Preparation and properties of peroxy titanium malonate

The method of preparation and physicochemical properties of peroxy titanium malonate, TiO2(OOC)2CH2·3H2O are given. The reasons for the poor complexing tendency of malonic acid are discussed. The nature of the bonds between titanium and the peroxy as well as malonate groups is assigned from spectrophotometric and infra-red absorption studies.

Preparation and properties of peroxy titanium malonate

The method of preparation and physicochemical properties of peroxy titanium malonate, TiO2(OOC)2CH2·3H2O are given. The reasons for the poor complexing tendency of malonic acid are discussed. The nature of the bonds between titanium and the peroxy as well as malonate groups is assigned from spectrophotometric and infra-red absorption studies.

Studies in nonlinear optical materials: structure of di-2-menthyl 2-(N,N'-dimethyl-2-imidazolidinylidene)malonate monohydrate

C28H48N2Oa.H2 O, Mr=494.7, orthorhombic,P2~2~2~, a = 7.634 (2), b = 11.370 (2), c=34. 167 (4) A, V = 2966 (2) A 3, Z = 4, D m = 1.095,D x -- 1. 108 g cm -3, Mo Kct, 2 -- 0.7107 ,/k, ~ =0.43 cm -~, F(000) = 1088.0, T= 293 K, R = 0.061 for 1578 significant reflections. The second-harmonicgeneration (SHG) efficiency of this compound is negligible (1/100th of the urea standard). The observed low second-order nonlinear response has been attributed to the unfavourable packing of the molecules in the crystal lattice.

Molecular interactions in bis(2-aminopyridinium) malonate: A crystal isostructural to bis(2-aminopyridinium) maleate crystal

Crystals of a new salt in 2:1 ratio of 2-aminopyridine and malonic acid are grown by slow evaporation. These crystals of bis(2-aminopyridinium) malonate are orthorhombic and belong to the non-centrosymmetric space group, Fdd2 with parameters a = 22.0786(6), b = 23.0218(6), c = 5.5595(1)angstrom and Z=8 at 300 K. The crystals are isostructural to those of bis(2-aminopyridinium) maleate, which is a NLO material. The isostructurality index between bis(2-aminopyridinium) maleate and bis(2-aminopyridinium) malonate was also calculated. The hyperpolarizability calculated using semi empirical method MOPAC2009 showed that bis(2-aminopyridinium) malonate has slightly higher beta value compared to that of bis(2-aminopyridinium) maleate. (C) 2011 Elsevier B.V. All rights reserved.

Syntheses of two new 1D and 3D networks of Cu(II) and Co(II) using malonate and urotropine as bridging ligands: Crystal structures and magnetic studies

Two new metal-organic based polymeric complexes, [Cu-4(O2CCH2CO2)(4)(L)].7H(2)O (1) and [CO2(O2CCH2CO2)(2)(L)].2H(2)O (2) [L = hexamethylenetetramine (urotropine)], have been synthesized and characterized by X-ray crystal structure determination and magnetic studies. Complex 1 is a 1D coordination polymer comprising a carboxylato, bridged Cu-4 moiety linked by a tetradentate bridging urotropine. Complex 2 is a 3D coordination polymer made of pseudo-two-dimensional layers of Co(II) ions linked by malonate anions in syn-anticonformation which are bridged by bidentate urotropine in trans fashion, Complex 1 crystallizes in the orthothombic system, space group Pmmn, with a = 14,80(2) Angstrom, b = 14.54(2) Angstrom, c = 7.325(10) Angstrom, beta = 90degrees, and Z = 4. Complex 2 crystallizes in the orthorhombic system, space group Imm2, a = 7.584(11) Angstrom, b = 15.80(2) Angstrom, c = 6.939(13) Angstrom, beta = 90.10degrees(1), and Z = 4. Variable temperature (300-2 K) magnetic behavior reveals the existence of ferro- and antiferromagnetic interactions in 1 and only antiferromagnetic interactions in 2. The best fitted parameters for complex 1 are J = 13.5 cm(-1), J = -18.1 cm(-1), and g = 2.14 considering only intra-Cu-4 interactions through carboxylate and urotropine pathways. In case of complex 2, the fit of the magnetic data considering intralayer interaction through carboxylate pathway as well as interlayer interaction via urotropine pathway gave no satisfactory result at this moment using any model known due to considerable orbital contribution of Co(II) ions to the magnetic moment and its complicated structure. Assuming isolated Co(II) ions (without any coupling, J = 0) the shape of the chi(M)T curve fits well with experimental data except at very low temperatures.

