Density functional estimation of hydride and proton affinities of substituted allenes and heteroallenes

2021 ◽  
Author(s):  
Hamid Saeidian ◽  
Hadi Malekian ◽  
Esmail Vessally
Keyword(s):  
Density Functional ◽  
Proton Affinities ◽  
Functional Estimation

scholarly journals Protonated heterocyclic derivatives of cyclopropane and cyclopropanone: classical species, alternate sites, and ring fragmentation

2015 ◽  
Vol 93 (7) ◽  
pp. 708-714 ◽  
Author(s):  
Margarida S. Miranda ◽  
Darío J.R. Duarte ◽  
Joaquim C.G. Esteves da Silva ◽  
Joel F. Liebman
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Density Functional ◽  
Computational Study ◽  
Basis Set ◽  
Proton Affinities ◽  
Functional Theory ◽  
Heterocyclic Derivatives ◽  
Gas Phase Basicities ◽  
Derivatives Of

A computational study has been performed for protonated oxygen- or nitrogen-containing heterocyclic derivatives of cyclopropane and cyclopropanone. We have searched for the most stable conformations of the protonated species using density functional theory with the B3LYP functional and the 6-31G(2df,p) basis set. More accurate enthalpy values were obtained from G4 calculations. Proton affinities and gas-phase basicities were accordingly derived.

scholarly journals DFT and ab initio calculations of ionization potentials, proton affinities and bond dissociation enthalpies of aromatic compounds

2019 ◽  
Vol 12 (2) ◽  
pp. 225-240
Author(s):  
Denisa Cagardová ◽  
Martin Michalík ◽  
Erik Klein ◽  
Vladimír Lukeš ◽  
Zoran Marković
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Radical Scavenging ◽  
Radical Cations ◽  
Ionization Potentials ◽  
Phase Reaction ◽  
Proton Affinities ◽  
Functional Theory ◽  
Bond Dissociation ◽  
Nitro Derivatives

Abstract Theoretical study of phenol, thiophenol, benzeneselenol, aniline and their para-amino and paranitro derivatives is presented. Neutral molecules, their deprotonated forms, neutral radicals, and radical cations were studied using three Density Functional Theory (DFT) functionals as well as combined DFT and ab initio G4 method in order to calculate the N—H, O—H, S—H, and Se—H bond dissociation enthalpies (BDE), proton affinities of corresponding anions (PA) and ionization potentials (IP) of studied compounds. These quantities represent fundamental reaction enthalpies related to the radical scavenging action of primary antioxidants. Calculated values were compared with available experimental data to assess applicability of the computational approaches employed. M06-2X/6-311++G(d,p) and G4 methods showed the best agreement with the available experimental gas-phase reaction enthalpies.

The Utility of Calculated Proton Affinities in Drug Design: A DFT Study

2018 ◽  
Vol 71 (8) ◽  
pp. 580 ◽  
Author(s):  
Daniel Moscoh Ayine-Tora ◽  
Jóhannes Reynisson
Keyword(s):  
Drug Design ◽  
Density Functional ◽  
Water Solubility ◽  
Pharmacokinetic Profile ◽  
Acid Dissociation ◽  
Acid Dissociation Constant ◽  
Proton Affinities ◽  
Pka Values ◽  
Drug Candidates ◽  
Linear Relationships

Computer-aided drug design comprises several predictive tools, which can calculate various properties of the candidates under development. Proton affinity (PA) is related to pKa (the negative log of the acid dissociation constant (Ka)) one of the fundamental physical properties of drug candidates, determining their water solubility and thus their pharmacokinetic profile. The following questions therefore emerged: to what extent are PA predictions useful in drug design, and can they be reliably used to derive pKa values? Using density functional theory (DFT), it was established that for violuric acid, with three ionisation groups, the PAs correlate well with the measured pKas (R2 = 0.990). Furthermore, an excellent correlation within the amiloride compound family was achieved (R2 = 0.922). In order to obtain correlations for larger compound collections (n = 210), division into chemical families was necessary: carboxylic acids (R2 = 0.665), phenols (R2 = 0.871), and nitrogen-containing molecules (R2 = 0.742). These linear relationships were used to predict pKa values of 90 drug molecules with known pKas. A total of 48 % of the calculated values were within 1 logarithmic unit of the experimental number, but mainstream empirically based methods easily outperform this approach. The conclusion can therefore be reached that PA values cannot be reliably used for predicting pKa values globally but are useful within chemical families and in the event where a specific tautomer of a drug needs to be identified.

Triazene proton affinities: A comparison between density functional, Hartree-Fock, and post-Hartree-Fock methods

1994 ◽  
Vol 15 (8) ◽  
pp. 875-892 ◽  
Author(s):  
Ann M. Schmiedekamp ◽  
Igor A. Topol ◽  
Stanley K. Burt ◽  
Holy Razafinjanahary ◽  
Henry Chermette ◽  
...  
Keyword(s):  
Density Functional ◽  
Proton Affinities ◽  
Hartree Fock

Gas-phase spectroscopic characterization of neutral and ionic polycyclic aromatic phosphorus heterocycles (PAPHs)

2020 ◽  
Vol 500 (2) ◽  
pp. 2564-2576
Author(s):  
Ricardo R Oliveira ◽  
Germán Molpeceres ◽  
Felipe Fantuzzi ◽  
Heidy M Quitián-Lara ◽  
Heloisa M Boechat-Roberty ◽  
...  
Keyword(s):  
Ir Spectra ◽  
Density Functional ◽  
Dipole Moments ◽  
Closed Shell ◽  
Spectroscopic Characterization ◽  
Infrared Emission ◽  
Proton Affinities ◽  
Anionic Species ◽  
Polycyclic Aromatic ◽  
Phosphorus Heterocycles

ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) constitute an essential family of compounds in interstellar (ISM) and circumstellar (CSM) media. Recently, formation routes for the corresponding polycyclic aromatic phosphorus heterocycles (PAPHs) in astrophysical environments have been proposed. In order to contribute to a better understanding of the phosphorus chemistry in the ISM, infrared (IR) spectra and selected properties of PAPHs were computed at the density functional theory level for neutral, cationic, and anionic species. Our results reveal that several protonated PAPHs do not have planar backbones, and all species have permanent dipole moments between 2D and 4D. Closed-shell PAPHs have similar ionization potentials compared to the parent PAHs, below the Lyman threshold limit. In addition, all PAPHs show positive electron affinities higher than those of PAHs. Protonation preferably occurs on the heteroatom but with lower proton affinities than those of the corresponding nitrogen analogues (polycyclic aromatic nitrogen heterocycles). In general, neutral species have similar IR spectra profile with the most intense bands around 800 cm−1 (12.5 μm) related to C−H wagging. Charge and protonation affect the IR spectra mainly by decreasing the intensities of these modes and increasing the ones between 1000 (10.0 μm) and 1800 cm−1 (5.6 μm). The P−H stretching appears in a different spectral region, between 2300 (4.3 μm) and 2700 cm−1 (3.7 μm). Our results are discussed in the context of distinct sources where PAHs and phosphorus are detected. PAPHs, in particular the coronene derivatives, can contribute to the unidentified infrared emission band at 6.2 μm.

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