Polar coordinate representation of Hb(rc) versus (h2/8m)nabla2rhob(rc) at BCP in AIM analysis: classification and evaluation of weak to strong interactions

Extremely stable system of 1-haloselanyl-anthraquinones: experimental and theoretical investigations

Highly stable selanyl halides, 1-ATQSeX (X = I (1), Br (2) and Cl (3)), were prepared. The structures of 1, 2, 6 (1-ATQSeX: X = Me) and 7 (1-ATQBr) were determined. QC calculations were performed on 1-3, 4 (X = F), 5 (X = H), 6, 7 and 8 (X = SeATQ-1). The O⋯Se distances in 1-4 from the sum of the vdW radii of the atoms (Δr(Se, O1)) were less than -1 Å, in magnitude, which must be the driving force for the high stability. The O-*-Se interactions seem stronger in the order of 1 < 2 < 3 < 4. The intrinsic dynamic and static natures of O⋯Se and/or Se⋯X in 1-8 are elucidated by QTAIM dual functional analysis (QTAIM-DFA). The Se-*-I, Se-*-Br, Se-*-Cl and Se-*-F interactions in 1-4 are predicted to have the natures of covalent, TBP with CT, TBP with CT, and typical HB with covalency, respectively, whereas O-*-Ses in 1-4 are all predicted to have the nature of MC with CT. The Se-*-H, Se-*-CMe and Se-*-Se interactions in 5, 6 and 8 are all predicted to have the covalent nature, while O-*-Ses in 5, 6 and 8 are all predicted to have the nature of typical HB with no covalency. The E(2) values of 1-6 and 8 are calculated with NBO analysis, and correlate excellently with Δr(Se, O1), except for Se-*-F, for which E(2) is evaluated to be much larger. The E(2) values also correlate very well with Cii-1 for all Se-*-X in 1-4, although data from 5, 6 and 8 deviated from the correlation, where Cii is the diagonal element of the compliance (force) constant for the internal vibrations. The behaviour of the interactions is further examined based on the QTAIM-DFA parameters of θ and θp. The stabilizing effect is further confirmed by the calculations with the ν(CO) values analyzed carefully.

Solution Dynamics of Covalent Open-[60]Fullerene Dimers

The translational diffusivity of covalent open-[60]fullerene dimers in an organic solvent was found to be well describable by a prolate ellipsoid model while a monomeric open-[60]fullerene behaves like a sphere model. The water association dynamics were examined for two open-[60]fullerene dimers, showing a higher water affinity for the sp3-linked dimer relative to sp2-linked dimer owing to an effective orbital-orbital overlap identified by π(fullerene)→σ*(H2O) interactions as suggested by theoretical calculations.

Direct Through-Space Substituent-π Interactions in Noncovalent Arene-Fullerene Assemblies

The arene-arene interactions between electron-rich and deficient aromatics have been less understood. Herein, we focus on a [60]fullerene π-surface as an electron-deficient aromatics. Using a 1H signal of H2O@C60 as a magnetic probe, the presence of benzene-fullerene interactions was confirmed. To investigate substituent effects on the noncovalent arene-fullerene interactions, NMR titration experiments were carried out using an open-[60]fullerene and a series of substituted benzenes, i. e., PhX (X=NO2, CN, Cl, OMe, H, CH3, and NH2), demonstrating a 1 : 2 stoichiometry with a positive correlation between stabilization energies upon the first association (ΔG1) and Hammet constants (σm). The destabilization of the self-assembled structure for X=OMe with a σ-withdrawing nature clearly showed direct through-space substituent-π interactions describable by the Wheeler-Houk model while the second association was suggested to be considerably perturbed by the secondary effects.

Water Adsorption on π-Surfaces of Open-Fullerenes

Understanding the water adsorptive behavior of fullerenes is of particular importance for their material application in aqueous media. The conventional fullerenols usually provide complex physical pictures of water adsorption due to their uncontrollable hydroxylation degree and substitution pattern. Herein, we focus on poorly hydroxylated fullerenes with well-defined structures. The water adsorptive behavior was examined by synchrotron IR spectroscopy and computational studies. As a result, three types of IR bands were observed for adsorbed water. The population of the three states was considerably altered by the orientational difference of the hydroxy groups. Nevertheless, water adsorption could not occur for 9-fluorenol and catechol. This indicates that the Lewis acidic fullerene π-surface plays a prominent role in water adsorption, while the rather Lewis basic π-surface of 9-fluorenol is unable to attract much water at a boundary with humid air.

A Simple Manganese(I) Catalyst for the Efficient and Selective Hydrophosphination of Olefins with PH3, Primary, and Secondary Phosphanes

A tridentate ligand L with a P,NH,N donor motif was synthesized in few steps from commercially available precursors. Upon reaction with [MnBr(CO)5], an octahedral 18-electron complex [Mn(CO)3(L)]Br (1) is obtained in which L adopts a facial arrangement. After deprotonation of the NH group in the cationic complex unit, a neutral Mn(I) amido complex [Mn(CO)2(L-H)] (2) is formed under loss of CO. Rearrangement of L-H leads to a trigonal bipyramidal structure in which the P and N donor centers are in trans position. Further deprotonation of 2 results in a dep-blue anionic complex fragment [Mn(CO)2(L-2H)]- (3). DFT calculations and a QTAIM analysis show that the amido complex 2 contains a Mn-N bond with partial double bond character and 3 an aromatic MnN2C2 ring. The anion [Mn(CO)2(L-2H)]- reacts with Ph2PH to give a phosphido complex, which serves as phosphide transfer reagent to activated olefins. But the catalytic activity is low. However, the neutral amido complex 2 is an excellent catalyst and with loadings as low as 0.04 mol %, turn over frequencies of >40'000 h-1 can be achieved. Furthermore, secondary and primary alkyl phosphines as well as PH3 can be added in a catalytic hydrophosphination reaction to a wide range of activated olefins such as α,β-unsaturated aldehydes, ketones, esters, and nitriles. But also, vinyl pyridine and some styrene derivatives are converted into the corresponding phosphanes.

