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In recent years, external electric fields (EEFs) have captured some spotlight as novel effectors of chemical change. EEFs directly impact the structure of molecular systems. For example, aligning an electric field along a specific bond-axis leads to either shortening or elongation of the bond (and ultimately bond breaking). Furthermore, EEFs enable unprecedented control over chemical reactivity. Orienting an electric field along the so-called “reaction-axis,” the direction in which the electrons reorganize during the conversion from reactant to product, leads to catalysis or inhibition and can induce mechanistic crossover from concerted to stepwise reactions. Off-reaction-axis orientation enables control over the stereoselectivity of reactions and disables forbidden–orbital mixing. Two-directional fields enable control over both reactivity and selectivity. In this advanced review, we offer an overview of this rapidly evolving research field with a focus on the valence bond modeling of EEF effects and the insight it offers. A wide variety of examples will be considered and a link to the experiment will be made throughout. We end by offering some perspectives in which we postulate that, as experimental techniques continue to mature, EEFs could potentially become a generally applicable “zapping” tool to facilitate elaborate chemical syntheses. This article is categorized under:. Structure and Mechanism > Reaction Mechanisms and Catalysis.

International audience; Although dibenzyl disulfide (DBDS) is used as a mineral oil stabilizer, its presence in electrical transformer oil is associated as one of the major causes of copper corrosion and subsequent formation of copper sulfide. In order to prevent these undesirable processes, MY zeolites (with M = Li, Na, K, Cs, Cu or Ag) are proposed to adsorb molecularly DBDS. In this study, different MY zeolites are investigated at the DFT+D level in order to assess their ability in DBDS adsorption. It was found that CsY, AgY and CuY exhibit the best compromise between high interaction energies and limited S-S bond activation, thus emerging as optimal adsorbents for DBDS

International audience; "Click" chemistry, used to promote nanoparticle assemblies, is a powerful strategy which has emerged very recently to control the spatial arrangement of nanoparticles onto surfaces. Such a strategy may be of high interest for applications such as magnetic recording media or magnetic sensors which are based on the fine control of the collective properties of nanoparticles. Nevertheless, self-assembly driven by clickable functional groups still remains to be understood. Mixed self-assembled monolayers (SAMs) of alkane−thiol molecules were used to control the spatial arrangement of nanoparticles onto gold substrates. This approach was combined with click chemistry in order to control the immobilization of nanoparticles on selective areas through specific copper catalyzed alkyne−azide cycloaddition (CuAAC) reaction. Mixed SAMs consist of co-adsorbed 11-(undec-1-ynyl)thiol (S-CC) and 12-(dodecane)thiol (S-CH 3) molecules. The variation of the molar ratio between both molecules resulted in significant modulation of the structure of nanoparticle assemblies. The spatial arrangement of nanoparticles revealed the very complex structure of alkyne/methylene terminated mixed SAMs. Alkyne terminal groups could not be only studied by the usual characterization surface techniques such as PM-IRRAS and XPS. Therefore, azido-terminated nanoparticles acted as probing agents to determine the spatial distribution of alkyne groups at the surface of mixed SAMs. This approach was combined with scanning tunneling microscopy (STM) and DFT calculations to get a deeper insight into the structure of mixed SAMs of S-CC and S-CH 3 molecules. Gold substrate topography, chemical affinity of molecules, intermolecular interactions and length of alkyl chains were found to be critical parameters that rule the SAM structure.

Supersonic atmospheric plasma spray (SAPS) technique is a classical method which is employed to coat the carbon/carbon (C/C) composites by nano-hydroxyapatite (HAp) powders to decrease the biologically inert, hydrophobic drawbacks of substrate surfaces. In recent years, profiting from the promoting of energy conservation and environmental protection, more emphasis was placed on industrial manufacturing to simplify the experimental steps. This paper aims to study the preparation of nano-HAp coatings by suspension plasma spray (SPS) instead of the original SAPS technique. A denser, more uniform and less defective coating is successfully fabricated on C/C substrate using SPS technique. More important, fewer surface flaws in SPS coating could be observed by scanning electron microscopy (SEM) which shows that the large drawbacks of the coating have disappeared during spraying process. Meanwhile, except for HAp, phase compositions of the SPS coating appear with slight calcium oxide (CaO, 0.8%) and tricalcium phosphate (TCP, 30.7%), and then all CaO as well as TCP phases transform into dicalcium phosphate anhydrous (DCPA, 60.6%) after microwave-hydrothermal (MH) treatment. Thermal analysis (TG/DSC) reveals that SPS coating (97.51%) has a higher thermal stability than that of the SAPS coating (82.37%). Also, in comparison, the SPS coating after MH treatment (SPS-MH coating) exhibits better thermal properties (92.76%). In addition, compared to the SAPS and SPS coatings, due to the more flaw reduction and phase transformation, SPS-MH coating shows a better biological properties according to the surface microstructure in simulation body fluid (SBF) solution and cell spreading area on coating. The highest corrosion resistance with the current density of 3.9798 × 10−7 A/cm2 and a potential of 0.0419 V is achieved for SPS-MH coating.

The range-separation parameter in tuned, range-separated exchange–correlation functionals is investigated in two contexts. First, the system dependence of the parameter is investigated for a series of systems obtained by successively ionizing a single species, paying particular attention to the degree of linearity in the energy versus electron number curve. The parameter exhibits significant system dependence and, therefore, achieving near-linearity in one segment of the curve leads to strong nonlinearity in other segments. This provides a challenging test case for the development of new functionals designed to overcome the known problems of this class of functional. Next, the study considers whether a range-separation parameter tuned to a Koopmans energy condition is also applicable for the analogous density condition. This is tested by comparing two formulations of the Fukui function of conceptual density functional theory, for three representative systems. Both formulations yield the same general features and are not highly sensitive to the range-separation parameter. However, the agreement between the two is near-optimal when the energy-tuned parameter is used, indicating that this parameter is applicable for the analogous density condition.

The nature of reduced Cr species on silica is still under debate. In this work, combined DFT and in situ UV-vis DRS investigations of reduction of chromia-silica catalyst have been done. Advanced periodic and cluster models of amorphous silica are applied to reproduce the heterogeneity of surface Cr species. Geometrical parameters, vibrational frequencies, excitation energies, and relative stabilities of Cr sites are determined. It is predicted that reduction of monomeric Cr(VI) species to Cr(IV) sites is highly exergonic, whereas deep reduction to Cr(II) is less thermodynamically favored. Dimeric Cr(VI) species can finally be reduced to Cr(III) or Cr(II). In situ UV-vis DRS studies indicate that Cr(VI) species are selectively converted to Cr(II) under CO in dry conditions, whereas reduction with dry H2 leads to formation of Cr(III) and Cr(II). For both reducing agents, the presence of water hampers deep reduction to Cr(II), which can be explained by reoxidation/hydrolysis processes.

