Catalytic properties of cesium salts of 12-molybdophosphoric acid supported on SBA-15 mesoporous silica

The Cs salt of molybdophosphoric acid CS2.5H0.5PM012O40 (CsHPM) was supported on SBA15 in the concentration of 20, 30 and 40 wt. % loadings. The structure and texture of these CsHPM/SBA-15 composites were studied by XRD, FT-IR and micro-Raman spectroscopy, BET and pore size distribution, SEM-EDS. Thermal stability was investigated by thermo gravimetric analysis (TGA), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The dehydration of ethanol was used to probe the catalytic properties of the CsHPM samples incorporated on the silica matrix. The main reaction products obtained on acid (dehydration) catalytic centres were ethylene and diethyl ether, and respectively acetaldehyde which was obtained on redox (dehydrogenation) catalytic centres

Mononuclear Cu(II) complexes of novel salicylidene Schiff bases: synthesis and mesogenic properties

Two new Schiff base ligands 1 and 2 (where 1 = 4-(2-hydroxybenzilidenamino)-phenyl-4-(decyloxy)-2-(pent-4-enyloxy)benzoate, 2 = 4-(4-(decyloxy)-2-hydroxybenziliden amino)-phenyl-4-(decyloxy)-2-(pent-4-enyloxy)benzoate) and their copper (Cu)(II) complexes have been synthesised and characterised. The derivatives were fully characterised structurally, and their mesomorphic behaviour was investigated by polarised optical microscopyand differential scanning calorimetry. The structure of Cu(II) complex having 1 as ligand (3) was determined by X-ray diffraction. The Schiff base ligands exhibit enantiotropic nematic phases, the Cu(II) complex 4 shows monotropic nematic phase behaviour, while compound 3 does not show mesomorphism

Homoleptic and heteroleptic pt(II) complexes with potential biological activity

Metal complexes used as pharmaceuticals have received great attention because of their potential biological activity. The chemistry of platinum(II) complexes has been widely developed since the cytostatic activity of cis-diaminodichloroplatinum(II) (cisplatin) has been discovered [1]. Moreover, transition metal complexes containing planar polycyclic aromatic systems intercalate between the stacked base pairs of DNA. The biological activity of both cis- and trans-diamine Pt(II) complexes is dramatically enhanced by the presence of aromatic intercalator ligands, due to the influence on both kinetics and thermodynamics of DNA binding [2,3]. The chemistry of Pt(II) complexes is highly versatile, permitting the design and synthesis of a large variety of different structures. By ‘smart’ molecular engineering, new structures are programmed and obtained continuously, in an attempt to overcome the drawbacks of the cisplatinum like tumor resistance, or to lessening unpredictable and severe nephrotoxicity and/or providing oral bioavailability. Herein, new Pt(II) complexes as DNA intercalators were synthesized and characterized aiming to follow their structure – activity relationships. The synthesis and characterization of the complexes will be presented

New mononuclear cobalt (III) and manganese (III) complexes containing a hexadentate schiff base ligand

Manganese and cobalt complexes in high oxidation state play an important role in a diverse range of enzymatic and electron-transfer processes in biological systems1 and as antibacterial or antiviral agents2 . Here, we report the synthesis and crystal structures of two new mononuclear complexes [MnL](ClO4) (1) and [CoL](NO3)·2CH3OH (2) containing N,N’- bis[(2-hydroxybenzilideneamino)propyl]-piperazine (H2L) (Figure 1). X-ray structure determinations of 1 and 2 revealed that both compounds consist of mononuclear complex cations containing trivalent metal centers, MnIII or CoIII. The metal ions are coordinated in a distorted octahedral fashion by the N4 donor set of the ligand in basal and the two phenoxo oxygen atoms in apical positions. Spectral properties are consistent with the crystallographic results and the electrochemical properties of the complexes have been investigated by cyclic voltammetry. Furthermore, thermal studies were performed to deduce the stabilities of the ligand and complex

Original scientific paper The

influence of the nature and textural properties of different supports on the thermal behavior of Keggin type heteropolyacid

Thermogravimetry Applied for Investigation of Coke Formation in Ethanol Conversion over Heteropoly Tungstate Catalysts

Thermogravimetric analysis (TGA) was used to evaluate the thermal stability and the amount of coke deposition resulting from the deactivation of catalysts during ethanol dehydration reaction in a fixed bed continuous flow reactor. In this study, a series of catalysts containing 30% of Pd doped and pure 12-tungstophosphoric acid and its insoluble Cs2.5H0.5PW12O40 salt supported on SBA-15 were prepared. The catalytic efficiency of ethanol dehydration reaction was also evaluated. Two types of coke are identified from the TPO (Temperature programmed oxidation) profiles and assigned to the coke precursor and hard coke, respectively. The results indicate that cesium salts reduced the formation of hard coke. The amount of total coke formed was significantly reduced by supporting the catalysts on mesoporous SBA-15 molecular sieves

The influence of the nature and textural properties of different supports on the thermal behavior of Keggin type heteropolyacids

In order to obtain highly dispersed heteropolyacids (HPAs) species, H3PMo12VO40 and H3PVMo11O40 were supported on various supports: silica (Aerosil - Degussa and Romsil types) and TiO2. The structure and thermal decomposition of supported and unsupported HPAs were followed by different techniques (TGA-DTA, FTIR, XRD, low temperature nitrogen adsorption, scanning electron microscopy). All the supported HPAs were prepared by impregnation using the incipient wetness technique with a 1:1 mixture of water–ethanol. Samples were prepared with different concentrations to examine the effect of loading on the thermal behavior of the supported acid catalysts. The thermal stability was evaluated with reference to the bulk solid acids and mechanical mixtures. After deposition on silica types supports, an important decrease in thermal stability was observed on the Romsil types and a small decrease on the Aerosil type. The stability of the heteropolyacids supported on titania increased due to an anion-support interaction, as the thermal decomposition proceeded in two steps. The structure of the HPAs was not totally destroyed at 450 ºC as some IR bands were still preserved. A relatively uniform distribution of HPAs on the support surface was observed for all compositions of the active phase. No separate crystallites of solid phase HPAs were found in the SEM images