取代螺环戊烷的电子轰击和化学电离正,负离子质谱

本文报道了苯取代螺环戊烷衍生物的电子轰击(EI)正离子和化学电离正、负离子(PNCI)质谱。通过亚稳离子测定,研究了该类化合物的裂解机理。在卤代螺环戊烷的EI质谱中,分子离子峰都很弱,甚至不出现M 离子。其特征离子为[M-X]~ 、[M-2X] 和[M-X-HX]~ 。CI正离子谱有较强的[M H]~ 、[M-2X]~ 和[M-x]~ ,CI负离子谱的特征离子为[M X]~-,它们在多数情况下为基峰离子,另外还出现HX_2~-或X~-离子。     

某些寡肽场解吸质谱的研究

本文阐述了几个寡肽的场解吸质谱。根据四个标准二肽场解吸质谱的裂解规律对四个合成肽进行了鉴定。这些肽的场解吸质谱不仅获得了高强度的分子离子M~+或[M+1]~+、[M+2]~+而且获得了部分序列信息。     

若干糖苷类化合物的负离子化学电离质谱研究

本文报道苦玄参苷类(picfeltarraenins)(1～5)、膜荚黄芪苷类(astramembrannins)(6～8)、雪胆素苷类(hemsamabilinins)(9,10)及其O-乙酰衍生物(11,12)和洋地黄毒苷(digitoxin)(13)的负离子化学电离质谱.用甲烷和二氯甲烷作为混合反应气,获得了满意的结果.谱中有特征的M~(?)或[M-1]~-,[M+Cl]~-和一系列脱糖基的碎片离子[M+Cl-nR]~-(R为不同类型的糖基)及糖基碎片离子[R+Cl]~-.乙酰化的糖苷还给出[M+Cl-nCH_2CO]~-或[M+Cl-nCH_3COOH]~-等碎片离子.     

石油芳烃组分中未知化合物——三叔丁基苯基磷酸酯的高分辨质谱分析

将大气压光电离(APPI)、电喷雾(ESI)、实时直接分析(DART)多种电离源和傅立叶变换离子回旋共振质谱(FT-ICR MS)联用对石油芳烃样品中的未知化合物进行研究。通过高分辨质谱的精确质量,结合碰撞诱导解离(CAD)技术,经分析并与文献标准物质谱图比对,推断未知物为三(2,4-二-叔丁基苯基)磷酸酯(TDTBPP),并研究了其在不同大气压电离源中的电离特性。APPI谱图中主要为[M+H]~+峰,同时存在M.~+峰。ESI谱图中主要为[M+Na]~+(不加甲酸)或[M+NH4]~+峰(加甲酸)。DART谱图中主要为[M+NH4]~+峰,而EI谱图中基峰为m/z 57(叔丁基),次强峰为[M-CH3]~+峰。     

烷基乙二胺-CF_3CO_2型质子化离子液体的分子间氢键作用

利用密度泛函理论M06-2X方法,在6-311G(d,p)水平下,对由N-烷基乙二胺阳离子[HAlkyl]~+(Alkyl=Hex,Oct,Et Hex)与三氟乙酸阴离子[TFA]~-形成的[HHex][TFA],[HOct][TFA]及[HEtHex][TFA]型质子化离子液体(PILs)的离子对进行了理论研究.通过几何优化和分子振动频率分析3种PILs均得到5种较稳定构型[HAlkyl][TFA]S1~S5.结果表明,[HAlkyl]~+与[TFA]~-间发生了质子转移形成了O—H…N型氢键.3种PILs的基组重叠误差校正后的分子间相互作用能(ΔE_(int)~(BSSE))在-449.91~-522.87 kJ/mol范围内.由于分子间形成了较强的O—H…N氢键作用,引起N—H振动频率消失,在2200~2700 cm~(-1)范围内出现了较强的O—H键振动.通过自然键轨道(NBO)及分子中原子(AIM)理论计算,研究了分子间氢键作用的相对强度及其对分子构型稳定性的影响.NBO分析结果表明,其稳定化能主要源自于[HAlkyl]的氨基中孤对电子LP(N)与[TFA]中O—H反键轨道σ*(H—O)间的相互作用,即LP(N)→σ*(H—O).并探讨了阳离子部位[HAlkyl]~+的质子化位置以及烷基链长、支链的引入对[HAlkyl]与[TFA]间氢键作用强度的影响.     

