Synthesis,characterization, molecular modelling and biological activity of 2‐(pyridin‐1‐ium‐1‐yl) acetate and its Cu2+, Pt4+, Pd2+, Au3+ and Nd3+ complexes

A new series of Cu²⁺, Pt⁴⁺, Pd²⁺, Au³⁺ and Nd³⁺ complexes derived from 2‐(pyridin‐1‐ium‐1‐yl) acetate have been synthesized and characterized using elemental analyses, spectral (infrared (IR), UV–visible, mass, ¹³C NMR and ¹H NMR), magnetic and thermal measurements. IR results suggest that the ligand acts in a neutral monodentate fashion in all complexes. Octahedral geometry is proposed for Cu²⁺ and Pt⁴⁺ complexes and square‐planar for Pd²⁺ and Au³⁺ complexes. The bond lengths, bond angles, and HOMO and LUMO were calculated. Superoxide dismutase‐like radical scavenger activity and cytotoxic activity of the isolated complexes on HepG2 liver cancer cells have been screened. Ligand and complexes (Pt⁴⁺ and Nd³⁺) exhibit potent antioxidant activity upon coordination while Cu²⁺ and Au³⁺ complexes do not show superoxide dismutase‐like radical scavenger activity. The cytotoxic activity assay against HepG2 cell line proves that the ligand and its Pt⁴⁺ complex have a high cytotoxic activity, while the other complexes showed no cytotoxic activity. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis,characterization, density functional theory,X‐ray study,thermal stability,and biological and MOE relevance of metal complexes of griseofulvin

Metal(II) and metal(III) coordination compounds of griseofulvin (GFV) drug were synthesized. The structure of the ligand was determined on the basis of elemental analyses, infrared and ¹H NMR spectroscopies and thermal studies. GFV behaved as a neutral tridentate chelating agent and coordinated to metal ions through three oxygen atoms: two methoxy groups and oxygen atom of furan ring. Metal complexes were characterized by means of elemental analyses and molar conductance, spectral (infrared, electron spin resonance) and thermal studies. All the complexes showed molar conductance behaviour corresponding to an electrolytic nature. All the complexes showed octahedral geometry, except [Zn(GFV)Cl]Cl that showed tetrahedral geometry. Density functional theory (DFT) calculations were employed to understand and estimate the contribution of each interaction in the formation of the assembly using several theoretical models. The computed parameters from DFT calculations for structure optimizations and vibrational frequencies were in good agreement with the experimental data. Newly synthesized metal complexes in addition to GFV were examined against opportunistic pathogens. The biological applications of complexes were studied with two Gram‐positive bacteria (Bacillus subtilis and Staphylococcus aureus) and two Gram‐negative bacteria (Escherichia coli and Neisseria gonorrhoeae) as well as their antifungal activity against Candida albicans. Results suggested that metal complexes were more biologically sensitive than free ligand. The complexes showed a moderate inhibition of MCF7 breast cancer cell line growth. Molecular docking studies further helped in understanding the mode of action of the compounds through their various interactions with the crystal structures of: human serum albumin (PDB: 5FUO), Staphylococcus aureus nucleoside (PDB: 3Q8U), human acetylcholinesterase (PDB: 1B41) and the human DNA–Topo I complex (PDB: 1SC7).     

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.     

Synthesis and characterization of metal complexes of azo dye based on 5‐nitro‐8‐hydroxyquinoline and their applications in dyeing polyester fabrics

New Mn(II), Ni(II), Co(II) and Cu(II) complexes of an azo dye ligand based on p ‐phenylenediamine with 5‐nitro‐8‐hydroxyquinoline were synthesized and characterized using elemental analysis, inductive coupled plasma analysis, molar conductance, powder X‐ray diffraction, thermogravimetric analysis, magnetic moment measurements, and infrared, ¹H NMR, electron ionization mass and UV–visible spectral studies. The spectral and analytical data reveal that the azo dye ligand acts as a monobasic bidentate ligand via deprotonated OH and nitrogen atom of the quinoline ring. The data support the formulation of all complexes with a 2:1 ligand‐to‐metal ratio, except the Mn(II) complex that has a mononuclear formula. All complexes have an octahedral structure. The molar conductance data reveal that all the metal complexes are non‐electrolytic in nature. From the X‐ray data, the average particle size of the ligand and its complexes is 0.32–0.64 nm. The colour fastness to light, washing, perspiration, sublimation and rubbing of the prepared ligand and its complexes on polyester fabrics and colorimetric properties were measured. The results reveal that the ligand and its complexes have a good to moderate affinity to polyester fibres.     

