Detailed investigation of the binding abilities of the heterodomain of a multiHis cyclopeptide toward Cu(II) ions.

Cyclopeptides hold significant relevance in various fields of science and medicine, due to their unique structural properties and diverse biological activities. Cyclic peptides, characterized by intrinsically higher conformational order, exhibit remarkable stability and resistance to proteolytic degradation, making them attractive candidates for developing targeted drug delivery systems. The aim of this work is to elucidate the unique coordination properties of the multi-His cyclic peptide with c(HDHKHPHHKHHP) sequence (HDCP - heterodomain cyclopeptide).

Through-space scalar spin-spin coupling: from rigid intramolecular cases to short-lived van der Waals complexes.

We will discuss, with the help of few selected examples, how the concept of through-space scalar spin-spin coupling between non covalently bonded nuclei has evolved in recent years. We will first present systems where 'no covalent bond' actually means that the two atoms are separated by a large number of bonds; then we will see cases where it is referred to true van der Waals dimers, but with the two atoms somehow constrained in their positions; we will finish with the most recent examples of liquids and even gaseous mixtures with full translational degrees of freedom in a regime of intermolecular/interatomic fast exchange.

Influence of Anion Species on Liquid-Liquid Phase Separation in [EMIm][X]/Benzene Mixtures.

When a molar excess of benzene is mixed with an ionic liquid (IL), liquid-liquid phase separation may appear with a pure liquid phase almost composed of only benzene molecules separated from a liquid clathrate phase with benzene molecules dissolved in the IL. Our previous study (J. Phys.

Pathway for Water Transport through Breathable Nanocomposite Membranes of PEBAX with Ionic Liquid [CCim]Cl.

Water transport through membranes is an attractive topic among the research dedicated to dehydration processes, microenvironment regulation, or more simply, recovery of freshwater. Herein, an atomistic computer simulation is proposed to provide new insights about a water vapor transport mechanism through PEBAX membranes filled with ionic liquid (IL) [CCim]Cl. Starting from experimental evidence that indicates an effective increase in water permeation as the IL is added to the polymer matrix (e.

Phase coexistence in [C/CMIm][NO] ionic-liquid mixtures and first-order phase transitions from homogeneous liquid to smectic B by varying the cation ratio.

We perform molecular dynamics simulations to investigate the transition processes of [C/CMIm][NO] binary mixtures by varying the cation ratio of C to C at a fixed temperature of 400 K. The cation ratio is tuned by ranging C percentage from 0% to 100% with a fixed number of 4096 total simulated ion pairs. Our simulated-annealing results indicate that, at 400 K, pure C is a homogeneous liquid whilst pure C is an ionic liquid crystal (ILC) of smectic-B (SmB) type.

Computational NMR spectroscopy of Tl.

We have investigated the NMR chemical shift of Tl in several thallium compounds, ranging from small covalent Tl(I) and Tl(III) molecules to supramolecular complexes with large organic ligands and some thallium halides. NMR calculations were run at the ZORA relativistic level, with and without spin-orbit coupling using few selected GGA and hybrid functionals, namely BP86, PBE, B3LYP, and PBE0. We also tested solvent effects both at the optimization level and at the NMR calculation step.

Phase behaviour of mixtures of charged soft disks and spheres.

We have investigated the phase behaviour of mixtures of soft disks (Gay-Berne oblate ellipsoids, GB) and soft spheres (Lennard-Jones, LJ) with opposite charge as a model of ionic liquid crystals and colloidal suspensions. We have used constant volume Molecular Dynamics simulations and fixed the stoichiometry of the mixture in order to have electroneutrality; three systems have been selected GB : LJ = 1 : 2, GB : LJ = 1 : 1 and GB : LJ = 2 : 1. For each system we have selected three values of the scaled point charge * of the GB particles, namely 0.

Activation of Vegetable Oils by Reaction with Maleic Anhydride as a Renewable Source in Chemical Processes: New Experimental and Computational NMR Evidence.

