Waro Nakanishi

Transannular E···E' Interactions in Neutral, Radical Cationic, and Dicationic Forms of cyclo-[E(CH2CH2CH2)2E'] (E, E' = S, Se, Te, and O) with Structural Feature: Dynamic and Static Behavior of E···E' Elucidated by QTAIM Dual Functional Analysis.

The nature of the transannular E-∗-E interactions in neutral, radical cationic, and dicationic forms of cyclo-E(CH2CH2CH2)2E (1) (E, E = S, Se, Te, and O) (1, 1(•+), and 1(2+), respectively) is elucidated by applying QTAIM dual functional analysis (QTAIM-DFA). Hb(rc) are plotted versus Hb(rc) - Vb(rc)/2 for the data of E-∗-E at BCPs in QTAIM-DFA, where ∗ emphasizes the existence of BCP. Plots for the fully optimized structures are analyzed by the polar coordinate (R, θ) representation. Those containing the perturbed structures are by (θp, κp): θp corresponds to the tangent line of the plot, and κp is the curvature. While (R, θ) describes the static nature, (θp, κp) represents the dynamic nature of interactions. The nature is well-specified by (R, θ) and (θp, κp). E-∗-E becomes stronger in the order of 1 < 1(•+) < 1(2+), except for O-∗-O. While E-∗-E (E, E = S, Se, and Te) in 1(2+) are characterized as weak covalent bonds, except for S-∗-Te (MC nature through CT) and Se-∗-Te (TBP nature through CT), O-∗-E seems more complex. The behavior of E-∗-E in 1(2+) is very close to that of cyclo-E(CH2CH2CH2)E (E, E = S, Se, Te, and O), except for O-∗-O.

Quantum chemical calculations with the AIM approach applied to the π-interactions between hydrogen chalcogenides and naphthalene

The nature of the π–interactions in the 1u2006:u20061 and 2u2006:u20061 adducts of EH2 with the naphthalene π-system (E = O, S, Se and/or Te) is elucidated by applying QTAIM-DFA (QTAIM dual functional analysis). The H–*–π interactions are detected in EH2–*–π(C10H8) and (EH2)2–*–π(C10H8) for E = S, Se and Te, whereas E–*–π interactions are in OH2–*–π(C10H8), (OH2)2–*–π(C10H8) and HE–H–*–π(C10H8) (denoted by HHE–*–C10H8) (E = S, Se and Te). Asterisks * emphasize the existence of bond critical points (BCPs) on the interactions in question. Hb(rc) are plotted versus Hb(rc) − Vb(rc)/2 at the BCPs in QTAIM-DFA. Plots for the fully optimized structures are analyzed using the polar coordinate (R, θ) representation. Those containing the perturbed structures are by (θp, κp): θp corresponds to the tangent line of the plot and κp is the curvature. While (R, θ) describe the static nature, (θp, κp) represent the dynamic nature of interactions. The θ and θp values are less than 90° for all interactions in question, examined in this work, except for θp = 90.6° for HHTe–*–π(C10H8). Therefore, all interactions examined are classified by the pure-CS (closed shell) interactions and predicted to have vdW-nature, except for HHTe–*–π(C10H8), which should have the character of the typical HB-nature without covalency. The π–EB interaction in HHS–*–C10H8 is predicted to have the border character between the vdW-nature and the typical HB-nature without covalency, since θp = 89.8°. The nature of four interactions appeared between 2H in TeH2 and C10H8 in TeH2–*–π(C10H8) is also clarified well using QTAIM-DFA.

Nature of S2Se2 σ(4c–6e) at naphthalene 1,8-positions and models, elucidated by QTAIM dual functional analysis