Impact of PVC microplastics in photodynamic inactivation of Staphylococcus aureus and MRSA

Photodynamic processes have found widespread application in therapies. These processes involve photosensitizers (PSs) that, when excited by specific light wavelengths and in the presence of molecular oxygen, generate reactive oxygen species (ROS), that target cells leading to inactivation. Photodynamic action has gained notable attention in environmental applications, particularly against pathogens and antibiotic-resistant bacteria (ARB) that pose a significant challenge to public health. However, environmental matrices frequently encompass additional contaminants and interferents, including microplastics (MPs), which are pollutants of current concern. Their presence in water and effluents has been extensively documented, highlighting their impact on conventional treatment methods, but this information remains scarce in the context of photodynamic inactivation (PDI) setups. Here, we described the effects of polyvinyl chloride (PVC) microparticles in PDI targeting Staphylococcus aureus and its methicillin-resistant strain (MRSA), using curcumin as a PS under blue light. The presence of PVC microparticles does not hinder ROS formation; however, depending on its concentration, it can impact bacterial inactivation. Our results underscore that PDI remains a potent method for reducing bacterial concentrations in water and wastewater containing ARB, even in highly contaminated scenarios with MPs.

Molecular CO2 Storage: State of a Single-Molecule Gas

CO2 evolution is one of the urgent global issues; meanwhile, understanding of sorptive/dynamic behavior is crucial to create next-generation encapsulant materials with stable sorbent processes. Herein, we showcase molecular CO2 storage constructed by a [60]fullerenol nanopocket. The CO2 density reaches 2.401 g/cm3 within the nanopore, showing strong intramolecular interactions, which induce nanoconfinement effects such as forbidden translation, restricted rotation, and perturbed vibration of CO2. We also disclosed an equation of state for a molecular CO2 gas, revealing a very low pressure of 3.14 rPa (1 rPa = 10-27 Pa) generated by the rotation/vibration at 300 K. Curiously enough, the CO2 capture enabled to modulate an external property of the encapulant material itself, i.e., association of the [60]fullerenol via intercage hydrogen-bonding.

Intrinsic dynamic and static natures of APn--X+--BPn σ(3c-4e) type interactions (APn = BPn = N, P, As and Sb; X = H, F, Cl, Br and I) in bicyclo[3.3.3] and bicyclo[4.4.4] systems and their behaviour, elucidated with QTAIM dual functional analysis

The intrinsic dynamic and static natures of APn--X+--BPn (APn = BPn: N, P, As and Sb; X = H, F, Cl, Br and I) in 1a+-8c+ were elucidated with the quantum theory of atoms-in-molecules dual functional analysis (QTAIM-DFA). Species 1a+-8c+ were formed by incorporating X+ between APn and BPn of APn(CH2CH2CH2)3BPn (1-4) and APn(CH2CH2CH2CH2)3BPn (5-8). The relative stabilities between the symmetric and nonsymmetric structures along with their transition states were investigated. Various natures from typical hydrogen bonds (t-HB) to classical covalent bonds were predicted for the APn-X/BPn-X interactions in APn--X+--BPn with QTAIM-DFA. The secondary interactions of H-H and X-C were also detected. The vdW to molecular complexes through charge transfer natures were predicted for them. Natural bond orbital analysis clarified that the CT terms were caused by not only n(APn)→ σ*(X-BPn) but also σ(APn-C)→σ*(X-BPn), σ(APn-C/BPn-C)→np(X+) and n(X)→ns(Pn+). The direction and magnitude of the p-character of n(APn) were the factors that determined the types of donor-acceptor interactions. Estimating the order of the interaction strengths was attempted. The σ(3c-4e) characters of APn--X+--BPn were also examined by analysing the charge distributions on APn--X+--BPn. These results would provide fundamentally important insight into designing molecules with high functionality containing X+ in symmetric and nonsymmetric structures.

Open-[60]fullerenols with water adsorbed both inside and outside

The water affinity on [60]fullerenols was found to be governed by surface electrostatic potential while water aggregation is initiated by the hydroxy groups attached on the carbon surface. The molecular water adsorption at the internal sphere caused a significnat inhibition of water adsorption at the external carbon surface.

Halogen Bonding and/or Covalent Bond: Analogy of 3c-4e N···I···X (X = Cl, Br, I, and N) Interactions in Neutral, Cationic, and Anionic Complexes

X-ray structural measurements and computational analysis demonstrated the similarity of the geometries and electronic structures of the X-I···N (X = Cl, Br, I, and N) bonding in strong halogen-bonded (HaB) complexes and in the anionic or cationic halonium ions. In particular, I···N bond lengths in the solid-state associations formed by strong HaB donors (e.g., I2, IBr, ICl, and N-iodosuccinimide) and acceptors (e.g., quinuclidine or pyridines) were in the same range of 2.3 ± 0.1 Å as those in the halonium ions [e.g., the bis(quinuclidine)iodonium cation or the 1,1'-iodanylbis(pyrrolidine-2,5-dione) anion]. In all cases, bond lengths were much closer to those of the N-I covalent bond than to the van der Waals separations of these atoms. The strong N···I bonding in the HaB complexes led to a substantial charge transfer, lengthening and weakening of the I···X bonds, and polarization of the HaB donors. As a result, the central iodine atoms in the strong HaB complexes bear partial positive charges akin to those in the halonium ions. The energies and Mayer bond orders for both N···I and I···X bonds in such associations are also comparable to those in the halonium ions. The similarity of the bonding in such complexes and in halonium ions was further supported by the analysis of electron densities and energies at bond critical (3, -1) points in the framework of the quantum theory of atoms in molecules and by the density overlap region indicator. Overall, all these data point out the analogy of the symmetric N···I···N bonding in the halonium ions and the asymmetric X···I···N bonding in the strong HaB complexes, as well as the weakly covalent character of these 3c-4e interactions.