Thermal behaviour of malonic acid, sodium malonate and its compounds with some bivalent transition metal ions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Supramolecular assemblies and magnetic behaviors of the M(II)/p-aminopyridine/malonate (M = Ni, Mn, Cu, Co) systems

The coordination compounds [Ni(μ-mal)(apy)2(H 2O)]·2.8H2O (1), [Mn(μ-mal)(H2O) 2] (2), (apyH)2[Cu(μ-mal)2] (3) and (apyH)2[Co(mal)2(H2O)2] (4) (mal = malonate, apy = p-aminopyridine) have been synthesized and characterized by elemental analysis, vibrational spectroscopy, single crystal X-ray diffraction and magnetometry. With exception of 4, the malonate group acts as bridging ligand leading to the formation of one-dimensional polymeric chains. In compound 1 it was observed the coordination of the p-aminopyridine in the axial positions of the distorted octahedral coordination sphere. The solid-state structure exhibits a high complex 3D network formed by several supramolecular interactions. Magnetic properties were determined for all members of the series and indicate that the materials behave are normal paramagnets, except the Mn polymer 2 which exhibits an antiferromagnetic ground state. © 2013 Elsevier Ltd. All rights reserved.

Chemoselective condensationof beta-naphthol, dimethyl malonate, andaromatic aldehydes promoted by niobium pentachloride

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chemoselective condensation of β-naphthol, dimethyl malonate, and aromatic aldehydes promoted by niobium pentachloride

A multicomponent reaction of β-naphthol, dimethyl malonate, and aromatic aldehydes in the presence of NbCl5 as promoter is described. Under similar conditions, aromatic aldehydes with different substituents exhibited different behaviors than β-naphthol and dimethyl malonate. In these MCRs, 4-aryl-3,4-dihydrobenzo[f]coumarins are obtained as the major products (41–93%) and 14-aryl-14H-dibenzo[a,j]xanthenes as the minor products (1–38%).

High-pressure Raman spectroscopic and other structural studies of hydrotalcites containing intercalated dicarboxylic acid anions

The results of pressure-tuning Raman spectroscopic, X-ray powder diffraction and solid-state 13C-NMR studies of selected dicarboxylate anions intercalated in a Mg-Al layered double hydroxide (talcite) lattice are reported. The pressure dependences of the vibrational modes are linear for pressures up to 4.6 GPa indicating that no phase transitions occur. The interlayer spacings show that the oxalate, malonate and succinate dianions are oriented perpendicular to the layers, but the glutarate and adipate are tilted. The solid-state 13C-NMR spectra of these materials show full chemical shift anisotropy and, therefore, the anions are not mobile at room temperature.

Titanium Complexes for the Polymerisation of Ethene and Caprolactone

The literature part of the thesis mainly reviews the results of the use of titanium catalysts for ethene and caprolactone polymerisation. The behaviour of titanium catalysts bearing phenoxy-imino ligands has been the focus of more detailed investigations in ethene polymerisation. Reasons for the production of multimodal polyethene for a range of catalysts are also given. The experimental part of the thesis is divided into two sections based on the monomers used in the polymerisations: Part A (ethene) and part B (caprolactone). Part A: Titanium(IV) complexes bearing phenoxy-imino ligands are known to possess high ethene polymerisation activities after MAO activation. Depending on the ligand, the activities of the catalysts in polymerisation can vary between 1 and 44000 kgPE/(mol*cat*h*bar). Depending on the polymerisation temperature and the electronic and steric properties of the catalyst ligands, low to high molar mass values and uni- and multimodal polydispersity values can been observed. In order to discover the reasons for these differences, 22 titanium(IV) complexes containing differently substituted phenoxy-imino derivatives as di- and tetradentate ligands were synthesised with high yields and used as homogeneous catalysts in ethene polymerisations. Computational methods were used to predict the geometry of the synthesised complexes and their configuration after activation. Based on the results obtained, the geometry of the catalyst together with the ligand substituents seem to play a major role in defining the catalytic activity. Novel titanium(IV) complexes bearing malonate ligands were also synthesised. Malonates are considered to be suitable ligand pre-cursors since they can be produced by the simple reaction of any primary or secondary alcohol with malonylchloride, and thus they are easily modifiable. After treatment with MAO these complexes had polymerisation activities between 10 and 50 kgPE/(mol*cat*h*bar) and surprisingly low polydispersity values when compared with similar types of catalysts bearing the O?O chelate ligand. Part B: One of the synthesis routes in the preparation of the above mentioned phenoxy-imino titanium dichloride complexes involved the use of Ti(NMe2)4 with a range of salicylaldimine type compounds. On reaction, these two compounds formed an intermediate product selectively and quantitatively which was active in the ring-opening polymerisation of caprolactone. Several mono-anionic alcoholates were also combined with Ti(NMe2)4 in different molar ratios and used as catalysts. Full conversion of the monomer was achieved within 15 minutes with catalysts having a co-ordination number of 4 while after 22 hours full conversion was achieved with catalysts having a co-ordination number of 6.

