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, Characterization and Biological Activity of Transition Metals with Schiff Base Derived from Adamantaneamineand o-Vanillin

Five new solid complexes were synthesized about transition metals with Schiff base（ L, C18H23NO2 ） derived from adamantaneamine and o-vanillin, and characterized by elemental analysis, molar conductance, infrared spectra, UV-vis spectra, thermal analysis. Their chemical formula are [ML2]（ClO4）2 （ M= Mn, Co, Ni, Cu, Zn）, and the coordination numbers are four, The antibacterial activity of Schiff base ligand and its complexes was studied.

Synthesis, Structure and Biological Activity of 5-Benzyl-4-amino-1,2,4-triazole-3-thione Schiff Base

A novel Schiff base was synthesized via 5-benzyl-4-amino-1,2,4-triazole-3-thione with 3-phenoxy-benzaldehyde under refluxing. The structure was characterized by elemental analysis, IR, 1H NMR, ESI-MS and single-crystal X-ray diffraction. This compound crystallizes in monoclinic, space group P21 /c with a = 16.0289（16）, b = 5.8022（6）, c = 20.542（2）, β = 95.667（2）o, C22 H18 N4 OS, Mr = 386.46, V = 1901.1（3）3, Z = 4, Dc = 1.347 g/cm3, F（000） = 804, μ = 0.191 mm-1, the final R = 0.0453 and wR = 0.1307 for 2456 observed reflections with I 〉 2σ（I）. The crystal packing of the compound is stabilized by classical intermolecular N–H…S hydrogen bonds. Furthermore, the biological activity to four vegetable pathogens has been tested. The title compound exhibited good fungicidal activities to Gibberlla nicotiancola.

A New Schiff Base Derivatives Designed to Bind Metal Ion (Cu, Co): Thermodynamics and Biological Activity Studies

Schiff base synthesis is usually acid catalyzed and it usually requires refluxing the mixture of aldehydes and amine in ethanolic solution. Synthesis and characterization of Schiff base ligands derived from substituted amine and salicylaldehyde and their complexes (Cu2+, Co2+) are reported. The ligands and ligand-complexes were characterized by melting point, FTIR, CHN-elemental analysis and UV-Visible analysis. The UV-Visible and elemental analysis of complexes established (1:2) mole ratio (M:L). The stability constant and thermodynamic parameters (K, ΔG, ΔH, ΔS) were determined at different temperature (30 - 40)°C which established that the metal-complexes were very stable. The review describes the promising biological activities of Schiff base and their metal complexes.

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.

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.

Syntheses,Crystal Structures and Biological Activities of Three New Schiff Bases Derived from Substituted Salicylaldehyde and Tris Base

Three new o-hydroxy Schiff bases, L1, L2 and L3, were derived from the 1：1 M condensation of substituted salicylaldehyde with tris base and were characterized by FT-IR, ^1H NMR and ^13C NMR spectroscopies. The crystal structure of L1 was also determined by single-crystal X-ray analysis, and it exists as a zwitterionic form in the solid state, with the H atom of the phenol group being transferred to the imine N atom. It adopts an E-configuration about the central C=N double bond. In addition, the biological activity assay was carried out and the results show that the Schiff-base compounds have a diverse range of biological activities against the fungi tested, which suggests great potential applications in antifungal fields in the future.

Synthesis,Crystal Structure and Cytotoxic Activity of a Zinc(Ⅱ) Complex of the Schiff Base Derived from S-benzyldithiocarbazate

A novel zinc（Ⅱ） complex of empirical formula,ZnL2（L=anionic forms of S-benzyl-β-N-（2,4-dichlorobenzylidene） hydrazine carbodithioate）,has been synthesized and characterized by elemental analysis,IR spectra and single-crystal X-ray diffraction.The crystal belongs to the triclinic system,space group P with a = 9.3168（9）,b = 13.0353（13）,c = 14.7702（15） ,α = 71.2860（10）,= 87.5140（10）,γ = 79.4480（10）o,V = 1670.0（3） 3,Z = 2,Mr = 773.93,Dc = 1.539 g/cm3,μ = 1.334 mm-1,F（000） = 784,the final R = 0.0403 and wR = 0.0800 for 4060 observed reflections with I〉2（I）.In the crystal structure,the zinc（Ⅱ） complex has a distorted tetrahedral geometry in which the zinc ion is coordinated by the nitrogen and sulfur atoms from two Schiff base ligands,respectively.The preliminary bioassay indicates that the Schiff base and its zinc complex exhibit inhibitory activity against the human gastric cancer cell lines（MKN45） and hepatoma cell lines（HepG2）.

Probing the dynamic thermodynamic resolution and biological activity of Cu(Ⅱ) and Pd(Ⅱ) complexes with Schiff base ligand derived from proline

Schiff base metal complexes are of great importance in pharmaceutical science owing to their unique chemical properties, which enable them to exhibit diverse biological activities such as anti-bacterial,anti-oxidant, anti-inflammatory, and anti-tumor properties. Furthermore, Schiff base metal complexes can serve as reagents and catalysts in chemical reactions. This review aims to provide an overview of our recently published studies on Cu(Ⅱ) and Pd(Ⅱ) complexes derived from proline Schiff base ligands. We also discuss the potential applications of these metal complexes in the fields of antibacterial and chiral resolution.

Synthesis,Crystal Structure and Biological Activity of(E)-3-Chloro-2-(2-(2-methylbenzylidene)-hydrazinyl)pyridine

The novel Schiff base（E）-3-chloro-2-（2-（2-methylbenzylidene）hydrazinyl）pyridine was synthesized and characterized by ^1H NMR, MS, elemental analysis and X-ray diffraction. The compound crystallizes in monoclinic space group Pbca with a = 14.6638（3）, b = 7.7522（2）, c = 20.3850（4） A, V = 2317.30（9） A^3, Z = 8, R = 0.063 and w R = 0.1922. The title compound exhibits good antifungal activity against Stemphylium lycopersici（Enjoji） Yamamoto and Fusarium oxysporum sp. cucumebrium.