Vegetable oils are bio-based and sustainable starting materials that can be used to develop chemicals for industrial processes. In this study, the functionalization of three vegetable oils (grape, hemp, and linseed) with maleic anhydride was carried out either by conventional heating or microwave activation to obtain products that, after further reactions, can enhance the water dispersion of oils for industrial applications. To identify the most abundant derivatives formed, trans-3-octene, methyl oleate, and ethyl linoleate were reacted as reference systems.

Correction: The structuring effect of the alkyl domains on the polar network of ionic liquid mixtures: a molecular dynamics study.

Correction for 'The structuring effect of the alkyl domains on the polar network of ionic liquid mixtures: a molecular dynamics study' by Valerio Mazzilli , , 2022, , 18783-18792, https://doi.org/10.1039/D2CP02786K.

The structuring effect of the alkyl domains on the polar network of ionic liquid mixtures: a molecular dynamics study.

By using molecular dynamics simulations, we investigate the structural and dynamic properties of mixtures of 1,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide, [CCim][TfN] and 1-dodecyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [CCim][TfN] (also C and C in short). Such mixtures feature an imidazolium bistriflimide salt with a very short alkyl chain, not giving rise to any nano-segregation as a pure component, with another one with a longer alkyl chain that exhibits a substantial nano-segregation as a pure liquid. As the mole fraction of the long-chain component C is increased, the so-called pre-peak of the structure factor (), occurring in the region 1-3 nm, shows a shift to higher values of the wavevector , mirroring a decrease of the corresponding correlation length.

The effect of hydration on the stability of ionic liquid crystals: MD simulations of [CCim]Cl and [CCim]Cl·HO.

The thermal range of the stability of Ionic Liquid Crystal (ILC) phases of imidazolium ILCs, and the type of the mesophase itself are affected by several molecular structural features, the two prominent ones being the alkyl chain length and the counter-anion. Hydration is also very important: monohydrate samples of 1-alkyl-3-methylimidazolium halides have a higher clearing point and a wider thermal range of the stability of the ionic smectic phase, compared with the analogous anhydrous sample. To understand the reasons, at a microscopic level, for such increased stability due to hydration, we run classical Molecular Dynamics (MD) simulations of a typical ionic liquid crystal, 1-tetradecyl-3-methylimidazolium chloride, and of its monohydrate form.

Xenon Diffusion in Ionic Liquids with Blurred Nanodomain Separation.

The dynamics of xenon gas, loaded in a series of 1-alkyl-3-methylimidazolium based ionic liquids, probes the formation of increasingly blurred polar/apolar nanodomains as a function of the anion type and the cation chain length. Exploiting Xe NMR spectroscopy techniques, like Pulse Gradient Spin Echo (PGSE) and inversion recovery (IR), the diffusion motion and relaxation times are determined for 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C C im][TFSI]. A correlation between the ILs nano-structure and both xenon diffusivity and relaxation times, as well as chemical shifts, is outlined.

Liquid-Liquid Phase Separation of Viologen Bistriflimide/Benzene Mixtures: Role of the Dual Ionic and Organic Nature of Ionic Liquids.

Liquid-liquid phase separation occurs at room temperature when mixing an excess of benzene with solid viologen bistriflimide salts with various alkyl side-chain lengths. A liquid phase composed of (almost) pure benzene is above the other sponge-like liquid phase with salt absorbed in benzene. Nuclear magnetic resonance experiments indicate that the mole ratio of benzene/salt in the sponge-like phase remains unchanged upon varying the amounts of (nonexcessive) salt or benzene.

Xenon Dynamics in Ionic Liquids: A Combined NMR and MD Simulation Study.

