Synthesis and structural studies on (E)-3-(2,6-difluorophenyl)-1-(4-fluorophenyl)prop-2-en-1-one: a promising nonlinear optical material.

A new fluorinated chalcone (E)-3-(2,6-difluorophenyl)-1-(4-fluorophenyl)prop-2-en-1-one was synthesized in 90% yield and crystallized by a slow evaporation technique. Its full structural characterization and purity were determined by scanning electron microscopy, infrared spectroscopy, gas chromatography-mass spectrometry, 1H, 13C and 19F nuclear magnetic resonance, thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), Raman microspectroscopy, UV-Vis absorption spectroscopy, single crystal X-ray diffraction (XRD) and Hirshfeld surface (HS) analysis. The fluorinated chalcone crystallized in centrosymmetric space group P21/c stabilized by the C-H⋯O and C-H⋯F interactions and the π⋯π contact. The crystalline environment was simulated through the supermolecule approach where a bulk with 378 000 atoms was built. The electric parameters were calculated at the DFT/CAM-B3LYP/6-311++G(d,p) level as function of the electric field frequency. The macroscopic parameters such as linear refractive index and third-order nonlinear susceptibility (χ (3)) were calculated, and the results were compared with experimental data obtained from the literature. The χ (3)-value for the chalcone crystal is 369.294 × 10-22 m2 V-2, higher than those obtained from a few similar types of molecule, showing that the chalcone crystal can be considered as a nonlinear optical material. Also, molecular theoretical calculations such as infrared spectrum assignments, frontier molecular orbital analysis and MEP were implemented, revealing that the most positive region is around the hydrogen atoms of the aromatic rings, and electrophilic attack occurs on the carbonyl group.

A novel dihydrocoumarin under experimental and theoretical characterization.

Coumarins are natural and synthetic active ingredients widely applied in diverse types of medicinal treatments, such as cancer, inflammation, infection, and enzyme inhibition (monoamine oxidase B). Dihydrocoumarin compounds are of great interest in organic chemistry due to their structural versatilities and, as part of our investigations concerning the structural characterization of small molecules, this work focuses on crystal structure and spectroscopic characterization of the synthesized and crystallized compound 4-(4-methoxyphenyl)-3,4-dihydro-chromen-2-one (C16H14O3). Additionally, a theoretical calculation was performed using density functional theory to analyze the sites where nucleophilic or electrophilic attack took place and to examine the molecular electrostatic potential surface. Throughout all of these calculations, both density functional theory and Car-Parrinello molecular dynamics were performed by fully optimized geometry. The spectroscopic analysis indicated the presence of aromatic carbons and hydrogen atoms, and also the carbonyl and methoxy groups that were confirmed by the crystallographic structure. The C16H14O3 compound has a non-classical intermolecular interaction of type C-H⋅⋅⋅O that drives the molecular arrangement and the crystal packing. Moreover, the main absorbent groups were characterized throughout calculated harmonic vibrational frequencies. Also, natural bond orbital analysis successfully locates the molecular orbital with π-bonding symmetry and the molecular orbital with π* antibonding symmetry. Finally, the gap between highest occupied and lowest unoccupied molecular orbitals implies in a high kinetic stability and low chemical reactivity of title molecule.

Synthesis, characterization, and computational study of the supramolecular arrangement of a novel cinnamic acid derivative.

In this work, we present the synthesis, characterization, and computational study of the supramolecular arrangement of a new cinnamic acid derivative: ethyl-(2E)-3-(4-hydroxy-3,5-dimethoxyphenyl)-prop-2-enoate (EHD). Single crystals of EHD were obtained using ethyl ether as solvent and a slow evaporation technique. Its crystallographic structure, derived from X-ray diffraction experiments, includes a disordered water molecule on the EHD supramolecular structure. This water molecule participates in four O-H···O hydrogen bonds, which are arranged as a centrosymmetric H-bond array with the water at the center. Electronic and structural properties of the isolated EHD molecule and of the EHD molecule in the presence of one water molecule were calculated at the B3LYP/6-311++G(2d,2p) level of theory. These calculations show that the HOMO-LUMO energy gap of EHD decreases upon the introduction of the water molecule, suggesting that EHD becomes a stronger electron acceptor. These results indicate that the water molecule helps to stabilize the crystal structure in this system containing unequal numbers of acceptor and donor atoms. The supramolecular synthon involving the disordered water molecule and the supramolecular features presented here provide new possibilities in the design of functional materials and should also help us to gain a deeper understanding of the processes by which molecules recognize biological targets.

