Synthesis, Characterization and Antibacterial Activity of New Ln(Ⅲ) Complex with Unsymmetrical Schiff Base Ligand

A new unsymmetrical Schiff base ligand (H_2LLi) was synthesized using L-lysine, o-vanillin and salicylaladyde. Three solid metal complexes of this ligand [Ln(H_2L)(NO_3)] NO_3·2H_2O (Ln=Sm, Ho, Tm) were prepared and characterized by elemental analyses, IR spectra, UV spectra, TG-DTG and molar conductance. The ligand synthesized are chelating agent. The nitrogen atoms of Schiff base, oxygen atoms of hydroxybenzene, methoxide and carboxyl are all coordinated to the metal ions. Carboxyl and the nitrate ion within the coordination sphere are coordinated to the metal ion in a mondentate or bidentate fashion. Water molecules are lied in crystal substances. The antibacterial activity of the ligand and its complexes was also studied. The antibacterial experiments indicate that they have antibacterial activity to E. coli, S. aureus, B. subtilis and the complexes have higher activity than the ligand.

Synthesis, Characterization and Antibacterial Activity of New Ln(Ⅲ) Complexes with an Unsymmetrical Schiff Base Ligand

A new unsymmetrical Schiff base ligand (H2LLi) was synthesized using L-lysine, salicylaldehyde and 2-hydroxy-1-naphthaldehyde. Three solid metal complexes of this ligand \[Ln(H2L)(NO3)\] NO3·2H2O (Ln=La, Sm, Ho) have been prepared and characterized by elemental analyses, IR spectra, UV spectra, TG-DTG and molar conductance. The antibacterial activities of the ligand and its complexes are also studied. The antibacterial experiments indicate that the ligand and its complexes possess antibacterial activity against Escherichia coli, Staphylococcus aureus and Bacillus subtilis and that the complexes have higher activity than those of the ligand.

Microwave Synthesis, Spectral, Thermal and Antimicrobial Studies of Some Ni(II) and Cu(II) Schiff Base Complexes

Schiff bases have been synthesized by condensing nicotinamide with methyl isobutyl ketone (MKN) and 2-hydroxy acetophenone (HAN). Metal complexes have been prepared by interacting these Schiff bases with metal ions viz. Ni(II), Cu(II) 1:2 (metal:ligand) ratio. These compounds have been synthesized by conventional as well as microwave methods and characterized by elemental analysis, FT-IR, UV-Vis, FAB-mass, ESR, molar conductance, and thermal analysis. FAB mass and thermal data show degradation pattern of the complexes. The complexes are colored and stable in air at room temperature. The structure of the ligands were elucidated by spectral studies which indicate the presence of two or three coordinating groups in ligands which may be oxygen atom of the phenolic -OH group, the nitrogen atom of the azomethine (C=N) group and the oxygen atom of the carbonyl group. The thermal behavior of metal complexes shows that the hydrated complexes loses water molecules of hydration in the first step;followed by decomposition of ligand molecules in the subsequent steps. The solid state electrical conductivity of the metal complexes has also been measured. Solid state electrical conductivity studies reflect semiconducting nature of the complexes. The Schiff bases and metal complexes show good activity against the Gram-positive bacteria;Staphylococcus aureus and Gram-negative bacteria;Escherichia coli and fungi Aspergillus nigerand Candida albicans. The antimicrobial results also indicate that the metal complexes are better antimicrobial agents as compared to the Schiff bases.

Synthesis, Structure Characterization, Antibacterial Activity and Fluorescence Studies of a Ni(Ⅱ) Compound with Schiff-base Ligand

We synthesized one novel Schiff-base ligand by modifying the aromatic aldehyde： H2L^1（H2L^1 = N,N？-bis（2-oxy-acetate-3-methoxyl）benzylpropylene（1,3-propane）diamine）. [Ni（C（23）H（24）N2O8）]·6H2O]（1） was prepared by the reaction between H2L^1 and NiCl2·6H2O in C2H5 OH. Compound 1 was structurally characterized by elemental analysis, IR, H NMR and single-crystal X-ray diffraction. 1 crystallizes in monoclinic system, space group P21/n with a = 1.3952（4）, b = 1.3746（9）, c = 1.6121（0） nm, β = 112.66（3）°, V = 2.8533（4） nm^3, Z = 4, Mr = 623.25 and Dc = 1.451 g·cm^（-3）. The Ni（Ⅱ） atom is hexa-coordinated to furnish a slightly distorted octahedral geometry. Lattice water molecules are found in 1, and the H-bonding intersections formed novel water clusters. The IR, antibacterial activity and luminescence of 1 are studied.

