Novel copper(II) heterochelate: synthesis,structural features and fluorescence studies

Fluorescence properties of four based derivatives [Aⁿ] (where n = 1–4) and their Cu(II) heterochelates of the type [Cu(Aⁿ)(CQ)(OH)]^?xH₂O {where A¹ = 3‐(2‐oxo‐2H‐chromen‐3‐yl)‐4H‐furo[3,2‐c]chromen‐4‐one, A² = 8‐methyl‐3‐(2‐oxo‐2H‐chromen‐3‐yl)‐4H‐furo[3,2‐c]chromen‐4‐one, A³ = 6‐methyl‐3‐(2‐oxo‐2H‐chromen‐3‐yl)‐4H‐furo[3,2‐c]chromen‐4‐one, A⁴ = 8‐chloro‐3‐(2‐oxo‐2H‐chromen‐3‐yl)‐4H‐furo[3,2‐c]chromen‐4‐one and x = 3, 2, 4, 1} were studied at room temperature. The fluorescence spectra of heterochelates show red shift, which may be due to the chelation by the ligands to the metal ion. It enhances ligand ability to accept electrons and decreases the electron transition energy. The kinetic parameters such as order of reaction (n), energy of activation (E_a), entropy (ΔS^#), pre‐exponential factor (A), enthalpy (ΔH^#) and Gibbs free energy (ΔG^#) have been reported. The antimicrobial activity of Clioquinol and Cu(II) heterochelates have been determined and described. All the heterochelates showed a more effective antimicrobial activity than the free ligand. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and Antimicrobial Evaluation of Some New Spiroindolinone Derivatives

In an attempt to find a new class of antimicrobial agents, a series of spiroindolinone compounds containing pyridine, pyrimidine, benzopyrans, pyrido, naphtodiazepines, pyrazole, and isoxazole ring systems were prepared via the reaction of 3‐(2‐oxo‐2‐(3‐oxo‐3H‐benzo[f]chromen‐2‐yl)ethylidene)indolin‐2‐one ( 4 ) with an appropriate nucleophilic reagent. Newly synthesized compounds were characterized by elemental analysis and spectral data (IR, ¹H‐NMR, ¹³C‐NMR, and mass spectra). Representative compounds were tested and evaluated as antimicrobial agents.     

Synthesis,structural studies and antimicrobial evaluation of nickel (II) complexes of NNS tridentate thiosemicarbazone based ligands

Synthesis and characterization of three nickel complexes [NiCl(L¹)] 1 , [NiCl(L²)] 2 and [NiCl(L³)] 3 are described {HL¹ = 4‐(2,5‐dimethoxyphenyl)‐1‐((pyridin‐2‐yl)methylene)thiosemicarbazide, HL² = 4‐(3‐nitrophenyl)‐1‐((pyridin‐2‐yl)methylene)thiosemicarbazide and HL³ = 4‐(2,4‐dimethoxyphenyl)‐1‐((pyridin‐2‐yl)methylene)thiosemicarbazide} and among the tridentate ligands HL³ is reported for the first time. The structures of the complexes were assigned based on CHNS microanalysis, spectroscopic (IR & UV–Vis.) data and solution conductivity studies. The absence of any magnetism for the complexes proved their square planar geometry. Single crystals of complex 1 were grown and analyzed by XRD analysis which confirmed the complex planarity as each Ni atom connects to three (two nitrogen and one sulfur) atoms from the thiosemicarbazone ligand and an additional chlorine atom. Packing of the complex 1 in the crystal lattice was proved to stabilize via intermolecular hydrogen bonds. Antimicrobial activities of 1 – 3 were studied in vitro against fungal and bacterial species and, in several instances, the complexes possessed improved antibacterial behavior in comparison to chloramphenicol.     

