Mirela M. Barsan

Structural Motifs and Biological Studies of New Antimony(III) Iodide Complexes with Thiones

Eight new antimony(III) iodide complexes of the heterocyclic thioamides, 2-mercapto-1-methylimidazole (MMI), 2-mercaptobenzimidazole (MBZIM), 5-ethoxy-2-mercaptobenzimidazole (EtMBZIM), 2-mercaptothiazolidine (MTZD), 3-methyl-2-mercaptobenzothiazole (NMeMBZT), 2-mercapto-3,4,5,6-tetrahydropyrimidine (tHPMT), 2-mercaptopyridine (PYT), and 2-mercaptopyrimidine (PMT) of formulas {[SbI(3)(MMI)(2)].MeOH} (1), [SbI(3)(MBZIM)(2)] (2), {[SbI(2)(mu(2)-I)(EtMBZIM)(2)](2).H(2)O} (3), [SbI(3)(MTZD)] (4), [(NMeMBZT)SbI(2)(mu(2)-I)(2)(mu(2)-S-NMeMBZT)SbI(2) (NMeMBZT)] (5), {[SbI(3)(tHPMT)(3)].MeOH} (6), [SbI(3)(PYT)] (7), and [SbI(3)(PMT)(2)] (8), have been synthesized and characterized by elemental analysis, FT-IR spectroscopy, FT-Raman spectroscopy, and TG-DTA analysis. The crystal structures of 3, 4, 5, 6, and 7 were also determined by X-ray diffraction. The complexes show interesting structural motifs. Complex 6 is a monomer, with octahedral (Oh) geometry around the metal ion formed by three sulfur and three iodide atoms. Complexes 3 and 5 are dimers, with a square pyramidal (SP) geometry in each monomeric unit, while complexes 4 and 7 are polymers with pseudotrigonal bipyramidal (psi-TBP). Two or three sulfur atoms from thioamide ligands and three iodide atoms are bound to Sb atoms forming building blocks for the dimers and polymers. Strong intramolecular interactions between mu(2)-I and/or mu(2)-S and Sb atoms stabilize both structures. In dimer complex 5, two terminal iodide and one terminal sulfur atom are bonded to the Sb ion, while two mu(2)-I and one mu(2)-S bridging atoms bridge the metal ions forming psi-Oh geometry. Computational studies using multivariant linear regression (MLR) and artificial neural networks (ANN) and considering biological results (50% inhibitory concentration, IC(50)) as dependent variables derived a theoretical equation for IC(50) values of the complexes studied. The calculated IC(50) values are compared satisfactorily with the experimental inhibitory activity of the complexes measured. Complexes 3-7 were used to study their influence upon the catalytic peroxidation of linoleic acid by the enzyme Lipoxygenase (LOX). Compounds 1-8 were also tested for in vitro cytotoxicity, and they showed mostly a moderate cytostatic activity against a variety of tumor cell lines but comparable with those found for the antimony(III) chloride and bromide complexes, reported earlier [Ozturk et al. Inorg. Chem. 2007, 46, 2861-2866; Ozturk et al. Inorg. Chem. 2009, 48, 2233-2245].

New Antimony(III) Bromide Complexes with Thioamides : Synthesis, Characterization, and Cytostatic Properties

