Accurate Infrared (IR) Spectra for Molecules Containing the C≡N Moiety by Anharmonic Computations with the Double Hybrid B2PLYP Density Functional

Vazart, Fanny; Latouche, Camille; Cimino, Paola; Barone, Vincenzo

doi:10.1021/acs.jctc.5b00638

Cited by 18 publications

(23 citation statements)

References 48 publications

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“…For example, a hybrid approach combining higher-level harmonic computations augmenting DVPT2/GVPT2 anharmonic analysis could be used. Barone and co-workers have reported evidences of accurate and affordable hybrid B3LYP(harmonic)/B2PLYP(anharmonic) computations [51,52], as also seen in our previous studies [53].…”

Section: Resultssupporting

confidence: 81%

Distinct Difference in Sensitivity of NIR vs. IR Bands of Melamine to Inter-Molecular Interactions with Impact on Analytical Spectroscopy Explained by Anharmonic Quantum Mechanical Study

et al. 2019

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Melamine (IUPAC: 1,3,5-Triazine-2,4,6-triamine) attracts high attention in analytical vibrational spectroscopy due to its misuse as a food adulterant. Vibrational spectroscopy [infrared (IR) and Raman and near-infrared (NIR) spectroscopy] is a major quality control tool in the detection and quantification of melamine content. The physical background for the measured spectra is not interpreted in analytical spectroscopy using chemometrics. In contrast, quantum mechanical calculations are capable of providing deep and independent insights therein. So far, the NIR region of crystalline melamine has not been studied by quantum mechanical calculations, while the investigations of its IR spectra have remained limited. In the present work, we employed fully anharmonic calculation of the NIR spectrum of melamine based on finite models, and also performed IR spectral simulation by using an infinite crystal model—periodic in three dimensions. This yielded detailed and unambiguous NIR band assignments and revised the previously known IR band assignments. We found that the out-of-plane fundamental transitions, which are essential in the IR region, are markedly more sensitive to out-of-plane inter-molecular interactions of melamine than NIR transitions. Proper description of the chemical surrounding of the molecule of melamine is more important than the anharmonicity of its vibrations. In contrast, the NIR bands mostly arise from in-plane vibrations, and remain surprisingly insensitive to the chemical environment. These findings explain previous observations that were reported in IR and NIR analytical studies of melamine.

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Section: Resultssupporting

confidence: 81%

Distinct Difference in Sensitivity of NIR vs. IR Bands of Melamine to Inter-Molecular Interactions with Impact on Analytical Spectroscopy Explained by Anharmonic Quantum Mechanical Study

et al. 2019

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“…While they are not sufficient for a truly quantitative picture of the reaction energetics, they give further confidence in the reliability of the geometric parameters and harmonic frequencies obtained at this level. 67 In agreement with previous studies, 68 the results delivered by the widely employed CBS-QB3 model 61 are quite disappointing. Indeed, for some species (FC01, R12′, TS 2−3 , P9), it shows discrepancies larger than 10 kJ mol −1 with respect to the cheap values, which, as discussed in the previous section, are close to very accurate benchmark values (see Table 1).…”

Section: Chsupporting

confidence: 78%

Exploring the Maze of C₂N₂H₅ Radicals and Their Fragments in the Interstellar Medium with the Help of Quantum-Chemical Computations

Salta

Tasinato

Lupi

et al. 2020

ACS Earth Space Chem.

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Among the species discovered in the interstellar medium and planetary atmospheres, a crucial role is played by the so-called “interstellar” complex organic molecules (iCOMs) because they are the signature of the increasing molecular complexity in space. Indeed, they may represent the connection between simple molecules and biochemical species like amino acids and nucleobases. In particular, HCN and the related CN radical are the starting points of rich nitrile chemistry. In this framework, we have undertaken a computational investigation of the gas-phase reaction mechanisms involving different C2N2H5 radicals and their fragments, stemming from the addition of the cyano radical to the nitrogen atom of methylamine. Aiming at exploiting an accurate yet cost-effective protocol, a combination of CCSD(T)-based composite schemes and density functional theory has been employed. The exploration of the plausible chemical reaction channels has led to the identification of 12 different products, as well as 28 transition states connecting reactants, intermediates, and products. Aminoacetonitrile (H2NCH2CN), proposed as an intermediate in the formation of the smallest amino acid glycine, and the CH2NH2 radical appear as products energetically accessible under astrophysical conditions.