A new azo‐Schiff base: Synthesis,characterization, biological activity and theoretical studies of its complexes

A new Azo‐Schiff base ligand L was prepared by reaction of m‐hydroxy benzoic acid with (Schiff base B) of 3‐[2‐(1H–indol‐3‐yl)‐ethylimino]‐1.5‐dimethyl‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐ylamine. This synthesized ligand was used for complexation with different metal ions like Ni(II), Co(II), Pd(II) and Pt(IV) by using a molar ratio of ligand: metal as 1:1. Resulted compounds were characterized by NMR (¹H and ¹³C), UV–vis spectroscopy, TGA, FT‐IR, MS, elemental analysis, magnetic moment and molar conductivity studies. The activation thermodynamic parameters, such as ΔE*, ΔH^*, ΔS^*, ΔG^*and K are calculated from the TGA curves using Coats ‐ Redfern method. Hyper Chem‐8 program has been used to predict structural geometries of compounds in gas phase. The biological activities of Schiff base and its complexes had been tested in vitro against, two Gram positive bacteria (Bacillus subtillis and Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli and Pseudomonas aeruguinosa).     

Spectroscopic characterization,thermogravimetry, density functional theory and biological studies of some mixed‐ligand complexes of meloxicam and 2,2′‐bipyridine with some transition metals

The mixed‐ligand Mn(II), Fe(III), Ni(II), Cu(II), Zn(II) and Zr(IV) complexes of meloxicam (H₂mel) and 2,2′‐bipyridine (Bipy) were prepared and characterized. For all complexes, the analytical and spectroscopic results revealed that H₂mel acts in a monobasic bidentate manner through the oxygen of the amide and nitrogen of the thiazole groups, whereas Bipy coordinates through the two nitrogen atoms with slightly distorted octahedral geometry. Thermodynamic parameters (E, ΔS^*, ΔH^* and ΔG^*) were calculated using Coats–Redfern and Horowitz–Metzger methods. The geometries of H₂mel and the complexes were carefully studied using density functional theory to predict the properties of materials performed using the hybrid density functional method B3LYP. All studied complexes are soft with respect to H₂mel where η varies from 0.096 for Zn(II) complex to 0.067 for Fe(III) complex and σ varies from 10.42 to 14.93 eV, while η and σ for H₂mel are 0.14 and 7.14 eV, respectively. The antibacterial activities of the ligands and metal complexes were investigated and the data show that the complexes are active against some bacterial species compared with H₂mel.     

Crystal structure,characterization and catalytic activities of Cu(II) coordination complexes with 8‐hydroxyquinoline and pyrazine‐2‐carboxylic acid

Green and blue crystals of the coordination complexes [Cu(8‐hquin)₂(H₂O)₂], 1 and [Cu(pyzca)₂(H₂O)₂], 2 were obtained by the reaction of copper chloride with 8‐hydroxyquinoline (8‐hquinH) or pyrazine‐2‐carboxylic acid (pyzcaH) as ligands. The structures of 1 and 2 were characterized by elemental analyses, electronic absorption, Infrared (IR) and thermal studies. The luminescent behavior complexes 1 and 2 was also discussed. The coordination environment of copper(II) center displays distorted octahedral coordination geometry. The structure of the complexes 1 and 2 is constructed by an infinite number of discrete mononuclear molecules extending along the a‐axis to form a 1D‐chain via H‐bonds. The extensive hydrogen bonds and short contacts develop the structures of 1 and 2 to 3D‐network. The catalytic behavior of the complexes 1 and 2 was utilized for degradation of methylene blue dye (MB). The kinetic data indicated that the complexes 1 and 2 are effective catalysts for degradation of MB dye. Photoluminescence probing technology was used as a sensitive probe for detecting ^?OH radicals.     

