A Brief Review on the Use of Chelation Agents in Sol-gel Synthesis with Emphasis on β-Diketones and β-Ketoesters

Metal alkoxides are the most commonly used sol-gel process precursors. Most alkoxides show excessive reactivity towards water. That leads to rapid hydrolysis, metal hydroxide formation, and immediate precipitation. The reactivity of alkoxides can be reduced by modification with chelation agents. Chelation influences the gelation process, which is reflected in gel structure and properties of the final material. In this short review, the chelation process, the oligomerization phenomena, and the influence of the chelating agent on the gel structure are discussed. Peculiarities of the use of FTIR and NMR, as methods particularly suitable for the investigation of chelation process, are described taking ethyl acetoacetate as an example

Thermophysical Comparison of Five Commercial Paraffin Waxes as Latent Heat Storage Materials

Thermophysical properties of phase change materials (PCM) are of utmost importance in latent heat thermal energy storage (LHTES) applications. Therefore, an experimental study is conducted in order to determine thermophysical properties of five technical grade paraffin waxes produced by major Croatian oil company, INA d.d. Rijeka. The temperatures and enthalpies of melting and solidification (latent heat capacity) and specific heat capacities of solid and liquid paraffin waxes were measured by differential scanning calorimetry (DSC). The thermal diffusivity of paraffin waxes was determined utilizing transient method. The importance of eliminating phase transformation interferences to thermophysical properties determination is addressed. The densities and the coefficient of thermal expansion were measured using Archimedes methods. A self-adopted simple and inexpensive laboratory procedure for the determination of liquid density as a temperature function is presented. Finally, the thermal conductivities have been calculated from measured densities, heat capacities and diffusivities. Based on results obtained, the investigated paraffin waxes were evaluated in regard to their applicability as PCM for LHTES

Thermal evolution process, properties and photocatalytic activity of sol-gel derived nanocrystalline anatase in dye degradation process

Nanocrystalline anatase aimed to be used as a photocatalyst for dye degradation processes in industrial effluents and has been prepared and investigated. Amorphous titania gel has been prepared using sol–gel process by slow hydrolysis of titanium n–butoxide. The prepared gel has been investigated using Fourier–Transformed Infra–Red Spectroscopy (FTIR), Powder X–ray Diffraction (PXRD), Differential Thermal Analysis (DTA), Thermo–Gravimetric Analysis (TGA), N2 gas adsorption–desorption isotherms and Diffuse Reflectance UV–Vis Spectroscopy (DRS). It was determined that the amorphous gel was comprised of non-hydrolyzed butoxy groups as well as hydroxyl groups bonded to titanium. The thermal evolution of gel is consisted of five steps: elimination of adsorbed water and butanol in temperature range between room temperature and 200 °C, decomposition and elimination of butoxy groups between 200 and 300°C. The crystallization of anatase centered at 404°C, transformation to rutile starting from 540 °C and oxidation of char and tar above 600°C. Thermal treatment of gel at 350 °C for 2 h yields with pure nanocrystalline anatase with average crystallite size of 13.2±0.2 nm, specific surface area of 65.48 m2 g–1 and bandgap, of 3.24 eV. The preliminary assessment of prepared catalyst photocatalytic activity was obtained through degradation process of methylene blue dye under UV light and the 99 % degradation of dye took place within 150 min

The novel nucleobase-ferrocene hybrids: synthesis, structural characterization and electrochemistry

