Determination of degree of conversion as a function of depth of a photo-initiated dental restoration composite—III application to commercial Prodigy Condensable™

In this third work, we evaluated the degree of conversion (DC) versus depth of dental filling composite named Prodigy Condensable™ using infrared spectroscopy. Confirming previous results, there was a gradual reduction of DC with increasing depth but the composite exhibited extreme values of DC, an upper value (45.9%) on the surface and a lower one (6.1%) at a depth of 5 mm. The composite presented the worst performance among materials studied. The composite formulation was 80% of inorganic fillers and BisfenolA/dimethacrylate (BisGMA) (18%)/triethyleneglycoldimethacrylate (TEGDMA) (2.0%) as monomers. As stated before, type/ratio/viscosity of monomers and type, amount, size and size distribution of fillers all together had an important role in the cure reaction contributing to the final performance of the composite.     

Enthalpic determinations of aliphatic ester-solvent systems with correlations

Calorimetric measurements were carried out on ester-solvent systems where the esters were H(CH₂)_xCOO(CH₂)_yH, with x and y varying from 1 to 5, and the solvents were n-hexane and 1,2-dichloroethane. Calculation of the enthalpies of cavity formation enabled the enthalpies of interaction to be determined. Both enthalpies correlated with number of carbon atoms N, equal to x+y in the esters, giving for 1,2-dichloroethane

Indium(I) bromide-mediated coupling of dibromoacetonitrile with aldehydes followed by Boord elimination of bromine and oxygen of β-bromo alkoxides for preparation of 3-organyl-2-alkenenitriles

The organoindium compound derived from indium monobromide and dibromoacetonitrile reacts with carbonyl compounds to afford the corresponding 2-bromo-2-cyano-indium(III) alkoxide. The action of a second equivalent of indium monobromide onto the alkoxides derived from aldehydes promotes the Boord elimination of the β-related oxygen and bromine atoms leading to 2-alkenenitriles.     

A Thermodynamic Study of Interactions of Monoionic Kaolinite with N,N-Dimethylacetamide (DMA) and Pyridine (PY)

Two series of monoionic (M) kaolinites (M = H(+), Ca(2+), Cu(2+), Zn(2+), Al(3+), and Fe(3+)) were prepared from a natural Brazilian clay (S?o Sim?o clay, SP): series A, dried under vacuum at 25 degrees C, and series B, dried under vacuum at 25 degrees C. The natural clay was characterized by elemental analysis, cation exchange capacity, X-ray diffractometry, differential thermal analysis, and surface area measurements (BET). The interactions of M,M-dimethylacetamide and pyridine with these (M) kaolinites were studied by adsorption isotherms, titration calorimetry, and infrared spectroscopy (for pyridine only). The results indicated a coordinative interaction between M,M-dimethylacetamide and (M) kaolinites. For the interactions between pyridine and (M) kaolinites, the formation of hydrogen bonds (M = Al(3+), Fe(3+)), hydrogen and coordinative bonds (M = Cu(2+), Zn(2+)), and ionic pairs (M = H(+), Ca(2+)) was observed. For the pyridine-(Cu) kaolinite system, a substitution of water coordinated to Cu(2+) by pyridine was established.     

Cd(II) determination in the presence of aqueous micellar solutions

The equilibrium constants and molar absorptivities for the fast formation of a 1:3 complex between cadmium(II) (Cd(II)) and dithizonate anion, in the presence of cationic and non-ionic surfactants, allowed a simple and fast spectrophotometric determination of total cadmium. Indeed, the molar absorptivities of the Cd(II)-dithizone (Dz) complex formed in the presence of the neutral Triton X-100 and cationic cetyltrimethylammonium bromide (CTAB) surfactants are almost twice the value observed in the standard method and the maxima of absorption are shifted by about 40 nm when compared with the standard method. Clearly, the use of neutral and cationic surfactants promotes a higher value of the molar absorptivities of the complex, resulting in an increase in the sensitivity of the method. Application of the method to the desorption of Cd(II) ions from clays is illustrated.     

