201
|
Wang Y, Szczepanski J, Vala M. Silver-carbon cluster AgC3: structure and infrared frequencies. J Phys Chem A 2008; 112:11088-92. [PMID: 18844337 DOI: 10.1021/jp805181m] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Silver-carbon clusters were formed by dual Nd:YAG laser vaporization, trapped in a solid Ar matrix at 12 K, and investigated by infrared spectroscopy. Two new infrared absorption bands were observed at 1827.8 and 1231.6 cm(-1). Isotopic ((13)C) substitution experiments were performed to aid in their assignment. Possible structures considered for the carrier of these bands were Ag(m)C(n) with m = 1 and 2 and n = 1-3, all of which were investigated by density functional theory calculations. The geometries and associated vibrational harmonic-mode frequencies of these clusters were computed with the MPW1PW91 functional and SDD basis set. Both calculations and (13)C-isotopic substitution experiments indicate that the new bands are due to the asymmetric and symmetric C=C stretching modes, respectively, in near-linear AgC3.
Collapse
Affiliation(s)
- Yun Wang
- Department of Chemistry and Center for Chemical Physics, University of Florida, Gainesville, Florida 32611-7200, USA
| | | | | |
Collapse
|
202
|
Adachi M, Saitoh Y, Chiba A, Narumi K, Yamada K, Kaneko T. Monte Carlo particle trajectory simulation for classification of C3+ cluster ion structure utilizing Coulomb explosion imaging. Radiat Phys Chem Oxf Engl 1993 2008. [DOI: 10.1016/j.radphyschem.2008.05.049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
203
|
Pichierri F. Molecular structure of the octatetranyl anion, C8H-: a computational study. J Phys Chem A 2008; 112:7717-22. [PMID: 18666765 DOI: 10.1021/jp710297g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The equilibrium molecular structure of the octatetranyl anion, C8H(-), which has been recently detected in two astronomical environments, is investigated with the aid of both ab initio post-Hartree-Fock and density functional theory (DFT) calculations. The model chemistry adopted in this study was selected after a series of benchmark calculations performed on molecular acetylene for which accurate gas-phase structural data are available. Geometry optimizations performed at the CCSD/6-311+G(2d,p), QCISD/6-311+G(2d,p), and MP4(SDQ)/6-311+G(2d,p) levels of theory yield for C8H(-) an interesting polyyne-type structure that defies the chemical formula displaying a simple alternation of triple and single carbon-carbon bonds, [:C[triple bond]C-C[triple bond]C-C[triple bond]C-C[triple bond]CH](1-). In the optimized geometry of C8H(-), as one proceeds from the naked carbon atom on one side of the chain to the CH unit on the opposite side of the chain, the short (formally triple) carbon-carbon bonds decrease in length from 1.255 to 1.213 A whereas the long (formally single) carbon-carbon bonds increase (albeit only slightly) in length from 1.362 to 1.378 A (CCSD results). In striking contrast, both MP2 and DFT (B3LYP and PBE0) calculations fail in reproducing the pattern of the carbon-carbon bond lengths obtained with the CCSD, QCISD, and MP4 methods. The structures of three shorter n-even chains, C(n)H(-) (n = 2, 4, and 6), along with those of four n-odd compounds (n = 3, 5, 7, and 9) are also investigated at the CCSD/6-311+G(2d,p) level of theory.
Collapse
Affiliation(s)
- Fabio Pichierri
- G-COE Laboratory, Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-07, Sendai 980-8579, Japan.
| |
Collapse
|
204
|
|
205
|
|
206
|
Szczepanski J, Wang Y, Vala M. Copper−Carbon Cluster CuC3: Structure, Infrared Frequencies, and Isotopic Scrambling. J Phys Chem A 2008; 112:4778-85. [DOI: 10.1021/jp801111m] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jan Szczepanski
- Department of Chemistry and Center for Chemical Physics, University of Florida, Gainesville, Florida 32611-7200
| | - Yun Wang
- Department of Chemistry and Center for Chemical Physics, University of Florida, Gainesville, Florida 32611-7200
| | - Martin Vala
- Department of Chemistry and Center for Chemical Physics, University of Florida, Gainesville, Florida 32611-7200
| |
Collapse
|
207
|
Abstract
Investigators have recorded the electronic spectra of assorted carbon-chain systems in the gas phase using a variety of methods, ranging from direct cavity ringdown absorption spectroscopy to photofragmentation techniques that utilize the cooling capabilities of an ion trap. We summarize the results from these studies and compare them with astronomical measurements of the diffuse interstellar band (DIB) absorptions. Although carbon chains comprising up to a handful of carbon atoms cannot be the carrier species, we explore which chains remain viable. In particular, the 1Σu+–X1Σg+ transitions of the odd-numbered carbon chains (n = 17,19,…) possess large oscillator strengths and lie in the 400–900-nm DIB range. The origin bands of larger bare carbon rings, such as C18, have also been observed, with striking similarities to some DIB measurements at high resolution, although at other wavelengths. Finally, we consider recently obtained electronic spectra of metal-containing carbon chains.
Collapse
Affiliation(s)
- Evan B. Jochnowitz
- Department of Chemistry, University of Basel, CH-4056 Basel, Switzerland;,
| | - John P. Maier
- Department of Chemistry, University of Basel, CH-4056 Basel, Switzerland;,
| |
Collapse
|
208
|
Ranković R, Jerosimić S, Perić M. Theoretical investigation of the vibronic spectrum in the X(2)Pi(u) electronic state of C(6)(+). J Chem Phys 2008; 128:154302. [PMID: 18433204 DOI: 10.1063/1.2894312] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
In this study we employ the recently developed model for handling the Renner-Teller effect in Pi electronic states of six-atomic molecules with linear equilibrium geometry to calculate the vibronic spectrum in the X(2)Pi(u) electronic state of the C(6)(+) ion. The applied model Hamiltonian excludes the stretching vibrations and end-over-end rotations. On the other hand, it considers the interplay between the vibronic and spin-orbit couplings. The parameters determining the shape of the bending potential energy surfaces are computed by means of a Density functional theory, and the spin-orbit coupling constant by the Multireference CI program using state-averaged complete active space self-consistent field (SA-CASSCF) wavefunctions. The results of the present study are expected to motivate and help future experimental investigations on C(6)(+).
