2-哌嗪基-4-苯基嘧啶衍生物的合成研究

以苯乙酮和苯胺衍生物为起始原料,通过缩合、环合、氯代反应,得到3种4-苯基-2-氯嘧啶衍生物,进而与苯基哌嗪盐酸盐反应,合成了12种带有不同取代基的2-哌嗪基-4-苯基嘧啶衍生物。该合成方法具有反应时间短、操作简便、副产物少的优点。各步产物均用MS,1H NMR,13C NMR表征。     

2,4—二氨基—5—取代苄基嘧啶类质谱研究

报道了8个2,4-二氨基-5-取代苄基嘧啶衍生物的电子轰击质谱及碰撞活化解离和质量分析离子动能谱.该谱提供了化合物醚键及2,4-二氨基-5-取代苄基嘧啶环的主要碎裂途径,总结了一些裂解规律,将有助于这类化合物的结构推断。     

尿素及硫脲与羰基化合物间的氢键相互作用

利用量子化学二级微扰理论方法对尿素及硫脲衍生物与羰基化合物之间的氢键复合物进行了研究, 在自然键轨道分析基础上进一步揭示了氢键本质并研究了取代基效应. 结果表明, 羰基化合物中供电子基和共轭基, 尿素及硫脲中的吸电子基和共轭基均有利于氢键的形成. 结合尿素与硫脲的催化反应过程, 讨论了氢键复合物两种可能的顺反异构并分析比较了顺反式构象异构体的稳定能大小.     

取代基对腺嘌呤与胸腺嘧啶氢键复合物体系结合能的影响

优化得到了17个取代胸腺嘧啶与腺嘌呤形成的氢键复合物的结构, 并计算了这些复合物的结合能, 探讨了胸腺嘧啶上不同取代基对结合能的影响. 结果表明, CF₃取代的胸腺嘧啶与腺嘌呤间的结合能大于胸腺嘧啶与腺嘌呤间的结合能, 这可能是屈氟尿苷具有阻止病毒及肿瘤扩散功能的原因所在. SO₃H, CN和NO₂取代的胸腺嘧啶与腺嘌呤间具有更大的结合能, 表明这3个基团取代的胸腺嘧啶也可能具有潜在的抗肿瘤作用. 分子中原子理论与自然键轨道分析表明, 在所有体系中, 氢键N—H…N最强, N—H…O=C次之, C—H…O=C最弱, 轨道作用在氢键作用中占有重要地位.     

环双(对-蒽基-对草快)的分子识别与谱学性质

环双(对-蒽基-对草快)是一种新型的缺电子大环仿生主体, 分子识别是其最重要的应用之一. 考察主体对一系列客体分子如水、氨、醇及杂环等的识别能力, 用密度泛函理论(DFT)中的B3LYP/3-21G基组对主客体复合物的结构进行优化. 在B3LYP/6-31G(d)水平上进行单点能计算, 校正后得到复合物的结合能. 用B3LYP/3-21G方法计算13C和3He化学位移. 结果表明, 主体对客体分子的识别主要靠客体上的杂原子与主体上的氢原子之间的氢键进行. 复合物的稳定化能受氢键的数目和距离影响. 氢键的形成导致部分复合物LUMO与HOMO能隙增大, 同时导致与氢键相连的C—H键上C原子的化学位移向低场移动. 复合物的芳香性与其结合能的大小及结合方式有关. 主体的芳香性因其与客体之间的弱相互作用而提高, 但太强的相互作用及客体在主体空腔内都将影响主体的环电流, 从而削弱其芳香性.     

取代基对腺嘌呤与胸腺嘧啶氢键复合物体系结合能的影响简

优化得到了17个取代胸腺嘧啶与腺嘌呤形成的氢键复合物的结构,并计算了这些复合物的结合能,探讨了胸腺嘧啶上不同取代基对结合能的影响. 结果表明,CF3取代的胸腺嘧啶与腺嘌呤间的结合能大于胸腺嘧啶与腺嘌呤间的结合能,这可能是屈氟尿苷具有阻止病毒及肿瘤扩散功能的原因所在. SO3H,CN和NO2取代的胸腺嘧啶与腺嘌呤间具有更大的结合能,表明这3个基团取代的胸腺嘧啶也可能具有潜在的抗肿瘤作用. 分子中原子理论与自然键轨道分析表明,在所有体系中,氢键N—H…N最强,N—H…O=C次之,C—H…O=C最弱,轨道作用在氢键作用中占有重要地位.     

