Synthesis,spectral characterisation and thermal studies of zirconyl complexes of biologically active molecules

Zirconyl complexes of hippuric acid (C₉H₉NO₃, hipH) and monophenylbutazone (4-butyl-1-phenyl-3,5-pyrazolidinedione, MPB) were prepared using ZrOCl₂ · 8H₂O and ZrO(NO₃)₃ · xH₂O and characterized by elemental analysis, molar conductance measurement and IR, UV–Vis and NMR spectral methods. Thermal decomposition behaviour was studied by thermogravimetry. The second harmonic generation (SHG) conversion efficiency of hippuric acid complexes was also studied.     

Synthesis,structural and thermal studies of some biologically active antimony semicarbazones and thiosemicarbazones

The reactions of Ph₃SbCl₂ and SbCl₃ with semicarbazone and thiosemicarbazone ligands resulted in Ph₃SbCl₂(L) and SbCl₃(L) (L?=?semicarbazone and thiosemicarbazone ligands). These complexes were characterized by elemental analyses, IR, ¹H and ¹³C {¹H} NMR spectral data, and conductometric measurements. On the basis of spectroscopic data, a seven-coordinate and a five-coordinate antimony with ligand coordination through oxygen/sulfur and azomethine nitrogen have been suggested for Ph₃SbCl₂(L) and SbCl₃(L), respectively. These compounds show antifungal and antibacterial activities. Thermal behavior of some of the adducts have been studied by thermogravimetric analyses. Thermal decomposition of Ph₃SbCl₂(L) and SbCl₃(L) resulted in micron size Sb and Sb₂S₃ particles. The materials obtained were characterized by powder X-ray diffraction patterns, scanning electron microscopy, and energy dispersive X-ray analysis (EDAX).     

Synthesis,spectral, thermal,potentiometric and antimicrobial studies of transition metal complexes of tridentate ligand

A series of metal complexes of Cu(II), Ni(II), Co(II), Fe(III) and Mn(II) have been synthesized with newly synthesized biologically active tridentate ligand. The ligand was synthesized by condensation of dehydroacetic acid (3-acetyl-6-methyl-(2H) pyran-2,4(3H)-dione or DHA), o-phenylene diamine and fluoro benzaldehyde and characterized by elemental analysis, molar conductivity, magnetic susceptibility, thermal analysis, X-ray diffraction, IR, ¹H-NMR, UV–Vis spectroscopy and mass spectra. From the analytical data, the stoichiometry of the complexes was found to be 1:2 (metal:ligand) with octahedral geometry. The molar conductance values suggest the non-electrolyte nature of metal complexes. The IR spectral data suggest that the ligand behaves as a dibasic tridentate ligand with ONN donor atoms sequence towards central metal ion. Thermal behaviour (TG/DTA) and kinetic parameters calculated by the Coats–Redfern and Horowitz–Metzger method suggest more ordered activated state in complex formation. To investigate the relationship between stability constants of metal complexes and antimicrobial activity, the dissociation constants of Schiff bases and stability constants of their binary metal complexes have been determined potentiometrically in THF–water (60:40%) solution at 25 ± 1 °C and at 0.1 M NaClO₄ ionic strength. The potentiometric study suggests 1:1 and 1:2 complexation. Antibacterial and antifungal activities in vitro were performed against Staphylococcus aureus, Escherichia coli and Aspergillus niger, Trichoderma, respectively. The stability constants of the metal complexes were calculated by the Irving–Rosotti method. A relation between the stability constant and antimicrobial activity of complexes has been discussed. It is observed that the activity enhances upon complexation and the order of antifungal activity is in accordance with stability order of metal ions.     

