“Solid-Liquid” Vitrimers Based on Dynamic Boronic Ester Networks

The "solid-liquid" behavior of vitrimers have not been systematically investigated. Herein, a series of "solid-liquid" vitrimers bearing varying contents of dynamic boronic ester bonds were synthesized via thiol-ene click reactions. These vitrimers allow for flexibile modulation of their network structures and thus show a range of intriguing properties including high stretchability, flexible transition from elasticity to plasticity, strong strain rate dependence, and solid-liquid performance. Th...     

过渡金属催化合成含氮杂环化合物的研究进展

含氮杂环化合物是一类非常重要的有机杂环化合物,也是有机合成化学的研究热点之一。本文首先简要介绍了含氮杂环化合物在天然产物、合成药物和功能材料中的分布及其广泛应用;然后以不同过渡金属催化剂为线索,按照时间由远至近的顺序分别概述了Pd、Ag、Fe、Ni、Zn、Cu等六类过渡金属催化剂在合成五、六元含氮杂环化合物方面的研究进展,对反应条件、反应特征进行了概括;最后对含氮杂环化合物合成领域的过渡金属催化剂的整体发展趋势进行了归纳总结。     

Strength of Intramolecular Hydrogen Bonds

The concept of resonance-assisted hydrogen bonds(RAHBs)highlights the synergistic interplay between theπ-resonance and hydrogen bonding interactions.This concept has been well-accepted in academia and is widely used in practice.However,it has been argued that the seemingly enhanced intramolecular hydrogen bonding(IMHB)in unsaturated compounds may simply be a result of the constraints imposed by theσ-skeleton framework.Thus,it is crucial to estimate the strength of IMHBs.In this work,we used two approaches to probe the resonance effect and estimate the strength of the IMHBs in the two exemplary cases of the enol forms of acetylacetone and o-hydroxyacetophenone.One approach is the block-localized wavefunction(BLW)method,which is a variant of the ab initio valence bond(VB)theory.Using this approach,it is possible to derive the geometries and energetics with resonance shut down.The other approach is Edmiston’s truncated localized molecular orbital(TLMO)technique,which monitors the energy changes by removing the delocalization tails from localized molecular orbitals.The integrated BLW and TLMO studies confirmed that the hydrogen bonding in these two molecules is indeed enhanced byπ-resonance,and that this enhancement is not a result ofσconstraints.     

简单的配体改变调控钌配合物催化还原CO2的活性：硼基配体的对位效应和Ru―H键的性质

开发高效的催化剂用于催化还原CO₂转化为甲酸和它的盐类已经成为研究的热点,是因为将CO₂转化为C1产物不仅可以解决CO₂的含量升高带来的环境问题,还可以解决化石能源燃烧日趋严重的问题。贵金属配合物催化CO₂转化为甲酸和甲酸盐类是目前这类反应最有效的方式,尤其是Ru、Ir和Rh等贵金属。我们之前的研究结果表明Ir(Ⅲ), Ru(Ⅱ)类配合物催化还原CO₂转化为甲酸盐的活性是由配合物Ru―H键的成键性质决定的。它们能高活性的催化CO₂是由于它们都含有同一种特点的Ru―H键,是由Ru的sd²杂化轨道和H的1s轨道杂化而成的,而且这一特点可以被活性氢的对位配体显著影响。鉴于硼基配体具有强的对位效应,我们基于高活性的均相催化剂Ru(PNP)(CO)H₂ (PNP = 2, 6-二(二叔丁基磷甲基)-吡啶)设计了Ru-PNP-HBcat和Ru-PNP-HBpin,并计算了二者催化还原CO₂的活性。Bcat和Bpin配体是实验上常用的硼基配体。我们的计算结果表明Ru-PNP-HBcat和Ru-PNP-HBpin有比Ru-PNP-H₂更长的Ru―H键、亲核性更强的活性氢,其Ru―H键中的Ru原子的d轨道杂化成分的贡献也比Ru-PNP-H₂的更少。相应地Ru-PNP-HBcat和Ru-PNP-HBpin活化CO₂的能垒比Ru-PNP-H₂低。而且Ru-PNP-H₂、Ru-PNP-HBcat和Ru-PNP-HBpin催化CO₂转化为甲酸盐的能垒分别为76.2、67.8、54.4 kJ∙mol^-1,表明Ru-PNP-HBpin具有最高的催化活性。因此,钌配合物催化还原CO₂的活性可由硼基配体强的对位效应和Ru―H键的成键性质来调控。     