Collapse
Affiliation(s)
- Radomir Ranković
- Faculty of Physical Chemistry, University of Belgrade, Belgrade, Serbia
| | | | | |
Collapse
|
209
|
Arulmozhiraja S, Ohno T. CCSD calculations on C14, C18, and C22 carbon clusters. J Chem Phys 2008; 128:114301. [DOI: 10.1063/1.2838200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
210
|
|
211
|
Shi Y, Ervin KM. Hydrogen Atom Transfer Reactions of C2-, C4-, and C6-: Bond Dissociation Energies of Linear H−C2n- and H−C2n (n = 1, 2, 3). J Phys Chem A 2008; 112:1261-7. [DOI: 10.1021/jp077181c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yang Shi
- Department of Chemistry and Chemical Physics Program, University of Nevada, Reno, 1664 North Virginia Street, Reno, Nevada 89557-0216
| | - Kent M. Ervin
- Department of Chemistry and Chemical Physics Program, University of Nevada, Reno, 1664 North Virginia Street, Reno, Nevada 89557-0216
| |
Collapse
|
212
|
Zhang F, Gu X, Kaiser RI, Bettinger H. A reinvestigation of the gas phase reaction of boron atoms, 11B(2Pj)/10B(2Pj) with acetylene, C2H2(X1Σg+). Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2007.10.067] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
213
|
Perić M, Petković M, Jerosimić S. Renner–Teller effect in five-atomic molecules: Ab initio investigation of the spectrum of. Chem Phys 2008. [DOI: 10.1016/j.chemphys.2007.07.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
214
|
van Hemert M, van Dishoeck E. Photodissociation of small carbonaceous molecules of astrophysical interest. Chem Phys 2008. [DOI: 10.1016/j.chemphys.2007.08.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
215
|
Yang S, Kertesz M. Linear Cn Clusters: Are They Acetylenic or Cumulenic? J Phys Chem A 2007; 112:146-51. [DOI: 10.1021/jp076805b] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Shujiang Yang
- Department of Chemistry, Georgetown University, Washington DC 20057-1227
| | - Miklos Kertesz
- Department of Chemistry, Georgetown University, Washington DC 20057-1227
| |
Collapse
|
216
|
Calvo F, Lépine F, Baguenard B, Pagliarulo F, Concina B, Bordas C, Parneix P. Evidence for cluster shape effects on the kinetic energy spectrum in thermionic emission. J Chem Phys 2007; 127:204312. [PMID: 18052432 DOI: 10.1063/1.2804861] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Experimental kinetic energy release distributions obtained for the thermionic emission from C(n) (-) clusters, 10< or =n< or =20, exhibit significant non-Boltzmann variations. Using phase space theory, these different features are analyzed and interpreted as the consequence of contrasting shapes in the daughter clusters; linear and nonlinear isomers have clearly distinct signatures. These results provide a novel indirect structural probe for atomic clusters associated with their thermionic emission spectra.
Collapse
Affiliation(s)
- F Calvo
- LASIM, Université Claude Bernard Lyon 1, 43 Blvd. du 11 Novembre 1918, Villeurbanne Cedex, France.
| | | | | | | | | | | | | |
Collapse
|
217
|
Massó H, Veryazov V, Malmqvist PÅ, Roos BO, Senent ML. Ab initio characterization of C5. J Chem Phys 2007; 127:154318. [DOI: 10.1063/1.2759206] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
|
218
|
|
219
|
Fernandéz-Lima FA, Ponciano CR, da Silveira EF, Nascimento MAC. Experimental and theoretical characterization of the Cn=2,16- clusters produced by 337nm UV laser. Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2007.08.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
|
220
|
Montagnon L, Spiegelman F. Self-consistent field tight-binding model for neutral and (multi-) charged carbon clusters. J Chem Phys 2007; 127:084111. [PMID: 17764233 DOI: 10.1063/1.2759210] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A semiempirical model for carbon clusters modeling is presented, along with structural and dynamical applications. The model is a tight-binding scheme with additional one- and two-center distance-dependent electrostatic interactions treated self-consistently. This approach, which explicitly accounts for charge relaxation, allows us to treat neutral and (multi-) charged clusters not only at equilibrium but also in dissociative regions. The equilibrium properties, geometries, harmonic spectra, and relative stabilities of the stable isomers of neutral and singly charged clusters in the range n=1-14, for C(20) and C(60), are found to reproduce the results of ab initio calculations. The model is also shown to be successful in describing the stability and fragmentation energies of dictations in the range n=2-10 and allows the determination of their Coulomb barriers, as examplified for the smallest sizes (C(2) (2+),C(3) (2+),C(4) (2+)). We also present time-dependent mean-field and linear response optical spectra for the C(8) and C(60) clusters and discuss their relevance with respect to existing calculations.
