo}imidazole) show bidentate N,N′ chelation, while in [RuCl(CO)(PPh₃)(S_κEtaaiNEt)]PF₆ ( 3b ) the ligand S_κEtaaiNEt serves as tridentate N,N′,S chelator. The cyclic voltammogram shows Ru^III/Ru^II (~1.1 V) and Ru^IV/Ru^III (~1.7 V) couples of the complexes 2 while Ru^III/Ru^II (1.26 V) couple is observed only in 3 along with azo reductions in the potential window +2.0 to ?2.0 V. DFT computation has been used to explain the spectra and redox properties of the complexes. In the oxidation reaction NMO acts as best oxidant and [RuCl(CO)(PPh₃)(S_κRaaiNR′)](PF₆) ( 3 ) is the best catalyst. The formation of high‐valent Ru^IV=O species as a catalytic intermediate is proposed for the oxidation process. Copyright © 2014 John Wiley & Sons, Ltd.     

Vanadium(III) complexes containing phenoxy–imine–thiophene ligands: Synthesis,characterization and application to homo‐ and copolymerization of ethylene

A set of vanadium(III) complexes, namely {SNO}VCl₂(THF)₂ ( 2a , SNO = thiophene‐(N═CH)‐phenol; 2b , SNO = 5‐phenylthiophene‐(N═CH)‐phenol; 2c , SNO = 5‐phenylthiophene‐(N═CH)‐4‐tert ‐butylphenol; 2d , SNO = 5‐methylthiophene‐(N═CH)‐phenol; 2e , SNO = 5‐methylthiophene‐(N═CH)‐4‐tert ‐butylphenol; 2f , SNO = 5‐methylthiophene‐(N═CH)‐2‐methylphenol; 2g , SNO = 5‐methylthiophene‐(N═CH)‐4‐fluorophenol), were synthesized by reaction of VCl₃(THF)₃ with phenoxy–imine–thiophene proligands ( 1a – g ). All vanadium(III) complexes were characterized using elemental analysis and infrared and electron paramagnetic resonance spectroscopies. Upon activation with methylaluminoxane (MAO), vanadium precatalysts 2a – g proved active in the polymerization of ethylene (213.6–887.2 kg polyethylene (mol[V])⁻¹⋅h⁻¹), yielding high‐density polyethylenes with melting temperatures in the range 133–136 °C and crystallinities varying from 28 to 41%. The 2e/ MAO catalyst system was able to copolymerize ethylene with 1‐hexene affording poly(ethylene‐co ‐1‐hexene)s with melting temperatures varying from 126 to 102 °C and co‐monomer incorporation in the range 3.60–4.00%.     

Synthesis,Interionic Structure,and Reactivity toward CO and p‐Methylstyrene of Palladacyclic Compounds Bearing α‐Diimine Ligands

Palladacyclic compounds [Pd(C₆H₄(C₆H₅C?O)C?N? R)(N? N)] [X] (R = Et, ⁱPr, 2,6‐ⁱPr₂C₆H₃; N? N = bpy = 2,2′‐bipyridine, or 1,4‐(o,o′‐dialkylaryl)‐1,4‐diazabuta‐1,3‐dienes; [X]^? = [BF₄]^? or [PF₆]^?) were synthesized from the dimers [{Pd(C₆H₄(C₆H₅C?O)C?N? R)(μ‐Cl)}₂] and N? N ligands. Their interionic structure in CD₂Cl₂ was determined by means of ¹⁹F,¹H‐HOESY experiments and compared with that in the solid state derived from X‐ray single‐crystal studies. [Pd(C₆H₄(C₆H₅C?O)C?N? R)(N? N)] [X] complexes were found to copolymerize CO and p‐methylstyrene affording syndiotactic or isotactic copolymers when bpy or 1,4‐(o,o′‐dimethylaryl)‐1,4‐diazabuta‐1,3‐dienes were used, respectively. The reactions with CO and p‐methylstyrene of the bpy derivatives were investigated. Two intermediates derived from a single and a double insertion of CO into the Pd? C bonds were isolated and completely characterized in solution.     

