Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
Browse
4 results
Search Results
Article Citation - Scopus: 30Thermochemistry of Alkali Metal Cation Interactions With Histidine: Influence of the Side Chain(2012-11-26) Armentrout, Peter B.; Citir, Murat; Chen, Yu; Rodgers, Mary T.The interactions of alkali metal cations (M+ = Na+, K+, Rb+, Cs+) with the amino acid histidine (His) are examined in detail. Experimentally, bond energies are determined using threshold collision-induced dissociation of the M+(His) complexes with xenon in a guided ion beam tandem mass spectrometer. Analyses of the energy dependent cross sections provide 0 K bond energies of 2.31 ± 0.11, 1.70 ± 0.08, 1.42 ± 0.06, and 1.22 ± 0.06 eV for complexes of His with Na+, K+, Rb+, and Cs+, respectively. All bond dissociation energy (BDE) determinations include consideration of unimolecular decay rates, internal energy of reactant ions, and multiple ion-neutral collisions. These experimental results are compared to values obtained from quantum chemical calculations conducted previously at the MP2(full)/6-311+G(2d,2p), B3LYP/6-311+G(2d,2p), and B3P86/6-311+G(2d,2p) levels with geometries and zero point energies calculated at the B3LYP/6-311+G(d,p) level where Rb and Cs use the Hay-Wadt effective core potential and basis set augmented with additional polarization functions (HW*). Additional calculations using the def2-TZVPPD basis set with B3LYP geometries were conducted here at all three levels of theory. Either basis set yields similar results for Na+(His) and K+(His), which are in reasonable agreement with the experimental BDEs. For Rb+(His) and Cs +(His), the HW* basis set and ECP underestimate the experimental BDEs, whereas the def2-TZVPPD basis set yields results in good agreement. The effect of the imidazole side chain on the BDEs is examined by comparing the present results with previous thermochemistry for other amino acids. Both polarizability and the local dipole moment of the side chain are influential in the energetics. © 2012 American Chemical Society. © 2013 Elsevier B.V., All rights reserved.; MEDLINE® is the source for the MeSH terms of this document.Article Citation - WoS: 1Citation - Scopus: 1Highly Efficient Chlorinated Solvent Uptake by Novel Covalent Organic Networks via Thiol-Ene Chemistry(Springer, 2021-07-03) Yavuz, Mustafa Selman; Citir, MuratIn this study, we synthesized an aliphatic-aromatic regular network as a novel covalent organic networks called TEPN-1 (Thiol-ene Polymer Network) and TEPN-2 via thiol-ene chemistry. TEPN-1 and TEPN-2 were analyzed by FTIR, C-13-NMR, Brunauer-Emmett-Teller, thermogravimetric analysis and elemental analysis. Solvent uptake capacity of TEPN-1 and TEPN-2 was employed against 26 solvents which are frequently used in chemical industry. It is found that TEPN-1 has the highest swelling adsorption ratio with chloroform and DCM (13.7 and 11.5 g.g(-1), respectively), while TEPN-2 has 9.2 and 7.5 g.g(-1), respectively. Both TEPN-1 and TEPN-2 have very minimal water uptake (0.165 and 0.189 g.g(-1), respectively). TEPN-1 and TEPN-2 are efficient adsorbents for most of organic solvents including water-miscible organic solvents such as THF, dioxane and pyridine.Article Citation - WoS: 58Citation - Scopus: 59Bond Energies of ThO+ and ThC+: A Guided Ion Beam and Quantum Chemical Investigation of the Reactions of Thorium Cation With O2 and CO(AIP Publishing, 2016-05-13) Cox, Richard M.; Citir, Murat; Armentrout, P. B.; Battey, Samuel R.; Peterson, Kirk A.Kinetic energy dependent reactions of Th+ with O-2 and CO are studied using a guided ion beam tandem mass spectrometer. The formation of ThO+ in the reaction of Th+ with O-2 is observed to be exothermic and barrierless with a reaction efficiency at low energies of k/k(LGS) = 1.21 +/- 0.24 similar to the efficiency observed in ion cyclotron resonance experiments. Formation of ThO+ and ThC+ in the reaction of Th+ with CO is endothermic in both cases. The kinetic energy dependent cross sections for formation of these product ions were evaluated to determine 0 K bond dissociation energies (BDEs) of D-0(Th+-O) = 8.57 +/- 0.14 eV and D-0(Th+-C) = 4.82 +/- 0.29 eV. The present value of D-0(Th+-O) is within experimental uncertainty of previously reported experimental values, whereas this is the first report of D-0(Th+-C). Both BDEs are observed to be larger than those of their transition metal congeners, TiL+, ZrL+, and HfL+ (L = O and C), believed to be a result of lanthanide contraction. Additionally, the reactions were explored by quantum chemical calculations, including a full Feller-Peterson-Dixon composite approach with correlation contributions up to coupled-cluster singles and doubles with iterative triples and quadruples (CCSDTQ) for ThC, ThC+, ThO, and ThO+, as well as more approximate CCSD with perturbative (triples) [CCSD(T)] calculations where a semi-empirical model was used to estimate spin-orbit energy contributions. Finally, the ThO+ BDE is compared to other actinide (An) oxide cation BDEs and a simple model utilizing An(+) promotion energies to the reactive state is used to estimate AnO(+) and AnC(+) BDEs. For AnO(+), this model yields predictions that are typically within experimental uncertainty and performs better than density functional theory calculations presented previously. Published by AIP Publishing.Article Citation - Scopus: 50Activation of Methane by Os+: Guided-Ion and Theoretical Studies(2013-08-19) Armentrout, Peter B.; Parke, Laura G.; Hinton, Christopher S.; Citir, MuratActivation of methane by the third-row transition-metal cation Os + is studied experimentally by examining the kinetic energy dependence of reactions of Os+ with CH<inf>4</inf> and CD<inf>4</inf> using guided-ion-beam tandem mass spectrometry. A flow tube ion source produces Os+ in its electronic ground state and primarily in the ground spin-orbit level. Dehydrogenation to form [Os,C,2 H]++H<inf>2</inf> is exothermic, efficient, and the only process observed at low energies for reaction of Os+ with methane, whereas OsH+ dominates the product spectrum at higher energies. The kinetic energy dependences of the cross sections for several endothermic reactions are analyzed to give 0K bond dissociation energies (in eV) of D<inf>0</inf>(Os+-C)=6.20±0. 21, D<inf>0</inf>(Os+-CH)=6.77±0.15, and D<inf>0</inf>(Os +-CH<inf>3</inf>)=3.00±0.17. Because it is formed exothermically, D<inf>0</inf>(Os+-CH<inf>2</inf>) must be greater than 4.71eV, and a speculative interpretation suggests the exothermicity exceeds 0.6eV. Quantum chemical calculations at the B3LYP/def2-TZVPP level show reasonable agreement with the experimental bond energies and with previous theoretical values available. Theory also provides the electronic structures of the product species as well as intermediates and transition states along the reactive potential energy surfaces. Notably, the structure of the dehydrogenation product is predicted to be HOsCH+, rather than OsCH<inf>2</inf>+, in contrast to previous work. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. © 2013 Elsevier B.V., All rights reserved.