2-硫代黄嘌呤互变异构体的密度泛函理论计算

在密度泛函B3LYP/6-311G**水平上,对14种气相和水相中可能存在的2-硫代黄嘌呤互变异构体进行了几何构型全自由度优化,并计算出它们的总能量、焓、熵、吉布斯自由能.Onsager反应场溶剂模型用于水相的计算.计算结果表明,2-硫代黄嘌呤在气相和水相中主要以酮式结构形式存在,与已有实验结果一致.在气相和水相中,酮式结构—N(7)(H)均比酮式结构—N(9)(H)更稳定.2-硫代黄嘌呤互变异构的熵效应小,对互变异构平衡没有显著的影响,而焓变对互变异构却产生了主要的影响.水溶剂化自由能与异构体的气相偶极矩存在相关性.另外,较详细地考察了2-硫代黄嘌呤与6-硫代黄嘌呤的相对稳定性.     

6-硫代黄嘌呤互变异构体的密度泛函理论计算

在密度泛函B3LYP/6-311G**水平下,对14种气相和水相中可能存在的6-硫代黄嘌呤异构体进行了几何构型的全自由度优化,并计算出它们的总能量、焓、熵、吉布斯自由能。Onsager反应场溶剂模型用于水相的计算.计算结果表明,6-硫代黄嘌呤在气相中和水相中主要以硫酮的形式存在.在气相和水相中,硫酮-N7(H)均比硫酮-N9(H)更稳定.计算结果同已有实验结果一致.6-硫代黄嘌呤异构化的熵效应小,对互变异构平衡几乎没有显著的影响,而焓变对互变异构产生了主要的影响.较详细地讨论了水溶剂化作用对异构体的能量、几何结构、电荷分布和偶极矩的影响.     

2,6-二巯基嘌呤互变异构体热力学稳定性的密度泛函理论研究

利用密度泛函(DFT)B3LYP/6-311G(d,p)方法,水相计算采用自洽反应场(SCRF)中的Onsager模型,对气相和水相中可能存在的13种2,6-二巯基嘌呤互变异构体进行了全优化,并计算了各异构体的热力学参数、偶极矩及原子净电荷。计算结果表明,不论是气相还是水相,二硫酮DTP(1,3,7)是最稳定的异构体。溶剂化效应使各异构体的稳定性均增强,偶极矩大者其稳定性显著增大。溶剂化吉布斯自由能与异构体在两相中偶极矩之差存在相关性。二硫酮DTP(1,3,7)在水相中与致癌物BPDE进行亲核取代反应时,二硫酮DTP(1,3,7)中的S10原子优先进攻亲电试剂BPDE.     

金属离子(Na~+、K~+、Ca~(2+)、Mg~(2+)、Zn~(2+))与鸟嘌呤异构体配合物的稳定性

在B3LYP/6-311++G**水平上用极化连续介质模型(PCM)系统研究了金属离子(M+/2+=Na+,K+,Ca2+,Mg2+,Zn2+)和十三种鸟嘌呤异构体形成的配合物GnxM+/2+(n为鸟嘌呤异构体的编号,x表示M+/2+与鸟嘌呤异构体的结合位点)在气(g)液(a)两相中的稳定性顺序.着重探讨了液相中配合物的稳定性差异,并且从溶质-溶剂效应、结合能、形变能及异构体的相对能量等几个方面分析了造成稳定顺序发生变化的原因.报道了溶液中这五种金属离子与鸟嘌呤异构体结合形成的六种基态配合物:aG1N2,N3Na+,aG1N2,N3K+,aG1O6,N7Ca2+,aG1N2,N3Mg2+(aG1O6,N7Mg2+),aG2N3,N9Zn2+.可以看出,除了在Zn2+配合物中鸟嘌呤异构体为G2外,构成其余四种金属离子配合物的鸟嘌呤异构体都是G1,但结合位点不同.同时对气相中各类配合物稳定性也进行了系统的排序,并报道了几种较稳定的配合物,如:gG3N1,O6K+,gG5N1,O6K+,gG3N1,O6Ca2+/Mg2+,gG4O6,N7Ca2+/Mg2+.     

