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1.
Ping Qian Wei Song Linan Lu Zhongzhi Yang 《International journal of quantum chemistry》2010,110(10):1923-1937
Various properties of typical structures of water clusters in the n = 2–34 size regime with the change of cluster size have been systematically explored. Full optimizations are carried out for the structures presented in this article at the Hartree–Fock (HF) level using the 6‐31G(d) basis set by taking into account the positions of all atoms within the cluster. The influence of the HF level on the results has been reflected by the comparison between the binding energies of (H2O)n (n = 2–6, 8, 11, 13, 20) calculated at the HF level and those obtained from high‐level ab initio calculations at the second‐order Møller–Plesset (MP2) perturbation theory and the coupled cluster method including singles and doubles with perturbative triples (CCSD(T)) levels. HF is inaccurate when compared with MP2 and CCSD(T), but it is more practical and allows us to study larger systems. The computed properties characterizing water clusters (H2O)n (n = 2–34) include optimal structures, structural parameters, binding energies, hydrogen bonds, charge distributions, dipole moments, and so on. When the cluster size increases, trends of the above various properties have been presented to provide important reference for understanding and describing the nature of the hydrogen bond. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献
2.
《化学:亚洲杂志》2017,12(17):2172-2176
Hydrothermal reactions of metal nitrates and ligand bis(5‐(pyridine‐2‐yl)‐1,2,4‐triazol‐3‐yl)methane (H2L1) gave three cluster compounds, {Cr2}, {Zn12} and {Fe8}. Notably, methylene group of H2L1 was in situ oxidized either to hydroxymethylated (L2‐O)3− in the metallo‐ring {Zn12} or to a rigid carbonylated (L3=O)2− in the screw‐type {Fe8}. In light of comparative experimental results, NO3− was deduced to be of a catalytic role in the ligand oxidation. Metal ion could be regarded as an “induced” tool for clusters generation in self‐assembly process. 相似文献
3.
Gessenildo Pereira Rodrigues Elizete Ventura Silmar Andrade do Monte Mario Barbatti 《Journal of computational chemistry》2016,37(7):675-683
The UV‐induced photochemistry of HCFC‐132b (CF2ClCH2Cl) was investigated by computing excited‐state properties with time‐dependent density functional theory (TDDFT), multiconfigurational second‐order perturbation theory (CASPT2), and coupled cluster with singles, doubles, and perturbative triples (CCSD(T)). Excited states calculated with TDDFT show good agreement with CASPT2 and CCSD(T) results, correctly predicting the main excited‐states properties. Simulations of ultrafast nonadiabatic dynamics in the gas phase were performed, taking into account 25 electronic states at TDDFT level starting in two different spectral windows (8.5 ± 0.25 and 10.0 ± 0.25 eV). Experimental data measured at 123.6 nm (10 eV) is in very good agreement with our simulations. The excited‐state lifetimes are 106 and 191 fs for the 8.5 and 10.0 eV spectral windows, respectively. Internal conversion to the ground state occurred through several different reaction pathways with different products, where 2Cl, C‐Cl bond breakage, and HCl are the main photochemical pathways in the low‐excitation region, representing 95% of all processes. On the other hand, HCl, HF, and C‐Cl bond breakage are the main reaction pathways in the higher excitation region, with 77% of the total yield. © 2015 Wiley Periodicals, Inc. 相似文献
4.
Teobald Kupka Marzena Nieradka Jakub Kaminský Leszek Stobiński 《Magnetic resonance in chemistry : MRC》2013,51(10):676-681
The potential of nuclear magnetic resonance (NMR) technique in probing the structure of porous systems including carbon nanostructures filled with inert gases is analysed theoretically using accurate calculations of neon (21Ne) nuclear magnetic shieldings. The CBS estimates of 21Ne NMR parameters were performed for single atom, its dimer and neon interacting with acetylene, ethylene and 1,3‐cyclopentadiene. Several levels of theory including restricted Hartree‐Fock (RHF), Møller‐Plesset perturbation theory to the second order (MP2), density functional theory (DFT) with van Voorhis and Scuseria's t‐dependent gradient‐corrected correlation functional (VSXC), coupled cluster with single and doubles excitations (CCSD), with single, doubles and triples included in a perturbative way (CCSD(T)) and single, doubles and tripes excitations (CCSDT) combined with polarization‐consistent aug‐pcS‐n series of basis sets were employed. The impact of neon confinement inside selected fullerene cages used as an NMR probe was studied at the RHF/pcS‐2 level of theory. A sensitivity of neon probe to the proximity of multiple CC bonds in C2H2, C2H4, C5H6 and inside C28, C30, C32, C34 and C60 fullerenes was predicted from 21Ne NMR parameters' changes. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
5.
