Solution equilibrium and redox properties of metal complexes with 2-formylpyridine guanylhydrazone derivatives: Effect of morpholine and piperazine substitutions.

Schiff bases derived from aminoguanidine are extensively investigated for their structural versatility. The tridentate 2-formylpyridine guanylhydrazones act as analogues of 2-formyl or 2-acetylpyridine thiosemicarbazones, where the thioamide unit is replaced by the guanidyl group. Six derivatives of 2-formylpyridine guanylhydrazone were synthesized and their proton dissociation and complex formation processes with Cu(II), Fe(II) and Fe(III) ions were studied using pH-potentiometry, UV-visible, NMR and electron paramagnetic resonance spectroscopic methods.

Nickel(II) complexes with 14-membered bis-thiosemicarbazide and bis-isothiosemicarbazide ligands: synthesis, characterization and catalysis of oxygen evolution reaction.

Design and development of novel, low-cost and efficient electrocatalysts for oxygen evolution reaction (OER) in alkaline media is crucial for lowering the reaction overpotential and thus decreasing the energy input during the water electrolysis process. Herein, we present the synthesis of new 14-membered bis-thiosemicarbazide and bis-isothiosemicarbazide macrocycles and their nickel(II) complexes characterized by spectroscopic techniques (H and C NMR, IR, UV-vis), electrospray ionization mass spectrometry, single crystal X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) and cyclic voltammetry. Finally, the activity of nickel(II) complexes towards OER is reported.

Are the metal identity and stoichiometry of metal complexes important for colchicine site binding and inhibition of tubulin polymerization?

Quite recently we discovered that copper(II) complexes with isomeric morpholine-thiosemicarbazone hybrid ligands show good cytotoxicity in cancer cells and that the molecular target responsible for this activity might be tubulin. In order to obtain better lead drug candidates, we opted to exploit the power of coordination chemistry to (i) assemble structures with globular shape to better fit the colchicine pocket and (ii) vary the metal ion. We report the synthesis and full characterization of bis-ligand cobalt(III) and iron(III) complexes with 6-morpholinomethyl-2-formylpyridine 4-(4-hydroxy-3,5-dimethylphenyl)-3-thiosemicarbazone (HL1), 6-morpholinomethyl-2-acetylpyridine 4-(4-hydroxy-3,5-dimethylphenyl)-3-thiosemicarbazone (HL2), and 6-morpholinomethyl-2-formylpyridine 4-phenyl-3-thiosemicarbazone (HL3), and -ligand nickel(II), zinc(II) and palladium(II) complexes with HL1, namely [Co(HL)(L)](NO) (1), [Co(HL)(L)](NO) (2), [Co(HL)(L)](NO) (3), [Fe(L)]NO (4), [Fe(HL)(L)](NO) (5), [Ni(L)]Cl (6), [Zn(L)Cl] (7) and [Pd(HL)Cl]Cl (8).

Isomerization pathway of a C-C sigma bond in a bis(octaazamacrocycle)dinickel(II) complex activated by deprotonation: a DFT study.

Unlabelled: The anti () to syn () isomerization pathway of the deprotonated form of the dimer with two nickel(II) 15-membered octaazamacrocyclic units connected via a carbon-carbon (C-C) σ bond was investigated. For the initial anti () structure, a deprotonation of one of the bridging ( hybridized) carbon atoms is suggested to allow for an to geometry twist. A 360° scan around the bridging C-C dihedral angle was performed first to find an intermediate geometry.

Indolo[2,3-]benzazocines and indolo[2,3-]benzazonines and their copper(II) complexes as microtubule destabilizing agents.

A series of four indolo[2,3-]benzazocines HL1-HL4 and two indolo[2,3-]benzazonines HL5 and HL6, as well as their respective copper(II) complexes 1-6, were synthesized and characterized by H and C NMR spectroscopy, ESI mass spectrometry, single crystal X-ray diffraction (SC-XRD) and combustion analysis (C, H, N). SC-XRD studies of precursors Vd, VIa·0.5MeOH, of ligands HL4 and HL6·DCM, and complexes 2·2DMF, 5·2DMF, 5'·iPrOH·MeOH provided insights into the energetically favored conformations of eight- and nine-membered heterocycles in the four-ring systems.

