Structural and Spectral Investigations of Transition Metal Complexes Of Di-2-Pyridyl Ketone N (4), N (4)-Disubstituted Thiosemicarbazones

The study deals with structural and spectral investigations of transition metal complexes of di-2-pyridyl ketone N(4),N(4)-disubstituted thiosemicarbazones. The main objective and scope of the work deals with di-2-pyridyl ketone N(4),N(4)-disubstituted thiosemicarbazones are quardridentate NNNS donor ligands. To chosen this ligand for study because, the ligands are prepared and characterized for the first time, since there are two pyridyl nitorgens, dimmers and polymers of complexes may result leading to interesting structural aspects. The work includes the preparation of the thiosemicarbzones and their structural and spectral studies, synthesis and spectral characterization of complexes of copper(II),,nickel(II),manganese(II), dioxovanadium(V),cobalt(III),zinc(II),cadmium(II) of the ligand HL, synthesis and spectral characterization of complexes of copper(II),manganese(II), of the ligand HL and the development of X-ray quality crystals and its X-ray diffraction studies. The structural characterization techniques are elemental analysis, conductivity measurements, magnetic measurements, electronic spectroscopy, H NMR spectroscopy, Infrared spectroscopy and X-ray crystallography.

Copper(II) complexes of N(4)-substituted thiosemicarbazones derived from pyridine-2-carbaldehyde: Crystal structure of a binuclear complex

Ten copper(II) complexes {[CuL1Cl] (1), [CuL1NO3]2 (2), [CuL1N3]2 · 2/3H2O (3), [CuL1]2(ClO4)2 · 2H2O (4), [CuL2Cl]2 (5), [CuL2N3] (6), [Cu(HL2)SO4]2 · 4H2O (7), [Cu(HL2)2] (ClO4)2 · 1/2EtOH (8), [CuL3Cl]2 (9), [CuL3NCS] · 1/2H2O (10)} of three NNS donor thiosemicarbazone ligands {pyridine-2-carbaldehyde-N(4)-p-methoxyphenyl thiosemicarbazone [HL1], pyridine-2-carbaldehyde-N(4)-2-phenethyl thiosemicarbazone [HL2] and pyridine-2-carbaldehyde N(4)-(methyl), N(4)-(phenyl) thiosemicarbazone [HL3]} were synthesized and physico-chemically characterized. The crystal structure of compound 9 has been determined by X-ray diffraction studies and is found that the dimer consists of two square pyramidal Cu(II) centers linked by two chlorine atoms.

Structural and spectral studies of novel Co(III) complexes of N(4)-substituted thiosemicarbazones derived from pyridine-2-carbaldehyde

Seven bis(ligand) Co(III) complexes {[CoL21] NO3 · H2 O (1), [CoL21] Cl · 2 H2 O (2),[CoL21] ClO4 (3), [CoL22] NO3 (4), [CoL22] Cl · 2 H2 O (5), [CoL23] Br · 2 H2 O (6), [CoL23] ClO4 · H2 O (7)} of three thiosemicarbazone ligands {pyridine-2-carbaldehyde-N(4)-p-methoxyphenyl thiosemicarbazone [HL1], pyridine-2-carbaldehyde-N(4)-2-phenylethyl thiosemicarbazone [HL2] and pyridine-2-carbaldehyde-N(4)-(methyl),N(4)-(phenyl) thiosemicarbazone [HL3]} were synthesized and physico-chemically characterized. All complexes are assigned octahedral geometries on the basis of spectral studies. The ligands deprotonate and coordinate by means of pyridine nitrogen, azomethine nitrogen, and thiolate sulfur atoms. The single crystal X-ray structures of HL3 and two nitrate compounds are discussed. The structural studies corroborate the spectral characterization.

