Semicarbazone Ligand Research Articles

Structure and magnetic properties of two new lanthanide complexes with the 1-((E)-2-pyridinylmethylidene)semicarbazone ligand

Two novel semicarbazone-lanthanide(III) complexes were prepared and structurally characterized as [Ln (Hscpy)2 (NO3)2]NO3·MeOH (Ln = Gd and Tb; Hscpy = 1-((E)-2-pyridinylmethylidene)semicarbazone). The 4f metal ions experience deca-coordination geometry. Each molecular formula contains two neutral Hscpy molecules in the keto form coordinated through two nitrogen atoms and one oxygen atom, while two nitrate ligands are both coordinated in a chelate mode. The 1 + charge of the cation-complex is balanced by a nitrate anion. Extensive intermolecular hydrogen bonds are formed through the methanol solvate molecule, which acts both as a donor and an acceptor molecule. The chemical composition of the compounds was confirmed by high resolution mass spectra (ESI-MS); peaks at m/z = 122.07 and 148.05, assigned to the fragments C6H8N3+ and C7H6N3O+, respectively, are in agreement with the coordination of Hscpy. Alternating current magnetic susceptibility analysis was performed in the 10–10000 Hz range, and the terbium-complex showed slow relaxation of the magnetization when immersed in a static magnetic field of 1 kOe and 1.5 kOe, with an activation barrier to the relaxation (21.9(4) cm−1) among the highest found for ten-coordinated Tb(III) complexes. This behavior of slow relaxation of the magnetization is relevant as a memory effect regarding the development of Single Molecule Magnets (SMM).

Spin-crossover behavior of neutral iron(iii) complexes with salicylaldehyde thio-, seleno- and semicarbazone ligands: experiment and theoretical analysis.

The iron(iii) complex [Fe(Hsemsal)(semsal)]·3H2O (1) (H2semsal - salicylaldehyde semicarbazone) has been synthesized and characterized by powder and single crystal X-ray diffraction, and magnetic susceptibility measurements. Crystal structure analysis showed that the complex forms neat stacks stabilized by hydrogen-bonding through water molecules and π-π interactions between phenolate rings of ligands. The complex does not exhibit spin-crossover phenomena and remains in the high-spin state down to 2 K. DFT calculations were performed for a series of neutral Fe(iii) complexes, and the influence of the N2S2O2, N2Se2O2 and N2O4 coordination environment on the spin transition in these complexes was traced. The effect of substituents in the benzene ring of salicylaldehyde on the stabilization of the HS or LS states in complexes of this type was analyzed.

Some boron compounds of semicarbazones: antimicrobial activity and precursor for the sol–gel transformation to nanosized boron oxide

Biologically active boron Schiff base compounds: precursors for the low temperature synthesis of B2O3 and B7O.

Template synthesis of two new supramolecular zinc(II) complexes containing pentadentate N3O2 semicarbazone ligand: Nanostructure synthesis, Hirshfeld surface analysis, and DFT studies

Two new zinc(II) complexes, [Zn(H2dapsc) (CH3OH)2][ZnBr2Cl2] (1) and [Zn(H2dapsc) (CH3OH)Br]Br.(CH3OH) (2), where H2dapsc is 2,6-diacetylpyridine bis(semicarbazone), were synthesized using a template method in which the pentadentate N3O2 semicarbazone ligand derived from [1 + 2] condensation of 2,6-diacetylpyridine and semicarbazide in the presence of zinc(II) ion as template agent. These compounds were characterized by IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Their single crystal X-ray structures showed that in both complex cations, the metal center has a distorted pentagonal-bipyramidal geometry in which the semicarbazone (H2dapsc) ligand occupies the equatorial plane, while the axial positions occupy by two methanol ligands in (1) and two bromo and methanol ligands in (2). Furthermore, the impact of the close intermolecular contacts on the crystal packing of (1) and (2) have been further studied using Hirshfeld surface analysis. Density Functional Theory (DFT) method was applied for the calculation of HOMO-LUMO energy gap, atomic charges and vibrational frequencies of title complexes. Moreover, the nanostructure of zinc complex was synthesized by a sonochemical method and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), FT-IR spectroscopy, and elemental analysis.