Synthesis,structural characterization and in vitro cytotoxicity of diorganotin complexes with Schiff base ligands derived from 3‐hydroxy‐2‐naphthoylhydrazide

A series of diorganotin complexes with Schiff base ligands, (E)‐N′‐(5‐bromo‐2‐hydroxybenzylidene)‐3‐hydroxy‐2‐naphthohydrazide, H₂L1, and (E)‐N′‐(5‐chloro‐2‐hydroxybenzylidene)‐3‐hydroxy‐2‐naphthohydrazide, H₂L2, were synthesized and characterized by elemental analysis, IR, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy. The molecular structures of the complexes, [(5‐bromo‐2‐oxidobenzylidene)‐3‐hydroxy‐2‐naphthohydrazidato]di(o‐chlorobenzyl)tin(IV) 6 and [(5‐chloro‐2‐oxidobenzylidene)‐3‐hydroxy‐2‐naphthohydrazidato]dibutyltin(IV) 9, were determined through single‐crystal X‐ray diffraction and revealed a distorted trigonal‐bipyramidal configuration. The in vitro cytotoxic activity of the Schiff bases and their diorganotin complexes was also evaluated against several human carcinoma cell lines, namely HT29 (human colon carcinoma cell line), SKOV‐3 (human ovarian cancer cell line), MCF7 (hormone‐dependent breast carcinoma cell line) and MRC5 (non‐cancer human fibroblast cell line). [(5‐Bromo‐2‐oxidobenzylidene)‐3‐hydroxy‐2‐naphthohydrazidato]dibutyltin(IV) 2 and [(5‐bromo‐2‐oxidobenzylidene)‐3‐hydroxy‐2‐naphthohydrazidato]dibenzyltin(IV) 5 were the most active diorganotin complexes of H₂L1 ligand. Among the diorganotin complexes of H₂L2 ligand, [(5‐chloro‐2‐oxidobenzylidene)‐3‐hydroxy‐2‐naphthohydrazidato]dicyclohexyltin(IV) 11 showed good cytotoxic activity against all the tested cell lines. As such, the above compounds can be considered agents with potential anticancer activities, and can therefore be investigated further in in vitro or in vivo anticancer studies. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis,characterization, electronic structure,and non‐linear optical properties (NLO) of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes with 5‐phenylazo‐8‐hydroxyquinoline using DFT approach

5‐phenylazo‐8‐hydroxyquinoline and its newly metal complexes with Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) metal ions have been prepared and characterized using different analytical techniques. The complexes are distorted octahedral binding via one oxygen and nitrogen atoms of the ligand; two/three coordinated water molecules. 1:1 complexes contain one chloride or OH⁻ ion and some complexes have one or two water of hydration whereas 1:2 complexes contain only two coordinated water molecules in their coordination spheres. All complexes behave as neutral in dimethylformamide (DMF). The electronic structure and non‐linear optical parameters NLO of the complexes (ML and ML2) are investigated theoretically at the B3LYP/GEN level of theory. The geometries of the studied complexes are non‐planner. The calculated E_HOMO and E_LUMO energies of the studied complexes were used to calculate the global properties; hardness (η), global softness (S) and electronegativity (χ). The total dipole moment (μ_tot), static total and anisotropy of polarizability (α, Δα) and static first hyperpolarizability (β) values were calculated and compared with urea as a reference compound. The studied complexes show promising optical properties.     

Synthesis and antimicrobial activities of sulfonohydrazide‐substituted 8‐hydroxyquinoline derivative and its oxinates

Looking at the pharmacological importance of 8‐hydroxyquinolines and sulfonamides, in the present study, a novel bi‐dentate ligand 4‐amino‐N′‐[(8‐hydroxyquinoline‐5‐yl)methyl] benzenesulfonohydrazide (AHQMBSH) having above both moieties within a single molecular framework was synthesized by the reaction of N‐acetamidobenzene sulfonohydrazide with 5‐chloromethyl‐8‐hydroxyquinoline hydrochloride. Its metal(II) oxinates were also prepared with Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) salts. All the above compounds were investigated by physicochemical analyses, thermogravimetric analysis and spectroscopic techniques. Antimicrobial activities for the above prepared compounds were carried out using the agar‐plate method against various strains of bacteria (Staphylococcus aureus, Bacillus subtillis, Pseudomonas aerugionsa, Escherichia coli) and fungi (Aspergillus niger and Aspergillus flavous). The results show a significant increase in antimicrobial and antifungal activities of AHQMBSH compared with the parent 8‐hydroxyquinoline and sulfonamides. Copyright © 2010 John Wiley & Sons, Ltd.     

