Spectroscopic and electrochemical properties of nickel(II), iron(III) and cobalt(II) complexes with benzilbisthiosemicarbazone — importance of working conditions and the metal salt used in the final complex

Electrical semiconduction modulated by light in a cobalt and naphthalene diimide metal-organic framework

Metal-organic frameworks (MOFs) have emerged as an exciting class of porous materials that can be structurally designed by choosing particular components according to desired applications. Despite the wide interest in and many potential applications of MOFs, such as in gas storage, catalysis, sensing and drug delivery, electrical semiconductivity and its control is still rare. The use and fabrication of electronic devices with MOF-based components has not been widely explored, despite significant progress of these components made in recent years. Here we report the synthesis and properties of a new highly crystalline, electrochemically active, cobalt and naphthalene diimide-based MOF that is an efficient electrical semiconductor and has a broad absorption spectrum, from 300 to 2500 nm. Its semiconductivity was determined by direct voltage bias using a four-point device, and it features a wavelength dependant photoconductive-photoresistive dual behaviour, with a very high responsivity of 2.5 × 105 A W-1.

Impact and correlation of pKaand dnelectrons of some selected thiosemicarbazone Schiff base metal Co, Ni, Cu complexes: a study of electrochemical behavior, excitation and optical energies

The electron-transfer and coordination mechanism of thiosemicarbazone Schiff bases with metal ions (Co, Ni, Cu), correlation of the electrochemical and optical properties for their potential applications in various fields of chemistry and biochemistry are underexplored.

Synthesis of metal complexes involving Schiff base ligand with methylenedioxy moiety: spectral, thermal, XRD and antimicrobial studies

Metal complexes of Zn(II), Cd(II), Ni(II), Cu(II), Fe(III), Co(II), Mn(II) Hg(II), and Ag(I) have been synthesized from Schiff base ligand, prepared by the condensation of 3,4-(methylenedioxy)aniline and 5-bromo salicylaldehyde. All the compounds have been characterized by using elemental analysis, molar conductance, FT-IR, UV-Vis, (1)H NMR, (13)C NMR, mass spectra, powder XRD and thermal analysis (TG/DTA) technique. The elemental analysis suggests the stoichiometry to be 1:1 (metal:ligand). The FT-IR, (1)H NMR, (13)C NMR and UV-Vis spectral data suggest that the ligand coordinate to the metal atom by imino nitrogen and phenolic oxygen as bidentate manner. Mass spectral data further support the molecular mass of the compounds and their structure. Powder XRD indicates the crystalline state and morphology of the ligand and its metal complexes. The thermal behaviors of the complexes prove the presence of lattice as well as coordinated water molecules in the complexes. Melting point supports the thermal stability of all the compounds. The in vitro antimicrobial effects of the synthesized compounds were tested against five bacterial and three fungal species by well diffusion method. Antioxidant activities have also been performed for all the compounds. Metal complexes show more biological activity than the Schiff base.

Spectroscopic and biological approach in the characterization of a novel 14-membered [N4] macrocyclic ligand and its palladium(II), platinum(II), ruthenium(III) and iridium(III) complexes

A novel, tetradentate nitrogen donor [N4] macrocyclic ligand, i.e. 3,5,14,16-tetramethyl-2,6,13,17-tetraazatricyclo[12,0,0(7-12)] cosa-1(22),2,5,7,9,11,13,16,18,20-decaene(L), has been synthesized and characterized by elemental analyses, IR, Mass, and (1)H NMR spectral studies. Complexes of Pd(II), Pt(II), Ru(III) and Ir(III) have been prepared and characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, Mass, electronic spectral and thermal studies. On the basis of molar conductance the complexes may be formulated as [PdL]Cl2, [PtL]Cl2, [Ru(L)Cl2]Cl and [Ir(L)Cl2]Cl. The complexes are insoluble in most common solvents, including water, ethanol, carbon tetrachloride and acetonitrile, but soluble in DMF/DMSO. The value of magnetic moment indicates that all the complexes are diamagnetic except Ru(III) complex which shows magnetic moment corresponding to one unpaired electron. The magnetic moment of Ru(III) complex is 1.73 B.M. at room temperature. The antimicrobial activities of ligand and its complexes have been screened in vitro, as growth inhibiting agents. The antifungal and antibacterial screening were carried out using Food Poison and Disc Diffusion Method against plant pathogenic fungi and bacteria Alternaria porri, Fusarium oxysporum, Xanthomonas compestris and Pseudomonas aeruginosa respectively. The compounds were dissolved in DMSO to get the required solutions. The required medium used for these activities was PDA and nutrient agar.

