Berta Holló

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.

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.

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.

Anion-/cation-directed reaction routes to polymorphic forms of a pyrazole-type ligand and its coordination compounds with zinc. Key structural differences between polymorphs’

Abstract Synthetic paths toward the two polymorphs of a monohydrate, one anhydrous polymorph of 1-carboxamidino-5-hydroxy-3-methylpyrazole (hcmp) and two polymorphs of zinc complexes containing hcmp ligand are presented. By choosing ions which are not part of the final product, it is possible to direct the synthesis toward the particular polymorph. In all three modifications of hcmp, the same hydrogen bonding motif appears, leading to formation of similar molecular chains. Differences arise due to different modes of chain aggregation and the presence of solvent water. Analysis of the crystal packing and the energetic features of hcmp polymorphs is made using the PIXEL model. The thermal decomposition processes are examined using differential scanning calorimetry and thermogravimetry. Analysis of crystal packing in the two polymorphs of zinc complex suggests the key role of the hydrogen bonding capacity of the aqua ligand for the appearance of the two polymorphic forms. In both polymorphs of zinc complex, stacking interactions have an important role. However, the enhanced hydrogen bonding capacity of the aqua ligand influences the formation of multistacking arrangement.

Interactions of Schiff base type compounds and their coordination complexes with the anticancer drug cisplatin

There is a complex interplay between the structural and other physicochemical properties of new compounds and the molecules in living organisms. To understand the mechanism of the interactions at the molecular level, the correlations between the selected properties and their biological responses have to be examined. With this aim, in this paper, density functional theory (DFT) and LMP2 calculations were carried out for the 2-acetylpyridine-aminoguanidine ligand, L, and its copper(II) complexes containing different monoanionic ligands. In addition, several parameters, most frequently used for the prediction of drug-likeness of new compounds, were calculated. The influence of the compounds on the effectiveness of the reference chemotherapeutic drug cisplatin was determined in vitro, by comparison of their combination indices (CIs). The drug interactions between cisplatin and the earlier synthesized ligands L1 (bis(3-chloropyridazine-6-hydrazone)-2,6-diacetylpyridine) and L2 (bis(phthalazine-1-hydrazone)-2,6-diacetylpyridine) and their Co(III), Ni(II), Cu(II) and Zn(II) complexes, respectively, were also measured. The ligands L, L2, and L3, as well as their complexes, showed different interactions in combination with cisplatin from strong antagonism of L to strong synergism of 4-L1 and 4-L2. The experimental results and the calculated parameters were analyzed to evaluate their correlation with the measured interactions. The thermal stability of the L·2HCl ligand and its four copper(II) complexes was determined and the thermal stability data were correlated to selected calculated molecular descriptors.

Synthesis and characterization of copper, nickel, cobalt, zinc complexes with 4-nitro-3-pyrazolecarboxylic acid ligand

In the continuation of our systematic research of pyrazole coordination compounds, complexes of Cu(II), Ni(II), Co(II) and Zn(II) with 4-nitro-3-pyrazolecarboxylic acid ligand (L) were synthesized in the reaction of warm ethanolic solutions of the ligand and CuCl2·2H2O, Ni(CH3COO)2, CoCl2·6H2O and Zn(CH3COO)2, mixed in the metal-to-ligand ratio of 1:2. As the compounds could not be obtained in the form suitable for single-crystal structure analysis, their bis(ligand) structures, ML2 (M = CuII, NiII, CoII and ZnII) were proposed on the basis of elemental analysis, IR spectrometry, conductometric and TG–MS measurements. The low conductivity of the compounds additionally supports the deprotonation of the ligand and the formation of neutral complexes. The solvent content was calculated using the thermogravimetric (TG) data. According to TG data, the copper(II) compound crystallizes with 8 while nickel(II) complex with 4 water molecules, CuL2·8H2O, NiL2·4H2O. Complexes of Co(II) and Zn(II) contain 1 and 1.5 water molecules. Despite the differences in solvation properties, the high similarity in the course of the decomposition refers to the similar coordination mode of the organic ligand. The crystal and molecular structures of HL·H2O and NH4[LHL] were determined by single-crystal X-ray structure analysis. Biological research based on determining the inhibition effect of commercial fungicide Cabrio top, ligand, and all newly synthesized complexes on Ph. viticola has been carried out using the phytosanitary method.

Synthesis, spectroscopic and thermal characterization of new metal-containing isocyanate-based polymers

AbstractTo overcome the polyurethanes low heat resistance and obtain new PU-based materials, in continuation of our research in the synthesis of hybrid polymers, we report here the synthesis of metal-containing polyurethanes formed in the reaction of pyrazole-based coordination compounds [Cuampf(NO3)2MeOH]·MeOH and [CuampfCl2] where ampf denotes N,N′-bis(4-acetyl-5-methyl pyrazole-3-yl)formamidine ligand, and two isocyanates, 1,6-diisocyanatohexane (HDI) and Bayhydur 3100 (Bay, a hydrophilic linear polymer based on 1,6-diisocyanatohexane) using dibutyltin-dilaurate catalyst. The formed materials were characterized by FT-IR spectrometry and thermal methods. The formation of the new polymers, besides the corresponding FT-IR spectra, was proved by differential scanning calorimetry (DSC) determining their glass transition temperatures. The thermal decomposition of the materials was examined by simultaneous thermogravimetric (TG) and DSC measurement. For the evaluation of the decomposition mechanism, the data obtained by coupled TG–mass spectrometric (MS) measurements were used. The thermal stability of the hybrid materials based on HDI was found substantially higher than that of the pure 1,6-diisocyanatohexane and decomposition of hybrid materials was more complex, while in the reaction of the metal complexes with Bay the thermal properties of the obtained hybrid polymers were changed only slightly, referring to a small amount of incorporated complexes.