第五.六族元素的有机化合物在有机合成中应用的研究XXXXI.一些新的含氟膦叶立德衍生物的质谱研究

前文已报道了一些含氟膦叶立德衍生物的电子轰击(EI)和化学电离正、负离子(PCI、NCI)质谱,着重对化学电离的正、负离子的断裂机理进行了研究.在CI正离子谱中[M+H]~+为基峰,而CI负离子谱中出现稳定的[M—C_6H_5]~-离子. 关于一般膦叶立德的EI质谱已有报道,在正离子谱中出现各种骨架重排离子.重排机理文献中也有详细讨论.本文继续报道一些新的含氟膦叶立德的EI质谱,它们的断裂机     

环丙烷衍生物在D2O离子体系中的H/D交换反应

在D2O化学反应气条件下研究了环丙烷衍生物的H/D交换反应特性.发现了三种新的产物离子[M+1]+、[M+2]+和[M+3]+.应用碰撞诱导碎裂(CID)技术研究了这些离子的碎裂反应特性.实验结果表明三种新的产物离子是由反应物与试剂离子之间发生H/D交换反应生成的.并获得了环丙烷衍生物结构中活泼氢位置及其数量的信息.     

92种工业染料在四极杆/静电场轨道阱高分辨质谱中的离子化规律

采用四极杆/静电场轨道阱高分辨质谱,通过正负离子快速切换的全扫描分析,实现了对92种工业染料的分子离子峰的离子化规律的探究。结果表明:碱性染料中氯或硫元素的存在状态决定了染料分子离子峰的存在形式,其中,氯元素以氯化氢形式存在的含氯染料是通过丢掉氯化氢形成[~*M+H]~+分子离子峰,氯元素以Cl~-存在且含有强极性基团(分子中氮原子呈现带有4个键的正离子状态)的染料分子离子峰通过丢掉Cl~-后形成[~*M]~+分子离子峰;对于含有硫元素的碱性染料,当硫元素是以HSO_4~-的形式存在且含有强极性基团(分子中氮原子呈现带有4个键的正离子状态)的碱性染料是通过丢掉HSO_4~-形成[~*M]~+分子离子峰;酸性染料准分子离子峰的类型与分子结构中Na~+、磺酸基的数目相关,倾向失去所有的Na~+,从溶剂中获得氢原子结合在磺酸基上,形成一系列[(M-xNa+yH)/(x-y)]~-离子,含有多个磺酸基染料的多以二价准分子离子峰为基峰;苏丹染料和分散染料作为含电负性基团的弱极性染料,更易形成[M+H]~+分子离子峰。     

两个含双磺酸基团化合物的合成、晶体结构及荧光性质(英文)

采用缓慢蒸发溶剂法在水中合成了2个含双磺酸基的化合物A-2,5-DSA·(Hphen)2·2H2O(1)和[Co(phen)2(H2O)2]·(A-2,5-DSA)·3H2O(2)(A-2,5-DSA=苯胺-2,5-二磺酸根离子,phen=1,10-邻菲罗啉)。化合物1中,相邻的质子化的1,10-邻菲罗啉反向堆叠在一起,水分子通过氢键与(Hphen)+和苯胺-2,5-二磺酸根离子相连,形成二维的层状结构。化合物2中,钴离子与2个1,10-邻菲罗啉和2个水分子配位,构成[Co(phen)2(H2O)2]2+阳离子。3个自由的水分子通过氢键将苯胺-2,5-二磺酸根离子和[Co(phen)2(H2O)2]2+连接形成三维网状结构。两个化合物中苯胺-2,5-二磺酸根离子均起到平衡电荷的作用。室温下2个化合物均具有荧光性质,其最大发射峰分别在601 nm和441 nm。     