Syntheses, silylation, characterization, and antimicrobial and antifertility activities of organoboron derivatives of some bioactive monofunctional bidentate semicarbazones

Some new mononuclear organoboron derivatives of the type PhBL1–5(OH) (1a–1e) were synthesized by the reaction of PhB(OH)2 and LH (LH = OC(NH2)NH:NC(CH3)4C6H4R, where R = H (L1H); CH3(L2H); OCH3(L3H); Cl (L4H); Br (L5H)) in 1:1 molar ratio in refluxing tetrahydrofuran (THF). This was followed by the reactions of PhBL1–5(OH) with NH(SiMe3)2 in 2:1 molar ratio in THF to yield new heterodinuclear derivatives of the type PhBL1–5(OSiMe3) (2a–2e). All these newly synthesized complexes were characterized using elemental analyses and their probable structure was proposed on the basis of infrared, 1H NMR, 13C NMR, 11B NMR and 29Si NMR spectral data and mass spectrometry. Semicarbazone ligands and their corresponding mono‐ and heterodinuclear boron derivatives were screened against pathogenic bacteria (E. coli and P. aeruginosa) and fungi (A. niger and P. peniculosum) to examine their antimicrobial activities. Representative compounds of each series of mono‐ and heterodinuclear boron derivatives and a ligand were screened for their antifertility activity on male adult Wistar rats.

A copper(II) complex of a semicarbazone: crystal structure, spectroscopic analysis and cytotoxicity against human cancer cell lines

A Cu(II) complex of 2-hydroxyacetophenone N(4)-phenyl semicarbazone (H2L) has been prepared, and its crystal structure is reported. The single-crystal X-ray study reveals a dimeric structure with a distorted square planar coordination geometry around each copper atom, with an ONO-donor ligand and µ2-oxo group located between the two copper atoms. The secondary coordination sphere of Cu(II) is six-coordinate, with a NO3 − ion and methanol solvent molecule making weak interactions. Supramolecular interactions involving the adjacent complexes were investigated. The complex [Cu(HL)]2(CH3OH)2(NO3)2 was also characterized by physicochemical and spectroscopic methods. The biological activity of the free semicarbazone and its Cu(II) complex were evaluated by cytotoxicity assays against human cancer cell lines. A dimeric stable complex between copper(II) and semicarbazone ligand has been synthesized, and the crystal structure has been studied. Spectroscopy experiments and cytotoxicity assays against human cancer cell lines were performed.

Synthesis Characterization and Biological Application of 2,3,4-Trimethoxy Benzaldehyde Semicarbazone Co(II) Metal Ions.

[Co(L4)2Cl2] were prepared by reacting 2,3,4-trimethoxy benzaldehyde semi carbazone ligands with CoCl2.6H2O. The IR, UV, Mass and 1H NMR spectra of the complexes have been assigned. Thermo gravimetric analysis were also carried out. The data agree quite well with the proposed structures and show that the complexes were finally decomposed to the corresponding ligands. Complexes were screened for antimicrobial activities by the disc diffusion technique using DMSO as solvent. The activity data show that the semi carbazone metal complexes are more potent antimicrobials metal complexes.

Supramolecular architectures and crystal structures of gold(III) compounds with semicarbazones

The synthesis and crystal structures of two novel semicarbazones and four gold(III) compound derivatives of these semicarbazones are presented. A pattern in the formation of the semicarbazones shows the association of Cl– ions held together by intra- and intermolecular forces. [AuCl4]− and [AuBr4]− anions are co-crystallised with these semicarbazone ligands, and the packing architectures revealed by a single-crystal X-ray diffraction analysis showed the different influences of the anions and the association of these chemical species by intermolecular forces on the crystal packing. Crystal engineering led to gold(III) compounds that are stabilised by relevant hydrogen bonding networks, which demonstrated their importance to the supramolecular organisation of the studied compounds. Interestingly, Cl∙∙∙Br interactions are observed and contribute to the formation of the supramolecular structures. Elemental analysis data and spectroscopic properties in the solid state and solution are also described.