In the present study, the effect of different types of iron oxides, which naturally exist on steel substrate, on the interfacial interaction between an epoxy coating and a carbon steel substrate was studied at the molecular/atomic level by employing molecular dynamics (MD) simulations and quantum mechanics (QM) calculations. Three types of iron oxide, that is, ferrous oxide (FeO), ferric oxide (Fe2O3, hematite), and ferrous ferric oxide (Fe3O4, magnetite), were considered for modeling, and their binding energies were calculated and compared by altering the concentration of hydroxide groups on the surface. To probe the effect of curing agent on interfacial interactions, computations were performed for either uncured or aminoamide-cured epoxy resins. The effect of the acid–base properties of the iron oxide on the molecular bonding was theoretically investigated by imposing diverse iron hydroxide/oxide termination groups. Noticeably, MD and QM calculations confirmed rather well earlier experimental evaluatio...

The most relevant manifestations of ligand noninnocence of quinone and bipyridine derivatives are thoroughly scrutinized and discussed through an extensive and systematic set of octahedral ruthenium complexes, [(en)2RuL]z, in four oxidation states (z = +3, +2, +1, and 0). The characteristic structural deformation of ligands upon coordination/noninnocence is put into context with the underlying electronic structure of the complexes and its change upon reduction. In addition, by means of decomposing the corresponding reductions into electron transfer and structural relaxation subprocesses, the energetic contribution of these structural deformations to the redox energetics is revealed. The change of molecular electron density upon metal- and ligand-centered reductions is also visualized and shown to provide novel insights into the corresponding redox processes. Moreover, the charge distribution of the π-subspace is straightforwardly examined and used as indicator of ligand noninnocence in the distinct oxidation states of the complexes. The aromatization/dearomatization processes of ligand backbones are also monitored using magnetic (NICS) and electronic (PDI) indicators of aromaticity, and the consequences to noninnocent behavior are discussed. Finally, the recently developed effective oxidation state (EOS) analysis is utilized, on the one hand, to test its applicability for complexes containing noninnocent ligands, and, on the other hand, to provide new insights into the magnitude of state mixings in the investigated complexes. The effect of ligand substitution, nature of donor atom, ligand frame modification on these manifestations, and measures is discussed in an intuitive and pedagogical manner M.G. and P.S. are thankful for financial support from the FEDER grant UNGI10-4E-801 and MINECO grant CTQ2014-59212-P/BQU

The germylene [(i-Pr)2NB(N-2,6-Me2C6H3)2]Ge (1) was easily accessible by the reaction of the in situ prepared dilithium precursor [(i-Pr)2NB(N-2,6-Me2C6H3)2]Li2 with GeCl2·dioxane complex. The bonding situation in 1 has been also described from the theoretical point of view. This germylene is smoothly oxidized by diphenyldichalcogenides PhEEPh, I2 or MeI to produce bis(phenylchalcogenato)germanes [(i-Pr)2NB(N-2,6-Me2C6H3)2]Ge(EPh)2 [where E = S (2), Se (3) and Te (4)] and corresponding iodo-derivatives [(i-Pr)2NB(N-2,6-Me2C6H3)2]GeI2 (5) and [(i-Pr)2NB(N-2,6-Me2C6H3)2]Ge(Me)I (6). The treatment of 1 with bromine resulted in the unexpected formation of a heteroleptic germylene compound [(i-Pr)2NB(NH-2,6-Me2C6H3)(N-2,6-Me2C6H3)]GeBr (7) and a germanium(IV) compound [(i-Pr)2NB(NH-2,6-Me2C6H3)(N-2,6-Me2C6H3)]GeBr3 (8). The reaction of germylene 1 with 2,3-dimethylbutadiene and 2,3-dibenzylbutadiene resulted in spiro-compounds [(i-Pr)2NB(N-2,6-Me2C6H3)2]Ge[CH2C(R)C(R)CH2] [where R = Me (10) and benzyl (11)]. Similarly, compound [(i-Pr)2NB(N-2,6-Me2C6H3)2]Ge[N(Dip)CHCHN(Dip)] (12) (where Dip = 2,6-i-Pr2C6H3) was obtained by the reaction of 1 with corresponding diimine (Dip)NCHCHN(Dip). All compounds were characterized by multinuclear NMR spectroscopy and their molecular structures were unambiguously established using single-crystal X-ray diffraction analysis.

Several expanded porphyrins switch between Hückel, Möbius and twisted-Hückel topologies, encoding different aromaticity and NLO properties. Since the topological switch can be induced by different external stimuli, expanded porphyrins represent a promising platform to develop molecular switches for molecular electronic devices. In order to determine the optimum conditions for efficient molecular switches from octaphyrins, we have carried out a comprehensive quantum chemical study focusing on the conformational preferences and aromaticity of [36]octaphyrins. Different external stimuli for triggering the topological switch have been considered in our work, such as protonation and redox reactions. Importantly, the structure–property relationships between the molecular conformation, the number of π-electrons and aromaticity in octaphyrins have been established by using energetic, magnetic, structural and reactivity descriptors. Remarkably, we found that the aromaticity of octaphyrins is highly dependent on the π-conjugation topology and the number of π-electrons and it can be modulated by protonation and redox reactions. A non-aromatic figure-eight conformation is strongly preferred by neutral [36]octaphyrins that switches to a Möbius aromatic conformation upon protonation. Such a change of topology involves an aromaticity switch in a single molecule and is accompanied by a drastic change in the NLO properties. In contrast, the twisted-Hückel topology remains the most stable one in the oxidized and reduced species, but the aromaticity is totally reversed upon redox reactions. Aromaticity is shown to be a key concept in expanded porphyrins, determining the electronic, magnetic and NLO properties of these macrocycles.

textcopyright 2018 American Chemical Society. Green, stable, and wide electrochemical window deep eutectic solvents (DESs) are ideal candidates for electrochemical systems. However, despite several studies of their bulk properties, their structure and properties under electrified confinement have barely been investigated, which has hindered widespread use of these solvents in electrochemical applications. In this Letter, we explore the electrical double layer structure of 1:2 choline chloride-urea (Reline), with a particular focus on the electrosorption of the hydrogen bond donor on a graphene electrode using atomistic molecular dynamics simulations. We discovered that the interface is composed of a mixed layer of urea and counterions followed by a mixed charged clustered structure of all of the Reline components. This interfacial structuring is strongly dependent on the balance between intermolecular interactions and surface polarization. These results provide new insights into the electrical double layer structure of a new generation of electrolytes whose interfacial structure can be tuned at the molecular level., info:eu-repo/semantics/published

Hydroxylated amorphous silica nanoparticles were modeled using a combination of computational techniques at different levels of length scales from Angstrom to hundreds of nanometers. Using quantum chemical ab initio methods, force field Monte Carlo methods, reactive force field simulations, and numerical model calculations, including BET theory calculations it was possible to describe and model the physico-chemical properties of hydroxylated amorphous silica. The results are compared with experimental data and found to be in good agreement with the theory, confirming the reliability of the computational method and the silica model structure.