Synthesis,spectral and antimicrobial activity studies of o-aminoacetophenone o-hydroxybenzoylhydrazone complexes

Coordination compounds of Mn^II, Co^II, Ni^II, Cu^II, Zn^II, Cd^II and Hg^II ions with o-aminoacetophenone o-hydroxybenzoylhydrazone (AAOHBH) were synthesized and characterized by elemental analyses, molar conductivity, magnetic moments (at ca. 25°C) and spectral (i.r., u.v., n.m.r. and m.s.) studies. The i.r. spectra show that the ligand acts in a monovalent bidentate, neutral bidentate and/or neutral tridentate fashion, depending on the metal salt used and the reaction medium. Tetrahedral structures are proposed for both Co^II and Ni^II complexes and square planar for Cu^II complexes on the basis of magnetic and spectral evidence. The complex formation in solution was investigated potentiometrically and spectrophotometrically. Spectral studies in solution show that the ligand can be used for the microdetermination of Co^II ion within a metal concentration up to 46.3p.p.m. The electrical conductivity of AAOHBH and its metal complexes was determined. The tendency of AAOHBH to form complexes with Co^II, Ni^II, Cu^II, Cd^II and Hg^II ions in 50% aqueous-dioxane was studied by pH measurements.The antimicrobiol activity of AAOHBH and its complexes derived from Co^II, Ni^II and Cu^II illustrates that the Ni^II complex seems to be inert towards Escherichia coli and Bacillus subtilis. The antimicrobial activity of the Cu^II complex was higher against E. coli and lower against B. subtilis than the corresponding organic ligand. The Co^II complex has the same activity as the organic ligand against E. coli.     

Synthesis and spectral studies of the biologically active complexes of tantalum(V) with N-alkylphenothiazines

Dioxo-bridged binuclear tantalum(V) complexes with six N-alkylphenothiazines (NAP) of general formula [TaO(L)(C2O4)]2C2O4, (L=NAP) have been prepared and characterized on the basis of elemental analysis, conductometric, magnetic and thermogravimetric data. The spectra of the complexes indicate that both the phenothiazine ligands and oxalate groups are coordinated to tantalum in a bidentate fashion, suggesting a coordination number of six around metal. The fungitoxicity of the isolated complexes against several fungi has been investigated.     

Synthesis of some new biologically active coumarin derivatives

The reaction of 4-hydroxycoumarin in toluene with a variety of aromatic binucleophilic compounds has been studied. 3-(Dimethylaminomethylene)chromane-2,4-dione was used as a key intermediate for the preparation of bis[N-(4-oxocoumarinylmethylene)]-1,4-diamines. Alternative synthetic procedures and antibacterial activity data of some of the new compounds are given. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 361–366, March, 2006.     

Thermal studies on some group VIII complexes with biologically active ligands

The mode of decomposition of complexes involving biologically important ligands such as thiouracil and xanthine coordinated to some group VIII metals has been studies by thermogravimetry. The results show that the complex tris-(dithiouracil) trichlororhodium(III) is monomeric and not polymeric as suggested previously. The decomposition behavior of the complex indicates that after the initial loss of a ligand molecule to form a four-coordinate complex, further ligand removal takes place in one sharp step. In the case of the complexes bis-(3-methylxanthine) diammineplatinum(II) and bis-(9-methylxanthine) diamminepalladium(II), ammonia comes off first, followed by rapid loss of the remaining xanthine ligands. Moreover, the activation energy determined for the main decomposition step suggests that the breakdown of the xanthine ligand involves the initial cleavage of the pyrimidine moiety, followed closely by loss of the remaining imidazole portion.

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Zusammenfassung Die Art der Zersetzung von Komplexen einiger Metalle der VIII. Gruppe mit biologisch wichtigen Liganden, wie Thiouracil and Xanthin, wurde thermogravimetrisch untersucht. Die Ergebnisse zeigen, daß der Komplex Tris-(dithiouracil) trichlororhodium(III) monomer und nicht — wie früher vermutet — polymer ist. Das Zersetzungsverhalten des Komplexes zeigt, daß nach dem zu einem tetrakoordinierten Komplex führenden Verlust eines Ligandmoleküls die Abgabe eines weiteren Liganden in einem scharfen Schritt erfolgt. Im Falle der Komplexe Bis-(3-methylxanthin) diamminplatin(II) und Bis-(9-methylxanthin) diamminpalladium(II) erfolgt zunächst eine Abspaltung von Ammoniak, der ein schneller Verlust der verbleibenden Xanthinliganden folgt. Die für die Hauptzersetzungsreaktion bestimmte Aktivierungsenergie läßt vermuten, daß der Abbau der Xanthinliganden über eine Spaltung des Pyrimidinteils verläuft, der schnell die Abgabe des verbleibenden Imidazolteils folgt.