Synthesis and thermal studies of tetraaza macrocylic ligand and its transition metal complexes. DNA binding affinity of copper complex

A Tetraaza Macrocylic Ligand (H2L) and its complexes, [Cd(H2L)(OH2)2](NO3)(2)·1/2OH2 (I), [Co(H2L)(OH2)](NO3)(2)·1/2OH2 (II), [Cu(H2L)(NO3)2]·3/2OH2 (III) and [Ni(H2L)(NO3)(OH2)]NO3·OH2 (IV), have been synthesized and characterized on the basis of elemental analysis, molar conductivity, 1H NMR, UV-vis, FT-IR and mass spectroscopy. All results confirm that the prepared compounds have 1:1 metal-to-ligand stoichiometry, octahedral configuration and the ligand behaves as a neutral tetradendate towards the metal ions. [CdL(OH2)2] (V), [CoL(OH2)2] (VI), [CuL(OH2)2] (VII) and [Ni(H2L)(NO3)2] (VIII) were synthesized pyrolytically in solid state from corresponding compounds (I-IV). Analytical results of complexes (V-VIII) show that the ligand behaves either as a neutral tetradendate or dianionic tetradentate ligand towards the metal ions. The binding of H2L and its copper complex (III) to DNA has been investigated by ultraviolet absorption spectroscopy. The experiments indicate that H2L and its copper complex (III) can bind to DNA through an intercalative mode. The H2L and its copper complex (III) exhibited anti-tumor activity against Ehrlich Acites Carcinoma (E.A.C) at the concentration of 100 μg/ml.

Spectroscopy: the study of DNA cleavage by newly synthesized polydentate macrocyclic ligand and its copper(II) complexes

A novel hexadentate nitrogen donor [N6] macrocyclic ligand, i.e. 2,6,12,16,21,22-hexaaza-3,5,13,15-tetramethyl-4,14-diethyl-tricyclo-[15.3.1.1(7-11)]docosane-1(21),2,5,7(22),8,10,12,15,17,19-decaene (L), has been synthesized. Copper(II) complexes with this ligand have been prepared and subjected to elemental analyses, molar conductance measurements, magnetic susceptibility measurements, mass, 1H NMR (ligand), IR, electronic, and EPR spectral studies. On the basis of molar conductance the complexes may be formulated as [Cu(L)X2] [X = Cl(-), Br(-), NO3(-) and CH3COO(-)] due to their nonelectrolytic nature in N,N'-dimethylformamide (DMF). All the complexes are of the high spin type and are six coordinated. On the basis of IR, electronic and EPR spectral studies tetragonal geometry has been assigned to the Cu(II) complexes. The interaction of these complexes with calf thymus DNA has been explored by using absorption, emission, viscosity measurements, electrochemical studies and DNA cleavage. All the experimental results suggest that the complexes bind to DNA and also promote the cleavage plasmid pBR 322, in the presence of H2O2 and ascorbic acid.