In view of its use as reactivity theory, Conceptual Density Functional Theory (DFT), introduced by Parret al., has mainly concentrated up to now on theE=E[N,v]functional. However, different ensemble representations can be used involving other variables also, such asρandμ. In this study, these different ensemble representations (E, Ω,F, andR) are briefly reviewed. Particular attention is then given to the corresponding second-order (functional) derivatives, and their analogies with the second-order derivatives of thermodynamic state functionsU,F,H, andG, which are related to each otherviaLegendre transformations, just as the DFT functionals (Nalewajski and Parr, 1982). Starting from an analysis of the convexity/concavity of the DFT functionals, for which explicit proofs are discussed for some cases, the positive/negative definiteness of the associated kernels is derived and a detailed comparison is made with the thermodynamic derivatives. The stability conditions in thermodynamics are similar in structure to the convexity/concavity conditions for the DFT functionals. Thus, the DFT functionals are scrutinized based on the convexity/concavity of their two variables, to yield the possibility of establishing a relationship between the three second-order reactivity descriptors derived from the considered functional. Considering two ensemble representations,FandΩ,Fis eliminated as it has two dependent (extensive) variables,Nandρ. ForΩ, on the other hand, which is concave for both of its intensive variables (μandυ), an inequality is derived from its three second-order (functional) derivatives: the global softness, the local softness, and the softness kernel. Combined with the negative value of the diagonal element of the linear response function, this inequality is shown to be compatible with the Berkowitz-Parr relationship, which relates the functional derivatives ofρwithυ, at constantNandμ. This was recently at stake upon quantifying Kohn’s Nearsightedness of Electronic Matter. The analogy of the resulting inequality and the thermodynamic inequality for theGderivatives is highlighted. Potential research paths for this study are briefly addressed; the analogies between finite-temperature DFT response functions and their thermodynamic counterparts and the quest for analogous relationships, as derived in this paper, for DFT functionals that are analogues of entropy-dimensioned thermodynamic functions such as the Massieu function.

International audience; Previously, we have proposed a relationship between the adsorption modes of a simple molecule (NO) and the behavior of the nanometer-scale monometallic clusters after this adsorption. More precisely, a set of experiments seems to show that dissociative adsorption of NO leads to the sintering of nanometer-scale metallic particles (NSMPs), whereas molecular adsorption is related to the oxidation. Although numerous investigations have been published on catalytic or electrocatalytic reactions where the interaction between carbon monoxide and NSMPs is involved, only a few studies have been dedicated to the adsorption of CO on NSMPs. This purely energetic approach is discussed through different results already published in the literature and through some recent theoretical calculations related to solid state physics. Although interesting and systematic results are gathered here and are partly explained, this adsorption process still remains a challenge.

In view of its use as reactivity theory, Conceptual Density Functional Theory (DFT), introduced by Parr et al., has mainly concentrated up to now on the E=E[N, v] functional. However, different ensemble representations can be used involving other variables also, such as ρ and μ. In this study, these different ensemble representations (E, Ω, F, and R) are briefly reviewed. Particular attention is then given to the corresponding second-order (functional) derivatives, and their analogies with the second-order derivatives of thermodynamic state functions U, F, H, and G, which are related to each other via Legendre transformations, just as the DFT functionals (Nalewajski and Parr, 1982). Starting from an analysis of the convexity/concavity of the DFT functionals, for which explicit proofs are discussed for some cases, the positive/negative definiteness of the associated kernels is derived and a detailed comparison is made with the thermodynamic derivatives. The stability conditions in thermodynamics are similar instructure to the convexity/concavity conditions for the DFT functionals. Thus, the DFT functionals are scrutinized based on the convexity/concavity of their two variables, to yield the possibility of establishing a relationship between the three second-order reactivity descriptors derived from the considered functional. Considering two ensemble representations, F and Ω, F is eliminated as it has two dependent (extensive) variables, N and ρ. For Ω, on the other hand, which is concave for both of its intensive variables (μ and υ), an inequality is derived from its three second-order (functional) derivatives:the global softness, the local softness, and the softness kernel. Combined with the negative value of the diagonal element of the linear response function, this inequality is shown to be compatible with the Berkowitz-Parr relationship, which relates the functional derivatives of ρ with υ, at constant N and μ. This was recently at stake upon quantifying Kohn's Nearsightedness of Electronic Matter. The analogy of the resulting inequality and the thermodynamic inequality for the G derivatives is highlighted. Potential research paths for this study are briefly addressed; the analogies between finite-temperature DFT response functions and their thermodynamic counterparts and the quest for analogous relationships, as derived in this paper, for DFT functionals that are analogues of entropy-dimensioned thermodynamic functions such as the Massieu function.

現在わが国において使用を許可されている食用色素について, 可視光照射下におけるグアノシンの光分解反応に基づき, その光増感作用を検討した。その結果, ハロゲン多置換キサンテン系色素が光増感作用を有することを明らかにした。さらに, その光増感作用の強さは, 食用赤色3号(エリスロシン), The photosensitizing capability of food dyes, which are currently allowed to use as food additives in Japan, was examined on the basis of photodegradation of guanosine under irradiation of visible light. The results clearly demonstrated that the poly-halogenated xanthene dyes showed the photosensitizing capability, and it increased in the following order : erythrosine

Pauling long bond orders have previously been used to obtain qualitative insight in the transmission through nanographenes. Here we show that this long bond order, the atom–atom polarizability (a measure for delocalization) and the transmission probability are intimately linked and that their relationships are valid for all alternant hydrocarbons. These relationships allow a simple rationalization of the transport properties of a variety of molecules considered in molecular electronics. As an example, some molecular wires such as oligo( p -phenylene) are studied, leading to a simple explanation for the experimentally observed exponential decay of the transmission probability with the number of phenyl units.