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, , VIII . , -() (III) , , . - , . - (3-) (II) -(9 -) - (II) -(II) , . , , , , .

     

Synthesis,spectral, fluorescence and thermal studies on ionic hafnocene thiopurine complexes

Ionic chelates of hafnocene, with 6-mercaptopurine (HL¹) (A) and 6-thioguanine (HL²) (B) of the type [( ⁵-C₅H₅)₂HfL¹]⁺X^– (C) and [( ⁵-C₅H₅)₂HfL²]⁺X^– (D) (X = CuCl₃, ZnCl₃, CdCl₃, HgCl₃, PhNHNHCS₂) have been prepared and characterized by conductivity measurements and by i.r., electronic, ¹H-n.m.r. and ¹³C-n.m.r. spectra. Fluorescence studies of the complexes containing Hg in the anionic moiety, and relevant photochemical parameters, have been elucidated. Thermodynamic parameters have been calculated using thermogravimetric (t.g.) and differential thermal analytical (d.t.a.) curves and their variations have been correlated with some structural parameters of the complexes. The ligands, as well as their hafnium(IV) complexes, exhibit appreciable antibacterial and antifungal activity against E. coli, S. typhi, P. aeruginosa, Z. mobilis bacterial strains and versus A. awamori, A. niger fungal strains, respectively.     

Synthesis and spectral study of biologically active macrocyclic complexes of divalent transition metal ions

The condensation reaction of succinyldihydrazide with glyoxal in the presence of divalent metal ions (1: 1: 1) results in the formation of the complexes of type [M(C₆H₈N₄O₂)X₂], where M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and X = Cl⁻, NO₃⁻, CH₃COO⁻. The complexes have been characterized with the aid of elemental analyses, conductance measurements and electronic, NMR, infrared spectral studies. On the basis of these studies, a six-coordinated distorted octahedral geometry in which two nitrogen and two carbonyl oxygen atoms are suitably placed for coordination toward metal ion, has been proposed for all the complexes. The complexes were tested for their in vitro antibacterial activity. Some of the complexes showed remarkable antibacterial activities against some selected bacterial strains.     

Conventional and microwave synthesis,spectral, thermal and antimicrobial studies of some transition metal complexes containing 2-amino-5-methylthiazole moiety

Schiff base metal complexes of Cr(III), Co(II), Ni(II) and Cu(II) derived from 5-chlorosalicylidene-2-amino-5-methylthiazole (HL¹) and 2-hydroxy-1-naphthylidene-2-amino-5-methylthiazole (HL²) have been synthesized by conventional as well as microwave methods. These compounds have been characterized by elemental analysis, FT-IR, FAB-mass, molar conductance, electronic spectra, ¹H-NMR, ESR, magnetic susceptibility, thermal, electrical conductivity and XRD analyses. The complexes exhibit coordination number 4 or 6. The complexes are coloured and stable in air. Analytical data reveal that all the complexes exhibit 1:2 (metal:ligand) ratio. IR data show that the ligand coordinates with the metal ions in a bidentate manner through the phenolic oxygen and azomethine nitrogen. FAB-mass and thermal data show degradation pattern of the complexes. The thermal behaviour of metal complexes shows that the hydrated complexes lose water molecules of hydration in the first step; followed by decomposition of ligand molecules in the subsequent steps. XRD patterns indicate crystalline nature for 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 niger and Candida albicans. The antimicrobial results also indicate that the metal complexes are better antimicrobial agents as compared to the Schiff bases.     