Spectroscopic characterization of chromium(III), manganese(II) and nickel(II) complexes with a nitrogen donor tetradentate, 12-membered azamacrocyclic ligand

The complexes of Cr(III), Mn(II) and Ni(II) were synthesized with macrocyclic ligand i.e. 5,11-dimethyl-6,12-diethyl-dione-1,2,4,7,9,10-hexazacyclododeca -1,4,6,10-tetraene. The ligand (L) was prepared by [2+2] condensation reaction of 2,3-pentanedione and semicarbazide hydrochloride. These complexes were found to have the general composition [Cr(L)X(2)]X and [M(L)X(2)] (where M=Mn(II) and Ni(II); X=Cl(-), NO(3)(-), (1/2)SO(4)(2-), NCS(-) and L=ligand [N(6)]). The ligand and its transition metal complexes were characterized by the elemental analysis, molar conductance, magnetic susceptibility, mass, IR, electronic and EPR spectral studies. On the basis of IR, electronic and EPR spectral studies, an octahedral geometry has been assigned for these complexes except sulphato complexes which are of five coordinated geometry.

The Spectroscopy: a modern technology in the characterization of novel macrocyclic ligand and its homo-bi-nuclear cobalt (II) complexes

A novel hexadentate nitrogen-sulphur donor [N(4)S(2)] macrocyclic ligand, i.e. 3,13-dithio-6,10,16,20-tetraoxo-8,18-dithia-1,2,4,5,11,12,14,15-octaazacyclocosane (L), has been synthesized. Cobalt (II) complexes of this ligand have been prepared and subjected to elemental analyses, molar conductance measurements, magnetic moment susceptibility measurements, mass, (1)H NMR (Ligand), IR, electronic, and EPR spectral studies. On the basis of molar conductance, complexes may be formulated as [Co(2)(L)X(2)]X(2) [where X=Cl(-), Br(-), NO(3)(-) and NCS(-)] due to their 1:2 electrolytic nature in dimethylformamide (DMF). All the complexes are of the high spin type and are four coordinated. On the basis of IR, electronic and EPR spectral studies tetrahedral geometry has been assigned to all the complexes. The antimicrobial activities of the ligand and its complexes, as growth inhibiting agents, have been screened in vitro against several species of bacteria and plant pathogenic fungi.

Synthesis, spectroscopic and thermal studies of transition metal complexes derived from benzil and diethylenetriamine

A macrocyclic ligand, bdta (where bdta=3,6,9,12,15,18-hexaaza-1,2,10,11-tetraphenyl-2,9,11,18-tetraenecyclododecane) has been prepared by cyclocondensation of benzil with diethylenetriamine which efficiently encapsulates transition as well as pseudo-transition metal ions leading to the formation of M(bdta)Cl2 type complexes [where M=Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II)]. The analytical, spectroscopic and magnetic moment data suggests an octahedral geometry for all the complexes. EPR spectra of Mn(II) and Cu(II) show considerable exchange interaction in the complex. They are non-conducting in DMSO. The TGA profile of the ligand and its complexes are identical and consists of two discreet stages. The voltammogram of Cu-complex exhibits a quasi-reversible one-electron transfer wave for Cu(II)/Cu(I) couple.

Manganese(II) complexes of substituted di-2-pyridyl ketone thiosemicarbazones: structural and spectral studies

The reaction between manganese(II) acetate and two substituted thiosemicarbazones derived from di-2-pyridyl ketone (HL) in 1:2 molar ratio produces new complexes of general formula [MnL2]. The thiosemicarbazone moiety in HL deprotonates and gets coordinated to Mn(II) through the azomethine nitrogen, one of the pyridyl nitrogens, and the thiolate sulfur in both the complexes. The crystal structure of [MnL2(1)] was established by single crystal X-ray diffraction and the compound crystallizes into a monoclinic lattice with P2(1)/c space group. Manganese(II) exists in a distorted octahedral geometry in the complexes.