Synthesis, Structure and Antibacterial Activities of 4-BBTS Schiff Base and Its Complexes

4-Bromobenzaldehyde thiosemicarbazone Schiff base （4-BBTS） and its Cu（Ⅱ）, Zn（Ⅱ）, Co（Ⅱ） and Ni（Ⅱ） complexes were synthesized and characterized by elemental analysis, UV, IR, MS, ^1H NMR, and molar conductivity. Using disc diffusion method, the antibacterial activity tests were conducted. The results revealed that the ligand as well as all the complexes exhibits good antibacterial activities against E. Coli. and S. Aureus. Moreover, Cu（Ⅱ） complex shows the best antibacterial activity, which provides beneficial reference for studying the relationship between the structures and performances.

Synthesis, Characterization and Antibacterial Activities of Polydentate Schiff Bases, Based on Salicylaldehyde

Three Schiff bases L1, L2 and L3 were synthesized by condensing salicylaldehyde with 4-aminoantipyrine, ethylendiamine and 2-aminophenol respectively and subsequently characterized by various physicochemical investigations. All the three compounds were screened for their In-vitro antibacterial activity against two gram positive bacteria, Staphylococcus aureus (S.A), Staphylococcus epidermidis (S.E) and two gram negative bacteria Klebsiella pneumoniae (K.P) and Pseudomonas aeruginosa (P.A) by agar diffusion method. On comparing the results obtained with the activity of commercially available antibiotics such as Ciprofloxacin and Chloramphenicol, the newly synthesized compounds showed comparable antibacterial activities. The solvent methanol exhibit activity against all bacterial species with IZs ranging from 8 ± 0.25 to 17 ± 0.29 mm while the standard antibiotics Ciprofloxacin and Chloramphenicol exhibited an activities with IZs varying from 21.3 ± 0.31 to 28.3 ± 0.32 and 26.3 ± 0.24 mm to 32.3 ± 0.23 mm, respectively. However, the newly synthesized Schiff bases L1, L2 and L3 showed IZs ranging from 7.4 ± 0.23 to 32.5 ± 0.14, 3 ± 0.57 to 12 ± 0.28 and 10 ± 0.20 to 32 ± 0.36 respectively. Among the Schiff bases, L3 showed the activity (32 ± 0.36) against S.E and P.A which is higher than the activity of standard antibiotics Ciprofloxacin and Chloramphenicol against the same bacterial strains. The results obtained revealed that all the synthesized Schiff bases exhibit appreciable antibacterial activity against all the bacteria species which potentially makes them, to apply as wide range antibacterial drugs, after further in-vivo cytotoxicity investigations. Their activity can also be further modified by changing the functionality of precursors for Schiff base condensation.

Synthesis, Crystal Structure and Biological Activity of 4-Amino-2,4-dihydro-5-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-3H-1,2,4-triazole-3-thione Schiff Base

The target compound 1,2,4-triazole Schiff base containing pyrazole ring was synthesized by 4-amino-2,4-dihydro-5-（（3,5-dimethyl- lH-pyrazol-1-yl）methyl）-3H-1,2,4-triazole-3-thione and 3,4,5-trimethoxy benzaldehyde.The structure was confirmed by IR,~1H NMR,H RMS,elemental analysis and single-crystal X-ray diffraction.The crystal belongs to the triclinic system,space group P1 with a = 7.8772（17）,b = 8.2986（18）,c = 15.392（3） A,α= 93.360（4）,β= 94.609（4）,γ= 93.584（4）°,C（18）H（22）N6O3S,Mr= 402.47,V= 998.9（4） A^3,Z= 2,F（000） = 422,Dc =1.335 g/cm^3,μ= 0.194 mm^（-1）,the final R = 0.0533 and wR = 0.1329 for 3517 observed reflections with I 2σ（I）.The preliminary bioassay results indicate that the target compound has good fungicidal activity against Gibberlla nicotiancola in EC50 value and F.O.f.sp.niveum in EC（95） value.