C_(59)F_(2n)HN(n=1,2)异构体的结构与稳定性的理论研究

分别用MNDO和AM1两种半经验方法,对C59F2nHN (n = 1, 2) 的异构体进行几何构型全优化,结合频率分析及HF/6-31G单点能计算,确定了各异构体的基态结构及其相对稳定性。计算结果表明,C59HN的F加成物的立体选择性规律与C60的不同,最稳定异构体不是1-2加成物。C59F2HN的最稳定异构体是1-4加成的6, 18-或12, 15-异构体; C59F4HN的最稳定异构体是1-4,1-4加成的6, 18; 12, 15-异构体,其能量远小于其它各异构体的能量。N原子取代碳笼骨架C原子后,改变了碳笼F加成物的立体选择性规律。     

硫、氮双齿配体与Cd(II)和Hg(II)配合物的合成与表征

以HMFC[(反)-肉桂酰基二茂铁缩(S)-甲基二硫代碳酰腙]与HBFC[(反)-肉桂酰基二茂铁缩(S)-苄基二硫代碳酰腙]两种Schiff碱分别与醋酸镉[Cd(OAc)₂•2H₂O]、醋酸汞[Hg(OAc)₂]反应, 合成了6个未见文献报道的配合物Cd(MFC)₂•H₂O, Cd(MFC)•OAc, Cd(BFC)₂, Hg(MFC)₂, Hg(MFC)•OAc, Hg(BFC)₂, 考察了其物理性质, 并利用元素分析、IR, ¹H NMR及摩尔电导表征了其组成、可能结构, 推断了配位过程. 结果表明: 这两种Schiff 碱都是反式双齿配体, 经烯硫醇化并失去质子后, 以负硫离子与过渡金属离子形成共价键, 氮原子与中心金属离子形成配位键.     

新型两亲性混配钌配合物的合成及其对Hg2+的选择性“肉眼”识别

采用与文献不同的路线合成了4,4′-二(p-甲基苯基)-2,2′-二联吡啶,与文献结果相比,总收率由4.0%提高至15.3%.该化合物和4,4′-二羧基-2,2′-二联吡啶组成混合配体与金属钌配位,合成了两亲性、混配型配合物cis-N,N-4,4′-二(p-甲基)苯基-2,2′-二联吡啶-N,N-4,4′-二羧基-2,2′-二联吡啶-N,N-二异硫氰钌配合物,并用IR,UV-Vis,NMR和Maldi-TOF等手段进行表征.将该两亲性混配钌配合物首次用于对Hg2+的识别中,发现此配合物对Hg2+表现出灵敏的选择性“肉眼”识别:在DMF/乙醇溶液(体积比1∶9)中加入Hg2+后,MLCT态吸收由530nm蓝移到485nm.该配合物与Hg2+以1∶1(摩尔比)结合,检测限可低至0.5×10-6mol/L.     

[Hg(C5H4S5)I2]2的合成与晶体结构(C5H4S5 = 4,5-亚乙基二硫杂-1,3-二硫杂-2-硫酮)

用 HgI2 和 4,5-亚乙基二硫杂-1,3-二硫杂-2-硫酮 (C5H4S5)反应,合成一种二核汞配合物[Hg(C5H4S5)I2]2 1。X 射线衍射结果表明,晶体属于单斜晶系,C2/c 空间群,晶胞参数 a =21.6847(1),b = 8.5125(4),c = 15.6699(8),a=112.7850(1)°,V=2666.8(2) ?3。Mr = 1357.54,Z = 4,Dx = 3.381 g/cm3,ì = 16.913 cm–1,F(000) = 2400,R=0.0639,wR=0.1711,S=1.052。配合物 1 具有二聚体结构,2 个汞原子通过 2 个碘原子桥联,形成 1 个 Hg2I2菱形平面,汞原子周围的配位是四面体结构,通过分子间的硫…硫作用和碘…硫作用,形成准二维超分子网络。 S S S H g I I S S S S I I H g S     

[Si,N,C,O]2+异构体结构、相对稳定性与解离

在UB3LYP/6-311G(d)和UCCSD(T)/6-311 + G(2df)(单点)水平下得到了[Si, N, C,O]²⁺体系的15种异构体, 对它们的结构进行了分析, 并给出了能量较低的离子碎片方式. 计算结果表明线型异构体SiNCO²⁺ (²Π )是[Si,N,C,O]²⁺体系中热力学最稳定的物种, 其次是线型的SiOCN²⁺(²Π ), SiCNO²⁺(²Π )和含NCO三元环的异构体SiC(NO)(²A″ ). 几个动力学相对较稳定的异构体的稳定性顺序为SiNCO²⁺> SiCNO²⁺(²Π )> SiOCN²⁺> SiC(NO)²⁺ >OSiNC²⁺(²Π ). 对异构化过程及离子碎片方式的分析结果说明线型异构体SiNCO²⁺是相关质谱实验中的主要物种, 而且是亚稳态的, 在质谱条件下可以解离成离子碎片.     