The translational dynamics of xenon gas dissolved in room-temperature ionic liquids (RTILs) is revealed by Xe NMR and molecular dynamics (MD) simulations. The dynamic behavior of xenon gas loaded in 1-alkyl-3-methylimidazolium chloride, [CCim]Cl ( = 6, 8, 10), and hexafluorophosphate, [CCim][PF] ( = 4, 6, 8, 10) has been determined by measuring the Xe diffusion coefficients and NMR relaxation times. The analysis of the experimental NMR data demonstrates that, in these representative classes of ionic liquids, xenon motion is influenced by the length of the cation alkyl chain and anion type.

Computational NMR Spectroscopy of Ionic Liquids: [CCim]Cl/Water Mixtures.

In this work, I have analyzed the structure of binary mixtures of 1-butyl-3-methylimidazolium chloride ionic liquid, [CCim]Cl, and water, using computational NMR spectroscopy. The structure of the complex fluid phase, where the ionic and hydrophobic nature of ionic liquids is further complicated by the addition of water, is first generated by classical Molecular Dynamics (MD) and then validated by calculating the NMR properties with DFT at the ONIOM(B3LYP/cc-pVTZ//B3LYP/3-21G) on clusters extracted during the MD trajectories. Three ionic liquid/water mixtures have been considered with the [CCim]Cl mole fraction of 1.

One-bond J( N─ F) spin-spin coupling constants of cationic fluorinating reagents: Insights from DFT calculations.

We have investigated, by means of density functional theory protocols, the one-bond J( N─ F) spin-spin coupling constants in a series of fluorinating reagents, containing the N─F bond, recently studied experimentally. The results of the calculations show a very good linear relationship with the experimental values, even though only the M06-2X(PCM)/pcJ-2//B3LYP/6-311G(d,p) level affords a very low mean absolute error. The calculations allow to analyze the various molecular orbitals contributions to the J coupling and to rationalize the observed positive sign, corresponding to a negative sign of the reduced spin-pin coupling constant K(N─F).

Influence of the ion size on the stability of the smectic phase of ionic liquid crystals.

The thermotropic phase behavior of ionic liquids and ionic liquid crystals based on novel N-alkyl-3-methylpyridinium halides, trihalides and dichloroiodates was experimentally studied by polarized optical spectroscopy (POM) and differential scanning calorimetry (DSC) as well as by molecular dynamics (MD) simulation. In the experiments, the existence and thermal range of stability of the smectic phase of these ionic liquid crystals are found to strongly depend on the volume ratio between the cation and anion, that is their relative size. Only compounds with a relatively large volume ratio of the cation to anion, i.

A coarse-grained model of ionic liquid crystals: the effect of stoichiometry on the stability of the ionic nematic phase.

We have investigated, by means of molecular dynamics simulations, the phase behaviour of mixtures of charged ellipsoidal Gay-Berne (GB) particles and spherical Lennard-Jones (LJ) particles, as a coarse-grained model of ionic liquid crystals (ILCs). The anisotropic GB particles represent cations usually found in ILCs, for example, pyridinium or bipyridinium salts, while the spherical LJ particles are taken as a model of anions like common halides, hexafluorophosphate and tetrafluoroborate. Here we have focused our attention on the effect of the stoichiometry of the system (that is, the GB : LJ ratio n : m in the salt formula [GB]n[LJ]m) on the stability and thermal range of the ionic liquid crystal phases formed, with special attention to the ionic nematic phase.

The Te Chemical Shift of Diphenyl Ditelluride: Chasing Conformers over a Flat Energy Surface.

The interest in diphenyl ditelluride (Ph₂Te₂) is related to its strict analogy to diphenyl diselenide (Ph₂Se₂), whose capacity to reduce organic peroxides is largely exploited in catalysis and green chemistry. Since the latter is also a promising candidate as an antioxidant drug and mimic of the ubiquitous enzyme glutathione peroxidase (GPx), the use of organotellurides in medicinal chemistry is gaining importance, despite the fact that tellurium has no recognized biological role and its toxicity must be cautiously pondered. Both Ph₂Se₂ and Ph₂Te₂ exhibit significant conformational freedom due to the softness of the inter-chalcogen and carbon⁻chalcogen bonds, preventing the existence of a unique structure in solution.