We investigate the local polarisability or polarisability density using both a conceptual density functional theory approach based on the linear response function and time-dependent density functional theory. Using a zero frequency in the latter, we can immediately compare both approaches. Using an analytical expression for the linear response kernel, we are able to systematically analyse α(r) throughout the periodic table. An extension to molecules is also made with a study of the CO molecule retrieving the connection between local softness and local polarisability.

The establishment of an internally consistent scale of noble gas electronegativities is a long-standing problem. In the present study, the problem is attacked via the Mulliken definition, which in recent years gained widespread use to its natural appearance in the context of conceptual density functional theory. Basic ingredients of this scale are the electron affinity and the ionization potential. Whereas the latter can be computed routinely, the instability of the anion makes the judicious choice of computational technique for evaluating electron affinities much more tricky. We opted for Puiatti's approach, extrapolating the energy of high ε solvent stabilized anions to the ε = 1 (gas phase) case. The results give negative electron affinity values, monotonically increasing (except for helium which is an outlier in most of the story) to almost zero at eka-radon in agreement with high level calculations. The stability of the B3LYP results is successfully tested both via improving the level of theory (CCSD(T)) and expanding the basis set. Combined with the ionization energies (in good agreement with experiment), an electronegativity scale is obtained displaying (1) a monotonic decrease of χ when going down the periodic table, (2) top values not for the noble gases but for the halogens, as opposed to most (extrapolation) procedures of existing scales, invariably placing the noble gases on top, and (3) noble gases having electronegativities close to the chalcogens. In the accompanying hardness scale (hardly, if ever, discussed in the literature) the noble gases turn out to be by far the farthest the hardest elements, again with a continuous decrease with increasing Z. Combining χ value of the halogens and the noble gases the Ng(δ+)F(δ-) bond polarity emerging from ab initio calculations naturally emerges. In conclusion, the chemistry of the noble gases is for a large part determined by their extreme hardness, equivalent to a high resistance to change in its electronic population coupled to their high electronegativity.

The nature and origin of ion-π and ion-σ interactions has been systematically investigated using dispersion-corrected density functional theory and the recently developed noncovalent interaction (NCI) method. A detailed analysis of these interactions is performed with the aim to identify the requirements that have to be fulfilled by the molecular system for strong ion-ligand interactions. Interestingly, our results indicate that aliphatic systems, such as cyclohexane, can interact as strong as aromatic ones with both cations and anions, despite of having a negligible quadrupole moment. In fact, cyclohexane binds anions stronger than benzene itself but slightly weaker that hexafluorobenzene. The NCI method reveals that the interaction between the ions and three C–H bonds of the saturated fragment are responsible for the surprisingly strong ion-σ interaction. A weakening of the ion-σ interactions is observed in the order: Li + > F − > Na + > Cl − > Br − ≈ K + . In addition, a complete Ziegler–Rauk type energy decomposition analysis has been carried out in order to reveal the origins of the thermodynamic driving force for complex formations. The electron density deformation upon complex formation has been scrutinized with a complementary NOCV analysis allowing the identification of molecular orbital interaction contributions to the stabilization. Based on these analysis, it is shown that the formally anion-π interaction is rather an anion-σ ∗ interaction.

Metal and ligand-based reductions have been modeled in octahedral ruthenium complexes revealing metal–ligand interactions as the profound driving force for the redox-active behaviour of orthoquinoid-type ligands. Through an extensive investigation of redox-active ligands we revealed the most critical factors that facilitate or suppress redox-activity of ligands in metal complexes, from which basic rules for designing non-innocent/redox-active ligands can be put forward. These rules also allow rational redox-leveling, i.e. the moderation of redox potentials of ligand-centred electron transfer processes, potentially leading to catalysts with low overpotential in multielectron activation processes.

Utilizing the bulky guanidinate ligand [LAr*]− (LAr* = (Ar*N)2C(R), Ar* = 2,6-bis(diphenylmethyl)-4-tert-butylphenyl, R = NCtBu2) for kinetic stabilization, the synthesis of a rare terminal Fe(IV) nitride complex is reported. UV irradiation of a pyridine solution of the Fe(II) azide [LAr*]FeN3(py) (3-py) at 0 °C cleanly generates the Fe(IV) nitride [LAr*]FeN(py) (1). The 15N NMR spectrum of the 115N (50% Fe≡15N) isotopomer shows a resonance at 1016 ppm (vs externally referenced CH3NO2 at 380 ppm), comparable to that known for other terminal iron nitrides. Notably, the computed structure of 1 reveals an iron center with distorted tetrahedral geometry, τ4 = 0.72, featuring a short Fe≡N bond (1.52 Å). Inspection of the frontier orbital ordering of 1 shows a relatively small HOMO/LUMO gap with the LUMO comprised by Fe(dxz,yz)N(px,y) π*-orbitals, a splitting that is manifested in the electronic absorption spectrum of 1 (λ = 610 nm, ε = 1375 L·mol–1·cm–1; λ = 613 nm (calcd)). Complex 1 persists in low-temperature solutions of pyridine but becomes unstable at room temperature, gradually converting to the Fe(II) hydrazide product [κ2-(tBu2CN)C(η6-NAr*)(N-NAr*)]Fe (4) upon standing via intramolecular N-atom insertion. This reactivity of the Fe≡N moiety was assessed through molecular orbital analysis, which suggests electrophilic character at the nitride functionality. Accordingly, treatment of 1 with the nucleophiles PMe2Ph and Ar–N≡C (Ar = 2,6-dimethylphenyl) leads to partial N-atom transfer and formation of the Fe(II) addition products [LAr*]Fe(N═PMe2Ph)(py) (5) and [LAr*]Fe(N═C═NAr)(py) (6). Similarly, 1 reacts with PhSiH3 to give [LAr*]Fe[N(H)(SiH2Ph)](py) (7) which Fukui analysis shows to proceed via electrophilic insertion of the nitride into the Si–H bond.

