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1.
CaRg n+ (Rg=He, Ne, Ar) complexes with n=1–4, are investigated by performing using the B3LYP/6-311+G (3df) density functional theory calculations. The CaHe n+ ( n=1–4) complexes are found to be stable. In the case of CaNe n+ and CaAr n+, stable structures and stationary point were found only for n=1 and 2. For n=3 in the C3V and the D3h point group as well as for n=4 in the Td (tetrahedral) point group a saddle point (imaginary frequency) is observed and global minimum could be obtained along the potential energy surface. 相似文献
2.
The dissociative multiple photoionization of tetramethylgermane (Ge(CH 3) 4) in the valence, and in the Ge(3d,3p,3s) and C(1s) inner-shell regions has been studied by using time-of-flight mass spectrometry coupled to synchrotron radiation in the range 49.5–450 eV. Total and individual photoion yields have been recorded as a function of the incident photon energy. Several discrete resonances over a structureless giant resonance are observed below the Ge(3p), Ge(3s) and C(1s) threshold regions. The structureless giant resonance corresponding to the Ge(3d) presumably arises from the continuum enhancement caused by the 3d→εf transition. Various monocations of H +, H 2+, CH n+ ( n=0–4), C 2H n+ ( n=0–5), GeH n+, GeCH n+, GeC 2H n+, and GeC 3H n+ are detected in the whole energy range. Dissociation processes have also been investigated by photoelectron–photoion and photoion–photoion coincidence methods. The dominant dissociation channel is found to be CH n+–GeCH n+ in the whole energy examined. Specific energy dependence of dissociation processes is observed in the Ge(3p) and Ge(3s) regions. With the help of ab initio HF/6-311++G(2df,p) calculation, we roughly estimated the photoabsorption positions and symmetries for the discrete core hole states. 相似文献
3.
Ab initio SCF and CI calculations have been carried out for H n+ and H n− ( n = 3, 5, 7, 9, 11, 13) clusters with a double-zeta plus polarization basis set. The stabilization energy of negative ion clusters H n− is very small (less than 1 kcal) and their existence is critical. The structural difference between positive- and negative-ion clusters are discussed in terms of the bonding ability involved. While H n+ is a charge-transfer complex, the stability of H n− comes mainly from the ion-induced-dipole attractions. The electron correlation effect on the structure and stability of these ion clusters is also discussed. 相似文献
4.
Structure, electronic state and energy of Si nC − and Si nC −2 ( n=1–7) anions have been investigated using the density functional theory. Structural optimization and frequency analysis are performed at the level B3LYP/6-311G(d). The charged-induced structural changes in these anions have been discussed. The strong C–C bond is also favored over C–Si bonds in the Si nC −m anions in comparison with corresponding neutral cluster. Among different Si nC − and Si nC −2 ( n=1–7) anions, Si 3C −, Si 5C − and Si 2C −2 are most stable. Their stability has a decreasing tendency with the increase in the size of these clusters. 相似文献
5.
The reactivity of naphthalene and pyrene radical cations and their derivatives (C 10H n+, n=6,7,8,9), C 16H n ( n=9,10,11) has been studied with molecules of interstellar interest in an ion cyclotron resonance apparatus. The radical cations C 10H 8+ and C 16H 10+ are unreactive with H 2,CO,H 2O and NH 3. Adduct formation is the only channel for almost all reactions of C 10H 7+ with these molecules. The implications of these results for the stability of polycyclic aromatic hydrocarbon (PAH) cations in the interstellar medium are briefly discussed. Exploratory studies of the ion chemistry of a larger PAH, coronene, have also been done. 相似文献
6.
Geometries and vibrational frequencies of complexes of cationic coinage metal clusters M n+ (M=Cu, Ag, Au; n=1–4) and H 2S are computed using density functional theory. Thermochemical values for M n+H 2S decomposition channels involving loss of an H atom, H 2 molecule, M atom, or M 2 molecule are also computed. Significantly different results are obtained for closed-shell ( n odd) and open-shell ( n even) complexes. 相似文献
7.