Synthetic,spectral, structural and antimicrobial studies of some Schiff bases 3-d metal complexes

The complexes of tailor made ligands with life essential metal ions may be an emerging area to answer the problems of multi-drug resistance (MDR). The coordination complexes of VO(II), Co(II), Ni(II) and Cu(II) with the Schiff bases derived from 3-bromobenzaldehyde/3-chlorobenzaldehyde with 2-aminophenol have been synthesized and characterized by elemental analysis, molar conductance, electronic spectra, FT-IR, ESR, FAB mass, thermal and magnetic susceptibility measurements, FAB mass and thermal data show degradation of complexes. Both the ligands behave as bidentate coordinating through O and N donor. The complexes exhibit coordination number 4, 5 or 6. X-ray powder diffraction data shows that four (2, 3, 6 and 7) complexes are crystallized in tetragonal system. The in vitro biological screening effects of the investigated compounds were tested against the bacteria Escherichia coli, Staphylococcus aureus and Streptococcus fecalis and the fungi Aspergillus niger, Trichoderma polysporum and Candida albicans by serial dilution method. A comparative study of the MIC values of the Schiff base and their Co(II) (6) and Cu(II) (8) complexes, indicates that the metal complexes exhibit higher or lower antimicrobial activity than the free ligand (L₂).     

Synthesis,spectral and thermal studies of monomeric,homobimetallic and polymeric complexes containing benzoyldithiocarbazate

New mixed ligand complexes of benzoyldithiocarbazate (H₂BDT) have been synthesized and characterized by elemental analyses, spectral studies (i.r., u.v.–vis., mass), thermal analysis and electrical conductivity measurements. The complexes have the general formulae: [M₂(BDT)(OX)₂] · xH₂O; [Co₂(BDT)(OX)₂(H₂O)₄]; [M(HBDT)(OX)-(H₂O)], [Ni(BDT)(py)₂] _n and [Ni(BDT)(L)] _n where M = Mn^II, Ni^II and Cu^II; BDT = dithiocarbazate dianion; OX = 8-hydroxyquinolinate; x = 1 or 2; M = Zn^II or Cd^II; HBDT = dithiocarbazate anion and L = 2,2-bipyridyl or 1,10-o-phenanthroline. For the [M₂(BDT)(OX)₂] · xH₂O, [Co₂(BDT)(OX)₂(H₂O)₄], [Ni(BDT)(py)₂] _n and [Ni(BDT)(L)] _n complexes, benzoyldithiocarbazate acts as a dibasic-tetradentate ligand in the enol form via the enolic oxygen, the hydrazide nitrogens and the thiolate sulphur, while it acts as a monobasic-tridentate ligand in the keto form in the [M(HBDT)(OX)(H₂O)] complexes. The thermal behaviour of the complexes has been studied by t.g.–d.t.g. techniques. Kinetic parameters of the thermal decomposition process have been computed by Coats–Redfern and Horowitz–Metzger methods. It is obvious that the thermal decomposition in the complexes occurs directly at the metal–ligand bonds except for the Zn^II and Cd^II complexes in which decomposition seems to be at a point in the benzoyldithiocarbazate moiety. From the calculated kinetic data it can be concluded that the dehydration processes in all complexes have been described as phase-boundary controlled reactions. The activation energy values reveal that the thermal stabilities of the homobimetallic complexes lie in the order: Mn^II < Ni^II < Co^II, while the monomeric Cd^II complex has more enhanced thermal stability than the Zn^II complex.     

