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.     

Novel 3‐Hydroxy‐2‐naphthoic hydrazone and Ni(II), Co(II) and Cu(II) Complexes: Synthesis,Spectroscopic Characterization,Antimicrobial, DNA Cleavage and Computational Studies

A novel hydrazone ligand derived from condensation reaction of 3‐hydroxy‐2‐naphthoic hydrazide with dehydroacetic acid, and its Ni(II), Cu(II) and Co(II) complexes were synthesized, characterized by spectroscopic, elemental analyses, magnetic susceptibility and conductivity methods, and screened for antimicrobial, DNA binding and cleavage properties. Spectroscopic analysis and elemental analyses indicated the formula, [MLCl₂], for the complexes; square planar geometry for the nickel, and tetrahedral geometry for copper and cobalt complexes. The non‐electrolytic natures of the complexes in Dimethyl Sulphoxide (DMSO) were confirmed by their molar conductance values in the range of 6.11–14.01 Ω^?1cm²mol^?1. The copper complex had the best antibacterial activity against Staphylococcus aureus (ATCC 29213). DNA cleavage activities of the compounds, evaluated on pBR322 DNA, by agarose gel electrophoresis, in the presence and absence of oxidant (H₂O₂) and free radical scavenger (DMSO), indicated no activity for the ligand, and moderate activity for the complexes, with the copper complex cleaving pBR322 DNA more efficiently in the presence of H₂O₂. When the complexes were evaluated for antibacterial and A‐DNA activity using Molecular docking technique, the copper complex was found to be most effective against Gram‐positive (S. aureus) bacteria. [CuLCl₂] showed good hydrogen bonding interaction with the major‐groove (C₂^.G₁₃ base pair) of A‐DNA. Density functional theory (DFT) calculations of the structural and electronic properties of the complexes revealed that [CuLCl₂] had a smaller HOMO‐LUMO gap, suggesting a higher tendency to donate electrons to electron‐accepting species of biological targets.     

Synthesis,spectral, DFT calculations and antibacterial studies of Fe(III) complexes of new fluorescent Schiff bases derived from imidazo[4',5':3,4]benzo[1,2‐c]isoxazole

New fluorescent heterocyclic ligands were synthesized by the reaction of 8‐(4‐chlorophenyl)‐3‐alkyl‐3H‐imidazo[4',5':3,4]benzo [1,2‐c]isoxazol‐5‐amine with p‐hydroxybenzaldehyde and p‐chlorobenzaldehyde in good yields. The coordination ability of the ligands with Fe³⁺ ion was examined in an aqueous metanolic solution. Schiff base ligands and their metal complexes were characterized by elemental analyses, IR, UV–vis, mass, and NMR spectra. The optical properties of the compounds were investigated and the results showed that the fluorescence of all compounds is intense and their obtained emission quantum yields are around 0.15 – 0.53. Optimized geometries and assignment of the IR bands and NMR chemical shifts of the new complexes were also computed by using density functional theory (DFT) methods. The DFT‐calculated vibrational wavenumbers and NMR chemical shifts are in good agreement with the experimental values, confirming suitability of the optimized geometries for Fe(III) complexes. Also, the 3D‐distribution map for HOMO and LUMO of the compounds were obtained. The new compounds showed potent antibacterial activity and their antibacterial activity (MIC) against Gram‐positive and Gram‐negative bacterial species were also determined. Results of antibacterial test revealed that coordination of ligands to Fe(III) leads to improvement in the antibacterial activity.     

Reactivity of Dicoordinated Stannylones (Sn0) versus Stannylenes (SnII): An Investigation Using DFT‐Based Reactivity Indices