Using pseudopotentials and double zeta basis sets with s, p diffuse functions and two sets of d functions, MRD-CI calculations were performed on As 2(±), As 4(+), GaAs −, GaAs 2(±) and Ga 2As 2(±). This study complements previous theoretical investigations on Ga (±) to Ga 4(±) and GaAs (+). For As 4 tetrahedral symmetry was assumed, and Re of X 1A 1 determined as 4.73 a0. Vertical ionization potentials to several states of As 4+ were calculated. For GaAs 2, GaAs 2+ and GaAs 2−, ground and one low-lying state were geometry-optimized, both in C 2v (Ga-As-As), and linear symmetry (GaAsAs, C ∞h and AsGaAs, D ∞h). The lowest state of GaAs 2 is 2B 2 in C 2v. For Ga 2As 2, the lowest state and low-lying excited states were optimized in various geometries. The most stable state has rhombic structure ( 1A g in D 2h), but T-form and other forms (C 2v, C ∞v, D ∞h) are only 1–2 eV less stable. In D 2h symmetry, several low-lying excited states of Ga 2As 2 were studied. The ground states of Ga 2As 2+ and Ga 2As 2− were found to be 2B 2u, and 2B 2g, respectively. Trends in ionization potentials (IP), electron affinities (EA), atomization energies and fragmentation energies for the molecules Ga xAs y and the pure compounds Ga n and As n up to 4 atoms, were studied. Ga xAs y clusters, with x + y even, have higher IP's than odd-numbered clusters. An experimentally observed alternation of EA, whereby an odd number of atoms have higher EA than their even neighbors, is confirmed. The mixed compounds Ga xAs y have atomization energies between those of Ga n and As n ( x + y = n), usually closer to those of Ga n. Fragmentation of Ga xAs y occurs such that As----As bonds are retained, and if possible, also Ga----As bonds, since the dissociation energy of As 2 is higher than that of GaAs, which in turn is higher than that of Ga 2. Calculated fragmentation energies agree qualitatively with experimental observations about the composition of 3-atomic and 4-atomic clusters Ga xAs y. 相似文献
8.
Ab initio calculations up to MP4(SDTQ) level and density functional theory have been used to estimate binding energies and electronic structures of Cu +(L) n (L=OH 2, NH 3, n=1–4) complexes using TZP basis set types. The computed binding energies agree well with experimental values. General trends in structures and energetics are recorded for both Cu +(OH 2) n and Cu +(NH 3) n systems. The first two ligands are more strongly bound to Cu + than the third and fourth molecules. The 4s–3d σ hybridization and electrostatic interactions are the main factors behind the higher binding energies for the first two ligands. Analysis of HOMO mixed orbitals in the copper ion as well as in complexes indicates shrinking of the orbital lobes directed to the ligand with shrinking more effective in the two ligand system. The lower binding energies for the third and fourth ligands were attributed to the attenuation of sd σ hybridization and decreasing of Cu–L attraction at long separation which is necessary to relieve Cu–L and L–L exchange repulsions. NBO analysis and charge-model calculations support the presence of sd σ hybridization and electron transfer to the copper ion in case of the first two ligands. 相似文献
9.
Ion-exclusion chromatography–cation-exchange chromatography was developed for the simultaneous separation of common inorganic anions and cations (Cl −, NO 3− and SO 42−; Na +, NH 4+, K +, Mg 2+ and Ca 2+) on a weakly acidic cation-exchange column by elution with weak acid. Generally, the resolution among these monovalent cations was only moderate, thereby hindering the determination of these analytes in natural-water samples. Therefore, 18-crown-6 was added to the eluent to improve the resolution. A good separation of these anions and cations on a weakly acidic cation-exchange column was achieved in 30 min by elution with 5 m M tartaric acid/6 m M 18-crown-6/methanol–water (7.5:92.5). The ion-exclusion chromatography–cation-exchange chromatography method developed here was successfully applied to the separation of major anions and cations in an environmental water sample. 相似文献
10.
