Prediction and characterization of halogen–hydride interaction in Cu n H n ···ClC2Z and Cu n H···ClC2Z complexes (n = 2–5; Z = H, F, CH3)

Halogen–hydride interactions between the lowest energy structure of Cu _n H _n and Cu _n H clusters (n = 2–5) as halogen acceptor and ClC₂Z (Z = H, F, CH₃) as halogen donor have been investigated at the MP2/6-311++G(d,p) level of theory. Different approaches based on structural parameters, energetic analysis, shift in vibrational frequencies, and molecular electrostatic potential were used to characterize the resultant halogen–hydride bonds. Upon complexation, the Cl–C bonds tend to elongate, concomitant with red shifts of the Cl–C vibrational frequencies. Interaction energies of this type of halogen bonds vary from ?2.34 to a maximum ?7.38 kJ mol^?1. The calculated interaction energies were found to be increased in magnitude with increasing of the negative electrostatic potential at a point on the outer side of hydrogen atom of halogen acceptor units. Moreover, decomposition of the interaction energies reveals that the electrostatic interaction plays a main role in the formation of the complexes. The quantum theory of atoms in molecules analysis has also been applied to provide more insight into the nature and properties of these interactions. Our results indicate pure closed-shell interactions in these systems with similar characteristics to the conventional halogen bonds.     

Application of nuclear magnetic relaxation to elucidate proton location and dynamics in n···h···o hydrogen bonds

The proton location and dynamics in a hydrogen bond in solution are fundamentally important for understanding the phenomenon of proton transfer (PT). In the present study, the proton location and its dynamics were explored for the NH form of the two PT tautomers of the Schiff base by analyzing the fluctuation of the (15)N-(1)H magnetic dipolar coupling by the PT as well as the NH reorientational motion. For this purpose, the (15)N and (13)C spin-lattice relaxation times were measured in dichloromethane or acetonitrile solutions of three Schiff bases with different substituents on the benzene moieties, N-(4,6-dimethoxysalicylidene)methylamine (compound 1), N-(1-methylnitrilomethylidyne)-2-naphthalenomethylamine (compound 2), and N-(3,5-dibromosalicylidene)-methylamine (compound 3). For the NH form of compound 2 in dichloromethane, the proton location shifted to the center between the nitrogen and oxygen atoms, as compared with the minimum of the PT potential surface derived from molecular orbital calculations. For the NH form of compound 3 in dichloromethane, the proton location shift was not observed, and the PT rate was significantly lower than the reorientation rate of the NH bond. The results are discussed in terms of the electronic effect of the substituents and the static and dynamic solvent effect.     

Density functional investigations on the (H2O)n·CCH and (H2O)n·HCC complexes (n=1–3)

The electronic structures and energies of (H₂O)_n·CCH and (H₂O)_n·HCC complexes (n=1–3) between CCH and water have been theoretically investigated at the UB3LYP/6-311++G(2df,p)//UB3LYP/6-311G(d,p) level. The complexes with n=2–3 are cyclic structures with homodromic hydrogen-bond chain. The (H₂O)_n·CCH (n=1–3) complexes show increasing stabilities towards CCH- or H₂O-eliminations of 2.3, 5.8 and 7.6 kcal/mol and are energetically more stable than the corresponding (H₂O)_n·HCC complexes by 0.8, 2.7 and 3.4 kcal/mol, respectively, due to the charge-separation-enhanced hydrogen bonds within (H₂O)_n·CCH (n=2,3). Strong interactions between CCH and (H₂O)₂ and (H₂O)₃ clusters suggest special solvent effects of water on the chemical behavior of unsaturated radicals.     

