An EPR study of some copper(II) coordination compounds of substituted biguanides. Part IV

l-Isoleucine-Schiff Base Copper(II) Coordination Polymers: Crystal Structure, Spectroscopic, Hirshfeld Surface, and DFT Analyses

A new copper(II) coordination polymer was synthesized from the l-isoleucine-Schiff base and characterized by elemental analysis, Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, single-crystal X-ray diffraction (XRD) analysis, electronic paramagnetic resonance, and thermogravimetric analysis. XRD analysis confirmed the square planar coordination geometry of metallic centers and a zipper-like polymer structure. Vibrational, electronic, and paramagnetic spectroscopies and thermal analysis were consistent with the crystal structure. A Hirshfeld surface (HS) and density functional theory (DFT) analyses were employed to gain additional insight into interactions responsible for complex packing. The quantitative examination of two-dimensional (2D) fingerprint plots revealed, among other van der Waals forces, the dominating participation of H···H and H···Cl interactions in the molecular packing. The use of computational methods provided great help in detailing the supramolecular interactions occurring in the crystal, which were mainly van der Waals attractions. The electronic transition analysis helped corroborate the electronic transitions observed experimentally in the absorption spectrum. The frequency and vibrational mode analysis gave a deeper insight into the characterization of the CuL_CL complex.

Synthesis, Characterisation and Antimicrobial Activity of Manganese(II), nickel(II), cobalt(II), Copper(II) and Zinc(II) Complexes of a Binucleating Tetradentate Ligand

The binucleating, tetradentate Schiff base ligand (H2L) has been synthesised by condensation of bis-(4-aminophenyl)-methane with salicyladehyde. The resulting metal(II) complexes [metal = Mn||, Ni||, Co||, Cu|| and Zn||] have been characterised by elemental analyses, molar conductances, magnetic moment, IR, UV-vis spectra, thermal analyses (DTA and TGA) and ESR spectra. Antimicrobial activities of the ligand and its metal(II) complexes have been tested against different microorganisms. The electrochemical data of complexes (2), (9) and (10) are discussed.

Cytotoxic behavior and spectroscopic characterization of metal complexes of ethylacetoacetate bis(thiosemicarbazone) ligand

Reaction of Cr(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) ion with 2,4-dihydrazino-thioamido-1-ethoxybutane led to the formation of mono and binuclear complexes. These complexes have been characterized by elemental analyses, IR, UV-Vis spectra, magnetic moments, molar conductances, (1)H NMR and mass spectra (ligand and its Zn(II) complex), thermal analyses (DTA and TGA) and ESR measurements. The IR data suggest the involvement of sulfur and azomethane nitrogen atoms in coordination to the central metal ion .The Molar conductances of the complexes in DMF are commensurate with their non-ionic character. The ESR spectra of Cu(II) complexes show axial type symmetry (d(x2-y2)) ground state with covalent bond character. On the basis of spectral studies, octahedral or tetrahedral geometry has been assigned to the metal complexes. Complexes have been tested invitro against tumor cells and number of microorganisms in order to assess their antitumor and antimicrobial properties.

Molecular mechanism of action of metformin: old or new insights?

Metformin is the first-line drug treatment for type 2 diabetes. Globally, over 100 million patients are prescribed this drug annually. Metformin was discovered before the era of target-based drug discovery and its molecular mechanism of action remains an area of vigorous diabetes research. An improvement in our understanding of metformin's molecular targets is likely to enable target-based identification of second-generation drugs with similar properties, a development that has been impossible up to now. The notion that 5' AMP-activated protein kinase (AMPK) mediates the anti-hyperglycaemic action of metformin has recently been challenged by genetic loss-of-function studies, thrusting the AMPK-independent effects of the drug into the spotlight for the first time in more than a decade. Key AMPK-independent effects of the drug include the mitochondrial actions that have been known for many years and which are still thought to be the primary site of action of metformin. Coupled with recent evidence of AMPK-independent effects on the counter-regulatory hormone glucagon, new paradigms of AMPK-independent drug action are beginning to take shape. In this review we summarise the recent research developments on the molecular action of metformin.