The bonding in heavier Group 14 zero-valent complexes of a general formula L2 E (E=Si-Pb; L=phosphine, N-heterocyclic and acyclic carbene, cyclic tetrylene and carbon monoxide) is probed by combining valence bond (VB) theory and maximum probability domain (MPD) approaches. All studied complexes are initially evaluated on the basis of the structural parameters and the shape of frontier orbitals revealing a bent structural motif and the presence of two lone pairs at the central E atom. For the VB calculations three resonance structures are suggested, representing the "ylidone", "ylidene" and "bent allene" structures, respectively. The influence of both ligands and central atoms on the bonding situation is clearly expressed in different weights of the resonance structures for the particular complexes. In general, the bonding in the studied E0 compounds, the tetrylones, is best described as a resonating combination of "ylidone" and "ylidene" structures with a minor contribution of the "bent allene" structure. Moreover, the VB calculations allow for a straightforward assessment of the π-backbonding (E→L) stabilization energy. The validity of the suggested resonance model is further confirmed by the complementary MPD calculations focusing on the E lone pair region as well as the E-L bonding region. Likewise, the MPD method reveals a strong influence of the σ-donating and π-accepting properties of the ligand. In particular, either one single domain or two symmetrical domains are found in the lone pair region of the central atom, supporting the predominance of either the "ylidene" or "ylidone" structures having one or two lone pairs at the central atom, respectively. Furthermore, the calculated average populations in the lone pair MPDs correlate very well with the natural bond orbital (NBO) populations, and can be related to the average number of electrons that is backdonated to the ligands.

In this study, an intuitive concept is derived, which explains the characteristic dependence of spin-state energetics on the exact exchange admixture of DFT functionals in the case of octahedral transition metal complexes. The change in electron density distributions upon varying the admixture, c 3, in the B3LYP functional is analyzed for archetype ionic and covalent systems as well as for the Fe 2+ ion in an ideal octahedral field. An understanding of how the DFT description of the electronic structure of octahedral complexes changes as a function of c 3 is sought. A systematic spin-state energy analysis of 50 octahedral complexes of various metals and ligands with consistent experimental data is presented, allowing the derivation, in theory, of an optimal c 3 value for each system. The notion that the admixture dependence of DFT spin-state energetics stems from the treatment of nondynamic electrons arising from the mixing of (M–L z2) 0(d z2) 2 and (M–L x2-y2 0(d( x2-y2)) 2 configurations into the dominant (M–L x2-y2) 2(d x2-y2) 0 and (M–L x2-y2) 2(d x2-y2) 0 ones in the low(er) spin states is put forward. That is, in the effort to mimic such electron–electron interactions, E x LDA overestimates, whereas exact exchange downplays the contribution of this type of electron correlation to the stability of low(er) spin states, leading to the widespread practical observation that the higher the exact exchange admixture, the more stable the high-spin-state configuration.

International audience; Periodic DFT-D calculations are used to decipher the role of intermolecular forces on the stability of mixed linear thiol self-assembled monolayers (SAMs) on Au(111) and compared with experiment. The interaction energy is rationalized by quantifying its different contributions. The inter-chain interaction energy is shown to be in direct relation with the surface reconstruction and the formation of adatoms. The stability of the mixed SAM systems is predicted by calculations and validated with experiments. In order to describe predictively the segregation of binary thiol mixtures adsorption on Au surfaces a segregation descriptor is defined. This procedure is a promising step forward in the prediction of segregated SAMs leading to future functional nanomaterials, including Janus or patchy nanoparticles for optics, formulation and self-assembled patterns.

International audience

The chalcogen bond has been acknowledged as an influential noncovalent interaction (NCI) between an electron-deficient chalcogen (donor) and a Lewis base (acceptor). This work explores the main features of chalcogen bonding through a large-scale computational study on a series of donors and acceptors spanning a wide range in strength and character of this type of bond: (benzo)chalcogenadiazoles (with Ch = Te/Se/S) versus halides and neutral Lewis bases with O, N, and C as donor atoms. We start from Pearson's hard and soft acids and bases (HSAB) principle, where the hard nature of the chalcogen bond is quantified through the molecular electrostatic potential and the soft nature through the Fukui function. The σ-holes are more pronounced when going down in the periodic table and their directionality matches the structural orientation of donors and acceptors in the complexes. The Fukui functions point toward an n→σ*-type interaction. The initial conjectures are further scrutinized using quantum mechanical methods, mostly relating to the systems' electron density. A Ziegler–Rauk energy decomposition analysis shows that electrostatics plays a distinctly larger role for the soft halides than for the hard, uncharged acceptors, associated with the softness matching within the HSAB principle. The natural orbital for chemical valence analysis confirms the n→σ* electron donation mechanism. Finally, the electron density and local density energy at the bond critical point in the quantum theory of atoms in molecules study and the position of the spikes in the reduced density gradient versus density plot in the NCI theory situate the chalcogen bond in the same range as strong hydrogen bonds. © 2017 Wiley Periodicals, Inc.

International audience; G protein-coupled receptors (GPCRs) play an important role in many cellular responses; as such, their mechanism of action is of utmost interest. To gain insight into the active conformation of GPCRs, the X-ray crystal structures of nanobody (Nb)-stabilized β2 -adrenergic receptor (β2 AR) have been reported. Nb80, in particular, is able to bind the intracellular G protein binding site of β2 AR and stabilize the receptor in an active conformation. Within Nb80, the complementarity-determining region 3 (CDR3) is responsible for most of the binding interactions. Hence, we hypothesized that peptidomimetics of the CDR3 loop might be sufficient for binding to the receptor, inhibiting the interaction of β2 AR with intracellular GPCR interacting proteins (e.g., G proteins). Based on previous crystallographic data, a set of peptidomimetics were synthesized that, similar to the Nb80 CDR3 loop, adopt a β-hairpin conformation. Syntheses, conformational analysis, binding and functional in vitro assays, as well as internalization experiments, were performed. We demonstrate that peptidomimetics can structurally mimic the CDR3 loop of a nanobody and its function by inhibiting G protein coupling as measured by partial inhibition of cAMP production.

Even though the concept of aromaticity and antiaromaticity is extremely important and widely used, there still exist lots of controversies in the literature, which are believed to be originated from the fact that there are so many aromatic types discovered and at the same time there are many aromaticity indexes proposed. In this work, using seven series of substituted fulvene derivatives as an example and with the information-theoretic approach in density functional reactivity theory, we examine these concepts from a different perspective. We investigate the changing patterns of Shannon entropy, Fisher information, Ghosh–Berkowitz–Parr entropy, information gain, Onicescu information energy, and relative Renyi entropy on the ring carbon atoms of these systems. Meanwhile, we also consider variation trends of four representative kinds of aromaticity indexes such as FLU, HOMA, ASE and NICS. Statistical analyses among these quantities show that with the same ring structure of the derivatives, both information-theoretic quantities and aromaticity indexes obey the same changing pattern, which are valid across all seven systems studied. However, cross correlations between these two sets of quantities yield two completely opposite patterns. These ring-structure dependent correlations are in good agreement with Hückel's 4n + 2 rule of aromaticity and 4n rule of antiaromaticity. Our results should provide a novel and complementary viewpoint on how aromaticity and antiaromaticity should be appreciated and categorized. More studies are in progress to further our understanding about the matter.