Nature of the activation of succinate dehydrogenase byvarious effectors and in hypobaria and hypoxia

Hepatic mitochondrial succinate dehydrogenase (succinate:(acceptor)oxidoreductase, EC 1.3.99.1) was activated by preincubation of mitochondria with four diverse classes of compounds, the dicarboxylic acids, nitrophenols, quinols (and ubiquinols) and pyrophosphates. Of the various compounds tested malonate, oxaloacetate and pyrophosphate, well-known competitive inhibitors of the enzyme, and also hydroquinone and ubiquinols were effective even at low concentrations and showed maximal stimulation in 2 min.

Oxidation of succinate in heart, brain, and kidney mitochondria in hypobaria and hypoxia

Exposure of rats to hypobaric stress for periods of up to 36 h caused a consistent change in the succinate-NT reductase activity of the heart mitochondria whereas there was no significant change in the activities of either succinate dehydrogenase and succinate-NT reductase of the brain and the kidney. Mitochondrial succinate dehydrogenase of the heart, the brain and the kidney was activated 2- to 7-fold with the substrate and malonate. The activations obtained with oxalate, citrate and dinitrophenol were relatively lower in comparison to succinate and malonate. Benzohydroquinone and 2-nitrophenol had no stimulatory effect on the heart, the brain and the kidney mitochondria. THE ACTIVATIONS OBTAINED WITH THE VARIOUS EFFECTORS PARTIALLY (OR COMPLETELY IN THE CASE OF SUCCINATE) REVERSED ON WASHING THE MITOCHONDRIAL SAMPLES WITH THE SUCROSE HOMOGENIZING MEDIUM. The effect of ubiquinol, which also activated the enzyme, was only partially reversed after the second preincubation with succinate in the brain and the kidney whereas in the heart the activity was fully reversed. The increased activity of succinate dehydrogenase obtained with ATP and ADP was further enhanced by Mg2+ exclusively in the brain mitochondria, suggesting the possibility of Mg2+-AIP complex as the active species. Succinate-NT reductase of the heart, the brain and the kidney mitochondria showed a high activation with ubiquinone whereas its reduced form had no stimulatory effect.

Structural and kinetic studies on the activators of succinate dehydrogenase

1. 1. Diverse classes of compounds such as dicarboxylates, pyrophosphates, quinols and nitrophenols are known to activate mitochondrial succinate dehydrogenase (EC 1.3.99.1). Examples in each class — malonate, pyrophosphate, ubiquinol and 2,4-dinitrophenol — are selected for comparative studies on the kinetic constants and structural relationship. 2. 2. The activated forms of the enzyme obtained on preincubating mitochondria with the effectors exhibited Michaelian kinetics and gave doublereciprocal plots which are nearly parallel to that of the basal form. On activation, Km for the substrate also increased along with V. The effectors activated the enzyme at low concentrations and inhibited, in a competitive fashion, at high concentrations. The binding constant for activation was lower than that for inhibition for each effector. 3. 3. These compounds possess ionizable twin oxygens separated by a distance of Image and having fractional charges in the range of −0.26 to −0.74 e. The common twin-oxygen feature of the substrate and the effectors suggested the presence of corresponding counter charges in the binding domain. The competitive nature of effectors with the substrate for inhibition further indicated the close structural resemblance of the activation and catalytic sites.