New antimony(III) bromide complexes with the heterocyclic thioamides, thiourea (TU), 2-mercapto-1-methylimidazole (MMI), 2-mercapto-benzimidazole (MBZIM), 2-mercapto-5-methyl-benzimidazole (MMBZIM), 5-ethoxy-2-mercapto-benzimidazole (EtMBZIM), 2-mercapto-3,4,5,6-tetrahydro-pyrimidine (tHPMT), 2-mercaptopyridine (PYT), 2-mercapto-thiazolidine (MTZD), 3-methyl-2-mercaptobenzothiazole (MMBZT), and 2-mercaptopyrimidine (PMTH) of formulas [SbBr(3)(TU)(2)] (1), [SbBr(3)(MMI)(2)] (2), {[SbBr(2)(MBZIM)(4)](+) [Br](-) H(2)O} (3), {[SbBr(2)(mu(2)-Br)(MMBZIM)(2)](2)} (4), {[SbBr(2)(mu(2)-Br)(EtMBZIM)(2)](2) MeOH} (5), {[SbBr(3)(mu(2)-S-tHPMT)(tHPMT)](n)} (6), {[SbBr(2)(mu(2)-Br)(PYT)(2))(n)} (7), {[SbBr(2)(mu(2)-Br)(MTZD)(2)](n)} (8), [SbBr(3)(MMBZT)(2)] (9), and {[SbBr(5)](2-)[(PMTH(2)(+))(2)]} (10) have been synthesized and characterized by elemental analysis, conductivity measurements, FTIR spectroscopy, FT-Raman spectroscopy, TG-DTA analysis, and X-ray powder diffraction. The crystal structures of 3, 4, 5, 6, 7, 8, and 10 were also determined by X-ray diffraction. In 3, four sulfur atoms from thione ligands and two bromide ions form an octahedral (O(h)) cationic [SbS(4)Br(2)](+) species in which the two bromide anions lie at axial positions. A third bromide counteranion neutralizes the whole complex. 4 and 5 are dimers, whereas 6, 7 and 8 are polymers, built up by monomeric units of square pyramidal (SP) geometry around the metal center, which were formed by two sulfur atoms of thioamide ligands and three bromide ions. Finally, 10 is ionic salt containing 1D polymeric network of {[SbBr(5)](2-)}(n) anions and (-)[(PMTH(2)(+))2] counter cations in the lattice. The complexes showed mostly a moderate cytostatic activity against a variety of tumor cell lines.

Azobenzene photoisomerization under high external pressures: testing the strength of a light-activated molecular muscle.

The photoinduced isomerization and thermal back relaxation of an azobenzene-functionalized polymer poly(disperse red 1 acrylate) were investigated at increasing external pressures up to 1.5 GPa inside a diamond-anvil spectroscopic cell. The thermal cis-trans isomerization was monitored by laser pump-probe spectroscopy, which demonstrated an increase in the half-life of the isomerization process with increasing pressure. Additionally, the cis content of the photostationary state gradually decreased as a function of pressure, with complete arrest of the trans-cis photoisomerization above 1.5 GPa. The fact that the photoswitching behavior however could still be observed beyond 1 GPa is remarkable and is effectively a measure of the strength of the azobenzene chromophore as an artificial muscle. The changes in the Raman shifts of both trans- and cis-azobenzene were also investigated from ambient pressure up to 4 GPa, and no discontinuities were observed in the pressure vs wavenumber plots indicating no change in phase. The cis-trans photoisomerization of azobenzene was shown however to still be inducible at all the pressures investigated, confirming the suitability of these molecules for high-efficiency light actuation.

Synthesis, Characterization, and Biological Studies of Organotin(IV) Derivatives with o- or p-hydroxybenzoic Acids

Organotin(IV) complexes with o- or p-hydroxybenzoic acids (o-H2BZA or p-H2BZA) of formulae [R2Sn(HL)2] (where H2L = o-H2BZA and R = Me- (1), n-Bu- (2)); [R3Sn(HL)] (where H2L = o-H2BZA and R = n-Bu- (3), Ph- (4) or H2L = p-H2BZA and R = n-Bu- (5), Ph- (6)) were synthesized by reacting a methanolic solution of di- and triorganotin(IV) compounds with an aqueous solution of the ligand (o-H2BZA or p-H2BZA) containing equimolar amounts of potassium hydroxide. The complexes were characterized by elemental analysis, FT-IR, Far-IR, TGA-DTA, FT-Raman, Mössbauer spectroscopy, 1H, 119Sn-NMR, UV/Vis spectroscopy, and Mass spectroscopy. The X-ray crystal structures of complexes 1 and 2 have also been determined. Finally, the influence of these complexes 1–6 upon the catalytic peroxidation of linoleic acid to hydroperoxylinoleic acid by the enzyme lipoxygenase (LOX) was kinetically studied and the results showed that triorganotin(IV) complex 6 has the lowest IC50 value. Also complexes 1–6 were studied for their in vitro cytotoxicity against sarcoma cancer cells (mesenchymal tissue) from the Wistar rat, and the results showed that the complexes have high activity against these cell lines with triphenyltin((IV) complex 4 to be the most active one.

Application of photoacoustic infrared spectroscopy in the forensic analysis of artists' inorganic pigments.