取代基对1-甲基尿嘧啶与N-甲基乙酰胺氢键复合物中氢键强度的影响

使用密度泛函理论B3LYP方法和二阶微扰理论MP2方法对由1-甲基尿嘧啶与N-甲基乙酰胺所形成的氢键复合物中的氢键强度进行了理论研究, 探讨了不同取代基取代氢键受体分子1-甲基尿嘧啶中的氢原子对氢键强度的影响和氢键的协同性. 研究表明: 供电子取代基使N－H…O＝C氢键键长r(H…O)缩短, 氢键强度增强; 吸电子取代基使N－H…O＝C氢键键长r(H…O)伸长, 氢键强度减弱. 自然键轨道(NBO)分析表明: 供电子基团使参与形成氢键的氢原子的正电荷增加, 使氧原子的负电荷增加, 使质子供体和受体分子间的电荷转移量增多; 吸电子基团则相反. 供电子基团使N－H…O＝C氢键中氧原子的孤对电子轨道n(O)对N－H的反键轨道σ^*(N－H)的二阶相互作用稳定化能增强, 吸电子基团使这种二阶相互作用稳定化能减弱. 取代基对与其相近的N－H…O＝C氢键影响更大.     

苯并呋喃酮衍生物结构对其DPPH捕获能力的影响

采用自由基比色法考察苯并呋喃酮衍生物结构对其DPPH捕获能力的影响。结果发现,母体苯环5,7位上甲基和叔丁基的改变以及取代苯环上强供电子取代基的存在对苯并呋喃酮衍生物的DPPH捕获能力没有明显影响。取代苯环2’位存在明显的位阻作用,对苯并呋喃酮衍生物的DPPH捕获能力具有明显的抑制作用：并且当此位为不含活泼氢的氢键受体取代基时,苯并呋喃酮衍生物的DPPH捕获能力会由于取代基与3位活泼氢的氢键作用而被进一步削弱;但此位为含有活泼氢的氢键受体取代基时,此取代基的氢将会由于3位活泼氢与取代基的氢键作用而活化,从而使其位阻作用得到一定程度的抑制。     

具有除草活性的3-(嘧啶基-2)-1,3,4-噁二唑-2(3H)-酮衍生物的设计、 合成与定量构效关系的研究

设计合成了一系列未见文献报道的5-叔丁基-3-[4-取代-5-(氢)甲基嘧啶-2-基]-1,3,4-噁二唑-2(3H)-酮的衍生物, 其结构均经过1H NMR, IR和元素分析表征. 生测结果显示, 部分化合物表现出较好的除草活性. 定量的结构与活性关系研究表明, 它们的除草活性与取代基的立体效应参数和电性参数呈现很好的相关性, 相关系数r大于0.8. 当作用对象为油菜时, 化合物的活性可能主要与取代基R2的邻位立体效应参数Es和电性参数相关; 当作用对象为稗草时, 化合物的活性主要与取代基R2邻位立体效应参数Es和间位取代基电性参数相关.     

嘧啶酮衍生物的微波合成

在微波辅助下,Baylis-Hillman加成物与4-氨基-6-氯嘧啶或2-氨基-噻唑反应,快速合成了两类嘧啶酮衍生物——3-取代-7-氯-4H-嘧啶[1,2-b]哒嗪-4-酮和6-取代-5H-噻唑[3,2-a]嘧啶-5-酮,收率81%～98%,其结构经1H NMR,13C NMR,IR和MS确证。     

The structure and spectra of H-bonded complexes formed by 2-pyridone

The self-assembly complexes formed by 2-pyridone derivatives were theoretically studied by the AM1 and DFT methods to determine their binding energies. The UV, IR, and NMR spectra of the complexes were calculated using the INDO/CIS, AM1, and B3LYP/3-21G methods, respectively. It was shown that the complexes could be formed by two monomers via double hydrogen bonding thanks to the negative binding energy. The affinity for binding was increased by substituents in the monomers. But this stimulating effect depended on the simultaneous influence of the electronic and steric effects. The first absorption bands in the UV spectra of the complexes were blue-shifted relative to that of the monomer because of their larger LUMO-HOMO energy gaps. As hydrogen bonds were formed, the N-H stretching vibrations of the monomers were weakened in the IR spectra of the complexes. And the chemical shifts of the C=C and C≡C carbon atoms were shifted downfield in the ¹³C NMR spectra. The article is published in the original.     

Hydrogen-bonded assembly and binding affinity of the multi-point acceptor and isophthalic acid

Supermolecular complexes formed by oligophenyleneethynylene derivatives and isophthalic acid were studied using AM1 method to obtain binding energy. Electronic spectra and IR spectra of the complexes were calculated by INDO/CIS and AM1 methods based on AM1 geometries. Results indicated that the dimer could be formed by the monomers via hydrogen bonding because of the negative binding energy. Binding energy of the complexes was affected by electronegativity and steric effects of the substituents. The first UV absorptions and IR frequencies of N-H bonds of the complexes were both red-shifted compared with those of the monomers. The complexes could bind small molecules via hydrogen bonds, resulting in the change in UV absorptions and an increase in IR frequencies of N-H bonds.     