Anion photoelectron spectra and ab initio calculations of the iodide-carbon monoxide clusters: I(-)···(CO)(n), n = 1-4

Anion photoelectron spectra are reported for the iodide-carbon monoxide clusters, with supporting ab initio calculations for the 1:1 dimer anion and neutral complexes. A C(s) minimum geometry is predicted for the anion complex, while for the neutral complex two linear van der Waals minima are predicted differing in the attachment point of the iodine, that is, I···CO and I···OC. The predicted adiabatic photodetachment energy agrees well with the experimental spectrum. The photoelectron spectra feature a vibrational progression in the CO stretching mode, which becomes more pronounced for the larger clusters.     

Proton transfer and autoionization in HNO3·HCl·(H2O)n particles

The structure and spectroscopic properties of clusters of HNO(3)·HCl·(H(2)O)(n), with n = 1 to 6, have been calculated at the MP2/aug-cc-pVDZ level of theory. Altogether 22 different clusters have been found as stable structures, with minima in their potential energy surfaces. The clusters can be grouped in families with the same number of water molecules, and with close aggregation energies within each family. The addition of each new water molecule increments the aggregation energy of the clusters by a nearly constant value of 76.2 ± 0.1 Hartree. The proton transfer parameter and the coordination number of HNO(3) and HCl in each cluster have been evaluated, and the wavenumber shifts for the X(-)-H(+) vibration from the corresponding mode in the isolated molecules have also been predicted. These values allow classification of the acidic species in the clusters into three types, characterized by the strength of the hydrogen bond and the degree of ionization. A correspondence is found between the coordination number of HNO(3) and the magnitude of the X(-)-H(+) vibrational shift.     

Theoretical Studies on the Intermonomer Interaction of F-·(H2O)n (n = 1,2)

Five optimized geometries of F-·(H2O)n (n = 1, 2) were obtained with ab initio calculation at the B3LYP/6-311++G** level.The accurate intermonomer interaction energy was calculated using the MP2 electron correlation correction as well as the basis set superposition error correction by the Boys-Bernardi "counterpoise" protocol.Natural bond orbital (NBO) theory was applied to quantify the relative strength of these interactions and account for their effects on the stability, structural and vibrational parameters of Fˉ·(H2O)n (n = 1, 2).It is shown that the charge transferring from the lone pair of F-1 to the σ*OH(…F) antibonding orbital is important.The results indicate the occupancy of σ*OH(…F) is increased (denoted Δσ*OH(…F)) and the ΔROH(…F) bond is leng- thened (denoted (ROH(…F)), leading to the red-shift and the red-shift values have linear correlation with both Δσ*OH(…F) and ΔROH(…F).     

SiO2·(CO)n(n=1～2)结构和属性的理论研究

用密度泛函理论详细地研究了SiO2·(CO)n(n=1～2)的结构和属性.研究表明,SiO2·CO是一个T形的具有C2v对称性的分子,SiO2·(CO)2具有C2对称性的分子;频率计算结果与实验值一致,CO在与SiO2成键过程中,C-O伸缩振动频率有所增加,说明静电势在复合过程中起了重要作用;基组重叠误差(BSSE)修正在计算相互作用能时不可忽视,相互作用能和解离能的计算以及NBO分析表明,SiO2·(CO)2中的SiO2与CO之间的作用相对SiO2·CO来说较弱;SiO2和CO2与CO的成键特点不同,主要是缘于SiO2与CO2的能隙不同.     

Nonconventional C–H···Cu Interaction Between Copper Cun Clusters (n = 3–20) and Aromatic Compounds

The present study examines bonding patterns between copper Cu_n clusters (n?=?3–20) and aromatic compounds (benzene, phenol, and benzaldehyde) using a density-functional theory (DFT) approach. Hirshfeld population, natural bond orbital (NBO), molecular orbitals, and quantum theory of atoms in molecules (QTAIM) analyses suggested the formation of two types of interactions Cu–arene and C–H···Cu, in the complexation of copper clusters by an aromatic compound.