Fourier-transform photoacoustic infrared (PAIR) spectroscopy has been used in the analysis of 12 inorganic pigments commonly in use by artists today, viz., cobalt blue, ultramarine blue, Prussian blue, azurite, malachite, chromium oxide, viridian, cadmium yellow, chrome yellow, iron oxide, yellow ochre and Mars orange. The authenticity of these 12 commercial pigments was first established by recording their Raman spectra. The subsequent PAIR spectra were highly reproducible and matched well in the mid-IR region with previously published data for these pigments. A number of additional overtone and combination bands were also detected that will prove useful in the identification of the pigments in the future. The PAIR technique is a promising and reliable method for the analysis of inorganic pigments, especially since it involves much simpler preparation than is required for conventional IR measurements.

Raman, FTIR, photoacoustic-FTIR and inelastic neutron scattering spectra of alkaline earth and lanthanide salts of hexahydridoruthenate(II), A2RuH6, (A = Ca, Sr, Eu) and their deuterides.

The vibrational spectra (Raman, photoacoustic and Fourier transform infrared and inelastic neutron scattering) of the calcium, strontium and europium salts of hexahydrido- and hexadeuteridoruthenate(II) have been analyzed. All observed fundamental modes and overtone and combination bands are assigned. Density functional theory calculations of the vibrational frequencies assist in the analysis.

High-pressure resonance Raman spectroscopic study of ultramarine blue pigment

The resonance Raman spectrum of ultramarine has been studied as a function of pressure up to 5 GPa. The overtone progressions of the ν(1) fundamental and the combination bands of S(3)(-) and the ν(1) band of S(2)(-) were measured and the pressure dependences were determined. The symmetric stretching mode of S(3)(-) is nearly harmonic. No phase transition was observed over the measured pressure range.

Thermal decomposition studies of the polyhedral oligomeric silsesquioxane, POSSh, and when it is impregnated with the metallocene bis(η5-cyclopentadienyl)zirconium (IV) dichloride or immobilized on silica

Thermal decomposition studies of the free polyhedral oligomeric silsesquioxane, POSSh, and when this compound has been impregnated with Cp2ZrCl2 (Cp = eta5-C5H5) or immobilized on SiO2 were conducted using infrared emission spectroscopy (IES) over a 100-1000 degrees C temperature range and by thermogravimetric analysis (TGA). The organic groups in POSS(h) apparently decompose thermally into Si-CH3, Si-H and other fragments. Upon impregnation with Cp2ZrCl2, however, a different thermal decomposition pathway was followed and new infrared emission bands appeared in the 1000-900 cm(-1) region suggesting the formation of Si-O-Zr moieties. When immobilized on SiO2 and subjected to thermal decomposition, the POSSh compound lost its organic groups and the inorganic structure remaining was incorporated into the SiO2 framework.

Raman, FTIR, photoacoustic-infrared, and inelastic neutron scattering spectra of ternary metal hydride salts A2MH5, (A = Ca, Sr, Eu; M = Ir, Rh) and their deuterides.

The vibrational spectra of the ternary metal hydride (deuteride) salts, A(2)MH(5) and A(2)MD(5), where A = calcium, strontium and europium and M = iridium(I) and rhodium(I), have been assigned using Raman, Fourier transform infrared, photoacoustic infrared, and inelastic neutron scattering spectroscopies and density functional theory (DFT) calculations. The wavenumbers of the infrared-active stretching vibrations depend upon the ionization energies of the central metal atom and the cation. The phase transition in calcium pentahydridoiridate(I) was studied as a function of temperature and pressure.

Micro-Raman high-pressure investigation on the malaria pigment hematin anhydride (β-hematin)

The effect of pressure on the Raman and fluorescence spectra of hematin anhydride (β-hematin) is reported. In a diamond-anvil cell, DAC, with applied pressures up to 41 kbar, the Raman spectrum undergoes a series of intensity enhancements and increases in energy for many of the Raman-active bands up to a pressure of ~27 kbar. At higher pressures, there is either a leveling out or a decrease in the energies of these vibrational modes. The fluorescence bands also undergo a series of pressure- sensitive changes where, up to 10 kbar, there is a marked quenching of the intensity of the emissive bands, which is accompanied by a net increase in energy of the vibrational bands. The results are interpreted in terms of a high-pressure phase change, to account for the Raman shifts, and a separate defect or surface site of the emissive state, which is more efficiently quenched at higher pressure.