The reactivity of dicoordinated Sn⁰ compounds, stannylones, is probed using density functional theory (DFT)‐based reactivity indices and compared with the reactivity of dicoordinated Sn^II compounds, stannylenes. For the former compounds, the influence of different types of electron‐donating ligands, such as cyclic and acyclic carbenes, stannylenes and phosphines, on the reactivity of the central Sn atom is analyzed in detail. Sn⁰ compounds are found to be relatively soft systems with a high nucleophilicity, and the plots of the Fukui function f^? for an electrophilic attack consistently predict the highest reactivity on the Sn atom. Next, complexes of dicoordinated Sn compounds with different Lewis acids of variable hardness are computed. In a first part, the double‐base character of stannylones is demonstrated in interactions with the hardest Lewis acid H⁺. Both the first and second proton affinities (PAs) are high and are well correlated with the atomic charge on the Sn atom, probing its local hardness. These observations are also in line with electrostatic potential plots that demonstrate that the tin atom in Sn⁰ compounds bears a higher negative charge in comparison to Sn^II compounds. Stannylones and stannylenes can be distinguished from each other by the partial charges at Sn and by various reactivity indices. It also becomes clear that there is a smooth transition between the two classes of compounds. We furthermore demonstrate both from DFT‐based reactivity indices and from energy decomposition analysis, combined with natural orbitals for chemical valence (EDA‐NOCV), that the monocomplexed stannylones are still nucleophilic and as reactive towards a second Lewis acid as towards the first one. The dominating interaction is a strong σ‐type interaction from the Sn atom towards the Lewis acid. The interaction energy is higher for complexes with the cation Ag⁺ than with the non‐charged electrophiles BH₃, BF₃, and AlCl₃.     

Microwave‐assisted Synthesis,Characterization, and Density Functional Theory Study of Biologically Active Ferrocenyl Bis‐pyrazoline and Bis‐pyrimidine as Organometallic Macromolecules

Organometallic macromolecules such as ferrocenyl bis‐pyrazoline ( 2 , 3 ) and bis‐pyrimidine ( 4 , 5 ) derivatives were synthesized by reacting ferrocenyl bis‐chalcone 1 with thiosemicarbazide/phenylhydrazine/guanidine hydrochloride/thiourea, respectively, under microwave irradiation. Ferrocenyl bis‐chalcone 1 was synthesized by reacting acetyl ferrocene with terephthalaldehyde. Synthesized compounds were characterized by using IR, ¹H NMR, ¹³C NMR, EI‐MS, and elemental analysis. In vitro antibacterial activity against two Gram‐negative and two Gram‐positive bacteria was determined by the disc diffusion assay. Moreover, minimum inhibition concentrations were also measured with reference to chloramphenicol. Thioamide functionally containing ferrocenyl bis‐pyrazoline derivative 2 shows the best antibacterial activity on Escherichia coli and Salmonella typhimurium, among all tested compounds including the reference drug chloramphenicol. The structure–activity relationship is also developed by using computational calculations with density functional theory (DFT)/B3LYP method.     

X‐ray structures,spectroscopic, electrochemical,thermal, antibacterial,and DFT studies of two nickel(II) and cobalt(III) complexes constructed from a new quinazoline‐type ligand

Two two‐dimensional supramolecular Nickel(II) and Cobalt(III) complexes, [Ni( L ² )₂]·2CH₃OH ( 1 ) and [2Co( L ² )₂] ( 2 ) ( HL ²  = 1‐(2‐{[(E)‐3‐bromo‐5‐chloro‐2‐hydroxybenzylidene]amino}phenyl)ethanone oxime), were synthesized via complexation of salts acetate with HL ¹ (2‐(3‐bromo‐5‐chloro‐2‐hydroxyphenyl)‐4‐methyl‐1,2‐dihydroquinazoline 3‐oxide, H is the deprotonatable hydrogen). During the reaction, the C–N bond in HL ¹ is converted into the C=N–OH group in HL ² . The spectroscopic data of both complexes were compared with the ligand HL ¹ . HL ¹ and both complexes were determined by single‐crystal X‐ray crystallography. The differently geometric features of the obtained complexes 1 and 2 are observed. In the crystal structure, 1 and 2 form an infinite 1‐D chain‐like and 2‐D supramolecular frameworks. EPR spectroscopy of 2 was investigated. Moreover, electrochemical properties and antimicrobial activities of both complexes were also studied. In addition, the calculated HOMO and LUMO energies show the character of HL ¹ , complexes 1 and 2 . The electronic transitions and spectral features of HL ¹ and both complexes were discussed by TD‐DFT calculations.     

