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1.
A density functional theory study on the geometrical structures and dissociation channels of MP n + (M = Fe, Co or Ni; n = 2, 4, 6 or 8) binary cluster ions has been performed. The tetrahedral P4 structure and linear P2 structure are found to be two relatively stable units in these ions. The lowest energy structures of MP n + cluster ions are constructed by bonding a twofold or fourfold M atom with a P4 or P2 unit. The M–P bond is clearly weaker than the P–P bond. The most likely dissociation channel of the MP n + cluster ions is the detachment of a P4 or P2 fragment. This conclusion is well consistent with the published experimental data and consistent with our previously reported theoretical study on the CrP m + (m = 2, 4, 6 or 8) cluster ions.  相似文献   

2.
A reverse‐binding‐selectivity between monovalent and divalent cations was observed for two different self‐assembly G16‐hexadecamer and G8‐octamer systems. The dissociation constant between G4‐quadruplex and monomer was calculated via VT‐1H NMR experiments. Quantitative energy profiles revealed entropy as the key factor for the weaker binding toward Ba2+ compared with K+ in the G8‐octamer system despite stronger ion‐dipole interactions. This study is the first direct comparison of the G4‐quartet binding affinity between mono and divalent cations and will benefit future applications of G‐quadruplex‐related research. Further competition experiments between the G8‐octamer and 18‐crown‐6 with K+ demonstrated the potential of this G8 system as a new potassium receptor.  相似文献   

3.
The collision‐induced dissociation (CID) and electron‐induced dissociation (EID) spectra of the [(NaCl)m(Na)n]n+ clusters of sodium chloride have been examined in a hybrid linear ion trap Fourier transform ion cyclotron resonance mass spectrometer. For singly charged cluster ions (n = 1), mass spectra for CID and EID of the precursor exhibit clear differences, which become more pronounced for the larger cluster ions. Whereas CID yields fewer product ions, EID produces all possible [(NaCl)xNa]+ product ions. In the case of doubly charged cluster ions, EID again leads to a larger variety of product ions. In addition, doubly charged product ions have been observed due to loss of neutral NaCl unit(s). For example, EID of [(NaCl)11(Na)2]2+ leads to formation of [(NaCl)10(Na)2]2+, which appears to be the smallest doubly charged cluster of sodium chloride observed experimentally to date. The most abundant product ions in EID spectra are predominantly magic number cluster ions. Finally, [(NaCl)m(Na)2]+ . radical cations, formed via capture of low‐energy electrons, fragment via the loss of [(NaCl)n(Na)] . radical neutrals. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

4.
Cerium oxide cluster cations (CemOn+, m=2–16; n=2m, 2m±1 and 2m±2) are prepared by laser ablation and reacted with acetylene (C2H2) in a fast‐flow reactor. A time‐of‐flight mass spectrometer is used to detect the cluster distribution before and after the reactions. Reactions of stoichiometric CemO2m+ (m=2–6) with C2H2 produce CemO2m?2+ clusters, which indicates a “double‐oxygen‐atom transfer” reaction CemO2m++C2H2→CemO2m?2++(CHO)2 (ethanedial). A single‐oxygen‐atom transfer reaction channel is also identified as CemO2m++C2H2→CemO2m?1++C2H2O (at least for m=2 and 3). Density functional theory calculations are performed to study reaction mechanisms of Ce2O4++C2H2, and the calculated results confirm that both the single‐ and double‐oxygen‐atom transfer channels are thermodynamically and kinetically favourable.  相似文献   

5.
The crystal structure of the title compound, C6H8N+·C8HN4O2, is characterized by three independent ion pairs (A, B and C) in the asymmetric unit. Each ion pair consists of an anion and a cation, and the three ion pairs have similar geometric parameters. All the anions are arranged as dianion dimers via two N—H⋯O hydrogen bonds and the dimers form one‐dimensional columns parallel to the b axis as a result of π–π interactions. The cations are also stacked, in two different ways: one type of stacking consists of alternating A and B cations, while the other type consists of C cations only. Each dianion dimer stack is surrounded by eight stacks of cations and is not connected directly to other dianion stacks.  相似文献   