The nature of extended hypervalent interactions of the BE–*–AE–*–AE–*–BE type is elucidated for 1-(8-MeBEC10H6)AE–AE(C10H6BEMe-8′)-1′, (1 (AE, BE) = (S, S), 2 (S, Se), 3 (Se, S) and 4 (Se, Se)) and models A–D, BR2BE⋯(AR)AE–AE(AR)⋯BEBR2 (AR, BR = H and Me). QTAIM dual functional analysis, which we proposed recently, is applied to the analysis. Total electron energy densities Hb(rc) are plotted versus Hb(rc) − Vb(rc)/2 for the interactions at bond critical points (BCPs; *), where Vb(rc) show potential energy densities at BCPs. Data for the perturbed structures around the fully optimized structures are employed for the plots, in addition to those of the fully optimized ones. While the data for the fully optimized structures are analysed by the polar coordinate (R, θ) representation, those containing the perturbed structures are by (θp, κp): θp corresponds to the tangent line for the plot and κp is the curvature. While (R, θ) show the static nature, (θp, κp) represent the dynamic nature of interactions. All AE–*–AE interactions in 1–4 and models A–D are classified by the shard shell interactions and have the character of a weak covalent nature. The AE–*–BE interactions in 1–4 are all classified by the regular closed shell interactions. They are predicted to have the typical HB (hydrogen bond) nature with covalency for 1 and 2 but the nature of the molecular complex formation through CT for 3 and 4. The AE–*–BE interactions in models A–D are predicted to be weaker than those in 1–4.

Dynamic and static behavior of the E–E′ bonds (E, E′ = S and Se) in cystine and derivatives, elucidated by AIM dual functional analysis

Atoms-in-molecules dual functional analysis (AIM-DFA) is applied to the E–E′ bonds (E, E′ = S and Se) in R-cystine (1) and the derivatives of 1, together with MeEE′Me. Hb(rc) are plotted versus Hb(rc) − Vb(rc)/2 at bond critical points (BCPs), where Hb(rc) − Vb(rc)/2 = (ħ2/8m)∇2ρb(rc). The plots are analyzed by the polar coordinate (R, θ) representation. Data of perturbed structures around the fully optimized structures are also plotted in this treatment. Perturbed structures are generated using NIV (normal coordinates of internal vibrations). Each plot for an interaction with data of a fully optimized and four perturbed structures gives a curve, which supplies important information. It is expressed by (θp, κp): θp corresponds to the tangent line for the plot measured from the y-direction and κp is the curvature. While (R, θ) correspond to the static nature of interactions, (θp, κp) represent the dynamic nature. The behavior of the E–E′ bonds is well described by (R, θ) and (θp, κp).

Linear Four-Chalcogen Interactions in Radical Cationic and Dicationic Dimers of 1,5-(Dichalcogena)canes: Nature of the Interactions Elucidated by QTAIM Dual Functional Analysis with QC Calculations

The dynamic and static nature of extended hypervalent interactions of the BE···AE···AE···BE type are elucidated for four center-seven electron interactions (4c-7e) in the radical cationic dimers (1·+) and 4c-6e in the dicationic dimers (12+) of 1,5-(dichalcogena)canes (2: AE(CH2CH2CH2)2BE: AE, BE = S, Se, Te, and O). The quantum theory of atoms-in-molecules dual functional analysis (QTAIM-DFA) is applied for the analysis. Total electron energy densities Hb(rc) are plotted versus Hb(rc) - Vb(rc)/2 [= (ℏ2/8m)∇2ρb(rc)] at bond critical points (BCPs) of the interactions, where Vb(rc) values show potential energy densities at BCPs. Data from the fully optimized structures correspond to the static nature of the interactions. Those from the perturbed structures around the fully optimized ones are also plotted, in addition to those of the fully optimized ones, which represent the dynamic nature of interactions. The BE···AE-AE···BE interactions in 12+ are stronger than the corresponding ones in 1·+, respectively. On the one hand, for 12+ with AE, BE = S, Se, and Te, AE···AE are all classified by the shared shell interactions and predicted to have the weak covalent nature, except for those in 1a2+ (AE = BE = S) and 1d2+ (AE = BE = Se), which have the nature of regular closed shell (r-CS)/trigonal bipyramidal adduct formation through charge transfer (CT-TBP). On the other hand, AE···BE are predicted to have the nature of r-CS/molecular complex formation through charge transfer for 1a2+, 1b2+ (AE = Se; BE = S), and 1d2+ or r-CS/CT-TBP for 1c2+ (AE = Te; BE = S), 1e2+ (AE = Te; BE = Se), and 1f2+ (AE = BE = Te). The BE···AE-AE···BE interactions in 1·+ and 12+ are well-analyzed by applying QTAIM-DFA.