Canan Unaleroglu

Monodentate chromium(III) ascorbate complexes prepared via chromate reduction in THF

ABSTRACT Two new Cr(III)-ascorbate complexes, K[Cr(C6H7O6)2(OH)2-(H2O2)2]·3H2O (1) and K2[Cr(C6H7O6)3(OH)2(H2O)]·2H2O (2), have been prepared by reducing chromate with L-ascorbic acid in aqueous THF. The complexes have been characterized by various analytical and spectroscopic methods (UV/Vis, FTIR, 13C NMR and EI MS) and by thermal and magnetic measurements. Experimental results indicated a distorted octahedral environment around the Cr(III) centers and the coordination mode of ascorbic acid has been shown to be monodentate through its O(3) atom by NMR studies. The analytical and spectroscopic data available allowed the proposal of structural formulae for (1) and (2).

Synthesis and characterization of transition metal-vitamin B13 complexes mixed with a co-vitamin

The synthesis and structural characterization of mixed vitamin-metal complexes are reported. A complex bearing two vitamins (B3 and B13) on the same metal centre, nicotinamide(orotato)nickel(II) pentahydrate, has been prepared and characterised by single-crystal X-ray diffraction methods. A complex of Cr(III) with vitamins C and B13, bis(ascorbato)orotatochromium(III) dihydrate, has been isolated and its nature investigated by means IR, 13C NMR, API-ES and thermogravimetric measurements. Theoretical calculations have been performed to propose a structure in accord with results obtained.

SYNTHESIS AND CHARACTERIZATION OF COPPER ASCORBATE

The preparation of copper ascorbate in CH2Cl2 is described. The reaction between copper(II) methoxide and L-ascorbic acid in the presence of N,N,N′,N′-tetramethylethylenediamine (TMEDA) and under strictly anaerobic conditions leads to the formation of a stable Cu(II)-ascorbate complex. No redox reaction takes place. Spectroscopic evidence suggest that the compound is polymeric where Cu(II) is chelated by the enolic oxygens of one ascorbate unit and the side chain alcoholic oxygens of another.

Ascorbic acid as a potential masking agent in the tanning process. Olated chromium complexes involving ligating ascorbate and bridging sulfate groups

Two polynuclear complexes, a dimer and a tetramer, involving sulfate and hydroxo bridges and ligating ascorbate were isolated from aqueous solutions. Structural formulae are proposed on the basis of microanalytical and thermal analysis results, i.r., 13C-n.m.r., mass spectral data and magnetic measurements.

pH-Independent decomposition reactions of L-ascorbic acid in aqueous metal solutions. 2. Imaging by scanning tunneling microscopy

Abstract STM images of aqueous solutions of L-ascorbic acid containing Gd 3 ions at pH values of 2, 6 and 12 have been recorded periodically after drying the samples on gold coated mica. The results have revealed that the organisations of the AA molecules and metal ions show different features throughout the conversion of Gd-ascorbate complexes to Gd-oxalates.

Design, synthesis and cytotoxic evaluation of β-aryl-α-dimethoxyphosphoryl-γ-lactams

New β-aryl-α-dimethoxyphosphoryl-γ-lactams 4a, b were designed and synthesized through the intra-molecular cyclization of 3a, b obtained from the addition reaction of methyl 2-(dimethoxyphosphoryl)acetate to (E)-2-(2-nitrovinyl)thiophene and (E)-2-(2-nitrovinyl)furan, respectively. The in vitro cytotoxicity of these compounds was evaluated against human breast cancer (MCF-7), rat glioblastoma (C6), prostate cancer (PC3), neuroblastoma (SHSY-5Y), and mouse fibroblast cell lines (L929). Dimethyl (4-(furan-2-yl)-2-oxopyrrolidin-3-yl)phosphonate (4b) was found to have cytotoxic activity towards MCF-7 and PC3 cell lines at the concentration values above 5 mM and 6 mM, respectively (IC50 values of MCF-7, 5.92 ± 1.86; PC3, 6.70 ± 2.10 mM). Dimethyl (2-oxo-4-(thiophen-2-yl)pyrrolidin-3-yl)phosphonate (4a) only decreased the viability of MCF-7 cells at 8 mM concentration (IC50 value of MCF-7 5.67 ± 1.70 in mM). In addition 4a, b had shown no significant cytotoxic effect on C6, SHSY-5Y and L929 cell lines.

Access to pyrrole-based heterocyclic compounds via addition of pyrrole to C=C and C=N bonds

Abstract A series of metal triflate-catalyzed addition reactions of pyrrole to C=C and C=N bonds have been investigated to access pyrrole-based heterocyclic compounds. The addition of pyrrole to different α,β-unsaturated compounds or N-tosyl imines afforded suitable structures for the construction of [5-5] bicyclic systems or porphyrins, respectively. Intramolecular cyclization reactions were applied for the synthesis of pyrrolizine derivatives. In the other reaction mode, intermolecular cyclization reactions gave A4- and trans-A2B2-meso-substituted porphyrins under mild reaction conditions with low scrambling.

A facile synthesis and characterization of the novel 2,2-dichloro-1-[3-(2,2-dichloro-acetyl)-2-(4-methoxy-phenyl)-imidazolidin-1-yl]- ethanone

ABSTRACT The synthesis of (2,2-dichloro-1-[3-(2,2-dichloro-acetyl)-2-(4-methoxy-phenyl)-imidazolidin-1-yl]-ethanone by a facile one-pot reaction between N,N′-bis(4-methoxy-benzylidene)-ethane-1,2-diamine and dichloroacetyl chloride is described. The structure was confirmed by 1H NMR, MS and FTIR techniques and X-ray crystallography.

Selective synthesis of 5-aryl-10-(nitromethyl) substituted 15-azatripyrrane, 15-oxatripyrrane and 15-thiatripyrrane: access to nitromethyl functionalized A3B-porphyrins

A chemical strategy toward the selective synthesis of unsymmetrical tripyrranes was developed for the formation of meso-aryl and -nitromethyl substituted A3B porphyrins. The iodine catalyzed addition of meso-substituted dipyrromethanes to nitrovinylarenes to generate unsymmetrical 5-aryl-10-(nitromethyl) substituted 15-azatripyrranes, 15-oxatripyrranes and 15-thiatripyrrane under mild conditions has been investigated. The multicomponent reactions of 15-azatripyrranes provided the construction of meso-aryl and -nitromethyl substituted A3B-porphyrins. To the best of our knowledge, the first examples of 5-aryl-10-(nitromethyl) substituted 15-azatripyrranes, 15-oxatripyrranes and 15-thiatripyrrane, and 5-(nitromethyl)-10,15,20-tris(aryl)porphyrins are introduced in this study.

Rationally Designed Fluorescent pH Sensors for Measurements in Extremely Alkaline Media

We investigated the pKa increasing effects on meso-phenol BODIPY to achieve fluorescent pH sensors working in extreme alkalinity. We demonstrated the effects of substituents on meso, α, γ and position of the hydroxyl group on pKa. By considering these parameters, we developed pH sensors working above 11.0 in aqueous medium (ethanol/water 1:1). One of these sensors had a pKa of 12.0 and enabled the measurement of pH up to 13.6. This highly photostable and bright sensor compound could be synthesized easily from cheap starting materials.