Cd (II) Ion-Selective Electrode Based on 2 –Acetylthiophene Semicarbazone in Polymeric Membrane

A new polyvinylchloride membrane sensor for Cd+2 ions has been prepared using 2–acetylthiophene Semicarbazone ligand as an electroactive ionophore and dibutylphthalate (DBP) as a plasticizing agent. The best performance was recorded with a membrane composition of PVC: DBP: Ionophore: NaTPB as 31: 64: 3.2: 1.8 (w/w %).The sensor exhibits a Nernstian response for Cd+2 ions over a wide concentration range (1.0 ×10–5 to 1.0 ×10–1 M) with a slope of 29.4 ± 0.2 mV decade–1. It has a fast response time of ˂ 10 s and can be used for at least 5 weeks without any divergence in potential. The electrode can be used in the pH range from 3.4 to 7.6. The proposed sensorrevealed relatively good selectivity and high sensitivity for Cd+2 ions in presence of a number of mono, di andtrivalent interfering cations within the working range of the electrode. The electrode was successfully applied for the direct determination of Cd+2in solution and, as an indicator electrode, in potentiometric titration of cadmium ions using ethylenediamine tetraacetic acid (EDTA) as titrant. Keywords: Ion Selective Electrodes, Cadmium, PVC membrane, semicarbazide

Cd (II) Ion-Selective Electrode Based on 2 –Acetylthiophene Semicarbazone in Polymeric Membrane

A new PVC membrane sensor for Cd+2 ions has been prepared using 2–acetylthiophene Semicarbazone ligand as an ionophore and dibutylphthalate (DBP) as a plasticizing agent. The best performance was recorded with a membrane composition of PVC: DBP: Ionophore: NaTPB as 31: 64: 3.2: 1.8 (w/w %). The sensor exhibits a Nernstian response for Cd+2 ions over a wide concentration range (1.0 ×10–5 to 1.0 ×10–1 M) with a slope of 29.4 ± 0.2 mV decade–1. It has a fast response time of ˂ 10 s and can be used for at least 5 weeks without any divergence in potential. The electrode can be used in the pH range from 3.4 to 7.6. The proposed sensor was successfully applied for the direct determination of Cd+2 in solutions and, as an indicator electrode, in potentiometric titration of cadmium ions using EDTA as titrant.

Formation and stability of Co(II), Ni(II), Cu(II) and Zn(II) complexes of pyridoxal semicarbazone and pyridoxal thiosemicarbazone in solution

The formation and stability of Pyridoxal semicarbazone (PLSC) and Pyridoxal thiosemicarbazone (PLTSC) Schiff base ligand (L) complexes of Co(II), Ni(II), Cu(II) and Zn(II) have been investigated by Irving-Rossotti pH-metric titration technique, at 30 ± 1oC and an ionic strength of 0.1M KNO3 in 70% v/v DMF-H2O medium. The acid dissociation constants (pKa) of the ligands and the stability constants of the metal complexes formed in solution were determined. The results indicate the formation of 1:1(ML) and 1:2(ML2) complexes in solution. The order of stability of the metal complexes with respect to the metal ions follows the Irwing -william's natural order, Co(II) Zn(II).

Four transition metal complexes with a semicarbazone ligand bearing pyrazine unit

Four new complexes based on L (where L = 3-ethyl-2-acetylpyrazine semicarbazone), namely [CoL2]Cl2·0.5H2O (1), [CoL2](NO3)2 (2), [CdL(H2O)2(NO3)](NO3)·H2O (3) and [CuL(CH3OH)Cl2]·[CuLCl2] (4) have been synthesized and characterized by X-ray diffraction analyses. The results show that the semicarbazone acts as a tridentate neutral ligand in all complexes. Each of complex 1 and 2 reveals a distorted octahedral geometry around the metal ion provided by two units of the ligand, while the ratio of the ligand and metal is 1:1 in complexes 3 and 4. The effect of complexes 1–4 on cell proliferation, apoptosis of human pancreatic cancer (Patu8988), human gastric cancer (SGC7901) and human hepatic cancer (SMMC7721) cell lines have been detected by MTT assay, Annexin V/PI double staining flow cytometry and TUNEL assay. The results show that complexes 1–4 can inhibit cell proliferation of Patu8988, SGC7901 and SMMC7721 cells, significantly higher than the effect of the ligand. However, the complex 4 reveals higher apoptosis rate, and displays up-regulated expression level of caspase 3, detected by western blotting, which also indicates the complex 4 can induce caspase-dependent cell apoptosis in SMMC7721.