Synthesis,Crystal Structure and Biological Activity of a Planar Copper Complex Derived from S-benzyldithiocarbazate

A planar transition metal complex Cu（L）2 （L = （E）-benzyl-2-（4-nitrobenzylidene）-hydrazinecarbodithioate） has been prepared and determined by X-ray single-crystal diffraction. The crystal belongs to the monoclinic system,space group P21/c with a = 6.7101（11）,b = 16.952（3）,c = 13.962（3） ,β = 92.458（4）°,V = 1586.7（5） 3,Z = 4,Mr = 724.33,Dc = 1.516 g·m-3,μ = 0.998 mm-1,F（000） = 742,S = 1.021,R = 0.0634 and wR = 0.1077 for 813 observed reflections with Ⅰ〉 2σ（Ⅰ） and 205 parameters. In the molecular structure of the title complex,the copper atom exhibits a slightly distorted square-planar geometry in which the basal plane is defined by two N and two S atoms from two bidentate ligands. The complex was evaluated for its antitumor activity against two kinds of cell lines （MKN45 and HepG2） by MTT method. The preliminary bioassay indicates that the complex exhibits weak antitumor activity.

Synthesis, Characterization and Biological Activities of Binuclear Metal Complexes of 2-Benzoylpyridine and Phenyl(Pyridin-2-yl) Methanediol Derived from 1-Phenyl-1-(Pyridin-2-yl)-N-(Pyrimidin-2-yl) Methanimine Dihydrate Schiff Base

The Schiff base, 1-phenyl-1-(pyridin-2-yl)-N-(pyrimidin-2-yl)methanimine dihydrate (L1) has been synthesized by the condensation reaction between 2-aminopyrimidine and 2-benzoylpyridine and characterized using 13C-NMR, 1H-NMR, microanalysis, FT-IR, DEPT-135, HSQC, HMBC, COZY, NOESY. The reaction of 1-phenyl-1-(pyridin-2-yl)-N-(pyrimidin-2-yl)methanimine dihydrate (L1) with salts of V(IV), Co(II) and Cu(II), however, resulted in the hydrolysis of L1 to give binuclear metal complexes of 2-benzoylpyridine (L2) and phenyl(pyridin-2-yl)methanediol (L3) which were characterized using UV-visible spectroscopy, and TGA. The single crystal x-ray structure determined for the Copper(II) complex revealed that we obtained a compound previously obtained using a different method of synthesis. The Schiff base ligand (L1) is soluble in methanol, ethanol, DMSO, acetone and DMF. Microanalysis and Spectroscopic studies indicated that binuclear metal complexes were obtained by the coordination of metal ion to 2-benzoylpyridine (L2) and phenyl(pyridin-2-yl)methanediol (L3) from the hydrolysis of L1. Spectroscopic and elemental analysis reveal the formation of square pyramidal complexes of Co(II) and Cu(II) and a square planar complex of V(IV). In vitro antibacterial and antifungal activity against three bacterial strains (Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus) and three fungal stains (Candida albicans, Candida glabrata and Candida parapsilosis) showed moderate biological activity. Antioxidant studies reveal that only the binuclear Co(II) and oxovanadium(II) complexes are potent to eliminate free radicals.

Biological Activities of Schiff Bases and Their Complexes: A Review of Recent Works

Schiff bases are the most widely used organic compounds. They have been shown to exhibit a broad range of biological activities, including antifungal, antibacterial, antimalarial, antiproliferative, anti-inflammatory, antiviral, and antipyretic properties. This review summarizes the synthesis and biological activities of Schiff bases and their complexes.

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, 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, Structure and Biological Activity of 3-Methyl-4-(3-nitrobenzylideneamino)-5-ethoxycarbonyl-methylsulfanyl-1,2,4-triazole

A Schiff base was synthesized by 3-methyl-4-amino-5-ethoxycarbonyl-methylsul- fanyl-1,2,4-triazole with 3-nitrobenzaldehyde. The structure was confirmed by IH NMR, IR, H RMS, TGA techniques and X-ray diffraction. The crystal belongs to monoclinic system, space group P21/c, with a = 8.965（2）, b = 21.903（5）, c = 9.197（2） ,A, β = 114.011（4）°, CIaH15NsOnS, Mr = 349.08, V= 1649.7（6） A3, De = 1.407 g·cm-3, Z = 4, F（000） = 728,μ =0.226 mm1, the final R = 0.0574 and wR = 0.1336 for 2932 unique reflections with 1 〉 2σ（I）. Furthermore, the biological activity to four vegetable pathogens has been tested. The title compound exhibits better biological activity to four vegetable pathogens compared to the Schiff base without 5-ethoxycarbonyl and to Gibberlla saubinetti in EC95 compared with triadimefon.

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.

Schiff Bases as Important Class of Pharmacological Agents

Therapeutics are compounds,which do not always exhibit healing powers.They sometimes prevent or control roles.Many compounds,well known or less are treated as the therapeutic agents.Among them,there is a specific group of molecules named commonly as Schiff bases,chemically imines.Schiff bases are aldehyde-or ketone-like compounds in which the carbonyl group is replaced by an imine-HN=СН-or azomethine-NHN=СН-group,they are an important class of compounds for new drug development.Schiff base modifications so far proved to be very effective with increased efficacy and reduced toxicity.Therefore,many researchers have synthesized these compounds as target structures and evaluated their biological activity.The aim of this work was to present some interesting and promising examples of Schiff bases which exhibit biological activity.