取代基对2-(2-羟基苯基)苯并噻唑分子内氢键及质子转移的影响:密度泛函理论研究

运用密度泛函(DFT)和含时密度泛函(TD DFT)理论方法研究了在2-(2-羟基苯基)苯并噻唑(HBT)苯环羟基的邻位或对位分别引入羟基和醛基后的衍生物分子内质子转移过程,考察了取代基的电子效应及取代位置对分子内氢键和质子转移反应的影响,模拟计算了各分子的IR振动光谱和电子光谱.研究发现,HBT及其衍生物分子可以形成分子内氢键,且激发态时氢键增强.基态时以醇式构型稳定存在,激发态时酮式结构为优势构象.分子的最大吸收峰和发射峰主要源于电子从前线分子轨道HOMO到LUMO之间的跃迁.基态分子内质子转移需要越过较高的能垒因而难以发生,而激发态时只需越过较低能垒就很容易发生激发态分子内质子转移.取代基的电子效应和取代位置对HBT分子氢键强度、互变异构体的相对稳定性、电子光谱及质子转移反应的能垒均有一定影响.     

聚苯胺嵌入氧化石墨复合物的合成及表征

近年来,聚苯胺类导电高分子嵌入无机片层化合物的报道日趋增加.这些材料中,由于无机/有机的纳米复合,一方面使无机材料的传输性能,如导电性等有极大改善,同时也使该类材料的电化学性能有极大的提高.因此对这类纳米复合材料的研究越来越为广大科研工作者所重视[1～8].作为一种二维的层状化合物,氧化石墨层间大量极性基团的存在虽然赋予了氧化石墨丰富的嵌入化学(Ｉｎｔｅｒｃａｌａｔｅｃｈｅｍｉｓｔｒｙ)[7～11],但在一定程度上也破坏了原石墨的晶体结构,致使其导电率大大降低(接近非导体).因此,如何以常用的纳米复合技术实现氧化石墨(ＧＯ…     

微波消解-ICP-AES法同时测定绞股蓝中4种微量元素

采用微波消解法,以HNO3-H2O2对样品进行处理,用电感耦合等离子体发射光谱法(ICP-AES)同时测定了绞股蓝中的铁、锰、铜、锌4种微量元素。结果表明,所测样品中的元素含量按铁、锰、锌、铜顺序递减,各元素测定结果的相对标准偏差在1.0%~3.8%之间,回收率在88%~97%之间。方法简单,有实用意义。     

Theoretical Study of Structure,Energetic, Hydrogen Bonds Strength and Intramolecular Proton Transfer of 2‐(2‐R (ROH,NH2, SH) Phenyl (or Pyridyl)) Benzoxazoles (or Benzothiazoles)

The ground‐ and excited‐state intramolecular proton transfer processes of 2‐(2‐R (R?OH, NH₂, SH) phenyl (or pyridyl)) benzoxazoles (or benzothiazoles) are investigated by the DFT methods. The calculated results indicate that in the ground state there is a high correlation (R=0.9950) between the proton transfer barrier and the intramolecular hydrogen bonds (IMHB) strength. The increase of the strength of IMHB in the proton transfer processes leads to a larger barrier contributions. Intramolecular proton transfer process pathway is along with the minimal difference of change value in the IMHB angle. In the excited‐state, there is a similar relationship between the IMHB and the barrier.     

Synthesis of a Novel Triheterocyclic Framework via 1,3‐Dipolar Cycloaddition of a Nitrile Oxide with Imidazo[2,1‐b][1,3]thiazole‐3(2H)‐ones

A novel series of (9Z)‐9‐arylmethylidene‐3‐(2,6‐dichlorophenyl)‐5,6‐dihydro[1,3]thiazolo[2′,3′:2,3]imidazo [1,2‐d][1,2,4]oxadiazol‐8(9H)‐one derivatives were prepared in moderate yields by the 1,3‐dipolar cycloaddition reaction of a nitrile oxide with (2Z)‐2‐arylmethylidene‐5,6‐dihydroimidazo [2,1‐b][1,3]thiazol‐3(2H)‐ones. The reaction site of the dipolarphile is the C═N of imidazo[2,1‐b][1,3]thiazole rather than the expected C═C of the arylmethylidene. The product structures were characterized thoroughly by IR, MS, NMR spectroscopy, and elemental analysis. The results indicate that this reaction proceeds with chemoselectivity and regioselectivity.     