Synthesis and antibacterial activity of Schiff bases of 5-substituted isatins

Based on the existing reports on the bioactive isatin derivatives, a number of Schiff bases were synthesized by reacting 5-substituted isatins with bioactive amines/hydrazides and their structures were confirmed using spectroscopic methods such as NMR, IR and mass spectrometry. Furthermore, Nbenzylation of isatin followed by the Schiff base formation furnished a new series of compounds（11a-13c） which allowed the analysis of the effect of isatin N-substitution on the bioactivity of the resulting compounds. The antibacterial activity of the synthesized derivatives was evaluated using a microtiter plate method on a series of gram positive and gram negative bacterial strains. Compounds 2d, 3b, 5c and 6a were among the most potent derivatives against Pseudomonas aeruginosa（MIC = 6.25 μg/m L）.Analysis of the structure-activity relationship showed that the incorporation of（thio）urea-based Schiff bases lead to more potent derivatives with a broader spectrum of antibacterial activity. In addition,highly lipophilic compounds such as 11a-12c did not show any measurable antibacterial activity, which implies that an optimal lipophilicity might be an important requirement for the antibacterial activity of the studied isatins. Finally, the finding that hydantoin derivatives of N-benzylisatins（13a-13c） still exhibit some antibacterial activity prompted us to consider exploring the bioactivity of more diverse derivatives of isatin-aminohydantoin Schiff bases（compounds 1a-1d） in our future studies.

Synthesis,spectral studies,thermal behavior,and antibacterial activity of Ni(Ⅱ),Cu(Ⅱ),and Zn(Ⅱ) complexes with an ONO tridentate Schiff base

Three new transition metal complexes have been synthesized with a Schiff base, 3-（2-hydroxy-5-chlorophenylimino）-1,3- diphenylpropen-l-one. In all complexes Schiff base is completely deprotonated and coordinated to metal as tridentate ligand via phenolic and enolic oxygens and imine nitrogen. Thermal decomposition of the complexes has been studied by thermogravimetry. The in vitro antibacterial activity of Schiff bases and their complexes has been evaluated and compared with the standard drugs.

Syntheses, Crystal Structures and Antibacterial Activities of Cobalt(Ⅱ) and Manganese(Ⅱ) Complexes with Schiff Base Ligand Derived from Tryptamine

Two new mononuclear complexes, namely [Co（L）2]（1） and [Mn（L）2]（2）（HL = N-（3-methylsalicylidene）tryptamine）, have been synthesized by the reactions of the ligand with cobalt acetate or manganese acetate in anhydrous ethanol. The crystal structures of the complexes were characterized by IR spectrum, elemental analysis, PXRD and single-crystal X-ray diffraction analysis. Complex 1 crystallizes in monoclinic, space group C2/c, with a = 23.146（2）, b = 9.4864（10）, c = 13.9261（15）A, β = 102.898（2）°, V = 2980.6（5） ？3, Z = 4, Dc = 1.367 g/cm3, F（000） = 1284 and μ = 0.616 mm^-1. Complex 2 crystallizes in monoclinic, space group P21/n, with a = 14.807（11）, b = 13.118（10）, c = 16.663（13） A, β = 111.237（14）°, V = 3017（4） A^3, Z = 4, Dc = 1.342 g/cm^3, F（000） = 1276 and μ = 0.477 mm-1. The units of complex 1 are linked by intermolecular N–H…π hydrogen bonds into infinite 1D chains, which are further extended into a 3D supramolecular structure by a series of π···π stacking interactions. The units of complex 2 are linked by intermolecular N–H…π hydrogen bonds and C–H…π hydrogen bonds into an infinite 3D supramolecular structure. Meanwhile, the antibacterial activities of the ligand and its complexes have been tested against four kinds of bacteria. The results show that the three compounds all have excellent antibacterial activities and that 1 and 2 possess stronger inhibiting effects against the bacteria than the Schiff base.