In this work we present the synthesis, spectroscopic and nonlinear optical properties of push-pull type organic dyes based on 1-phenyl-2-pyrazoline or 4-(dimethylamino)phenyl chromophores as a donor part, and bridged by a double bound ortho- or meta- substituted nitrophenyl group as an acceptor. For the optical measurements we have used the poly(methyl methacrylate) based thin films doped with the dyes. Third harmonic generation measurements were performed under the picosecond laser regime with excitation wavelength at 1064 nm. The experimental results confirmed that investigated systems can be used as the efficient nonlinear optical systems for harmonic of light generation (tripled but also doubled frequency). It has also been proved the strong dependence between chemical structure (position of electron-acceptor moiety as well as the type of electron-donor unit) and nonlinear optical (NLO) response coming from series of isomers and derivatives.

The structure and morphology of three polymer/graphene nanocomposites have been studied using classical molecular dynamics (MD) simulations. The simulations use 10-monomer oligomeric chains of three polymers: polyethylene (PE), polystyrene (PS) and polyvinylidene fluoride (PVDF). The structure of the polymer chains at the graphene surface has been investigated and characterized by pair correlation functions (PCF), g(r), g(θ) and g(r,θ). In addition, the influence of the temperature on the graphene/polymer interactions has been analysed for each of the three polymer/graphene nanocomposite systems. The results indicate that graphene induces order in both the PE and PVDF systems by providing a nucleation site for crystallisation, steering the growth of oligomer crystals according to the orientation of the graphene sheet, whereas the PS system remains disordered in the presence of graphene. The overall results are in line with the findings in a recent quantumchemical study by some of the present authors.

A set of neutral and ionic ruthenium arene trichlorostannyl complexes are reported herein. The tin(II) compounds L 1SnCl {1; L 1 = [2-(CH 2NEt 2)-4,6-(tBu) 2C 6H 2] –} and [L 2SnCl][SnCl 3] {2; L 2 = 2,6-[(CH 3)C=N(C 6H 3-2,6-iPr 2) 2]C 5H 3N} showed a rather different reactivity towards the ruthenium complex [(η 6-cymene)RuCl] 2(η-Cl) 2. As a consequence, the neutral complex [Ru(η 6-cymene)(L 1SnCl)Cl 2] (4) and the ionic compound [L 2SnCl][Ru(η 6-cymene)(SnCl 3) 2Cl] (8) were isolated. The insertion reaction of 4 with SnCl 2 provided the neutral trimetallic ruthenium complex [Ru(η 6-cymene)(L 1SnCl)(SnCl 3)Cl] (6). Analogous ruthenium complexes [Ru(η 6-cymene)(L 3PPh 2)Cl 2] (5) and [Ru(η 6-cymene)(L 3PPh 2)(SnCl 3)Cl] (7) containing the phosphane ligand L 3PPh 2 {3; L 3 = [2,6-iPr 2-(C 6H 3)NH] –} were also prepared to evaluate the donor–acceptor strength of the tin(II)- and phosphorus-containing ligands. The structural characterization and DFT calculations of the above-mentioned complexes suggest a strong influence of the [SnCl 3] – moiety on the Ru–E interaction (E = Sn, P). The influence of the trichlorostannyl ligand on the Ru–E interaction in the complexes 4–7 was further evaluated by means of a distortion/interaction analysis.

Functionalized diamondoids show great potential as building blocks for various new optoelectronic applications. However, until now, only simple mono and double substitutions were investigated. In this work, we considered up to 10 and 6 sites for functionalization of the two smallest diamondoids, adamantane and diamantane, respectively, in search for diamondoid derivatives with a minimal and maximal HOMO-LUMO energy gap. To this end, the energy gap was optimized systematically using an inverse molecular design methodology based on the best-first search algorithm combined with a Monte Carlo component to escape local optima. Adamantane derivatives were found with HOMO-LUMO gaps ranging from 2.42 to 10.63 eV, with 9.45 eV being the energy gap of pure adamantane. For diamantane, similar values were obtained. The structures with the lowest HOMO-LUMO gaps showed apparent push-pull character. The push character is mainly formed by sulfur or nitrogen dopants and thiol groups, whereas the pull character is predominantly determined by the presence of electron-withdrawing nitro or carbonyl groups assisted by amino and hydroxyl groups via the formation of intramolecular hydrogen bonds. In contrast, maximal HOMO-LUMO gaps were obtained by introducing numerous electronegative groups.

The activation of N-methyl-D-aspartate receptors is found to be intimately associated with neurodegenerative diseases which make them promising therapeutic targets. Despite the significantly increasing multidisciplinary interests centred on this ionotropic channel, design of new ligands with intended functional activity remains a great challenge. In this article, a computational study based on density functional theory is presented to understand the structural factors of ligands determining their function as antagonists and partial agonists. With this aim, the GluN1 subunit is chosen as being one of the essential components in the activation mechanism, and quantum chemical calculations are implemented for 30 antagonists and 30 partial agonists known to bind to this subunit with different binding affinities. Several quantum chemical descriptors are investigated which might unlock the difference between antagonists and partial agonists.

In this work, electrical currents through nanographenes, a class of alternant hydrocarbons also known as polycyclic aromatic hydrocarbons, in molecular junctions under small bias are explored. We illustrate that when the π-current dominates, that is, when no quantum interference takes place, the current prefers the direction of the shortest bond (the bond with the highest double bond character) upon entering the molecule from the contacts. As such, the idea of electrons propagating through double bonds from contact to contact, originating from the curly arrow drawings used in a previously established selection rule for transmission, seems to be more deeply rooted in the actual physical process of electron transport than previously anticipated. Furthermore, this work confirms that the σ-current behaves completely differently than the π-current. When this type of current becomes important, that is, when quantum interference takes place, the current generally prefers the shortest path from contact to contact, irrespective of the length of the bonds constituting this path, in accordance with the strong distance dependency of the σ-current. Finally, it is demonstrated that keto groups (and cross-conjugating groups in general) can be used to seal off parts of the molecule for the current. No current flows through the sealed off part of the molecule under small bias and it does not influence the transmission spectrum of the considered system.