Li Duan Xiang‐Wen Wu Jian‐Ping Ma Yu‐Bin Dong 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(6):m149-m151
The title novel two‐dimensional coordination polymer, {[Zn2(C10H8N3O2)4]·H2O}n, features a {Zn2L2} bimetallic ring repeat unit {L is the 3‐[(1H‐1,2,4‐triazol‐1‐yl)methyl]benzoate ligand}. Each ZnII cation of the bimetallic ring is further bonded to two other L ligands, resulting in a novel infinite two‐dimensional network structure with two channels of different sizes. The crystallographically unique ZnII atom is thus six‐coordinated in a distorted octahedral environment of four carboxylate O atoms and two triazole N atoms. Two of these networks interpenetrate in an orthogonal arrangement to form the full three‐dimensional framework, with disordered water molecules located in the channels. 相似文献
6.
《Chemical physics letters》1987,139(2):134-139
Using our recently implemented closed-shell coupled cluster singles and doubles (CCSD) model, the equilibrium structure and vibrational harmonic frequency of N2, CO, HF and OH− have been determined. This set ofdiatomics was specially chosen so as to represent the range of bonding characteristics found in small molecules. The CCSD results are compared to analogous configuration interaction (CI) predictions and are found to be most similar to CISDQ or CISDTQ. That is, CI including all singles + doubles + quadruples (CISDQ) or CISDQ+all triple excitations (CISDTQ). The agreement of CCSD with CISDQ/CISDTQ is found to be much better for the singly bonded species with the agreement for neutral HF somewhat better than for anionic OH−. We arrive at two major conclusions. First, higher-order effects not present in the CCSD model are less negligible for multiply bonded species and, to a smaller degree, for anionic species as well. Secondly, even for the two types of molecules discussed above, the CCSD results are closer to the CISDQ/CISDTQ predictions than are CISD values. Since CCSD is less computationally time consuming than CISDQ/CISDTQ, we suggest that the CCSD model is one of the best methods available when highly accurate ab initio predictions for chemical species strongly dominated by a single-determinant wavefunction are desired. 相似文献
7.
Zhao‐Cai Liu Qi‐Kui Liu Yan‐An Li Jian‐Ping Ma Yu‐Bin Dong 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(1):31-36
A new nano‐sized rigid double‐armed oxadiazole‐bridged organic ligand, 2,5‐bis{2‐methyl‐5‐[2‐(pyridin‐3‐yl)ethenyl]phenyl}‐1,3,4‐oxadiazole, C30H20N4O, L or (I), which adopts a cis conformation in the solid state, has been synthesized and used to create the two novel metallocycle complexes (2,5‐bis{2‐methyl‐5‐[2‐(pyridin‐3‐yl‐κN)ethenyl]phenyl}‐1,3,4‐oxadiazole)diiodidocadmium(II) dichloromethane monosolvate, [CdI2(C30H20N4O)]·CH2Cl2, (II), and di‐μ‐iodido‐bis[(2,5‐bis{2‐methyl‐5‐[2‐(pyridin‐3‐yl‐κN)ethenyl]phenyl}‐1,3,4‐oxadiazole)copper(I)], [Cu2I2(C30H20N4O)2], (III). Molecules of complex (II) adopts a 20‐membered `0'‐shaped metallocycle structure with crystallographic mirror symmetry. The discrete units are linked into one‐dimensional chains through intermolecular π–π and C—H...π interactions. In (III), the two I atoms and two CuI atoms form a {Cu2(μ‐I)2} cluster. One {Cu2(μ‐I)2} cluster and two L ligands form two 20‐membered monometallic rings in a head‐to‐head fashion, leading to a discrete centrosymmetric `8'‐shaped metallocyclic complex. These metallocycles stack together via two kinds of intermolecular π–π interactions to generate a two‐dimensional network in the ac plane. The luminescence properties of (I)–(III) were investigated in the solid state at room temperature and displayed an obvious red shift. 相似文献
8.
Yutaka Imamura Takeshi Baba Hiromi Nakai 《International journal of quantum chemistry》2008,108(8):1316-1325
Natural bond orbital‐based energy density analysis (NBO‐EDA), which split energies into atomic and bonding contributions, is proposed for correlated methods such as coupled‐cluster singles and doubles (CCSD) and second‐order Møller–Plesset (MP2) perturbation. Applying NBO‐EDA for CCSD and MP2 to ethylene and the Diels–Alder reaction, we are successful in obtaining useful knowledge regarding electron correlation of π‐ and σ‐type orbitals, and clarifying the difference of the reaction barriers and heat of reaction calculated by CCSD and MP2. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
9.