New Sulfur-Containing Polyarsenicals from the New Caledonian Sponge Echinochalina bargibanti.

Arsenicin A (C₃H₆As₄O₃) was isolated from the New Caledonian poecilosclerid sponge , and described as the first natural organic polyarsenic compound. Further bioguided fractionation of the extracts of this sponge led us to isolate the first sulfur-containing organic polyarsenicals ever found in Nature. These metabolites, called arsenicin B and arsenicin C, are built on a noradamantane-type framework that is characterized by an unusual As⁻As bonding.

"Through-Space" Relativistic Effects on NMR Chemical Shifts of Pyridinium Halide Ionic Liquids.

We have investigated, using two-component relativistic density functional theory (DFT) at ZORA-SO-BP86 and ZORA-SO-PBE0 level, the occurrence of relativistic effects on the H, C, and N NMR chemical shifts of 1-methylpyridinium halides [MP][X] and 1-butyl-3-methylpyridinium trihalides [BMP][X ] ionic liquids (ILs) (X=Cl, Br, I) as a result of a non-covalent interaction with the heavy anions. Our results indicate a sizeable deshielding effect in ion pairs when the anion is I and I . A smaller, though nonzero, effect is observed also with bromine while chlorine based anions do not produce an appreciable relativistic shift.

Aggregation behavior of dihexadecylviologen bistriflimide ionic liquid crystal in different solvents: influence of polarity and concentration.

Solutions of 1,1'-dihexadecyl-4,4'-bipyridinium di[bis(trifluoromethanesulfonyl)imide] salt, also known as dihexadecylviologen bistriflimide, in deuterated acetonitrile (ACN), dichloromethane (DCM) and chloroform (CDCl3), respectively, were investigated by the combination of 1H and DOSY NMR spectroscopy, DFT calculations and MD simulation to understand the influence of solvent polarity and solute concentration (10-5-10-1 M) on its aggregation behavior. We found that the polar solvent acetonitrile (ACN) does not favor ion aggregation and cluster formation. In the whole range of concentrations investigated, the system appears to be dominated by neutral ion pairs composed of one cation and two anions, possibly in fast equilibrium (on the NMR time scale) with small or slightly larger aggregates.

P and Pt solid-state NMR and DFT studies on platinum(i) and platinum(ii) complexes.

31P and 195Pt solid state NMR spectra of anti-[(PHCy)ClPt(μ-PCy2)2Pt(PHCy)Cl] (3) and [(PHCy2)Pt(μ-PCy2)(κ2P,O-μ-POCy2)Pt(PHCy2)] (Pt-Pt) (4) were recorded under cross polarization/magic-angle spinning conditions (31P) or with the cross polarization/Carr-Purcell-Meiboom-Gill pulse sequence (195Pt) and compared to the data obtained by relativistic DFT calculations of 31P and 195Pt CS tensors and isotropic shielding at the ZORA spin-orbit level. A good agreement with the experimental results was found and it was possible to rationalize the chemical shift differences of 195Pt and 31P nuclei between compounds 3 and 4 as mostly due to a change (in opposite directions for 195Pt and 31P) of the principal component of the shielding tensor perpendicular to the molecular plane defined by the Pt and P atoms. Paramagnetic and spin-orbit terms were found to be the most important contributions to 195Pt and 31P shielding.

Ion pairing in 1-butyl-3-methylpyridinium halide ionic liquids studied using NMR and DFT calculations.

We present the 1H, 13C and 15N NMR chemical shifts of bulk ionic liquids based on 1-butyl-3-methylimidazolium (the cation also known as 1-butyl-3-picolinium) halides (Cl-, Br- and I-) and tribromide (Br3-) salts. A characterization in solution of the analogous ICl2- and I3- salts is also reported. A series of DFT calculations has been run to predict the features of the NMR spectra of the pure ILs based on a few selected supramolecular ionic aggregates.