Theoretical Study on the Hydrogen Bonding Interactions in Complexes of 5‐Hydroxytryptamine with Water

The energies, geometries and harmonic vibrational frequencies of 1:1 5‐hydroxytryptamine‐water (5‐HT‐H₂O) complexes are studied at the MP2/6‐311++G(d,p) level. Natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM) analyses and the localized molecular orbital energy decomposition analysis (LMO‐EDA) were performed to explore the nature of the hydrogen‐bonding interactions in these complexes. Various types of hydrogen bonds (H‐bonds) are formed in these 5‐HT‐H₂O complexes. The intermolecular C4H5^5‐HT···O^w H‐bond in HTW3 is strengthened due to the cooperativity, whereas no such cooperativity is found in the other 5‐HT‐H₂O complexes. H‐bond in which nitrogen atom of amino in 5‐HT acted as proton donors was stronger than other H‐bonds. Our researches show that the hydrogen bonding interaction plays a vital role on the relative stabilities of 5‐HT‐H₂O complexes.     

A TD-DFT study on the hydrogen bonding of three esculetin complexes in electronically excited states: strengthening and weakening

Time-dependent density functional theory (TD-DFT) method was used to study the excited-state hydrogen bonding of three esculetin complexes formed with aprotic solvents. The geometric structures, molecular orbitals (MOs), electronic spectra and the infrared (IR) spectra of the three doubly hydrogen-bonded complexes formed by esculetin and aprotic solvents dimethylsulfoxide (DMSO), tetrahyrofuran (THF) and acetonitrile (ACN) in both ground state S(0) and the first singlet excited state S(1) were calculated by the combined DFT and TD-DFT methods with the COSMO solvation model. Two intermolecular hydrogen bonds can be formed between esculetin and the aprotic solvent in each hydrogen-bonded complex. Based on the calculated bond lengths of the hydrogen bonds and the groups involved in the formation of the intermolecular hydrogen bonds in different electronic states, it is demonstrated that one of the two hydrogen bonds formed in each hydrogen-bonded complex is strengthened while the other one is weakened upon photoexcitation. Furthermore, it is found that the strength of the intermolecular hydrogen bonds formed in the three complexes becomes weaker as the solvents change from DMSO, via THF, to ACN, which is suggested to be due to the decrease of the hydrogen bond accepting (HBA) ability of the solvents. The spectral shifts of the calculated IR spectra further confirm the strengthening and weakening of the intermolecular hydrogen bonds upon the electronic excitation. The variations of the intermolecular hydrogen bond strengths in both S(0) and S(1) states are proposed to be the main reasons for the gradual spectral shifts in the absorption and fluorescence spectra both theoretically and experimentally.     

Two silver(I) complexes with bis(benzimidazole)‐2‐oxopropane ligands: Syntheses,crystal structures and DNA binding studies

Two Ag(I) complexes, [Ag₂(bobb)₂]⋅(NO₃)₂ ( 1 ) and [Ag₂(crotonate)₂(aobb)]_n ( 2 ) (bobb =1,3‐bis(1‐benzylbenzimidazol‐2‐yl)‐2‐oxapropane; aobb =1,3‐bis(1‐allylbenzimidazol‐2‐yl)‐2‐oxopropane), have been synthesized and characterized using elemental analysis, electrical conductivities, infrared and UV–visible spectral measurements and single‐crystal X‐ray diffraction. Complex 1 is binuclear and three‐coordinated by two N atoms from two bobb ligands, while complex 2 is a unique metal organic compound with diamond‐like multinuclear Ag centers with each Ag bridged by two aobb ligands and two crotonate ions to form one‐dimensional single polymer chain structures and extended into two‐dimensional frameworks through π–π and intermolecular C─H⋅⋅⋅O hydrogen bonds. The adjacent Ag(I) centers are bridged by allyl from aobb which is not only a σ‐bonding ligand, but also a π‐acid ligand. The DNA binding modes of complexes 1 and 2 were investigated using electronic absorption titration, fluorescence spectra and viscosity measurements. The results suggest that the two complexes bind to DNA via an intercalative mode, and their binding affinity for DNA follows the order 2  >  1 . This is due to the chelating effects which can enhance the planar functionality of the metal complexes.     