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“…Moreover, the B3LYP-D363,64 computations led to remarkable improvements on the accuracy of structural parameters and binding energies for systems involving both stacking interactions and hydrogen bonds, providing at the same time accurate anharmonic frequencies 32,33,46,62,71–73. However, some larger discrepancies with respect to experiment are still observed for the X-H and C=X (X=O, N) stretching frequencies32,61, which can be systematically amended by hybrid computations46,74,75 with harmonic frequencies corrected at higher-level of theory (Coupled Cluster (CC) or B2PLYP) with basis sets of at least triple- ζ quality17,46,59. The B2PLYP/B3LYP-D3 model has been applied for uracil-water complexes and hydrogen-bonded uracil dimers35.…”

Section: Introductionmentioning

confidence: 99%

Reliable vibrational wavenumbers for CO and N–H stretchings of isolated and hydrogen-bonded nucleic acid bases

Fornaro

Biczysko

Bloino

et al. 2016

Phys. Chem. Chem. Phys.

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The accurate prediction of vibrational wavenumbers for functional groups involved in hydrogen-bonded bridges remains an important challenge for computational spectroscopy. For the specific case of the C=O and N-H stretching modes of nucleobases and their oligomers, the paucity of experimental reference values needs to be compensated by reliable computational data, which require the use of approaches going beyond the standard harmonic oscillator model. Test computations performed for model systems (formamide, acetamide and their cyclic homodimers) in the framework of the second order vibrational perturbation theory (VPT2) confirmed that anharmonic corrections can be safely computed by global hybrid (GHF) or double hybrid (DHF) functionals, whereas the harmonic part is particularly challenging. As a matter of fact, GHFs perform quite poorly and even DHFs, while fully satisfactory for C=O stretchings, face unexpected difficulties when dealing with N-H stretchings. On these grounds, a linear regression for N-H stretchings has been obtained and validated for the heterodimers formed by 4-aminopyrimidine with 6-methyl-4-pyrimidinone (4APM-M4PMN) and by uracil with water. In view of the good performance of this computational model, we have built a training set of B2PLYP-D3/maug-cc-pVTZ harmonic wavenumbers (including linear regression scaling for N-H) for six-different uracil dimers and a validation set including 4APM-M4PMN, one of the most stable hydrogen-bonded adenine homodimers, as well as the adenine-uracil, adenine-thymine, guanine-cytosine and adenine-4-thiouracil heterodimers. Because of the unfavourable scaling of DHF harmonic wavenumbers with the dimensions of the investigated systems, we have optimized a linear regression of B3LYP-D3/N07D harmonic wavenumbers for the training set, which has been next checked against the validation set. This relatively cheap model, which shows very good agreement with experimental data (average errors of about 10 cm(-1)), paves the route toward a reliable analysis of spectroscopic signatures for larger polynucleotides.

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Accurate Infrared (IR) Spectra for Molecules Containing the C≡N Moiety by Anharmonic Computations with the Double Hybrid B2PLYP Density Functional

Cited by 18 publications

References 48 publications

Distinct Difference in Sensitivity of NIR vs. IR Bands of Melamine to Inter-Molecular Interactions with Impact on Analytical Spectroscopy Explained by Anharmonic Quantum Mechanical Study

Distinct Difference in Sensitivity of NIR vs. IR Bands of Melamine to Inter-Molecular Interactions with Impact on Analytical Spectroscopy Explained by Anharmonic Quantum Mechanical Study

Exploring the Maze of C₂N₂H₅ Radicals and Their Fragments in the Interstellar Medium with the Help of Quantum-Chemical Computations

Reliable vibrational wavenumbers for CO and N–H stretchings of isolated and hydrogen-bonded nucleic acid bases

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Accurate Infrared (IR) Spectra for Molecules Containing the C≡N Moiety by Anharmonic Computations with the Double Hybrid B2PLYP Density Functional

Cited by 18 publications

References 48 publications

Distinct Difference in Sensitivity of NIR vs. IR Bands of Melamine to Inter-Molecular Interactions with Impact on Analytical Spectroscopy Explained by Anharmonic Quantum Mechanical Study

Distinct Difference in Sensitivity of NIR vs. IR Bands of Melamine to Inter-Molecular Interactions with Impact on Analytical Spectroscopy Explained by Anharmonic Quantum Mechanical Study

Exploring the Maze of C2N2H5 Radicals and Their Fragments in the Interstellar Medium with the Help of Quantum-Chemical Computations

Reliable vibrational wavenumbers for CO and N–H stretchings of isolated and hydrogen-bonded nucleic acid bases

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Exploring the Maze of C₂N₂H₅ Radicals and Their Fragments in the Interstellar Medium with the Help of Quantum-Chemical Computations