A series of novel heterobimetallic crown ether-like polyoxadiphosphaplatinaferrocenophanes cis-[1,1′-Fc(CH 2O(CH 2CH 2O) nCH 2CH 2PPh 2) 2]PtCl 2 ( n=1–3) (4a–c) was synthesized in good yield by cyclization of the bis(phosphine) ligands 1,1′-Fc(CH 2O(CH 2CH 2O) nCH 2CH 2PPh 2) 2 ( n=1–3) (3a–c) and (PhCN) 2PtCl 2 under high dilution conditions in CH 2Cl 2. The bisphosphines 3a–c are obtained by reaction of the corresponding diols 1,1′-Fc(CH 2O(CH 2CH 2O) nCH 2CH 2OH) 2 ( n=1–3) (1a–c) with: (i) CH 3SO 2Cl in CH 2Cl 2 and (ii) LiPPh 2 in THF. Although the X-ray crystal structure of 4a shows that the cavity is large enough for the encapsulation of small metal cations, inclusion experiments of 4a–c with Group 1 cations, and Mg 2+, or NH 4+ in solution applying NMR titration and cyclovoltammetric methods reveal no evidence for the formation of host–guest complexes for 4a,b. In the case of 4c only the addition of Na + or K + leads to an insignificant effect. 相似文献
11.
The ionization and dissociative ionization of NF 3 by electron impact has been measured by Fourier transform mass spectrometry (FTMS). The total ionization cross-section rises to a maximum value of 2.4±0.4×10 −16 cm 2 at 140 eV. Estimates of the total single ionization cross-section using ab initio energies with the binary encounter Bethe (BEB) [Y.K. Kim, M.E. Rudd, Phys. Rev. A 50 (1994) 3594] or Deutsch–Märk [Int. J. Mass Spec. 197 (2000) 37] models are roughly twice the measured values. The partial cross-sections creating NF x+ ( x=0, 1, 2, 3), F +, and NF x2+ ( x=1, 2, 3) are reported. Differences between the FTMS results and quadrupole data and fast atom beam results of Tarnovsky et al. [Int. J. Mass Spectrom. Ion Processes 133 (1994) 175] are discussed. 相似文献
12.
Using the temperature jump technique, the study of the kinetics of the complexing of oxomolybdate anion with malic acid has been carried out in aqueous solutions of pH 7.15–8.5 at ionic strength 0.1 M (KNO 3) and 25°'C. A reaction scheme for the formation of 1 : 1 complexes is proposed which accounts for the observed relaxation rates. The significance of the ligand deprotonation on the complexation reaction of MoO42− by a single protonated ligand, i.e. MoO42−+LHnk→MoO3(OH)Ln−2, (where n = 1 -, 2 -, etc), is analysed on the basis of a simple model. A linear correlation between the log k and the pK of the monoprotonated ligand (LH) is found for this reaction when the global process is controlled by the proton transfer from the ligand to an oxogroup, i.e. log k = a - 0.5xpK. It is found that this correlation is satisfied by MoO42− and WO42−. The experimental slopes for these oxyanions are −0.503 and −0.543 respectively, in agreement with the predictions. 相似文献
13.
Ab initio molecular orbital calculations are reported for small neutral molecules and cations containing magnesium, nitrogen and hydrogen. Structures have been optimized using gradient techniques at B3LYP/6-31+G(d) and at MP2(full)/6-311++G(d,p). Single-point calculations are reported at QCISD(T)(full)/6-311++G(2df,p) and at CCSD(T)(full)/6-311++G(2df,p) levels using geometries optimized at MP2(full)/6-311++G(d,p). Standard enthalpies of formation at 298 K have been calculated at these two higher levels of theory. Other thermochemical properties calculated include ionization energies and proton affinities. The binding enthalpies of ammonia to Mg +, MgNH 2+ and MgNH 3+ are also reported. 相似文献
14.
