Test-particle model potentials for hydrogen-bonded complexes: Complexes formed from HCN, HF, H2O, NH3, HCONH2, HCONHCH3, guanine and cytosine

Sagarik, Kritsana; Pongpituk, Vilaval; Chaiyapongs, Supaporn; Sisot, Phittaya

doi:10.1016/0301-0104(91)89012-y

Cited by 24 publications

(9 citation statements)

References 43 publications

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“…Three basic steps that were applied successfully in our previous investigations were used in this work: (1) searching for the intermediate complexes in the proton transfer pathway using the Test‐particle model (T‐model) potentials; (2) refining the T‐model‐optimized structures using an accurate quantum chemical method; and (3) performing BOMD simulations on the candidate intermediate complexes using the refined structures as the starting configurations. Because the effects of electron correlations may play important roles in the present model systems, the quantum chemical calculations were performed using the second‐order Møller–Plesset perturbation theory (MP2) with the resolution of the identity (RI) approximation and the TZVP basis set (this process is abbreviated RIMP2/TZVP calculations) .…”

Section: Methodsmentioning

confidence: 99%

Proton dissociation and transfer in hydrated phosphoric acid clusters

Suwannakham

Chaiwongwattana

Sagarik

2015

Int J of Quantum Chemistry

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The dynamics and mechanisms of proton dissociation and transfer in hydrated phosphoric acid (H3PO4) clusters under excess proton conditions were studied based on the concept of presolvation using the H3PO4–H3O+–nH2O complexes (n = 1–3) as the model systems and ab initio calculations and Born–Oppenheimer molecular dynamics (BOMD) simulations at the RIMP2/TZVP level as model calculations. The static results showed that the smallest, most stable intermediate complex for proton dissociation (n = 1) is formed in a low local‐dielectric constant environment (e.g., ε = 1), whereas proton transfer from the first to the second hydration shell is driven by fluctuations in the number of water molecules in a high local‐dielectric constant environment (e.g., ε = 78) through the Zundel complex in a linear H‐bond chain (n = 3). The two‐dimensional potential energy surfaces (2D‐PES) of the intermediate complex (n = 1) suggested three characteristic vibrational and 1H NMR frequencies associated with a proton moving on the oscillatory shuttling and structural diffusion paths, which can be used to monitor the dynamics of proton dissociation in the H‐bond clusters. The BOMD simulations over the temperature range of 298–430 K validated the proposed proton dissociation and transfer mechanisms by showing that good agreement between the theoretical and experimental data can be achieved with the proposed rate‐determining processes. The theoretical results suggest the roles played by the polar solvent and iterate that insights into the dynamics and mechanisms of proton transfer in the protonated H‐bond clusters can be obtained from intermediate complexes provided that an appropriate presolvation model is selected and that all of the important rate‐determining processes are included in the model calculations. © 2015 Wiley Periodicals, Inc.

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Section: Methodsmentioning

confidence: 99%

Proton dissociation and transfer in hydrated phosphoric acid clusters

Suwannakham

Chaiwongwattana

Sagarik

2015

Int J of Quantum Chemistry

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“…in the previous work were used in the investigations of the CH 3 OH þ 2 (CH 3 OH) n complexes, n ¼ 1-4; (1) searching for the H-bond structures which could be intermediate states in the structural diffusion pathway, using the test-particle model (T-model) potentials; [20][21][22][23][24][25] (2) refining the computed H-bond structures using B3LYP/TZVP calculations; (3) BOMD simulations using the refined structures as the starting configurations. In the present work, the choice of n ¼ 1-4 is justified by B3LYP/6-31þG(d) calculations and vibrational predissociation spectroscopy of protonated CH 3 OH clusters, [15] in which the proton transfer in linear H-bond chain was concluded to involve the CH 3 OH tetramer and pentamer (n ¼ 3 and 4, respectively).…”

