卤键的AIM研究

本文利用分子中的原子理论对一系列含卤分子与氨之间形成的卤键进行了分析，内容包括键关键点的确定、关键点的电子密度和拉普拉斯量以及复合物形成前后的若干原子性质，如电荷、能量、极化矩、卤键供体原子体积等的变化。结果显示：（1）所有卤键复合物中均存在一键关键点，其作用属于闭壳型相互作用；（2）卤键复合物键关键点的电子密度及其拉普拉斯量与卤键的强度间存在很好的线性关系；（3）键关键点电子密度的对数与卤键的距离d(X···N)高度相关。这一研究有望对卤键的本质提供进一步的认识。     

Co-existing Intermolecular Halogen Bonding and Hydrogen Bonding in the Compound Trans-5,10-bis（1-bromodifluoro-acetyl-1-ethoxycarbonyl-methylidene）thianthrene

Trans-5,10-bis(1-bromodifluoroacetyl-l-ethoxycarbonyl-methylidene)thianthrene (1b) was prepared from the reaction of BrCF2COC(N2)CO2Et with thianthrene. X-ray single crystal diffraction analysis showed that the intermolecular halogen bonding and hydrogen bonding coexisted in this compound. The bromine atom acted as an electron acceptor in the halogen bond and an electron donor in the hydrogen bond. It is the first example that the bromine atom acted as such a dual role in the hydrogen and halogen bond.     

Theoretical Study of Nonclassical Platinum Complexes Bonding to Purine Bases： How the Long-lived Monofunctional Adducts Can Be in Existence？

1 INTRODUCTION Since the discovery of the anticancer activity of cisplatin by Roserberg, cisplatin has become one of the most widely utilized antitumor drugs in the world, with an annual sales of approximately 500 million dollars[1~6]. Because of the successful story of cisplatin, a great deal of attention was drawn to platinum complexes and many studies were focused on the influence of different ligands and conforma- tions on anticancer property[7]. Subsequently, much progress has been …     

Cleavage of the Fe—Fe Bond of （Me2SiSiMe2） [η^5－C5H4Fe（CO）2]2 with Na／Hg and Molecular Structure of the Ring－Opened Complex

The reaction of the rifle cyclic complex (1) with sodium amalgam in THF resulted in the expected cleavage of the Fe-Fe bond to afford his-sodium salt ( Me2SiSiMe2 ) [η^5-C5H4Fe(CO)2]2 (4). The latter was not isolated and was used directly to react with MeI, PhCH2Cl, CH3C(O)Cl, PhC(O)Cl,Cy3SnCl (Cy= cyclohexyl) or Ph3SnCl to afford corresponding ring-opened derivatives (Me2SiSiMe2) [η^5-C5H4Fe(CO)2]2 [5, R=Me; 6, R=PhCH2; 7, R=CH3C(O); 8, R=PhC(O); 9, R = Cy3Sn or 10, R = Ph3Sn ]. The crystal and molecular structures of 10 were determined by X-ray diffraction analysis. The molecule took the desired ant/ conformation around the Si-Si bond. The length of the Si--Si bond is 0.2343(3)nm, which is essentially identical to that in the cyclic structure of 1[0.2346(4) tun]. This result unambiguously demonstrates that the Si--Si bond in the cyclic structure of 1 is not subject to obvious strain.     

Synthesis and Structure of a Novel Copper（Ⅱ） Dinuclear Complex with 4,4′-Dipyridyl as the Bridge

With N,N′-bis(benzimidazol-2-methyl)amine as the ligand,a novel Cu(Ⅱ) dinuclear complex was synthesized as a mimetic compound of superoxide dismutase(SOD).The complex was characterized with element analysis,UV and IR spectra.The crystal structure was determined by using X-ray diffraction analysis.the crystal structure shows that Cu(Ⅱ) and its coordinated atoms construct distorted octahedron configuration with oxygen atome of (ClO4-)s in the axial directions.The coordinated cations are linked by (ClO4-)s to form nonplanar sheets.All sheets are linked together into three-dimensional network by the intermolecular hydrogen bonds.The result of the activity assay indicates that the complex does have certain biological activity.     

A computational study on the gas phase reaction of Os^＋ with N2O

The reaction of Os~+(~6D,~4F) with N_2O has been investigated at B3LYP/TZVP and CCSD(T)/6-311+G~* levels of theory.The mechanisms corresponding to O-atom and N-atom transfer reactions have been revealed.It was found that on the sextet reaction surface both the O-atom and N-atom transfer reactions undergo through direct-abstraction mechanism,leading to the formation of OsO~+ and OsN~+,whereas on quartet surface the two reactions undergo through O-N bond or N-N bond insertion mechanism.The calculated energ...     