Synthesis of Novel Spiro Thiazolotriazole Derivatives via 1,3‐Dipolar Cycloaddition of Azomethine Ylide

The 1,3‐dipolar cycloaddition of azomethine ylide generated in situ from isatin and sarcosine to 5‐arylmethylidene thiazolo[3,2‐b][1,2,4]triazol‐6(5H)‐ones afforded novel 1′‐methyl‐4′‐aryldispiro[indole‐3,2′‐pyrrolidine‐3′,5″‐[1,3]thiazolo[3,2‐b][1,2,4]triazole]‐2,6″ (1H)‐diones in moderate yields. The structures of all the products were characterized thoroughly by NMR, infrared spectroscopy (IR), mass spectroscopy (MS) elemental analysis together with X‐ray crystallographic analysis.     

Investigation on the complex of diperoxovanadate with picolinamide

A novel diperoxovanadate complex NH₄[OV(O₂)₂(picolinamide)]·H₂O was synthesized from aqueous solution under physiological conditions. The solution structure of the complex was characterized by multinuclear (¹H, ¹³C, ¹⁴N, and ⁵¹V), variable temperature as well as two-dimensional (DOSY) NMR techniques in the interaction system of NH₄VO₃/H₂O₂/picolinamide at room temperature. The crystal structure of the complex was determined at 223 K by single-crystal X-ray diffraction method. It belongs to the monoclinic space group P21/c with a = 7.323(3) Å, b = 14.255(7) Å, c = 10.022(5) Å, β = 99.524(9)°, V = 1031.7(8) Å³, and Z = 4. The crystal is composed of ammonium ions, picolinamide oxodiperoxovanadate(V) ions, and water molecules, which are held together by ionic and hydrogen bond forces. The species [OV(O₂)₂(picolinamide)]⁻ is seven-coordinated with a distorted pentagonal bipyramidal geometry both in solution and in crystal.     

Electrodeposition of a biocompatible hydroxyapatite matrix to immobilize glucose oxidase for sensitive glucose biosensing

Microchimica Acta - The electrochemical quartz crystal microbalance was used to quantitatively examine the electrodeposition of hydroxyapatite (HA) at a gold electrode. Potentiostatic...     

2-(3-羟基-2-吡啶基)-苯并咪唑的合成、晶体结构及光谱研究

在合成2-(3-羟基-2-吡啶基)-苯并咪唑的基础上, 利用NMR (1H, 13C, COSY, HSQC 和HMBC), MS, IR 和UV 进
行了详细表征; 通过X-ray 单晶衍射测定该化合物的晶体结构, 实验结果表明该晶体属于单斜晶系{空间群为P21/c,
a＝14.289(3) Å, b＝10.618(2) Å, c＝12.783(3) Å, β＝93.51(3)°, V＝1935.8(7) Å3, Z＝8}, 很好支持了波谱表征的结果.
2-(3-羟基-2-吡啶基)-苯并咪唑的荧光光谱表明, 该化合物在激发态下存在双质子转移现象, 密度泛函计算结果合理解
释了实验现象.     

2-(2-巯苯基)苯并噁唑分子内质子转移的理论研究

在B3LYP/6-31G(d,p)水平上研究了2-(2-巯苯基)苯并噁唑气态中五种异构体(E1, E2, E3, E4和K)在气态中的稳定性及其在基态下的质子转移, 同时结合极化连续介质模型(PCM)研究了水、二甲亚砜、乙腈、乙醇、苯胺和环己烷等对2-(2-巯苯基)苯并噁唑溶剂化作用的影响. 研究结果表明, 醇式异构体E1为2-(2-巯苯基)苯并噁唑的优势构型; 在E1向K(酮式异构体)转变过程中, 存在一个较小的能垒; 当考虑零点振动能(ZPVE)后, 逆向能垒消失. 在溶液中, 随着溶剂极性的增强, 醇式异构体E1与K之间的反应平衡向K方向移动, 在非极性溶剂环己烷中, E1为优势构型, 而在强极性水溶液中, K为优势构型.