X. Li Y. Zhao X. Jing F. Liu F. Hao 《International journal of quantum chemistry》2006,106(5):1086-1092
The equilibrium geometries, vibrational frequencies, and dissociation energies of rare gas iodine clusters Rg2I?(Rg = Ar, Kr, Xe) were calculated at the Hartree–Fock (HF), second‐order Møller–Plesset (MP2), the coupled cluster method with single and double excitation and a noniterative correction for triple excitations method [CCSD(T)] levels. The title species have bent C2v structure of about 60° angle. The electron correlation effects and relativistic effects on the geometry and stability were investigated at CCSD(T) level. Both effects stabilize title species. The calculated electron affinities are in good agreement with the experimental results available. The effect of high angular momentum functions (g and h) was studied. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 相似文献
10.
The π–π interactions between CO2 and three aromatic molecules, namely benzene (C6H6), pyridine (C5H5N), and pyrrole (C4H5N), which represent common functional groups in metal‐organic/zeoliticimidazolate framework materials, were characterized using high‐level ab initio methods. The coupled‐cluster with single and double excitations and perturbative treatment of triple excitations (CCSD(T)) method with a complete basis set (CBS) was used to calibrate Hartree–Fock, density functional theory, and second‐order M?ller–Plesset (MP2) with resolution of the identity approximation calculations. Results at the MP2/def2‐QZVPP level showed the smallest deviations (only about 1 kJ/mol) compared with those at the CCSD(T)/CBS level of theory. The strength of π–π binding energies (BEs) followed the order C4H5N > C6H6 ~ C5H5N and was roughly correlated with the aromaticity and the charge transfer between CO2 and aromatic molecule in clusters. Compared with hydrogen‐bond or electron donor–acceptor interactions observed during BE calculations at the MP2/def2‐QZVPP level of theory, π–π interactions significantly contribute to the total interactions between CO2 and aromatic molecules. © 2013 Wiley Periodicals, Inc. 相似文献
11.
Ibon Alkorta Fernando Blanco Janet E. Del Bene José Elguero Laura Hernández‐Folgado María‐Luisa Jimeno 《Magnetic resonance in chemistry : MRC》2010,48(1):68-73
The experimental spin–spin coupling constants (SSCCs) for 1,3‐ and 1,4‐difluorobenzene have been determined anew, and found to be consistent with previously determined values. SSCCs for 1,2‐, 1,3‐, and 1,4‐difluorobenzene have been analyzed by comparing them with the coupling constants computed using the second‐order polarization propagator approximation (SOPPA) and the equation‐of‐motion coupled cluster singles and doubles method (EOM‐CCSD). Eighty experimental values have been analyzed using SOPPA calculations, and a subset of 40 values using both SOPPA and EOM‐CCSD approaches. One‐bond coupling constants 1J(C? C) and 1J(C? F) are better described by EOM‐CCSD, whereas one‐bond 1J(C? H) values are better described by SOPPA. An empirical equation is presented which allows for the prediction of unknown coupling constants from computed SOPPA values. A similar approach may prove useful for predicting coupling constants in larger systems. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
12.
Yan‐an Li Qi‐Kui Liu Jian‐Ping Ma Yu‐Bin Dong 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(6):m152-m155
The molecule of 3,5‐bis{4‐[(benzimidazol‐1‐yl)methyl]phenyl}‐4H‐1,2,4‐triazol‐4‐amine (L), C30H24N8, has an antiperiplanar conformation of the two terminal benzimidazole groups and forms two‐dimensional networks along the crystallographic b axis via two types of intermolecular hydrogen bonds. However, in catena‐poly[[[dichloridomercury(II)]‐μ‐3,5‐bis{4‐[(benzimidazol‐1‐yl)methyl]phenyl}‐4H‐1,2,4‐triazol‐4‐amine] dichloromethane hemisolvate], {[HgCl2(C30H24N8)]·0.5CH2Cl2}n, synthesized by the combination of L with HgCl2, the L ligand adopts a synperiplanar conformation. The HgII cation lies in a distorted tetrahedral environment, which is defined by two N atoms and two Cl atoms to form a one‐dimensional zigzag chain. These zigzag chains stack via hydrogen bonds which expand the dimensionality of the structure from one to two. 相似文献
13.