Collapse
Affiliation(s)
- Laurent Montagnon
- Laboratoire de Chimie et de Physique Quantique, UMR 5626, IRSAMC, CNRS et Université Paul Sabatier, 118 Route de Narbornne, 31062 Toulouse, France
| | | |
Collapse
|
221
|
Massó H, Senent ML, Rosmus P, Hochlaf M. Electronic structure calculations on the C4 cluster. J Chem Phys 2007; 124:234304. [PMID: 16821915 DOI: 10.1063/1.2187972] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The ground and the electronically excited states of the C4 radical are studied using interaction configuration methods and large basis sets. Apart from the known isomers [l-C4(X(3)Sigmag (-)) and r-C4(X(1)Ag)], it is found that the ground singlet surface has two other stationary points: s-C4(X(1)Ag) and d-C4(X(1)A1). The d-C4 form is the third isomer of this cluster. The isomerization pathways from one form to the other show that deep potential wells are separating each minimum. Multireference configuration interaction studies of the electronic excited states reveal a high density of electronic states of these species in the 0-2 eV energy ranges. The high rovibrational levels of l-C4((3)Sigmau (-)) undergo predissociation processes via spin-orbit interactions with the neighboring (5)Sigmag + state.
Collapse
Affiliation(s)
- H Massó
- Departamento de Astrofisica Molecular e Infrarroja, Instituto de Estructura de la Materia, CSIC, Serrano 121, Madrid 28006, Spain
| | | | | | | |
Collapse
|
222
|
Belau L, Wheeler SE, Ticknor BW, Ahmed M, Leone SR, Allen WD, Schaefer HF, Duncan MA. Ionization Thresholds of Small Carbon Clusters: Tunable VUV Experiments and Theory. J Am Chem Soc 2007; 129:10229-43. [PMID: 17655303 DOI: 10.1021/ja072526q] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Small carbon clusters (Cn, n = 2-15) are produced in a molecular beam by pulsed laser vaporization and studied with vacuum ultraviolet (VUV) photoionization mass spectrometry. The required VUV radiation in the 8-12 eV range is provided by the Advanced Light Source (ALS) at the Lawrence Berkeley National Laboratory. Mass spectra at various ionization energies reveal the qualitative relative abundances of the neutral carbon clusters produced. By far the most abundant species is C3. Using the tunability of the ALS, ionization threshold spectra are recorded for the clusters up to 15 atoms in size. The ionization thresholds are compared to those measured previously with charge-transfer bracketing methods. To interpret the ionization thresholds for different cluster sizes, new ab initio calculations are carried out on the clusters for n = 4-10. Geometric structures are optimized at the CCSD(T) level with cc-pVTZ (or cc-pVDZ) basis sets, and focal point extrapolations are applied to both neutral and cation species to determine adiabatic and vertical ionization potentials. The comparison of computed and measured ionization potentials makes it possible to investigate the isomeric structures of the neutral clusters produced in this experiment. The measurements are inconclusive for the n = 4-6 species because of unquenched excited electronic states. However, the data provide evidence for the prominence of linear structures for the n = 7, 9, 11, 13 species and the presence of cyclic C10.
Collapse
Affiliation(s)
- Leonid Belau
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA
| | | | | | | | | | | | | | | |
Collapse
|
223
|
Hochlaf M, Nicolas C, Poisson L. Photoionization of C4 molecular beam: Ab initio calculations. J Chem Phys 2007; 127:014310. [PMID: 17627349 DOI: 10.1063/1.2746032] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Large computations are performed on the C(4) (+) cation in order to characterize its stable isomers and its lowest electronic excited states using configuration interaction methods and large basis sets. Several stable isomers are found including a linear C(4) (+)(l-C(4) (+)), a rhombic C(4) (+)(r-C(4) (+)) (or cyclic), and a branched (d-C(4) (+)) structure. Our calculations show a high density of electronic states for all of these isomers favoring their interactions. By combining the present ab initio data and those on neutral C(4), the l-C(4)(X)+hnu-->l-C(4) (+)(X(+))+e(-), d-C(4)(X)+hnu-->d-C(4) (+)(X(+))+e(-), and r-C(4)(X)+hnu-->r-C(4) (+)(X(+))+e(-) vertical photoionization transition energies are computed at 10.87, 10.92, and 10.77 eV, respectively. Photoionizing a C(4) molecular beam results on an onset at 10.4-10.5 eV and then to a linear increase of the signal due to the opening of several ionization channels involving most of the C(4) and C(4) (+) isomers and electronic states.
Collapse
Affiliation(s)
- Majdi Hochlaf
- Laboratoire de Chimie Théorique, Université de Marne la Vallée, F 77454 Champs sur Marne, France
| | | | | |
Collapse
|
224
|
Neubauer-Guenther P, Giesen TF, Schlemmer S, Yamada KMT. High resolution infrared spectra of the linear carbon cluster C7: The ν4 stretching fundamental band and associated hot bands. J Chem Phys 2007; 127:014313. [PMID: 17627352 DOI: 10.1063/1.2749520] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
High resolution infrared spectra of the nu(4) fundamental antisymmetric stretching mode and associated hot bands of the linear carbon cluster C(7) were recorded using a tunable diode laser spectrometer in the frequency range of 2135-2141 cm(-1). Spectra of the nu(4) fundamental, nu(4)+nu(11)-nu(11), nu(4)+2nu(11)-2nu(11), and nu(4)+nu(8)-nu(8), bands have been analyzed and are compared to recent experimental results and high level ab initio calculations. In particular, the presented results give experimental evidence for the rigidity of C(7) and confirm theoretical predictions of a rather regular chain molecule, similar to the cases of C(4), C(5), and C(9). For the two energetically low-lying bending modes, nu(8) and nu(11), the rotational constants differ by less than 0.2%, from the ground state value, B(0)=0.030 624 4(28) cm(-1), in good agreement with the recent calculations by Botschwina [Chem. Phys. Lett. 354, 148 (2002)]. From the hot band analysis and the [script-l]-type doubling constant q, experimental values for the band origins of the nu(8) and nu(11) fundamentals have been derived.