Coordination modes of multidentate azodye ligand derived from 4,4′‐methylenedianiline towards some transition metal ions: Synthesis,spectral characterization,thermal investigation and biological activity

Nine new azodye metal complexes of Mn(II), Co(II), Ni(II), Cu(II), Cr(III), Fe(III), Ru(III), Hf(IV) and Zr(IV) ions have been prepared via the reaction of 5,5′‐((1E,1′E)‐(methylenebis(1,4‐phenylene))bis(diazene‐2,1‐diyl))bis(6‐hydroxy‐2‐thioxo‐2,3‐dihydropyrimidin‐4(5H)‐one) (H₄L) with the corresponding metal salts affording sandwich (1 L:1 M), mononuclear (2 L:1 M), binuclear (1 L,2 M) and tetranuclear (1 L,4 M) complexes. Elemental analyses, spectral methods, magnetic moment measurements and thermal studies were utilized to confirm the mode of bonding and geometrical structure for the ligand and its metal complexes. Infrared spectral data show that the H₄L ligand chelates with some metal ions in keto–enol–thione or keto–thione manner. It behaves in a neutral/dibasic tetradentate fashion in sandwich and binuclear complexes. Also, it acts as a neutral bidentate moiety in the Cr(III) complex. The spectra reveal that azo group participates in chelation in all complexes. Octahedral geometry was suggested for all chelates but the Cu(II) complex with square planar geometry. The thermal stability and decomposition of the compounds were studied, the data showing that the thermal decomposition ended with metal or metal oxide mixed with carbon as final product. The electron spin resonance spectrum of the Cu(II) complex demonstrates that the free electron is located in the ( ) orbital. Measurements of biological activity against human cell lines Hep‐G₂ and MCF‐7 reveal that the Cu(II) complex has a higher cytotoxicity in comparison to the free ligand and other metal complexes, with IC₅₀ values of 6.10 and 5.2 μg ml^?1, respectively, while the ligand has anti‐tumour activity relative to some of the investigated metal complexes.     

Synthesis,characterization and biological studies of alkenyl‐substituted titanocene(IV) carboxylate complexes

The carboxylate compounds [Ti(η⁵‐C₅H₅)(η⁵‐C₅H₄{CMe₂(CH₂CH₂CH?CH₂)})(O₂CCH₂SXyl)₂] (2; Xyl = 3,5‐Me₂C₆H₃) and [Ti(η⁵‐C₅H₅)(η⁵‐C₅H₄{CMe₂(CH₂CH₂CH?CH₂)})(O₂CCH₂SMesl)₂] (3; Mes 1 = 2,4,6‐Me₃C₆H₂) were synthesized by the reaction of [Ti(η⁵‐C₅H₅)(η⁵‐C₅H₄{CMe₂(CH₂CH₂CH?CH₂)})Cl₂] (1) with 2 equivalents of xylylthioacetic acid or mesitylthioacetic acid, respectively. Compounds 2 and 3 were characterized by spectroscopic methods. The cytotoxic activity of 1–3 was tested against human tumor cell lines from four different histogenic origins—8505C (anaplastic thyroid cancer), DLD‐1 (colon cancer) and the cisplatin sensitive A253 (head and neck cancer) and A549 (lung carcinoma)—and compared with those of the reference complex [Ti(η⁵‐C₅H₅)₂Cl₂] (R1) and cisplatin. Surprisingly, the cytotoxic activities of the carboxylate derivatives were lower than those of their corresponding dichloride analogue (1). However, complexes 1–3 were more active than titanocene dichloride against all the studied cells with the exception of complex 2 against A253 and A549 cell lines. DNA‐interaction tests were also carried out. Solutions of all the studied complexes were treated with different concentrations of fish sperm DNA, observing modifications of the UV spectra with intrinsic binding constants of 2.99 × 10⁵, 2.45 × 10⁵, and 2.35 × 10⁵ M ^?1 for 1–3. Structural studies based on density functional theory calculations of 2 and 3 were also carried out. Copyright © 2010 John Wiley & Sons, Ltd.     

