超价化合物M_(n+1)F_n(n=1,2;M=Na,K)体系的非线性光学性质的理论研究

采用UMP2/6-311+G(3df)方法研究了一系列化合物M_(n+1)F_n(n=1,2;M=Na,K)体系的几何构型及非线性光学性质(NLO).结果表明:这些体系均为超价化合物,均拥有较大的第一超极化率(β_0).尤其是Na_3F_2体系中结构2c的β_0值为29.16×10~(-49)C~3·m~3·J~(-2),是已知超价化合物Li_3F_2的2c结构的β_0值2.22×10~(-49)C~3·m~3·J~(-2)的13.1倍.     

Theoretical studies on structures and nonlinear optical properties of alkali doped electrides B12N12–M (M = Li,Na, K)

The structures and nonlinear optical properties of a novel class of alkali metals doped electrides B₁₂N₁₂–M (M = Li, Na, K) were investigated by ab initio quantum chemistry method. The doping of alkali atoms was found to narrow the energy gap values of B₁₂N₁₂ in the range 3.96–6.70 eV. Furthermore, these alkali metals doped compounds with diffuse excess electron exhibited significantly large first hyperpolarizabilities (β₀) as follows: 5571–9157 au for B₁₂N₁₂–Li, 1537–18,889 au for B₁₂N₁₂–Na, and 2803–11,396 au for B₁₂N₁₂–K. Clearly, doping of the alkali atoms could dramatically increase the β₀ value of B₁₂N₁₂ (β₀ = 0). Furthermore, their transition energies (ΔE) were also calculated. The results showed that these compounds had low ΔE values in the range 1.407–2.363 eV, which was attributed to large β₀ values of alkali metals doped B₁₂N₁₂ nanocage. © 2016 Wiley Periodicals, Inc.     

Structural properties and nonlinear optical responses of superatom compounds BF4‐M (M = Li,FLi2, OLi3, NLi4)

A new type of superhalogen‐(super)alkali compound, BF₄‐M (M = Li, FLi₂, OLi₃, NLi₄), is theoretically characterized at the MP2/6‐311+G(3df) level. The interaction between superhalogen BF₄ and different shaped (super)alkali M is found to be strong and ionic in nature. Bond energies of these BF₄‐M species are in the range of 200.0–226.7 kcal/mol at the CCSD(T)/6‐311+G(3df) level, which are much larger than the traditional ionic bond energy of 130.1 kcal/mol of FLi. In addition, different from the alkali halides, the BF₄‐M compounds prefer to dissociate into ions rather than neutral fragments. The energetic properties of BF₄‐M are found to be closely related to the size of the M subunit. The different effects of superalkali and superhalogen subunits on the nonlinear optical (NLO) properties of such superatom compounds are also revealed. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Competition between halogen bond and hydrogen bond in complexes of superalkali Li3S and halogenated acetylene XCCH (X = F,Cl, Br,and I)

Complexes of superalkali Li₃S and XCCH (X = F, Cl, Br, and I) have been studied with theoretical calculations at the MP2/aug‐cc‐pVTZ level. Three types of structures are found: (A) the X atom combines with the S atom through a halogen bond; (B) the X atom interacts with the π electron of Li₃S by a π halogen bond; (C) the H atom combines with the S atom through a hydrogen bond. For A and B, a heavier halogen atom makes the interaction stronger, while for C, the change of interaction energy is not obvious, showing a small dependence on the nature of the X atom in HCCX. A is more stable than B and their difference in stability decreases as X varies from Cl to I. For the F and Cl complexes, A is weaker than C, however, the former is stronger than the latter in the Br and I complexes. The above three types of interactions have been analyzed by means of electron localization function, electron density difference, and energy decomposition, and the results show that they have similar nature and features with conventional interactions. © 2014 Wiley Periodicals, Inc.     

Tetrel bonds between PhSiF3/PhTH3 (T = Si,Ge, Sn) and H3ZO (Z = N,P, As): A pentacoordinate silicon (IV) complex

The nature of the complexes PhTH₃ H₃ZO and PhSiF₃ H₃ZO (T = Si, Ge, and Sn; Z = N, P, and As) has been investigated at the MP2/aug’‐cc‐pVTZ(PP) level. These complexes are primarily stabilized by one T···O tetrel bond. Interaction energies of these complexes vary from 11 to 220 kJ/mol, and T···O separations from 1.89 to 3.09 Å. Charge transfer from the O lone pair into the C T and T H σ* antibonding orbitals leads to the stabilization of these complexes. The T···O tetrel bond between PhTH₃/PhSiF₃ and H₃NO exhibits a significant degree of covalence, characterized by the large interaction energy, negative energy density, and large charge transfer. Furthermore, a pentacoordinate silicon (IV) complex is formed in PhSiF₃ H₃NO with the Si···O distance almost close to the length of Si O bond. This indicates that the oxygen atom in N‐oxides shows a strong affinity to the silicon atom in organosilicon compounds.     

