Oxidative stress and methods used for hydroxyl radical determination

Understanding the role of oxidative stress in brain as well as developing medical strategies to reduce its damaging potential in the aging process and pathogenesis of cancer, neurological diseases like Alzheimer’s diseases and Parkinson’s diseases and other incurable illnesses is an important direction in medicine and biochemistry over the world. This review outlines the processes by which hROS may be formed, their damaging potential and determinations methods. Also, the questions upon the nature of reactive hROS in a Fenton (like) system plays a crucial role will be addressed on this part and several lines of evidences will be presented in order to clarify this issue. Highly reactive hydroxyl radicals (hROS) have been implicated in the etiology of many diseases, therefore monitoring of hROS should be extremely helpful to further investigate and understand the role of hROS in the pathogenesis of neurological disorders and to develop medical strategies to reduce the damaging potential of hROS. The very short half-life of OH• requires the use of trapping agents such as salicylic acid or phenylalanine for detection, but their hydroxylated derivatives are either unstable, or implicated as reactant in biochemical processes. Based on already successfully in vitro and in vivo work done in our group in the past two decades, we decided to use sodium terephthalic acid as a trapping agent, the hydroxylation of which yields only one stable and highly fluorescent isomer, 2-hydroxyterephthalate (OH-TA)

Magnetic-, ESR and Quantumchemical Investigations on Penta- and Hexa- Coordinated Manganese (II) Complexes

Two manganese(II) complexes with the tridentate ligand 2,6-bis(benzimidazol-2-yl)pyridine, namely $[Mn(bzimpy)_2](ClO_4)_2$, 1, and $[Mn(bzimpy)Cl_2]$ * 0.5MeOH, 2, have been investigated by magnetic AC susceptibility measurements in the temperature range of 18 to 300 K. Electron spin resonance has been performed in solid state and frozen solution at 77 K. Parameters for the magnetic contributions to the Hamiltonian received by these techniques confirm axial magnetic anisotropy. ACS data are: $g_av = 1.92±0.04$, $|D/hc| = 0.9±1.3 cm^-1$ and $g_av = 1.89$, $|D/hc| = 1.4 cm^-1$ for 1, and 2, respectively. The three found ESR resonances correspond to $g_eff^(1) = 1.99$, $g_eff^(2) = 3.3$ and $g_eff^(3) = 4.3$. The highest field resonance exhibits a hyperfine sextet splitting of $|A_av/hcl| = 92 x 10^-4 cm^-1$ for both complexes. Well resolved forbidden transitions allow for an estimation of the zero-field splitting parameter being $D/hc = -0.09 and 0.13 cm^-1$ for the two complexes, respectively. $Ab$ $initio$ MO-LCAO-SCF calculations on a double-zeta basis set indicate that complex 2 should be more stable than $1$. The calculations yielded also information about electronic structure, bond-strenghts and charge distributions within the complexes

Ruthenium(II) complexes containing a phosphinefunctionalized thiosemicarbazone ligand: synthesis, structures and catalytic C–N bond formation reactions via N-alkylation

A series of ruthenium(II) complexes incorporating a thiosemicarbazone chelate tethered with a diphenylphosphine pendant have been studied. Thus, [(PNS-Et)RuCl(CO)(PPh3)] (1), [N,S-(PNS-Et) RuH(CO)(PPh3)2] (2) and [(PNS-Et)RuCl(PPh3)] (3) were synthesized by reactions of various RuII precursors with 2-(2-(diphenylphosphino)benzylidene)-N-ethylthiosemicarbazone (PNS-Et). However, complexation of PNS-Et with an equimolar amount of [RuCl2(dmso)4] resulted in two different entities [(PNS-Et) RuCl(dmso)2] (4) and [(PNS-Et)2Ru] (5) with different structural features in a single reaction. All the RuII complexes have been characterized by analytical and various spectroscopic techniques. Compounds 1–5 were recrystallized, and the X-ray crystal structures have been reported for 1, 2 and 5. In the complexes 1 and 3–5 the ligand coordinated in a tridentate monobasic fashion by forming PNS five- and six-membered rings, whereas in 2, the ligand coordinated in a bidentate monobasic fashion by forming a strained NS four-membered ring. Furthermore, compounds 1–5 showed catalytic activity in N-alkylation of heteroaromatic amines. Notably, complexes 1–3 were found to be very efficient catalysts toward N-alkylation of a wide range of heterocyclic amines with alcohols. In the presence of a catalytic amount of 2 with 50 mol% of KOH, N1,C5-dialkylation of 4-phenylthiazol-2-amine has been investigated. Reaction of in situ generated aldehyde with amine yields the N1,C5-dialkylated products through the hydride ion transformation from alcohol. Complexes 1–3 also catalyzed a variety of coupling reactions of benzyl alcohols and sulfonamides, which were realized often with 99% isolated yields. Advantageously, only one equivalent of the primary alcohol was consumed in the process

Field-Induced Single Molecule Magnetic Behavior of Mononuclear Cobalt(II) Schiff Base Complex Derived from 5-Bromo Vanillin

