Decomposição térmica de complexos de Zn e Cd com isomaleonitriladitiolato (imnt)

Thermal decomposition of [Bu4N]2[Zn(imnt)2] and [M(NH3)2(imnt)] complexes with M = Zn and Cd, and imnt = (bis 1,1-dicyanoethylene-2,2 dithiolate) in inert atmosphere was investigated by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). Pyrolysis studies at different temperatures, 300, 400, 500, and 600 ºC, in N2 atmosphere were performed and the products were characterized by X-ray diffraction (XRD), infrared and Raman spectroscopy, and scanning electron microscopy (SEM). The products were identified as sulfide sub-micron particles, along with amorphous carbon. Particle sizes estimated by SEM were ca. 50 nm for the cationic complexes and 500 nm for the neutral complexes.

Estudo espectroscópico de complexos de Eu3+, Tb3+ E Gd3+ com ligantes derivados de ácidos dicarboxílicos

Complexes of Eu3+, Tb3+ and Gd3+ with dipicolinic acid, chelidamic acid and chelidonic acid have been synthesized in order to study the effect of the substituent groups on the luminescence of the lanthanide complexes. The luminescence of the Eu3+ and Tb3+ complexes was quantified by quantum yield measurements. The complexes of Gd3+ have been used to determine the energies of the triplet states of the ligands. The Tb3+ complex synthesized with dipicolinic acid presented the highest quantum yield due to the energy difference between the triplet state of the dipicolinic acid and the emitting level of the Tb3+ ion.

Síntese e caracterização de novos complexos de platina (II) com ligantes derivados do furano e nitrofurano

Platinum (II) complexes, for example, cisplatin and carboplatin, have been used as chemotherapeutic agents for the treatment of various types of cancer. Several other complexes of this metallic ion are also under clinical evaluation. This work describes the synthesis of five new platinum (II) complexes having furan and 5-nitrofuran derivatives and chloride as ligands. The compounds were characterized by NMR, IR and elemental analysis.

Complexos metálicos com o herbicida glifosato: revisão

We present studies involving metallic ions and the herbicide glyphosate. The metallic complexes of Cu(II), Zn(II), Mn(II), Ni(II), Cd(II), Pb(II), Cr(III), Fe(III), Co(III), ammonium, sodium, Ag(I), alkaline earth metals and of some lanthanides ions are described. The complexes are discussed in terms of their synthesis, identification, stability and structural properties, based on data from the current literature.

Simulação de desdobramentos complexos de espectros de RMN de ¹H

Complex ¹H NMR spectra multiplets that cannot be easily understood by simple inspection are rather frequent in the daily work of the organic chemistry analyst. The multiple and excellent new techniques available from modern instruments usually provide satisfactory solutions, but there are still many cases where a simulation is necessary, at least to obtain a final confirmation. It is extremely convincing to see that a graph, obtained by calculations with chemical-shift and coupling-constant values only, can be virtually identical to the experimental spectrum. This paper describes a computer program to make such calculations. The program is free and can be downloaded from http://artemis.ffclrp.usp.br/NMR.htm (click on SimEsp_NMR_Compil.zip). All routines are also available and may be used without any restrictions. The paper includes a fairly detailed discussion about how the calculations are made.

Construção de campo de força empírico para estudo de complexos de Fe(III) com interesse bioinorgânico

In this work we present a new parametrization in molecular mechanics for studying iron complexes. This force field was implemented in the FORCES 2000 program, developed in our group for studying in coordination compounds of interest in bioinorganic chemistry. Mononuclear and dinuclear iron complexes were studied using this program with good success.

Síntese e reatividade de complexos platina-trifenilestibina: uma revisão bibliográfica

This article deals with synthesis and reactivity of complexes with triphenylstibine (SbPh3) as the ligand. A comparative study of analogous complexes of triphenylphosphine (PPh3) and triphenylarsine (AsPh3) with platinum in the oxidation states zero, two and four is included. The bibliographic revision includes publications since 1936, when the first Pt(II) complex with triphenylstibine was described.

Síntese e caracterização de um novo complexo de platina (IV) a partir de seu análogo de platina (II) utilizando iodo molecular como agente oxidante: uma rota sintética interessante para obtenção de novos complexos de platina

In an attempt to reduce toxicity and widen the spectrum of activity of cisplatin and its analogues, much attention has been focused on designing new platinum complexes. This work reports the synthesis and characterization of novel compounds of the platinum (II) and platinum (IV) containing 2-furoic hydrazide acid and iodide as ligands. Although the prepared compounds do not present the classical structure of biologically active platinum analogues, they could be potentially active or useful as precursors to prepare antitumor platinum complexes. The reported compounds were characterized by ¹H NMR, 13C NMR, 195Pt NMR, IR and elemental analyses.