Syntheses, Supramolecular Structures and Antibacterial Activities of Five Helical Transition Complexes with 5-Chloro-1-phenyl-1H-pyrazole-3,4-dicarboxylic Acid

Five new transition metal complexes [Cu(HL)₂(H₂O)₂] ( 1 ), [Cu(HL)₂(phen)] ( 2 ), [Cu(HL)₂(H₂O)]₂(4,4′‐bipy) ( 3 ), [Zn(HL)₂(H₂O)₂]·(4,4′‐bipy) ( 4 ), [Ag(HL)(4,4′‐bipy)]_n ( 5 ), (H₂L=5‐chloro‐1‐phenyl‐1H‐pyrazole‐3,4‐dicarboxylic acid, phen=1,10‐phenanthroline; 4,4′‐bipy=4,4′‐bipyridine) have been synthesized and characterized. Complexes 1 , 2 and 4 exhibit monomeric structures, 3 shows a dinuclear structure, 5 displays 1D chain structure, and all extend to 3D supramolecular network via rich hydrogen bonds. Complexes 1 , 2 , 3 , 5 comprise single helical chains, while complex 4 generates quadruple‐stranded helical chains. Furthermore, the antibacterial activities of the titled complexes against bacterial species, three Gram positive bacteria (Staphylococcus aureus, Bacillus subtilis and Candida albicans) and two Gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa) were studied and compared to the activities of free ligands by using the microdilution method.     

Novel 13,14‐dimethyl‐5,8‐dioxa‐2,11,13,14‐tetraaza‐1,12‐diphosphabicyclo [10.1.1] tetradecane 1,12‐dioxide ligand and its Ni(II), Co(II), and Cu(II) complexes: Synthesis,characterization, antimicrobial,DNA cleavage,and computational studies

A novel diazadiphosphetidine ligand derived from the reaction of 2,4‐dichloro‐1,3‐dimethyl‐1,3,2,4‐diazadiphosphetidine‐2,4‐dioxide and 2,2′‐(ethane‐1,2‐diylbis[oxy])bis(ethan‐1‐amine) and its Ni(II), Cu(II), and Co(II) complexes have been synthesized, characterized by spectroscopic, elemental analyses, magnetic susceptibility, and conductivity methods, and screened for antimicrobial, DNA binding, and cleavage properties. Spectroscopic analysis and elemental analyses indicate the formula [M(H₂L)Cl₂] for the Cu(II), Co(II), Ni(II), and Zn(II) complexes and octahedral geometry for all the complexes. The non‐electrolytic nature of the complexes in dimethyl sulfoxide (DMSO) was confirmed by their molar conductance values, which are in the range 12.32–6.73 Ω^?1 cm² mol^?1. Computational studies have been carried out at the density functional theory (DFT)‐B3LYP/6‐31G(d) level of theory on the structural and spectroscopic properties of diazadiphosphetidine H₂L and its binuclear Cu(II), Co(II), Ni(II), and Zn(II) complexes. Six tautomers and geometrical isomers of the diazadiphosphetidine ligand were confirmed using semiempirical AM1 and DFT method from DMOL³ calculations. The copper complex had the best antibacterial activity against Staphylococcus aureus (ATCC 29213). DNA cleavage activities of the compounds, evaluated on pBR322 DNA by agarose gel electrophoresis in the presence and absence of an oxidant (H₂O₂) and a free‐radical scavenger (DMSO), indicated no activity for the ligand and moderate activity for the complexes, with the copper complex cleaving pBR322 DNA more efficiently in the presence of H₂O₂.     

Physicochemical characterization of nanobidentate ferrocene‐based Schiff base ligand and its coordination complexes: Antimicrobial,anticancer, density functional theory,and molecular operating environment studies