Corrigendum to: Recent Developments in the Field of Tumor-Inhibiting Metal Complexes.

An article was published in the journal "Current Pharmaceutical Design", Volume 9, No. 25, 2003, pp: 2078-2089 [1]. The first author is requesting an alteration in the name.

Spectroscopic Characterization of the Binding and Release of Hydrophilic, Hydrophobic and Amphiphilic Molecules from Ovalbumin Supramolecular Hydrogels.

Protein-based hydrogels have attracted growing attention for pharmaceutical and biomedical applications. Ovalbumin (OVA), the hen egg white albumin, possessing good foaming and gelling properties and being widely used in the food industry, has recently been indicated as a potential pharmaceutical vehicle. In this study, the binding and release properties of pure OVA hydrogels were investigated by electron paramagnetic resonance (EPR) spin labeling.

Enriching Chemical Space of Bioactive Scaffolds by New Ring Systems: Benzazocines and Their Metal Complexes as Potential Anticancer Drugs.

The search for new scaffolds of medicinal significance combined with molecular shape enhances their innovative potential and continues to attract the attention of researchers. Herein, we report the synthesis, spectroscopic characterization (H and C NMR, UV-vis, IR), ESI-mass spectrometry, and single-crystal X-ray diffraction analysis of a new ring system of medicinal significance, 5,6,7,9-tetrahydro-8-indolo[3,2-]benzazocin-8-one, and a series of derived potential ligands (), as well as ruthenium(II), osmium(II), and copper(II) complexes (, , and ). The stability of compounds in 1% DMSO aqueous solutions has been confirmed by H NMR and UV-vis spectroscopy measurements.

Different Modes of Acid-Promoted Cyclooligomerization of 4-(4-Thiosemicarbazido)butan-2-one Hydrazone: 14-Membered versus 28-Membered Polyazamacrocycle Formation.

Unprecedented self-assembly of a novel 14-membered cyclic bis-thiosemicarbazone or/and a 28-membered cyclic tetrakis-thiosemicarbazone upon acid-promoted cyclooligomerization of 4-(4-thiosemicarbazido)butan-2-one hydrazone has been discovered. A thorough study of the influence of various factors on the direction of macrocyclization provided the optimal conditions for the highly selective formation of each of the macrocycles in excellent yields. Plausible pathways for macrocyclizations have been discussed.

Synthesis and crystal structure of -di-aqua(1,4,8,11-tetra-aza-undeca-ne)copper(II) isophthalate monohydrate.

In the title hydrated mol-ecular salt, [Cu(CHN)(HO)](CHO)·HO, the metal ion is coordinated by the two primary and two secondary N atoms of the amine ligand and the mutually O atoms of the water mol-ecules in a tetra-gonally distorted octa-hedral geometry. The average equatorial Cu-N bond lengths (2.013 and 2.

The Release of a Highly Cytotoxic Paullone Bearing a TEMPO Free Radical from the HSA Hydrogel: An EPR Spectroscopic Characterization.

This study shows the potential of a thermally induced human serum albumin (HSA) hydrogel to serve as a drug depot for sustained release of a highly cytotoxic modified paullone ligand bearing a TEMPO free radical (). The binding of to HSA was studied by electron paramagnetic resonance (EPR) spectroscopy and imaging. The EPR protocol was also implemented for the study of matrix degradation, and ligand diffusion rate, in two additional spin-labeled hydrogels, containing 5-doxylstearate and 3-carbamoyl-proxyl.

Elucidation of Structure-Activity Relationships in Indolobenzazepine-Derived Ligands and Their Copper(II) Complexes: the Role of Key Structural Components and Insight into the Mechanism of Action.

