Search results for "solvation"
showing 10 items of 157 documents
Solvent-Adaptive Behavior of Oligospirobifluorenes at the Surface of Quartz Crystal Microbalances-A Conformational Process
2017
Oligospirobifluorenes represent promising building blocks for the generation of microporous sensor materials based on their restricted flexibility. The contact with specific solvents leads to a change of the three-dimensional spirobifluorene structure. The single fluorene moieties unfold to an open structure with an increased volume due to intermolecular interactions with the solvent, detectable by NMR spectroscopy. The induced microporosity was further investigated by affinity comparisons of aromatic analytes with high fundamental frequency quartz crystal microbalances.
Comparative evaluation of the swelling and degrees of cross-linking in three organic gel packings for SEC through some geometric parameters.
2003
Abstract The size exclusion chromatographic (SEC) behavior of five solvent/polymer systems in three organic column packings based on polystyrene/divinylbenzene (PS/DVB) copolymer, TSK-Gel H HR , μ-styragel and TSK-Gel H XL , has been compared. All the packings offer similar characteristics (pore size, particle size and efficiency) but some differences have been found when eluting the same systems. The different elution behavior observed in both polymeric gels has been analyzed in terms of their swelling and cross-linking degrees and of the fractal parameters. From the Universal Calibration plots, values of the chromatographic partition coefficient, K p , have been obtained and using some eq…
Structure of anisole derivatives by total neutron and X-ray scattering: Evidences of weak C–H⋯O and C–H⋯π interactions in the liquid state
2020
Abstract High resolution, total neutron and X-ray scattering data have been used in synergy with Molecular Dynamics simulations to access atomistic scale insight into the structure of anisole and 2,3,5-trimethylanisole, two aromatic compounds bearing an electron-donating methoxy group. A detailed description is provided for the main interactions occurring in these systems, including π-π stacking and weak hydrogen bonding correlations: C H⋯O and C H⋯π. The existence of preferential orientations of the first shell coordinating molecules and the specific nature of the interactions involving the π cloud and the polar methoxy group have been reported and discussed.
Solvation parameters of solutes: an attempt of improvements in characterization and determination
2008
We are presenting here an updated version of our predictive model of solvation parameters of solutes, based on a simplified molecular topology (J. Chem. Inf. Model, 2006, 46, 1723-1734). The learning experimental database of this model is presently larger than in our first version and includes more compounds with more than one functional group of the same type. This experimental database is also surer, in the sense that it only includes compounds in liquid state at room temperature, when the polarizability of a compound in solution is established via its refractive index in gas or crys- talline state. Indeed, we demonstrate in this paper, a bias in this case.
Temperature-Dependence of Solvent-Induced Stokes Shift and Fluorescence Tunability in Carbon Nanodots
2019
We carried out a cryogenic investigation on the optical properties of carbon dots, aiming to better understand their emission mechanism and the role of the solvent. The solvatochromic Stokes shift is quantified by a low temperature approach which allows freezing of the photo-excited state of carbon dots, preventing any solvation relaxation. Moreover, the reduction in temperature helps to identify the dynamical inhomogeneous contribution to the broadening of the emission band; therefore, disentangling the role of solvent from other types of broadening, such as the homogeneous and the static inhomogeneous contributions.
Pressure-responsive mesoscopic structures in room temperature ionic liquids
2015
Among the most spectacular peculiarities of room temperature ionic liquids, their mesoscopically segregated structural organization keeps on attracting attention, due to its major consequences for the bulk macroscopic properties. Herein we use molecular dynamics simulations to explore the nm-scale architecture in 1-octyl-3-methylimidazolium tetrafluoroborate, as a function of pressure. This study reveals an intriguing new feature: the mesoscopic segregation in ionic liquids is characterized by a high level of pressure-responsiveness, which progressively vanishes upon application of high enough pressure. These results are in agreement with recent X-ray scattering data and are interpreted in …
Simulation of FUS protein condensates with an adapted coarse-grained model
2020
AbstractDisordered proteins and nucleic acids can condense into droplets that resemble the membraneless organelles observed in living cells. MD simulations offer a unique tool to characterize the molecular interactions governing the formation of these biomolecular condensates, their physico-chemical properties, and the factors controlling their composition and size. However, biopolymer condensation depends sensitively on the balance between different energetic and entropic contributions. Here, we develop a general strategy to fine-tune the potential energy function for molecular dynamics simulations of biopolymer phase separation. We rebalance protein-protein interactions against solvation …
Cyclic triureas—synthesis, crystal structures and properties
2008
The synthesis of 24-membered macrocycles is described, in which rigid xanthene units (X) and/or diphenyl ether units (D) as flexible analogues are linked via urea groups. All four possible combinations (XXX, XXD, XDD, DDD) have been obtained with yields of 40-72% for the cyclisation step. In two cases, the respective cyclic hexamers (XXDXXD, XXXXXX) were also isolated. Two compounds have been characterised by a single crystal X-ray analysis of the free triurea (XXD, XDD) and one example (DDD) by its complex with tetrabutylammonium chloride. It shows the chloride anion in the centre of the macrocycle, held by six NH...Cl- hydrogen bonds. The interaction with various other anions has been stu…
Density functional study of Cu2+-phenylalanine complex under micro-solvation environment
2013
Abstract We present an atomistic study carried out using density functional calculations including structural relaxations and Car–Parrinello Molecular Dynamics (CPMD) simulations, aiming to investigate the structures of phenylalanine-copper (II) ([Phe-Cu] 2+ ) complexes and their micro-solvation processes. The structures of the [Phe-Cu] 2+ complex with up to four water molecules are optimized using the B3LYP/6-311++G** model in gas phase to identify the lowest energy structures at each degree of solvation ( n = 0–4). It is found that the phenylalanine appears to be in the neutral form in isolated and mono-hydrated complexes, but in the zwitterionic form in other hydrated complexes (with n …
Reversibility and Diffusion in Mandelythiamin Decarboxylation. Searching Dynamical Effects in Decarboxylation Reactions
2012
Decarboxylation of mandelylthiamin in aqueous solution is analyzed by means of quantum mechanics/molecular mechanics simulations including solvent effects. The free energy profile for the decarboxylation reaction was traced, assuming equilibrium solvation, while reaction trajectories allowed us to incorporate nonequilibrium effects due to the solvent degrees of freedom as well as to evaluate the rate of the diffusion process in competition with the backward reaction. Our calculations that reproduce the experimental rate constant show that decarboxylation takes place with a non-negligible free energy barrier for the backward reaction and that diffusion of carbon dioxide is very fast compared…