Collapse
|
225
|
Huang YR, Knippenberg S, Hajgató B, François JP, Deng JK, Deleuze MS. Imaging Momentum Orbital Densities of Conformationally Versatile Molecules: A Benchmark Theoretical Study of the Molecular and Electronic Structures of Dimethoxymethane. J Phys Chem A 2007; 111:5879-97. [PMID: 17566995 DOI: 10.1021/jp0719964] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The main purpose of the present work is to predict from benchmark many-body quantum mechanical calculations the results of experimental studies of the valence electronic structure of dimethoxymethane employing electron momentum spectroscopy, and to establish once and for all the guidelines that should systematically be followed in order to reliably interpret the results of such experiments on conformationally versatile molecules. In a first step, accurate calculations of the energy differences between stationary points on the potential energy surface of this molecule are performed using Hartree-Fock (HF) theory and post-HF treatments of improving quality (MP2, MP3, CCSD, CCSD(T), along with basis sets of increasing size. This study focuses on the four conformers of this molecule, namely the trans-trans (TT), trans-gauche (TG), gauche-gauche (G+G+), and gauche-gauche (G+G-) structures, belonging to the C2v, C1, C2, and Cs symmetry point groups, respectively. A focal point analysis supplemented by suited extrapolations to the limit of asymptotically complete basis sets is carried out to determine how the conformational energy differences at 0 K approach the full CI limit. In a second step, statistical thermodynamics accounting for hindered rotations is used to calculate Gibbs free energy corrections to the above energy differences, and to evaluate the abundance of each conformer in the gas phase. It is found that, at room temperature, the G+G+ species accounts for 96% of the conformational mixture characterizing dimethoxymethane. In a third step, the valence one-electron and shake-up ionization spectrum of dimethoxymethane is analyzed according to calculations on the G+G+ conformer alone by means of one-particle Green's function [1p-GF] theory along with the benchmark third-order algebraic diagrammatic construction [ADC(3)] scheme. A complete breakdown of the orbital picture of ionization is noted at electron binding energies above 22 eV. A comparison with available (e,2e) ionization spectra enables us to identify specific fingerprints of through-space orbital interactions associated with the anomeric effect. At last, based on our 1p-GF/ADC(3) assignment of spectral bands, accurate and spherically averaged (e,2e) electron momentum distributions at an electron impact energy of 1200 eV are computed from the related Dyson orbitals. Very significant discrepancies are observed with momentum distributions obtained for several outer-valence levels using standard Kohn-Sham orbitals.
Collapse
Affiliation(s)
- Y R Huang
- Research group of Theoretical Chemistry, Department SBG, University of Hasselt, Agoralaan, Gebouw D, B3590 Diepenbeek, Belgium
| | | | | | | | | | | |
Collapse
|
226
|
Botschwina P. Coupled Cluster Study of the Linear Carbon Chains C2n+1 (n = 5−9). J Phys Chem A 2007; 111:7431-6. [PMID: 17583326 DOI: 10.1021/jp070922p] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Making use of the coupled cluster variant CCSD(T) in conjunction with Dunning's cc-pVTZ basis set, equilibrium structures and complete harmonic force fields have been calculated for the linear carbon chains of type C2n+1 with n = 5-9. With the exception of C3, which is a well-known "floppy" molecule with an extremely shallow bending potential, all members of the C2n+1 series up to C19 appear to behave like fairly normal semirigid molecules. The IR active bending vibrations of lowest wavenumber for C17 and C19, which may be of interest to forthcoming far-infrared astronomy, are predicted to occur at 13.1 and 11.1 cm(-1), respectively, with corresponding absolute IR intensities of 6.6 and 5.9 km mol-1. Huge IR intensities are calculated for one antisymmetric stretching vibration per chain (19,948, 29,632, and 30,040 km mol(-1) for C15, C17, and C19, respectively). A quantitative description of these vibrations may require the explicit consideration of anharmonicity effects and electronic structure calculations going beyond CCSD(T).
Collapse
Affiliation(s)
- Peter Botschwina
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstr. 6, D-37077 Göttingen, Germany
| |
Collapse
|
227
|
Zhang C, Sun W, Cao Z. Most stable structure of fullerene[20] and its novel activity toward addition of alkene: A theoretical study. J Chem Phys 2007; 126:144306. [PMID: 17444711 DOI: 10.1063/1.2716642] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Structures and stabilities of fullerene C20 and C20- have been investigated by the density functional theory and CCSD(T) calculations. In consideration of the Jahn-Teller distortion of Ih-symmetric C20, possible subgroup symmetries have been used in the full geometry optimization. On the basis of relative energetics, vibrational analyses, and electron affinities, fullerenes C20 and C20- have most stable D2h and Ci structures, respectively. The controversy on the relative stability of fullerene[20] arises from the use of different subgroups in calculation and the basis set dependence in vibrational analysis. Predicted nucleus-independent chemical shift values show that the most stable fullerene C20 and its derivatives C20(C2H2)n and C20(C2H4)n (n=1-3) exhibit remarkable aromaticity, while C20(C2H2)4 and C20(C2H4)4 have no spherical aromaticity. The C20 (D2h) cage has remarkable activity toward the addition of olefin, and such feasibility of the addition reaction is ascribed to strong bonding interactions among frontier molecular orbitals from C20 and olefin. Calculations indicate that both C20(C2H2)n and C20(C2H4)n have similar features in electronic spectra.