Spectral and structural studies of mono- and binuclear copper(II) complexes of salicylaldehyde N(4)-substituted thiosemicarbazones

Three copper(II) complexes of salicylaldehyde N(4)-phenyl thiosemicarbazone (H2L1) and two copper(II) complexes of N(4)-cyclohexyl thiosemicarbazone (H2L2) have been synthesized and characterized by different physicochemical techniques like magnetic studies and electronic, infrared and EPR spectral studies. The complexes View the MathML source and [(CuL2)2] (4) having dimeric structure. The thiosemicarbazones bind to the metal as dianionic ONS donor ligand in all the complexes, except in the complex [Cu(HL1)2] · H2O (2). In complex 2, the ligand moieties are coordinated as monoanionic (HL−) ones. Two of the complexes [CuL1dmbipy] · H2O (3) and [CuL2dmbipy] (5) have been found to possess the stoichiometry [CuLB], where B = 4,4′-dimethyl-2,2′-bipyridine (dmbipy). The coordination geometry around copper(II) in 5 is trigonal bipyramidal distorted square based pyramidal (TBDSBP), as obtained by X-ray diffraction studies.

Structural, EPR and Antimicrobial Studies on Some Transition Metal Complexes of Thiosemicarbazones

Department of Applied chemistry, Cochin University of Science and Technology

Structural and biological investigations of metal complexes of some substituted thiosemicarbazones

Department of Applied Chemistry, Cochin University of Science and Technology

Transition metal complexes of some bis(thiosemicarbazones) derived from 2,6-diacetylpyridine and N4-substituted thiosemicarbazides:Synthesis, spectral and structural studies

Coordination chemistry of pentadentate 2,6-diacetylpyridine bis(thiosemicarbazone) Schiff base ligands has been intensively studied due to the versatility of the molecular chain in order to obtain very different geometries as well as their broad therapeutic activity. Metal complexes of thiosemicarbazone with aldehydes and ketones have been widely reported. But there have been fewer reports on potential pentadentate bis(thiosemicarbazones) formed from 2,6-diacetylpyridine. Keeping these in view, we have synthesized four bis(thiosemicarbazone) systems with 2,6-diacetylpyridine. In the present work, the chelating behavior of bis(thiosemicarbazones) are studied, with the aim of investigating the influence of coordination exerts on their conformation and or configuration, in connection with the nature of the metal and of the counter ion. The selection of the 2,6-diacetylpyridine as the ketonic part was based on its capability to form polynuclear complexes with different coordination number. The doubled armed bis(thiosemicarbazones) can coordinate to a metal centre as dianionic ligand by losing its amide protons or it can coordinate as monoanionic ligand by losing its amide proton from one of the thiosemicarbazone moiety or it can also be coordinate as neutral ligand. Hence it is interesting to explore the coordinating capabilities of these ligands whether in neutral form or anionic form and to study the structural variations occurring in the ligands during complexation such as change in conformation.

Transition Metal Complexes with Ring Incorporated Thiosemicarbazones: Syntheses,Structures and Spectral Properties

In the present work,the chelating behaviour of thiosemicarbazones of a heterocyclic diketone, 2,6-diacetylpyridine is studied,with the aim of investigating the influence coordination exerts on their conformation and /or configuration, in connection with the nature of the metal and of the counter ion.The various possibilities like unsubstitution,ring incorporation at terminal nitrogen and condensation of one of the ketone group alone have been tried for ligand selection.Mainly first row transition metals like manganese,iron,nickel,copper,zinc and cadmium are studied.Metals like cobalt also were studied but could not result in fruitful isolation of the compound due to solubility problems.Different spectroscopic and characterization techniques have been utilized to reveal the nature of the metal and the ligands in coordinated metal complex.

Spectral and Structural Studies of Transition Metal Complexes of Thiosemicarbazones Containing Ring Incorporated at N(4)-position