On the nature of noble gas - metal bond in silver aggregates

The aim of this paper is to extend the study of the nature of the bond between noble gas to nano- and sub nanoscale silver aggregates. In the framework of DFT-PAW calculations implemented in the abinit package, we carried out a thorough investigation on the nature of the bond between the six noble gases NG (He, Ne, Ar, Kr, Xe and Rn) and numerous neutral silver aggregates Agn from the single atom Ag1 to the nanoparticle Ag147 using atoms-in-molecules (AIM) dual functional analysis,. We evaluated the impact of the silver aggregate size, the adsorption site and of the noble gas on the Ag-NG bond. Our study concluded on the favored adsorption of heavier noble gases (Kr, Xe and Rn) over that of lighter noble gases (He, Ne and Ar) on any aggregate size due to an enhanced chemical contribution in the bond. For these heavier noble gases, in accordance with studies carried out on surfaces, we noted their preferential adsorption on on-top sites rather than on hollow sites, which further evidences the chemical contribution to the bond. Moreover, the slight positive Bader charge on these heavier noble gases implies an electron transfer from the noble gas to the silver atom. Noble gas adsorption is favored on smaller, few-atom, two-dimensional clusters rather than on larger three-dimensional nanoparticles. Finally, we identified a universal power law with a unique exponent linking bond length and electronic density at the bond critical point for all aggregate sizes, noble gases and adsorption sites.

Dynamic and Static Nature of XH-∗-π and YX-∗-π (X = F, Cl, Br, and I; Y = X and F) in the Distorted π-System of Corannulene Elucidated with QTAIM Dual Functional Analysis

The dynamic and static nature of the XH-∗-π and YX-∗-π (X = F, Cl, Br, and I; Y = X and F) interactions in the distorted π-system of corannulene (π(C₂₀H₁₀)) is elucidated with a QTAIM dual functional analysis (QTAIM-DFA), where asterisks emphasize the presence of bond critical points (BCPs) on the interactions. The static and dynamic nature originates from the data of the fully optimized and perturbed structures, respectively, in QTAIM-DFA. On the convex side, H in F-H-∗-π(C₂₀H₁₀) and each X in Y-X-∗-π(C₂₀H₁₀) join to C of the central five-membered ring in π(C₂₀H₁₀) through a bond path (BP), while each H in X-H-∗-π(C₂₀H₁₀) does so to the midpoint of C=C in the central five-membered ring for X = Cl, Br, or I. On the concave side, each X in F-X-∗-π(C₂₀H₁₀) also joins to C of the central five-membered ring with a BP for X = H, Cl, Br, and I; however, the interactions in other adducts are more complex than those on the convex side. Both H and X in X-H-∗-π(C₂₀H₁₀) (X = Cl and Br) and both Fs in F-F-∗-π(C₂₀H₁₀) connect to the three C atoms in each central five-membered ring (with three BPs). Two, three, and five BPs were detected for the Cl-Cl, I-H, Br-Br, and I-I adducts, where some BPs do not stay on the central five-membered ring in π(C₂₀H₁₀). The interactions are predicted to have a vdW to CT-MC nature. The interactions on the concave side seem weaker than those on the convex side for X-H-∗-π(C₂₀H₁₀), whereas the inverse trend is observed for Y-X-∗-π(C₂₀H₁₀) as a whole. The nature of the interactions in the π(C₂₀H₁₀) adducts of the convex and concave sides is examined in more detail, employing the adducts with X-H and F-X placed on their molecular axis together with the π(C₂₄H₁₂) and π(C₆H₆) adducts.

Synthesis, structures and reactions of acylsulfenyl iodides with theoretical investigations

A series of acylsulfenyl iodides (RCOSI) were synthesized by the reactions of carbothioic acid group 11-16 element derivatives with iodine or N-iodosuccinimides in moderate to good yields. The structure of the PhCOSI was nearly square planar based on the X-ray analysis, where the C[double bond, length as m-dash]O⋯I distance (3.153(5) Å) was significantly shorter than the sum of the van der Waals radii of the atoms (Σr _vdW), indicating close contact within the molecule. The distances between an iodine atom and the neighbouring two iodine atoms were also less than Σr _vdW, perhaps due to the energy lowering effect of the interactions. The acylsulfenyl iodides readily reacted with alkenes and alkynes to give the expected addition products in moderate to good yields at approximately 0 °C. A new synthesis of acylated sulfines, sulfenamides and sulfenochalcogenides using acylsulfenyl iodides is also described. Theoretical calculations were performed on PhCOSI with the Sapporo-TZP(+1s1p) basis sets at the MP2 level, which perfectly reproduced the observed structures. Similar calculations were performed on the reactions, exemplified by those of MeCOSI and CH₂[double bond, length as m-dash]CH₂, together with those of MeSI and CH₂[double bond, length as m-dash]CH₂. Mechanisms for both reactions were proposed, which were very similar. The proposed mechanism for the former was understood based on that of the latter. For both mechanisms, the episulfuranes and episulfonium ions played an important role. The dynamic and static nature of the bonds in the COSI group of PhCOSI and MeCOSI were elucidated based on QTAIM dual functional analysis.

