Coordination of the natural ligand lapachol to iron(II): synthesis,theoretical study and antiproliferative activity

Transition Metal Chemistry - Lapachol is a natural naphthoquinone known for having a variety of biological properties, and in recent years, it has been used in the synthesis of metal complexes with...     

On the Search of Metallated Sulfonamides: Synthesis and X‐ray Characterization of the New Sulfathiazolato Nickel(II)‐Chelate Complex [Ni(STZ)2(Py)2]·2Py (STZ = Sulfathiazolato Anion; Sulfathiazole = N1‐2‐thiazolyl‐sulfanilamide; Py = Pyridine)

Sulfathiazole (HSTZ) reacts with triethylamine and Ni(CH₃COO)₂·4H₂O in methanol and further with pyridine to give the sulfathiazolato complex [Ni(STZ)₂(Py)₂]·2Py. In the new chelate complex the deprotonated sulfonamidic nitrogen atom does not take part in the coordination process, apparently retaining the negative charge. Two (STZ)^? moieties are symmetrically bonded to the Ni²⁺ ion through a thiazolyl nitrogen atom and an oxygen atom of the S(O)₂ group. Two pyridine molecules accomplish the fairly distorted octahedral coordination at the metal centre.     

Chemical Conversion of Hg‐Clusters: Synthesis and Crystal Structure of $ {\rm [(DMSO)_2 Co(NC \overline{S)_4(Hg}-TePh)_2]_{\rm n} }$, the First Compound Containing a Polymeric Hg—Te Chain

The six‐membered ring Hg₃Te₃ of [Hg₃Cl₃(μ‐TePh)₃]·2 DMSO {(Ph = C₆H₅; DMSO = (CH₃)₂SO} was opened by redissolution with DMSO, reacting with Co[Hg(SCN)₄] and affording polymeric . The monoclinic novel compound belong to the space group P2₁/n and assembles in a bidimensional lattice tetrahedral Hg^II(SCN)₂Te₂‐ and octahedral Co^II(NCS)₄(DMSO)₂‐chains linked trough SCN bridges along the crystallographic axis b and diagonally to the ac axes. The structure of [(DMSO)₂Co(NCS)₄(Hg—TePh)₂]_n is limited by the DMSO ligands in the axial positions of the Co‐octahedrons.     

Double Carbonyl Substitution in [BrMn(CO)5]: Reaction with Benzoylhydrazine and Synthesis of fac‐[Mn(Br)(CO)3(BHD)]·2THF (BHD = OC(Ph)—NH—NH2)

[BrMn(CO)₅] reacts with benzoylhydrazine in THF occurring substitution of two CO groups by a Metal‐ligand ring to give fac‐[Mn(Br)(CO)₃(BHD)]·2THF (BHD = C₆H₅CONHNH₂). The novel compound shows a distorted octahedral arrangement at the manganese atom, with three nearly linear carbonyl ligands in a fac arrangement, illustrating another example that the CO group in position trans to the bromine ligand in [BrMn(CO)₅] presents the most intensive metal‐CO backbonding effect of all the CO groups of the parent complex, leading to the formation of a facial (and not meridional) isomer, even in the presence of a bidentate ligand like benzydrazide. X‐ray measures of yellow crystals showed that the title complex belong to space group P2₁/c, with the asymmetric unit containing one crystallographically independent [Mn(Br)(CO)₃(BHD)] complex and two tetrahydrofurane solvate molecules. The new compound represents heretofore the unique occurrence of the complexing single bidentate ligand ‐O=C(Ph)‐N(H)‐N(H)₂‐ with an octahedral coordination at the Mn^I atom supported chiefly by carbonyl groups.     

Unidimensional Self‐assembling of {HgII[NNN(PhBr)2]2} through Metal‐η4‐arene π‐Interactions: Synthesis and X‐Ray Characterization of a Bis Diaryl Symmetric‐substituted Triazenide Complex Polymer of Mercury(II)

A solution of deprotonated 1,3‐bis(4‐bromophenyl)triazene reacts with Hg(CH₃COO)₂ in methanol / tetrahydrofurane to give yellow crystalline needles of {Hg^II[NNN(PhBr)₂]₂}_n, a triazenide complex polymer of Hg^II with metal‐η²,η²‐arene π‐interactions, performed by coordinated single triazenide chains. The crystal structure of the new polymeric complex of Hg^II belongs to the monoclinic space group P2₁/n. The lattice of [Hg^II(BrPhNNNPhBr)₂]_n can be viewed as a one‐dimensional assembling of planar tectons [Hg^II(BrPhNNNPhBr)₂] linked through metalocene alike Hg^II‐η²,η²‐arene π‐interactions along the crystallographic b axis.     