Collapse
Affiliation(s)
- Congjie Zhang
- School of Chemistry and Materials Science, Shaanxi Normal University, Xi'an 710062, China.
| | | | | |
Collapse
|
228
|
Kamiya M, Hirata S. Higher-order equation-of-motion coupled-cluster methods for electron attachment. J Chem Phys 2007; 126:134112. [PMID: 17430021 DOI: 10.1063/1.2715575] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
High-order equation-of-motion coupled-cluster methods for electron attachment (EA-EOM-CC) have been implemented with the aid of the symbolic algebra program TCE into parallel computer programs. Two types of size-extensive truncation have been applied to the electron-attachment and cluster excitation operators: (1) the electron-attachment operator truncated after the 2p-1h, 3p-2h, or 4p-3h level in combination with the cluster excitation operator after doubles, triples, or quadruples, respectively, defining EA-EOM-CCSD, EA-EOM-CCSDT, or EA-EOM-CCSDTQ; (2) the combination of up to the 3p-2h electron-attachment operator and up to the double cluster excitation operator [EA-EOM-CCSD(3p-2h)] or up to 4p-3h and triples [EA-EOM-CCSDT(4p-3h)]. These methods, capable of handling electron attachment to open-shell molecules, have been applied to the electron affinities of NH and C2, the excitation energies of CH, and the spectroscopic constants of all these molecules with the errors due to basis sets of finite sizes removed by extrapolation. The differences in the electron affinities or excitation energies between EA-EOM-CCSD and experiment are frequently in excess of 2 eV for these molecules, which have severe multideterminant wave functions. Including higher-order operators, the EA-EOM-CC methods predict these quantities accurate to within 0.01 eV of experimental values. In particular, the 3p-2h electron-attachment and triple cluster excitation operators are significant for achieving this accuracy.
Collapse
Affiliation(s)
- Muneaki Kamiya
- Quantum Theory Project, Department of Chemistry, University of Florida, Gainesville, Florida 32611-8435, USA
| | | |
Collapse
|
229
|
Saha S, Western CM. Experimental and ab initio study of a new D 1Deltag state of the C3 radical. J Chem Phys 2007; 125:224307. [PMID: 17176141 DOI: 10.1063/1.2399528] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We report here the first observation of the D (1)Delta(g) state of the C(3) radical, which provides the first comprehensively analyzed example of the dynamic Renner-Teller splitting in Delta symmetry. Two color double resonance spectroscopy via the A (1)Pi(u) state was employed to experimentally probe an extensive range of vibronic levels in this D (1)Delta(g) state, covering all three modes of vibration of C(3). The analysis was supported by ab initio potential energy surface calculations on the C(3) radical to outline the lowest eight singlet electronic states. Two methods were used to analyze the Renner-Teller effect. The first method is an empirical Hamiltonian based on normal modes, using harmonic oscillator functions as a basis, with Renner-Teller and other terms added as required, which allows conventional vibrational parameters to be determined. The second is a much larger program that uses the exact kinetic energy operator for a triatomic molecule to calculate vibronic energy levels directly from the Renner-Teller pair of potential energy surfaces. Both methods give a good fit to the experimental results, with only a small adjustment to the ab initio surfaces required for the latter. One of the overall conclusions is that the Renner-Teller effect is rather smaller in the D (1)Delta(g) state than in the A (1)Pi(u) state.
Collapse
Affiliation(s)
- Sudarshana Saha
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | | |
Collapse
|
230
|
Barrientos C, Redondo P, Largo A. Structure and Stability of Small ZnCn Clusters. J Chem Theory Comput 2007; 3:657-64. [DOI: 10.1021/ct6001797] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Carmen Barrientos
- Departamento de Química Física, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid, Spain
| | - Pilar Redondo
- Departamento de Química Física, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid, Spain
| | - Antonio Largo
- Departamento de Química Física, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid, Spain
| |
Collapse
|
231
|
Rodriguez KR, Williams SM, Young MA, Teeters-Kennedy S, Heer JM, Coe JV. Carbon chains and the (5,5) single-walled nanotube: structure and energetics versus length. J Chem Phys 2007; 125:194716. [PMID: 17129159 DOI: 10.1063/1.2397680] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Reliable thermochemistry is computed for infinite stretches of pure-carbon materials including acetylenic and cumulenic carbon chains, graphene sheet, and single-walled carbon nanotubes (SWCNTs) by connection to the properties of finite size molecules that grow into the infinitely long systems. Using ab initio G3 theory, the infinite cumulenic chain (:C[double bond]C[double bond]C[double bond]C:) is found to be 1.9+/-0.4 kcal/mol per carbon less stable in free energy at room temperature than the acetylenic chain (.C[triple bond]C-C[triple bond]C.) which is 24.0 kcal/mol less stable than graphite. The difference between carbon-carbon triple, double, and single bond lengths (1.257, 1.279, and 1.333 A, respectively) in infinite chains is evident but much less than with small hydrocarbon molecules. These results are used to evaluate the efficacy of similar calculations with the less rigorous PM3 semiempirical method on the (5,5) SWCNT, which is too large to be studied with high-level ab initio methods. The equilibrium electronic energy change for C(g)-->C[infinite (5,5) SWCNT] is -166.7 kcal/mol, while the corresponding free energy change at room temperature is -153.3 kcal/mol (6.7 kcal/mol less stable than graphite). A threefold alternation (6.866, 6.866, and 6.823 A) in the ring diameter of the equilibrium structure of infinitely long (5,5) SWCNT is apparent, although the stability of this structure over the constant diameter structure is small compared to the zero point energy of the nanotube. In general, different (n,m) SWCNTs have different infinite tube energetics, as well as very different energetic trends that vary significantly with length, diameter, and capping.