The thesis is an introduction to evaluate the coordination behaviour of a few compounds of our interest. The crucial aim of these investigations was to synthesize and characterize some transition metal complexes using the ligands benzaldehyde, 2-hydroxybenzaldehyde and 4-methoxybenzaldehyde N(4)-ring incorporated thiosemicarbazones.The study involves a brief foreword of the metal complexes of thiosemicarbazones including their bonding, stereochemistry and biological activities.The different analytical and spectroscopic techniques used for the analysis of the ligands and their complexes are discussed.It also deals with the synthesis and spectral characterization of the thiosemicarbazones and single crystal X-ray diffraction study of one of them.Chapter 3 describes the synthesis, spectral characterization, single crystal X-ray diffraction studies of copper(ll) complexes with ONS/NS donor thiosemicarbazones. Chapter 4 deals with the synthesis, spectral characterization and single crystal X-ray diffraction studies of nickel(II) complexes. Chapter 5 contains the synthesis, structural and spectral characterization of the cobalt(III) complexes. Chapters 6 and 7 include the synthesis, structural and spectral characterization of zinc(II) and cadmium(ll) complexes with ONS/NS donor thiosemicarbazones.

Transition metal complexes derived from ketone based N(4)-substituted thiosemicarbazones: Crystal structures and spectral studies

Thiosemicarbazones have recently attracted considerable attention due to their ability to form tridentate chelates with transition metal ions through either two nitrogen and sulfur atoms, N–N–S or oxygen, nitrogen and sulfur atoms, O–N–S. Considerable interest in thiosemicarbazones and their transition metal complexes has also grown in the areas of biology and chemistry due to biological activities such as antitumoral, fungicidal, bactericidal, antiviral and nonlinear optical properties. They have been used for metal analyses, for device applications related to telecommunications, optical computing, storage and information processing.The versatile applications of metal complexes of thiosemicarbazones in various fields prompted us to synthesize the tridentate NNS-donor thiosemicarbazones and their metal complexes. As a part of our studies on transition metal complexes with these ligands, the researcher undertook the current work with the following objectives. 1. To synthesize and physico-chemically characterize the following thiosemicarbazone ligands: a. Di-2-pyridyl ketone-N(4)-methyl thiosemicarbazone (HDpyMeTsc) b. Di-2-pyridyl ketone-N(4)-ethyl thiosemicarbazone (HDpyETsc) 2. To synthesize oxovanadium(IV), manganese(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes using the synthesized thiosemicarbazones as principal ligands and some anionic coligands. 3. To study the coordination modes of the ligands in metal complexes by using different physicochemical methods like partial elemental analysis, thermogravimetry and by different spectroscopic techniques. 4. To establish the structure of compounds by single crystal XRD studies

Crystal Structures and Spectral Aspects of Mixed Ligand Transition Metal Chelates Derived from Aldehyde based ONS Donor Thiosemicarbazones

Thiosemicarbazones have emerged as an important class of ligands over a period of time, for a variety of reasons, such as variable donor properties, structural diversity and biological applications. Interesting as the coordination chemistry may be, the driving force for the study of these ligands has undoubtedly been their biological properties and the majority of the 3000 or so publications on thiosemicarbazones since 2000 have alluded to this feature. Thiosemicarbazones with potential donor atoms in their structural skeleton fascinate coordination chemists with their versatile chelating behavior. The thiosemicarbazones of aromatic aldehydes and ketones form stable chelates with transition metal cations by utilizing both their sulfur and azomethine nitrogen as donor atoms. They have been shown to possess a diverse range of biological activities including anticancer, antitumor, antibacterial, antiviral, antimalarial and antifungal properties owing to their ability to diffuse through the semipermeable membrane of the cell lines. The enhanced effect may be attributed to the increased lipophilicity of the metal complexes compared to the ligand alone.

Spectral, Structural And Biological Studies Of Some Metal Complexes Of ‘Nsubstituted 2-Benzoylpyridine Thiosemicarbazones

Aqua complex ions of metals must have existed since the appearance of water on the earth, and the subsequent appearance of life depended on, and may even have resulted from the interaction of metal ions with organic molecules. Studies on the coordinating ability of metal ions with other molecules and anions culminated in the theories of/\lfred Werner. Thereon the progress in the studies of metal complex chemistry was rapid. Many factors, like the utility and economic importance of metal chemistry, the intrinsic interest _in many of the compounds and the intellectual challenge of the structural problems to be solved, have contributed to this rapid progress. X—ray diffraction studies further accelerated the progress. The work cited in this thesis was carried out by the author in the Department of Applied Chemistry during 2001-2004. The primary aim of these investigations was to synthesise and characterize some transition metal complexes of 2-benzoylpyridine N(4)-substituted thiosemicarbazones and to study the antimicrobial activities of the ligands and their metal complexes. The work is divided into eight chapters

