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981.
Fernández G Sánchez L Pérez EM Martín N 《Journal of the American Chemical Society》2008,130(32):10674-10683
The convergent synthesis of large monodisperse dendrimers, up to the fourth generation, decorated in their periphery with pi-extended tetrathiafulvalene units is reported, and their redox and supramolecular properties are investigated. A number of experiments (MALDI-TOF, (1)H NMR at variable temperature and different concentration, DLS, AFM and SEM imaging) confirm the self-aggregation process of these dendrimers, despite the butterfly-like shape of the exTTF units, highly distorted from planarity, to form large supramolecular architectures in the gas phase, in solution, and on a mica surface. Dendrimers 5, 9, and 12 host a number of C60 molecules to form segregated arrays of donor and acceptor units which could give rise to valuable materials useful for the preparation of optoelectronic devices. UV-vis titration experiments demonstrate that complexation of C60 occurs in a positive cooperative manner. Cyclic voltammetry experiments show that the peripheral exTTF units are involved in multioxidation processes. The self-diffusion coefficients (D) of the dendrimers reported herein and the previously reported exTTF (1) and tweezer (2) have been calculated from their chronoamperograms at different concentrations and by the Cottrell equation and, where possible, by PFG-NMR. The calculated values for D demonstrate the decrease of this magnitude with increasing dendrimer size. 相似文献
982.
Yan Guo Chen Liang Chengcheng C. Zhang Jesús Ferrando-Soria Yu Gao Jiahui H. Yang Xiangyu Y. Liu Emilio Pardo 《化学:亚洲杂志》2022,17(1):e202101220
Developing efficient adsorbent materials is crucial for adsorption and separation to realize the purification of energy source and raw chemicals. Here, we report a novel and robust 3D In-based MOF built up with fluorine-functionalized ligands, QMOF-2F , with improved separation properties of C2-light hydrocarbons over methane at room temperature respect isoreticular non-fluorinated MOF. QMOF-2F shows a remarkable chemical stability in different solvents, including water, and pH (2–12). DFT calculations support the key role of fluorine-functionalization on the improved performance of QMOF-2F . 相似文献
983.
Cosimo Toma Alberto Manganaro Giuseppa Raitano Marco Marzo Domenico Gadaleta Diego Baderna Alessandra Roncaglioni Nynke Kramer Emilio Benfenati 《Molecules (Basel, Switzerland)》2021,26(1)
Carcinogenicity is a crucial endpoint for the safety assessment of chemicals and products. During the last few decades, the development of quantitative structure–activity relationship ((Q)SAR) models has gained importance for regulatory use, in combination with in vitro testing or expert-based reasoning. Several classification models can now predict both human and rat carcinogenicity, but there are few models to quantitatively assess carcinogenicity in humans. To our knowledge, slope factor (SF), a parameter describing carcinogenicity potential used especially for human risk assessment of contaminated sites, has never been modeled for both inhalation and oral exposures. In this study, we developed classification and regression models for inhalation and oral SFs using data from the Risk Assessment Information System (RAIS) and different machine learning approaches. The models performed well in classification, with accuracies for the external set of 0.76 and 0.74 for oral and inhalation exposure, respectively, and r2 values of 0.57 and 0.65 in the regression models for oral and inhalation SFs in external validation. These models might therefore support regulators in (de)prioritizing substances for regulatory action and in weighing evidence in the context of chemical safety assessments. Moreover, these models are implemented on the VEGA platform and are now freely downloadable online. 相似文献
984.