环丙烷衍生物在CD3OD离子体系中的H/D交换反应

研究了环丙烷衍物生物在CD3OD离子体系中的H/D交换反应产物离子[M 1]^*,[M 2]^ 和[M 3]^*的碰撞诱民碎裂(CID)反应特征,实验结果表明这些产物离子是由反应物与试剂离子之间生H/D交换反应生成的,获得了环丙烷衍生物结构中活泼氢位置及其数量的信息.     

Protonation and Dehydrogenation During the Multiphoton Ionization of the Cluster: C_4H_5N(H_2O)_n

Proton transfer process in hydrogen-bonded clusters has attracted great interest of many chemists in physical chemistry and biochemistry1-5. Pyrrole (C4H5N) is one of the building blocks of some important biomolecules6. And pyrrole is a compound of five-membered hetero-cyclic aromatic ring, in which a lone pair of electrons offered by the N atom and the two double bonds form a delocalized big ( bond. In this paper we report on the observations for the cluster system pyrrole-water by use of a…     

Effective solvation of alkaline earth ions by proline-rich proteolytic peptides of galectin-3 upon electrospray ionisation

In an analysis of a combined chymotrypsin/AspN digest of galectin-3 by positive ion nano-electrospray ionisation mass spectrometry (nanoESI-MS) several peptides were observed which showed metal adduct ions as their most abundant ion signals. The most prominent adduct ions were observed at m/z values corresponding to [M+40]2+, [M+41]3+, and [M+42]4+ ions. Detailed investigation of the [M+40]2+ ion of the peptide GAPAGPLIVPY showed that it was not, as originally expected, a [M+H+39K]2+ adduct ion but had the composition [M+40Ca]2+. This was verified by several approaches: (i) nanoESI-MS/MS of the [M+Ca]2+ adduct ions resulted in the virtually exclusive formation of doubly charged fragment ions; (ii) mass determination by quadrupole time-of-flight (QTOF)-MS provided a preliminary identification; and (iii) accurate mass measurement using nanoESI Fourier transform ion cyclotron resonance (FTICR)-MS at a mass resolving power of 500 000 allowed the specific detection and identification of the isobaric ion pairs [M+40Ca]2+/[M+H+39K]2+ and [M+24Mg]2+/[M+H+23Na]2+. All peptides in the chymotryptic galectin-3 digest without a basic residue (K or R) showed addition of calcium as the most prominent ionisation principle. A further common feature of these nonbasic peptides was the presence of several proline residues, which is assumed to be a factor promoting the intense addition of calcium. It was observed that the common trace levels of sodium and calcium in analytical grade solvents (about 1-10 microM) are sufficient to generate the [M+H+23Na]2+ and [M+40Ca]2+ ions as the most prominent species of the peptide GAPAGPLIVPY. We conclude that the sequence motifs P-XX-P and P-XXX-P favour the solvation of alkaline earth ions in ESI-MS. In view of the successful detection of physiological Ca/protein interactions by ESI-MS, this finding may point to a solvation of Ca2+ by galectin in solution. The findings open new routes of research in the study of metal/protein and metal/peptide interactions     

Ionization and collision-induced fragmentation of N-linked and related carbohydrates using divalent cations