New diorganotin(IV) complexes of Schiff base derived from 4‐amino‐3‐hydrazino‐5‐mercapto‐4H‐1,2,4‐triazole: Synthesis,structural characterization,density functional theory studies,atoms‐in‐molecules analysis and antifungal activity

New diorganotin(IV) complexes of a Schiff base (HL) having general formula R₂Sn(L)Cl (where L is the monoanion of HL and R = n‐Bu or Ph) have been synthesized and characterized using elemental analysis, infrared, NMR (¹H, ¹³C, ¹¹⁹Sn) and UV–visible spectroscopies and mass spectrometry. These investigations suggest that in these 1:1 monomeric derivatives the Schiff base ligand acts in a monoanionic bidentate manner coordinating through the O_phenolic and N_azomethine, with proposed distorted trigonal bipyramidal geometry around tin with O_phenolic and two organic groups in the equatorial plane and the N_azomethine and the third organic group in axial positions. The proposed structures have been validated by density functional theory (DFT)‐based quantum chemical calculations at the B3LYP/6‐31G(d,p)/Def2‐SVP (Sn) level of theory. The simulated UV–visible spectrum was obtained with the time‐dependent DFT method in the gas phase and in the solvent field with the integral equation formalism–polarizable continuum model. A comparative analysis of the experimental vibrational frequencies and simulated harmonic frequencies indicates a good correlation between them. An insight into the intramolecular bonding and interactions among bonds in organotin(IV) complexes of HL was obtained by means of natural bond orbital analysis. The topological and energetic properties of the electron density distribution for the tin–ligand interaction in R₂Sn(L)Cl have been theoretically calculated at the bonds around the central tin atom in terms of atoms‐in‐molecules theory. The R₂Sn(L)Cl complexes were screened for their in vitro antifungal activity against chosen fungal strains.     

Heterocycles Derived from 5‐(2‐Aminothiazol‐4‐yl)‐8‐hydroxyquinoline: Synthesis and Antimicrobial Activity

5‐(2‐Aminothiazol‐4‐yl)‐8‐hydroxyquinoline 2 has been synthesized by treating thiourea with 5‐chloroacetyl‐8‐hydroxyquinoline 1 . The amine 2 was treated with aromatic aldehydes to furnish schiff bases 6a‐c which on treatment with phenyl isothiocyanate gave the corresponding thiazolo‐s‐triazines 7a‐c . Reaction of 2 with phenyl isothiocyanate gave the corresponding aminocarbothiamide derivative 8 which on reaction with malonic acid in acetyl chloride afforded thiobarbituric acid derivative 9 . Coupling of 9 with diazonium salt gave the phenyl hydrazono derivative 10 . However, reaction of 2 with carbon disulphide and methyl iodide afforded dithiocarbamidate 12 which on treatment with ethylenediamine, o‐aminophenol and/or phenylenediamine gave the aminoazolo derivatives 13–15 , respectively. Other substituted fused thiazolopyrimidines 16–20 have been also prepared by the reaction of 2 with some selected dicarbonyl reagents. The characterisation of synthesized compounds has been done on the basis of elemental analysis, IR, ¹H‐NMR and mass spectral data. All the newly synthesized compounds have been screened for their antimicrobial activities.     

Synthesis,characterization and assessment of the cytotoxic activity of Cu(II), Fe(III) and Mn(III) complexes of camphoric acid‐derived salen ligands

Novel Cu(II), Fe(III) and Mn(III) salen‐type metal complexes from (1R,3S)‐N,N′‐bis[salicylidene]‐1,3‐diamino‐1,2,2‐trimethylcyclopentane were synthesized and screened for their in vitro cytotoxic activity against three human cancer cell lines: melanoma, colorectal and breast. In vitro experiments carried out with the three metal complexes show that the copper complex exhibits the highest cytotoxic activity towards all cell lines studied, presenting IC₅₀ values of 3.32–6.71 μM. A significant improvement in the anti‐proliferative effect, by 20‐fold, is observed with this complex when compared with conventional chemotherapy. The relationship between structure, redox characteristics and biological activity in human cancer cell lines was evaluated for the most efficient Cu(II) complex and associated with theoretical calculations. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis,structural characterization,density functional theory calculations and biological evaluation of a new organotin(IV) complex containing N‐isonicotinyl‐N',N″‐diaryl phosphorictriamide as N‐donor ligand