Synthesis of N1‐substituted coumarino[4,3‐c] pyrazoles

3‐Acyl‐4‐hydroxy‐2‐oxo‐2H‐chromen derivatives 1a‐d were condensed with (7‐hydroxy‐2‐oxo‐2H‐chromen‐4‐yl)‐acetic acid hydrazide 2 , (4‐methyl‐2‐oxo‐2H‐chromen‐7‐yloxy)‐acetic acid hydrazide 3 , and (7‐hydrazinocarbonylmethoxy‐2‐oxo‐2H‐chromen‐4‐yl)‐acetic acid hydrazide 4 , to give corresponding 3‐alkyl‐1‐[2‐(7‐hydroxy‐2‐oxo‐2H‐chromeno‐4‐yl)‐acetyl]‐1H‐chromeno[4,3‐c]pyrazole‐4‐one 5a‐d , 3‐alkyl‐1‐[2‐(4‐methyl‐2‐oxo‐2H‐chromeno‐7‐yloxy)‐acetyl]‐1H‐chromeno[4,3‐c]pyrazole‐4‐one 6a‐d , and 1‐{4‐[(3‐alkyl‐1H‐chromeno[4,3‐c]pyrazole‐4‐one‐1‐yl)‐carbonylmethyl]‐2‐oxo‐2H‐chromen‐7‐yloxy‐acetyl}‐3‐alkyl‐1H‐chromeno[4,3‐c]pyrazole‐4‐one 7a‐d.     

Synthesis,Photophysical and Computational Study of Novel Coumarin‐based Organic Dyes

A series of novel coumarin pyrazoline moieties combined with tetrazoles, 3‐(1‐phenyl‐4‐(1H‐tetrazol‐5‐yl)‐1H‐pyrazol‐3‐yl)‐2H‐chromen‐2‐one , 6‐chloro‐3‐(1‐phenyl‐4‐(1H‐tetrazol‐5‐yl)‐1H‐pyrazol‐3‐yl)‐2H‐chromen‐2‐one , 6‐bromo‐3‐(1‐phenyl‐4‐(1H‐tetrazol‐5‐yl)‐1H‐pyrazol‐3‐yl)‐2H‐chromen‐2‐one and 6‐bromo‐3‐(1‐(4‐bromophenyl)‐4‐(1H‐tetrazol‐5‐yl)‐1H pyrazol‐3‐yl)‐2H‐chromen‐2‐one 7(a‐d), were designed and synthesized. Single crystal X‐ray diffraction and their interactions were studied by Hirshfeld surface analysis. Thermal stabilities and electrochemical properties of these compounds were examined from differential scanning calorimetry (DSC ), thermogravimetric (TGA ) and cyclic voltammetric (CV ) studies. Their spectroscopic properties were analyzed in various alcohols and general solvents by UV–Vis absorption, fluorescence and time‐resolved spectroscopy. In addition, the ground and excited state electronic properties were investigated using density functional theory (DFT ). The calculated highest occupied molecular orbital (HOMO ) and lowest unoccupied molecular orbital (LUMO ) and energy band gap (E _g ) values have revealed the effect of substitution of halogens. The substitution has equally affected the ground and excited states of 7(a‐d) compounds. The solvatochromism on absorption, fluorescence spectra and fluorescence lifetimes of these compounds was investigated. All these results showed the chromen‐2‐one of pyrazoline tetrazole derivatives could play an important role in photonic and electronic devices.     

Facile One‐Pot Synthesis of 3‐{2‐[5‐Hydroxy‐4‐(2‐hydroxy‐ethyl)‐3‐methyl‐pyrazol‐1‐yl]‐thiazol‐4‐yl}‐chromen‐2‐ones via a Three‐Component Reaction

Reaction of 3‐(2‐bromo‐acetyl)‐chromen‐2‐one with thiosemicarbazide and 2‐acetylbutyro lactone in anhydrous ethanol gave 3‐{2‐[5‐hydroxy‐4‐(2‐hydroxy‐ethyl)‐3‐methyl‐pyrazol‐1‐yl]‐thiazol‐4‐yl}‐chromen‐2‐one in good yields.     

Facile Synthesis of Novel 3‐(4‐phenylisothiazol‐5‐yl)‐2H‐chromen‐2‐one Derivatives as Potential Anticancer Agents

A series of 3‐(4‐phenylisothiazol‐5‐yl)‐2H‐chromen‐2‐one ( 6a – l ) derivatives has been efficiently synthesized by straightforward sequential reactions. Tandem Vilsmeier Hack reaction/cyclization/bromination/Suzuki cross‐coupling reactions were successfully applied to the preparation of title compounds in good‐to‐high yields. In the synthetic sequences, 3‐chloro‐3‐(2‐oxo‐2H‐chromen‐3‐yl)acrylaldehydes ( 2 ) were found to react with ammonium thiocyanate to yield the corresponding 3‐(isothiazol‐5‐yl)‐2H‐chromen‐2‐ones ( 3 ). These derivatives were brominated with N‐bromo succinamide to yield the corresponding regioselective 3‐(4‐bromoisothiazol‐5‐yl)‐2H‐chromen‐2‐one ( 4 ). Finally, compound 4 was treated with various phenyl/pyrazole/7H –pyrrolo[2,3‐d]pyrimidinyl boronic acids 5a – l in the presence of K₂CO₃ and Pd catalyst in dimethylformamide to yield the corresponding title derivatives 6a – l . All the synthesized compounds were characterized by analytical and spectral studies. All the final compounds were screened against different cancer cell lines (A549, PC3, SKOV3, and B16F10), and among these compounds, 6b , 6g , 6h , and 6l displayed moderate cytotoxic activity against the tested cell lines.     