Cyclometalated Iridium(III) Complexes Containing Semicarbazone Ligands: Synthesis, Characterization, Photophysical and Biological Studies

AbstractThe synthesis, crystal structure, photophysical properties, and biological activity of the novel bis‐cyclometalated complexes [Ir(ptpy)2(vnsc)] (2) and [Ir(ptpy)2(acsc)] (3) [ptpy = 2‐(p‐tolyl)pyridinato, vnsc = vanillin semicarbazone, acsc = acetone semicarbazone] are described. The new compounds were prepared by the reaction of [{Ir(μ‐Cl)(ptpy)2}2] (1) with the corresponding semicarbazone ligands under basic conditions. The molecular structure of compound 3 was confirmed by a single‐crystal X‐ray diffraction study. The complex crystallized from chloroform as a mono‐ solvate in the orthorhombic space group Pcab with eight molecules in the unit cell.

Syntheses of nickel (II) complexes from novel semicarbazone ligands with chloroformylarylhydrazine, benzimidazole and salicylaldehyde moieties.

This study addressed the design and syntheses of diverse ligands, which were then successfully treated with Ni (II) ion to afford a series of nickel complexes. α-Chloroformylarylhydrazine hydrochlorides 6 contain two different functional groups. One is a strong nucleophile, and the other is a good electrophile. Therefore, it can be designed to react with several reagents to obtain diverse derivatives which can be used as ligands for metal complexes. Furthermore, benzimidazole and salicylaldehyde can provide electron donor sites, N and O electron donors, separately. Hence, the starting materials α-chloroformylarylhydrazine hydrochlorides 6 were first treated with 2-(aminomethyl)-benzimidazole (7) to give the corresponding semicarbazides 8. Then, the semicarbazides 8 reacted with various substituted salicylaldehydes 9–11 to afford the desired substituted-salicylaldehyde 2-aryl-4-substituted semicarbazones 12–14, which could coordinate with nickel (II) ion to give the corresponding nickel complexes 15–17.

Preparation, Characterization & Biological activity for Some Iron(II) Complexes Containing Mixed Ligands (Benzilazine & Semicarbazone) & Study of Laser Effect on Them

The research included preparation of new iron(II) complexes with mixed ligands including benzilazine(BA) and semicarbazone ligands {benzilsemicarbazone- BSCH or benzilbis(semicarba-zone)- BBSCH2 or salicylaldehydesemicarbazone- SSCH2 or benzoinsemicarbazone- B'SCH2}.by classical and microwave methods. The resulted complexes have been characterized using chemical and physical methods. The study suggested that the above ligands form ionic complexes having formulae [Fe(SCHi)(BA)(Cl)m](Cl)2-m {where SCH, BSCH, BBSCH2, SSCH¬2 or B'SCH2 ligands; m=1 or 2}. Hexacoordinated mononuclear complexes have been investigated by this study and having octahedral geometries. The effect of laser ray type visible region have been studied on solid ligands and complexes for 1-3 hours, all the semicarbazone ligands have been affected slightly which can be neglected through the results of decomposition or melting points, while azine ligand does not affected by this kind of ray, i.e. stable ligand. Whereas, a noticeable effect have been observed on the most complexes through the results of decomposition or melting points which suggest the change in their structures, meanwhile the other complexes affected slightly by this kind of radiation which suggests the breaking of the hydrogen bond only. The activity of all the salt, ligands and complexes have been evaluated by agar plate diffusion techniques against human pathogenic bacterial strains: Staphylococcus aureus, Escherichia coli, Pseudomonas auruginosa, Streptococcus faecalis, Proteus mirabilis and Entero-bacter aerogenes. All the ligands and complexes were found to have antibacterial activity against all the bacteria in vivo. The activity of all the ligands and complexes have been evaluated on Tonsillitis from males and females. They show very good activity against this pathogen

ChemInform Abstract: Carbohydrate Derived Thiosemicarbazone and Semicarbazone Palladium Complexes: Homogeneous Catalyst for C—C Cross Coupling Reactions.

