Proposal for Sets of (77)Se NMR Chemical Shifts in Planar and Perpendicular Orientations of Aryl Group and the Applications

The orientational effect of p-YC(6)H(4) (Ar) on δ(Se) is elucidated for ArSeR, based on experimental and theoretical investigations. Sets of δ(Se) are proposed for pl and pd employing 9-(arylselanyl)anthracenes (1) and 1-(arylselanyl)anthraquinones (2), respectively, where Se–C (R) in ArSeR is on the Ar plane in pl and perpendicular to the plane in pd. Absolute magnetic shielding tensors of Se (σ(Se)) are calculated for ArSeR (R = H, Me, and Ph), assuming pl and pd, with the DFT-GIAO method. Observed characters are well reproduced by the total shielding tensors (σ (t)(Se)). The paramagnetic terms (σ (P)(Se)) are governed by σ (P)(Se)(xx) + σ (P)(Se)(yy), where the direction of n(P)(Se) is set to the z-axis. The mechanisms of the orientational effect are established both for pl and pd. Sets of δ(Se: 1) and δ(Se: 2) act as the standards for pl and pd, respectively, when δ(Se) of ArSeR are analyzed based on the orientational effect

Fine Structures of 8-G-1-(p-YC6H4C ≡ CSe)C10H6 (G = H, Cl, and Br) in Crystals and Solutions: Ethynyl Influence and Y- and G-Dependences

Fine structures of 8-G-1-(p-YC6H4C ≡ CSe)C10H6 [1 (G = H) and 2 (G = Cl): Y = H (a), OMe (b), Me (c), F (d), Cl (e), CN (f), and NO2 (g)] are determined by the X-ray analysis. Structures of 1, 2, and 3 (G = Br) are called A if each Se–Csp bond is perpendicular to the naphthyl plane, whereas they are B when the bond is placed on the plane. Structures are observed as A for 1a–c bearing Y of nonacceptors, whereas they are B for 1e–g with Y of strong acceptors. The change in the structures of 1e–g versus those of 1a–c is called Y-dependence in 1. The Y-dependence is very specific in 1 relative to 1-(p-YC6H4Se)C10H7 (4) due to the ethynyl group: the Y-dependence in 1 is almost inverse to the case of 4 due to the ethynyl group. We call the specific effect “Ethynyl Influence.” Structures of 2 are observed as B: the A-type structure of 1b changes dramatically to B of 2b by G = Cl at the 8-position, which is called G-dependence. The structures of 2 and 3 are examined in solutions based on the NMR parameters

Synthesis, structural, spectroscopic and electrochemical studies of carborane substituted naphthyl selenides

[EN] New unsymmetrical selenides bearing an o-carborane and a naphthalene ring as the substituents were prepared by the cleavage of the corresponding diselenides. The compounds were characterized by means of spectroscopic and analytical methods. Se-77 NMR signals of the selenium atoms attached to the carbon atoms of the carborane cages are shifted downfield in comparison to those bonded only to the aromatic rings, indicating an electron withdrawing effect of the o-carboranyl substituent. Compounds 1-(2-R-1,2-dicarba-closo-carboranyl)naphthyl selenides (R = Me, 1; Ph, 2) were characterized by means of single crystal X-ray diffraction. The influence of the electronic nature of the substituents attached to the selenium atoms on the structural parameters and packing properties of naphthyl selenides are discussed. Theoretical calculations and cyclic voltammetry (CV) studies were carried out to compare the bonding nature of carboranyl and analogous aryl selenium compounds. Cyclic voltammetry studies of naphthyl carboranyl mono and diselenides have shown that the carboranyl fragment polarizes the Se lone pair making it less prone to generate a Se-Se bond.This work was supported by the Japan-Spain Research Cooperative Program, Joint Project, 2004JP0102 from Japan Society for the Promotion of Science (JSPS) and CSIC, CICYT (CTQ2010-16237) and the Generalitat de Catalunya, 2009/SGR/00279. Dr O. Guzyr is grateful to Ministerio Education, Cultura y Deporte for grant SAB2003-0122.Guzyr, O.; Viñas, C.; Wada, H.; Hayashi, S.; Nakanishi, W.; Teixidor, F.; Vaca Puga, A.... (2011). Synthesis, structural, spectroscopic and electrochemical studies of carborane substituted naphthyl selenides. Dalton Transactions. 40(13):3402-3411. https://doi.org/10.1039/c0dt01658fS34023411401

Dynamic and Static Nature of Br4σ(4c–6e) and Se2Br5σ(7c–10e) in the Selenanthrene System and Related Species Elucidated by QTAIM Dual Functional Analysis with QC Calculations