Twenty-two isomers/conformers of C 3H 6S +√ radical cations have been identified and their heats of formation (Δ Hf) at 0 and 298 K have been calculated using the Gaussian-3 (G3) method. Seven of these isomers are known and their Δ Hf data are available in the literature for comparison. The least energy isomer is found to be the thioacetone radical cation (4 +) with C2v symmetry. In contrast, the least energy C 3H 6O +√ isomer is the 1-propen-2-ol radical cation. The G3 Δ Hf298 of 4 + is calculated to be 859.4 kJ mol −1, ca. 38 kJ mol −1 higher than the literature value, ≤821 kJ mol −1. For allyl mercaptan radical cation (7 +), the G3 Δ Hf298 is calculated to be 927.8 kJ mol −1, also not in good agreement with the experimental estimate, 956 kJ mol −1. Upon examining the experimental data and carrying out further calculations, it is shown that the G3 Δ Hf298 values for 4 + and 7 + should be more reliable than the compiled values. For the five remaining cations with available experimental thermal data, the agreement between the experimental and G3 results ranges from fair to excellent. Cation CH3CHSCH2+√ (10+) has the least energy among the eleven distonic radical cations identified. Their ΔHf298 values range from 918 to 1151 kJ mol−1. Nevertheless, only one of them, CH2=SCH2CH2+√ (12+), has been observed. Its G3 ΔHf298 value is 980.9 kJ mol−1, in fair agreement with the experimental result, 990 kJ mol−1. A couple of reactions involving C3H6S+√ isomers CH2=SCH2CH2+√ (12+) and trimethylene sulfide radical cation (13+) have also been studied with the G3 method and the results are consistent with experimental findings. 相似文献
15.
Two polymeric mercury(II) halide adducts of an olefinic double betaine, cis-( p-Me 2NC 5H 4N +) 2C 2(COO −) 2 (L), have been prepared and characterized by X-ray crystallography. [{Hg 2L 2Cl 4·6HgCl 2} n] (1) crystallizes in the monoclinic space group C2/ c with Z = 4, and [{Hg 2L 2Br 4·HgBr 2} n] (2) in the triclinic space group P
with Z = 1. Complexes 1 and 2 are structurally similar, being composed of centrosymmetric fourteen-membered rings and nearly linear HgX 2 (X = Cl, Br) moieties that are further inter-linked by weak HgX [HgCl = 2.930–3.136(9) Å, HgBr = 3.057–3.310(6) Å] and HgO [2.64, 2.75(3) Å] bonds to generate a two-dimensional polymeric network. 相似文献
16.
The multiphoton ionization of the hydrogen-bonded clusters N, N-dimethylformamide–(methanol) n (DMF–(CH 3OH) n) was studied using a time-of-flight mass spectrometer at the wavelengths of 355 and 532 nm. At both wavelengths, a series of protonated DMF–(CH 3OH) nH + ions was obtained. The clusters were also investigated by density functional theory B3LYP method in conjunction with basis sets 6-31+G(d,p) and 6-311+G(2d,p). Equilibrium geometries of both neutral and ionic DMF–CH 3OH clusters, and dissociation channels and dissociation energies of the ionic clusters are presented. The results show that when DMF–CH 3OH is vertically ionized and dissociated, DMFH + and CH 3O are the dominant products via proton transfer reaction. A high energy barrier makes another channel corresponding to the production of DMFH + and CH 2OH disfavored. In the DMF–(CH 3OH)H + ion, the proton prefers to link with the O atom of DMF molecule. Variation of atomic charges during proton transfer in hydrogen bond of the protonated cluster DMF–(CH 3OH)H + ion is also discussed. 相似文献
17.
