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1.
Five cation clusters X (X=H, Li, Na, K, and Cu) with two possible isomers, i.e., regular trigonal structure (D3h) and linear structure (D∞h), have been investigated using four methods: B3LYP, B3PW91, MP2, CCSD(T) and basis set 6‐311+G(3df). The calculations show that only the regular trigonal structure (D3h) is stable. The related neutral clusters X3Cl (X=H, Li, Na, K, and Cu) are also investigated using two methods: B3LYP, MP2, and basis set 6‐311+G(3df). For H3Cl species, there is no a stable structure to be found. For other four X3Cl (X=Li, Na, K, and Cu) species, there are two stable isomers, for which the bidentate structures (C2v‐1) [see Fig. 1 (d)] are global minima. According to the general criteria for aromaticity including resonance energy (RE) and nucleus‐independent chemical shift (NICS), the five trigonal isomers exhibit a higher degree of aromaticity. Molecular orbital analysis reveals that the five trigonal X(X=H, Li, Na, K, and Cu) isomers possess only σ‐aromaticity originating from s orbitals. For the Cu ring the d orbitals do not play a significant role in the electron delocalization effects. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
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James F. Harrison Daniel B. Lawson 《International journal of quantum chemistry》2005,102(6):1087-1091
The quadrupole moments (Θ) of Li2, Na2, and K2 have been determined using SCF, B3LYP, and CCSD(T). Included in this study is the effect of valence and core–valence correlation. The variation of Θ as a function of bond length has also been evaluated from which vibrational contributions have been determined. Additionally, the shape and relative magnitude of Θ vs. bond length are attributed to the s–s nature of the bonding. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
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A theoretical study on the intermolecular interaction of energetic system-Nitromethane dimer 总被引:3,自引:0,他引:3
Three optimized geometries of nitromethane dimer have been obtained at the HF/6-31G level.Dimer binding energies have been corrected for the basis set superposition error (BSSE) and the zero point energy.Computed results indicate that the cyclic structure of (CH3NO2)2 is the most stable of three optimized geometries,whose corrected binding energyis 17.29 kJ mol-1 at the MP4SDTQ/6-31G//HF/6-31G level.In the optimized structures of nitromethane dimer,the inter-molecular hydrogen bond has not been found; and the charge-transfer interaction between CH3NO2 subsystems is weak; and the correlation interaction energy makes a little contribution to the intermolecular interaction energy of the dimer. 相似文献
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The characteristic features of molecules like polyhedra and fullerenes, which follow the 2(N+1)(2) rule of spherical aromaticity, can be related to energetically stable closed-shell configurations of (pseudo-)atoms. This unifying view relies on a thought experiment, which produces a polyhedron in a two-step process and which can, in turn, relate the electronic configuration of any spherical polyhedron to the one of a corresponding closed-shell atom. In the first step, the electronic ground-state configuration is identified. In the second step, a group theoretical analysis can be carried out; this relates the spherically symmetric atomic orbitals to the molecular orbitals classified according to the irreducible representations of the point group of the polyhedron under consideration. This procedure explains and justifies the pseudo-l classification of molecular orbitals, which is the basis of the 2(N+1)(2) rule. For the transition from the electronic configuration of the rare gas Eka-Rn (Uuo) to the icosahedral fullerene C(20) (2+), we show how a change in the ground-state configuration leads to the phenomenologically found 2(N+1)(2) rule for spherically aromatic fullerenes. 相似文献
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Junxia Cheng Hong Zhang Xinlu Cheng Shenjiang Wu 《International journal of quantum chemistry》2019,119(24):e26027
The laser synthesis of alkaline earth dimers (Be2, Mg2, Ca2, Sr2, and Ba2) is investigated by theoretical calculation. Photoassociation based on ab initio calculations is rationalized by Franck-Condon filtering. The optimal target states of photoassociations have been obtained, which are A1∑+u state for Be2, Mg2, and Ca2, and are B1∑+u state for Sr2 and Ba2, corresponding to vibrational transition bands from X1∑+g to excited state are 0-1, 0-7, 0-10, 0-13, and 0-3, respectively. The proposed laser drive transitions to target states are also investigated that range from 350 to 740 nm. By using quantum wave-packet dynamic methods, we calculated the absorption cross sections of photon energy and yields for the selected states of photoassociation. It show that the most sensitive molecules for quantum selective control of photoassociation are Be2 and Ba2 for alkaline earth dimers. These important parameters will provide a feasible scheme for further experimental researches. 相似文献
