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

Review on Isatin- A Remarkable Scaffold for Designing Potential Therapeutic Complexes and Its Macrocyclic Complexes with Transition Metals

Role of synthetic coordination chemistry in pharmaceutical science is expeditiously increased due to its sundry relevances in this field. The present review endows the synthesized macrocyclic complexes of transition metal ions containing isatin and its derivatives as ligand precursors, their characterization and their copious pharmaceutical applications. Isatin (1H-Indole-2,3-dione) is a protean compound (presence of lactam and keto moiety permits to change its molecular framework) that can be obtained from marine animals, plants, and is also found in mammalian tissues and in human fluids as a metabolite of amino acids. It can be used for the synthesis of miscellaneous organic and inorganic complexes and for designing of drugs since it has remarkable utility in pharmaceutical industry due to its wide range of biological and pharmacological activities, for instance anti-microbial, anti-HIV, anti-tubercular, anti-cancer, anti-viral, anti-oxidant, anti-inflammatory, anti-angiogenic, analgesic activity, anti-Parkinson's disease, anti-convulsant etc. This review provides extensive information about the latest methods for the synthesis of isatin or its substituted derivatives based macrocyclic complexes of transition metals and their plentiful applications in medicinal chemistry.

Graphical Abstract

The energy gap law for NIR-phosphorescent Cr(III) complexes

A series of homoleptic Cr(III) complexes containing substituted anionic 1,3-bis(pyridin-2-ylimino)isoindolin-2-ide ligands are phosphorescent with λ_max in the 777-970 nm range in degassed fluid solutions. The energy gap law has been successfully applied to the doublet excited states of Cr(III) complexes.

In Vitro Synthesis, Structure elucidation and its antioxidant properties of Platinum(IV)-hydrazide complexes: Molecular modeling of free-hydrazides suggested as potent lipoxygenase inhibitor

BACKGROUND

Combination of biologically active ligand and metal in one molecule may increase the activity and reduce the toxicity.

OBJECTIVES

In this study synthesis and characterization of platinum(IV) complexes with bioactive hydrazide ligands is discussed.

METHOD

Elemental analysis, conductivity measurements and spectroscopic studies were used to elucidate the structure of complexes.

RESULTS

Our study suggests that hydrazide ligands coordinate with Pt(IV) in bidenate fashion. The platinum(IV) complexes have octahedral geometry with metal to ligand ratio of 1:2. Hydrazide ligands coordinated with central metal platinum(IV) by oxygen of carbonyl group and nitrogen of primary amine. Synthesized complexes exhibited variable DPPH radical scavenging and lipoxygenase inhibition activity. Furthermore, it is also found that Pt(IV)-hydrazide complexes are more potent superoxide and nitric oxide radical scavengers than their uncoordinated hydrazide ligands while in case of lipoxygenase enzyme inhibition, some of the free hydrazide ligands are more active than their respective Pt(IV) complexes. In silico docking technique explores molecular interactions of synthesized ligands in the active site of lipoxygenase enzyme. Predicted docking energies are in good agreement with experimental data suggesting that in silico studies might be useful for discovery of therapeutic candidates.

CONCLUSION

Structure function relationship demonstrates that the radical scavenging and enzyme inhibition activities of the Pt(IV) compounds are effected by nature of ligand, position of substituent, electronic and steric effects. However, electronic factor seem to play more important role than other factors.

New 15-membered tetraaza (N4) macrocyclic ligand and its transition metal complexes: spectral, magnetic, thermal and anticancer activity

Novel tetraamidemacrocyclic 15-membered ligand [L] i.e. naphthyl-dibenzo[1,5,9,12]tetraazacyclopentadecine-6,10,11,15-tetraoneand its transition metal complexes with Fe(II), Co(II), Ni(II), Cu(II), Ru(III) and Pd(II) have been synthesized and characterized by elemental analysis, spectral, thermal as well as magnetic and molar conductivity measurements. On the basis of analytical, spectral (IR, MS, UV-Vis, (1)H NMR and EPR) and thermal studies distorted octahedral or square planar geometry has been proposed for the complexes. The antitumor activity of the synthesized ligand and some complexes against human breast cancer cell lines (MCF-7) and human hepatocarcinoma cell lines (HepG2) has been studied. The complexes (IC50=2.27-2.7, 8.33-31.1μg/mL, respectively) showed potent antitumor activity, towards the former cell lines comparable with their ligand (IC50=13, 26μg/mL, respectively). The results show that the activity of the ligand towards breast cancer cell line becomes more pronounced and significant when coordinated to the metal ion.