U ovom radu opisana je sinteza novih hibrida nukleobaza i ferocena te njihova strukturna karaktrizacija i elektrokemijska ispitivanja. Reakcijom N-alkiliranja uracilnog ili citozinskog prstena sintetizirani su N-1 i/ili N-3 derivati s propargilnim ili butenilnim supstituentima na uracilnom (1, 4, 7, 8 i 19-21) ili citozinskom (15-17) prstenu koji su nadalje uz natrijev azid prevedeni u 4-azidobutenilne derivate 5, 9, 10 i 23. Paladijem kataliziranom Sonogashira-inom reakcijom unakrsnog povezivanja 5-jod-N-1-propargiluracila (1) s etinilferocenom pripravljen je hibrid 5-joduracila i ferocena (2) premošten etinilnom poveznicom u položaju 5 uracila. Hibridi nukleobaza i 4-ferocenil-1,2,3-triazola (3, 6, 11, 12, 14 i 24) pripravljeni su mikrovalovima potpomognutom „klik“ reakcijom 4-azidobutenskih derivata uracila i citozina s etinilferocenom uz Cu katalizator. „Klik“ reakcijom N-propargiliranih derivata nukleobaza (1 i 13) s azidoferocenom uveden je 1,2,3-triazolni prsten u položaj N-1 i N-3 pri čemu su pripravljeni 4-ferocenil–5-joduracil–1,2,3-triazolni hibrid (3) i N-4-benzoilcitozinski hibrid 4-ferocenil-1,2,3-triazola (14). Strukturna karakerizacija hibrida nukleobaza i ferocena provedena je 1H NMR spektroskopijom. Elektrokemijska ispitivanja novosintetiziranih spojeva provedena su cikličkom voltametrijom.This paper describes the synthesis of new nucleobase and ferrocene hybrids and their structural characterization and electrochemistry. N-1 and/or N-3 derivtives with propargyl or butenyl side chain on uracil (1, 4, 7, 8 and 19-21) or cytosine (15-17) ring were synthesized by N-alkylation reaction, which were with sodium azide converted to 4-azidobutenyl derivatives 5, 9, 10 and 23. The palladium catalyzed cross-coupling Sonogashira reaction of 5-iodo-N-1-propargyluracil (1) with ethinylferrocene gave hybrid of 5-iodouracil and ferrocene (2) bridged with the ethynyl linkage at position 5 of uracil. Hybrids of nucleobases and 4-ferrocenyl-1,2,3-triazoles (3, 6, 11, 12, 14 and 24) were prepared by "click" reaction assisted by microwave irradiation of 4-azidobutene derivatives of uracil and cytosine with ethynylferrocene in the presence of Cu catalyst. 1,2,3-triazole ring was introduced in N-1 and N-3 position by "click" reaction of the N-propargylated nucleobase derivatives (1 and 13) with azidoferrocene where 4-ferocenyl-5-ioduracil-1,3,3-triazole hybrid (3) and N-4-benzoylcytosine 4-ferocenyl-1,2,3-triazole hybrid (14) were prepared. Structural characterization of nucleobase and ferrocene hybrides was performed using 1H NMR spectroscopy. Electrochemical evaluation of novel compounds was performed by cyclic voltammetry

On the Temperature Corresponding to a = 0.632 in Non-isothermal JMA Kinetics

The expression for rate, da/dT, of the nucleation and growth (NG) process under non-isothermal conditions, as described by the Johnson-Mehl-Avrami (JMA) kinetic model, served as the basis for a detailed study of a class of functions F(m) = (da/dT)Tm, where m ÎÂ. Studies of the fractional conversion, a, of the NG process at the temperature of the maximum of function F(m), T = T(m), have shown that when reduced activation energy, x = E/RT, approaches infinity (x®¥), fractional conversion, a, at the temperature corresponding to the maximum of function F(m), a(m), converges to a = 0.632, for any value of m. It has been further shown that fractional conversion, a, for the NG process is equal to a = 0.632 at the temperature corresponding to the maximum of function F(m) = (da/dT)Tm for the particular value of parameter m from the interval: 1 £ m £ 2

Characterization of Sol-gel Derived Cobalt-doped Willemite via 2D Correlation Spectroscopy

Cobalt blue is one of the world’s most famous blue pigments, but it presents a threat to human health since it is toxic when inhaled or ingested. A safer and environmentally preferable way of obtaining cobalt blue-like pigments is doping of various nontoxic compounds with small amounts of cobalt. In this work, doping of zinc silicate (willemite, Zn2SiO4) was carried out with 5, 10, and 15 mol% of Co with the aim of obtaining Zn2–xCoxSiO4 solid solution. Thermal properties of sol-gel derived samples were examined with simultaneous differential thermal and thermogravimetric analysis (DTA/TGA), which showed dehydration, decomposition, and burning effects, accompanied with mass loss and willemite crystallization effect at 800 °C. X-ray powder diffraction analysis (XRD) indicated the formation of willemite phase at 800 °C, accompanied with ZnO phase and increase in willemite crystallinity with annealing temperature rise from 800 to 1100 °C. Fourier transform infrared spectroscopy (FTIR) showed characteristic bands for present oxides and their bonds along with adsorbed water and carbon dioxide. Colouration of prepared samples changed with annealing temperature, whereas higher Co concentrations and temperatures accentuated the intense blue colour. Diffuse reflectance spectroscopy (DRS) revealed an increase in absorbance with annealing temperature and specific bands as a result of different Co coordination present in the samples. The 2D correlation analysis of FTIR and UV-Vis spectra of the samples thermally treated at various temperatures was utilized to investigate and correlate the changes in the structure with the rise of the annealing temperature. The obtained correlation facilitated the finding of optimal process parameters for the desired pigment quality. This work is licensed under a Creative Commons Attribution 4.0 International License