AbstractTwo Pd‐catalysts with carbohydrate derived thiosemicarbazone and semicarbazone ligands are developed and both are efficient for Suzuki—Miyaura and Sonogashira coupling reactions.

Synthesis, X‐ray Diffraction Study, and Cytotoxicity of a ­Cationic p‐Cymene Ruthenium Chloro Complex Containing a Chelating Semicarbazone Ligand

AbstractAn organometallic salt composed of a new cationic p‐cymene ruthenium chloro complex containing a chelating benzaldehyde semicarbazone ligand and of the known anionic p‐cymene ruthenium trichloro complex, [(η6‐p‐cymene)Ru(bzsc)Cl]+[(η6‐p‐cymene)RuCl3]– (1) (bzsc = benzaldehyde semicarbazone) was synthesized and further characterized by IR, 1H NMR, and UV/Vis spectroscopy HR‐ESI mass spectrometry, and elemental analysis. The single‐crystal structure of 1 was also determined. The in vitro anticancer activities of the complex was evaluated against three human cancer cell lines (SGC‐7901, BEL‐7404 and CNE‐1), and the IC50 values were 20.7, 71.1 and 42.6 μM, respectively.

Synthesis, structure and electrochemistry behavior of a cobalt(III) compound with azide and methyl 2-pyridyl ketone semicarbazone ligands

An unprecedented cobalt(III) compound with methyl 2-pyridyl ketone semicarbazone (HL) and the auxiliary azide ligand, [Co(L)2] [Co(L)(N3)3] (1) was synthesized and further characterized crystallographically and spectroscopically. Compound 1 crystallizes in the triclinic system and space group of P-1 and its structure consists of two mononuclear crystallographic units with metal chromophore comprising two cobalt(III) centers revealing distorted octahedral geometries and formed by distinct ligands in the inner coordination spheres. Interestingly, compound 1 represents the first complex formed by two distinct mononuclear units involving this ligand. As consequence of various donor and acceptor groups in both crystallographic units, there are several strong NH⋯N and NH⋯O hydrogen bonding interactions interconnecting adjacent moieties, ultimately leading to a three-dimensional supramolecular network. Furthermore, the electrochemical behavior of the HL and compound 1 were investigated.

ChemInform Abstract: Mononuclear Palladium and Heterodinuclear Palladium—Ruthenium Complexes of Semicarbazone Ligands. Synthesis, Characterization, and Application in C—C Cross‐Coupling Reactions.

AbstractA variety of mononuclear palladium and heterobinuclear Pd—Ru N,N,O‐pincer complexes is synthesized and studied in Suzuki, Heck and Sonogashira cross‐coupling.

Ship-in-a-bottle synthesis and physicochemical studies on zeolite encapsulated Mn(II), Mn(III)-semicarbazone complexes: application in the heterogeneous hydroxylation of benzene

Complexes of Mn(II) and Mn(III) with semicarbazone ligand (SALSC) derived from salicylaldehyde and semicarbazide have been occluded in zeolite-Y supercages by a diffusion method. The synthesized host/guest materials have been isolated and characterized by various physico-chemical techniques. The results have revealed that, SALSC can coordinate with the central metal ions via the (C=N), deprotonated enolic (C=O) and phenolic (OH) groups. Investigation of the stereochemistry pointed out that, the intrazeolitic manganous and manganic semicarbazone complexes have a 1M:2L tetrahedral and 1M:1L penta-coordinate structures, respectively. The catalytic activity of the samples was evaluated towards benzene hydroxylation at 80 °C and the results showed a stimulation activity to give phenol with the sequence MnII-Y > MnIII(SALSC)/Y > MnII(SALSC)/Y.