A novel bidentate Schiff base ligand (HL, Nanobidentate Ferrocene based Schiff base ligand L (has one replaceable proton H)) was prepared via the condensation of 2‐amino phenol with 2‐acetyl ferrocene. The ligand was characterized using elemental analysis, mass spectrometry, infrared (IR) spectroscopy, ¹proton nuclear magnetic resonance (H‐NMR) spectroscopy, scanning electron microscopy (SEM), and thermal analysis. The corresponding 1:1 metal complexes with some transition‐metal ions were additionally characterized by their elemental analysis, molar conductance, SEM, and thermogravimetric ana1ysis (TGA). The complexes had the general formula [M(L)(Cl)(H₂O)₃]xCl·nH₂O (M = Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II)), (x = 0 for Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II), x = 1 for Cr(III) and Fe(III)), (n = 1 for Cr(III), n = 3 for Mn(II) and Co(II), n = 4 for Fe(III), Ni(II), Cu(II), Zn(II), and Cd(II)). Density functional theory calculations on the HL ligand were also carried out in order to clarify molecular structures by the B31YP exchange‐correlation function. The results were subjected to molecular orbital diagram, highest occupied mo1ecu1ar orbital–lowest occupied molecular orbital, and molecular electrostatic potential calculations. The parent Schiff base and its eight metal complexes were assayed against four bacterial species (two Gram‐negative and two‐Gram positive) and four different antifungal species. The HL ligand was docked using molecular operating environment 2008 with crystal structures of oxidoreductase (1CX2), protein phosphatase of the fungus Candida albicans (5JPE), Gram(?) bacteria Escherichia coli (3T88), Gram(+) bacteria Staphylococcus aureus (3Q8U), and an androgen‐independent receptor of prostate cancer (1GS4). In order to assess cytotoxic nature of the prepared HL ligand and its complexes, the compounds were screened against the Michigan cancer foundation (MCF)‐7 breast cancer cell line, and the IC₅₀ values of compounds were calculated.     

Polymer complexes. LXX. Synthesis,spectroscopic studies,thermal properties and antimicrobial activity of metal(II) polymer complexes

The monomer 3‐allyl‐5‐(phenylazo)‐2‐thioxothiazolidine‐4‐one (HL) was prepared by the reaction of allyl rhodanine with aniline through diazo‐coupling reaction. Reaction of HL with Ni(II) or Co(II) salts gave polymer complexes ( 1 – 8 ) with general stoichiometries [M(HL)(Cl)₂(OH₂)₂]_n, [M(HL)(O₂SO₂)(OH₂)₂]_n, [M(L)(O₂NO)(H₂O)₂]_n and [M(L)(O₂CCH₃)(H₂O)₂]_n (where M = Ni(II) or Co(II)). The structures of the polymer complexes were identified using elemental analysis, infrared and electronic spectra, molar conductance, magnetic susceptibility, X‐ray diffraction and thermogravimetric analysis. The interaction between the polymer complexes and calf thymus DNA showed a hypochromism effect. HL and its polymer complexes were tested against bacterial and fungal species. Co(II) polymer complex 2 is the most effective against Klebsiella pneumoniae and is more active than penicillin. The results showed that Ni(II) polymer complex 5 is a good antibacterial agent against Staphylococcus aureus and Pseudomonas aeruginosa. Molecular docking was used to predict the binding between the monomer with the receptors of prostate cancer (PDB code: 2Q7L Hormone) and breast cancer (PDB code: 1JNX Gene regulation). Coats–Redfern and Horowitz–Metzger methods were applied for calculating the thermodynamic parameters of HL and its polymer complexes. The thermal activation energy of decomposition for HL is higher than that for the polymer complexes.     

Experimental and computational studies on a new mixed ligand oxido–rhenium(V) compound

A mixed ligand oxido–rhenium(V) complex, [ReOS₃(HL)]Cl.H₂O ( 1p Cl.H₂O), with 3‐thiopentane‐1,5‐dithiolato (S₃) as a tridentate ligand and imidazolidinethione (HL) as an ancillary monodentate sulfur donor co‐ligand, has been synthesized. 1p Cl.H₂O has been characterized by spectral analyses. The X‐ray crystal structure of 1p Cl.H₂O shows that the complex contains a distorted square‐pyramidal “ReOS₄” core. The structural parameters agree with our optimized structure of 1p ⁺. Subsequently, the optimized structure was used to calculate systematically the relative stabilities of a sequence of oxido–Re(V) and the analogous oxido–Tc(V) complexes just by varying the donor sites (N, S, and O) on the tridentate ligand moiety in 1p ⁺. Electrochemical studies on 1p Cl.H₂O show an oxidative rhenium(VI)/ rhenium(V) couple at 1.561 V versus Ag/AgCl under controlled linear diffusion situation. Vibrational frequencies, electronic structures, and redox potential of 1p ⁺ have been calculated theoretically employing density functional theory (DFT) or time‐dependent‐DFT methods. The experimental findings are in excellent agreement with the computed results. The calculated redox potentials of the investigated oxido–Re(V) complexes and their oxido–Tc(V) counterparts are shown to correlate linearly with their respective chemical potential values.     