Model studies of the optical rotation,and theoretical determination of its sign for β‐pinene and trans‐pinane

We have carried out extensive studies on the basis set dependence of the calculated specific optical rotation (OR) in molecules at the level of the time–dependent Hartree–Fock and density functional approximations. To reach the limits of the basis set saturation, we have devised an artificial model, the asymmetrically deformed (chiral) methane (CM) molecule. This small system permits to use basis sets which are prohibitively large for real chiral molecules and yet shows all the important features of the basis set dependence of the OR values. The convergence of the OR has been studied with n‐aug‐cc‐pVXZ basis sets of Dunning up to the 6–ζ. In a parallel series of calculations, we have used the recently developed large polarized (LPolX) basis sets. The relatively small LPolX sets have been shown to be competitive to very large n‐aug‐cc‐pVXZ basis sets. The conclusions reached in calculations of OR in CM concerning the usefulness of LPolX basis sets have been further tested on (S)‐methyloxirane and (S)‐fluoro‐oxirane. The smallest set of the LPolX family (LPol–ds) has been found to yield OR values of similar quality as those obtained with much larger Dunning's aug‐cc‐pVQZ basis set. These results have encouraged us to carry out the OR calculations with LPol–ds basis sets for systems as large as β‐pinene and trans‐pinane. In both cases, our calculations have lead to the correct sign of the OR value in these molecules. This makes the relatively small LPol–ds basis sets likely to be useful in OR calculations for large molecules. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Tuning the electronic‐optical properties of porphyrin‐like porous C24N24 fullerene with (Li3O)n = (1–5) decoration. A computational study

Using DFT methods, the electronic properties and the first hyperpolarizabilities of porphyrin‐like porous C₂₄N₂₄ fullerene decorated with (Li₃O)_{n = (1–5)} have been systematically investigated. It is found that Li₃O molecules can effectively be adsorbed over N4 cavities of C₂₄N₂₄ with high interaction energies. This interaction is found to narrow the HOMO‐LUMO gap and work function values of C₂₄N₂₄. Thus its electronic properties are strongly sensitive to interaction with the Li₃O molecules. Indeed, compared with the sole parent C₂₄N₂₄ fullerene, (Li₃O)_{n = (1–5)}@C₂₄N₂₄ possess large first hyperpolarizabilities (β₀ ). Obviously, the Li₃O superalkali chemisorbed over C₂₄N₂₄ fullerene exhibit not only excellent stability but also large first hyperpolarizability. Therefore, they are expected to be potential innovative candidates for excellent electro‐optical materials.     

σ‐Hole Opposite to a Lone Pair: Unconventional Pnicogen Bonding Interactions between ZF3 (Z=N,P, As,and Sb) Compounds and Several Donors

The ability of several pnicogen sp³ derivatives ZF₃ (Z=N, P, As, Sb) to interact with electron‐rich entities by means of the opposite face to the lone pair (lp) is investigated at the RI‐MP2/aug‐cc‐pVQZ level of theory. The strength of the interaction ranges from ?1 to ?87 kJ mol^?1, proving its favorable nature, especially when the lp is coordinated to a metal center, whereby the strength of the interaction is significantly enhanced. NBO analysis showed that orbital effects are modest contributors to the global stabilization of the pnicogen σ‐hole bonded complexes studied. Finally, a selection of Cambridge Structural Database examples are shown that demonstrate the impact of this counterintuitive binding mode in the solid state.     

NLO‐X (X = I–III): New Gaussian basis sets for prediction of linear and nonlinear electric properties

New adjusted Gaussian basis sets are proposed for first and second rows elements (H, B, C, N, O, F, Si, P, S, and Cl) with the purpose of calculating linear and mainly nonlinear optical (L–NLO) properties for molecules. These basis sets are new generation of Thakkar‐DZ basis sets, which were recontracted and augmented with diffuse and polarization extrabasis functions. Atomic energy and polarizability were used as reference data for fitting the basis sets, which were further applied for prediction of L–NLO properties of diatomic, H₂, N₂, F₂, Cl₂, BH, BF, BCl, HF, HCl, CO, CS, SiO, PN, and polyatomic, CH₄, SiH₄, H₂O, H₂S, NH₃, PH₃, OCS, NNO, and HCN molecules. The results are satisfactory for all electric properties tested; dipole moment (µ), polarizability (α), and first hyperpolarizability (β), with an affordable computational cost. Three new basis sets are presented and called as NLO‐I (ADZP), NLO‐II (DZP), and NLO‐III (VDZP). The NLO‐III is the best choice to predict L–NLO properties of large molecular systems, because it presents a balance between computational cost and accuracy. The average errors for β at B3LYP/NLO‐III level were of 8% for diatomic molecules and 14% for polyatomic molecules that are within the experimental uncertainty. © 2014 Wiley Periodicals, Inc.     

