Thermochemical Studies on Double- and Triple-layered [2.2]Paracyclophanes. Estimation of Molecular Strain Energies.

Nishiyama, Keiichi; Sakiyama, Ninoru; Seki, Syûzô; Horita, Hisanori; Otsubo, Tetsuo; Misumi, Soichi

doi:10.1246/bcsj.53.869

Cited by 25 publications

(9 citation statements)

References 28 publications

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“…Second, only small organic and inorganic molecules for which accurate formation enthalpies are known have been used to equilibrate the reactions (i.e., were used as A, B, and D in eq ), in particular acetylene, ethylene, ethane, CO, methane, H 2 , H 2 O, H 2 S, HCN, N 2 , and NH 3 . We expect under these conditions that the possible cancellations of errors are minimal, and better insights into the ability of the electronic structure theory methods to provide accurate reaction enthalpies can be gained. …”

Section: Computational Detailsmentioning

confidence: 99%

Heats of Formation of Medium-Sized Organic Compounds from Contemporary Electronic Structure Methods

Minenkov

Wang

et al. 2017

J. Chem. Theory Comput.

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Computational electronic structure calculations are routinely undertaken to predict thermodynamic properties of various species. However, the application of highly accurate wave function theory methods, such as the "gold standard" coupled cluster approach including single, double, and partly triple excitations in perturbative fashion, CCSD(T), to large molecules is limited due to high computational cost. In this work, the promising domain based local pair natural orbital coupled cluster approach, DLPNO-CCSD(T), has been tested to reproduce 113 accurate formation enthalpies of medium-sized molecules (few dozens heavy atoms) important for bio- and combustion chemistry via the reaction based Feller-Peterson-Dixon approach. For comparison, eight density functional theory (B3LYP, B3LYP-D3, PBE0, PBE0-D3, M06, M06-2X, ωB97X-D3, and ωB97M-V) and MP2-based (B2PLYP-D3, PWPB95-D3, B2T-PLYP, B2T-PLYP-D, B2GP-PLYP, DSD-PBEP86-D3, SCS-MP2, and OO-SCS-MP2) methods have been tested. The worst performance has been obtained for the standard hybrid DFT functionals, PBE0 (mean unsigned error (MUE)/mean signed error (MSE) = 9.1/6.0 kcal/mol) and B3LYP (MUE/MSE = 13.5/-13.3 kcal/mol). The influence of an empirical dispersion correction term on these functionals' performance is not homogeneous: B3LYP performance is improved (B3LYP-D3 (MUE/MSE = 6.0/0.8 kcal/mol)); meanwhile PBE0 performance is worse (PBE0-D3 (MUE/MSE = 14.1/13.6 kcal/mol)). The Minnesota functionals, M06 (MUE/MSE = 3.8/-2.0 kcal/mol) and M06-2X (MUE/MSE = 3.5/3.0 kcal/mol), and recently developed ωB97X-D3 (MUE/MSE = 3.2/0.2 kcal/mol) and ωB97M-V (MUE/MSE = 2.2/1.3 kcal/mol) methods provided significantly better formation enthalpies. Enthalpies of similar quality can also be obtained from some double hybrid methods (B2PLYP-D3 (MUE/MSE = 4.7/2.0 kcal/mol), PWPB95-D3 (MUE/MSE = 4.3/3.2 kcal/mol), B2T-PLYP (MUE/MSE = 4.1/-3.0 kcal/mol), and B2T-PLYP-D (MUE/MSE = 3.3/1.7 kcal/mol)). The two spin component scaled (SCS) MP2 methods resulted in even smaller errors (SCS-MP2 (MUE/MSE = 1.9/1.2 kcal/mol) and OO-SCS-MP2 (MUE/MSE = 1.6/0.1 kcal/mol)). The best performance was found for the frozen core (FC) DLPNO-CCSD(T) method with a MUE/MSE of 1.6/-1.2 kcal/mol. The performance of the DLPNO-CCSD(T) method can be further improved by running the post-SCF calculations on the B3LYP orbitals: the MUE/MSE for the DLPNO-CCSD(T,B3LYP) approximation is 1.2/-0.4 kcal/mol. We recommend the DLPNO-CCSD(T,B3LYP) method for black box applications in thermodynamics of medium-sized organic molecules when the canonical CCSD(T) calculations with basis sets of reasonable quality are prohibitively expensive.