Inverse Versus Normal Behavior of Interactions, Elucidated Based on the Dynamic Nature with QTAIM Dual-Functional Analysis

In QTAIM dual-functional analysis, H_b(r_c) is plotted versus H_b(r_c) - V_b(r_c)/2 for the interactions, where H_b(r_c) and V_b(r_c) are the total electron energy densities and potential energy densities, respectively, at the bond critical points (BCPs) on the interactions in question. The plots are analyzed by the polar (R, θ) coordinate representation for the data from the fully optimized structures, while those from the perturbed structures around the fully optimized structures are analyzed by (θ_p, κ_p). θ_p corresponds to the tangent line of the plot, and κ_p is the curvature; θ and θ_p are measured from the y-axis and y-direction, respectively. The normal and inverse behavior of interactions is proposed for the cases of θ_p > θ and θ_p < θ, respectively. The origin and the mechanism for the behavior are elucidated. Interactions with θ_p < θ are typically found, although seldom for [F-I-∗-F]^-, [MeS-∗-TeMe]²⁺, [HS-∗-TeH]²⁺ and CF₃SO₂N-∗-IMe, where the asterisks emphasize the existence of BCPs in the interactions and where [Cl-Cl-∗-Cl]^- and CF₃SO₂N-∗-BrMe were employed as the reference of θ_p > θ. The inverse behavior of the interactions is demonstrated to arise when H_b(r_c) - V_b(r_c)/2 and when the corresponding G_b(r_c), the kinetic energy densities at BCPs, does not show normal behavior.

A computational study of the inclusion of β-cyclodextrin and nicotinic acid: DFT, DFT-D, NPA, NBO, QTAIM, and NCI-RDG studies

Forming complexes with cyclodextrins can protect nicotinic acid (vitamin B3) from premature metabolism and enhance the solubility and stability of this drug. In this work, the formation of the inclusion complex of the neutral form of nicotinic acid and β-cyclodextrin was achieved. The complex is modeled using PM3, PM6-D4H3, and PM7, by considering two orientations of the guest: A and B, one is from wide to narrow rim, and the second is from narrow to the wide rim, respectively. The global minima positions were re-optimized using three density function methods: MN-15, B3LYP, and PW6B95-D3 with polarized Pople basis set 6-31G(d) in gas and aqueous phase. Orientation A showed the minimum complexation energy where the carboxylic functional group of nicotinic acid is located on the primary hydroxyl rim of β-cyclodextrin and the pyridine ring is totally embedded in the cavity. To further our study on the nature of complexation and the interactions of this host-guest system, different calculations were done. The reactivity indices showed that orientation A is harder than B and more electrophilic; the charge transfer occurred from the host to the guest and was confirmed by the natural population analysis (NPA). The natural bond orbitals (NBO) reveal the delocalization of orbitals between the host and the guest, quantum theory of atoms in molecules (QTAIM) analysis, and non-covalent interaction (NCI) analysis based on a reduced density gradient (RDG) give a detailed description of the nature of interactions between the host and the guest such as the hydrogen bonding and van der Waals interaction, and confirmed the stability of the complex given by the orientation A.

Characterization of resonance structures in aromatic rings of benzene and its heavier-element analogues

We present the experimental visualization of the valence-electron-density distribution in benzene and its kinetically stabilized heavier-element analogues, i.e., 1,2-disilabenzene and 1,2-digermabenzene. The valence-electron-density-distribution (EDD) analysis on the 1,2-disila- and 1,2-digermabenzenes revealed that these contain incompletely delocalized π electrons on their cyclic conjugation systems, making them less aromatic compared to benzene. Based on the results of this EDD analysis in combination with anisotropy of the current-induced density (ACID) calculations, considerable contributions from the characteristic resonance structures of 1,2-disila- and 1,2-digermabenzenes with cleaved EE bonds can be expected.

Intrinsic Dynamic and Static Nature of π···π Interactions in Fused Benzene-Type Helicenes and Dimers, Elucidated with QTAIM Dual Functional Analysis

The intrinsic dynamic and static nature of the π···π interactions between the phenyl groups in proximity of helicenes 3–12 are elucidated with the quantum theory of atoms-in-molecules dual functional analysis (QTAIM-DFA). The π···π interactions appear in C-∗-C, H-∗-H, and C-∗-H, with the asterisks indicating the existence of bond critical points (BCPs) on the interactions. The interactions of 3–12 are all predicted to have a p-CS/vdW nature (vdW nature of the pure closed-shell interaction), except for ²C_bay-∗-⁷C_bay of 10, which has a p-CS/t-HB_nc nature (typical-HBs with no covalency). (See the text for definition of the numbers of C and the bay and cape areas). The natures of the interactions are similarly elucidated between the components of helicene dimers 6:6 and 7:7 with QTAIM-DFA, which have a p-CS/vdW nature. The characteristic electronic structures of helicenes are clarified through the natures predicted with QTAIM-DFA. Some bond paths (BPs) in helicenes appeared or disappeared, depending on the calculation methods. The static nature of C_cape-∗-C_cape is very similar to that of C_bay-∗-C_bay in 9–12, whereas the dynamic nature of C_cape-∗-C_cape appears to be very different from that of C_bay-∗-C_bay. The results will be a guide to design the helicene-containing materials of high functionality.

Chalcogen-bonded donor–acceptor complexes of 5,6-dicyano[1,2,5]selenadiazolo[3,4-b]pyrazine with halide ions

With halides X− (X = Cl, Br, I) 5,6-dicyano-[1,2,5]selenadiazolo[3,4-b]pyrazine 1 forms chalcogen-bonded complexes [1–X]− structurally defined by XRD. UV/Vis spectra of [1–X]− feature red-shifted charge-transfer bands in the Vis part.

Role of Basic Surface Groups of Activated Carbon in Chlordecone and β-Hexachlorocyclohexane Adsorption: A Molecular Modelling Study

The influence of nitrogen-containing surface groups (SGs) onto activated carbon (AC) over the adsorption of chlordecone (CLD) and β-hexachlorocyclohexane (β-HCH) was characterized by a molecular modelling study, considering pH (single protonated SGs) and hydration effect (up to three water molecules). The interactions of both pollutants with amines and pyridine as basic SGs of AC were studied, applying the multiple minima hypersurface (MMH) methodology and using PM7 semiempirical Hamiltonian. Representative structures from MMH were reoptimized using the M06-2X density functional theory. The quantum theory of atoms in molecules (QTAIM) was used to characterize the interaction types in order understanding the adsorption process. A favorable association of both pesticides with the amines and pyridine SGs onto AC was observed at all pH ranges, both in the absence and presence of water molecules. However, a greater association of both pollutants with the primary amine was found under an acidic pH condition. QTAIM results show that the interactions of CLD and β-HCH with the SGs onto AC are governed by Cl···C interactions of chlorine atoms of both pesticides with the graphitic surface. Electrostatic interactions (H-bonds) were observed when water molecules were added to the systems. A physisorption mechanism is suggested for CLD and β-HCH adsorption on nitrogen-containing SGs of AC.