Anéis aromáticos condensados e relação E4/E6: estudo de ácidos húmicos de gleissolos por RMN de 13C no estado sólido utilizando a técnica CP/MAS desacoplamento defasado

In this work, seven samples of humic acids extracted from gleysoils were investigated. These studies, using NMR CP/MAS 13C techniques, did not show significant correlation between the E4/E6 ratio and the degree of aromaticity. However, dipolar dephasing (DD) measurements of condensed aromatic or substituted carbons showed a negative correlation of 0.94. Also, there was a good correlation between the amount of semiquinone free radicals measured by the EPR technique and condensed aromatic rings measured by NMR CP/MAS 13C with the DD technique. The content of semiquinone free radicals was quantified by EPR spectroscopy and was correlated with the humification (degree of aromaticity) of the humic substances. The results indicated that the E4/E6 ratio identifies the degree of aromatic rings condensation. It was also found that the degree of aromaticity, measured by NMR, as frequently presented in the literature (by conventional CP/MAS), underestimates aromatic rings in condensed structures.

Preparação e caracterização físico-química de complexos de inclusão entre anestésicos locais e hidroxipropil-beta-ciclodextrina

S(-) Bupivacaine (S(-)BVC) and Lidocaine (LDC) are widely used local anesthetics (LA). Hydroxypropyl beta-cyclodextrin (HP-beta-CD) is used as a drug-carrier system. The aim of this work was to characterize inclusion complexes between LA and HP-beta-CD. The affinity constants determined at different pHs show favourable complexation. The release kinetics experiments showed that S(-)BVC and LDC changed the released profiles in the presence of HP-beta-CD. Nuclear magnetic resonance experiments gave information about the interaction between LA and the cyclodextrin cavity. This study focused on the physicochemical characterization of drug-delivery formulations that come out as potentially new therapeutic options for pain treatment.

Relação entre transferência de carga e as interações intermoleculares em complexos de hidrogênio heterocíclicos

Hydrogen-bonded complexes formed by the interaction of the heterocyclic molecules C2H4O and C2H5N with HF, HCN, HNC and C2H2 have been studied using density functional theory. The hydrogen bond strength has been analyzed through electron density charge transfer from the proton acceptor to the proton donor. The density charge transfer has been estimated using different methods such as Mulliken population analysis, CHELPG, GAPT and AIM. It has been shown that AIM-estimated charge transfer correlates very well with the hydrogen bond energy and the infrared bathochromic effect of the proton donor stretching frequencies.

Biomateriais: deposição de hidroxiapatita sobre superfície de Ti-cp modificada por aspersão térmica

The osseointegrated titanium implants are reliable and safe alternatives to treatments for long periods of time. For surface modification, thermal aspersion of TiO2 was used. The samples with and without TiO2 were treated with NaOH and SBF in order to obtain a layer of HA. Characterization was done by SEM and FTIR. The images of HA obtained by SEM show a uniform morphology and a porous structure with spherical particles. The IR spectra show that the surface of Ticp/ TiO2 is more favorable for the HA deposit, as can be seen by the increase of the crystalline structure and the very intense and defined bands of the OH group of HA that is verified about 3571 and 630 cm-1. Thus the Ticp/ TiO2 surface presents a satisfactory nucleation of HA when compared to Ticp.

Sobre uma degenerescência acidental nos deslocamentos químicos de RMN de 31P{¹H} em complexos difosfínicos de rutênio

The [RuCl(bipy)(dppb)(4-pic)]PF6 complex was prepared and fully characterized. The X-ray crystal structure of this complex was determined in order to make an unambiguous distinction between the two possible positions of the 4-methylpyridine ligand (4-pic) in the compound: trans to phosphorus atom or trans to nitrogen atom. The [RuCl(bipy)(dppb)(4-pic)]PF6 complex exhibits an unusual temperature-dependent accidental degeneracy of the 31P chemical shifts in its solution NMR spectrum.

A química supramolecular de complexos pirazólicos

The purpose of this review is to describe the progress in the supramolecular chemistry of the pyrazolyl-based metal complexes. The text is written under the structural point of view, emphasizing the role of the covalent and non-covalent interactions in the rational construction of super and supramolecules.

Um estudo teórico de propriedades moleculares em complexos de hidrogênio trimoleculares C2H4···2HF, C2H2···2HF e C3h6···2HF

We present a theoretical study of molecular properties in C2H4···2HF, C2H2···2HF and C3H6···2HF trimolecular hydrogen-bonded complexes. From B3LYP/6-311++G(d,p) calculations, the most important structural deformations are related to the C=C (C2H4), C≡C (C2H2), C-C (C3H6) and HF bond lengths. According to the Bader's atoms in molecules and CHELPG calculations, it was identified a tertiary interaction between the fluorine atom of the second hydrofluoric acid molecule and hydrogen atoms of the ethylene and acetylene within the C2H4···2HF and C2H2···2HF complexes, respectively. Additionally, the evaluation of the infrared spectrum characterized the new vibrational modes and bathochromic effect of the HF molecules.