Transition metal complexes of 1,2‐dihydroquinazolinone derivative,an emerging class of analgesic and anti‐inflammatory agents

A new 1,2‐dihydroquinazolinone, 2‐(2‐hydroxy‐phenyl)‐3‐[1‐(2‐oxo‐2H‐chromen‐3‐yl)‐ethylideneamino]‐2,3‐dihydro‐1H‐quinazolin‐4‐one (L) and its Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes have been prepared. These were characterized by elemental, spectral [UV–visible, IR, NMR (¹H, ¹³C and 2D heteronuclear correlation) and mass], conductance, magnetic susceptibility and thermal studies. The physicochemical data indicate that the ligand behaves as tridentate with ONO donor sequence towards the metal ions, and trigonal bipyramidal geometry was assigned for complexes. The ligand and its metal complexes were evaluated for their in vivo anti‐inflammatory and analgesic activity. The tested compounds have shown excellent activity, which are almost equipotent to the standard used in the study. Copyright © 2011 John Wiley & Sons, Ltd.     

A convenient one‐pot synthesis of new 3‐(4‐aryl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2‐yl)‐2H‐chromen‐2‐ones

Anhydrous zinc bromide catalysed reactions of arylidine‐3‐acetyl coumarins ( 1a‐c ) and 5,6‐benzoanalogs of arylidine 3‐acetyl coumarins ( 4a,4b ) with 1,3‐cyclohexanedione gives ‐(4‐aryl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2yl)‐2H‐chromen‐2‐ones ( 3a, 3c ) and 5,6‐benzoanalogs of 3‐(4‐aryl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2yl)‐2H‐chromen‐2‐one ( 5a,5b ). Under similar conditions arylidine‐3‐acetylcoumarins ( 1a, 1b,1d, 1e, 1f ) and 5,6‐benzoanalog of arylidine 3‐acetyl coumarin ( 4b ) react with 5,5‐dimethyl‐1,3‐cyclohexanedione (dimedone) yielding 3‐(4‐aryl‐7,7‐dimethyl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2‐yl)‐2H‐chromen‐2‐ones ( 3d‐3h ) and the 5,6‐benzoanalog of 3.(4‐aryl‐7,7‐dimethyl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2‐yl)‐2H‐chromen‐2‐one ( 5c ).     

Synthesis of new 3‐(4‐oxo‐4H‐chromen‐3‐yl)‐3a,6a‐dihydropyrrolo[3,4‐d]isoxazole‐4,6‐dione derivatives by 1,3‐dipolar cycloaddition reaction

A series of new 3‐(4‐oxo‐4H‐chromen‐3‐yl)‐3a,6a‐dihydropyrrolo[3,4‐d]isoxazole‐4,6‐dione have been synthesized by the reaction of N‐arylmaleimides with nitrile oxide, prepared from α‐chloro‐4‐oxo‐4H‐chromen‐carbaldehyde oximes in situ through 1,3‐dipolar cycloaddition reaction. The structures of all new compounds were confirmed by elemental analysis, ir,¹H nmr and mass spectral data.     

Synthesis,spectroscopy, thermal and biological aspect of novel six‐coordinated dimeric iron(III) mixed‐ligand complexes

The mixed‐ligand complexes of iron(III) with 1‐cyclopropyl‐6‐fluoro‐4‐oxo‐7‐piperazin‐1‐yl‐1,4‐dihydroquinoline‐3‐carboxylic acid and various neutral bidentate Schiff base ligands were prepared. The structure of mixed‐ligand complexes was investigated using spectral, physicochemical and elemental analyses. Biocidal activity was determined using agar plate technique against Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Salmonella typhi, Escherichia coli and Serratia marcescens . The result showed a significant increase in a biocidal activity compared with parent ligands, metal salts and standard drugs (ofloxacin, levofloxacin). DNA binding and cleavage studies were carried out using absorption titration and gel electrophoresis techniques, respectively. The binding constant of Fe(III) complexes was obtained in the range 2.5–4.0 × 10⁴ M ^?1. The DNA binding and cleavage efficacy were raised in mixed‐ligand complexes as compared with parental ligands and metal salts. Copyright © 2008 John Wiley & Sons, Ltd.     