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Ab initio calculations indicate that metalation of the exocyclic amino group of cytosine by the elements of Group IA (Li, Na, K, Rb and Cs) induces protonation of a nucleobase ring nitrogen atom, and hence causes a proton shift from an exocyclic to an endocyclic nitrogen atom. Thus, this metal‐assisted process leads to the generation of rare nucleobase tautomers. The calculations suggest that this kind of metalation increases the protonation energies of the aromatic ring of the nucleobase. The present study reports the quantum chemistry analysis of the metal‐assisted tautomerization. The calculations clearly demonstrate that metalation of the exocyclic amino group of the nucleobase significantly increases the protonation energy of the aromatic rings of the nucleobase. Also, absolute anisotropy shift, molecular orbital and natural bond orbital calculations are compatible with these results. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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Competition between alkalide characteristics and nonlinear optical properties in OLi3MLi3O (M = Li,Na, and K) complexes
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Ambrish Kumar Srivastava Neeraj Misra 《International journal of quantum chemistry》2017,117(3):208-212
Alkalides possess enhanced nonlinear optical (NLO) responses due to localization of excess electrons on alkali metals. Employing MP2/6‐311 + G(d) level, we design novel alkalides by placing alkali atoms (M) between two Li3O superalkalis. We notice a competition between alkalide characteristics and NLO properties in OLi3? M? Li3O (M = Li, Na, and K) isomers. For instance, the atomic charge on M (q M) in D 2h structure is ?0.58e for M = Li and its first static mean hyperpolarizablity (β o) is 1 a.u., but in C 2v structure, q M = ?0.12e and β o= 3.4 × 103 a.u. More interestingly, the β o value for M = K (C 2v) increases to 1.9 × 104 a.u. in which q M = 0.24e . These findings may provide new insights into the design of alkalides, an unusual class of salts and consequently, lead to further researches in this direction. 相似文献
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A theoretical investigation of the gas-phase oxidation reaction of the saturated tert-butyl radical.
The radical-radical reaction mechanisms and dynamics of ground-state atomic oxygen [O(3P)] with the saturated tert-butyl radical (t-C4H9) are investigated using the density functional method and the complete basis set model. Two distinctive reaction pathways are predicted to be in competition: addition and abstraction. The barrierless addition of O(3P) to t-C4H9 leads to the formation of an energy-rich intermediate (OC4H9) on the lowest doublet potential energy surface, which undergoes subsequent direct elimination or isomerization-elimination leading to various products: C3H6O + CH3, iso-C4H8O + H, C3H7O + CH2, and iso-C4H8 + OH. The respective microscopic reaction processes examined with the aid of statistical calculations, predict that the major addition pathway is the formation of acetone (C3H6O) + CH3 through a low-barrier, single-step cleavage. For the direct, barrierless H-atom abstraction mechanism producing iso-C4H8 (isobutene) + OH, which was recently reported in gas-phase crossed-beam investigations, the reaction is described in terms of both an abstraction process (major) and a short-lived addition dynamic complex (minor). 相似文献
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Peaks with anomalous abundance found in the mass spectra are associated with ions with enhanced stability. Among the scientific community focused on mass spectrometry, these peaks are called ‘magic peaks’ and their stability is often because of suggestive symmetric structures. Here, we report findings on ionised Na‐acetic acid clusters [Na+‐(AcA)n] produced by Na‐doping of (AcA)n and UV laser ionisation. Peaks labelled n = 2, 4, 8 are clearly distinguishable in the mass spectra from their anomalous intensity. Ab initio calculations helped elucidate cluster structures and energetic. A plausible interpretation of the magic peaks is given in terms of (AcA)n formed by dimer aggregation. The encasing of Na+ by twisted dimers is proposed to be the origin of the enhanced cluster stability. A conceivable dimer‐formed tube‐like closed structure is found for the Na+‐(AcA)8. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Krokos E Spänig F Ruppert M Hirsch A Guldi DM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(5):1328-1341