Synthesis, spectroscopic characterization, molecular modeling and antimicrobial activities of Mn(II), Co(II), Ni(II), Cu(II) complexes containing the tetradentate aza Schiff base ligand

Mn(II), Co(II), Ni(II), and Cu(II) complexes with a tetradentate macrocyclic ligand [1.2.5.6tetraoxo-3,4,7,8tetraaza-(1,2,3,4,5,6,7,8)tetrabenzene(L)] were synthesized and characterized by elemental analysis, molar conductance measurements, mass, nmr, i.r., electronic and e.p.r. spectral studies. All the complexes are non electrolytes in nature and may be formulated as [M(L)X(2)] [where, M=Mn(II), Co(II), Ni(II), Cu(II) and X=Cl(-), CH(3)COO(-)]. On the basis of i.r., electronic and e.p.r. spectral studies a distorted octahedral geometry has been assigned for all complexes. The antimicrobial activities and LD(50) values of the ligand and its complexes, as growth inhibiting agents, have been screened in vitro against two different species of bacteria and plant pathogenic fungi.

Spectral, thermal and morphological studies of chromium nanoparticles

Cr(0) nanoparticles were synthesized by solution reduction process successfully. The influence of parameters on the size of Cr(0) nanoparticles was studied and the referential process parameters were obtained. The morphology and structure of the synthesized Cr(0) nanoparticles were characterized by Transmission Electron Microscopy (TEM), Powder X-ray Diffraction (XRD), Thermal Gravimetric Analysis (TGA), QELS Data and Infrared Spectroscopy (IR). The results show that Cr(0) nanoparticles are of high purity. XRD analysis revealed all relevant Bragg's reflection for crystal structure of Cr metal. XRD spectrum also indicates that there is no oxidation of Cr(0) nanoparticles to chromium oxide. TEM showed nearly uniform distribution of particles in methanol which was confirmed by QELS. Cr(0) nanoparticles can be synthesized easily by reducing agent and are quite stable too.

Template synthesis and spectral studies on mononuclear complexes of chromium(III) and manganese(II) with tetradentate N4 donor macrocycles

The present article deals with the synthesis, spectral characterization and antimicrobial activity of a series of new complexes of chromium(III) and manganese(II)of general formula [Cr(Macn)Cl2]·Cl and [Mn(Macn)Cl2] respectively. These complexes were prepared via template reaction by mixing methanolic solution of diacetyldihydrazone, diacids (oxalic acid, succinic acid, glutaric acid and adipic acid) with CrCl3·6H2O and MnCl2·4H2O in 2:2:1 M ratios respectively. The newly synthesized complexes were characterized on the basis of chemical analysis and spectral studies like IR, UV, ESR and X-ray diffraction. An octahedral structure has been proposed for the chromium(III) and manganese(II)macrocyclic complexes. The synthesized complexes were further tested in vitro against fungi and bacteria in order to assess their antibacterial and antifungal activities. The studies demonstrate that the complexes possess antimicrobial properties.

Synthesis, DNA-binding, DNA-photonuclease profiling and antimicrobial activity of novel tetra-aza macrocyclic Ni(II), Co(II) and Cu(II) complexes constrained by thiadiazole

A new tetra-aza macrocyclic ligand, L (C(24)H(16)N(12)O(2)S(4)) and its complexes of type, [MLCl(2)] and [CuL]Cl(2) (where M=Ni(II), Co(II); L=N,N'-(benzene-1,3-diyldi-1,3,4-thiadiazole-5,2-diyl)bis{2-[(5-benzene-1,3-diyl-1,3,4-thiadiazol-2-yl)amino]acetamide}) were synthesized and characterized by the spectral and analytical techniques. An octahedral geometry has been proposed for Ni(II) and Co(II) complexes while Cu(II) complex exhibit a square planar geometry. All the synthesized metal complexes were screened for their in vitro antimicrobial activity against selected species of pathogenic bacteria and fungi. The binding property of the complexes with CT-DNA was studied by absorption spectral analysis, followed by viscosity measurement and thermal denaturation studies. The photo induced cleavage studies revealed that the complexes possess photonuclease property against pUC19 DNA under UV-visible irradiation.

Synthesis of Al nanoparticles: transmission electron microscopy, thermal and spectral studies

Nanoparticles of Al(0) were synthesized by solution reduction process successfully. The influence of parameters on the size of Al(0) nanoparticles were studied and the referential process parameters were obtained. The morphology and structure of the synthesized Al(0) nanoparticles were characterized by Transmission Electron Microscopy (TEM), Powder X-ray Diffraction (XRD), Thermal Gravimetric Analysis (TGA), QELS Data and Infrared Spectroscopy (IR). The results show that nanoparticles of Al(0) are of high purity. XRD analysis revealed all relevant Bragg's reflection for crystal structure of Al metal. XRD spectrum also indicates there is no oxidation of Al(0) nanoparticles to aluminum oxide. TEM showed nearly uniform distribution of the particles in methanol and it was confirmed by QELS. Al(0) nanoparticles can be synthesized easily by reducing agent and are quite stable too.