6.
Both positive and negative phosphorus cluster ions were generated from the laser ablation of a red phosphorus sample. The mass distribution of phosphorus cluster ions was found to be very sensitive to the power density of the ablation laser. The P 7 + species exhibits the highest signal intensity in the recorded mass spectra of bare phosphorus cluster cations, as does P 5 - among the anions. Their special structural stability can be attributed to their planar configuration and their aromatic character. As the phosphorus cluster size increases, the odd/even alternation of the signal intensity becomes more pronounced. For the P n + species with n > 24, the relative abundance varies in the order of 8 and P n + with n = 8k + 1 (k = 3–11) are more intense than their neighbors. For comparison, some binary phosphide cluster ions, including CnP m - , SinP m - , BnP m + and AlnP m + , were produced as well. The mass distribution of binary phosphide cluster ions changes with different components. From analysis of the recorded mass spectra of the phosphide cluster ions, the larger clusters may be in a polyhedral configuration and tend to have all valence electrons paired.  相似文献   

7.
Thiosilicates of the Rare‐Earth Elements: III. KLa[SiS4] and RbLa[SiS4] – A Structural Comparison Pale yellow, platelet shaped, air‐ and water resistant single crystals of KLa[SiS4] derived from the reaction of lanthanum (La) and sulfur (S) with silicon disulfide (SiS2) in a molar ratio of 2 : 3 : 1 with an excess of potassium chloride (KCl) as flux and source of potassium ions in evacuated silica ampoules at 850 °C within seven days. The analogous reaction utilizing a melt of rubidium chloride (RbCl) instead also leads to yellow comparable single crystals of RbLa[SiS4]. The potassium lanthanum thiosilicate crystallizes monoclinically with the space group P21/m (a = 653.34(6), b = 657.23(6), c = 867.02(8) pm, β = 107.496(9)°) and two formula units per unit cell, while the rubidium lanthanum thiosilicate has to be assigned orthorhombically with the space group Pnma (a = 1728.4(2), b = 667.23(6), c = 652.89(6) pm) and four formula units in its unit cell. In both compounds the La3+ cations are surrounded by 8+1 sulfide anions in the shape of tricapped trigonal prisms. The Rb+ cations in RbLa[SiS4] show a coordination number of 9+2 relative to the S2? anions, which form pentacapped trigonal prisms about Rb+. This coordination number, however, is apparently too high for the K+ cations in KLa[SiS4], so that they only exhibit a bicapped trigonal prismatic environment built up by eight S2? anions. The isolated thiosilicate tetrahedra [SiS4]4? of the rubidium compound are surrounded by La3+ both edge‐ and face‐capping, but terminal as well as edge‐ and face‐spanning by Rb+. In the potassium compound there is no change for the La3+ environment about the [SiS4]4? tetrahedra, but the K+ cations are only able to attach terminal and via edges. The whole structure is built up by anionic equation/tex2gif-stack-1.gif{La[SiS4]}? layers that are separated by the alkali metal cations. In direct comparison the two thiosilicate structures can be regarded as stacking variants.  相似文献   

8.
The dissociation of ethylbenzene cation C8H10 served as a prototype to investigate the decompasition mechanisms of alkylbenzene cations. The reactions of C8H10 decomposition reaction system have been studied extensively at the B3LYP/6‐311++G?? ?? level with Gaussion 98 package. The chain reaction of C8H10 dissociation is initiated by C–H bond rupture. All reaction channels were fully investigated with the vibrational mode analysis to confirm the transition states and reveal the reaction mechanism. The energetically most favorable pathway is C8H10→TS4→P2+H· and the channel leading to C8H10 and C2H4 is also competitive.  相似文献   