有机/无机钙钛矿是一类极具潜质的光电材料,目前已实现超过20%的光电转化效率。本文采用第一性原理对有机/无机混合钙钛矿CH 3NH 3Pb xSn 1-xI 3 ( x = 0-1)的结构及光电特性进行了理论研究。结果表明,范德华力(VDW)在优化钙钛矿结构中起着重要的作用,考虑范德华力可减小Pb/Sn―I键长,从而减小体系体积。通过分析甲胺离子CH 3NH 3+的态密度和Bader电荷,我们发现其对前线轨道没有贡献,仅仅扮演电荷供体的角色。Pb/Sn与I之间同时存在共价键和离子键相互作用。价带顶(VBM)主要是由I 5 p以及Pb 6 s (Sn 5 s)杂化组成,而导带底(CBM)主要由Pb 6 p (Sn 5 p)轨道组成。在可见光区,随着波长的增加,体系吸收强度呈现整体下降趋势;随着Sn/Pb比值逐渐增大,吸收强度呈现增大趋势。CH 3NH 3SnI 3在可见光区表现出较佳的吸收光谱特性。 相似文献
18.
Since ion-neutral reactions are a major component of the processes driving interstellar chemistry, most reaction network include protonated species. Besides, these ions are able to initiate chemical processes that would not occur with their neutral parents. In this contribution we report a systematic study of the protonated adducts of the OC nO series ( n=3–8) using the B3LYP level of theory. The structures of all possible O-protonated and C-protonated isomers of [OC nOH +] have been determined together with their rotational constants, vibrational frequencies and intensities. Although it appears that these ions belong to two different series, odd- n and even- n, it is found that protonation occurs at the carbons second to the terminal oxygens for all n. The most stable structure is found to be the singlet ion whatever the singlet or triplet spin state of the parent species. However, due to the lack of efficient spin–orbit coupling, only the odd series [OC nOH +] with n=3,5,7 should be formed on the singlet ground state surface. Analysis of the infrared intensities shows that the spectra are dominated by only one or two very strong bands (CC stretching) that carry most of the overall intensity in the 2200–2350 cm −1 region. 相似文献
19.
A tandem quadrupole mass spectrometer is used to study the charge transfer reactions NH 3+ + NO and NO + + NH 3 over a collision energy range 1.5–13 eV. The vibrational state of the reagent ions is selected by resonance-enhanced multiphoton ionization. For the 0.9 eV exothermic process NH 3+ + NO → NH 3 + NO + excitation of the v2 umbrella bending mode ( v2 = 0–12) causes no marked change in the charge transfer cross section, while in the reverse process NO + + NH 3 → NO + NH 3+ excitation of the NO + vibration ( v = 0–6) strongly enhanced the charge transfer cross section. 相似文献
20.
Nickel(II) chromate complex with imidazole (HIm) was isolated from the [Ni 2+–HIm–CrO 42−] system in various experimental conditions, i.e. reagent molar ratios and nickel(II) salts. The catena( μ-CrO 4- O, O′)[Ni(HIm) 3H 2O] (1) crystallizes in monoclinic crystal system—space group P2 1/ n with cell parameters: a=11.784(2), b=8.899(2), c=13.934(3) (Å), β=95.19(3) (°). The unit cell contains two independent helixes, left- and right-handed, stabilized by intrahelical and interhelical hydrogen bonds (HB) and π–π interactions. The cis coordination of the CrO 42− anions and the HB systems appeared to be the main determinants of the helical architecture. To the best of our knowledge the cis-chromate coordination was observed for the first time. The cis coordination causes the distortion of the nickel octahedron, which was analysed by 4 K single crystal electronic spectra with D4h symmetry approximation (gaussian resolution and crystal field parameters). This symmetry was also confirmed with the polarised electronic spectra. The magnetic properties of the complex suggest the occurrence of weak intrachain antiferromagnetic interactions between the magnetic Ni II center. The computational DFT studies of complex 1 assuming three possible isomers mer[(HIm) 3]– cis[(CrO 42−) 2], mer– trans and fac– cis suggested that the main contribution to the stability of 1 might have interhelical and intrahelical hydrogen bonds. 相似文献
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