A mononuclear Co(II) complex of a Schiff base ligand derived from 5-Bromo-vanillin and 4-aminoantipyrine, that has a compressed tetragonal bipyramidal geometry and exhibiting field-induced slow magnetic relaxation, has been synthesized and characterized by single crystal X-ray diffraction, elemental analysis and molecular spectroscopy. In the crystal packing, a hydrogen-bonded dimer structural topology has been observed with two distinct metal centers having slightly different bond parameters. The complex has been further investigated for its magnetic nature on a SQUID magnetometer. The DC magnetic data confirm that the complex behaves as a typical S = 3/2 spin system with a sizable axial zero-field splitting parameter D/hc = 38 cm⁻¹. The AC susceptibility data reveal that the relaxation time for the single-mode relaxation process is τ = 0.16(1) ms at T = 2.0 K and BDC = 0.12 T

Investigations on the Spin States of Two Mononuclear Iron(II) Complexes Based on N-Donor Tridentate Schiff Base Ligands Derived from Pyridine-2,6-Dicarboxaldehyde

Iron(II)-Schiff base complexes are a well-studied class of spin-crossover (SCO) active species due to their ability to interconvert between a paramagnetic high spin-state (HS, S = 2, $^{5}$T$_{2}$) and a diamagnetic low spin-state (LS, S = 0, $^{1}$A$_{1}$) by external stimuli under an appropriate ligand field. We have synthesized two mononuclear FeII complexes, viz., [Fe(L$^{1}$)$_{2}$](ClO$_{4}$)$_{2}$.CH$_{3}$OH (1) and [Fe(L$^{2}$)$_{2}$](ClO$_{4}$)$_{2}$.2CH$_{3}$CN (2), from two N$_{6}$–coordinating tridentate Schiff bases derived from 2,6-bis[(benzylimino)methyl]pyridine. The complexes have been characterized by elemental analysis, electrospray ionization–mass spectrometry (ESI-MS), Fourier-transform infrared spectroscopy (FTIR), solution state nuclear magnetic resonance spectroscopy, $^{1}$H and $_{13}$C NMR (both theoretically and experimentally), single-crystal diffraction and magnetic susceptibility studies. The structural, spectroscopic and magnetic investigations revealed that 1 and 2 are with Fe–N$_{6}$ distorted octahedral coordination geometry and remain locked in LS state throughout the measured temperature range from 5–350 K

Poly[[bis­{μ3-tris­[2-(1H-tetra­zol-1-yl)eth­yl]amine}copper(II)] bis­(perchlorate)]

In the title compound, {[Cu(C9H15N13)2](ClO4)2}n, the Cu2+ cation lies on an inversion center and is coordinated by the tetra­zole N4 atoms of six symmetry-equivalent tris­[2-(1H-tetra­zol-1-yl)eth­yl]amine ligands (t 3 z) in the form of a Jahn–Teller-distorted octa­hedron with Cu—N bond distances of 2.0210 (8), 2.0259 (8) and 2.4098 (8) Å. The tertiary amine N atom is stereochemically inactive. The cationic part of the structure, viz. [Cu(t 3 z)2]2+, forms an infinite two-dimensional network parallel to (100), in pockets of which the perchlorate anions reside. The individual networks are partially inter­locked and held together by C—H⋯O inter­actions to the perchlorate anions and C—H⋯N inter­actions to tetra­zole N atoms

Characterization of a novel dioxomolybdenum complex by cyclic voltammetry

Metalloenzymes that carry a pterin-based molybdenum cofactor in their center catalyze numerous reactions in the human body and play a crucial role in its metabolism. Specifically, these enzymes promote redox reactions and oxygen transport in the body. Their absence may cause many problems leading to disability or even death in early childhood. Therefore, model compounds need to be synthesized and analyzed to investigate the reactivity, redox potential, and geometry of these cofactors. This study focused on electrode processes and determined the redox potentials of the new bis-(4-mercapto-5-(p-tolyl)-3H-1,2-dithiole-3-thione)-dioxomolybdenum complex by cyclic voltammetry. The 4-mercapto-5-(p-tolyl)-3H-1,2-dithiole-3-thione ligand underwent irreversible oxidation and reduction at thiol and thione functional groups. The new dioxomolybdenum complex showed a quasi-reversible two-stage electrode process

Anionic lanthanide complexes with 3-methyl-1-phenyl-4-formylpyrazole-5-one and hydroxonium as counter ion

AbstractA series of [H3O]+[LnL4]−·nH2O complexes (n=1–3, Ln=Nd, (1), Sm (2), Eu (3), Tb (4); HL=3-methyl-1-phenyl-4-formylpyrazole-5-one) were synthesized and characterized. The structures of the SmIII and EuIII complexes were investigated by X-ray diffraction. The isostructutal crystalls 2 and 3 consist the tetrakis [LnL4]− anions which are linked by H-bonding with the hydroxonium counter-ion and water molecules. The lanthanide ion is situated in the center of distorted tetragonal antiprism formed by eight oxygen atoms of 4-formyl-5-hydroxypyrazolonate anions. The TbIII and SmIII complexes show strong luminescence in solid state, whereas the EuIII and NdIII complexes show low luminescence activity