     

A density functional theory study of the Cu+·(CO)n (n = 1–3) complexes

Density functional theory calculations, with an effective core potential for the copper ion, and large polarized basis set functions have been used to construct the potential energy surface of the Cu⁺·(CO)_n (n = 1–3) complexes. A linear configuration is obtained for the global minimum of the Cu⁺·CO and Cu⁺·(CO)₂ complexes with a bond dissociation energy (BDE) of 35.9 and 40.0 kcal mol^-1, respectively. For the Cu⁺·(CO)₃ complex, a trigonal planar geometry is obtained for the global minimum with a BDE of 16.5 kcal mol^?1. C-coordinated copper ion complexes exhibit stronger binding energy than O-coordinated complexes as a result of C_lp → 4s σ-donation. The computed sequential BDEs of Cu⁺·(CO)_n (n = 1–4) complexes agree well with experimental findings, in which the electrostatic energy and σ-donation play an important role in the observed trend.     

Anticooperativity of FH···Cl− hydrogen bonds in [FH)nCl]− clusters (n = 1…6)

The change of cooperativity of FH···Cl⁻ hydrogen bonds upon sequential addition of up to six FH molecules to the Cl⁻ first coordination sphere is investigated. The geometry of clusters [(FH) _nCl]⁻ (n = 1…6) was calculated (CCSD/aug-cc-pVDZ) and compared with [(FH) _nF]⁻ clusters. The geometry is determined by the symmetry-driven electrostatic requirements and also by the fact that formation of each new FH···Cl⁻ bond creates a depression in the chlorine's electron cloud on the opposite side of Cl⁻ (σ-hole), which limits the range of directions available for subsequent H-bond formation. The mutual influence of FH···Cl⁻ hydrogen bonds is anticooperative—the addition of each FH molecule weakens H-bonds by 23–16% and decreases their covalent character (as seen by LMO-EDA decomposition and QTAIM analysis). Anticooperativity effects could be tracked by spectroscopic parameters (frequency of local HF mode ν_FH, chemical shift δ_H, spin–spin coupling constants ¹J_FH, ^1hJ_HCl, ^2hJ_FCl and nuclear quadrupolar constants χ_18F, χ_D, and χ_35Cl. © 2019 Wiley Periodicals, Inc.     

Theoretical studies on the coupling interactions in H2SO4···HOO˙···(H2O)n (n = 0-2) clusters: toward understanding the role of water molecules in the uptake of HOO˙ radical by sulfuric acid aerosols

A detailed knowledge of coupling interactions among sulfuric acid (H(2)SO(4)), the hydroperoxyl radical (HOO˙), and water molecules (H(2)O) is crucial for the better understanding of the uptake of HOO˙ radicals by sulfuric acid aerosols at different atmospheric humidities. In the present study, the equilibrium structures, binding energies, equilibrium distributions, and the nature of the coupling interactions in H(2)SO(4)···HOO˙···(H(2)O)(n) (n = 0-2) clusters have been systematically investigated at the B3LYP/6-311++G(3df,3pd) level of theory in combination with the atoms in molecules (AIM) theory, natural bond orbital (NBO) method, energy decomposition analyses, and ab initio molecular dynamics. Two binary, five ternary, and twelve tetramer clusters possessing multiple intermolecular H-bonds have been located on their potential energy surfaces. Two different modes for water molecules have been observed to influence the coupling interactions between H(2)SO(4) and HOO˙ through the formations of intermolecular H-bonds with or without breaking the original intermolecular H-bonds in the binary H(2)SO(4)···HOO˙ cluster. It was found that the introduction of one or two water molecules can efficiently enhance the interactions between H(2)SO(4) and HOO˙, implying the positive role of water molecules in the uptake of the HOO˙ radical by sulfuric acid aerosols. Additionally, the coupling interaction modes of the most stable clusters under study have been verified by the ab initio molecular dynamics.     

Heavy group 14 1,(n+2)-dimetallabicyclo[n.n.n]alkanes and 1,(n+2)-dimetalla[n.n.n]propellanes: are they all realistic synthetic targets?

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