Spectroscopic, cyclic voltammetric and biological studies of transition metal complexes with mixed nitrogen-sulphur (NS) donor macrocyclic ligand derived from thiosemicarbazide

The complexation of new mixed thia-aza-oxa macrocycle viz., 2,12-dithio-5,9,14,18-tetraoxo-7,16-dithia-1,3,4,10,11,13-hexaazacyclooctadecane containing thiosemicarba-zone unit with a series of transition metals Co(II), Ni(II) and Cu(II) has been investigated, by different spectroscopic techniques. The structural features of the ligand have been studied by EI-mass, (1)H NMR and IR spectral techniques. Elemental analyses, magnetic moment susceptibility, molar conductance, IR, electronic, and EPR spectral studies characterized the complexes. Electronic absorption and IR spectra of the complexes indicate octahedral geometry for chloro, nitrato, thiocyanato or acetato complexes. The dimeric and neutral nature of the sulphato complexes are confirmed from magnetic susceptibility and low conductance values. Electronic spectra suggests square-planar geometry for all sulphato complexes. The redox behaviour was studied by cyclic voltammetry, show metal-centered reduction processes for all complexes. The complexes of copper show both oxidation and reduction process. The redox potentials depend on the conformation of central atom in the macrocyclic complexes. Newly synthesized macrocyclic ligand and its transition metal complexes show markedly growth inhibitory activity against pathogenic bacterias and plant pathogenic fungi under study. Most of the complexes have higher activity than that of the metal free ligand.

Novel bidentate complexes of Cu(II) derived from 5-nitrofuran-2-carboxaldehyde thiosemicarbazones with antiamoebic activity against E. histolytica

The novel analogues of 5-nitrofuran-2-carboxaldehyde thiosemicarbazones 1-10 were synthesized and their copper(II) complexes 1a-10a were obtained by means of coordination with cupric chloride. All these compounds have been characterized by elemental analysis, IR, electronic spectra and thermogravimetric patterns while ligands have also been characterized by 1H NMR spectral studies. These copper complexes are bidentate and possess octahedral geometry around Cu(II) ion. Their antiamoebic activities were carried out to ascertain their effectiveness in comparison to their corresponding thiosemicarbazones. A number of these complexes possess noteworthy potencies towards HK-9 strain of Entamoeba histolytica in vitro. The complexes 2a-7a, 9a and 10a showed less IC50 value than metronidazole, the drug of choice for amoebiasis. Moreover, complexes 2a and 9a have shown the most promising antiamoebic activities (IC50 = 0.38 microM of 2a and IC50 = 0.34 microM of 9a versus IC50 = 1.81 microM of metronidazole). These results indicate that the metallated thiosemicarbazone may be lead molecule to inhibit growth of E. histolytica.

Metal complexes with Schiff-base ligands - pyridoxal and semicarbazide-based derivatives

The most important results of extensive studies (syntheses, spectral, magnetic, voltammetric and structural characteristics and biological activity) of metal complexes with pyridoxal semi-, thiosemi- and isothiosemicarbazones are reviewed.

Versatile Chelating Behavior of Benzil Bis(thiosemicarbazone) in Zinc, Cadmium, and Nickel Complexes

Reactions of benzil bis(thiosemicarbazone), LH(6), with M(NO(3))(2).nH(2)O (M = Zn, Cd, and Ni), in the presence of LiOH.H(2)O, show the versatile behavior of this molecule. The structure of the ligand, with the thiosemicarbazone moieties on opposite sides of the carbon backbone, changes to form complexes by acting as a chelating molecule. Complexes of these metal ions with empirical formula [MLH(4)] were obtained, although they show different molecular structures depending on their coordinating preferences. The zinc complex is the first example of a crystalline coordination polymer in which a bis(thiosemicarbazone) acts as bridging ligand, through a nitrogen atom, giving a 1D polymeric structure. The coordination sphere is formed by the imine nitrogen and sulfur atoms, and the remaining position, in a square-based pyramid, is occupied by an amine group of another ligand. The cadmium derivative shows the same geometry around the metal ion but consists of a dinuclear structure with sulfur atoms acting as a bridge between the metal ions. However, in the nickel complex LH(6) acts as a N(2)S(2) ligand yielding a planar structure for the nickel atom. The ligand and its complexes have been characterized by X-ray crystallography, microanalysis, mass spectrometry, IR, (1)H, and (13)C NMR spectroscopies and for the cadmium complex by (113)Cd NMR in solution and in the solid state.