Preparation, spectroscopic investigation and antiproliferative capacity of new metal complexes of (3E)-2-(hydroxyimino)-N-P-Tolyl-3-(P-tolylimino) butanamide

Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Sr(II), Hg(II), Tl(I), UO(2)(II) and ZrO(II) complexes of (3E)-2-(hydroxyimino)-N-P-Tolyl-3-(P-tolylimino) butanamide have been prepared and characterized by elemental analyses, IR, UV-Vis spectra, magnetic moments, conductances, (1)H NMR and mass spectra (ligand and its Zn(II) complex), thermal analyses (DTA and TGA) and ESR measurements. The IR data show that, the ligand behaves as monobasic bidentate or neutral bidentate. Molar conductances in DMF indicate that, the complexes are non-electrolytes. ESR spectra of solid Cu(II) complexes at room temperature show axial type (d(x)(2-)(y)(2)) with covalent bond character in an octahedral environment. Complexes showed inhibitory activity against hepatocellular carcinoma (HepG-2 cell line).

Elaborated studies for the ligitional behavior of thiouracil derivative towards Ni(II), Pd(II), Pt(IV), Cu(II) and UO2 ² ions

A synthesis of new thiouracil derivative was carried out and deliberately investigated. A new series of complexes was prepared using Ni(II), Pd(II), Pt(IV), Cu(II) and UO(2)(+2) ions. IR spectral data proposed the coordination mod of the ligand towards each metal ion and displays the binegative pentadentate mod as the maximum mod of coordination obtained with Ni(II) and Cu(II) complexes. (1)HNMR spectrum of UO(2)(+2) complex in comparing with the free ligand spectrum supports the binegative appearance of the coordinated ligand through the ionization of CO and CS groups. The electronic spectral data as well as the magnetic moment measurements are coincide with each others to propose the square-planar geometry with Ni(II), Pd(II) and Cu(II) complexes and octahedral geometry with the others. ESR spectrum of Cu(II) complex displays axially symmetric g tensor parameters with g(11)>g(⊥)>2.0023 indicating that the [Formula: see text] orbital as a ground state with the square-planar geometry. The TG analysis for all isolated complexes were carried out to assert about the presence of water molecules physically or chemically attached with the central atom. The biological study was carried out against different microorganisms as gram negative, gram positive and fungi. The comparable data display the relative priority of Ni(II) complex in comparing with others against all organisms but, the other complexes display activity by the same with the free ligand.

Cellular responses to the metal-binding properties of metformin

In recent decades, the antihyperglycemic biguanide metformin has been used extensively in the treatment of type 2 diabetes, despite continuing uncertainty over its direct target. In this article, using two independent approaches, we demonstrate that cellular actions of metformin are disrupted by interference with its metal-binding properties, which have been known for over a century but little studied by biologists. We demonstrate that copper sequestration opposes known actions of metformin not only on AMP-activated protein kinase (AMPK)-dependent signaling, but also on S6 protein phosphorylation. Biguanide/metal interactions are stabilized by extensive π-electron delocalization and by investigating analogs of metformin; we provide evidence that this intrinsic property enables biguanides to regulate AMPK, glucose production, gluconeogenic gene expression, mitochondrial respiration, and mitochondrial copper binding. In contrast, regulation of S6 phosphorylation is prevented only by direct modification of the metal-liganding groups of the biguanide structure, supporting recent data that AMPK and S6 phosphorylation are regulated independently by biguanides. Additional studies with pioglitazone suggest that mitochondrial copper is targeted by both of these clinically important drugs. Together, these results suggest that cellular effects of biguanides depend on their metal-binding properties. This link may illuminate a better understanding of the molecular mechanisms enabling antihyperglycemic drug action.