A series of truly water-soluble C(60)/porphyrin electron donor-acceptor conjugates has been synthesized to serve as powerful mimics of photosynthetic reaction centers. To this end, the overall water-solubility of the conjugates was achieved by adding hydrophilic dendrimers of different generations to the porphyrin moiety. An important variable is the metal center of the porphyrin; we examined zinc(II), copper(II), cobalt(II), nickel(II), iron(III), and manganese(III). The first insights into electronic communication between the electron donors and the electron acceptors came from electrochemical assays, which clearly indicate that the redox processes centered either on C(60) or the porphyrins are mutually affected. Absorption measurements, however, revealed that the electronic communication in terms of, for example, charge-transfer features, remains spectroscopically invisible. The polar environment that water provides is likely to be a cause of the lack of detection. Despite this, transient absorption measurements confirm that intramolecular charge separation processes in the excited state lead to rapid deactivation of the excited states and, in turn, afford the formation of radical ion pair states in all of the investigated cases. Most importantly, the lifetimes of the radical ion pairs were found to depend strongly on several aspects. The nature of the coordinated metal center and the type of dendrimer have a profound impact on the lifetime. It has been revealed that the nature/electronic configuration of the metal centers is decisive in powering a charge recombination that either reinstates the ground state or any given multiplet excited state. Conversely, the equilibrium of two opposing forces in the dendrimers, that is, the interactions between their hydrophilic regions and the solvent and the electronic communication between their hydrophobic regions and the porphyrin and/or fullerene, is the key to tuning the lifetimes. 相似文献
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A theoretical study was performed for the reaction of formyl cation and acetylene to give C3H+O in flames and C2H (nonclassical)+CO, both in flames and in interstellar clouds. The corresponding Potential Energy Surface (PES) was studied at the B3LYP/cc‐pVTZ level of theory, and single‐point calculations on the B3LYP geometries were carried out at the CCSD(T)/cc‐pVTZ level. Our results display a route to propynal evolving energetically under C2H (nonclassical)+CO and, consequently, accessible in interstellar clouds conditions. This route connects the most stable C3H3O+ isomer (C2‐protonated propadienone) with a species from which propynal may be produced in a dissociative electron recombination reaction. The reaction channel to produce the C3H+O evolves basically through two TSs and presents an endothermicity of 63.9 kcal/mol at 2000 K. According to our Gibbs energy profiles, the C2‐protonated propadienone is the most stable species at low–moderate temperatures and, consequently, could play a certain role in interstellar chemistry. On the contrary, in combustion chemistry conditions (2000 K) the C2H (nonclassical)+CO products are the most thermodynamically favored species. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 35–42, 2000 相似文献
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Ab initio calculations at the post Hartree–Fock level were performed on complexes of acetylene with hydrogen, nitrogen, and argon. Total energies, optimum geometries, and binding energies were calculated, using the 6-311G** and the 6-31+G(2df,2pd) basis sets. Calculations showed the complexes to be more stable than the separate entities, with the exception of the acetylene–hydrogen complex. 相似文献
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Lili Sun Yingfei Chang Bo Hong Rongshun Wang 《International journal of quantum chemistry》2007,107(5):1241-1247
Based on the D3 C32 fullerene, the equilibrium geometries, electronic structures, and binding energies of the endohedral fullerenes X0/n+@C32 (X = H, Li, Na, K, Be, Mg, Ca, B, Al, C, Si, N, P, n = 1–3) have been calculated using the DFT/B3LYP/6‐31G(d) method. The results show that the C32 cages are slightly enlarged due to encapsulation, and the sizes of non‐neutral molecules are smaller than the corresponding neutral ones. Cages containing Li, Na, and Ca and most of the cations, except Na+ and K+, are energetically favorable. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
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Kawahara S Tsuzuki S Uchimaru T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(15):4458-4464
Molecular interactions between pi systems having different pi-electron character (benzene, hexafluorobenzene, and borazine), and a Lewis acid/base (borane and ammonia) were theoretically studied. An attractive interaction between benzene, the electron-rich pi system, and borane was observed. On the other hand, repulsive interactions between benzene and ammonia was observed when the lone pair of nitrogen points toward the benzene ring. In contrast, an attractive interaction between hexafluorobenzene, an electron-deficient pi system, and ammonia was observed. Unexpectedly, a weak attractive interaction between hexafluorobenzene and borane was also observed. Borazine shows an interaction both to borane and ammonia. The attraction between the nitrogen atom of borazine and borane was larger than that between the boron atom of borazine and ammonia. 相似文献