Synthesis and spectral investigations of Mn(II) complexes of pentadentate bis(thiosemicarbazones)

Five Mn(II) complexes of bis(thiosemicarbazones) which are represented as [Mn(H2Ac4Ph)Cl2] (1), [Mn(Ac4Ph)H2O] (2), [Mn(H2Ac4Cy)Cl2]·H2O (3), [Mn(H2Ac4Et)Cl2]·3H2O (4) and [Mn(H2Ac4Et)(OAc)2]·3H2O (5) have been synthesized and characterized by elemental analyses, electronic, infrared and EPR spectral techniques. In all the complexes except [Mn(Ac4Ph)H2O], the ligands act as pentadentate neutral molecules and coordinate to Mn(II) ion through two thione sulfur atoms, two azomethine nitrogens and the pyridine nitrogen, suggesting a heptacoordination. While in compound [Mn(Ac4Ph)H2O], the dianionic ligand is coordinated to the metal suggesting six coordination in this case. Magnetic studies indicate the high spin state of Mn(II). Conductivity measurements reveal their non-electrolyte nature. EPR studies indicate five g values for [Mn(Ac4Ph)H2O] showing zero field splitting.

Structural, Spectral, Biological and Electrochemical Studies Of Some 3d Transition Metal Complexes of O-N-S and N-N-S Donor Ligands

The primary aim of these investigations was to probe the spectroscopic, electrochemical, biological and single crystal X-ray diffraction studies of some selected transition metal complexes of 4N-monosubstituted thiosemicarbazones. Transition metal complexes with thiosemicarbazones exhibit a wide range of stereochemistries and possess potential biological activity. Metal complexes of thiosemicarbazones are proved to have improved pharmacological and therapeutic effects. The studies are conducted to bring about a fair understanding of the structure activity relationship and to develop certain effective and economical metal-based antimicrobial agents. Study showed that the thiosemicarbazones have antibacterial, antiviral and antiproliferative properties and hence used against tuberculosis, leprosy, psoriasis, rheumatism, trypanosomiasis and coccidiosis. Certain thiosemicarbazones showed a selective inhibition of HSV and HIV infections. The insolubility of most thiosemicarbazones in water causes difficulty in the oral administration in clinical practice. Transition metal complexes are found to have more activity than uncombined thiosemicarbazones. They exhibit a variety of denticity and can be varied by proper substitution. The stereochemistry assumed by the thiosemicarbazones during the coordination with transition metal ions depends on the factors such as preparative conditions and availability of additional bonding site in the ligand moiety and charge of the ligand. The resulting complexes exhibited a wide range of stereochemistries and have biomimic activity and potential application as sensors.

Diversity in Structural and Spectural Characteristics of Some Transition Metal Complexes Derived From Aldehyde Based Thiosemicarbazone Ligands

The study deals with the diversity in structural and spectural characteristics of some transition metal complexes derived from aldehyde based thiosemicarbazone ligands thiosemicarbazones are a family of compounds with beneficial biological activity viz., anticancer,antitumour, antifungal, antibacterial, antimalarial, antifilarial, antiviral and anti-HIV activities. Many thiosemicarbazone ligands and their complexes have been prepared and screened for their antimicrobial activity against various types of fungi and bacteria. The results prove that the compounds exhibit antimicrobial properties and it is important to note that in some cases metal chelates show more inhibitory effects than the parent ligands. The increased lipophilicity of these complexes seems to be responsible for their enhanced biological potency. Adverse biological activities of thiosemicarbazones have been widely studied in rats and in other species. The parameters measured show that copper complexes caused considerable oxidative stress and zinc zinc complexes behaved as antioxidants. It has applications on analytical field also. Some thiosemicarbazones produce highly colored complexes with metal ions. This thesis aims to synthesis some novel thiosemicarbazone ligands and their transition metal complexes together with their physico-chemical characterization.