Synthesis and Crystal Structure of a Complex of Melamine with Benzoic Acid

A new complex of melamine（MA） with benzoic acid（HBA） was prepared, affording [（HMA＋）（BA-）]-2H2O. Each HBA molecule is deprotonated and one triazine nitrogen atom of MA is protonated. The adjacent HMA＋ cations are related via an inverse center to form ribbons with a pair of N--H…N hydrogen bonds. COO- groups of BA- anions are hydrogen bonded to alternate sides of the （HMA＋）∞ ribbons to generate indention ID tapes, which are extended into a 3D structure via N--H…O- and N--H…OW hydrogen bonds and π-π stacking interactions. Predominant patterns of the hydrogen bond present in the complex are anion/water and amino/water tape structures. The hydrogen-bonding patterns consist of alternate 6, 10-membered rings sharing two edges. Infrared（IR） spectroscopy conforms that proton transfer has taken place in the complex.     

硝酸镧与冠醚(2, 2)配合物的晶体及电子结构研究

用X-射线单晶衍射法测定了硝酸镧与冠醚(2,2)配合物的晶体结构,发现其具有与报道的Eu(NO_3)_3(2,2)配合物不同的配位方式.晶体属于三斜晶系,空间群P(?),晶胞参数为a=10.312(2)(?);b=12.745(3)(?);c=8.917(2)(?);α=103.79(2)°;β=112.73(2)°;γ=83.68(2)°;V=1049.5(5)(?)~3;F(000)=587.88;Z=2.结构用重原子法解出;R值为0.0292.用INDO法计算了配合物的净电荷分布,电子结构、键级.结果表明,镧与配位原子间的键具有一定程度的共价性.镧的5d轨道对共价性的贡献最大,而4f轨道基本上不参与成键.La-N比La-O(醚)间存在较强的作用,增大了配合物的稳定性.     

Synthesis, Characterization, and X-Ray Diffraction Analysis of Triethylenetetraammonium Tetrathiomolybdate

The reaction of gaseous H₂S with aqueous ammonium heptamolybdate in the presence of triethylenetetramine (trien) gave a red complex. The complex was recrystallized in hot water and characterized by element analysis and UV, visible, IR, and ¹H NMR spectroscopy. PMR has revealed accidental magnetic equivalence, resulting from the proximity of [MoS₄]^2- species in one complex molecule to the open triethylenetetramine ligand of another molecule. (TrienH₂)[MoS₄] crystallizes in the orthorhombic crystal system, space group Pca2₁, a=13.045(2), b=16.461(3), c=13.754(2) , =90, =90, =90°, V=2953.5(9) ³, Z=8, R₁=0.0323, wR₂=0.0730. The structure consists of the tetrahedral tetrathiomolybdate anions, forming an extended 3D framework in solids due to the interactions with triene cations via Mo-S...H-N hydrogen bonds.     

A Novel Mononuclear Copper（Ⅱ） Complex：Crystal Structure and DNA Cleavage Ability

The reaction of N-tosylatirdine with 1,2-diaminopropane in dry benzene solution yields an intermediate H2L, N,N,N',N'-tetrakis(2-(p-tolylsulfonyl)aminoethyl) propane-1,2-diamine. The mononuclear copper(Ⅱ) complex, [CuLH2O]·H2O, was synthesized by the reaction between the intermediate and copper(Ⅱ) in absolute methanol. The complex has been characterized by IR, UV-vis and X-ray diffraction technology, and its crystal crystallizes in the orthorhombic system, space group Pbca with a = 15.589(1), b = 21.897(2), c = 27.645(2) , V = 9436.4(1) 3, Dc = 1.352 g/cm3, Z = 8, Mr = 960.68, F(000) = 4040, μ(MoKa) = 0.698 mm-1, S = 0.98, R = 0.0537 and wR = 0.1180 for 5804 observed reflections (I > 2σ(I)). In the crystal structure, a one-dimensional chain is formed by abundant hydrogen bond interactions. The interaction of the complex with DNA was monitored using agarose gel electrophoresis. The result shows that the complex can transform the supercoiled to nicked and liner forms, and has a concentration-dependent cleavage activity.     

Ⅱ conjugation in the butadiene

The π electronic delocalization in trans-C4H6 and cis-C4H6 has been investigated in the frame of ab initio valence bond theory with 6-31G basis set. The result shows that the Csp2-Csp2 single bond length (1.506 A) is only about 0.024 A shorter than the Csp3-Csp3 bond, thus the central bond length shortening would be mainly due to π conjugation. The theoretical resonance energies of the trans-C4H6 and cis-C4H6 are 8.48 and 7.44 kcal/mol, respectively.