Linear Multiselenium Interactions in Dicationic Oligomers of 1,5-(Diselena)canes: Behavior of Semc σ(mc c-ne e) (6≤mc ≤16) Elucidated with QTAIM Dual Functional Analysis

The intrinsic dynamic and static nature mc center-ne electron interactions of the σ-type σ(mc c-ne e) were elucidated for the Se-Se interactions in dicationic oligomers of Se(CH2 CH2 CH2 )2 Se (1 (Se, Se)) [n2+ (Se, Se): n=1-8], especially for mc ≥6, where n2+ (Se, Se: n=1-8) are abbreviated by n2+ (n=1-8), respectively. QTAIM dual functional analysis (QTAIM-DFA) was applied to the interactions. Perturbed structures generated using coordinates derived from the compliance constants (Cii ) were employed for QTAIM-DFA. Each Se-*-Se in 12+ and 22+ has the nature of CT-TBP (trigonal bipyramidal adduct formation through CT) and Cov-w (weak covalent), respectively, which supply the starting points of the investigations. The asterisk emphasizes the existence of a bond critical point on the interaction. All Se-*-Se in 32+ are classified by the regular closed shell (r-CS) interactions and characterized as CT-MC (molecular complex formation through CT), which are denoted as r-CS/CT-MC, except for the central interaction, of which nature is r-CS/CT-TBP. Most interactions in 42+ -82+ are r-CS/t-HBwc (typical-HB with covalency) but some are pure-CS/t-HBnc (t-HB with no covalency). The linear Se2n 2+ interactions in 22+ -82+ seem close to those without any limitations, since the nature of Se-*-Se inside and outside of (CH2 CH2 CH2 )2 are very similar with each other. The linear Se2n 2+ interactions in 32+ -82+ are shown to be analyzed as σ(mc c-ne e: 6≤mc ≤16), not by the accumulated σ(3c-4e).

Beyond Classical Coordination Chemistry: The First Case of a Triply Bridging Phosphine Ligand

The first example of a triply bridging (μ₃ -P) phosphine ligand has been discovered in the crown-shaped [Cu₃ (μ₂ -Hal)₃ L] (Hal=Cl, Br, or I) complexes supported by tris[2-(2-pyridyl)ethyl]phosphine (L). Theoretical analysis completely confirms the observed μ₃ -P-bridging pattern, revealing the interaction of the same lone pair of phosphorus with three valence 4s-orbitals of Cu atoms. The presented complexes exhibit outstanding blue phosphorescence (λ_em =442-465 nm) with the quantum efficiency reaching 100 %. The complex [Cu₃ (μ₂ -I)₃ L] also exhibits remarkable thermo- and mechanochromic luminescence resulting in a sharp change in the emission colour upon external stimuli. These findings essentially contribute to coordination chemistry of the pnictine ligands.

Intrinsic Dynamic and Static Nature of Halogen Bonding in Neutral Polybromine Clusters, with the Structural Feature Elucidated by QTAIM Dual-Functional Analysis and MO Calculations

The intrinsic dynamic and static nature of noncovalent Br-∗-Br interactions in neutral polybromine clusters is elucidated for Br4-Br12, applying QTAIM dual-functional analysis (QTAIM-DFA). The asterisk (∗) emphasizes the existence of the bond critical point (BCP) on the interaction in question. Data from the fully optimized structures correspond to the static nature of the interactions. The intrinsic dynamic nature originates from those of the perturbed structures generated using the coordinates derived from the compliance constants for the interactions and the fully optimized structures. The noncovalent Br-∗-Br interactions in the L-shaped clusters of the Cs symmetry are predicted to have the typical hydrogen bond nature without covalency, although the first ones in the sequences have the vdW nature. The L-shaped clusters are stabilized by the n(Br)→σ*(Br-Br) interactions. The compliance constants for the corresponding noncovalent interactions are strongly correlated to the E(2) values based on NBO. Indeed, the MO energies seem not to contribute to stabilizing Br4 (C2h) and Br4 (D2d), but the core potentials stabilize them, relative to the case of 2Br2; this is possibly due to the reduced nuclear-electron distances, on average, for the dimers.

Isolation and Structural Determination of a Hexacoordinated Antimony(V) Dication

The hexacoordinated antimony(V) dication [(ppy)₃ Sb]²⁺ ([1]²⁺ ; ppy=2-(2-pyridyl)phenyl), stabilized by three intramolecular donor-acceptor interactions, has been isolated as its hexachloroantimonate salt [1][SbCl₆ ]₂ , prepared by the oxidative addition of chlorine to the neutral stibine [(ppy)₃ Sb] (1), followed by the abstraction of chloride. Air-stable [1][SbCl₆ ]₂ exhibits remarkable thermal stability and the three ppy ligands on the antimony atom are shown to be magnetically inequivalent in the ¹ H and ¹³ C NMR spectra. A hexacoordinated, meridional octahedral bonding geometry has been determined for [1][SbCl₆ ]₂ by X-ray crystallographic analysis. Theoretical calculations were performed to investigate why the meridional form was generated preferentially over the facial form. In addition, the dynamics of the ppy ligands were investigated by variable-temperature ¹ H NMR spectroscopy. The potential to generate dications by using a single-electron-transfer reagent has also been investigated. The dication [1]²⁺ is the first [12-Sb-6]²⁺ chemical species to have been structurally determined.