Synthesis and Structural Features of a New Diselenonium Dication Stabilized by Sulfur Atoms of Thiourea Groups: X‐ray Characterization of [(Se‐ettu)2]Br2 (ettu = ethylenethiourea)

Selenium and bromine were refluxed in methanol and stirred with ethylenethiourea to give yellow crystals of [(Se‐ettu)₂]Br₂ (ettu = ethylenethiourea). The first reported 1,2‐diselenonium dication stabilized by sulfur atoms is air unstable and yields a three‐dimensional lattice with Se⁺···Br^?···Se⁺ bridges enclosing also single Se⁺···Br^? interactions and H···Br^? bonds. The air instability of [(Se‐ettu)₂]Br₂ probably is due to redox reactions which lead to the decomposition of ethylenethiourea with precipitation of sulfur.     

Exploring Te–Te Bond Cleavage with Palladium(II): Synthesis,X‐ray Structural Characterization,and Optical Features of Tellurolate and Telluro‐Ether Complexes of Palladium(II)

The focus of this study was to explore reactions of (RTe)₂ with palladium(II) salts. These reactions led to Te–Te bond cleavage and the formation of three tellurolate‐bridged dinuclear complexes and a mononuclear telluro‐ether palladium(II) complex. The methodologies used yielded single source precursors for interesting materials. UV/vis spectroscopy results supported the measured optical bandgap for the complexes in the solid state. A study on the structure of all complexes in the solid state was carried out using single‐crystal X‐ray diffraction. Other analytical methodologies, such as elemental analysis and infrared spectroscopy, were also used for the characterization of the complexes.     

Oxazolidine copper complexes: Synthesis,characterization and superoxide dismutase activity of copper(II) complexes with oxazolidine ligands derived from hydroxyquinoline carboxaldehyde

This work describes the synthesis of copper(II) complexes, their identification using spectroscopic and electrochemical methods, structural characterization with X‐ray diffraction and density functional theory calculations (DFT), as well as their catalytic activity mimicking that of superoxide dismutase. Structural analysis revealed the formation of complexes with cyclization of ligands L1 and L2 with the formation of a heterocycle, 1,3‐oxazolidine. The DFT calculations confirmed this trend by stabilizing with lower energy. In addition, evaluations of mimetic enzymatic activity of complexes C1, C2, C3 and C4 revealed promising IC₅₀ values compared to other results seen in the literature (IC₅₀ = 0.22, 0.328, 0.55 and 0.92). Also, calf thymus DNA interactive experiments using UV–visible spectroscopy were conducted in the presence of the copper(II) complexes.     

Synthesis, structure and optical features of single adamantanoid Hg-SePh-X anionic clusters stabilized by octahedral complexes (Ph = phenyl; X = Cl, Br, I)

The ligand dppmo₂ [CH₂{P(O)Ph₂}₂] (Ph = phenyl), MgCl₂·6H₂O, MgBr₂, MgI₂, FeBr₂, CoBr₂, NiBr₂ and Hg(SePh)₂ react one at a time to give the complex salt of the general formula [M(dppmo₂)₃][Hg₄X₄(SePh)₆]·4dmf·H₂O (M = Mg²⁺, Fe²⁺, Co²⁺, Ni²⁺; X = Cl, Br, I; dmf = dimethylformamide). The cations [M(dppmo₂)₃]²⁺ are predominantly octahedral with axial angles from 175° to 178°. The adamantane like anions [Hg₄X₄(SePh)₆]²⁻ are examples of single adamantanoid species, since these compounds normally appear as polymers or fused cages. Adamantanoid cages are the preferential thermodynamic configuration for this atomic aggregate. They appear as single molecules or ions however only in a halogen rich reactions milieu.     

Synthesis of 1,2-disubstitued benzimidazoles using SiO2/ZnCl2

A general and easy method for the synthesis of several 1,2-disubstituted benzimidazoles using SiO₂/ZnCl₂ and solvent-free conditions is described. This efficient and improved method furnishes selectively and in good yields the corresponding 1,2-bis(organyl)-benzimidazoles starting from o-phenylenediamine and aromatic or aliphatic aldehydes. The catalytic system was re-used up three times and the use of focused microwaves accelerates the reaction.