Synthesis,physicochemical characterization,geometric structure and molecular docking of new biologically active ferrocene based Schiff base ligand with transition metal ions

Physicochemical studies were performed to study new ferrocene based Schiff base ligand (HL), (Z)‐(4‐(1‐((2‐carboxycyclohexa‐2,4‐dien‐1‐yl)imino)ethyl)[bis(η ⁵ cyclopenta‐1,3‐dien‐1 yl)]iron with some transition metal ions to form a series of ferrocenyl derivatives bearing transition metal complexes of the type [M(L)Cl(H₂O)₃] (M = Ni(II), Cu(II)), [M(L)Cl(H₂O)₃]nH₂O (M = Mn(II) (n = 1), Co(II) (n = 1), Zn(II) (n = 2) and Cd(II) (n = 3)) and [M(L)Cl(H₂O)₃]Cl.nH₂O (M = Cr(III) (n = 2) and Fe(III) (n = 1)). The new ligand and metal ion complexes have been prepared and characterized by IR, UV‐Vis, ¹H‐NMR, TG/DTA, elemental analysis and mass spectrometry. The TGA/DTG analysis revealed that the ferrocene precursors decompose spontaneously to form iron(II) oxide. The molecular and electronic structure of the ligand (HL) was optimized theoretically and the quantum chemical parameters were calculated. The molecular structure with a variety of functionalities can be used to investigate the coordination sites and the total charge density around each atom. DFT‐based molecular orbital energy calculations of the new ligand have been also studied. All of the complexes were screened against a panel of Gram (+) bacteria: Streptococcus pneumoniae and Bacillis subtilis , Gram (−) bacteria: Pseudomonas aeruginosa and Escherichia coli and panel of fungi: Aspergillus fumigatu , Syncephalastrum racemosum , Geotricum candidum and Candida albicans . Anticancer activity screening for the tested compounds using 4 different concentrations of HL ligand against human tumor cells of breast cancer cell line MCF‐7 were obtained. Molecular docking was used to predict the binding between HL ligand and human‐DNA‐Topo I complex (PDB ID: 1SC7), the receptors of breast cancer mutant oxidoreductase (PDB ID: 3HB5), crystal structure of Escherichia coli (PDB ID: 3T88), to identify the binding mode and the crucial functional groups interacting with the three proteins.     

Mononuclear diorganotin(IV) complexes with arylhydroxamates: syntheses,structures and assessment of in vitro cytotoxicity

Two series of diorganotin(IV) complexes with dihalogenobenzohydroxamate ligands (substituents = 2,4‐Cl₂, 2,4‐F₂, 3,4‐F₂, 2,5‐F₂, 2,6‐F₂), formulated as [R₂Sn(HL)₂] ( a ), and the arylhydroxamato/arylcarboxylato mixed‐ligand complexes [R₂Sn(HL)(L′)] ( b ), were prepared and characterized by FT‐IR, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopies, elemental analyses and melting point measurements. X‐ray diffraction analysis was also carried out for the complex [Me₂Sn{3,4‐F₂C₆H₃C(O)NHO}₂], 1a . These compounds exhibit in vitro cytotoxic activities towards human leukemic promyelocites HL‐60, BGC‐823, BEL‐7402 and KB cell lines which, in some cases, are identical to, or even higher than, that of cisplatin. The type, position and number of the X substituents in the phenyl ring play a role in the cytotoxic activity, and complex 8a , with its 2,6‐difluorobenzohydroxamato ligand, is highly active against all tumor cells. A tentative structure–activity relationship is also described. Copyright © 2007 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.     

Transition metal complexes of nano bidentate organometallic Schiff base: Preparation,structure characterization,biological activity,DFT and molecular docking studies