A Sterically Hindered Derivative of 2,1,3-Benzotelluradiazole: A Way to the First Structurally Characterised Monomeric Tellurium-Nitrogen Radical Anion

Interaction of the tetradentate redox-active 6,6'-[1,2-phenylenebis(azanediyl)]bis(2,4-di-tert-butylphenol) (H₄ L) with TeCl₄ leads to neutral diamagnetic compound TeL (1) in high yield. The molecule of 1 has a nearly planar TeN₂ O₂ fragment, which suggests the formulation of 1 as Te^II L^2- , in agreement with the results of DFT calculations and QTAIM and NBO analyses. Reduction of 1 with one equivalent of [CoCp₂ ] leads to quantitative formation of the paramagnetic salt [CoCp₂ ]⁺ [1]^.- , which was characterised by single-crystal XRD. The solution EPR spectrum of [CoCp₂ ]⁺ [1]^.- at room temperature features a quintet due to splitting on two equivalent ¹⁴ N nuclei. Below 150 K it turns into a broad singlet line with two weak satellites due to the splitting on the ¹²⁵ Te nucleus. Two-component relativistic DFT calculations perfectly reproduce the a(¹⁴ N) HFI constants and A_∥ (¹²⁵ Te) value responsible for the low-temperature satellite splitting. Calculations predict that the additional electron in 1^.- is localised mainly on L, while the spin density is delocalised over the whole molecule with significant localisation on the Te atom (≥30 %). All these data suggest that 1^.- can be regarded as the first example of a structurally characterised monomeric tellurium-nitrogen radical anion.

Guest-host complexes of 1-iodochlordecone and β-1-iodo-pentachlorocyclohexane with cyclodextrins as radiotracers of organochlorine pesticides in polluted water

The chlordecone (CLD) and the β-hexachlorocyclohexane (β-HCH) are persistent organic pollutants with a great environmental stability that cause severe affectations to health. The concentration of these pesticides in the environment is low, which represent a problem for their determination, even for the modern analytical methods. The labeling of these compounds with an iodine radioisotope for their use as radiotracers is a potential solution to this problem. The present work studies the interaction of 1-iodochlordecone (I-CLD) and β-1-iodo-pentachlorocyclohexane (I-β-HCH) with cyclodextrins (CDs), during the formation of molecular inclusion complexes pesticide@CDs. The methodology of multiple minima hypersurfaces, quantic calculations based on density functional theory and a topologic study of electronic density were used to corroborate the stability of I-CLD@CDs and I-β-HCH@CDs complexes. Three main types of guest-host complexes in relation to the occlusion grade were observed: with total occlusion, with partial occlusion and external interaction without occlusion. The more stable complexes are obtained when the γ-CD is the host molecule. The formed complexes with radiolabelled pollutants are analogous with the ones reported in previous works. These results confirm the utility of these complexes for the removal of organochlorine pesticides from polluted water and, also, demonstrate the possibility of using the I-CLD and the I-β-HCH as possible radiotracers for these pollutants in further studies with environmental proposes.

Dynamic and Static Nature of Br4 σ(4c-6e) and Se2Br5 σ(7c-10e) in the Selenanthrene System and Related Species Elucidated by QTAIM Dual Functional Analysis with QC Calculations

The nature of Br4 σ(4c-6e) of the BBr-∗-ABr-∗-ABr-∗-BBr form is elucidated for SeC12H8(Br)SeBr---Br-Br---BrSe(Br)C12H8Se, the selenanthrene system, and the models with QTAIM dual functional analysis (QTAIM-DFA). Asterisks (∗) are employed to emphasize the existence of bond critical points on the interactions in question. Data from the fully optimized structure correspond to the static nature of interactions. In our treatment, data from the perturbed structures, around the fully optimized structure, are employed for the analysis, in addition to those from the fully optimized one, which represent the dynamic nature of interactions. The ABr-∗-ABr and ABr-∗-BBr interactions are predicted to have the CT-TBP (trigonal bipyramidal adduct formation through charge transfer) nature and the typical hydrogen bond nature, respectively. The nature of Se2Br5 σ(7c-10e) is also clarified typically, employing an anionic model of [Br-Se(C4H4Se)-Br---Br---Br-Se(C4H4Se)-Br]-, the 1,4-diselenin system, rather than (BrSeC12H8)Br---Se---Br-Br---Br-Se(C12H8Se)-Br, the selenanthrene system.

Intrinsic dynamic and static nature of each HB in the multi-HBs between nucleobase pairs and its behavior, elucidated with QTAIM dual functional analysis and QC calculations

The intrinsic dynamic and static nature of each HB in the multi-HBs between nucleobase pairs (Nu-Nu') is elucidated with QTAIM dual functional analysis (QTAIM-DFA). Perturbed structures generated using coordinates derived from the compliance constants (C ii ) are employed for QTAIM-DFA. The method is called CIV. Two, three, or four HBs are detected for Nu-Nu'. Each HB in Nu-Nu' is predicted to have the nature of CT-TBP (trigonal bipyramidal adduct formation through charge transfer (CT)), CT-MC (molecular complex formation through CT), or t-HBwc (typical HB with covalency), while the vdW nature is predicted for the C-H⋯X interactions, for example. Energies for the formation of the pairs (ΔE) are linearly correlated with the total values of C ii -1 in Nu-Nu'. The total C ii -1 values are obtained by summing each C ii -1 value, similarly to the case of Ohm's law for the parallel connection in the electric resistance. The total ΔE value for a nucleobase pair could be fractionalized to each HB, based on each C ii -1 value. The perturbed structures generated with CIV are very close to those generated with the partial optimization method, when the changes in the interaction distances are very small. The results provide useful insights for better understanding DNA processes, although they are highly enzymatic.