14.
Noboru Watanabe Yohei Kamata Kota Yamauchi Yasuo Udagawa 《Journal of computational chemistry》2001,22(13):1315-1320
Total X‐ray scattering intensity σee(q) is very sensitive to electron correlation effects. In this study σee(q) of N2, CO, and N2O have been computed by the coupled cluster singles and doubles (CCSD) method and compared with configuration interaction singles and doubles (CISD) calculations as well as experimental observations. σee(q) curves by CCSD calculations are rather close to those by CISD, but although small, there still exist some discrepancies between calculated and observed values. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1315–1320, 2001 相似文献
15.
Ashley L. Ringer C. David Sherrill Rollin A. King T. Daniel Crawford 《International journal of quantum chemistry》2008,108(6):1137-1140
Recent photofragment fluorescence excitation (PHOFEX) spectroscopy experiments have observed the Ã1A″ singlet excited state of isocyanogen (CNCN) for the first time. The observed spectrum is not completely assigned and significant questions remain about the excited states of this system. To provide insight into the energetically accessible excited states of CNCN, optimized geometries, harmonic vibrational frequencies, and excitation energies for the first three singlet excited states are determined using equation‐of‐motion coupled‐cluster theory with singles and doubles (EOM‐CCSD) and correlation‐consistent basis sets. Additionally, excited state coupled‐cluster methods which approximate the contributions from triples (CC3) are utilized to estimate the effect of higher‐order correlation on the energy of each excited state. For the Ã1A″ state, our best estimate for T0 is about 42,200 cm?1, in agreement with the experimentally estimated upper limit for the zero‐point level of 42,523 cm?1. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
16.
Lukáš Bučinský Stanislav Biskupič Michal Ilčin Vladimír Lukeš Viliam Laurinc 《Journal of computational chemistry》2011,32(2):356-367
The comparison of coupled cluster with single and double excitations and with perturbative correction of triple excitations [CCSD(T)] ground state potential curves of mercury with rare gases (RG): HgHe and HgXe, at several levels of theory is presented. The scalar relativistic (REL) effects and spin‐orbit coupling effects in the ground state potential curves of these weakly bounded dimers are considered. The CCSD(T) ground state potential curves at the level of the Dirac‐Coulomb Hamiltonian (DCH) are compared with CCSD(T) curves at the level of 4‐component spin‐free modified DCH, the scalar 2nd order Douglas‐Kroll‐Hess (DKH2) and the nonrelativistic (NR‐LL) (Lévy‐Leblond) Hamiltonian. In addition, London‐Drude formula and SCF interaction energy curves are employed in the analysis of different contributions of REL effects in dissociation energies of HgRG and Hg2 dimers. Moreover, the large anharmonicity of the HgHe ground state potential curve is highlighted. The computationally less demanding scalar DKH2 Hamiltonian is employed to calculate the HgXe, Hg2, and Xe2 all electron CCSD(T) ground state potential curves in highly augmented quadruple zeta basis sets. These potential curves are used to simulate the shear viscosity of mercury, xenon, and mercury‐xenon (Hg:Xe) mixture. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011 相似文献
17.
Iterative multireference configuration interaction (IMRCI) is proposed. It is exploited to compute the electronic energies of H\begin{document}$_2$\end{document} O and CH\begin{document}$_2$\end{document} (singlet and triplet states) at equilibrium and non-equilibrium geometries. The potential energy curves of H\begin{document}$_2$\end{document} O, CH\begin{document}$_2$\end{document} (singlet and triplet states) and N\begin{document}$_2$\end{document} have also been calculated with IMRCI as well as the M?ller Plesset perturbation theory (MP2, MP3, and MP4), the coupled cluster method with single and double substitutions (CCSD), and CCSD with perturbative triples correction (CCSD(T)). These calculations demonstrate that IMRCI results are independent of the initial guess of configuration functions in the reference space and converge quickly to the results of the full configuration interaction. The IMRCI errors relative to the full configuration interaction results are at the order of magnitude of 10\begin{document}$^{-5}$\end{document} hartree within just 2-4 iterations. Further, IMRCI provides an efficient way to find on the potential energy surface the leading electron configurations which, as correct reference states, will be very helpful for the single-reference and multireference theoretical models to obtain accurate results. 相似文献
18.