Utilization of hydrogen bonds to stabilize M-O(H) units: synthesis and properties of monomeric iron and manganese complexes with terminal oxo and hydroxo ligands

Non-heme iron and manganese species with terminal oxo ligands are proposed to be key intermediates in a variety of biological and synthetic systems; however, the stabilization of these types of complexes has proven difficult because of the tendency to form oxo-bridged complexes. Described herein are the design, isolation, and properties for a series of mononuclear Fe(III) and Mn(III) complexes with terminal oxo or hydroxo ligands. Isolation of the complexes was facilitated by the tripodal ligand tris[(N'-tert-butylureaylato)-N-ethyl]aminato ([H(3)1](3-)), which creates a protective hydrogen bond cavity around the M(III)-O(H) units (M(III) = Fe and Mn). The M(III)-O(H) complexes are prepared by the activation of dioxygen and deprotonation of water. In addition, the M(III)-O(H) complexes can be synthesized using oxygen atom transfer reagents such as N-oxides and hydroxylamines. The [Fe(III)H(3)1(O)](2-) complex also can be made using sulfoxides. These findings support the proposal of a high valent M(IV)-oxo species as an intermediate during dioxygen cleavage. Isotopic labeling studies show that oxo ligands in the [M(III)H(3)1(O)](2-) complexes come directly from the cleavage of dioxygen: for [Fe(III)H(3)1(O)](2-) the nu(Fe-(16)O) = 671 cm(-1), which shifts 26 cm(-1) in [Fe(III)H(3)1((18)O)](2-) (nu(Fe-(18)O) = 645 cm(-1)); a nu(Mn-(16)O) = 700 cm(-1) was observed for [Mn(III)H(3)1((16)O)](2-), which shifts to 672 cm(-1) in the Mn-(18)O isotopomer. X-ray diffraction studies show that the Fe-O distance is 1.813(3) A in [Fe(III)H(3)1(O)](2-), while a longer bond is found in [Fe(III)H(3)1(OH)](-) (Fe-O at 1.926(2) A); a similar trend was found for the Mn(III)-O(H) complexes, where a Mn-O distance of 1.771(5) A is observed for [Mn(III)H(3)1(O)](2-) and 1.873(2) A for [Mn(III)H(3)1(OH)](-). Strong intramolecular hydrogen bonds between the urea NH groups of [H(3)1](3-) and the oxo and oxygen of the hydroxo ligand are observed in all the complexes. These findings, along with density functional theory calculations, indicate that a single sigma-bond exists between the M(III) centers and the oxo ligands, and additional interactions to the oxo ligands arise from intramolecular H-bonds, which illustrates that noncovalent interactions may replace pi-bonds in stabilizing oxometal complexes.     

Neutral gold complexes with tridentate SNS thiosemicarbazide ligands

Na[AuCl(4)]·2H(2)O reacts with tridentate thiosemicarbazide ligands, H(2)L1, derived from N-[N',N'-dialkylamino(thiocarbonyl)]benzimidoyl chloride and thiosemicarbazides under formation of air-stable, green [AuCl(L1)] complexes. The organic ligands coordinate in a planar SNS coordination mode. Small amounts of gold(I) complexes of the composition [AuCl(L3)] are formed as side-products, where L3 is an S-bonded 5-diethylamino-3-phenyl-1-thiocarbamoyl-1,2,4-triazole. The formation of the triazole L3 can be explained by the oxidation of H(2)L1 to an intermediate thiatriazine L2 by Au(3+), followed by a desulfurization reaction with ring contraction. The chloro ligands in the [AuCl(L1)] complexes can readily be replaced by other monoanionic ligands such as SCN(-) or CN(-) giving [Au(SCN)(L1)] or [Au(CN)(L1)] complexes. The complexes described in this paper represent the first examples of fully characterized neutral Gold(III) thiosemicarbazone complexes. All the [AuCl(L1)] compounds present a remarkable cell growth inhibition against human MCF-7 breast cancer cells. However, systematic variation of the alkyl groups in the N(4)-position of the thiosemicarbazone building blocks as well as the replacement of the chloride by thiocyanate ligands do not considerably influence the biological activity. On the other hand, the reduction of Au(III) to Au(I) leads to a considerable decrease of the cytotoxicity.     