Synthesis,structural characterization and antibacterial activity of diorganotin(Ⅳ) complexes with ONO tridentate Schiff bases containing pyridine ring

Five organotin（IV） complexes, were obtained by reaction of SnR2C12 （R = Ph, Me, Bu） with ONO donor Schiff bases. The synthesized complexes have been investigated by elemental analysis and IR, 1H NMR, and ll9Sn NMR spectroscopy. These data show that the Schiff base acts as a tridentate dianionic ligand and coordinates via the imine nitrogen and two oxygen atoms. The X- ray crystallography of complex 4 shows a dimeric structure for this molecule. The in vitro antibacterial activities of the Schiff bases and their complexes have been evaluated against Gram-positive （Bacillus subtilis and Staphylococcus aureus） and Gram-negative （Escherichia coli and Pseudomonas aeruginosa） bacteria and compared with the standard antibacterial drugs.

Syntheses, Crystal Structures and Antibacterial Activities of Schiff Base Ligand and Its Nickel(Ⅱ) Complex

A complex [NIL2] was synthesized, in which L, or to be exact, a Schiff base ligand （HL）, was derived from the condensation of 1-phenyl-3-methyl-4-phenylacetyl-5-pyrazolone （PMPAP） with L-phenylalanine methyl ester. They were characterized by IR and single-crystal X-ray diffraction. Green block crystals of both ligand and its complex were grown at room temperature. The ligand, which consists of two individual fragments, crystalizes in the P1 space group （a = 5.6268（5）, b = 10.6892（11） and c = 19.4869（18） A）. The complex crystalizes in the P21 space group （a -- 21.4076（18）, b = 9.4792（8） and c = 25.287（2） A）, which consists of a nickel six-coordinated compound. Every fragment is a distorted octahedron with four oxygen and two nitrogen atoms. The Schiff base ligand （HL） and its complex have been tested in vitro to evaluate their antibacterial activity against bacteria Escherichia Coli and Bacillus subtilis. It is found that the complex has higher activity than the corresponding free Schiff base ligand （HL） against the same bacterial.

Syntheses, Characterizations, Crystal Structures and Antibacterial Activities of Two Zinc(II) Complexes with a Schiff Base Derived from o-Vanillin and p-Toluidine

Two new zinc（Ⅱ） complexes, [Zn2L2Ch].2[ZnL（CH3OH）Cl2] 1 and [ZnL2（NO3）2] 2, were synthesized by reacting ZnX2.nH2O （X = Cl^-, NO3^-） and a Schiff base ligand 2-[（4-methylphenylimino）methyl]-6-methoxyphenol （C15HIsNO2, L） which was obtained by the condensation of o-vanillin （2-hydroxy-3-methoxybenzaldehyde） with p-toluidine. Both 1 and 2 were characterized by single-crystal X-ray diffraction technique, elemental analysis, molar conductance, FT-IR, UV-Vis, IH-NMR spectra and thermogravimetrie analysis. The Schiff base ligand and its zinc（Ⅱ） complexes have been tested in vitro to evaluate their antibacterial activity against bacteria, viz., Escherichia Coli, Staphylococcus aureus and Bacillus Subtilis. The results show that these complexes have higher activity than the corresponding free Schiff base ligand against the same bacteria.

Syntheses, Crystal Structures and Antibacterial Activities of Two Heterocyclic Schiff Base Compounds