Application of a Numerical Method for the Analysis of Metglas 2826 MB Crystallization Kinetics

Crystallization kinetics of y-FeNiMo solid solution in Metglas 2826 MB was studied by isothermal differential scanning calorimetry (DSC). The Johnson-Mehl-Avrami (JMA) equation was used to describe the crystallization process. In order to calculate the kinetic parameters, a new model of the numerical analysis of isothermally obtained DSC data was successfully applied. For the purposes of method evaluation, the classical analytical method of data analysis was also performed. The apparent activation energies obtained were (280 ± 22) kJ mol-1 and (296 ± 23) kJ mol-1 for the analytical and numerical methods, respectively. The Avrami exponents obtained by both methods lie between 1.75 and 1.95

Synthesis of C-5 substituted cytosine derivatives by palladium catalysed reactions

U ovom radu opisana je sinteza C-5 supstituiranih citozinskih derivata paladijem kataliziranim reakcijama. Sonogashira-inom reakcijom unakrsnog spajanja N-4-benzoil-5-jodcitozin (1) s terminalnim alkinima dobiveni su 5-alkinilni derivati citozina (2−4) te C-6-alkilni derivat pirolo[2,3-d]pirimidina 5. Triazolni prsten u položaj N-1 citozina uveden je „klik“ reakcijom potpomognutom mikrovalovima N-1-propagiliranog derivata citozina 6 s odgovarajućim azidima pri čemu su nastali spojevi 7−9. 5-alkinilni derivati citozina 10−11 s triazolnim supstituentom u položaju N-1 pripravljeni su Sonogashira-inom reakcijom 5-jod-N-1-metiltriazolnog derivata citozina 7 s odgovarajućim terminalnim alkinima. Strukturna karakterizacija novih derivata citozina provedena je 1H NMR spektroskopijom. Farmakološki učinci i moguće biološke mete predviđeni su in silico analizom (PASS). Citostatska ispitivanja in vitro novosintetiziranih spojeva 2, 5 i 7 provedena su na staničnim linijama HeLa (adenokarcinom vrata maternice), CaCo-2 (adenokarcinom debelog crijeva), Raji (Burkittov limfom) i K562 (kronična mijeloidna leukemija u blastičnoj fazi). Spoj 7 pokazao je umjereno djelovanje protiv stanične linije K562. Kako bi se odredili mogući mehanizmi bioloških djelovanja spojeva ispitana je interakcija spoja 7 s ct-DNA UV/Vis i fluorescencijskom spektroskopijom.This paper describes the synthesis of C-5 substituted cytosine derivatives by palladium catalysed reaction. 5-alkyl citosyne derivatives 2−4 and C-5 alkynylpyrolo[2,3-d]pirimidine derivative 6 have been synthesized by Sonogashira cross-coupling reaction of N-4-benzoyl-5-iodinecytosine (1) with terminal alkynes. N-1 triazole ring was introduced into N-1 position of cytosine derivatives 7−9 using „click“ reaction with corresponding azides under microvawe irradiation. 5-alkyl cytosine derivatives 10−11 with triazole substituent in position N-1 have been synthesized by Sonogashira cross coupling of 5-iodo-N-1-methyltriazole cytosine (7) with corresponding terminal alkyne. Structural characterization of synthesized compounds was conducted using 1H NMR spectroscopy. Pharmacological effects and potential bilogical targets of novel compounds have been predicted by in silico analysis (PASS). Cytostatic evaluation in vitro was preformed against human malignant tumor cells: HeLa, CaCo-2, Raji and K562. Compound 7 showed moderate cytotoxic effect against K562 tumor cell lines. Interaction of compound 7 with ct-DNA was performed by UV/Vis and fluorescence spectroscopy in order to predict mechanism of cytostatic activity