Copper(II) complexes with pyridoxal dithiocarbazate and thiosemicarbazone ligands: crystal structure,spectroscopic analysis and cytotoxic activity

Transition Metal Chemistry - The present study reports the synthesis and crystal structures of Cu(II) complexes with pyridoxal S-allyldithiocarbazate (H2L1) and pyridoxal thiosemicarbazones...     

Two Cu(I) complexes based on semicarbazone ligand: synthesis,crystal structure,Hirshfeld surface and anticancer activity evaluation against human cell lines

Structural Chemistry - Two novel Cu(I) complexes with the 2-acetylpyridine-N(4)-phenyl semicarbazone (HL) ligand, [CuCl (HL)(PPh3)]∙CH3CN (1) and [CuBr (HL)(PPh3)] (2), were investigated by...     

Supramolecular architectures and crystal structures of gold(III) compounds with semicarbazones

The synthesis and crystal structures of two novel semicarbazones and four gold(III) compound derivatives of these semicarbazones are presented. A pattern in the formation of the semicarbazones shows the association of Cl^– ions held together by intra- and intermolecular forces. [AuCl₄]^? and [AuBr₄]^? anions are co-crystallised with these semicarbazone ligands, and the packing architectures revealed by a single-crystal X-ray diffraction analysis showed the different influences of the anions and the association of these chemical species by intermolecular forces on the crystal packing. Crystal engineering led to gold(III) compounds that are stabilised by relevant hydrogen bonding networks, which demonstrated their importance to the supramolecular organisation of the studied compounds. Interestingly, Cl???Br interactions are observed and contribute to the formation of the supramolecular structures. Elemental analysis data and spectroscopic properties in the solid state and solution are also described.     

Magnetic properties of ferromagnetic quasi-1D copper-peptide compounds: exchange interactions and very low temperature phase transitions

The magnetic properties of the Cu(II)-peptide compounds (L-tyrosyl-L-leucinato)Cu(II) and (L-tryptophyl-glycinato)Cu(II), to be identified as Cu(II)Tyr-Leu and Cu(II)Trp-Gly, respectively, have been investigated by specific heat (0.08 < T < 28 K), dc magnetization (2 < T < 80 K, with B(0) = mu(o)H < or = 9 T), and ac magnetic susceptibility (with B(0) = 0 for 0.03 < T < 3 K and B(0) up to 9 T for 2 < T < 80 K) measurements. Above approximately 1 K, the specific heat and magnetization of both compounds display a ferromagnetic (FM) spin chain behavior sustained by syn-anti carboxylate bridges connecting equatorially Cu(II) ions at about 5 A. To model this behavior, we calculated the eigenvalues of Heisenberg chains with up to 20 spins 1/2 and used the method of Bonner and Fisher. A global fit of the model to the specific heat and magnetization data gives 2J(0)/k(B) = 3.60(5) K and 2.59(5) K for the intrachain exchange interactions in Cu(II)Tyr-Leu and Cu(II)Trp-Gly, respectively (H(ex)(i,j) = -2J(0) S(i).S(j)). These values of 2J(0) are discussed in terms of structural properties of the carboxylate bridges in the two compounds. Using the parameters obtained from the global fit, we calculated isothermal susceptibilities in agreement with the ac susceptibilities measured with small applied dc magnetic fields. However, the ac susceptibility measured with applied dc fields larger than 1 T lie between the values calculated for the isothermal and adiabatic susceptibilities. At 0.16 K for Cu(II)Tyr-Leu and 0.53 K for Cu(II)Trp-Gly, the observed specific heat and magnetic susceptibility display peaks associated to three-dimensional magnetic phase transitions. The interchain exchange couplings 2J(1) producing the 3D magnetic order are ferromagnetic and have magnitudes 2J(1)/k(B) approximately 0.015 and 0.073 K for Cu(II)Tyr-Leu and Cu(II)Trp-Gly, respectively.