• Younes Valadbeigi

      Articles written in Journal of Chemical Sciences

    • G4MP2, DFT and CBS-Q calculation of proton and electron affinities, gas phase basicities and ionization energies of hydroxylamines and alkanolamines

      Younes Valadbeigi Hossein Farrokhpour Mahmoud Tabrizchi

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      The proton affinities, gas phase basicities and adiabatic ionization energies and electron affinities of some important hydroxylamines and alkanolamines were calculated using B3LYP, CBS-Q and G4MP2 methods. Also, the B3LYP method was used to calculate vertical ionization energies and electron affinities of the molecules. The calculated ionization energies are in the range of 8-10.5 eV and they decrease as the number of carbon atoms increases. Computational results and ion mobility spectrometry study confirm that some alkanolamines lose a water molecule due to protonation at oxygen site and form cationic cyclic compounds. Effect of different substitutions on the cyclization of ethanolamine was studied theoretically.

    • Adsorption of small gas molecules on B36 nanocluster

      Younes Valadbeigi Hossein Farrokhpour Mahmoud Tabrizchi

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      Adsorption of CO, N2, H2O, O2, H2 and NO molecules on B36 cluster was studied using density functional theory (DFT) with B3LYP functional and 6-311+G(d,p) basis set. Energies, enthalpies and Gibbs free energies of the adsorption processes were calculated. The thermodynamic data showed that the B36 cluster is a good adsorbent only for CO, O2 and NO molecules. The calculated energies of adsorption of N2, H2 O and H2 on the B36 cluster were positive values. CO molecule is adsorbed via the carbon atom more effectively, while the nitrogen atom of NO is adsorbed better than the oxygen atom. Also, when NO and O2 are adsorbed synchronously via both atoms, they dissociate. The edge boron atoms of the B36 cluster showed more reactivity than the inner atoms.

    • Effect of Mono- and Di-hydration on the Intramolecular Proton Transfers and Stability of Cyanuric Acid Isomers: A DFT Study

      YOUNES VALADBEIGI

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      Structural and thermodynamic properties of 10 isomers of cyanuric acid were studied in aqueous and gas phases, employing B3LYP/6-311++G(d,p) method. The aromaticities of these isomers were evaluated using nucleus-independent chemical shift (NICS) index. The calculations showed that as the number of the ketogroups increases the stability of the isomers increases and the aromaticity decreases. Mono- and di-hydrations of the isomers did not change the stability trend, so that the tri-keto isomer was the most stable isomer amongthe hydrated and non-hydrated isomers. The activation energies (Ea) of the intramolecular proton transfers (tautomerisms) and energy barriers of H-rotations around its C-O axis in enolic isomers were calculated. The energy barriers were smaller than 45 kJ/mol for the H-rotations while the Ea values of the proton transfers were in the range of 130-210 kJ/mol. Effect of micro-hydrations on the transition state structures and the energy barriers of the tautomerisms were investigated. The mono- and di-hydrations lower the activation energies to100-130 kJ/mol and 110-145 kJ/mol, respectively.

    • Adsorption of neutral and protonated Lewis bases on Na8-nanocluster: basicity enhancement of the Lewis bases

      AZIN AZADSARV YOUNES VALADBEIGI

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      Abstract. Structural and energetic properties of Nan (n=1–8) nanoclusters were studied employing the B3LYP method and using 6-31+(d,p) basis set. Comparison of the calculated binding energies per atom (Eb) of the cluster shows that the Na8 cluster with D2d symmetry group is the most stable structure among the Nan clusters. Adsorption of neutral and protonated forms of ammonia, methylamine, ethylamine, hydrazine, guanidine, pyridine, methanolamine, and methanimine on Na8 cluster was studied. Interaction of the neutral Lewis bases with Na8 was very weak such that the interaction energies were smaller than − 50 kJ mol-1 However, the protonated bases interact with Na8 more strongly with interaction energies generally in the range of − 90 to −350 kJ mol-1. The protonated forms of methanolamine undergo dissociative adsorption on Na8 with adsorption energies of about − 800 kJ mol-1. Since the protonated bases are stabilized more than the corresponding neutral ones upon adsorption on Na8 cluster, the basicity of the Lewis bases enhances in the presence of Na8. The calculated proton affinities of the isolated Lewis bases were smaller than 990 kJ mol -1 while in the presence of the Na8 cluster, the basicity increases so that the calculated proton affinities were higher than 1000 kJ mol -1.

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