Maltoheptaose and several N-linked glycans were ionized by electrospray as adducts with the divalent cations Mg2+, Ca2+, Mn2+, Co2+ and Cu2+. [M + metal]2+ ions were the major species in all cases with calcium giving the highest sensitivity. In addition, copper gave [M + Cu]+ ions. Other cations gave singly charged ions only by elimination of a protonated monosaccharide. Fragmentation of the [M + metal]2+ ions produced both singly and doubly charged ions with the relative abundance of doubly charged ions decreasing in the order Ca > Mg > Mn > Co > Cu. Singly charged ions were formed by elimination of a protonated monosaccharide residue followed, either by successive monosaccharide residue losses, or by a 2,4A cross-ring cleavage of the reducing-terminal monosaccharide. Formation of doubly charged fragments from [M + metal]2+ ions involved successive monosaccharide-residue losses either with or without O,2A or 2,4A cross-ring cleavages of the reducing-terminal monosaccharide. Abundant diagnostic doubly charged ions formed by loss of the 3-antenna from the O,2A cross-ring product were specific to [M + Ca]2+ ions. Fragmentation of [M + Cu]+ ions was similar to that of the corresponding [M + H]+ ions in that most cross-ring fragments were absent.     

Density functional theory-based prediction of some aqueous-phase chemistry of superheavy element 111. Roentgenium(I) is the "softest" metal ion

A previous approach (Hancock, R. D.; Bartolotti, L. J. Inorg. Chem. 2005, 44, 7175) using DFT calculations to predict log K1 (formation constant) values for complexes of NH3 in aqueous solution was used to examine the solution chemistry of Rg(I) (element 111), which is a congener of Cu(I), Ag(I), and Au(I) in Group 1B. Rg(I) has as its most stable presently known isotope a t(1/2) of 3.6 s, so that its solution chemistry is not easily accessible. LFER (Linear free energy relationships) were established between DeltaE(g) calculated by DFT for the formation of monoamine complexes from the aquo ions in the gas phase, and DeltaG(aq) for the formation of the corresponding complexes in aqueous solution. For M2+, M3+, and M4+ ions, the gas-phase reaction was [M(H2O)6]n+(g) + NH3(g) = [M(H2O)5NH3]n+(g) + H2O(g) (1), while for M+ ions, the reaction was [M(H2O)2]+(g) + NH3(g) = [M(H2O)NH3]+(g) + H2O(g) (2). A value for DeltaG(aq) and for DeltaE for the formation of M = Cu2+ in reaction 1, not obtained previously, was calculated by DFT and shown to correlate well with the LFER obtained previously for other M2+ ions, supporting the LFER approach used here. The simpler use of DeltaE values instead of DeltaG(aq) values calculated by DFT for formation of monoamine complexes in the gas phase leads to LFER as good as the DeltaG-based correlations. Values of DeltaE were calculated by DFT to construct LFER with M+ = H+, and the Group 1B metal ions Cu+, Ag+, Au+, and Rg+, and with L = NH3, H2S, and PH3 in reaction 3: [M(H2O)2]+(g) + L(g) = [M(H2O)L]+g) + H2O(g) (3). Correlations involving DeltaE calculated by DMol3 for H+, Cu+, Ag+, and Au+ could reliably be used to construct LFER and estimate unknown log K1 values for Rg(I) complexes of NH3, PH3, and H2S calculated using the ADF (Amsterdam Density Functional) code. Log K1 values for Rg(I) complexes are predicted that suggest the Rg(I) ion to be a very strong Lewis acid that is extremely "soft" in the Pearson hard and soft acids and bases sense.     

铌硫簇离子的激光产生与质谱分析

黄建全、卢嘉锡等提出的[MO_3S_4]~(4+)簇骼中Mo_3S_3簇环具有类芳香性本质的观点,已逐渐为国内外化学者所接受。围绕着这一思想,我们最近在自制的仪器上进行了铌与硫的激光等离子体反应。在高温的激光等离子体中,各种物种一般皆有较高的内能,所以只有结构很稳定的化合物离子才可能较大量地生存下来,为质谱计所检测。铌仅比钼少一个价电子,Nb_3S_4~(4+)与[MO_3S_4]~(4+)是等电子的,铌与钼为同一周期的相邻元素,所以Nb_3S_4~+很可能也同样具有类芳香性的Nb_3S_3簇环,结构比较稳定。如果是这样的话,它应当在激光等离子体质谱中有突出的信号强度。我们的实验结果正是如此。     