Diorgano, Dichloro－tin （IV） Complexes of 4－X－Benzohydroxamic Acid （X=CI, OCH3）： Synthesis, Characterization, Antitumor Activity in Vitro and the Crystal Structure of trans－ [Me2Sn（L2） 2]

A series of diorganotin (IV) derivatives of R2SRL2 (R = Me, Et, n-Bu, ph or CI; L = Ll or L2) and their corresponding mixed-ligand complexes RESn (L1)(L2) have been prepared and the structure of trans-MeESn (L2)2 was characterized by FT-IR, ^1H, ^13C and ^ll9Sn NMR spectroscopies,MS, elemental analysis, melting points and X-ray diffIaction. The structure-activity relationships were discussed.     

A Facile Synthetic Method for the Preparation of σ－Symmetric （1,2： 4,5）－Diepoxypentane Equivalent

Optically active er -symmetric ( 1,2: 4,5)-diepo .xypentane equivalent (10) has been synthesized in eight steps with moderate yields and diastereomeric excess by using Sharpless asymmetric dihydroxylation (AD reaction). Compound 10 can be used to prepare syn 1,3-diol subunit in natural product.     

Extensive Studies on the AIEt3／THF-Promoted Diastereoselective Tandem Rearrangement／Reduction of a-Hydroxy （Amino） Heterocyclopropane： An Efficient Approach to 2-Quaternary 1,3-Diheteroatom Units

A facile and highly diastereoselective method for the construction of 2-quaternary 1,3-amino alcohols and 1,3-diols has been developed on the basis of the AlEt3/THF-promoted tandem rearrangement/reductive reaction of α-hydroxy (amino) aziridines (epoxides). The progressive achievement in this article included that both 2-epimers of the units could be constructed from the initially same substrate. Also a stereochemistry assignment we reported previously was corrected.     

Theoretical Insights into the Nature of Halogen Bonding in Prereactive Complexes

Benchmark quality geometries and interaction energies for the prereactive halogen‐bonded complexes of dihalogens and ammonia, including hypothetical astatine containing dihalogens, have been produced via explicitly correlated coupled cluster methods. The application of local electron correlation partitioning reveals dispersion, electrostatics and ionic substitutions all contribute significantly to the interaction energy, with a linear relationship between the ionic substitutions and the degree of charge transfer. Potential energy curves for H₃N???ClF show that as the relative orientations of the two subunits are manipulated appreciable interactions can be found at considerably angular displaced geometries, signifying lower directionality in halogen bonding than previously supposed.     

Halogen Bonding: An Interim Discussion

Halogen bonding is a noncovalent interaction that is receiving rapidly increasing attention because of its significance in biological systems and its importance in the design of new materials in a variety of areas, for example, electronics, nonlinear optical activity, and pharmaceuticals. The interactions can be understood in terms of electrostatics/polarization and dispersion; they involve a region of positive electrostatic potential on a covalently bonded halogen and a negative site, such as the lone pair of a Lewis base. The positive potential, labeled a σ hole, is on the extension of the covalent bond to the halogen, which accounts for the characteristic near‐linearity of halogen bonding. In many instances, the lateral sides of the halogen have negative electrostatic potentials, allowing it to also interact favorably with positive sites. In this discussion, after looking at some of the experimental observations of halogen bonding, we address the origins of σ holes, the factors that govern the magnitudes of their electrostatic potentials, and the properties of the resulting complexes with negative sites. The relationship of halogen and hydrogen bonding is examined. We also point out that σ‐hole interactions are not limited to halogens, but can also involve covalently bonded atoms of Groups IV–VI. Examples of applications in biological/medicinal chemistry and in crystal engineering are mentioned, taking note that halogen bonding can be “tuned” to fit various requirements, that is, strength of interaction, steric factors, and so forth.     

AIM and ELF Analyses of Halogen Bonding in NCS:BrCl Complexes

The nature of halogen bonding in five complexes formed between the thiocyanate (NCS) radical and a BrCl molecule was analyzed by quantum theory of atoms in molecules (QTAIM) and electron‐localization function (ELF) in this paper. The calculated results show that the geometry of the halogen atom bonded at the N‐atom is stable than those bonded at S‐ or C‐atom. The molecular electrostatic potentials determine the geometries and stabilities of the complexes. The valence basin of the S‐ or N‐atom in the electron‐donating NCS radical is compressed and its population decreases during the process of formation of the halogen‐bonded complexes.     

Tetrel Bonding Interactions

Tetrel (Tr) bonding is first placed into perspective as a σ‐hole bonding interaction with atoms of the Tr family. An sp³ R₄Tr unit has four σ‐holes with which a Lewis base can form a complex. We then highlight some inspiring crystal structures where Tr bonding is obvious, followed by an account of our own work. We have shown that Tr bonding is ubiquitous in the solid state and we have highlighted that Tr bonding with carbon is possible when C is placed in the appropriate chemical context. We hope that this account serves as an initial guide and source of inspiration for others wishing to exploit this vastly underexplored interaction.     