硫、氮双齿配体与Cd(II)和Hg(II)配合物的合成与表征

以HMFC[(反)-肉桂酰基二茂铁缩(S)-甲基二硫代碳酰腙]与HBFC[(反)-肉桂酰基二茂铁缩(S)-苄基二硫代碳酰腙]两种Schiff碱分别与醋酸镉[Cd(OAc)2?2H2O]、醋酸汞[Hg(OAc)2]反应,合成了6个未见文献报道的配合物Cd(MFC)2?H2O,Cd(MFC)OAc,Cd(BFC)2,Hg(MFC)2,Hg(MFC)OAc,Hg(BFC)2,考察了其物理性质,并利用元素分析、IR,1HNMR及摩尔电导表征了其组成、可能结构,推断了配位过程.结果表明:这两种Schiff碱都是反式双齿配体,经烯硫醇化并失去质子后,以负硫离子与过渡金属离子形成共价键,氮原子与中心金属离子形成配位键.     

Substituted 2-methyl- and 2-methyleneindolines. 2. Nitro- and amino-substituted 2-methyl- and 2-methylene-indolines

From 5- and 6-aminotetramethylindolines, 2-methyleneindolines have been synthesized; these compounds can be condensed with other heterocyclic systems. The nitration of 1,2,3,3-tetramethylindoline under different conditions was studied.For communication 1, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 919–923, July, 1989.     

Sc2MgGa2 and Y2MgGa2

Scandium magnesium gallide, Sc₂MgGa₂, and yttrium magnesium gallide, Y₂MgGa₂, were synthesized from the corresponding elements by heating under an argon atmosphere in an induction furnace. These intermetallic compounds crystallize in the tetragonal Mo₂FeB₂‐type structure. All three crystallographically unique atoms occupy special positions and the site symmetries of (Sc/Y, Ga) and Mg are m2m and 4/m, respectively. The coordinations around Sc/Y, Mg and Ga are pentagonal (Sc/Y), tetragonal (Mg) and triangular (Ga) prisms, with four (Mg) or three (Ga) additional capping atoms leading to the coordination numbers [10], [8+4] and [6+3], respectively. The crystal structure of Sc₂MgGa₂ was determined from single‐crystal diffraction intensities and the isostructural Y₂MgGa₂ was identified from powder diffraction data.     

2-stannaindenes and 2-stannaindanes

Condensation of o-xylylene bis(triphenylphosphorane) 4 with [(Me₃Si)₂N]₂Sn yields the 1,3-bis(triphen-ylphosphoranediyl)-2σ²-stannaindene 2 , which is orange as a solid and red in solution and which demonstrates stannylene reactivity. Alkyl bromides andiodides add to 2 to give the corresponding 2σ⁴-stannaindanes. In the reaction with PCl₃, the tin atom in 2 is replaced by a phosphenium ring member. A secondary product in the preparation of 2 is the spirocyclic 2σ⁴-stannaindane 12. Its structure has been determined by X-ray analysis. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:103–108, 1998     

Structure and properties of single crystalline CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2

Single crystals of CaMg(2)Bi(2), EuMg(2)Bi(2), and YbMg(2)Bi(2) were obtained from a Mg-Bi flux cooled to 650 °C. These materials crystallize in the CaAl(2)Si(2) structure-type (P ?3m1, No. 164), and crystal structures are reported from refinements of single crystal and powder X-ray diffraction data. EuMg(2)Bi(2) displays an antiferromagnetic transition near 7 K, which is observed via electrical resistivity, magnetization, and specific heat capacity measurements. Magnetization measurements on YbMg(2)Bi(2) reveal a weak diamagnetic moment consistent with divalent Yb. Despite charge-balanced empirical formulas, all three compounds are p-type conductors with Hall carrier concentrations of 2.0(3) × 10(19) cm(-3) for CaMg(2)Bi(2), 1.7(1) × 10(19) cm(-3) for EuMg(2)Bi(2), and 4.6(7) × 10(19) cm(-3) for YbMg(2)Bi(2), which are independent of temperature to 5 K. The electrical resistivity decreases with decreasing temperature and the resistivity ratios ρ(300 K)/ρ(10 K) ≤ 1.6 in all cases, indicating significant defect scattering.     

Homopolymerization of 2-alkyl- and 2-aryl-2-oxazolines

2-Aryl- and 2-alkyl-2-oxazolines have been polymerized to poly-(N-aroyl)aziridines and poly(N-acyl)aziridines, respectively, in the presence of boron trifluoride. The polymers obtained were glassy, light yellow resins with molecular weights ranging from 3500 to 7500 (35–50 oxazoline units per chain). The polymerization rates have been determined for several of these monomers. A polymerization mechanism is proposed.     

The alkali hypophosphites KH2PO2, RbH2PO2 and CsH2PO2

The structures of the hypophosphites KH₂PO₂ (potassium hypophosphite), RbH₂PO₂ (rubidium hypophosphite) and CsH₂PO₂ (caesium hypophosphite) have been determined by single‐crystal X‐ray diffraction. The structures consist of layers of alkali cations and hypophosphite anions, with the latter bridging four cations within the same layer. The Rb and Cs hypophosphites are isomorphous.