9.
Salts containing bis‐phosphonio‐benzophospholide cations 2 a – d with an additional donor site in one of the phosphonio‐moieties were synthesized either via quaternisation of the Ph2P moiety in the neutral phosphonio‐benzophospholide 3 , or via ring‐closure of the functionalized bis‐phosphonium ion 6 . The Ph2P‐substituted cation 2 d formed chelate complexes [M(k2P,P′‐ 2 d )(CO)n]+ with M(CO)n = Ni(CO)2, Fe(CO)3, Cr(CO)4. In the latter case, competition between formation of the chelate and a complex [Cr(kP‐ 2 d )2(CO)4]2+ was observed, and interpreted as a consequence of antagonism between the stabilizing chelate effect and destabilizing ligand–ligand repulsions. The formation of stable PdII and PtII complexes of 2 d suggests that the chelate effect may also overcome the kinetic inhibition which so far prevented isolation of complexes of these metals with bis‐phosphonio‐benzophospholides. The newly synthesized ligands and complexes were characterized by spectroscopic data, and an X‐ray crystal structure analysis of 2 a [Br]. The reactivity of chelate complexes towards Ph3P indicates that the ring phosphorus atom is a weaker donor than the pendant Ph2P‐group.  相似文献   

10.
Positive singly charged ionic liquid aggregates [(Cnmim)m+1(BF4)m]+ (mim = 3‐methylimidazolium; n = 2, 4, 8 and 10) and [(C4mim)m+1(A)m]+ (A = Cl, BF4, PF6, CF3SO3 and (CF3SO2)2N) were investigated by electrospray ionisation mass spectrometry and energy‐variable collision induced dissociation. The electrospray ionisation mass spectra (ESI‐MS) showed the formation of an aggregate with extra stability for m = 4 for all the ionic liquids with the exception of [C4mim][CF3SO3]. ESI‐MS‐MS and breakdown curves of aggregate ions showed that their dissociation occurred by loss of neutral species ([Cnmim][A])a with a ≥ 1. Variable‐energy collision induced dissociation of each aggregate from m = 1 to m = 8 for all the ionic liquids studied enabled the determination of Ecm, 1/2 values, whose variation with m showed that the monomers were always kinetically much more stable than the larger aggregates, independently of the nature of cation and anion. The centre‐of‐mass energy values correlate well with literature data on ionic volumes and interaction and hydrogen bond energies. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

11.
An all-electron (AE) calculation on the geometrical structures and possible dissociation channels of MnP n + (n = 2–8) cluster ions has been performed by using density functional theory with the generalized gradient approximation (GGA) at PW91 level. The lowest energy structures of MnP n + (n = 2–8) cluster ions may be regarded as the outcome of bonding between Mn atom and one or two units of P2, P3, and P4. The most possible dissociation channels of MnP n + (n = 2–8) cluster ions are the detachment of P2, P3, or P4 unit. These conclusions are basically consistent well with previous works in which the P2 and P4 structures are regarded as two relatively stable units and easy to be stripped.  相似文献   

12.
Studies on the aggregation degrees of negatively charged phosphides derived from the nucleophilic P4 functionalization could help understand the pathway of phosphorus atoms degradation or aggregation. In this report, we have isolated and characterized four phosphorus cluster anions (P73–, P144–, P162–, and P264–) from the nucleophilic functionalization of P4 with 1,4‐dilithio‐1,3‐butadienes. These phosphorus clusters could be rationalized as the P‐atom‐containing products besides the main phospholyl lithium. Their structural features and 31P NMR behaviors are discussed based on single crystal X‐ray diffraction analysis and 31P{1H} COSY NMR analysis.  相似文献   