Two heterocyclic Schiff bases were synthesized via the condensation reactions of primary amines with carbonyl compounds. 2-[（4-pyridylmethylene）-amino] phenol （compound 1） was synthesized by the interaction of 4-pyridinecarboxaldehyde with o-aminophenol in ethanol solvent; N,N＇-bis（3-（furan-2-yl）allylidene）benzene-1,4-diamin （compound 2） was synthesized by the interaction of 3-（2-furyl）acrolein with p-phenylenediamine in ethanol medium. The compounds were characterized by elemental analysis, IR, MS and single-crystal X-ray diffraction. Compound 1 （C12H10N2O） crystallizes in the monoclinic system, space group P21/c with α = 7.0771（7）, b = 7.2820（7）, c = 19.849（2）, b = 96.3390（10）°, V = 1016.66（17） ？3, Z = 4, Mr = 198.22, Dc = 1.295 g/cm3, F（000） = 416, GOOF = 1.060, m = 0.085 mm-1, the final R = 0.0371 and wR = 0.0929 for 1497 observed reflections with I 〉 2σ（I）. Compound 2 （C20H16N2O2） crystallizes in the orthorhombic system, space group Fdd2 with α = 26.344（15）, b = 48.50（3）, c = 5.293（3）, V = 6764（7） ？3, Z = 16, Mr = 316.35, Dc = 1.243 g/cm3, F（000） = 2656, GOOF = 1.043, m = 0.081 mm-1, the final R = 0.0526 and wR = 0.1267 for 2059 observed reflections with I 〉 2σ（I）. 1 and 2 molecules are connected through hydrogen bonds to generate a 2D network and a 1D chain structure, respectively. The preliminary antibacterial activity results showed that the title compounds display excellent antibacterial activities to Escherichia coli, Staphylococcus aureus and Bacillus subtilis.

Synthesis, Crystal Structure and Antibacterial Activity of 4,4'-Hydrazine-1,2- diylidenebis(methanylylidene)bis(2-ethoxyphenol)

A new Schiff base compound, 4,4′-hydrazine-1,2-diylidenebis（methanylylidene）- bis（2- ethoxyphenol） （C18H20N2O4）, has been synthesized by the condensation of 3-ethoxy-4- hydroxybenzaldehyde and 80% hydrazine hydrate in an ethanol solution. The compound was characterized by 1H NMR, MS and single-crystal X-ray diffraction. The crystal belongs to the monoclinic system, space group P21/n with a = 5.2421（5）, b = 10.3700（8）, c = 14.9906（11）A, β = 97.6030（10）°, Z = 2, V= 807.73（12） A, Dc = 1.350 g/cm3, Mr = 328.36, λ（MoKa） = 0.71073 A,μ = 0.096 mm-1, F（000） = 348, R = 0.041 and wR = 0.0136. The two benzene rings are coplanar. The molecule adopts an E,E configuration about the central C=N functional bonds. A total of 3938 unique reflections were collected, of which 1440 with I 〉 2σ（I） were observed. A different type of intermolecular hydrogen bond, O-H…N, exists in the crystal. The title complex molecules are connected through hydrogen bonds to generate a two-dimensional network. The preliminary antibacterial activity results showed that the title compound exhibits antibacterial activity against Staphylococcus aureus.

Synthesis, Crystal Structure and Antibacterial Activity of Two Hydrazones Derived from 2-Fluorobenzhydrazide

Two new Schiff base benzoyl hydrazone compounds, C14H10FN3O3 （Ⅰ） and C14H10F2N2O （Ⅱ）, have been synthesized and characterized by elemental analysis, IR, UV and X-ray single-crystal diffraction. Both compounds crystallize in monoclinic, space group P21/c with a = 7.0514（14）, b = 25.928（5）, c = 7.7099（15）, β = 111.823（2）°, V = 1308.6（4）3, Z = 4, C14H10FN3O3, Mr = 287.25, Dc = 1.458 g/cm3, μ（MoKα） = 0.115 mm-1, F（000） = 592, the final R = 0.0841 and wR = 0.2489 for 1901 observed reflections （I 2σ（I）） for I; a = 11.232（3）, b =12.735（4）, c = 8.612（2） , β = 90.869（3）°, V = 1231.7（6）3, Z = 4, C14H10F2N2O, Mr = 260.24, Dc = 1.403 g/cm3, μ（MoKα） = 0.111 mm-1, F（000） = 536, the final R = 0.0453 and wR = 0.1085 for 1317 observed reflections （I 2σ（I）） for Ⅱ. The antibacterial activities of both compounds against two bacteria were first studied and one compound showed considerable antibacterial activity against K. Pneumonia and S. aureus.