四硫氰合钴(Ⅱ)酸钡的18-冠-6配合物的研究

制备了四硫氰合钴(Ⅱ)酸钡的18—冠—6配合物,确定了它的组成,对它进行了红外光谱、质谱、热分析等多项物现性能的测试,并将测试结果结合已测定的配合物的结构进行了讨论。     

Inorganic crown: the host-guest chemistry of a high nuclearity 'Celtic-ring' isopolyoxotungstate [H12W36O120]12-

A range of complexes based on the high-nuclearity [W36] isopolyoxotungstate cluster, [H12W36O120]12-, with a triangular topology has been isolated by using the organic cation, protonated triethanolamine. In analogy to an 18-crown-6 crown ether with six oxygen donors on a ring, the cluster can form alkali and alkaline earth metal complexes [M within W36] (M = K+, Rb+, Cs+, NH4+, Sr2+ and Ba2+, 1-6, respectively). Compounds 1-6 were characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy. Comparisons between the structures of 1-6 and 18-crown-6 as well as the symmetry directing influence of the organo-cations in the isolation of the overall cluster architecture are discussed.     

刺五加寡糖的电喷雾多级串联质谱研究

采用小柱层析法从刺五加中分离得到刺五加寡糖类系列化合物(刺五加二糖刺五加六糖).实验结果表明,在正离子模式下的ESI-MS谱中,此类化合物呈现出特征的加合离子峰簇[M+Na]⁺/[M+K]⁺或[M+H₂O+Na]⁺/[M+H₂O+K]⁺,可以确定其分子量;在负离子模式下的ESI-MS谱中,刺五加寡糖易形成[M-H]^-/[M+nH₂O-H]^-(n<3).还利用电喷雾多级串联质谱(ESI-MSⁿ)对刺五加三糖进行了系统的研究,推断出刺五加三糖的组成与结构.     

Characterization of Nα-Fmoc-protected dipeptide isomers by electrospray ionization tandem mass spectrometry (ESI-MS(n)): effect of protecting group on fragmentation of dipeptides

A series of positional isomeric pairs of Fmoc-protected dipeptides, Fmoc-Gly-Xxx-OY/Fmoc-Xxx-Gly-OY (Xxx=Ala, Val, Leu, Phe) and Fmoc-Ala-Xxx-OY/Fmoc-Xxx-Ala-OY (Xxx=Leu, Phe) (Fmoc=[(9-fluorenylmethyl)oxy]carbonyl) and Y=CH(3)/H), have been characterized and differentiated by both positive and negative ion electrospray ionization ion-trap tandem mass spectrometry (ESI-IT-MS(n)). In contrast to the behavior of reported unprotected dipeptide isomers which mainly produce y(1)(+) and/or a(1)(+) ions, the protonated Fmoc-Xxx-Gly-OY, Fmoc-Ala-Xxx-OY and Fmoc-Xxx-Ala-OY yield significant b(1)(+) ions. These ions are formed, presumably with stable protonated aziridinone structures. However, the peptides with Gly- at the N-terminus do not form b(1)(+) ions. The [M+H](+) ions of all the peptides undergo a McLafferty-type rearrangement followed by loss of CO(2) to form [M+H-Fmoc+H](+). The MS(3) collision-induced dissociation (CID) of these ions helps distinguish the pairs of isomeric dipeptides studied in this work. Further, negative ion MS(3) CID has also been found to be useful for differentiating these isomeric peptide acids. The MS(3) of [M-H-Fmoc+H](-) of isomeric peptide acids produce c(1)(-), z(1)(-) and y(1)(-) ions. Thus the present study of Fmoc-protected peptides provides additional information on mass spectral characterization of the dipeptides and distinguishes the positional isomers.