13.
Fragmentation reactions of β‐hydroxymethyl‐, β‐acetoxymethyl‐ and β‐benzyloxymethyl‐butenolides and the corresponding γ‐butyrolactones were investigated by electrospray ionization tandem mass spectrometry (ESI‐MS/MS) using collision‐induced dissociation (CID). This study revealed that loss of H2O [M + H ?18]+ is the main fragmentation process for β‐hydroxymethylbutenolide (1) and β‐hydroxymethyl‐γ‐butyrolactone (2). Loss of ketene ([M + H ?42]+) is the major fragmentation process for protonated β‐acetoxymethyl‐γ‐butyrolactone (4), but not for β‐acetoxymethylbutenolide (3). The benzyl cation (m/z 91) is the major ion in the ESI‐MS/MS spectra of β‐benzyloxymethylbutenolide (5) and β‐benzyloxymethyl‐γ‐butyrolactone (6). The different side chain at the β‐position and the double bond presence afforded some product ions that can be important for the structural identification of each compound. The energetic aspects involved in the protonation and gas‐phase fragmentation processes were interpreted on the basis of thermochemical data obtained by computational quantum chemistry. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

14.
Crystals of the title compound, C4H8N5+·C2F3O2, are built up of singly protonated 2,4‐diamino‐6‐methyl‐1,3,5‐triazin‐1‐ium cations and trifluoroacetate anions. The CF3 group of the anion is disordered. The oppositely charged ions interact via almost linear N—H...O hydrogen bonds, forming a CF3COO...C4H8N5+ unit. Two units related by an inversion centre interact through a pair of N—H...N hydrogen bonds, forming planar (CF3COO...C4H8N5+...C4H8N5+·CF3COO) aggregates that are linked by a pair of N—H...O hydrogen bonds into chains running along the c axis.  相似文献   

15.
The asymmetric unit of the title compound, 3C10H12N22+·2C10H11N2+·8C6H5NO5P, contains one and a half naphthalene‐1,5‐diaminium cations, in which the half‐molecule has inversion symmetry, one 5‐aminonaphthalen‐1‐aminium cation and four hydrogen (5‐carboxypyridin‐3‐yl)phosphonate anions. The crystal structure is layered and consists of hydrogen‐bonded anionic monolayers between which the cations are arranged. The acid monoanions are organized into one‐dimensional chains along the [101] direction via hydrogen bonds established between the phosphonate sites. (C)O—H...Npy hydrogen bonds (py is pyridine) crosslink the chains to form an undulating (010) monolayer. The cations serve both to balance the charge of the anionic network and to connect neighbouring layers via multiple hydrogen bonds to form a three‐dimensional supramolecular architecture.  相似文献   

16.
The novel title organic salt, 4C5H7N2+·C24H8O84−·8H2O, was obtained from the reaction of perylene‐3,4,9,10‐tetracarboxylic acid (H4ptca) with 4‐aminopyridine (4‐ap). The asymmetric unit contains half a perylene‐3,4,9,10‐tetracarboxylate (ptca4−) anion with twofold symmetry, two 4‐aminopyridinium (4‐Hap+) cations and four water molecules. Strong N—H...O hydrogen bonds connect each ptca4− anion with four 4‐Hap+ cations to form a one‐dimensional linear chain along the [010] direction, decorated by additional 4‐Hap+ cations attached by weak N—H...O hydrogen bonds to the ptca4− anions. Intermolecular O—H...O interactions of water molecules with ptca4− and 4‐Hap+ ions complete the three‐dimensional hydrogen‐bonding network. From the viewpoint of topology, each ptca4− anion acts as a 16‐connected node by hydrogen bonding to six 4‐Hap+ cations and ten water molecules to yield a highly connected hydrogen‐bonding framework. π–π interactions between 4‐Hap+ cations, and between 4‐Hap+ cations and ptca4− anions, further stabilize the three‐dimensional hydrogen‐bonding network.  相似文献   

