Toluene Adsorption by Mesoporous Silicas with Different Textural Properties: A Model Study for VOCs Retention and Water Remediation

In this work, different mesoporous silicas were studied as potential sorbents for toluene, selected as a model molecule of aromatic organic fuel-based pollutants. Three siliceous materials with different textural and surface properties (i.e., fumed silica and mesoporous Santa Barbara Amorphous (SBA)-15 and Mobil Composition of matter (MCM)-41 materials) were considered and the effect of their physico-chemical properties on the toluene adsorption process was studied. In particular, FT-IR spectroscopy was used to qualitatively study the interactions between the toluene molecule and the surface of silicas, while volumetric adsorption analysis allowed the quantitative determination of the toluene adsorption capacity. The combined use of these techniques revealed that textural properties of the sorbents, primarily porosity, are the driving forces that control the adsorption process. Considering that, under real conditions of usage, the sorbents are soaked in water, their hydrothermal stability was also investigated and toluene adsorption by both the gas and aqueous phase on hydrothermally pre-treated samples was studied. The presence of ordered porosity, together with the different pore size distribution and the amount of silanol groups, strongly affected the adsorption process. In toluene adsorption from water, SBA-15 performed better than MCM-41.

Comparison of Umbrella Sampling and Steered Molecular Dynamics Methods for Computing Free Energy Profiles of Toluene Molecules through Phospholipid Bilayers

In this study, we use Molecular Dynamics (MD) to analyze three different corrections of the Steered Molecular Dynamics (SMD) implementation of Jarzynski's Equality (JE) to calculate the FE change for the translocation of a toluene molecule across a lipid bilayer, and compare the accuracy and computational efficiency of these approaches to the results obtained using Umbrella Sampling (US). We show that when computing the free energy profile of a small molecule across a model membrane, the SMD approach suffers from sampling issues that may be alleviated through the use of a slower pulling velocity, but at the cost of computational efficiency. We deduce that, despite its drawbacks, US remains the more viable approach of the two for computing the free energy (FE) profile.

Comparison of Umbrella Sampling and Steered Molecular Dynamics Methods for Computing Free Energy Profiles of Toluene Molecules through Phospholipid Bilayers

In this study, we use Molecular Dynamics (MD) to analyze three different corrections of the Steered Molecular Dynamics (SMD) implementation of Jarzynski's Equality (JE) to calculate the FE change for the translocation of a toluene molecule across a lipid bilayer, and compare the accuracy and computational efficiency of these approaches to the results obtained using Umbrella Sampling (US). We show that when computing the free energy profile of a small molecule across a model membrane, the SMD approach suffers from sampling issues that may be alleviated through the use of a slower pulling velocity, but at the cost of computational efficiency. We deduce that, despite its drawbacks, US remains the more viable approach of the two for computing the free energy (FE) profile.

Vibrational effect on unidirectional time-dependent angular momentum in low-symmetry aromatic ring molecule induced by two linearly polarized UV laser

In this study, we present the results of a theoretical study of the time-dependent angular momentum equation for low-symmetry aromatic ring molecule combine with vibrational effect using two linearly polarized UV laser. We consider the vibrational effect on Toluene molecule and show how the vibrational effect to change of the oscillation periods of unidirectional angular momentum.

Crystal structure of tricarbonyl(N-diphenylphosphanyl-N,N′-diisopropyl-P-phenylphosphonous diamide-κ2P,P′)cobalt(I) tetracarbonylcobaltate(−I) toluene 0.25-solvate

The asymmetric unit of the title compound, [Co(C24H30N2P2)(CO)3][Co(CO)4]·0.25C7H8, consists of two crystallographically independent cations with similar conformations, two anions, and one-half of a toluene molecule disordered about an inversion centre. In the cations, a Co/P/N/P four-membered slightly bent metallacycle is the key structural element. The pendant NH group is not coordinated to the CoIatom, which displays a distorted trigonal–bipyramidal coordination geometry. Weak interionic hydrogen bonds are observed between the NH groups and a carbonyl group of the tetrahedral [Co(CO)4]−anions.