Collapse
Affiliation(s)
- Kenneth R Rodriguez
- Department of Chemistry, The Ohio State University, Columbus, Ohio 43210-1173, USA
| | | | | | | | | | | |
Collapse
|
232
|
|
233
|
Terentyev A, Scholz R, Schreiber M, Seifert G. Theoretical investigation of excited states of C(3). J Chem Phys 2006; 121:5767-76. [PMID: 15367001 DOI: 10.1063/1.1786291] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
In this work, we present ab initio calculations for the potential energy surfaces of C(3) in different electronic configurations, including the singlet ground state [X (1)Sigma(g) (+),((1)A(1))], the triplet ground state [a (3)Pi(u),((3)B(1), (3)A(1))], and some higher excited states. The geometries studied include triangular shapes with two identical bond lengths, but different bond angles between them. For the singlet and triplet ground states in the linear geometry, the total energies resulting from the mixed density functional--Hartree-Fock and quadratic configuration interaction methods reproduce the experimental values, i.e., the triplet occurs 2.1 eV above the singlet. In the geometry of an equilateral triangle, we find a low-lying triplet state with an energy of only 0.8 eV above the energy of the singlet in the linear configuration, so that the triangular geometry yields the lowest excited state of C(3). For the higher excited states up to about 8 eV above the ground state, we apply time-dependent density functional theory. Even though the systematic error produced by this approach is of the order of 0.4 eV, the results give different prospective to insight into the potential energy landscape for higher excitation energies.
Collapse
Affiliation(s)
- A Terentyev
- Institut für Physik, Technische Universität Chemnitz, D-09107 Chemnitz, Germany
| | | | | | | |
Collapse
|
234
|
Mishra S, Vallet V, Poluyanov LV, Domcke W. Calculation of the vibronic structure of the photodetachment spectra of CCCl- and CCBr-. J Chem Phys 2006; 125:164327. [PMID: 17092093 DOI: 10.1063/1.2363193] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The vibronic structure of the closely spaced and strongly coupled X 2Sigma+ and A 2Pi states in the photodetachment spectra of CCCl- and CCBr- has been calculated by considering Sigma-Pi vibronic coupling together with spin-orbit coupling. The stretching modes are treated within the so-called linear-vibronic-coupling model. The vibronic and spin-orbit parameters have been determined by accurate ab initio electronic-structure calculations. While the nonrelativistic vibronic-coupling parameters are of approximately equal strength in CCCl and CCBr, the vibronic-coupling parameters of spin-orbit origin are found to be larger in the latter. The calculated photodetachment spectra of both systems are shown to exhibit a complicated vibronic structure due to strong Sigma-Pi vibronic coupling. The spectral envelopes of the calculated photodetachment spectra exhibit a double-hump reminiscent of strongly coupled Exe Jahn-Teller systems.
Collapse
Affiliation(s)
- Sabyashachi Mishra
- Department of Chemistry, Technical University of Munich, D-85747 Garching, Germany.
| | | | | | | |
Collapse
|
235
|
Boguslavskiy AE, Maier JP. Gas phase electronic spectra of the carbon chains C5, C6, C8, and C9. J Chem Phys 2006; 125:094308. [PMID: 16965081 DOI: 10.1063/1.2276848] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Three electronic absorption systems for C5 at 511, 445, and 232 nm and one for C6, C8, and C9 centered at 228, 259, and 288 nm have been observed in the gas phase. The C5 chain was produced in both discharge and ablation sources and detected using resonant two-color two-photon ionization spectroscopy involving 10.5 eV photons. The decay of the excited singlet electronic states indicates fast intramolecular processes on a subpicosecond time scale. The internal energy is assumed to be trapped in a triplet state for at least 15 micros. Hole-burning experiments on the 2 (3)Sigma(u)- <-- X (3)Sigma(g)- transition of C6, C8, and (1)Sigma(u)+ <-- X (1)Sigma(g)+ of C9 confirm the predissociative nature of the excited electronic states.
Collapse
Affiliation(s)
- A E Boguslavskiy
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland.
| | | |
Collapse
|
236
|
Zhang J, Wu W, Wang L, Chen X, Cao Z. Electronic spectra of linear isoelectronic clusters C2n+1S and C2n+1Cl+ (n = 0-4): an ab initio study. J Phys Chem A 2006; 110:10324-9. [PMID: 16928125 DOI: 10.1021/jp063109n] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Structures and stabilities of linear carbon chains C2n+1S and C2n+1Cl+ (n=0-4) in their ground states have been investigated by the CCSD and B3LYP approaches. The CASSCF calculations have been used to determine geometries of selected excited states of both isoelectronic series. Linear C2n+1S cluster has a cumulenic carbon framework, whereas its isoelectronic C2n+1Cl+ has a dominant character of acetylenic structure in the vicinity of terminal Cl. The vertical excitation energies of low-lying excited states have been calculated by the CASPT2 method. Calculations show that the excitation energies have nonlinear size dependence. The 2(1)Sigma+<--X1Sigma+ transition energy in C2n+1S has a limit of 1.78 eV, as the chain size is long enough. The predicted vertical excitation energies for relatively strong 1(1)Pi<--X1Sigma+ and 2(1)Sigma+<--X1Sigma+ transitions are in reasonable agreement with available experimental values. The spin-orbit effect on the spin-forbidden transition in both series is generally small, and the enhancement of the spin-forbidden transition by spin-orbit coupling exhibits geometrical and electronic structural dependence.