Marlene A. Velazco-Medel Luis A. Camacho-Cruz Hctor Magaa Kenia Palomino Emilio Bucio 《Molecules (Basel, Switzerland)》2021,26(10)
The modification of medical devices is an area that has attracted a lot of attention in recent years; particularly, those developments which search to modify existing devices to render them antimicrobial. Most of these modifications involve at least two stages (modification of the base material with a polymer graft and immobilization of an antimicrobial agent) which are both time-consuming and complicate synthetic procedures; therefore, as an improvement, this project sought to produce antimicrobial silicone (PDMS) in a single step. Using gamma radiation as both an energy source for polymerization initiation and as a source of reducing agents in solution, PDMS was simultaneously grafted with acrylic acid and ethylene glycol dimethacrylate (AAc:EGDMA) while producing antimicrobial silver nanoparticles (AgNPs) onto the surface of the material. To obtain reproducible materials, experimental variables such as the effect of the dose, the intensity of radiation, and the concentration of the silver salt were evaluated, finding the optimal reaction conditions to obtain materials with valuable properties. The characterization of the material was performed using electronic microscopy and spectroscopic techniques such as 13C-CPMAS-SS-NMR and FTIR. Finally, these materials demonstrated good antimicrobial activity against S. aureus while retaining good cell viabilities (above 90%) for fibroblasts BALB/3T3. 相似文献
985.
Hermosilla L Sieiro C Calle P Zerbetto M Polimeno A 《The journal of physical chemistry. B》2008,112(36):11202-11208
The temperature dependence of the cw-EPR spectra corresponding to the propagating radical responsible for the polymerization of methacrylic monomers has been simulated by an integrated computational approach that determines the structural and magnetic parameters (via quantum mechanical calculations) and diffusive properties (via hydrodynamic based methods), which represent the overall input of the stochastic Liouville equation that yields the spectrum. The system has been modeled as a rotator with only one relaxation process, the rotation around the C alpha-C beta bond. The simulations clearly indicate that the change of the spectral shape with the temperature is essentially related to the internal flexibility of the radical end. 相似文献
986.
Potassium aryltrifluoroborates are cross-coupled with aryl and heteroaryl chlorides using a 4-hydroxyacetophenone oxime-derived palladacycle as precatalyst, K2CO3 as base, and TBAB as additive in refluxing water under conventional and microwave heating affording the corresponding biphenyls under phosphine-free conditions. For the arylation of allyl and benzyl chlorides, KOH is used as base in acetone-water (3:2) at rt or 50 degrees C using 0.1 mol % Pd loading providing allylbenzenes and diarylmethanes, respectively. 相似文献
987.
The chirality of sec/prim- and prim/sec-1,2-amino alcohols can be determined by (1)H NMR of just one MPA derivative--either (R) or (S)--by comparison of two spectra at different temperatures and analysis of the evolution of the easily observable singles of the CalphaH signals. 相似文献
988.
Felts AK Gallicchio E Chekmarev D Paris KA Friesner RA Levy RM 《Journal of chemical theory and computation》2008,4(5):855-868
The OPLS-AA all-atom force field and the Analytical Generalized Born plus Non-Polar (AGBNP) implicit solvent model, in conjunction with torsion angle conformational search protocols based on the Protein Local Optimization Program (PLOP), are shown to be effective in predicting the native conformations of 57 9-residue and 35 13-residue loops of a diverse series of proteins with low sequence identity. The novel nonpolar solvation free energy estimator implemented in AGBNP augmented by correction terms aimed at reducing the occurrence of ion pairing are important to achieve the best prediction accuracy. Extended versions of the previously developed PLOP-based conformational search schemes based on calculations in the crystal environment are reported that are suitable for application to loop homology modeling without the crystal environment. Our results suggest that in general the loop backbone conformation is not strongly influenced by crystal packing. The application of the temperature Replica Exchange Molecular Dynamics (T-REMD) sampling method for a few examples where PLOP sampling is insufficient are also reported. The results reported indicate that the OPLS-AA/AGBNP effective potential is suitable for high-resolution modeling of proteins in the final stages of homology modeling and/or protein crystallographic refinement. 相似文献
989.
