Katalin Mészáros Szécsényi

Structural, spectroscopic and computational studies of the HgL2Cl2 complex (L = 3,5-dimethyl-1-thiocarboxamide pyrazole) and the crystal structure of L

In the present paper we report the synthesis as well as the structural and vibrational characterisation of the HgL2Cl2 complex (L = 3,5-dimethyl-1-thiocarboxamide). The crystal and molecular structures of both L and the HgL2Cl2 complex were determined by single-crystal X-ray diffraction. The coordination propensity of L to HgCl2 was explored by quantum chemical calculations. We found the preference of the monodentate coordination of L to HgCl2 through the sulfur atom (instead of the “pyridine” nitrogen) to be in agreement with Pearson’s acid–base character of the atoms involved and the steric effects. The vibrational properties of HgL2Cl2 were evaluated by a joint FT-IR and quantum chemical analysis. In addition, the thermal decomposition of the complex and ligand is reported.

Properties of baked foams from citric acid modified cassava starch and native cassava starch blends

Starch foams from native cassava starch (NS) and citric acid modified cassava starch (CNS) were prepared using baking processes with blend ratios of 80/20, 60/40, 50/50, 40/60 and 20/80. The density, thickness, morphology, thermal stability and water absorption of the NS, CNS and blended starch foams were determined. The ratio of the two starch components had a significant influence on the density and thickness of the blended starch foams. All blended starch foams showed good water resistance. Moreover, the morphology of the blended starch foam with the NS/CNS ratio of 50/50 showed a more ordered distribution of cell sizes with thicker cell walls than for the NS and CNS foams. The thermal stability of the blended starch foams was somewhat lower than the stability of the NS foam but not to the extent that it affected any potential practical applications.

Copper(II) Complexes with Reduced Schiff Base: Synthesis, Spectroscopic, Thermal, X-Ray, and Cytotoxic Studies of Novel Copper(II) Complexes with an Arylpyrazole Ligand

The synthesis of a novel arylpyrazole-derived ligand, 1,2-bis[(1,3-diphenylpyrazol-4-yl)methyl]diaminoethane (Ph4Pz2mde), and its complexes prepared with CuCl2 [Cu(Ph4Pz2mde)Cl2(MeOH)] 1, CuBr2 [Cu(Ph4Pz2mde)Br2(MeOH)] 2, from MeOH, and [Cu(Ph4Pz2mde)Cl2(DMF)] 3, from a mixture of MeOH and DMF, are described. The complexes are characterized by elemental and thermal analysis and FT-IR spectroscopy, while the 1H and 13C NMR assignments are given for the ligand. The crystal and molecular structure of [Cu(Ph4Pz2mde)Cl2(DMF)] was determined by single-crystal X-ray diffraction. In-vitro cytotoxicity of the Ph4Pz2mde ligand and two copper(ii) complexes was obtained using sulforhodamine B (SRB) treatment against three human tumour cell lines: HeLa (epitheloid carcinoma of cervix), MCF-7 (breast adenocarcinoma), and MRC-5 (lung fetal fibroblasts).

Synthesis, Structural, DFT, and Cytotoxicity Studies of CuII and NiII Complexes with 3-Aminopyrazole Derivatives*.

Template synthesis of N,N′-bis(4-acetyl-5-methylpyrazole-3-yl)formamidine (ampf) was performed starting from 4-acetyl-3-amino-5-methylpyrazole (aamp) and CH(OC2H5)3 in methanol in the presence of CuCl2, Cu(NO3)2, or Ni(NO3)2. The ligand was isolated in coordinated form as [Cu(ampf)Cl2], [Cu(ampf)(MeOH)(NO3)2]MeOH, and [Ni(ampf)(MeOH)2(NO3)]NO3 correspondingly. The compounds were characterized by elemental analysis, Fourier-transform IR and electronic spectroscopy, thermal analysis, single-crystal X-ray diffraction, and quantum chemical (density functional theory) calculations. The density functional theory calculations provided information on the metal–ligand interactions in the complexes and assisted the assignment of the FT-IR spectra. The antiproliferative activity of the complexes and the ligand precursor, aamp, was tested against human myelogenous leukaemia K562, colon adenocarcinoma HT29, and cervix carcinoma HeLa.

Investigation of 1,2,3-trialkylimidazolium ionic liquids: experiment and density functional theory calculations

Physico-chemical properties, thermal stability and bonding in 1,2,3-trialkylimidazolium based ionic liquids (ILs) were investigated by viscosity and density measurements together with thermogravimetric analysis (TGA) and IR spectroscopy. The obtained results were compared to those obtained for the corresponding 1,3-dialkylimidazolium based ILs. To obtain more insight into the influence of the methylation at position C-2 of the imidazolium ion, IR spectra were calculated with the help of density functional theory (DFT) calculations. The reduction in bonding intensity between ions was confirmed as a consequence of chain reduction and methylation. In this regard, DFT calculations indicated a much higher influence of methylation and these results were explained through the analysis of inter-molecular non-covalent interactions (NCIs). Intra-molecular NCIs together with quantum molecular descriptors were also applied for the explanation of thermal stability of the investigated ILs.