A new diorganotin(IV) complex with the formula SnCl₂(CH₃)₂L₂ ( C_1a ), L = 4‐NC₅H₄CONHPO(NCH₃CH₂C₆H₅)₂, was synthesized and characterized using ¹H NMR, ¹³C NMR, ³¹P NMR, ¹¹⁹Sn NMR and infrared spectroscopies. The molecular structure of C_1a was determined using X‐ray crystallography, revealing that C_1a contains hexa‐coordinated Sn(IV) centres with trans‐configuration of donor atoms around them. Each Sn(IV) atom is positioned in the centre of inversion of an octahedron. C_1a forms one‐dimensional chains via two equal intermolecular P?O…H? N hydrogen bonds. These hydrogen bonds produce centrosymmetric rings as a supramolecular hydrogen‐bonded pattern. In order to compare the relative stability of C_1a (with N‐ligated configuration) and its possible O‐ligated isomer, C_1b , density functional theory calculations were performed, the results showing a preference of C_1a over C_1b from an energy point of view. Also, natural bond orbital analysis was carried out to obtain detailed information on the electronic features of the optimized structures. The theoretical results show that intermolecular hydrogen bonding in the crystal structure has a significant role in the stabilization of C_1a , and Sn(IV) interacts more strongly with the N_py atom than the P?O functional group. Furthermore, the free ligand and its complex were tested against three human cancer cell lines, i.e. human cervical carcinoma (HeLa), human prostate cancer (PC‐3) and human breast adenocarcinoma cancer (MCF‐7). C_1a displays moderate to good cytotoxicity towards all three cancer cell lines. Moreover, antibacterial tests were carried out using the disc‐diffusion method, in which C_1a shows high activity against selected Gram‐negative and Gram‐positive bacteria. Copyright © 2015 John Wiley & Sons, Ltd.     

Some divalent metal(II) complexes of salicylaldehyde‐derived Schiff bases: Synthesis,spectroscopic characterization,antimicrobial and in vitro anticancer studies

Mononuclear transition metal(II) complexes of the type M(L)₂?2H₂O (where M = Co, Ni, Cu, Zn) have been synthesized from uninegative Schiff base ligands (HL₁–HL₄) designed by condensation of 4‐fluorobenzylamine with 2‐hydroxy‐1‐naphthaldehyde/3,5‐dichlorosalicylaldehyde/3,5‐dibromosalicylaldehyde/3‐bromo‐5‐chlorosalicylaldehyde. The compounds were successfully characterized using spectroscopic and physiochemical methods together with elemental analysis. Spectroscopic elucidation indicates a monobasic bidentate nature of ligands coordinated via deprotonated phenolic oxygen and azomethine nitrogen atom which suggests an octahedral geometry around the central metal ions. The complexes and ligands were screened for their in vitro antimicrobial activity against bacterial and fungal strains, the zinc(II) complexes being more active against the tested microbial strains. Further, the metal complexes were found to be more active than the uncomplexed ligands due to chelation process and, moreover, the complexes were more active against fungal strains than bacterial strains. Cytotoxic activities of all compounds were evaluated towards human alveolar adenocarcinoma epithelial cell line (A549), human breast adenocarcinoma cell line (MCF7), human prostate cancer cell line (DU145) and one normal human lung cell line (MRC‐5) using MTT colorimetric assay with doxorubicin as a standard. The zinc complexes were most active against the cancer cell lines and also found to be less toxic against MRC‐5 normal cell line than standard doxorubicin.     

DFT computational studies on rotation barriers,tautomerism, intramolecular hydrogen bond,and solvent effects in 8‐hydroxyquinoline