Solvatomorphism of 9,9′-[1,3,4-thiadiazole-2,5-diylbis(2,3-thiophendiyl-4,1-phenylene)]bis[9H-carbazole]: isostructurality, modularity and order–disorder theory

During a systematic investigation of the crystallization behaviour of 9,9′-[1,3,4-thiadiazole-2,5-diylbis(2,3-thiophendiyl-4,1-phenylene)]bis[9H-carbazole] (I), six single crystalline solvates were obtained and characterized by X-ray diffraction at 100 K. The structure of the hemi-2-butanone (MEK) solvate contains two crystallographically independent molecules of (I) related by pseudo-inversion symmetry. The structure is polytypic and composed of non-polar (I) layers and polar solvent layers. It can be described according to an extended order–disorder (OD) theory with relaxed vicinity condition. The observed polytype is of a maximum degree of order (MDO). Layer triples of the second MDO polytype are shown by twinning by inversion. The mono-benzene and mono-toluene solvates are isostructural. Whereas the (I) layers are isostructural to those of the idealized description of the hemi-MEK solvate, the solvent layers are non-polar, resulting in a fully ordered structure. The toluene molecule is ordered, the benzene molecule features disorder. The (I) layers in the sesqui-dioxane and sesqui-benzene solvates are isostructural and unrelated to those in the hemi-MEK, mono-benzene and mono-toluene solvates. The solvent layers are isopointal in both sesqui-solvates, but the stacking differs significantly. The hemi-dideuterodichloromethane (DCM-d 2) solvate is made up of two kinds of (I) rods, spaced by DCM-d 2 molecules. Rods of one kind are similar to analogous rods in the sesqui-dioxane and the sesqui-benzene solvates, whereas rods of the other kind are only remotely related to rods in the hemi-MEK solvate.

[5,10,15,20-Tetrakis(2,6-dimethoxyphenyl)porphyrinato]nickel(II)–toluene–dichloromethane (3/2/4):a mixed solvate

The crystal structure, electronic spectroscopy, and 1H NMR data for the title compound, [Ni(C52H44N4O8)]·0.67C7H8·1.33CH2Cl2, are reported. The compound was prepared by the reaction of nickel(II) acetate with the ligand in refluxing glacial acetic acid. The asymmetric unit consists of 1.5 nickel porphyrins, two dichloromethane molecules and one toluene molecule. One of the nickel–porphyrinate molecules is located on an inversion center and is planar in the solid state, while the other assumes a saddle-shaped geometry. In both cases, the nickel ion is four-coordinate.

trans-Dichlorobis[tris(4-fluorophenyl)phosphine]palladium(II) toluene solvate

The title compound, trans-[PdCl2{P(C6H4F)3}2]·C7H8, where P(C6H4F)3 is tris(4-fluorophenyl)phosphine, crystallizes with both molecules in special positions. The trans-[PdCl2{P(C6H4F)3}2] molecule lies on an inversion centre, resulting in a distorted trans square-planar geometry. The Pd—P and Pd—Cl distances are 2.3398 (12) and 2.2955 (13) Å, respectively, and the P—Pd—Cl angle is 87.58 (5)°. The effective cone angle for the tris(4-fluorophenyl)phosphine group was calculated to be 152°. The toluene molecule lies on a twofold rotation axis.

Cation-π Interactions in the Solid State: Crystal Structures of M+(benzene)2CB11Me12- (M = Tl, Cs, Rb, K, Na) and Li+(toluene)CB11Me12-

In these crystal structures, the relatively weak electrostatic interactions between the bulky CB11Me12- anion and the title cations permit cation-π interactions in the solid state. In all cases, single-crystal X-ray diffraction analysis reveals η6-arene-cation interactions within 10% of the expected van der Waals distance. The Tl+, Cs+, Rb+, and K+ structures are isomorphous, with the benzene molecules sandwiching the cation and four anions equatorially disposed in a nearly square arrangement. Both the cation and the near-square of closest anions are positioned to interact favorably with the local dipoles of benzene. The smaller Na+ crystallizes in polymeric chains with a nearly tetrahedrally coordinated cation in van der Waals contact with two anions and two benzene molecules in a tilted-sandwich arrangement. The Li+ structure possesses two motifs, a simple van der Waals sandwich of a toluene molecule and an anion, and chains of half-occupied toluene-Li complexes on inversion centers between anions. The simple van der Waals model is reasonably accurate for the cation-arene distances, only slightly underestimating the separation (2-10% deviation), with worse agreement for the smaller cations.