The Smallest “Aurophilic Species”

2009 ◽  
Vol 64 (4) ◽  
pp. 388-394 ◽  
Author(s):  
Raphael J. F. Berger
Keyword(s):  
Ab Initio ◽  
Molecular Species ◽  
Structural Parameters ◽  
Relativistic Effects ◽  
Closed Shell ◽  
Basis Sets ◽  
Ab Initio Methods ◽  
Relativistic Treatment ◽  
Highly Correlated ◽  
Formation Energies

The existence of the C2v symmetric closed-shell di[gold(I)]hydronium cation [Au2H]+ (1), is predicted. It is shown that 1 is the smallest possible molecular species containing aurophilic contacts. Equilibrium structural parameters, vibrational frequencies and formation energies of 1 from Au+ and AuH, have been calculated, employing a series of highly correlated but available standard relativistic ab initio methods up to CCSD(T) level of theory and all-electron basis sets of quadruple-ζ quality with double polarizations. Relativistic effects have been taken into account by employing pseudorelativistic electron core potentials (ECP) or a scalar relativistic treatment using a Douglas-Kroll-Heß Hamiltonian of 2nd, 3rd and 4th order (DKH2, DKH3, DKH4).

Conformational Stability and Structural Determination of Vinyldichlorosilane by ab initio Calculations

1999 ◽  
Vol 54 (8-9) ◽  
pp. 503-506
Author(s):  
Mohammad A. Qtaitat
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Structural Parameters ◽  
Conformational Stability ◽  
Basis Sets ◽  
Structural Determination

The Conformational stability and barriers of interconversion between the eis and gauche conformers of vinyldichlorosilane, CH2CHSiHCl2 , have been studied using ab initio calculations employing the RHF/3-21G* and RHF/6-31G* basis sets. The eis conformer was found to be more stable than the gauche one by 45 cm-1 (539 J/mol) and 140 cm-1 (1.68 kJ/mol) from the RHF/3-21G* and RHF/6-31G* basis sets, respectively. Additionally, the structural parameters of both rotamers have been calculated. These results are compared with results of related molecules.

Quantum-Chemical Ab Initio Calculations on Ala-(C5H5Al) and Galabenzene (C5H5Ga)

2014 ◽  
Vol 69 (7) ◽  
pp. 349-359 ◽  
Author(s):  
Stefanie Mersmann ◽  
Halima Mouhib ◽  
Matthias Baldofski ◽  
Gerhard Raabe
Keyword(s):  
Ab Initio ◽  
Quantum Chemical ◽  
Density Functional ◽  
Normal Modes ◽  
Closed Shell ◽  
Basis Sets ◽  
Moderate Intensity ◽  
Spectral Curves ◽  
Singlet States ◽  
Td Dft

1Quantum-chemical ab initio and time-dependent density functional theory (TD-DFT) calculations employing various basis sets were used to elucidate the spatial as well as the electronic structure of C5H5Al () and C5H5Ga (2) (ala- and galabenzene). The lowest closed shell singlet states of both compounds were found to have a non-planar structure of CS symmetry with C-X-C bond angles of about 116° (MP2/6-311++G**) and 125° (CCSD/aug-cc-pVDZ). At approximately 103°, the corresponding angles of the lowest triplets are significantly smaller. The lowest triplet state of alabenzene is also non-planar (CS) at the MP2 level while optimization with the CCSD and the CASPT2 method resulted in planar structures with C2v symmetry. The corresponding state of galabenzene has C2v symmetry at all levels of optimization. The relative stability of the lowest closed shell singlet and the lowest triplet (ΔE(T1-S0)) state is small and its sign even strongly method-dependent. However, according to the highest levels of theory applied in this study the singlet states of both molecules are slightly lower in energy than the corresponding triplets with singlet/triplet gaps between about 0.5 and 5.8 kcal/mol in favour of the singlet states. Most of the applied methods give a slightly smaller splitting for ala- than for galabenzene. Independent of the applied method (TD-DFT/CAM-B3LYP/6-311++G(3df,3pd)//MP2/6- 311++G** or SAC-CI/6-31++G(3df,3pd)//MP2/6-311++G**), the general shape of the calculated UV/VIS spectral curves are quite similar for the lowest singlet states of ala- and galabenzene, and the same applies to the spectra of the normal modes. The calculated UV/VIS spectra of C5H5Al and C5H5Ga are featured by long wavelength bands of moderate intensity around 900 nm at the TD-DFT and between 1300 and 1500 nm at the SAC-CI level. According to both methods these bands are predominantly due to HOMO(π)→LUMO(σ*) transitions. The results of isodesmic bond separation reactions for the singlet states indicate some degree of stabilization due to delocalization in both of the title compounds. With our best values between 29 and 32 kcal/mol this stabilization appears to be only slightly less than the previously reported value for borabenzene (∼38 kcal/mol).

CH2 revisited

2004 ◽  
Vol 82 (6) ◽  
pp. 684-693 ◽  
Author(s):  
Apostolos Kalemos ◽  
Thom H Dunning Jr. ◽  
Aristides Mavridis ◽  
James F Harrison
Keyword(s):  
Experimental Data ◽  
Electronic Structure ◽  
Potential Energy ◽  
Ab Initio ◽  
Key Words ◽  
State Of The Art ◽  
Basis Sets ◽  
Ab Initio Methods ◽  
H Channels ◽  
Potential Curves

The first four states of the CH2 molecule ([Formula: see text]3B1, ã1 A1, [Formula: see text]1A1, and [Formula: see text]1A1) are examined using state-of-the-art ab initio methods and basis sets. The construction of potential energy curves with respect to the C + H2 and CH + H channels provides significant clues to understanding the geometric and electronic structure of the above states. All of our numerical findings are in excellent agreement with the existing experimental data. Key words: CH2, MRCI, potential curves, vbL icons.

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