Collapse
Affiliation(s)
- Jinglai Zhang
- Institute of Fine Chemistry and Engineering, Henan University, Kaifeng 475001, China
| | | | | | | | | |
Collapse
|
237
|
Prinzbach H, Wahl F, Weiler A, Landenberger P, Wörth J, Scott LT, Gelmont M, Olevano D, Sommer F, von Issendorff B. C20 Carbon Clusters: Fullerene–Boat–Sheet Generation, Mass Selection, Photoelectron Characterization. Chemistry 2006; 12:6268-80. [PMID: 16823785 DOI: 10.1002/chem.200501611] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Electron-impact ionization in a time-of-flight mass spectrometer of C(20)H(0-3)Br(14-12) probes-secured from C(20)H(20) dodecahedrane by a "brute-force" bromination protocol-provided bromine-free C(20)H(0-2(3)) anions in amounts that allowed the clean mass-separation of the hydrogen-free C(20) (-) ions and the photoelectron (PE) spectroscopic characterization as C(20) fullerene (electron affinity (EA)=2.25+/-0.03 eV, vibrational progressions of 730+/-70). The extremely strained C(20) fullerene ions surfaced as kinetically rather stable entities (lifetime of at least the total flight time of 0.4 ms); they only very sluggishly expel a C(2) unit. The HOMO and LUMO are suggested to be almost degenerate (DeltaE=0.27 eV). The assignment as a fullerene was corroborated by the PE characterization of the C(20) bowl (EA=2.17+/-0.03 eV, vibrational progression of 2060+/-50 cm(-1)) analogously generated from C(20)H(10) corannulene (C(20)H(1-3)Br(9-8) samples) and comparably stable. Highly resolved low-temperature PE spectra of the known C(20) ring (EA=2.49+/-0.03 eV, vibrational progressions 2022+/-45 and 455+/-30 cm(-1)), obtained from graphite, display an admixture of, most probably, a bicyclic isomer (EA=3.40+/-0.03 eV, vibrational progression 455+/-30 cm(-1)). The C(20) (+(-)) and C(20)H(2) (+(-)) cluster ions generated from polybrominated perylene (C(20)H(0-2)Br(12-10)) have (most probably) retained the planar perylene-type skeleton (sheet, EA=2.47+/-0.03 eV, vibrational progressions of 2089+/-30 and 492+/-30 cm(-1) and EA=2.18+/-0.03 eV, vibrational progressions of 2105+/-30 and 468+/-30 cm(-1)).
Collapse
Affiliation(s)
- Horst Prinzbach
- Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, 79104 Freiburg, Germany.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
238
|
|
239
|
|
240
|
Irle S, Zheng G, Wang Z, Morokuma K. The C60 Formation Puzzle “Solved”: QM/MD Simulations Reveal the Shrinking Hot Giant Road of the Dynamic Fullerene Self-Assembly Mechanism. J Phys Chem B 2006; 110:14531-45. [PMID: 16869552 DOI: 10.1021/jp061173z] [Citation(s) in RCA: 215] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The dynamic self-assembly mechanism of fullerene molecules is an irreversible process emerging naturally under the nonequilibrium conditions of hot carbon vapor and is a consequence of the interplay between the dynamics and chemistry of polyyne chains, pi-conjugation and corresponding stabilization, and the dynamics of hot giant fullerene cages. In this feature article we briefly present an overview of experimental findings and past attempts to explain fullerene formation and show in detail how our recent quantum chemical molecular dynamics simulations of the dynamics of carbon vapor far from thermodynamic equilibrium have assisted in the discovery of the combined size-up/size-down "shrinking hot giant" road that leads to the formation of buckminsterfullerene C60, C70, and larger fullerenes. This formation mechanism is the first reported case of order created out of chaos where a distinct covalent bond network of an entire molecule is spontaneously self-assembled to a highly symmetric structure and fully explains the fullerene formation process consistently with all available experimental observations a priori. Experimental evidence suggests that it applies universally to all fullerene formation processes irrespective of the carbon source.
Collapse
Affiliation(s)
- Stephan Irle
- Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
| | | | | | | |
Collapse
|
241
|
|
242
|
Xu SH, Zhang MY, Zhao YY, Chen BG, Zhang J, Sun CC. Stability and property of planar (BN)x clusters. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.03.077] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
243
|
Schreiner PR, Reisenauer HP. The “Non-Reaction” of Ground-State Triplet Carbon Atoms with Water Revisited. Chemphyschem 2006; 7:880-5. [PMID: 16596611 DOI: 10.1002/cphc.200500555] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We introduce a novel experimental setup for the generation of carbon atoms by means of pulsed laser ablation with a pulse rate optimized to avoid warming of the matrix. The combination of this technique with annealing of the matrix, recooling, and spectral recording (e.g. IR) allowed us to differentiate between the reactivity of triplet and singlet carbon atoms towards water under matrix-isolation conditions. Our experimental procedure assures the relaxation of all unreacted carbon atoms to their triplet ground state in the 10 K matrix before spectral recording. In agreement with CCSD(T)/cc-pVTZ+ZPVE computational data and earlier lower level results, we find that triplet carbon atoms indeed do not react with water, despite their high initial energy. Intersystem crossing of the triplet to singlet states of hydroxy carbene are less important, as the barriers for rearrangement of the initial complex of triplet carbon atoms and water to covalently bound species are too high, and dissociation is more likely. We found no evidence for a direct O--H bond-insertion path for triplet carbon atoms. Self-condensation reactions of triplet carbon atoms are clearly favored and yield carbon clusters that show reactivity of their own. The proposed formation of aldoses in extraterrestrial environments can therefore only derive from "hot" carbon atoms or through photoreactions.