Excited‐State Hydrogen Bonding Strengthening and Weakening with Intramolecular Charge Transfer in Resorufin‐Water Complexes: A TD‐DFT Study

The geometric structures, infrared spectra and hydrogen bond binding energies of the various hydrogen‐bonded Res^?‐water complexes in states S0 and S1 have been calculated using the density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) methods, respectively. Based on the changes of the hydrogen bond lengths and binding energies as well as the spectral shifts of the vibrational mode of the hydroxyl groups, it is demonstrated that hydrogen bonds HB‐II, HB‐III and HB‐IV are strengthened while hydrogen bond HB‐I is weakened in the four singly hydrogen‐bonded Res^?‐Water complexes upon photoexcitation. When the four hydrogen bonds are formed simultaneously between one resorufin anion and four water molecules in the Res^?‐4Water complex, all the hydrogen bonds are weakened in both the ground and excited states compared with those in the corresponding singly hydrogen‐bonded Res^?‐Water complexes. Furthermore, in complex Res^?‐4Water, hydrogen bonds HB‐II and HB‐IV are strengthened while hydrogen bonds HB‐I and HB‐III are weakened after the electronic excitation. The hydrogen bond strengthening and weakening in the various hydrogen‐bonded Res^?‐water complexes should be due to the redistribution of the charges among the four heteroatoms (O_1‐3 and N₁) within the resorufin molecule upon the optical excitation.     

Theoretical study of the interaction of fluorinated dimethyl ethers and the ClF and HF molecules. Comparison between halogen and hydrogen bonds

A theoretical study of the halogen‐bonded complexes formed between fluorinated dimethyl ethers (n_F = 0–4) and ClF is carried out using the wB97XD method combined with the 6‐311++G(d,p) basis set. The properties of the complexes are compared with the corresponding properties of the hydrogen‐bonded complexes formed between the same electron donors and HF. The optimized geometries, the interaction energies, relevant natural bonding orbital characteristics along with some vibrational data are calculated. The analyzed properties also include the symmetry adapted perturbation theory decomposition of the energies along with the atoms‐in molecule analysis. For both the halogen and hydrogen bonds, the interaction energies are ruled by the intermolecular hyperconjugation energies. In contrast, the correlations between the binding energies and the basic properties of the ethers or the charge transfer are different for the halogen and hydrogen bonds. The applicability of the Bent's rule to these systems is discussed. © 2016 Wiley Periodicals, Inc.     

Structures,vibrational frequencies,topologies, and energies of hydrogen bonds in cysteine‐formaldehyde complexes

The hydrogen bonding interactions between cysteine (Cys) and formaldehyde (FA) were studied with density functional theory regarding their geometries, energies, vibrational frequencies, and topological features of the electron density. The quantum theory of atoms in molecules and natural bond orbital analyses were employed to elucidate the interaction characteristics in the Cys‐FA complexes. The intramolecular hydrogen bonds (H‐bonds) formed between the hydroxyl and the N atom of cysteine moiety in some Cys‐FA complexes were strengthened because of the cooperativity. Most of intermolecular H‐bonds involve the O atom of cysteine/FA moiety as proton acceptors, while the strongest H‐bond involves the O atom of FA moiety as proton acceptor, which indicates that FA would rather accept proton than providing one. The H‐bonds formed between the CH group of FA and the S atom of cysteine in some complexes are so weak that no hydrogen bonding interactions exist among them. In most of complexes, the orbital interaction of H‐bond is predominant during the formation of complex. The electron density (ρ_b) and its Laplace (?²ρ_b) at the bond critical point significantly correlate with the H‐bond parameter δR, while a linearly relationship between the second‐perturbation energy E(2) and ρ_b has been found as well. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Density functional theory and topological analysis on the hydrogen bonding interactions in cysteine‐thymine complexes

Hydrogen bonding interactions between amino acids and nucleic acid bases constitute the most important interactions responsible for the specificity of protein binding. In this study, complexes formed by hydrogen bonding interactions between cysteine and thymine have been studied by density functional theory. The relevant geometries, energies, and IR characteristics of hydrogen bonds (H‐bonds) have been systematically investigated. The quantum theory of atoms in molecule and natural bond orbital analysis have also been applied to understand the nature of the hydrogen bonding interactions in complexes. More than 10 kinds of H‐bonds including intra‐ and intermolecular H‐bonds have been found in complexes. Most of intermolecular H‐bonds involve O (or N) atom as H‐acceptor, whereas the H‐bonds involving C or S atom usually are weaker than other ones. Both the strength of H‐bonds and the structural deformation are responsible for the stability of complexes. Because of the serious deformation, the complex involving the strongest H‐bond is not the most stable structures. Relationships between H‐bond length (ΔR_X‐H), frequency shifts (Δv), and the electron density (ρ_b) and its Laplace (?²ρ_b) at bond critical points have also been investigated. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011