CuH‐Catalysed Hydroamination of Styrene with Hydroxylamine Esters: A Coupled Cluster Scrutiny of Mechanistic Pathways
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Dr. Sven Tobisch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(24):8290-8300
A detailed computational exploration of mechanistic intricacies of the copper(I) hydride (CuH)‐catalysed hydroamination of styrene with a prototype hydroxylamine ester by a recently reported [(dppbz)CuH] catalyst (dppbz≡{P^P}≡1,2‐bis(diphenylphosphino)‐benzene) is presented. A variety of plausible mechanistic avenues have been pursued by means of a sophisticated computational methodology, from which a general understanding of the factors controlling hydroamination catalysis emerged. The catalytically competent {P^P}CuI hydride, which is predominantly present as its dimer, involves in irreversible hydrocupration proceeding with complete 2,1 regioselectivity to form a secondary {P^P}CuI benzyl intermediate. Its interception with benzylamine ester produces the branched tertiary amine product and {P^P}CuI benzoate upon intramolecular SN2 disruption of the amine electrophile′s N?O linkage, to precede a highly rapid, strongly exergonic C?N bond‐forming reductive elimination. The {P^P}CuI benzoate corresponds to the catalyst resting state and its conversion back into the {P^P}CuI hydride upon transmetalation with a hydrosilane is turnover limiting. The effect of electronic perturbations at the amine electrophile upon the reaction rate for productive hydroamination catalysis and also non‐productive reduction of the hydroxylamine ester has been gauged, which unveiled a more fundamental insight into catalytic structure‐performance relationships. 相似文献
19.
Krishnan Ravikumar Balasubramanian Sridhar Jagadeesh Babu Nanubolu Tamilselvan Rajasekaran Basi Venkata Subba Reddy 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(4):322-329
Four structures of oxoindolyl α‐hydroxy‐β‐amino acid derivatives, namely, methyl 2‐{3‐[(tert‐butoxycarbonyl)amino]‐1‐methyl‐2‐oxoindolin‐3‐yl}‐2‐methoxy‐2‐phenylacetate, C24H28N2O6, (I), methyl 2‐{3‐[(tert‐butoxycarbonyl)amino]‐1‐methyl‐2‐oxoindolin‐3‐yl}‐2‐ethoxy‐2‐phenylacetate, C25H30N2O6, (II), methyl 2‐{3‐[(tert‐butoxycarbonyl)amino]‐1‐methyl‐2‐oxoindolin‐3‐yl}‐2‐[(4‐methoxybenzyl)oxy]‐2‐phenylacetate, C31H34N2O7, (III), and methyl 2‐[(anthracen‐9‐yl)methoxy]‐2‐{3‐[(tert‐butoxycarbonyl)amino]‐1‐methyl‐2‐oxoindolin‐3‐yl}‐2‐phenylacetate, C38H36N2O6, (IV), have been determined. The diastereoselectivity of the chemical reaction involving α‐diazoesters and isatin imines in the presence of benzyl alcohol is confirmed through the relative configuration of the two stereogenic centres. In esters (I) and (III), the amide group adopts an anti conformation, whereas the conformation is syn in esters (II) and (IV). Nevertheless, the amide group forms intramolecular N—H...O hydrogen bonds with the ester and ether O atoms in all four structures. The ether‐linked substituents are in the extended conformation in all four structures. Ester (II) is dominated by intermolecular N—H...O hydrogen‐bond interactions. In contrast, the remaining three structures are sustained by C—H...O hydrogen‐bond interactions. 相似文献
20.
Ariel G. De Candia Matias Molnar Leonardo D. Slep Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(5):m121-m126
Although it has not proved possible to crystallize the newly prepared cyclam–methylimidazole ligand 1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane (LIm1), the trans and cis isomers of an NiII complex, namely trans‐aqua{1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}nickel(II) bis(perchlorate) monohydrate, [Ni(C15H30N6)(H2O)](ClO4)2·H2O, (1), and cis‐aqua{1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}nickel(II) bis(perchlorate), [Ni(C15H30N6)(H2O)](ClO4)2, (2), have been prepared and structurally characterized. At different stages of the crystallization and thermal treatment from which (1) and (2) were obtained, a further two compounds were isolated in crystalline form and their structures also analysed, namely trans‐{1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}(perchlorato)nickel(II) perchlorate, [Ni(ClO4)(C15H30N6)]ClO4, (3), and cis‐{1,8‐bis[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}nickel(II) bis(perchlorate) 0.24‐hydrate, [Ni(C20H36N6)](ClO4)2·0.24H2O, (4); the 1,8‐bis[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane ligand is a minor side product, probably formed in trace amounts in the synthesis of LIm1. The configurations of the cyclam macrocycles in the complexes have been analysed and the structures are compared with analogues from the literature. 相似文献