Spectral, thermal, kinetic, molecular modeling and eukaryotic DNA degradation studies for a new series of albendazole (HABZ) complexes

This work represents the elaborated investigation for the ligational behavior of the albendazole ligand through its coordination with, Cu(II), Mn(II), Ni(II), Co(II) and Cr(III) ions. Elemental analysis, molar conductance, magnetic moment, spectral studies (IR, UV-Vis and ESR) and thermogravimetric analysis (TG and DTG) have been used to characterize the isolated complexes. A deliberate comparison for the IR spectra reveals that the ligand coordinated with all mentioned metal ions by the same manner as a neutral bidentate through carbonyl of ester moiety and NH groups. The proposed chelation form for such complexes is expected through out the preparation conditions in a relatively acidic medium. The powder XRD study reflects the amorphous nature for the investigated complexes except Mn(II). The conductivity measurements reflect the non-electrolytic feature for all complexes. In comparing with the constants for the magnetic measurements as well as the electronic spectral data, the octahedral structure was proposed strongly for Cr(III) and Ni(II), the tetrahedral for Co(II) and Mn(II) complexes but the square-pyramidal for the Cu(II) one. The thermogravimetric analysis confirms the presence or absence of water molecules by any type of attachments. Also, the kinetic parameters are estimated from DTG and TG curves. ESR spectrum data for Cu(II) solid complex confirms the square-pyramidal state is the most fitted one for the coordinated structure. The albendazole ligand and its complexes are biologically investigated against two bacteria as well as their effective effect on degradation of calf thymus DNA.

Polymer complexes: XLXII-interplay of coordination π-π stacking and hydrogen bonding in supramolecular assembly of [sulpha drug derivatives-N,S:N,O] complexes

A novel series of nickel(II) polymer complexes of 5-sulphadiazineazo-3-phenylamino-2-thio-4-thiazolidinone (HL₁), 5-sulphamethazine-3-phenylamino-2-thioxo-4-thiazolidinone (HL₂), 5-sulphamethoxazole-3-phenylamino-2-thioxo-4-thiazolidinone (HL₃), 5-sulphacetamide-3-phenyl-2-thioxo-4-thiazolidinone (HL₄) and 5-sulphaguanidine-3-phenylamino-2-thioxo-4-thiazolidinone (HL₅) were prepared and characterized. IR spectra show that HL(n) (n=1-5) is coordinated to the metal ion in a neutral tetradentate manner with NSNO donor sites of NH (hydrazone's), NH (3-phenylamine), carbonyl group and Ph-NH. The title [Ni₃(HL(n))₂(μ-OAc)₂(OAc)₄](n) consists of three Ni(II) atoms linked by interchain π-π interaction are observed between aromatic rings of two ligands (HL(n)) which are further doubly bridged two adjacent nickel atoms by acetate group. The geometrical structures of these complexes are found to be octahedral. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, thermal, infrared, ¹H NMR, electronic spectra, magnetic susceptibility and conductivity measurements. The richness of electronic spectral in these complexes is also supporting evidence for the trinuclearity of the Ni(II) polymer complexes.

Coordination and biological behaviour of 2-(p-toluidino)-N'-(3-oxo-1,3-diphenylpropylidene) acetohydrazide and its metal complexes

A series of Ni(II), Co(II), Cu(II), Mn(II), Zn(II), Zr(IV), Fe(III), Ru(III), La(III), Hf(IV) and U(VI) complexes of 2-( p-toluidino)-N'-(3-oxo-1,3-diphenylpropylidene) acetohydrazide (H2L) have been synthesised and characterised by elemental and thermal analyses (DTA, TG), molar conductances, magnetic moments, IR, 1H NMR, UV-Vis spectra and ESR measurements. The ESR spectra of solid complexes [(L)(HL)Cu2(OAc)], [Cu(HL)(H2L)(NO3)] and [CuCl (HL)(H2L)].H2O at room temperature show axial symmetry with covalent bond character, and complex [FeCl2(HL)(H2O)] has gav = 4.38, indicating a high spin (5/2) iron(III) complex. However, complexes [(HL)Mn2Cl3(H2O)4] and [RuCl2(HL)(H2O)].H2O have isotropic spectra consistent with octahedral structure. The antifungal and antibacterial activities of the ligand and its complexes were investigated.