Intramolecular hydrogen binding interactions in 8‐hydroxyquinoline, both in its zwitterionic tautomer and in the rotamer without the intramolecular hydrogen bond (IHB), have been computed using the B3LYP and MPW1K density functionals. The rotation of the O? H bond and intramolecular proton transfer reactions were studied theoretically. The following theory levels have been applied: B3LYP/6‐31G(d,p), B3LYP/6‐311++G(d,p), MPW1K/6‐311++G(d,p), and MPW1K/6‐311++G(2d,3p)//MPW1K/6‐311++G(d,p). Natural bond orbital (NBO) analysis has also been carried out. The effect of medium (benzene, chloroform, tetrahydrofuran, 1,2‐dichloroethane, acetone, water) was simulated using the self‐consistent reaction field (SCRF) method within the framework of the polarizable continuum model (PCM), at the MPW1K/6‐311++G(d,p) level. The evolution of geometry, relative energies, heights of rotation (around the O? H bond) and tautomerization barriers, IHB energies, and ΔG(solv) have been systematically investigated. The results obtained have shown the failure to neglect some changes of the above characteristics in polar media with respect to the gaseous phase. The series of stability of the forms under study in the gaseous phase remains the same in solution. Thus, in spite of the important role of the solvent electrostatic effects, the intrinsic stability of those species overcomes the solvent effects. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Synthesis and characterization of water‐soluble copper(II), cobalt(II) and zinc(II) complexes derived from 8‐hydroxyquinoline‐5‐sulphonic acid: DNA binding and cleavage studies

Three water‐soluble complexes, [Cu₂L₂Cl₂] ( 1 ), [CoL₂(im)₂] ( 2 ) and [ZnLClH₂O] ( 3 ) (HL = 8‐hydroxyquinoline‐5‐sulphonic acid; im = N ‐methylimidazole), were prepared and characterized using various spectral techniques. The DNA binding behaviour of complexes 1 – 3 was studied using UV–visible and circular dichroism (CD) spectra and cyclic voltammetry. All three complexes exhibit hypochromism but complexes 1 and 3 alone give a red shift of 4 nm with a significant binding constant of K _b = 2.1 × 10⁴ and 1.0 × 10⁴ M⁻¹, respectively, but complex 2 shows no red shift with lower K _b of 4.1 × 10³ M⁻¹. The voltammetric E _1/2 of complex 1 on interaction with herring sperm DNA shifts to a more positive potential, as expected, than complex 2 due to higher DNA affinity. Additionally, analysis of electrochemical data yields a value of K ₊/K ₂₊ greater than one suggesting that complex 1 binds to DNA through intercalation in the M(I) state. Evidently in CD spectral analysis, complex 1 exhibits a decrease in molar ellipticity with a red shift of 10 nm and a significant decrease in intensity compared to complexes 2 and 3 . This clearly indicates that complex 1 induces the B → A transition to a greater extent than 2 and 3 . Oxidative cleavage using circular plasmid pUC18 DNA with complex 1 was investigated using gel electrophoresis. Interestingly, complex 1 displays a strong DNA binding affinity and is efficient in cleaving DNA in the presence of H₂O₂ at pH = 8.0 at 37 °C.     

Synthesis,characterization, spectroscopic and theoretical studies of transition metal complexes of new nano Schiff base derived from l‐histidine and 2‐acetylferrocene and evaluation of biological and anticancer activities

A new Schiff base derived from the condensation of 2‐acetylferrocene with l ‐histidine was prepared and characterized using elemental analyses and spectroscopic methods. Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes of the Schiff base were prepared and characterized using various physicochemical methods such as elemental analysis, Fourier transform infrared and UV–visible spectroscopies, molar conductance, thermal analysis and scanning electron microscopy (SEM). Both ligand and complexes were investigated for their biological and anticancer activities. The elemental analyses showed that complexes were formed in a metal‐to‐ligand ratio of 1:1 stoichiometry. The spectral analyses proved that the ligand was tridentate and all complexes had an octahedral geometry, except the Zn(II) complex that was tetrahedral. SEM showed that the ligand and its Cd(II) complex were of nanometric structure. The molecular and electronic structure of the free ligand was optimized theoretically and the quantum chemical parameters were calculated. The molecular structure can be used to investigate the coordination sites and the total charge density around each atom. According to anticancer studies, Cd(II) complex was recommended to be used as anti‐breast cancer drug as it had very low IC₅₀ (3.5 μg ml^?1). Molecular docking was used to predict the binding between the free ligand and its Cd(II) complex and crystal structure of Staphylococcus aureus (PDB ID: 3Q8u), receptors of breast cancer mutant oxidoreductase (PDB ID: 3Hb5) and crystal structure of Escherichia coli (PDB ID: 3 T88) and to identify the binding mode and the crucial functional groups interacting with the three proteins.