Stacking Interactions: A Supramolecular Approach to Upgrade Weak Halogen Bond Donors

The co-crystallization of tetracyanobenzene (TCB) with haloarenes ArX provided six new co-crystals TCB ⋅ ArX (ArX=PhCl, PhBr, 4-MeC₆H₄Cl, 4-MeC₆H₄Br, 4-MeOC₆H₄Cl, 1,2-Br₂C₆H₄) which were studied by X-ray diffraction. In these systems, the strong collective effect of π⋅⋅⋅π stacking interactions and lone pair-(X)⋅⋅⋅π-hole-(C) bondings between TCB and ArX promote the strength of X⋅⋅⋅N_cyano halogen bonding (HaB). Theoretical studies showed that the stacking interactions affect the σ-hole depth of the haloarenes, thus significantly boosting their ability to function as HaB donors. According to the molecular electrostatic potential calculations, the σ- hole-(Cl) value (1.5 kcal/mol) in the haloarene 4-MeOC₆H₄Cl (featuring an electron-rich arene moiety and exhibiting very poor σ-hole-(Cl) ability) increases significantly in the stacked trimer (TCB)₂ ⋅ 4-MeOC₆H₄Cl (12.5 kcal/mol). Theoretical DFT calculations demonstrate the dramatic increase of X⋅⋅⋅N_cyano HaB strength for stacked trimers in comparison with parent unstacked haloarenes.     

Halogen Bonding Interactions of Polychlorinated Biphenyls and the Potential for Thyroid Disruption

Polychlorinated biphenyl (PCB) flame retardants are persistent pollutants and inhibit neurodevelopment, particularly in the early stages of life. Halogen bonding (XB) to the iodothyronine deiodinases (Dio) that modulate thyroid hormones (THs) is a potential mechanism for endocrine disruption. Cl⋅⋅⋅Se XB interactions of PCBs with SeMe⁻, a small model of the Dio active site selenocysteine, are compared with previous results on polybrominated diphenylethers (PBDEs) and THs using density functional theory. PCBs generally display weaker XB interactions compared to PBDEs and THs, consistent with the dependence of XB strength on the size of the halogen (I>Br>Cl). PCBs also do not meet a proposed energy threshold for substrates to undergo dehalogenation, suggesting they may behave as competitive inhibitors of Dio in addition to other mechanisms of endocrine disruption. XB interactions in PCBs are position-dependent, with ortho interactions slightly more favorable than meta and para interactions, suggesting that PCBs may have a greater effect on certain classes of Dio. Flexibility of PCBs around the biphenyl C−C bond is limited by ortho substitutions relative to the biphenyl linkage, which may contribute to the ability to inhibit Dio and other TH-related proteins.     

Halogen Bonding in Two-Dimensional Crystal Engineering

Halogen bonds, which provide an intermolecular interaction with moderate strength and high directionality, have emerged as a promising tool in the repertoire of non-covalent interactions. In this review, we provide a survey of the literature where halogen bonding was used for the fabrication of supramolecular networks on solid surfaces. The definitions of, and the distinction between halogen bonding and halogen-halogen interactions are provided. Self-assembled networks formed at the solution/solid interface and at the vacuum-solid interface, stabilized in part by halogen bonding, are discussed. Besides the broad classification based on the interface at which the systems are studied, the systems are categorized further as those sustained by halogen-halogen and halogen-heteroatom contacts.     

Reinvestigation of intramolecular hydrogen bond in malonaldehyde derivatives: An ab initio,AIM and NBO study

The RAHB systems in malonaldehyde and its derivatives at MP2/ 6‐311++G(d,p) level of theory were studied and their intramolecular hydrogen bond energies by using the related rotamers method was obtained. The topological properties of electron density distribution in O? H···O intramolecular hydrogen bond have been analyzed in term of quantum theory of atoms in molecules (QTAIM). Correlations between the H‐bond strength and topological parameters are probed. The results of QTAIM clearly showed that the linear correlation between the electron density distribution at HB critical point and RAHB ring critical point with the corresponding hydrogen bond energies was obtained. Moreover, it was found a linear correlation between the electronic potential energy density, V(r_cp), and hydrogen bond energy which can be used as a simple equation for evaluation of HB energy in complex RAHB systems. Finally, the similar linear treatment between the geometrical parameters, such as O···O or O? H distance, and Lp(O)→σ*_OH charge transfer energy with the intramolecular hydrogen bond energy is observed. © 2010 Wiley Periodicals, Inc., Int J Quantum Chem, 2011     

四元硼氮环成键的研究

在４－３１Ｇ基组水平上，对四元硼氮环做了ＳＣＦ－ＭＯ从头算．根据计算结果，由原子的轨道集居以及σ和π电子的分布，讨论了硼原子与氮原子间的成键情况．结果表明，硼有形成多中心σ键的倾向，且环上π电子极化是指向硼的，同时，硼和氮原子上加氢有利于环的稳定．