Collapse
Affiliation(s)
- Peter R Schreiner
- Institute of Organic Chemistry, Justus-Liebig University, Heinrich-Buff-Ring 58, 35392 Giessen, Germany.
| | | |
Collapse
|
244
|
A coupled cluster study of the IR active bending vibrations of C2n chains (n=2–5) in their 3Σg- electronic ground states. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2005.12.106] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
245
|
Xu SH, Zhang MY, Zhao YY, Chen BG, Zhang J, Sun CC. Stability and properties of planar carbon clusters. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.01.038] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
246
|
Bowling NP, Halter RJ, Hodges JA, Seburg RA, Thomas PS, Simmons CS, Stanton JF, McMahon RJ. Reactive Carbon-Chain Molecules: Synthesis of 1-Diazo-2,4-pentadiyne and Spectroscopic Characterization of Triplet Pentadiynylidene (H−C⋮C−C̈−C⋮C−H). J Am Chem Soc 2006; 128:3291-302. [PMID: 16522111 DOI: 10.1021/ja058252t] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
1-Diazo-2,4-pentadiyne (6a), along with both monodeuterio isotopomers 6b and 6c, has been synthesized via a route that proceeds through diacetylene, 2,4-pentadiynal, and 2,4-pentadiynal tosylhydrazone. Photolysis of diazo compounds 6a-c (lambda > 444 nm; Ar or N2, 10 K) generates triplet carbenes HC5H (1) and HC5D (1-d), which have been characterized by IR, EPR, and UV/vis spectroscopy. Although many resonance structures contribute to the resonance hybrid for this highly unsaturated carbon-chain molecule, experiment and theory reveal that the structure is best depicted in terms of the dominant resonance contributor of penta-1,4-diyn-3-ylidene (diethynylcarbene, H-C[triple bond]C-:C-C[triple bond]C-H). Theory predicts an axially symmetric (D(infinity h)) structure and a triplet electronic ground state for 1 (CCSD(T)/ANO). Experimental IR frequencies and isotope shifts are in good agreement with computed values. The triplet EPR spectrum of 1 (absolute value(D/hc) = 0.6157 cm(-1), absolute value(E/hc) = 0.0006 cm(-1)) is consistent with an axially symmetric structure, and the Curie law behavior confirms that the triplet state is the ground state. The electronic absorption spectrum of 1 exhibits a weak transition near 400 nm with extensive vibronic coupling. Chemical trapping of triplet HC5H (1) in an O2-doped matrix affords the carbonyl oxide 16 derived exclusively from attack at the central carbon.
Collapse
Affiliation(s)
- Nathan P Bowling
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706-1396, USA
| | | | | | | | | | | | | | | |
Collapse
|
247
|
|
248
|
Nicolas C, Shu J, Peterka DS, Hochlaf M, Poisson L, Leone SR, Ahmed M. Vacuum Ultraviolet Photoionization of C3. J Am Chem Soc 2006; 128:220-6. [PMID: 16390150 DOI: 10.1021/ja055430+] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Photoionization efficiency (PIE) curves for C(3) molecules produced by laser ablation are measured from 11.0 to 13.5 eV with tunable vacuum ultraviolet undulator radiation. A step in the PIE curve versus photon energy, obtained with N(2) as the carrier gas, supports the conclusion of very effective cooling of C(3) to its linear (1)Sigma(g)(+) ground state. The second step observed in the PIE curve versus photon energy could be the first experimental evidence of the C(3)(+)((2)Sigma(g)(+)) excited state. The experimental results, complemented by ab initio calculations, suggest a state-to-state vertical ionization energy of 11.70 +/- 0.05 eV between the C(3)(X(1)Sigma(g)(+)) and the C(3)(+)(X(2)Sigma(u)(+)) states. An ionization energy of 11.61 +/- 0.07 eV between the neutral and ionic ground states of C(3) is deduced using the data together with our calculations. Accurate ab initio calculations are performed for both linear and bent geometries on the lowest doublet electronic states of C(3)(+) using Configuration Interaction (CI) approaches and large basis sets. These calculations confirm that C(3)(+) is bent in its electronic ground state, which is separated by a small potential barrier from the (2)Sigma(u)(+) minimum. The gradual increase at the onset of the PIE curve suggests a geometry change between the ground neutral and cationic states. The energies between several doublet states of the ion are theoretically determined to be 0.81, 1.49, and 1.98 eV between the (2)Sigma(u)(+) and the (2)Sigma(g)(+),( 2)Pi(u), (2)Pi(g) excited states of C(3)(+), respectively.
Collapse
Affiliation(s)
- Christophe Nicolas
- Chemical Sciences Division, Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | | | | | | | | | | | | |
Collapse
|
249
|
Smith IWM, Sage AM, Donahue NM, Herbst E, Quan D. The temperature-dependence of rapid low temperature reactions: experiment, understanding and prediction. Faraday Discuss 2006; 133:137-56; discussion 191-230, 449-52. [PMID: 17191447 DOI: 10.1039/b600721j] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Despite the success of the CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme) method in measuring rate coefficients for neutral-neutral reactions of radicals down close to the very low temperatures prevalent in dense interstellar clouds (ISCs), there are still many reactions of potential importance in the chemistry of these objects for which there have been no measurements of low temperature rate coefficients. One important class of reactions is that between atomic and molecular free radicals and unsaturated hydrocarbons; that is, alkynes and alkenes. Based on semi-empirical arguments and correlations of 'room temperature' rate coefficients, k(298 K), for reactions of this type with the difference between the ionisation energy of the alkyne/alkene and the electron affinity of the radical, we suggest which reactions between the radicals, C(3P), O(3P), N(4S), CH, C2H and CN, and carbon chain molecules (Cn) and cyanopolyynes (HC2nCN and NCC2nCN) are likely to be fast at the temperature of dense ISCs. These reactions and rate coefficients have been incorporated into a purely gas-phase model (osu2005) of ISC chemistry. The results of these calculations are presented and discussed.
Collapse
Affiliation(s)
- Ian W M Smith
- University Chemical Laboratories, Lensfield Road, Cambridge, UK.
| | | | | | | | | |
Collapse
|
250
|
Lucotti A, Tommasini M, Zoppo MD, Castiglioni C, Zerbi G, Cataldo F, Casari C, Bassi AL, Russo V, Bogana M, Bottani C. Raman and SERS investigation of isolated sp carbon chains. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2005.10.016] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|