Indolo[3,2-][1]benzazepines (paullones), indolo[3,2-][2]benzazepines, and indolo[2,3-][2]benzazepines (latonduines) are isomeric scaffolds of current medicinal interest. Herein, we prepared a small library of novel indolo[3,2-][2]benzazepine-derived ligands - and copper(II) complexes -. All compounds were characterized by spectroscopic methods (H and C NMR, UV-vis, IR) and electrospray ionization (ESI) mass spectrometry, while complexes and , in addition, by X-ray crystallography.

Solution Equilibrium Studies on Salicylidene Aminoguanidine Schiff Base Metal Complexes: Impact of the Hybridization with L-Proline on Stability, Redox Activity and Cytotoxicity.

The proton dissociation processes of two tridentate salicylidene aminoguanidine Schiff bases (SISC, Pro-SISC-Me), the solution stability and electrochemical properties of their Cu(II), Fe(II) and Fe(III) complexes were characterized using pH-potentiometry, cyclic voltammetry and UV-visible, H NMR and electron paramagnetic resonance spectroscopic methods. The structure of the proline derivative (Pro-SISC-Me) was determined by X-ray crystallography. The conjugation of L-proline to the simplest salicylidene aminoguanidine Schiff base (SISC) increased the water solubility due to its zwitterionic structure in a wide pH range.

Ruthenium-nitrosyl complexes as NO-releasing molecules, potential anticancer drugs, and photoswitches based on linkage isomerism.

The synthesis of new types of mono- and polynuclear ruthenium nitrosyl complexes is driving progress in the field of NO generation for a variety of applications. Light-induced Ru-NO bond dissociation in solution may involve transient linkage isomers MS1 (Ru-ON) and MS2 (Ru-η-NO), which can be detected spectroscopically and analyzed computationally. The investigation of photoisomerization processes in the solid state may be useful for potential application of such complexes for data storage, photochromic or photomagnetic materials or even non-linear optics.

Diastereomeric dinickel(II) complexes with non-innocent bis(octaazamacrocyclic) ligands: isomerization, spectroelectrochemistry, DFT calculations and use in catalytic oxidation of cyclohexane.

Diastereomeric dinickel(II) complexes with bis-octaazamacrocyclic 15-membered ligands [Ni(L1-3-L1-3)Ni] (4-6) have been prepared by oxidative dehydrogenation of nickel(II) complexes NiL1-3 (1-3) derived from 1,2- and 1,3-diketones and -methylisothiocarbohydrazide. The compounds were characterized by elemental analysis, ESI mass spectrometry, and IR, UV-vis, H NMR, and C NMR spectroscopy. Single crystal X-ray diffraction (SC-XRD) confirmed the isolation of the and isomers of bis-octaazamacrocyclic dinickel(II) complexes 4a and 4s, the -configuration of 5s and the -configuration of the dinickel(II) complex 6a.

Ready access to 7,8-dihydroindolo[2,3-][1]benzazepine-6(5)-one scaffold and analogues via early-stage Fischer ring-closure reaction.

Paullone isomers are known as inhibitors of tubulin polymerase and cyclin dependent kinases (Cdks), which are potential targets for cancer chemotherapy. Herein we report an efficient and clean pathway to the fourth isomer, which remained elusive so far, namely 7,8-dihydroindolo[2,3-][1]benzazepin-6(5)-one. Moreover, we demonstrate the generality of our pathway by synthesizing two closely related analogues, one containing a bromo substituent and the other one incorporating an 8-membered instead of a 7-membered ring.

Highly Antiproliferative Latonduine and Indolo[2,3-]quinoline Derivatives: Complex Formation with Copper(II) Markedly Changes the Kinase Inhibitory Profile.

A series of latonduine and indoloquinoline derivatives - and their copper(II) complexes () were synthesized and comprehensively characterized. The structures of five compounds (, , , , and ) were elucidated by single crystal X-ray diffraction. The copper(II) complexes revealed low micro- to sub-micromolar IC values with promising selectivity toward human colon adenocarcinoma multidrug-resistant Colo320 cancer cells as compared to the doxorubicin-sensitive Colo205 cell line.

