The molecular structure of the (NCCN)<sub>2</sub>and (PCCP)<sub>2</sub>van der Waals dimers

Almeida, Wagner B. De; Resende, Stella M.; Santos, Hélio F. Dos

doi:10.1080/00268979400100951

Cited by 11 publications

(5 citation statements)

References 53 publications

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“…33 Although the PES of (Cy) 2 was explored with Hartree−Fock (HF) computations as early as 1984, 34 this investigation provides the first harmonic vibrational frequencies beyond the HF level of theory. 35 To provide a consistent description of all 3 dimer systems that can be formed from the Cy and Di monomers, this work optimizes various stationary points of (Di) 2 , (Cy) 2 , and Di/Cy and computes the corresponding harmonic vibrational frequencies at the CCSD(T) level of theory with a triple-ζ basis set augmented with two sets of polarization functions as well as diffuse s-and p-type functions. These high-level frequency computations will furnish benchmark values that may be of growing importance in light of the Hessian index discrepancies recently reported between MP2 and density function theory (DFT) computations for simple hydrocarbon/water dimers.…”

Section: Introductionmentioning

confidence: 99%

“…Only the parallel-displaced configuration has been examined in earlier work reporting that the heterogeneous parallel-displaced dimers exhibited appreciably larger interaction energies than their homogeneous counterparts . Although the PES of (Cy) 2 was explored with Hartree–Fock (HF) computations as early as 1984, this investigation provides the first harmonic vibrational frequencies beyond the HF level of theory . To provide a consistent description of all 3 dimer systems that can be formed from the Cy and Di monomers, this work optimizes various stationary points of (Di) 2 , (Cy) 2 , and Di/Cy and computes the corresponding harmonic vibrational frequencies at the CCSD(T) level of theory with a triple-ζ basis set augmented with two sets of polarization functions as well as diffuse s- and p-type functions.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Heterogeneity in Small π-Type Dimers: Homogeneous and Mixed Dimers of Diacetylene and Cyanogen

Copeland

Tschumper

2012

J. Chem. Theory Comput.

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The homo- and heterogeneous dimers of diacetylene (H-C≡C-C≡C-H) and cyanogen (N≡C-C≡N) were studied using ab initio electronic structure computations to probe the effects of heterogeneity on noncovalent interactions between systems with delocalized π electron networks. Full geometry optimizations and harmonic vibrational frequencies were performed using the robust coupled-cluster with single and double and perturbative triple excitations (CCSD(T)) method with the triple-ζ plus 2 sets of polarization functions TZ2P(f,d)++ basis set. Seven basic configurations were examined for each dimer (cross, stacked, parallel-slipped, parallel-tipped, linear, T-shaped and Y-shaped), but only four stationary points were identified on the potential energy surfaces (PESs) of the homogeneous cyanogen dimer and the mixed diacetylene/cyanogen dimer. Six previously characterized stationary points on the diacetylene dimer PES were re-examined with the CCSD(T) method and the TZ2P(f,d)++ basis set for consistency. Second-order Møller-Plesset perturbation theory (MP2) and CCSD(T) complete basis set (CBS) limit interaction energies were estimated using the explicitly correlated MP2-F12 and CCSD(T)-F12 methods in conjunction with the VQZ-F12 basis set. On the cyanogen dimer PES, the C2v T-shaped structure is the only minimum, with an average electronic interaction energy, Eint, of -1.96 kcal mol(-1) at the CCSD(T) CBS limit. The Cs Y-shaped structure (in agreement with previous results) is the global minimum on the diacetylene dimer PES, having a mean CCSD(T) CBS limit Eint of -1.75 kcal mol(-1). Three low-lying minima have been identified on the diacetylene/cyanogen dimer PES, a C∞v linear, a C2v cross, and a Cs parallel-slipped structure with average CCSD(T) CBS limit interaction energies of -2.00, -2.16, and -2.45 kcal mol(-1), respectively.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of Heterogeneity in Small π-Type Dimers: Homogeneous and Mixed Dimers of Diacetylene and Cyanogen

Copeland

Tschumper

2012

J. Chem. Theory Comput.

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“…Subsequently the group of de Almeida examined T-shaped, linear, and parallel structures at the HF level of theory. 17 Important nonplanar structures (including some of those studied by Hasanein and Evans) were neglected entirely by de Almeida et al, and the work went on to conclude that the T-shaped structure was the global minimum on the dimer potential energy surface.…”

Section: Introductionmentioning

confidence: 99%

Reliable structures and energetics for two new delocalized π⋯π prototypes: cyanogen dimer and diacetylene dimer

Hopkins

ElSohly

Tschumper

2007

Phys. Chem. Chem. Phys.