Synthesis,characterization, antimicrobial,and nuclease activity studies of some metal Schiff-base complexes

A Schiff base (L) is prepared by condensation of cuminaldehyde and L-histidine, and characterized by elemental analysis, IR, UV-Vis, ¹H-NMR, ¹³C-NMR, and mass spectra. Co(II), Ni(II), Cu(II), and Zn(II) complexes of this Schiff-base ligand are synthesized and characterized by elemental analysis, molar conductance, mass, IR, electronic spectra, magnetic moment, electron spin resonance (ESR), CV, TG/DTA, powder XRD, and SEM. The conductance data indicate that all the complexes are 1 : 1 electrolytes. IR data reveal that the Schiff base is a tridentate monobasic donor, coordinating through azomethine nitrogen, imidazole nitrogen, and carboxylato oxygen. The electronic spectral data and magnetic measurements suggest that Co(II) and Ni(II) complexes are tetrahedral, while Cu(II) complex has distorted square planar geometry. XRD and SEM show that Co(II), Cu(II), and Zn(II) complexes have crystalline nature, while the Ni(II) complex is amorphous and the particles are in nanocrystalline phase. The in vitro biological activities of the synthesized compounds were tested against the bacterial species, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, and Staphylococcus aureus; and fungal species, Aspergillus niger, Aspergillus flavus, and Candida albicans by the disc diffusion method. The biological study indicates that complexes exhibit more activity than the ligand. The nuclease activity of the ligand and its complexes are assayed on CT DNA using gel electrophoresis in the presence and the absence of H₂O₂. The Cu(II) complex shows increased nuclease activity in the presence of an oxidant when compared to the ligand, Co(II) and Ni(II) complexes.     

Synthesis,characterization, thermal,antimicrobial and antioxidant studies of some transition metal dithiocarbamates

Metal dithiocarbamate complexes of Co(II) [1], Cu(II) [2], Mn(II) [3], Cr(III) [4], and Pd(II) [5] have been synthesized using sodium N-ethyl-N-phenyldithiocarbamate (NaL). The complexes were characterized by elemental analyses, FTIR and UV–vis spectroscopic techniques, magnetic moment, molar conductance and thermal analyses (TGA and DSC). The infrared spectra indicated the coordination of dithiocarbamate through the two sulphur atoms in a symmetrical bidentate fashion. The thermal behavior of these complexes showed that the hydrated complexes lost water molecules in the first step, followed by decomposition of the ligand molecules in the final steps. Mass loss considerations at these final decomposition steps indicate conversion of the complexes to sulphides. The antimicrobial potentials of the complexes were evaluated against some selected bacteria strains (Escherichia coli, Pseudomonas aureginosa, Salmonella typhi and Staphylococcus aureus) and fungi organisms (Aspergillus flavus and Fasiparium oxysporium). The compounds showed a broad spectrum of fungicidal and bactericidal activities which exceeds that of the control drugs at a 100 μg/mL concentration. The antioxidant properties of the ligand and its Cu(II) complex were evaluated in vitro using DPPH assay, and the complex was found to exhibit better radical scavenging ability than the free ligand.     

Tetraaza macrocyclic complexes: synthesis,spectral and antimicrobial studies

A tetradentate nitrogen donor [N₄] macrocyclic ligand, 1,3,7,9-tetraaza-2,8-dithia-4,10-dimethyl-6,12-diphenylcyclododeca-4,6,10,12-tetraene has been synthesized by using thiourea and benzoylacetone. Complexes of Mn(II), Co(II), Ni(II), and Cu(II) have been synthesized with this ligand and characterized by element chemical analysis, molar conductance, magnetic susceptibility, mass, ¹H nuclear magnetic resonance, Fourier transform–infrared, electronic, and electron paramagnetic resonance spectral studies. The molar conductance measurements of Mn(II), Co(II), and Cu(II) complexes in dimethyformamide correspond to nonelectrolytes, whereas Ni(II) complex is a 1: 2 electrolyte. The complexes are high-spin except for Ni(II) which is diamagnetic. Octahedral geometry has been assigned for Mn(II) and Co(II) complexes, square planar for Ni(II) and tetragonal geometry for Cu(II). The ligand and its complexes were screened in vitro against two pathogenic fungi (Fusarium moniliformae and Rhizoctonia solani) and bacteria (Staphylococcus aureus and Pseudomonas aeruginosa) to assess their growth inhibiting potential.