Synthesis, single crystal X-ray structure and optical properties of 3,4-dimethyl-dithieno[2,3-b:3′,2′-d]thiophene-7,7-dioxide

The synthesis of the title compound (4), starting from commercial 3-bromo-4-methylthiophene, is described. The single crystal packing mode of 4, as well as the absorption and photoluminescence properties in solution and in the solid state are reported and analyzed in relation to those of the isomeric 3,5-dimethyl-dithieno[3,2-b:2′,3′-d]thiophene-4,4-dioxide (7). The different reactivities of 4 and 7 towards bromination are analyzed in the light of the results of ab initio B3LYP/6-31G^∗ calculations on both compounds.     

Structures,Energies, and Fundamental Vibrations of the Sulfonium Ions H3Sn+ (n = 1–4)

Using ab initio MO calculations at the MP2/6‐311G(2df,2pd) level of theory the most stable structures of the following seven ions were determined: H₃S⁺ (C_3v), H₂S–SH⁺ (C_s), H₂S–S–SH⁺ (C₁), HS–S(H)–SH⁺ (C₁), H₂S–S–S–SH⁺ (C₁), HS–S(H)–S–SH⁺ (C₁) and S(SH)₃⁺ (C₃). In the case of the isomeric H₃S₃⁺ cations the species protonated at the terminal sulfur atom is most stable while in the case of the H₃S₄⁺ ions the protonation at the β sulfur atom is energetically preferred. However, the energy differences between isomeric cations are rather small. At the same level of theory the wavenumbers of the harmonic fundamental vibrations were calculated and compared to the available experimental data leading to a support for the existing assignments in certain cases but in some cases to revisions. The reaction enthalpies and Gibbs free energies of the proton transfer reactions H₂S_n + H₂S_n+1 → H₃S_n⁺ + HS_n+1^– were calculated by the G2 method. For n = 1–3 the enthalpies are found in the range 639–731 kJ mol^–1.     

Homonuclear chalcogen–chalcogen bond interactions in complexes pairing YO3 and YHX molecules (Y = S,Se; X = H,Cl, Br,CCH, NC,OH, OCH3): Influence of substitution and cooperativity

MP2/aug‐cc‐pVTZ calculations are performed on complexes of YO₃ (Y = S, Se) with a series of electron‐donating chalcogen bases YHX (X = H, Cl, Br, CCH, NC, OH, OCH₃). These complexes are formed through the interaction of a positive electrostatic potential region (π‐hole) on the YO₃ molecule with the negative region in YHX. Interaction energies of the binary O₃Y???YHX complexes are in the range of ?4.37 to ?12.09 kcal/mol. The quantum theory of atoms in molecules and the natural bond orbital analysis were applied to characterize the nature of interactions. It was found that the formation and stability of these binary complexes are ruled mainly by electrostatic effects, although the electron charge transfer from YHX to YO₃ unit also seems to play an important role. In addition, mutual influence between the Y???N and Y???Y interactions is studied in the ternary HCN???O₃Y???YHX complexes. The results indicate that the formation of a Y???N interaction tends to weaken Y???Y bond in the ternary systems. Although the Y???Y interaction is weaker than the Y???N one, however, both types of interactions seem to compete with each other in the HCN???O₃Y???YHX complexes. © 2016 Wiley Periodicals, Inc.     

Theoretical study of the structural,elastic, electronic and optical properties of XCaF3 (X = K and Rb)

The PLANE WAVE pseudo-potential method within density functional theory (DFT) has been used to investigate the structural, elastic, electronic and optical properties of XCaF₃ (X = K and Rb) insulating. The studied compounds show a weak resistance to shear deformation compared to the resistance to the unidirectional compression. KCaF₃ and RbCaF₃ are considered ductile. The elastic constants and related parameters were predicted. The stiffness is more important in KCaF₃, whereas, the lateral expansion is more important in RbCaF₃. KCaF₃ and RbCaF₃ have R- Г indirect band gap. The main peaks in the imaginary part of the dielectric function correspond to the transition from the occupied state F₋p to the unoccupied states Ca: s or K, Rb: p. At lower energies, KCaF₃ and RbCaF₃ show the same optical properties. Under pressure effect, the peaks of imaginary part of dielectric function were shifted toward high energy.     