Theoretical investigation of the interaction of glycerol with aluminum and magnesium phthalocyanines.

Glycerol is a byproduct produced in great quantity by biodiesel industries in transesterification reactions. Finding new applications for glycerol is a current concern of many research groups around the world. This work focuses on a theoretical investigation, at the B3LYP/6-31G* level of theory, into the possibility of using aluminum phthalocyanine (AlPc) and magnesium phthalocyanine (MgPc) in the modelling of catalysts to convert glycerol into alcohol, which has wider industrial applicability. According to our calculations there are strong interactions between the O-terminus of glycerol and the central metal atom of AlPc and MgPc. By applying the Fukui function, HSAB theory and analysis of the frontier molecular orbital, it was possible to explain the way in which glycerol interacts with AlPc and MgPc. As a result of these interactions, there is a considerable change in both electronic and geometric parameters of glycerol, which can be used in designing new strategies to convert glycerol into alcohol.

A quantum chemical and chemometrical study of indolo[2,1-b]quinazoline and their analogues with cytotoxic activity against breast cancer cells.

Some indolo[2,1-b]quinalozine (tryptanthrin) analogues present cytotoxic activity against human breast cancer cells. In this work, chemometric methods were applied in the search for building discriminant models between active and inactive analogues, based on the correlations among their in vitro cytotoxic activities and their electronic and geometric molecular descriptors. From 88 descriptors calculated with density functional theory with the exchange correlation functional B3LYP and the basis set 6-31G* (Gaussian 03), 29 were pre-selected based on their Fisher weights, and finally five descriptors (partial charge on atom 15, bond orders between atoms 12-13, 17-25 and 18-26, and energy difference between frontier molecular orbitals) were selected for principal component analysis. This analysis was able to discriminate 12 inactive from 22 active analogues by using only one principal component, accounting for 49% of the total variance and allowing us to better understand the influence of these electronic descriptors in the cytotoxic activity. In addition, a supervised partial least-squares discriminant model was build and successfully used to discriminate tryptanthrin analogues. The model was validated through an independent test set and considered robust to overfitting.

Synthesis, structure, electronic and vibrational spectra of 9-(Diethylamino)-benzo(a)phenoxazin-7-ium-5-N-methacrylamide.

The electronic and vibrational spectra of 9-(Diethylamino)-benzo(a)phenoxazin-7-ium-5-N-methacrylamide (Nile Blue-5-N-methacrylamide) are measured, and the results are compared with the theoretical values obtained by quantum chemical calculations. The geometry, electronic transitions, charge distribution, and the IR normal modes of this new dye and of its precursor Nile Blue have been computed by using Density Functional Theory (DFT) method with the functional B3LYP and the 6-31G(d) Gaussian basis set. The molecular properties of the two dyes, predicted and observed, are very similar in the electronic ground state. In the excited state, however, the longer lifetime and larger fluorescence quantum yield of the Nile Blue-5-methacrylamide is ascribed to an inhibition of the twisted intramolecular charge transfer (TICT) process, when the NH2 is substituted by the methacrylamide in the 5-position of the aromatic extended ring of the dye. The change in charge density of the N atom in 5-position, as well as the difference in dipole moment and ionization potential of the two dyes molecules, explain the attenuation of TICT process. The vibration spectra of both dyes are simulated properly by using the DFT method.

[H-reflex in spastic patients due to spinal cord injury before and after the use of diazepam and baclofen]. / Pesquisa do reflexo "H" em pacientes espásticos por lesão medular antes e depois do uso de diazepam e baclofen.

This paper concerns the "H" reflex in eleven patients with spastic spinal cord injury (C5-T10), treated with Baclofen (50 mg/day) or Diazepam (20 mg/day). The "H" reflex was tested in the tibial nerve before and 15 days after the interrupted use of the drugs. Five patients used Baclofen and 6 patients used Diazepam. The latency time was measured. All the patients showed normal latency time before the use of the drugs. After the use all but one didn't show any significant alterations of the latency time. The patient, who showed a greater latency after use of drugs, presented an improvement of the motor function.