Nature of intramolecular O-H⋯π interactions as elucidated by QTAIM dual functional analysis with QC calculations

The intrinsic dynamic and static nature of intramolecular OH-*-π interactions is elucidated using a QTAIM dual functional analysis (QTAIM-DFA) after clarifying the structural features. Asterisks (*) are employed to emphasize the presence of bond critical points (BCPs) on the bond paths (BPs), which correspond to the interactions in question. Data from the fully optimized structures correspond to the static nature of the interactions. In our treatment, data from the perturbed structures, which are based around the fully optimized structure, are employed for the analysis in addition to those from the fully optimized structure, which represent the dynamic nature of the interaction. Seven intramolecular OH-*-C(π) interactions were detected in six-membered rings, with six BPs and BCPs for each, among the 72 conformers of the species examined here (1-15). The interactions are predicted to have a vdW or t-HBnc (typical hydrogen bonds with no covalency) nature, which appeared in the pure closed shell region. They appear to be stronger than the corresponding intermolecular interactions. Nine BPs with BCPs were also detected for the intramolecular O-*-X interactions (X = C(π) and H(π), joined to C(π)) in the 5-7-membered rings. The E(2) values of the interactions, as obtained by NBO, are discussed in relation to the stabilities of the conformers and the BPs with BCPs.

Nature of the E⋯E′ interactions (E, E′ = O, S, Se, and Te) at naphthalene 1,8-positions with fine details of the structures: experimental and theoretical investigations

The nature of E⋯E′ in 1-RE–8-R′E′C₁₀H₆ (E/E′ = O, S, Se and Te) is clarified with the QTAIM approach and NBO analysis, after structural determinations.

Evaluation of the molecular inclusion process of β-hexachlorocyclohexane in cyclodextrins

The present work aimed to study the guest–host complexes of β-hexachlorocyclohexane (β-HCH), a pesticide with high environmental stability that can cause severe health problems, with the most common cyclodextrins (α-, β-, and γ-CDs). The formation reactions of these molecular inclusion complexes were addressed in this research. The multiple minima hypersurface methodology, quantum calculations based on density functional theory and a topological exploration of the electron density based on the quantum theory of atoms in molecules approach were used to characterize the interaction spaces of the pollutant with the three CDs. Additionally, charge distribution, charge transfer and dual descriptor analyses were employed to elucidate the driving forces involved in the formation of these molecular inclusion complexes. Three types of fundamental interactions were observed: total occlusion, partial occlusion and external interaction (non-occlusion). Finally, experiments were performed to confirm the formation of the studied complexes. The most stable complexes were obtained when γ-CD was the host molecule. The interactions between the pesticide and CDs have fundamentally dispersive natures, as was confirmed experimentally by spectroscopic results. All the obtained results suggest the possibility of using CDs for the purification and treatment of water polluted with β-HCH.

The present work aimed to study the guest–host complexes of β-hexachlorocyclohexane (β-HCH), a pesticide with high environmental stability that can cause severe health problems, with the most common cyclodextrins (α-, β-, and γ-CDs).

The nature of G⋯E–Y σ(3c–4e) in o-MenGCH2C6H4EY (MenG = Me2N and MeE; E = O, S, Se and Te; Y = F, Cl, Br, EMe and Me) with contributions from CT and compliance constants in noncovalent G⋯E interactions

The intrinsic dynamic and static nature of G–*–E–*–Y σ(3c–4e) interactions was elucidated with the quantum theory of atoms in molecules dual functional analysis (QTAIM-DFA), employing o-Me_nGCH₂C₆H₄EY (Me_nG = Me₂N and MeE; E = O, S, Se and Te; Y = F, Cl, Br, I, EMe and Me). Asterisks (*) are employed to emphasize the existence of bond critical points (BCPs) on the bond paths (BPs), corresponding to the interactions in question. Data from the fully optimized structure correspond to the static nature of interactions. The dynamic nature is called the intrinsic dynamic nature if the perturbed structures are generated using the coordinates derived from the compliance constants. Basis sets of the Sapporo-TZP type with diffusion functions are employed for the heteroatoms at the MP2 level. The noncovalent G–*–E interactions in GEY σ(3c–4e) are predicted to demonstrate van der Waals bonding to CT-TBP (trigonal bipyramidal adduct formation through charge transfer) nature, while the E–*–Y bonds have the covalent nature. Some E–F bonds show strong ionic character when G–*–E is predicted to be stronger than E–*–Y. The contributions of the CT terms to the G–*–E interactions, evaluated with NBO, are discussed in relation to the predicted nature. The E(2) values based on NBO are strongly correlated to the compliance constants for the G–*–E interactions if suitably treated separately.

The nature of E⋯E′ in 1-RECH₂-2-R′E′C₆H₄ (E/E′ = O, S, Se and Te) is clarified with QTAIM approach and NBO analysis, after structural determinations.

M-S Multiple Bond in HMSH, H2MS, and HMS Molecules (M = B, Al, Ga): Matrix Infrared Spectra and Theoretical Calculations

Reaction products of B, Al, and Ga atoms with H₂S have been identified in solid argon using matrix isolation infrared absorption spectroscopy. The results show that the ground state B atom reaction with H₂S gives the H₂BS molecule while for the Al atom the HAlSH molecule forms first, which then further isomerizes to H₂AlS upon >500 nm irradiation. The reaction of the Ga atom with H₂S only takes place upon photolysis to produce HGaSH in the matrix. The assignments of the major modes for these products were confirmed by appropriate ¹⁰B, ¹¹B, D₂S, and H₂³⁴S isotopic shifts and theoretical frequency calculations. Topological analysis of the electron density suggests that both HBSH and H₂BS molecules possess covalent B-S bond with significant double bond character, while the M-S bond in the heavier group 13 homologues (Al, Ga) was characterized as a polar covalent strong interaction.