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Two new prototype delocalized pi[dot dot dot]pi complexes are introduced: the dimers of cyanogen, (N[triple bond]C-C[triple bond]N)(2), and diacetylene, (HC[triple bond]C-C[triple bond]CH)(2). These dimers have properties similar to larger delocalized pi...pi systems such as benzene dimer but are small enough that they can be probed in far greater detail with high accuracy electronic structure methods. Parallel-slipped and T-shaped structures of both cyanogen dimer and diacetylene dimer have been optimized with 15 different procedures. The effects of basis set size, theoretical method, counterpoise correction, and the rigid monomer approximation on the structure and energetics of each dimer have been examined. MP2 and CCSD(T) optimized geometries for all four dimer structures are reported, as well as estimates of the CCSD(T) complete basis set (CBS) interaction energy for every optimized geometry. The data reported here suggest that future optimizations of delocalized pi[dot dot dot]pi clusters should be carried out with basis sets of triple-zeta quality. Larger basis sets and the expensive counterpoise correction to the molecular geometry are not necessary. The rigid monomer approximation has very little effect on structure and energetics of these dimers and may be used without consequence. Due to a consistent cancellation of errors, optimization with the MP2 method leads to CCSD(T)/CBS interaction energies that are within 0.2 kcal mol(-1) of those for structures optimized with the CCSD(T) method. Future studies that aim to resolve structures separated by a few tenths of a kcal mol(-1) should consider the effects of optimization with the CCSD(T) method.

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“…Moreover, great advances in experimental techniques and theoretical methods have been verified, [3][4][5][6][7] and also ab initio calculations on the molecular structure and energetics of weakly bound complexes have been successfully conducted. [8][9][10][11] Many of the experimental works have shown that some van der Waals molecules exhibit hindered rotation motions which often have unexpected line intensities. [12][13][14][15][16] The experimental advances in the spectroscopy of van der Waals complexes have been matched by theoretical works, and some models have been developed 14,[17][18][19] for the study of the phenomenon of internal rotation in van der Waals complexes and its influence in the vibro-rotational spectrum of these molecular species.…”

Section: Introductionmentioning

confidence: 99%

Ab initio investigation of internal rotation in the ethylene–sulfur dioxide dimer

Resende

Almeida

1995

The Journal of Chemical Physics

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The phenomenon of tunneling motion in the C2H4...SO2 dimer has been studied in the ab initio Hartree–Fock (HF) and Mo/ller–Plesset second-order perturbation theory (MP2) levels, employing the DZP basis set. Basis set superposition errors (BSSE) were accounted for using the counterpoise correction method. A simple model for treating the problem in one dimension was utilized, where coupling of intramolecular vibration and dimer internal rotation have been neglected. A comparative study between two potentials was carried out. The first potential is based on pointwise ab initio calculations of the intermolecular potential energy surface (PES) including BSSE correction, and the second is based on the expression VN=V0 [1−cos(Nα)]/2, where V0 was obtained from the ab initio fully optimized equilibrium and transition state structures. The resultant Hamiltonian was solved using the variational method, and the calculated splitting of transition frequencies compared with experimental data.

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The molecular structure of the (NCCN)₂and (PCCP)₂van der Waals dimers

Cited by 11 publications

References 53 publications

Effects of Heterogeneity in Small π-Type Dimers: Homogeneous and Mixed Dimers of Diacetylene and Cyanogen

Effects of Heterogeneity in Small π-Type Dimers: Homogeneous and Mixed Dimers of Diacetylene and Cyanogen

Reliable structures and energetics for two new delocalized π⋯π prototypes: cyanogen dimer and diacetylene dimer

Ab initio investigation of internal rotation in the ethylene–sulfur dioxide dimer

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The molecular structure of the (NCCN)2and (PCCP)2van der Waals dimers

Cited by 11 publications

References 53 publications

Effects of Heterogeneity in Small π-Type Dimers: Homogeneous and Mixed Dimers of Diacetylene and Cyanogen

Effects of Heterogeneity in Small π-Type Dimers: Homogeneous and Mixed Dimers of Diacetylene and Cyanogen

Reliable structures and energetics for two new delocalized π⋯π prototypes: cyanogen dimer and diacetylene dimer

Ab initio investigation of internal rotation in the ethylene–sulfur dioxide dimer

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The molecular structure of the (NCCN)₂and (PCCP)₂van der Waals dimers