Synthesis of Pyridyl Polyheterocyclic Oxime-ether Schiff Bases Containing s-Triazole and Oxadiazole Subunits

4-Amino-5-pyridin-4-yl-s-triazole-3-thiol （1） was sequentally reacted with 3-chloro-1- phenylpropan-1-one to afford 3-（4-amino-5-pyridin-4-yl-s-triazole-3-sulfanyl）-1-phenylpropan-1- one （2） followed by oximation with hydroxylamine hydrochloride and etherification with 5-aryl-[13,4]oxadiazole-2-cbloromethanes to the corresponding oxime （3） and oxime-ethers （4a-e）, respectively. The condensation of compounds 4 with salicylaldehyde gave the title compounds （5a-e）. The antibacterial activity in vitro against Gram-postive （G^＋） and Gram negative （G） bacteria was primarily evaluated.

Substituent effect on spectral and antimicrobial activity of Schiff bases derived from aminobenzoic acids

The dependence of electronic absorption spectra antimicrobial property on the substituent position was investigated using three Schiff bases derived from salicylaldehyde and isomeric aminobenzoic acids in three solvents of different polarities. The absorption maxima in all three solvents exhibited dependence on the position of substituent with the absorption maxima undergoing a red shift as solvent polarity increased. The in vitro antibacterial activity of the compounds against some clinically important bacteria namely Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), Staphylococcus aureus (ATCC 25923), Enterococcus feacalis (ATCC 29212) was determined in N,N”-dimethylformamide and 1,4-dioxane using the agar dilution method. The results revealed that the ortho and meta substituted Schiff bases exhibited better antimicrobial activity in the non-polar solvent.

Synthesis, Molecular Structure and Antibacterial Activity of 1-(4-Methoxybenzaldehyde)-4-Methylthiosemicarbazone

A novel ligand, 1-(4-methoxybenzylidene)-4-methylthiosemicarbazone (MBT) derived from 4-methoxybenzaldehyde was synthesized and characterized by spectroscopic methods (IR, 1H NMR, 13C NMR), single crystal X-ray diffraction technique and physical means. MBT showed antibacterial activity in vitro with MICs of 64 μg/mL (a strain of Salmonella typhi (ATCC 6539)), 128 μg/mL (Salmonella typhi), 64 μg/mL (Salmonella paratyphi A), 128 μg/mL (Salmonella paratyphi B) and 64 μg/mL (Salmonella typhimurium). The results showed that MBT demonstrated moderate in vitro antibacterial activity against a strain of Salmonella typhi (ATCC 6539), Salmonella paratyphi A, and Salmonella typhimurium, indicating its promise as a possible lead for the discovery of antibacterial drugs.

Synthesis and Characterization of Schiff Base Metal Complexes Derived from Cefotaxime with 1<i>H</i>-indole-2,3-dione (Isatin) and 4-N,N-dimethyl-aminobenzaldehyde

This work involved the synthesis of two Schiff base derivatives of cefotaxime antibiotic (CFX) namely: [sodium3-(acetoxymethyl)-7-((Z)-2-(methoxyimino)-2-(2-((E)-2–oxoindolin-3-ylide-neamino) thiazol-4-yl)acetamido)-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate]. (0.5) Methanol (LI) and [sodium3-(acetoxymethyl)-7-((2Z)-2-(2-(4-dimethylamino) benzylideneamino) thiazol-4-yl)-2-(methoxyimino)acetamido)-8-oxo-5-thia-1-azabicyclo [4.2.0] oct-2-ene-2-carboxylate]. (0.5) Methanol (LII) from the condensation reaction of the antibiotic with 1H-Indole-2,3-dione(isatin) and -N, N-dimethyl amino benzaldehyde respectively. Metal complexes of the two Schiff base ligands with Co(II), Ni(II), Cu(II), Cd(II), Pd(II) and Pt(IV) ions were prepared by reacting each ligand with the metal salts in refluxing ethanol. The chemical structures of the two ligands as well as the stereo-chemical structures and geometries of the studied metal complexes were suggested depending the results obtained from CHN and TG analysis, NMR, FTIR, and atomic absorption spectrophotometry, electronic spectra, magnetic moments and conductivity measurements. The mole ratio of the ligands to the metal ion was 1:1 with tridentate bonding behaviors of the coordinating ligands with the metal ions.