Inhibition of Microtubule Dynamics in Cancer Cells by Indole-Modified Latonduine Derivatives and Their Metal Complexes.

Indolo[2,3-]benzazepines (indololatonduines) are rarely discussed in the literature. In this project, we prepared a series of novel indololatonduine derivatives and their Ru and Os complexes and investigated their microtubule-targeting properties in comparison with paclitaxel and colchicine. Compounds were fully characterized by spectroscopic techniques (H NMR and UV-vis), ESI mass-spectrometry, and X-ray crystallography, and their purity was confirmed by elemental analysis.

The Ruthenium Nitrosyl Moiety in Clusters: Trinuclear Linear μ-Hydroxido Magnesium(II)-Diruthenium(II), μ-Oxido Trinuclear Diiron(III)-Ruthenium(II), and Tetranuclear μ-Oxido Trigallium(III)-Ruthenium(II) Complexes.

The ruthenium nitrosyl moiety, {RuNO}, is important as a potential releasing agent of nitric oxide and is of inherent interest in coordination chemistry. Typically, {RuNO} is found in mononuclear complexes. Herein we describe the synthesis and characterization of several multimetal cluster complexes that contain this unit.

Crystal structure of -di-aqua-(1,4,8,11-tetra-aza-undeca-ne)nickel(II) bis-(pyridine-2,6-di-carboxyl-ato)nickel(II).

The asymmetric unit of the title compound, -di-aqua-(1,4,8,11-tetra-aza-undecane-κ , , , )nickel(II) bis-(pyridine-2,6-di-carboxyl-ato-κ ,, )nickel(II) {[Ni()(HO)][Ni(pdc)] where = 1,4,8,11-tetra-aza-undecane (CHN) and pdc = the dianion of pyridine-2,6-di-carb-oxy-lic acid (CHNO )} consists of an [Ni()(HO)] complex cation and a [Ni(pdc)] anion. The metal ion in the cation is coordinated by the four N atoms of the tetra-amine ligand and the mutually O atoms of the water mol-ecules in a tetra-gonally elongated octa-hedral geometry with the average equatorial Ni-N bond length slightly shorter than the average axial Ni-O bond [2.087 (4) 2.

Towards understanding the magnetism of Os(IV) complexes: an insight.

The magnetism of a recently synthesized -[OsCl(κN-Hind)] complex (5d-system), where Hind = 2-indazole, was studied experimentally and theoretically. Relativistic CASSCF/CASPT2 calculations for this and model [OsCl] complexes were employed to understand the nature of the low-lying multiplets. It is found that despite strong metal-ligand covalency they are basically characterized by the total angular pseudo-momentum originating from the spin-orbit coupling of the ground-state spin = 1 with the orbital pseudo-momentum = 1 of the Os ion.

Ni Oxidation State and Ligand Saturation Impact on the Capability of Octaazamacrocyclic Complexes to Bind and Reduce CO.

Two 15-membered octaazamacrocyclic nickel(II) complexes are investigated by theoretical methods to shed light on their affinity forwards binding and reducing CO. In the first complex [], the octaazamacrocyclic ligand is grossly unsaturated (π-conjugated), while in the second [] one, the macrocycle is saturated with hydrogens. One and two-electron reductions are described using Mulliken population analysis, quantum theory of atoms in molecules, localized orbitals, and domain averaged fermi holes, including the characterization of the Ni-C bond and the oxidation state of the central Ni atom.

Triapine Analogues and Their Copper(II) Complexes: Synthesis, Characterization, Solution Speciation, Redox Activity, Cytotoxicity, and mR2 RNR Inhibition.

Three new thiosemicarbazones (TSCs) - as triapine analogues bearing a redox-active phenolic moiety at the terminal nitrogen atom were prepared. Reactions of - with CuCl·2HO in anoxic methanol afforded three copper(II) complexes, namely, (), [ (), and (), in good yields. Solution speciation studies revealed that the metal-free ligands are stable as - at pH 7.