Electron-spin magnetic moments of the 2Σ+ ions Li2+, Li2−, and Be2+: An ab initio ROHF study

For the ²Σ⁺ ground states of the ions Li₂⁺, Li₂⁻, and Be₂⁺, the dependence of the magnetic moment (parametrized by g-shifts) on the bond length R was studied at the ROHF level. The Δ g-values were calculated via a perturbative approach (complete to second order in Breit-Pauli interactions) using quadruple-zeta AO basis sets augmented by semidiffuse and polarization functions. All Δ g-values in these systems are negative. The parallel component Δ g_∥ generally changes little with R, remaining close to the g-shift of the corresponding ²S atomic dissociation product. For Li₂⁺ and Be₂⁺, the perpendicular component Δ g _⟂ is more sensitive to geometry than is Δ g_∥, mainly because of the second-order magnetic coupling with excited ²Π states. For Li₂⁻, Δ g _⟂ and Δ g_∥ are similar due to the large size of the 2σ_u, SOMO, resulting in g-values close to that of a free electron. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 511–521, 1997     

CH⋅⋅⋅N Hydrogen‐Bonding Interaction in 7‐Azaindole:CHX3 (X=F,Cl) Complexes

The C?H???Y (Y=hydrogen‐bond acceptor) interactions are somewhat unconventional in the context of hydrogen‐bonding interactions. Typical C?H stretching frequency shifts in the hydrogen‐bond donor C?H group are not only small, that is, of the order of a few tens of cm^?1, but also bidirectional, that is, they can be red or blue shifted depending on the hydrogen‐bond acceptor. In this work we examine the C?H???N interaction in complexes of 7‐azaindole with CHCl₃ and CHF₃ that are prepared in the gas phase through supersonic jet expansion using the fluorescence depletion by infra‐red (FDIR) method. Although the hydrogen‐bond acceptor, 7‐azaindole, has multiple sites of interaction, it is found that the C?H???N hydrogen‐bonding interaction prevails over the others. The electronic excitation spectra suggest that both complexes are more stabilized in the S₁ state than in the S₀ state. The C?H stretching frequency is found to be red shifted by 82 cm^?1 in the CHCl₃ complex, which is the largest redshift reported so far in gas‐phase investigations of 1:1 haloform complexes with various substrates. In the CHF₃ complex the observed C?H frequency is blue shifted by 4 cm^?1. This is at variance with the frequency shifts that are predicted using several computational methods; these predict at best a redshift of 8.5 cm^?1. This discrepancy is analogous to that reported for the pyridine‐CHF₃ complex [W. A. Herrebout, S. M. Melikova, S. N. Delanoye, K. S. Rutkowski, D. N. Shchepkin, B. J. van der Veken, J. Phys. Chem. A­ 2005 , 109, 3038], in which the blueshift is termed a pseudo blueshift and is shown to be due to the shifting of levels caused by Fermi resonance between the overtones of the C?H bending and stretching modes. The dissociation energies, (D₀), of the CHCl₃ and CHF₃ complexes are computed (MP2/aug‐cc‐pVDZ level) as 6.46 and 5.06 kcal mol^?1, respectively.     

Pressure‐Induced Intersite BiM (M=Ru, Ir) Valence Transitions in Hexagonal Perovskites

Pressure‐induced charge transfer from Bi to Ir/Ru is observed in the hexagonal perovskites Ba_3+nBiM_2+nO_9+3n (n=0,1; M=Ir,Ru). These compounds show first‐order, circa 1 % volume contractions at room temperature above 5 GPa, which are due to the large reduction in the effective ionic radius of Bi when the 6s shell is emptied on oxidation, compared to the relatively negligible effect of reduction on the radii of Ir or Ru. They are the first such transitions involving 4d and 5d compounds, and they double the total number of cases known. Ab initio calculations suggest that magnetic interactions through very short (ca. 2.6 Å) M? M bonds contribute to the finely balanced nature of their electronic states.     

Structures of [M(Ura‐H)(H2O)n]+ (M = Mg,Ca, Sr,Ba; n = 1–3) complexes in the gas phase by IRMPD spectroscopy and theoretical studies

The structures of singly and doubly (and for Mg, triply) hydrated group 2 metal dications bound to deprotonated uracil were explored in the gas phase using infrared multiple photon dissociation spectroscopy in the mid‐infrared region (1000–1900 cm^?1) and the O–H/N–H stretching region (2700–3800 cm^?1) in a Fourier transform ion cyclotron resonance mass spectrometer. The infrared multiple photon dissociation spectra were then compared with the computed IR spectra for various isomers. Calculations were performed using B3LYP with the 6‐31 + G(d,p) basis set for all atoms except Ba²⁺ and Sr²⁺, for which the LANL2DZ or the def2‐TZVPP basis sets with relativistic core potentials were used. Atoms‐in‐molecules analysis was conducted for all lowest energy structures. The lowest energy isomers in all cases are those in which the one uracil is deprotonated at the N3 position, and the metal is coordinated to the N3 and O4 of uracil. Regardless of the degree of solvation, all water molecules are bound to the metal ion and participate in a hydrogen bond with a carbonyl of the uracil moiety. Copyright © 2016 John Wiley & Sons, Ltd.