Crystal structure, thermal behavior, and microbiological activity of a thiosemicarbazide-type ligand and its cobalt complexes

The synthesis of a potentially bioactive mixed-valence CoIII/CoII complex with 2-acetylpyridine S-methylisothiosemicarbazone (HL) ligand is described. The crystal and molecular structure of the formed [CoIIIL2][CoIICl3py]·Me2CO (I) compound (py stands for pyridine) is determined by single-crystal X-ray crystallography. It’s thermal decomposition along with the decomposition of the ligand and six structurally related complexes with formulas [CoL2]NO3·MeOH (1), [CoL2]Br·MeOH (2), [CoL2]HSO4·MeOH (3), [CoL2]2[CoII(NCS)4] (4), [Co(HL)(L)]I2·2MeOH (5), and [Co(HL)(L)][CoIICl4]·MeOH (6) was determined by simultaneous TG/DSC measurements. The decomposition pattern is evaluated using TG/DTA-MS data. The results were related to the solvent/moisture content and the decomposition mechanism of the compounds. The antimicrobial activity of the ligand and of all the complexes was tested in vitro for selected gram-negative and gram-positive bacteria and fungi. The activity of the ligand against all tested bacteria is comparable with those obtained for standard antibiotics, while it is less active against fungi. Surprisingly, the activity of the complexes is very low. The low antimicrobial activity of the complexes may be in connection with their high thermodynamic and kinetic inertness in solution. The results are also supported by the relatively high thermal stability of the complexes.

Synthesis, structure and thermokinetic studies on perchlorate salts of metal complexes containing a formamidine-type ligand

Two formamidine-type transition metal complexes of N,N′-bis(4-acetyl-5-methylpyrazol-3-yl)formamidine (ampf) have been synthesized by a template reaction in methanolic solution of the corresponding metal perchlorates and 4-acetyl-3-amino-5-methylpyrazole (aamp) precursor in the presence of triethyl orthoformate. Compounds of composition [M(ampf)(H2O)3](ClO4)2·H2O (M = CoII, NiII) have been formed. The crystal and molecular structures of the compounds have been determined by X-ray crystallography. The complexes were characterized by IR spectroscopy. The thermal stability and the decomposition kinetics of the two potential explosives were determined by thermal methods.

Synthesis, characterization and thermal behavior of copper(II) complexes with pyridoxal thiosemi (PLTSC)- and S-methylisothiosemicarbazone (PLITSC)

The syntheses of complexes of Cu(II) with biological active ligand, pyridoxal thiosemicarbazone (PLTSC) and its derivative, pyridoxal S-methylisothiosemicarbazone, are described. All coordination compounds were characterized by elemental analysis, molar conductivity and infrared spectra. The crystal and molecular structure of complexes [{Cu(μ-PLTSC)(H2O)}2](SO4)2·6H2O (2) and [{Cu(μ-PLTSC)(H2O)}2](SO4)2·2H2O (2a) is determined by single-crystal X-ray crystallography, too. The thermal decomposition of all the ligands and complexes was determined by simultaneous TG/DSC measurements. The decomposition mechanisms were compared and analyzed from the aspects of the relationships between the structures of the compounds and their thermal decomposition pattern.

Determination of natural rubber/poly(methyl methacrylate) blend composition by TG/DSC technique

Natural rubber/Poly(methyl methacrylate) or NR/PMMA blends were prepared by polymerization of the methyl methacrylate monomer and natural rubber latex. Their PMMA content before and after Soxhlet extraction was determined by 1H-NMR spectrometry. In this work, the thermal properties of the same NR/PMMA blends were determined using simultaneous thermogravimetry/differential scanning calorimetry (TG/DSC). The composition of the samples was determined on the basis of the derivative thermogravimetric (DTG) data. As the decomposition of the samples took place by simultaneous processes, by varying the heating rates the shape of the DTG curves was optimized for the deconvolution into two individual peaks of the two-component polymer system. Assuming the compensation of the errors, from the deconvoluted curves the amounts of the components in the blends were calculated. TG/MS data showed that the deconvolution was justified as the first part of the DTG curve could be related mainly to the decomposition of NR, while at higher temperatures, the decomposition of PMMA took place. The thermogravimetric method of composition determination of the polymer is simple and rapid, and in addition, is cheap compared with the costs of other instrumental techniques. The results were acceptable when compared with the corresponding data of 1H-NMR studies, too.

emf Studies of silver nitrate-potassium nitrate melts

The activity coefficients of silver nitrate in binary melts of AgNO3-KNO3 were determined by emf measurements in a formation cell consisting of a silver and a nitrate electrode, in a temperature range of 513-583 K and in the concentration range allowed by the melting point of the mixture. Using a polynomial expression of the excess chemical potential, the excess Gibbs function and the characteristic constants of the investigated binary molten salt system were calculated. The excess molar entropy was calculated by combining the excess Gibbs function with calorimetric data on the excess enthalpy of mixing from the literature. The excess chemical functions were represented by orthogonal series involving Legendre polynomials, which enabled a comparison of the characteristic constants for different binary molten salt systems. The conformal ionic solution theory has been tested with respect to its capability to predict the excess chemical potentials of a binary additive system.