An organometallic NO‐bidentate Schiff base, (2‐(1‐((1‐carboxyethyl)imino)ethyl) cyclopenta‐2,4‐dien‐1‐yl)(cyclopenta‐2,4‐dien‐1‐yl) iron (HL) was synthesized by condensation of 2‐acetylferrocene with amino acid alanine. Then its octahedral Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II) and Cd (II) complexes were synthesized. All compounds were characterized on the basis of elemental analysis (C, H, N and M), molar conductivity, FT‐IR, UV–Vis, ¹H‐NMR, SEM, mass analysis and thermal studies. Furthermore, computational studies of HL ligand have been carried out by DFT/B3LYP method. HOMO and LUMO energy values, chemical hardness‐softness, electronegativity, electrophilic index and other parameters were calculated. SEM micrographs of HL ligand and its [Cd (HL)(H₂O)₂Cl₂].2H₂O complex, showed that they were prepared in nano‐structure forms with particle size 54 and 41 nm, respectively. Antifungal and antibacterial activities of HL ligand and its metal complexes have been screened in vitro against different species such as Aspergillus fumigatus, Candida albicans, Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Salmonella typhimurium. The synthesized compounds were evaluated for their anticancer activities against breast cancer cell line (MCF‐7) and normal melanocytes cell line (HFB‐4). It was found that [Co (HL)(H₂O)₂Cl₂].3H₂O complex had the lowest IC₅₀ value (10.9 μg/ml) and hence was the most active one. Finally, the optimized structures of the Schiff base and its Co (II) complex have been used to accomplish molecular docking studies with receptors of 3HB5, 3MIW, 5IBV and 4WM8 to determine the most preferred mode of interaction.     

Design and synthesis of novel thiourea metal complexes with controllable antibacterial properties

A new bidentate O,S donor thiourea ligand (L¹), namely N‐(2‐hydroxyethyl)‐N′‐2‐chlorobenzoylthiourea, and its oxazolidine derivative (L²) were synthesized. Derivative L² was used for the preparation of Ni(L²)₂ and Cu(L²)₂ complexes. The compounds were investigated using X‐ray crystallography and Fourier transform infrared, ¹H NMR and UV–visible spectroscopies. Single‐crystal X‐ray analysis showed strong hydrogen bonding interactions between carbonyl oxygen and N(10) ─ H in the L¹ ligand. In addition, the antibacterial activities of these compounds were evaluated against Gram‐positive and Gram‐negative bacteria, measured using the colony count method. The Cu(L²)₂ complex exhibited a significant antibacterial activity while the activity of the other compounds was much lower. Finally, the relationship between the structure and antibacterial properties of these compounds was investigated using highest occupied and lowest unoccupied molecular orbital energies calculated by density functional theory method based on the 6‐31G*/LANL2DZ basis set.     

Studies on syntheses,reactivity and antibacterial activity of nickel(II) complexes of some N-S donors

Summary Square-planar and octahedral complexes of some selected bidentate N-S donor (HL) ring-substituted 4-phenylthiosemicarbazides possessing antibacterial activity have been prepared and characterized. Transformation of the red square-planar [Ni(HL)₂]X₂ complexes to the corresponding blue [Ni(HL)₂(H₂O)₂]X₂ octahedral complexes have been studied. The reactivity of the red square-planar complexes towards various monodentate Lewis base (B) was also examined, and octahedral complexes of the type [Ni(L)₂B₂] and [Ni(HL)B₂]X₂ were characterized. Thein vitro antibacterial activity of several of the red and blue complexes is higher than that of the unbound donors.     

DNA/BSA binding interactions and VHPO mimicking potential of vanadium(IV) complexes: Synthesis,structural characterization and DFT studies

Vanadium(IV) Schiff base complexes (VOL¹‐VOL³) were synthesized and characterized by elemental analysis, various spectral methods and single crystal XRD studies. Structural analysis of VOL² reveals that the central vanadium ion in the complex is six coordinate with distorted octahedral geometry. Density functional theory (DFT) and time dependent (TD‐DFT) studies were used to understand the electronic transitions observed in the complexes in UV–Vis spectra. The electrochemical behavior of the complexes was investigated in acetonitrile medium exhibit quasi‐reversible one electron transfer. The DNA and BSA protein binding interaction of vanadium complexes has been explored by UV–Vis and fluorescence spectral methods and viscosity measurements reveal that the complexes interact with CT‐DNA through intercalation mode and follows the order VOL¹ < VOL³ < VOL². The complexes exhibit binding interactions with BSA protein. The complexes act as chemical nuclease and cleave DNA in the presence of H₂O₂. The 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay was used to evaluate the radical scavenging activity demonstrate the antioxidant property of the complexes. The antimicrobial activity was screened for several microorganisms, Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli. The mimicking of vanadium haloperoxidase was investigated by the bromination of the organic substrate phenol red by vanadium complexes in the presence of bromide and H₂O₂.