Synthesis of [2‐aryl‐6‐oxo‐6H‐chromeno[6,7‐d]oxazol‐8‐yl]‐acetic acid ethyl esters

A number of coumarino[6,7‐d]oxazoles (nitrogen analogs of psoralens) have been synthesized from (7‐hydroxy‐2‐oxo‐2H‐chromen‐4‐yl) acetic acid ethyl ester 1 . The synthetic route began with the nitration of 1 with nitric acid in acetic acid to give (6‐nitro‐7‐hydroxy‐2‐oxo‐2H‐chromen‐4‐yl) acetic acid ethyl ester 2 ; (3,6‐dinitro‐7‐hydroxy‐2‐oxo‐2H‐chromen‐4‐yl) acetic acid ethyl ester 3 and (3,6,8‐trinitro‐7‐hydroxy‐2‐oxo‐2H‐chromen‐4‐yl) acetic acid ethyl ester 4 . The reduction of 2 was accomplished with tin(II) chloride, tin, and concentrated hydrochloric acid in ethanol giving (6‐amino‐7‐hydroxy‐2‐oxo‐2H‐chromen‐4‐yl) acetic acid ethyl ester 5 . After the condensation of aminocoumarin 5 with aromatic aldehyde in glacial acetic acid medium, followed the dehydrocyclization to coumarino[6,7‐d]oxazoles 7a‐k . The intermediate Schiff's bases 6a‐k have been obtained from 5 with aromatic aldehyde in ethanol. Antibacterial and antifungal activities of the compounds have been evaluated.     

Equatorial Ligand Perturbations Influence the Reactivity of Manganese(IV)‐Oxo Complexes

Manganese(IV)‐oxo complexes are often invoked as intermediates in Mn‐catalyzed C−H bond activation reactions. While many synthetic Mn^IV‐oxo species are mild oxidants, other members of this class can attack strong C−H bonds. The basis for these reactivity differences is not well understood. Here we describe a series of Mn^IV‐oxo complexes with N5 pentadentate ligands that modulate the equatorial ligand field of the Mn^IV center, as assessed by electronic absorption, electron paramagnetic resonance, and Mn K‐edge X‐ray absorption methods. Kinetic experiments show dramatic rate variations in hydrogen‐atom and oxygen‐atom transfer reactions, with faster rates corresponding to weaker equatorial ligand fields. For these Mn^IV‐oxo complexes, the rate enhancements are correlated with both 1) the energy of a low‐lying ⁴E excited state, which has been postulated to be involved in a two‐state reactivity model, and 2) the Mn^III/IV reduction potentials.     

Hantzsch reaction of 3‐(2‐bromoacetyl)‐4‐hydroxy‐chromen‐2‐one. Synthesis of 3‐(thiazol‐4‐yl)‐4‐hydroxy coumarines

3‐Acetyl‐4‐hydroxy‐chromen‐2‐one ( 1 ) was brominated with phenyltrimethylammonium tribromide to afford 3‐(2‐bromoacetyl)‐4‐hydroxy‐chromen‐2‐one ( 2 ) whose reactions with thiourea, thioacetamide and ammonium dithiocarbamate gave respectively 3‐(2‐amino‐thiazol‐4‐yl)‐4‐hydroxy‐, 4‐hydroxy‐3‐(2‐phenyl‐thiazol‐4‐yl)‐ and 4‐hydroxy‐3‐(2‐mercapto‐thiazol‐4‐yl)chromen‐2‐one. In a similar manner, com pound 2 was treated with four 1‐substituted‐2‐thioureas and thiobenzamide to give the corresponding 4‐hydroxy‐3‐(thiazol‐4‐yl)‐chromen‐2‐one derivatives.     

Synthesis and characterization of Ru(III), Rh(III), Pt(IV) and Ir(III) thiosemicarbazone complexes

Ru(III), Rh(III), Pt(IV) and Ir(III) complexes of 2-furfural thiosemicarbazone as ligand have been synthesised. These complexes have the composition [M(ligand)₂X₂]X (M = Ru(III) Rh(III) and Ir(III) X = Cl and Br) and [Pt(ligand)₂ X₂] X₂ (X = Cl, Br and 1/2SO₄). The deprotonated ligand forms the complexes of the formulae M(ligand-H)₃ and Pt(ligand-H)₃Cl. All these complexes have been characterized by elemental analysis, magnetic measurements, electronic and infrared spectral studies. All the complexes are six-coordinate octahedral.     