Dehydroascorbate reductase (DHAR) catalyzes the glutathione (GSH)-dependent reduction of dehydroascorbate and plays a direct role in regenerating ascorbic acid, an essential plant antioxidant vital for defense against oxidative stress. DHAR enzymes bear close structural homology to the glutathione transferase (GST) superfamily of enzymes and contain the same active site motif, but most GSTs do not exhibit DHAR activity. The presence of a cysteine at the active site is essential for the catalytic functioning of DHAR, as mutation of this cysteine abolishes the activity. Here we present the crystal structure of DHAR2 from Arabidopsis thaliana with GSH bound to the catalytic cysteine. This structure reveals localized conformational differences around the active site which distinguishes the GSH-bound DHAR2 structure from that of DHAR1. We also unraveled the enzymatic step in which DHAR releases oxidized glutathione (GSSG). To consolidate our structural and kinetic findings, we investigated potential conformational flexibility in DHAR2 by normal mode analysis and found that subdomain mobility could be linked to GSH binding or GSSG release.

International audience; In the context of copper corrosion passivation, the adsorption of benzotriazole (BTAH) and its derivatives: 5-Methyl, 5-Amine, 1-Amine, 1-Methyl on a Cu(111) surface was investigated using periodic density functional (DFT) calculations. The results were contrasted with experimental ASTM protocols. Adsorption of BTAH and radical (BTA●) forms, as well as solvent effect were evaluated. The Cu-N interaction provides stable complexes with adsorption over top sites. Radical forms yielded more stable complex. Their adsorption energies correlate with the substituent position and electronic features. And finally, a strong interaction was obtained when the charge transfer goes from surface to adsorbate.

International audience; Nanophase segregation of a bi-component thiol self-assembled monolayer is predicted using atomistic molecular dynamics simulations and experimentally confirmed. The simulations suggest the formation of domains rich in acid-terminated chains, on one hand, and of domains rich in amide-functionalized ethylene glycol oligomers, on the other hand. In particular, within the amide-ethylene glycol oligomers region, a key role is played by the formation of inter-chain hydrogen bonds. The predicted phase segregation is experimentally confirmed by the synthesis of 35 and 15 nm gold nanoparticles functionalized with several binary mixtures of ligands. An extensive study by transmission electron microscopy and electron tomography, using silica selective heterogeneous nucleation on acid-rich domains to provide electron contrast, supports simulations and highlights patchy nanoparticles with a trend towards Janus nano-objects depending on the nature of the ligands and the particle size. These results validate our computational platform as an effective tool to predict nanophase separation in organic mixtures on a surface and drive further exploration of advanced nanoparticle functionalization.

To further rationalize the competition between halogen and hydrogen bonding, a combined experimental and theoretical study on the weakly bound molecular complexes formed between the combined halogen bond / hydrogen bond donor fluoroiodomethane and the Lewis bases dimethyl ether and trimethylamine (in standard and fully deuterated form) is presented. The experimental data are obtained by recording infrared and Raman spectra of mixtures of the compounds in liquid krypton, at temperatures between 120 K and 156 K. The experiments are supported by ab initio calculations at the MP2/aug-cc-pVDZ-PP level, statistical thermodynamics and Monte Carlo Free Energy Perturbation calculations. For the mixtures containing fluoroiodomethane and dimethyl ether a hydrogen bonded complex with an experimental complexation enthalpy of -7.0(2) kJ mol-1 is firmly identified. In contrast, only a single weak spectral feature is observed that can be tentatively assigned to the halogen bonded complex. For the mixtures involving trimethylamine, both halogen and hydrogen bonded complexes are observed, the experimental complexation enthalpies being -12.5(1) and -9.6(2) kJ mol-1 respectively. To evaluate the influence of fluorination on the competition between halogen and hydrogen bonding, the results obtained for fluoroiodomethane are compared with those of a previous study involving difluoroiodomethane.

The first structural elucidation of the first group 4 transition metal P2 complex, namely [(nacnac)Ti(OAr)]2(μ2:η2,η2-P2) (1), is reported. Complex 1 is formed via reductive decarbonylation of the phosphaethynolate ion -[OCP], which serves as a P atom source. The rhombic Ti2P2 core is essentially planar with short bond lengths suggesting some degree of multiple bonding character between the Ti-P and P-P sites. Also observed in 1 was the rather downfield shifted 31P NMR spectroscopic signal, appearing as a broadened resonance (Δν1/2 ~ 4034 Hz) at 907 ppm. Computational studies of 1 provide an understanding of the Ti2P2 core as well as the origin of the highly downfield 31P NMR spectroscopic signal.

A series of tin(IV) guanidinates were prepared by a (4+1) oxidative cycloaddition of four 1,2-diones (3,5-di-tert-butyl-o-benzoquinone, 3,4,5,6-tetrachloro-1,2-benzoquinone, 9,10-phenanthrenedione, 1,2-diphenylethanedione) or by an oxidative addition of a C–Br bond (from 2-bromo-1,3-diphenylpropane-1,3-dione followed by rearrangement) and a Cl–Cl bond (Cl2 generated from (dichloro-λ3-iodanyl)benzene) with {pTol-NC[N(SiMe3)2]N-pTol}2Sn (1). The reactivity of five pentane-1,3-diones and dimethyl malonate with compound 1 was assessed on the basis of the effect of 1,3-diones on the reaction mechanism in comparison with 1,2-diones. In contrast with oxidation reactions observed for compounds containing conjugated C═O bonds, the reactions of the tin(II) guanidinate with 1,3-diones revealed a high ability for ligand substitution. All the tin compounds prepared were characterized, and ligand substitution reactions were monitored using 1H, 13C, and 119Sn NMR spectroscopy. The molecular structures of one tin(II) and five tin(IV) guanidinato complexes investigated were determined by X-ray diffraction. All tin(IV) compounds display six- or seven-coordination. The UV–vis absorption spectra were recorded and simulated by TDDFT methods in order to get insight into the origin of the nontypical colors of the target tin(IV) diolato-guanidinates and their keto-functionalized precursors.