The nature of Br4σ(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 Se2Br5σ(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

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 Hb(rc) are plotted versus Hb(rc) − Vb(rc)/2 at bond critical points (BCPs), where Vb(rc) 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

Analysis of One-Bond Se-Se Nuclear Couplings in Diselenides and 1,2-Diselenoles on the Basis of Molecular Orbital Theory: Torsional Angular Dependence, Electron Density Influence, and Origin in J1(Se, Se)

Nuclear couplings for the Se-Se bonds, J1(Se, Se), are analyzed on the basis of the molecular orbital (MO) theory. The values are calculated by employing the triple ζ basis sets of the Slater type at the DFT level. J1(Se, Se) are calculated modeled by MeSeSeMe (1a), which shows the typical torsional angular dependence on ϕ(CMeSeSeCMe). The dependence explains well the observed J1(Se, Se)obsd of small values (≤64 Hz) for RSeSeR′ (1) (simple derivatives of 1a) and large values (330–380 Hz) observed for 4-substituted naphto[1,8-c,d]-1,2-diselenoles (2) which correspond to symperiplanar diselenides. J1 (Se, Se : 2) becomes larger as the electron density on Se increases. The paramagnetic spin-orbit terms contribute predominantly. The contributions are evaluated separately from each MO (ψi) and each ψi→ψa transition, where ψi and ψa are occupied and unoccupied MO's, respectively. The separate evaluation enables us to recognize and visualize the origin and the mechanism of the couplings

Role of d<i>G/</i>d<i>w</i> and d<i>V/</i>d<i>w</i> in AIM Analysis: An Approach to the Nature of Weak to Strong Interactions

Role of d<i>G</i>_b(<i><b>r</b></i>_c)/d<i>w</i> and d<i>V</i>_b(<i><b>r</b></i>_c)/d<i>w</i> is revealed as the basic atoms-in-molecules (AIM) functions to evaluate, classify, and understand the nature of interactions, as well as <i>G</i>_b(<i><b>r</b></i>_c) and <i>V</i>_b(<i><b>r</b></i>_c). The border area between van der Waals (vdW) adducts and hydrogen-bonded (HB) adducts is shown to appear at around d<i>G</i>_b(<i><b>r</b></i>_c)/d<i>w</i> = −d<i>V</i>_b(<i><b>r</b></i>_c)/d<i>w</i> and that between molecular complexes (MC) and trigonal bipyramidal adducts (TBP) of chalcogenide dihalides appears at around 2d<i>G</i>_b(<i><b>r</b></i>_c)/d<i>w</i> = −d<i>V</i>_b(<i><b>r</b></i>_c)/d<i>w</i>. <i>H</i>_b(<i><b>r</b></i>_c) are plotted versus <i>H</i>_b(<i><b>r</b></i>_c) – <i>V</i>_b(<i><b>r</b></i>_c)/2 at bond critical points (BCPs) in the AIM dual functional analysis. The plots incorporate the classification of interactions by the signs of ∇²ρ_b(<i><b>r</b></i>_c) and <i>H</i>_b(<i><b>r</b></i>_c). <i>R</i> [= (<i>x</i>² + <i>y</i>²)^1/2] corresponds to the energy for the interaction in question at BCPs, where (<i>x</i>, <i>y</i>) = (<i>H</i>_b(<i><b>r</b></i>_c), <i>H</i>_b(<i><b>r</b></i>_c) – <i>V</i>_b(<i><b>r</b></i>_c)/2) and (<i>x</i>, <i>y</i>) = (0, 0) at the origin. The segment of lines for the plots (<i>S</i>) should correspond to energy, if the segment is substantially linear. The first derivative of <i>S</i> (d<i>S</i>) is demonstrated to be proportional to <i>R</i>. Relations between AIM functions, such as d<i>V</i>_b(<i><b>r</b></i>_c)/d<i>w</i>, d<i>G</i>_b(<i><b>r</b></i>_c)/d<i>w</i>, d<i>H</i>_b(<i><b>r</b></i>_c)/d­[<i>H</i>_b(<i><b>r</b></i>_c) – <i>V</i>_b(<i><b>r</b></i>_c)/2], d²<i>V</i>_b(<i><b>r</b></i>_c)/d<i>w</i>², d²<i>G</i>_b(<i><b>r</b></i>_c)/d<i>w</i>², and d²<i>H</i>_b(<i><b>r</b></i>_c)/d­[<i>H</i>_b(<i><b>r</b></i>_c) – <i>V</i>_b(<i><b>r</b></i>_c)/2]², are also discussed. The results help us to understand the nature of interactions