Vanadium(III) and vanadium(V) amine tris(phenolate) complexes

The coordination chemistry of amine tris(phenolate) ligands around V(III) and V(V) is described for the first time. Three amine tris(phenolate) ligands were employed featuring different steric and electronic influence exerted by the phenolate substituents in the ortho and para positions being either t-Bu, Me, or Cl. V(III) complexes of all ligands (1-3) were readily obtained by reaction between the ligand precursors and VCl3(THF)3 in the presence of triethylamine. The complexes obtained were pentacoordinate, a THF ligand completing the coordination sphere of the metal, which was found to be of almost perfect TBP geometry, as revealed by crystallography. V(V) oxo complexes of all the ligands (4-6) were readily obtained by a reaction between the ligand precursors and VO(OPr)3. The oxo complexes of the alkyl-bearing ligands (4 and 5) could also be synthesized by the air oxidation of the corresponding V(III) complexes (1 and 2); however, the attempted air oxidation of the V(III) complex bound to the electron-poor ligand (3) did not yield the corresponding oxo complex 6. 1H NMR and crystallographic analysis of complexes 4 and 5 supported their TBP structures. Complex 6, on the other hand, was found to be composed of a TBP complex (6a) and an octahedral complex (6b) in equilibrium, the octahedral complex being more stable at lower temperatures. An X-ray structure of 6b revealed a mononuclear oxo complex, the sixth coordination site being occupied by an aqua ligand to which two THF molecules are H-bonded. Complexes 4-6 catalyze the epoxidation of olefins by t-BuOOH, albeit slowly. These complexes may thus be considered as structural and functional models of vanadium-dependent haloperoxidase enzymes.     

Synthesis,Characterization, Antimicrobial Activities,and Structural Studies of Lanthanide (III) Complexes with 1-(4-Chlorophenyl)-3-(4-fluoro/hydroxyphenyl)prop-2-en-1-thiosemicarbazone

Twelve coordinate lanthanide (III) complexes with the general composition [Ln L₃X_n(H₂O)_n] where Ln = Pr(III), Sm(III), Eu (III), Gd (III), Tb (III), Dy (III), X = Cl^?1, NO₃ ^?2, n = 2–7, and L is 1-(4-chlorophenyl)-3-(4-fluoro/hydroxyphenyl)prop-2-en-1- thiosemicarbazone have been prepared. The lanthanide complexes (5) were derived from the reaction between 1-(4-chlorophenyl)-3-(4-fluoro/hydroxyphenyl)prop-2-en-1-thiosemicarbazone (4) with an aqueous solution of lanthanide salt. Chalcone thiosemicarbazone ligand (4) was prepared by the reaction of [1-(4-chlorophenyl)-3-(4-fluoro/hydroxyphenyl)]prop-2-enone (chalcone) (3) with thiosemicarbazide in the presence of hot ethanol. All the lanthanide-ligand 1:3 complexes have been isolated in the solid state, are stable in air, and characterized on the basis of their elemental and spectral data.

Thiosemicarbazone ligands behave as bidentate ligands by coordinating through the sulfur of the isocyanide group and nitrogen of the cyanide residue. The probable structure for all the lanthanide complexes is also proposed. The chalcone thiosemicarbazone ligands and their lanthanide complexes have been screened for their antifungal and antibacterial studies. Some of the synthesized lanthanide complexes have shown enhanced activity compared with that of the free ligand.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Nickel Complexes Bearing SNN and SS Donor Atom Ligands: Synthesis,Structural Characterization and Biological activity

Based on a tridentate thiosemicarbazone ligand {HL = 4‐(2,4‐dimethylphenyl)‐1‐((pyridin‐2‐yl)methylene)thiosemicarbazide}, the nickel complexes [NiCl(L)] 1 , [Ni(L)(diEtdtc)(H₂O)] 2 and [Ni(L)(pipdtc)(H₂O)] 3 were prepared {NadiEtdtc = sodium diethyldithiocarbamate and Napipdtc = sodium piperidine dithiocarbamate} and their structures were elucidated according to their elemental analyses, solution conductivities, magnetic moments and spectroscopic (IR and electronic) data. X‐ray single crystal studies have confirmed the structure of 1 as a square planar complex in which each nickel atom is linked to three (two nitrogen and one sulfur) atoms from the thiosemicarbazone ligand and a chlorine atom to ensure the complex neutrality. Moreover, the asymmetric unit cell of the complex was found to consist of two independent complex molecules of slightly different conformations (A&B). The complexes, especially the binary one, displayed high bactericidal activities that, in several instances, were comparable to or higher than those of the chloramphenicol standard.