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Section: Computational Detailsmentioning

confidence: 99%

Heats of Formation of Medium-Sized Organic Compounds from Contemporary Electronic Structure Methods

Minenkov

Wang

et al. 2017

J. Chem. Theory Comput.

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“…The experimental activation barrier for the opening of [2.2]-p-cyclophane ring was measured as 37.7 ( 0.5 kcal/mol, and the barrier for the reverse reaction was 11.8 ( 1.0 kcal/mol. Together with the experimental heat of formation of [2.2]-p-cyclophane equal 58.5 ( 0.5 kcal/mol 26 or more commonly known value 59.9 ( 1.9 kcal/mol, 27 this allows estimation of the heat of formation of the biradical dimer as 84.4 or 85.8 kcal/mol. The experimental heat of formation for p-xylylene is 50 ( 4 kcal/mol, 28 so the heat of formation for two monomers is around 15 kcal/mol higher than the heat of formation for the biradical dimer.…”

Section: Introductionmentioning

confidence: 97%

Theoretical Study of Polymerization Mechanism of p-Xylylene Based Polymers

et al. 2010

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The mechanism of polymerization of p-xylylene and its derivatives is analyzed at the theoretical level. The polymerization reaction takes place in vacuo without any catalyst. The first step is a pyrolytic decomposition of starting material for polymerization, p-cyclophane, a cyclic dimer of p-xylylene, into biradical linear dimer and finally into two quinonoid monomeric molecules of p-xylylene. The quinonoid monomer is diamagnetic; i.e., it has a singlet ground state. The monomers after pyrolysis, when the temperature is lowered, do not re-form cyclic dimers but instead polymerize into long chain molecules. The initiation of polymerization requires dimerization of two monomers leading to formation of a genuine noncoupled biradical dimer. The chain molecules grow through the propagation reaction only one unit at a time, by the attachment of a monomer to a radical chain end. In this work the pyrolysis reaction, the initiation reaction and the first propagation steps of parylene polymerization (up to pentamer) are studied in details using different quantum chemical methods: AM1 and PM6 semiempirical methods and density functional theory (DFT) approach using B3LYP functional with two basis sets of different size (SVP and TZVP).

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“…The dissociation energy of the CH 2 −CH 3 bond cleavage in ethylbenzene (328.8 kJ mol -1 ) was used. The strain energies (kJ mol -1 ) of the CPs were taken from the literature: 2PCP (122.6), 2MCP (49.8), and 2MPCP (97.9) . The strain energy of methyl-substituted 2PCPs was assumed to be the same as that of 2PCP.…”

Section: Discussionmentioning

confidence: 99%

Xylylene Formation from Vibrationally Hot Cyclophanes: Specific Dissociation Rate Constants of Strained Molecules

et al. 2002

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Cyclophane derivatives were irradiated with an ArF excimer laser in the gas phase. No triplet states, fluorescence, or cation radicals were observed in the transient spectra. The CH2−CH2 bonds dissociated, forming corresponding xylylenes by a two-photon process. The bond dissociations were explained in terms of a multiphoton reaction of hot molecules formed by an internal conversion. In addition, a slow rise of xylylene that originated in the single photon dissociation process of hot cyclophane was observed in the case of methyl-substituted paracyclophanes under low pressure conditions. The specific reaction rates of the dissociations of highly strained paracyclophanes were well explained by a statistical reaction theory, if a simple consideration of strain energy was made in the calculations.

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Thermochemical Studies on Double- and Triple-layered [2.2]Paracyclophanes. Estimation of Molecular Strain Energies.

Cited by 25 publications

References 28 publications

Heats of Formation of Medium-Sized Organic Compounds from Contemporary Electronic Structure Methods

Heats of Formation of Medium-Sized Organic Compounds from Contemporary Electronic Structure Methods

Theoretical Study of Polymerization Mechanism of p-Xylylene Based Polymers

Xylylene Formation from Vibrationally Hot Cyclophanes: Specific Dissociation Rate Constants of Strained Molecules

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