Intrinsic Dynamic Nature of Neutral Hydrogen Bonds Elucidated with QTAIM Dual Functional Analysis: Role of the Compliance Force Constants and QTAIM-DFA Parameters in Stability

The dynamic and static nature of various neutral hydrogen bonds (nHBs) is elucidated with quantum theory of atoms-in-molecules dual functional analysis (QTAIM-DFA). The perturbed structures generated by using the coordinates derived from the compliance force constants (Cij ) of internal vibrations are employed for QTAIM-DFA. The method is called CIV. The dynamic nature of CIV is described as the "intrinsic dynamic nature", as the coordinates are invariant to the choice of the coordinate system. nHBs are, for example, predicted to be van der Waals (H2Se-✶-HSeH; ✶=bond critical point), t-HBnc (typical-HBs with no covalency: HI-✶-HI), t-HBwc (t-HBs with covalency: H2C=O-✶-HI), CT-MC [molecular complex formation through charge transfer (CT): H2C=O-✶-HF], and CT-TBP (trigonal bipyramidal adduct formation through CT: H3N-✶-HI) in nature. The results with CIV were the same as those with POM in the calculation errors, for which the perturbed structures were generated by partial optimization, and the interaction distances in question were fixed suitably in POM. The highly excellent applicability of CIV for QTAIM-DFA was demonstrated for the various nHBs, as well as for the standard interactions previously reported. The stability of the HBs, evaluated by ΔE, is well correlated with Cij (ΔE×Cij =constant value of -165.64), and the QTAIM parameters, although a few deviations were detected.

Behaviour of the XH-*-π and YX-*-π interactions (X, Y = F, Cl, Br and I) in the coronene π-system, as elucidated by QTAIM dual functional analysis with QC calculations

The dynamic and static nature of XH-*-π and YX-*-π in the coronene π-system (π(C24H12)) is elucidated by QTAIM dual functional analysis, where * emphasizes the presence of bond critical points (BCPs) in the interactions. The nature of the interactions is elucidated by analysing the plots of the total electron energy densities H b(r c) versus H b(r c) - V b(r c)/2 [=(ħ 2/8m)∇2 ρ b(r c)] for the interactions at BCPs, where V b(r c) are the potential energy densities at the BCPs. The data for the perturbed structures around the fully optimized structures are employed for the plots in addition to those of the fully optimized structures. The plots are analysed using the polar coordinate of (R, θ) for the data of the fully optimized structures, while those containing the perturbed structures are analysed using (θ p, κ p), where θ p corresponds to the tangent line of each plot and κ p is the curvature. Whereas (R, θ) show the static nature, (θ p, κ p) represent the dynamic nature of the interactions. All interactions in X-H-*-π(C24H12) (X = F, Cl, Br and I) and Y-X-*-π(C24H12) (Y-X = F-F, Cl-Cl, Br-Br, I-I, F-Cl, F-Br and F-I) are classified by pure CS (closed shell) interactions and are characterized as having the vdW nature, except for X-H = F-H and Y-X = F-Cl, F-Br and F-I, which show the typical-HB nature without covalency. The structural features of the complexes are also discussed.

High-resolution X-ray diffraction determination of the electron density of 1-(8-PhSC10H6)SS(C10H6SPh-8')-1' with the QTAIM approach: evidence for S4 σ(4c-6e) at the naphthalene peri-positions

An extended hypervalent S4 σ(4c-6e) system was confirmed for the linear BS-∗-AS-∗-AS-∗-BS interaction in 1-(8-PhBSC10H6)AS-AS(C10H6 BSPh-8')-1' (1) via high-resolution X-ray diffraction determination of electron densities. The presence of bond critical points (BCPs; ∗) on the bond paths confirms the nature and extent of this interaction. The recently developed QTAIM dual functional analysis (QTAIM-DFA) approach was also applied to elucidate the nature of the interaction. Total electron energy densities H b( r c) were plotted versus H b( r c) - V b( r c)/2 for the interaction at the BCPs, where V b( r c) represents the potential energy densities at the BCP. The results indicate that although the data for an interaction in the fully optimized structure corresponds to a static nature, the data obtained for the perturbed structures around it represent the dynamic nature of the interaction in QTAIM-DFA. The former classifies the interaction and the latter characterises it. Although AS-∗-AS in 1 is classified by a shared shell interaction and exhibits weak covalent character, AS-∗-BS is characterized as having typical hydrogen-bond nature with covalent properties in the region of the regular closed shell interactions. The experimental results are supported by matching theoretical calculations throughout, particularly for the extended hypervalent E4 σ(4c-6e) (E = S) interaction.

Behavior of the E-E' Bonds (E, E' = S and Se) in Glutathione Disulfide and Derivatives Elucidated by Quantum Chemical Calculations with the Quantum Theory of Atoms-in-Molecules Approach

The nature of the E–E’ bonds (E, E’ = S and Se) in glutathione disulfide (1) and derivatives 2–3, respectively, was elucidated by applying quantum theory of atoms-in-molecules (QTAIM) dual functional analysis (QTAIM-DFA), to clarify the basic contribution of E–E’ in the biological redox process, such as the glutathione peroxidase process. Five most stable conformers a–e were obtained, after applying the Monte-Carlo method then structural optimizations. In QTAIM-DFA, total electron energy densities H_b(r_c) are plotted versus H_b(r_c) − V_b(r_c)/2 at bond critical points (BCPs), where V_b(r_c) are potential energy densities at BCPs. Data from the fully optimized structures correspond to the static nature. Those containing perturbed structures around the fully optimized one in the plot represent the dynamic nature of interactions. The behavior of E–E’ was examined carefully. Whereas E–E’ in 1a–3e were all predicted to have the weak covalent nature of the shared shell interactions, two different types of S–S were detected in 1, depending on the conformational properties. Contributions from the intramolecular non-covalent interactions to stabilize the conformers were evaluated. An inverse relationship was observed between the stability of a conformer and the strength of E–E’ in the conformer, of which reason was discussed.