Topoglidis E Lutz T Durrant JR Palomares E 《Bioelectrochemistry (Amsterdam, Netherlands)》2008,74(1):142-148
Hybrid protein films incorporating Cyt-c immobilized on TiO(2) films were prepared and characterised optically with UV-visible spectroscopy and electrochemically with cyclic voltammetry, and their conductivity properties were studied in detail. In addition the effects of a thin overlayer coating of a second metal oxide such as SiO(2), Al(2)O(3), ZrO(2) and MgO(2) were studied and the effects over the electrochemical properties of the hybrid working electrodes were discussed. 相似文献
990.
Juárez-Pérez EJ Viñas C González-Campo A Teixidor F Sillanpää R Kivekäs R Núñez R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(16):4924-4938
Mono- and dilithium salts of [3,3'-Co(1,2-C(2)B(9)H(11))(2)](-), (1(-)), react with different chlorosilanes (Me(2)SiHCl, Me(2)SiCl(2), Me(3)SiCl and MeSiHCl(2)) with an accurate control of the temperature to give a set of novel C(c)-mono- (C(c) = C(cluster)) and C(c)-disubstituted cobaltabis(dicarbollide) derivatives with silyl functions: [1-SiMe(2)H-3,3'-Co(1,2-C(2)B(9)H(10))(1',2'-C(2)B(9)H(11))](-) (3(-)); [1,1'-mu-SiMe(2)-3,3'-Co(1,2-C(2)B(9)H(10))(2)](-) (4(-)); [1,1'-mu-SiMeH-3,3'-Co(1,2-C(2)B(9)H(10))(2)](-) (5(-)); [1-SiMe(3)-3,3'-Co(1,2-C(2)B(9)H(10))(1',2'-C(2)B(9)H(11))](-) (6(-)) and [1,1'-(SiMe(3))(2)-3,3'-Co(1,2-C(2)B(9)H(10))(2)](-) (7(-)). In a similar way, the [8,8'-mu-(1',2'-C(6)H(4))-1,1'-mu-SiMe(2)-3,3'-Co(1,2-C(2)B(9)H(9))(2)](-) (8(-)); [8,8'-mu-(1',2'-C(6)H(4))-1,1'-mu-SiMeH-3,3'-Co(1,2-C(2)B(9)H(9))(2)](-) (9(-)) and [8,8'-mu-(1',2'-C(6)H(4))-1-SiMe(3)-3,3'-Co(1,2-C(2)B(9)H(9))(1',2'-C(2)B(9)H(10))](-) (10(-)) ions have been prepared from [8,8'-mu-(1',2'-C(6)H(4))-3,3'-Co(1,2-C(2)B(9)H(10))(2)](-) (2(-)). Thus, depending on the chlorosilane, the temperature and the stoichiometry of nBuLi used, it has been possible to control the number of substituents on the C(c) atoms and the nature of the attached silyl function. All compounds were characterised by NMR and UV/Vis spectroscopy and MALDI-TOF mass spectrometry; [NMe(4)]-3, [NMe(4)]-4 and [NMe(4)]-7 were successfully isolated in crystalline forms suitable for X-ray diffraction analyses. The 4(-) and 8(-) ions, which contain one bridging -mu-SiMe(2) group between each of the dicarbollide clusters, were unexpectedly obtained from the reaction of the monolithium salts of 1(-) and 2(-), respectively, with Me(2)SiHCl at -78 degrees C in 1,2-dimethoxyethane. This suggests that an intramolecular reaction has taken place, in which the acidic C(c)-H proton reacts with the hydridic Si-H, with subsequent loss of H(2). Some aspects of this reaction have been studied by using DFT calculations and have been compared with experimental results. In addition, DFT theoretical studies at the B3 LYP/6-311G(d,p) level of theory were applied to optimise the geometries of ions 1(-)-10(-) and calculate their relative energies. Results indicate that the racemic mixtures, rac form, are more stable than the meso isomers. A good concordance between theoretical studies and experimental results has been achieved. 相似文献