Polymer complexes: supramolecular modeling for determination and identification of the bond lengths in novel polymer complexes from their infrared spectra

Synthesis and characterization of allyl propenyl‐2‐(4‐derivatives phenylazo)butan‐3‐one (HL_n) are described. The monomers obtained contain N?N and carbonyl functional groups in different positions with respect to the allyl group. This structural difference affects the stereochemical structure of the uranyl polymer complexes prepared by the direct reaction of uranyl acetate with the monomers. The polymer complexes are characterized by elemental analyses, ¹H and ¹³C NMR, electronic and vibrational spectroscopy and other theoretical methods. The bonding sites of the hydrazone are deduced from IR and NMR spectra and each of the ligands were found to bond to the UO₂²⁺ ion in a bidentate fashion. The monomers obtained contain N?N and carbonyl functional groups in different positions with respect to the allyl group. IR spectra show that the allyl azo homopolymer (HL_n) acts as a neutral bidentate ligand by coordinating via the two oxygen atom of the carbonyl group, thereby forming a six‐membered chelating ring. The υ₃ frequency of UO₂²⁺ has been shown to be a good molecular probe for studying the coordinating power of the ligands. The υ₃‐values of UO₂²⁺ from IR spectra have been used to calculate the force constant, F_UO (in 10^?8 N/Å) and the bond length R_UO (in Å) of the U? O bond. We adopted a strategy based upon both theoretical and experimental investigations. The theoretical aspects are described in terms of the well‐known theory of 5d–4f transitions. The necessary structural data (coordination geometries and electronic structures) are determined from a framework for the modeling of novel polymer complexes. The Wilson, G. F. matrix method, Badger's formula and the Jones and El‐Sonbati equations were used to determine the stretching and interaction force constants from which the U? O bond distances were calculated. The bond distances of these complexes were also investigated. The effect of Hamett's constant is also discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Preparation,characterization, biological activity,density functional theory calculations and molecular docking of chelates of diazo ligand derived from m‐phenylenediamine and p‐chlorophenol

A novel azo dye ligand, 2,2′‐(1,3‐phenylenebis(diazene‐2,1‐diyl))bis(4‐chlorophenol), was synthesized from the diazotization of m ‐phenelyenediamine and coupling with p ‐chlorophenol in alkaline medium. Mononuclear Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes of the azo ligand (H₂L) were prepared and characterized using elemental analyses, infrared spectroscopy, electron spin resonance, magnetic susceptibility, conductance measurements and thermal analyses. The UV–visible, ¹H NMR and mass spectra of the ligand and its chelates were also recorded. The analytical data showed that the metal‐to‐ligand ratio in the mononuclear azo complexes was 1:1. Diffuse reflectance and magnetic moment measurements revealed the complexes to have octahedral geometry. The infrared spectral data showed that the chelation behaviour of the ligand towards transition metal ions was through phenolic oxygen and azo nitrogen atoms. The electronic spectral results indicated the existence of π → π* (phenyl rings) and n → π* (─N═N) and confirmed the mentioned structure. Molar conductivity revealed the non‐electrolytic nature of all chelates. The presence of water molecules in all complexes was supported by thermal studies. Molecular docking was used to predict the binding between H₂L and the receptors of breast cancer mutant 3hb5‐oxidoreductase, crystal structure of Escherichia coli (3 t88) and crystal structure of Staphylococcus aureus (3q8u). The molecular and electronic structure of H₂L was optimized theoretically and the quantum chemical parameters were calculated. In addition, the effects of the H₂L azo ligand and its complexes on the inhibition of bacterial or fungal growth were evaluated. The prepared complexes had enhanced activity against bacterial or fungal growth compared to the H₂L azo ligand.     

Structurally characterized homotrinuclear Salamo‐type nickel(II) complexes: Synthesis,solvent effect and fluorescence properties

Four new solvent‐induced Ni(II) complexes with chemical formulae [{NiL(μ₂‐OAc)(MeOH)}₂Ni]·2MeOH ( 1 ), [{NiL(μ₂‐OAc)}₂(n‐PrOH)(H₂O)Ni]·n‐PrOH ( 2 ), [{NiL(μ₂‐OAc)(DMF)}₂Ni] ( 3 ) and [{NiL(μ₂‐OAc)(DMSO)}₂Ni]·2DMSO ( 4 ), (H₂L = 4‐Nitro‐4′‐chloro‐2,2′‐[(1,3‐propylene)dioxybis(nitrilomethylidyne)]diphenol) have been synthesized and characterized by elemental analyses, FT‐IR, UV–Vis spectra and X‐ray crystallography. X‐ray crystal structure determinations revealed that each of the Ni(II) complexes 1–4 consists of three Ni(II) atoms, two completely deprotonated (L)^2? units, two μ₂‐acetate ions and two coordinated solvent molecules (solvents are methanol, n‐propanol, water, N,N‐dimethylformamide and dimethyl sulphoxide, respectively). Although the four complexes 1–4 were synthesized in different solvents, it is worthwhile that the Ni(II) atoms in the four complexes 1–4 adopt hexa–coordinated with slightly distorted octahedral coordination geometries, and the ratios of the ligand H₂L to Ni(II) atoms are all 2: 3. The complexes 1–4 possess self‐assembled infinite 1D, 3D, 1D and 2D supramolecular structures via the intermolecular hydrogen bonds, respectively. In addition, fluorescence behaviors were investigated in the complexes 1–4 .