Synthesis, Spectroscopic Investigation and Biological Activity of Metal(ll) Complexes with N2O4 Ligands

A new series of Mn(II), Ni(II), Co(II) and Cu(ll) complexes derived from diacetylmonoxime and 2-, 4- and 6-aminobenzoic acids have been prepared and characterised by elemental and thermal analyses (DTA, DTG and TG) as well as 1H and 13C NMR, IR, UV-Vis., Mass and ESR spectra, magnetic susceptibility and conductance measurements. The IR spectral data show that the ligands behave as mono- or di-basic, bis-, tri-, or tetradentate-chelates towards the metal ion. The stability of the complexes is achieved via intra- and inter-molecular hydrogen bonding of the OH-group with the oximato-oxygen atom or oxygen atom of a carboxylic group, giving polymeric networks in the solid state. Molar conductances in DMF solution indicate that the complexes are non-electrolytes. The ESR spectra of solid complexes [Co (HL1)21.2H2O (4), [Mn(HL1)2].H2O (5), [Mn(HL2)2(H2O)2].H2O (10), [Cu2(HL3)2(OAc)2(H2O)4] (12) and [(Mn)3 (L3)2(OAc)2(H2O)6].4H2O (15) at room temperature and 77 K, are isotropic, however, the copper(ll) complexes [Cu(HL1)(OAc)(H2O)2}2] (2) and [Cu(HL2)2(H2O)2].H2O (7) are non-axial and axial (dx2-y2) respectively with covalent bond character. The metal complexes exhibit greater inhibitory effects than tetracycline (bacteria) and amphotricen (fungi).

Coordination modes of novel rhodanine azodye complexes

The reaction products of metal(II) salts with 5-sulphamethoxazoleazo-3-phenyl-2-thioxo-4-thiazolidinone (H2L) have been characterized by elemental analyses, magnetic susceptibility, electronic, infrared and electron paramagnetic resonance spectral measurements. The spectral data suggest a square pyramidal structure for Cu(II) and Co(II) complexes and an octahedral for Ni(II) complexes. Various EPR parameters have been calculated. From the electron paramagnetic resonance and spectral data, the orbital reduction factors were calculated. In all case kperpendicular > kparallel which indicates a 2B1g ground state. These five coordinated complex of Cu(II) react further with pyridine forming six coordinate base adduct. The different modes of chelation of the ligand and stereochemistry around the metal ion are discussed.

Spectral studies on metal-ligand bonding of novel rhodanine azodye sulphadrugs

A series of novel complexes with 5-sulphadiazineazo-3-phenyl-2-thioxo-4-thiazolidinone (H2L1) and 5-sulphamethazineazo-3-phenyl-2-thioxo-4-thiazolidinone (H2L2) and various anions were prepared. Their structures and properties were characterized by elemental analyses, IR, UV-vis, EPR spectroscopy and magnetic measurements. The visible and EPR spectral studies indicated that the Cu(II) complexes have distorted octahedral. From the electron paramagnetic resonance and spectral data, the orbital reduction factors k(parallel) and k(perpendicular) were calculated. In all cases k(perpendicular) > k(parallel) indicates a 2B1g ground state. The crystal field parameters for Co(II) and Ni(II) complexes were calculated. The electronic absorption and a g(parallel)/A(parallel) values are indicative for the beginning of tetragonal distortion. The complexes, however, have lower symmetries and the amount of distortion in terms of DT/Dp, applying NSH 'Hamiltonian Theory' has been evaluated which indicate that the complexes are moderately distorted.