Spectroscopic studies and antibacterial activities of some new 16-membered octaazamacrocyclic complexes derived from thiocarbohydrazide and pentane-2,4-dione

A series of macrocyclic complexes of the type [M(C12H20N8S2)X2]; where M=Co(II), Ni(II), Cu(II), Zn(II); X=Cl-, NO3-, CH3COO- has been synthesized by template condensation of thiocarbohydrazide and pentane-2,4-dione in the presence of divalent metal salts in methanolic medium. The complexes have been characterized with the help of elemental analyses, conductance measurements, magnetic measurements, electronic, NMR, IR, EPR and MS spectral studies. The low value of molar conductance indicates them to be non-electrolytes. On the basis of various studies a distorted octahedral geometry may be proposed for all of these complexes. These metal complexes were also tested for their in vitro antibacterial activities against some Gram-positive bacterial strains, i.e., Bacillus subtilis, Bacillus stearothermophilus and two Gram-negative bacterial strains, i.e., Escherichia coli, Pseudomonas putida. The results obtained were compared with standard antibiotics, Chloramphenicol and Streptomycin and found that some of the synthesized complexes show good antibacterial activities as compared to the standard antibiotics.

Macrocyclic complexes: Synthesis and characterization

A novel series of complexes of the type [M(C28H24N4)X]X2, where M = Cr(III), Fe(III) or Mn(III), X = Cl?, NO3 ?, CH3COO? and (C28H24N4) corresponds to the tetradentate macrocyclic ligand, were synthesized in methanolic media by the template condensation of 1,8-diaminonaphthalene and 2,3- butanedione (diacetyl) in the presence of trivalent metal salts. The complexes were characterized by elemental analyses, conductance and magnetic measurements, and UV/Vis, NMR and IR spectroscopy. Based on these studies, a five-coordinate square pyramidal geometry for all the prepared complexes is proposed. All the synthesized macrocyclic complexes were tested for their in vitro antifungal activity against some fungal strains viz. Aspergillus niger and A. fumigatus. The results obtained were compared with the standard antifungal drug fluconazole.

New 14-membered octaazamacrocyclic complexes of divalent transition metal ions with their antimicrobial and spectral studies

A novel series of macrocyclic complexes of the type [M(C(18)H(14)N(10)S(2))X(2)]; where M=Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); X=Cl(-), NO(3)(-), CH(3)COO(-) has been synthesized by [2+2] condensation of thiocarbohydrazide and isatin in the presence of divalent metal salts in methanolic medium. The complexes have been characterized with the help of elemental analyses, conductance measurements, magnetic measurements, electronic, NMR and infrared spectral studies. The low value of molar conductance indicates them to be non-electrolytes. On the basis of various studies a distorted octahedral geometry may be proposed for all of these complexes. These metal complexes were also tested for their in vitro antimicrobial activities against some Gram-positive bacteria viz. Staphylococcus aureus, Bacillus subtilis, and some Gram-negative bacteria Escherichia coli, Pseudomonas aeruginosa and some fungal strains Aspergillus niger, Aspergillus flavus (molds), Candida albicans, Saccharomyces cerevisiae (yeasts). The results obtained were compared with standard antibiotic: Ciprofloxacin and the standard antifungal drug: Amphotericin-B.

Synthesis, spectral investigation and thermal aspects of coordination polymeric chain assemblies of some transition metal ions with bis-pyrazolones

A few coordination chain polymeric assemblies of the type [M(SB)(H(2)O)(2)](n).xH(2)O or [VO(SB)(H(2)O)](n).H(2)O [where M=Mn(II), Cu(II) and Zn(II), x=1; Co(II) and Ni(II) x=2, H(2)SB=(4Z,4'Z)-4,4'-(2,2'-(4,4'-methylenebis(4,1-phenylene)bis(azanediyl))bis(1-hydroxy ethan-2-yl-1-ylidene))bis(3-methyl-1-phenyl-1H-pyrazol-5(4H)-one)] have been investigated. Structural and spectroscopic properties have been studied on the basis of elemental analyses, infrared spectra, (1)H and (13)C NMR spectra, electronic spectra, magnetic measurements and thermo gravimetric analyses. FT-IR, (1)H and (13)C NMR studies reveal that the ligand (H(2)SB) exists in the tautomeric enol form in both the states with intramolecular hydrogen bonding. Magnetic moment and reflectance spectral studies reveal that an octahedral geometry has been assigned to all the prepared coordination polymers. The kinetic parameters such as order of reaction (n) and the energy of activation (E(a)) have been reported using Freeman-Carroll method. The pre-exponential factor (A), the activation entropy (DeltaS(#)), the activation enthalpy (DeltaH(#)) and the free energy of activation (DeltaG(#)) have been calculated.