The reactivity of bis(organoamino)phosphanes PhP(NHR)(NHR′) (1a–1c, in which R, R′ = tBu for 1a; tBu, Dip for 1b; and Ph for 1c; Dip = C6H3–2,6-iPr2) and tBuP(NHDip)2 (1d) with Me3Al was investigated. The reaction of 1a or 1b gave in the first step compounds [PhP(NHR)(NR′)]AlMe2 (in which R, R′ = tBu for 2a; tBu, Dip for 2b) as a result of methane elimination that upon heating underwent nitrogen-to-phosphorus hydrogen-atom migration under the formation of diiminophosphinates [Ph(H)P(NR)(NR′)]AlMe2 (in which R, R′ = tBu for 3a; tBu, Dip for 3b). In contrast, phosphane 1c showed a reversed reaction sequence that yielded an intermediate [Ph(H)P(NHPh)(=NPh)]AlMe3 (2c) first as a consequence of hydrogen-atom migration followed by the methane elimination and formation of diiminophosphinate [Ph(H)P(NPh)2]AlMe2 (3c). The partial deprotonation of 1a,b,d using one molar equivalent of nBuLi followed by the treatment with AlCl3 smoothly produced compounds [Ph(H)P(NR)(NR′)]AlCl2 (in which R, R′ = tBu for 4a; tBu, Dip for 4b) and [tBu(H)P(NDip)2]AlCl2 (4d), in which the hydrogen atom was again shifted from the nitrogen to the phosphorus atom. All studied compounds were characterized with the help of elemental analysis; 1H, 13C{1H}, 31P, and 31P{1H} NMR spectra; and in the case of 3c, 4a, 4b, and 4d by using single-crystal X-ray diffraction analysis. The phenomenon of the hydrogen-atom migration was subjected also to a theoretical survey with particular emphasis on the influence of the phosphane used.

Two mixed amido-azido tin(IV) species bearing either C,N-chelating or bulky amido ligands were prepared by the reaction of the corresponding stannylene (e.g., Sn[N(SiMe3)2]2 (1) or (LCN)2Sn (2, LCN = 2-(N,N-dimethylaminomethyl)phenyl)) with Me3SiN3. Both products of the oxidative addition, Sn[N(SiMe3)2]3N3 (3) and (LCN)2Sn[N(SiMe3)2]N3 (5), respectively, were fully characterized by both multinuclear NMR spectroscopy and XRD analysis. Heating of a mixture of 2 and Me3SiN3 up to 100 °C lead to the formation of a novel dimeric species (LCN)2Sn(μ-NSiMe3)2Sn(LCN)2 (4), where the two tin atoms are bridged by two NSiMe3 ligands, thus forming a four-membered diazadistannacycle. DFT calculations were also carried out to support the proposed reaction mechanisms.

We consider the problem of defining an appropriate local descriptor corresponding to an arbitrary global descriptor. Although it does not seem easy to rigorously and uniquely define local analogues of derived global descriptors (e.g., the electrophilicity) or the fundamental global descriptors associated with the canonical ensemble (e.g., the hardness), the local response of these global descriptors can be defined unambiguously. We look at the local response of the global electrophilicity and compare it to the conventional, ad hoc, definition of the local electrophilicity. The local response of global nucleofugality and electrofugality is also discussed.

Antagonists of the FimH adhesin, a protein almost universally present at the extremity of type-1 fimbriae expressed by Escherichia coli, have been abundantly in the spotlight as alternative treatments of urinary tract infections. The antagonists function as bacterial antiadhesives through highly specific α-d-mannose binding in a charged and polar pocket at the tip of the FimH lectin domain and by the stacking of alkyl or aromatic moieties substituted on the mannose with two tyrosine residues (Tyr48 and Tyr137) at the entrance of the mannose-binding pocket. Using high-resolution crystal data, interaction energies are calculated for the different observed aromatic stacking modes between the tyrosines and the antagonist. The dispersion component of the interaction energy correlates with the observed electron density. The quantum chemical reactivity descriptors local hardness and polarizability were successfully validated as prediction tools for ligand affinity in the tyrosine gate of FimH and therefore have potential for rapid drug screening.

International audience; Silica-supported chromium oxide systems are efficient catalysts for many important chemical processes. Despite many years of investigations, the structure of the surface Cr species is not unambiguously determined. In this work, comprehensive DFT investigations of the monomeric Cr(VI) oxide species on silica under dehydrated conditions are performed. A large number of advanced periodic and cluster models of the SiO2 surface, based on the beta-cristobalite structure and different amorphous structures, have been applied. The calculated relative energies of the rnonooxo and dioxo Cr(VI) species depend on their location on the surface and on the structure of the model. It is concluded that the dioxo Cr(VI) species are thermodynamically preferred, but the presence of the monoxo Cr(VI) species, being in minority, cannot be excluded. According to the vibrational frequency analysis, the asymmetric O=Cr=O stretching mode for the dioxo species and the Cr=O stretching mode for the monooxo species can overlap.

To rationalize the driving factors in the competition of halogen bonding and hydrogen bonding, the complexes of the combined halogen-/hydrogen-bond donor difluoroiodomethane with the Lewis bases trimethylphosphine, dimethyl sulfide and chloromethane are studied. For all Lewis bases,ab initiocalculations lead to halogen- and hydrogen-bonded complexes. Fourier transform–IR experiments involving solutions of mixtures of difluoroiodomethane with trimethylphosphine(-d9) or dimethyl sulfide(-d6) in liquid krypton confirm the coexistence of a halogen-bonded and hydrogen-bonded complex. Also for solutions containing chloromethane, evidence of the formation of binary associations is found, but no definitive assignment of the multiple complex bands could be made. Using van't Hoff plots, the experimental complexation enthalpies for the halogen- and hydrogen-bonded complex of difluoroiodomethane with trimethylphosphine are determined to be −15.4 (4) and −10.5 (3) kJ mol−1, respectively, while for the halogen- and hydrogen-bonded complexes with dimethyl sulfide, the values are −11.3 (5) and −7.7 (6) kJ mol−1, respectively. The experimental observation that for both trimethylphospine and dimethyl sulfide the halogen-bonded complex is more stable than the hydrogen-bonded complex supports the finding that softer Lewis bases tend to favor iodine halogen bonding over hydrogen bonding.

Electrophilic aromatic sulfonation of benzene with sulfur trioxide is studied with ab initio molecular dynamics simulations in gas phase, and in explicit noncomplexing (CCl3F) and complexing (CH3NO2) solvent models., Electrophilic aromatic sulfonation of benzene with sulfur trioxide is studied with ab initio molecular dynamics simulations in gas phase, and in explicit noncomplexing (CCl3F) and complexing (CH3NO2) solvent models. We investigate different possible reaction pathways, the number of SO3 molecules participating in the reaction, and the influence of the solvent. Our simulations confirm the existence of a low-energy concerted pathway with formation of a cyclic transition state with two SO3 molecules. Based on the simulation results, we propose a sequence of elementary reaction steps and a kinetic model compatible with experimental data. Furthermore, a new alternative reaction pathway is proposed in complexing solvent, involving two SO3 and one CH3NO2.