17.
18.
Gold phosphides show unique optical or semiconductor properties and there are extensive high technology applications, e.g. in laser diodes, etc. In spite of the various AuP structures known, the search for new materials is wide. Laser ablation synthesis is a promising screening and synthetic method. Generation of gold phosphides via laser ablation of red phosphorus and nanogold mixtures was studied using laser desorption ionisation time‐of‐flight mass spectrometry (LDI TOFMS). Gold clusters Aum+ (m = 1 to ~35) were observed with a difference of one gold atom and their intensities were in decreasing order with respect to m. For Pn+ (n = 2 to ~111) clusters, the intensities of odd‐numbered phosphorus clusters are much higher than those for even‐numbered phosphorus clusters. During ablation of P‐nanogold mixtures, clusters Aum+ (m = 1‐12), Pn+ (n = 2‐7, 9, 11, 13–33, 35–95 (odd numbers)), AuPn+ (n = 1, 2–88 (even numbers)), Au2Pn+ (n = 1‐7, 14–16, 21–51 (odd numbers)), Au3Pn+ (n = 1‐6, 8, 9, 14), Au4Pn+ (n = 1‐9, 14–16), Au5Pn+ (n = 1‐6, 14, 16), Au6Pn+ (n = 1‐6), Au7Pn+ (n = 1‐7), Au8Pn+ (n = 1‐6, 8), Au9Pn+ (n = 1‐10), Au10Pn+ (n = 1‐8, 15), Au11Pn+ (n = 1‐6), and Au12Pn+ (n = 1, 2, 4) were detected in positive ion mode. In negative ion mode, Aum (m = 1–5), Pn (n = 2, 3, 5–11, 13–19, 21–35, 39, 41, 47, 49, 55 (odd numbers)), AuPn (n = 4–6, 8–26, 30–36 (even numbers), 48), Au2Pn (n = 2–5, 8, 11, 13, 15, 17), Au3Pn (n = 6–11, 32), Au4Pn (n = 1, 2, 4, 6, 10), Au6P5, and Au7P8 clusters were observed. In both modes, phosphorus‐rich AumPn clusters prevailed. The first experimental evidence for formation of AuP60 and gold‐covered phosphorus Au12Pn (n = 1, 2, 4) clusters is given. The new gold phosphides generated might inspire synthesis of new Au‐P materials with specific properties. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

19.
Fragmentation of the γ‐aminobutyric acid molecule (GABA, NH2(CH2)3COOH) following collisions with slow O6+ ions (v≈0.3 a.u.) was studied in the gas phase by a combined experimental and theoretical approach. In the experiments, a multicoincidence detection method was used to deduce the charge state of the GABA molecule before fragmentation. This is essential to unambiguously unravel the different fragmentation pathways. It was found that the molecular cations resulting from the collisions hardly survive the interaction and that the main dissociation channels correspond to formation of NH2CH2+, HCNH+, CH2CH2+, and COOH+ fragments. State‐of‐the‐art quantum chemistry calculations allow different fragmentation mechanisms to be proposed from analysis of the relevant minima and transition states on the computed potential‐energy surface. For example, the weak contribution at [M?18]+, where M is the mass of the parent ion, can be interpreted as resulting from H2O loss that follows molecular folding of the long carbon chain of the amino acid.  相似文献   

20.
N‐methylimidazolidin‐4‐one organocatalysts were studied in the gas phase. Protonated and sodium‐cationized (sodiated) molecules are conveniently accessible by electrospray mass spectrometry. Protonation enables three different closed‐shell paths of ring cleavage leading to iminium ions. The fragmentation pattern is largely unaffected by exocyclic substituents and thus is valuable to characterize the substance type as N‐methylimidazolidin‐4‐ones. Sodiated species show a distinctly different fragmentation that is less useful for characterization purposes: apart from signal loss due to dissociation of Na+, the observation of benzyl radical loss is by far predominant. Only in absence of a benzyl substituent, an analogue of the third ring cleavage (loss of [C2H5NO]) is observed. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

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