Section: Oh;md Bamentioning

confidence: 99%

Dynamics and mechanism of structural diffusion in linear hydrogen bond

et al. 2011

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Dynamics and mechanism of proton transfer in a protonated hydrogen bond (H-bond) chain were studied, using the CH(3)OH(2)(+)(CH(3)OH)(n) complexes, n = 1-4, as model systems. The present investigations used B3LYP/TZVP calculations and Born-Oppenheimer MD (BOMD) simulations at 350 K to obtain characteristic H-bond structures, energetic and IR spectra of the transferring protons in the gas phase and continuum liquid. The static and dynamic results were compared with the H(3)O(+)(H(2)O)(n) and CH(3)OH(2)(+)(H(2)O)(n) complexes, n = 1-4. It was found that the H-bond chains with n = 1 and 3 represent the most active intermediate states and the CH(3)OH(2)(+)(CH(3)OH)(n) complexes possess the lowest threshold frequency of proton transfer. The IR spectra obtained from BOMD simulations revealed that the thermal energy fluctuation and dynamics help promote proton transfer in the shared-proton structure with n = 3 by lowering the vibrational energy for the interconversion between the oscillatory shuttling and structural diffusion motions, leading to a higher population of the structural diffusion motion than in the shared-proton structure with n = 1. Additional explanation on the previously proposed mechanisms was introduced, with the emphases on the energetic of the transferring proton, the fluctuation of the number of the CH(3)OH molecules in the H-bond chain, and the quasi-dynamic equilibriums between the shared-proton structure (n = 3) and the close-contact structures (n ≥ 4). The latter prohibits proton transfer reaction in the H-bond chain from being concerted, since the rate of the structural diffusion depends upon the lifetime of the shared-proton intermediate state.

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“…All the H-bond complexes which could serve as precursors and transition state complexes in proton transfer pathways were searched, characterized and analyzed. In order to effectively scan the intermolecular potential energy surfaces, test-particle model (T-model) potentials [30][31][32][33][34][35][36][37][38][39] were constructed and employed in the calculations of the equilibrium structures and interaction energies of the hydrated complexes. Since the applicability of the T-model had been discussed in details in our previous studies, [30][31][32][33][34][35][36][37][38][39] only some important aspects relevant to the geometry optimizations will be briefly summarized using the CH 3 OH-H 3 O + -H 2 O 1 : 1 : 1 complex as an example.…”

Section: Searching For Potential Precursors and Transition State Comp...mentioning

confidence: 99%

Proton transfer reactions and dynamics in CH₃OH–H₃O⁺–H₂O complexes

Sagarik

Chaiwongwattana

Vchirawongkwin

et al. 2010

Phys. Chem. Chem. Phys.

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Proton transfer reactions and dynamics in hydrated complexes formed from CH(3)OH, H(3)O(+) and H(2)O were studied using theoretical methods. The investigations began with searching for equilibrium structures at low hydration levels using the DFT method, from which active H-bonds in the gas phase and continuum aqueous solution were characterized and analyzed. Based on the asymmetric stretching coordinates (Deltad(DA)), four H-bond complexes were identified as potential transition states, in which the most active unit is represented by an excess proton nearly equally shared between CH(3)OH and H(2)O. These cannot be definitive due to the lack of asymmetric O-H stretching frequencies (nu(OH)) which are spectral signatures of transferring protons. Born-Oppenheimer molecular dynamics (BOMD) simulations revealed that, when the thermal energy fluctuations and dynamics were included in the model calculations, the spectral signatures at nu(OH) approximately 1000 cm(-1) appeared. In continuum aqueous solution, the H-bond complex with incomplete water coordination at charged species turned out to be the only active transition state. Based on the assumption that the thermal energy fluctuations and dynamics could temporarily break the H-bonds linking the transition state complex and water molecules in the second hydration shell, elementary reactions of proton transfer were proposed. The present study showed that, due to the coupling among various vibrational modes, the discussions on proton transfer reactions cannot be made based solely on static proton transfer potentials. Inclusion of thermal energy fluctuations and dynamics in the model calculations, as in the case of BOMD simulations, together with systematic IR spectral analyses, have been proved to be the most appropriate theoretical approaches.

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Test-particle model potentials for hydrogen-bonded complexes: Complexes formed from HCN, HF, H2O, NH3, HCONH2, HCONHCH3, guanine and cytosine

Cited by 24 publications

References 43 publications

Proton dissociation and transfer in hydrated phosphoric acid clusters

Proton dissociation and transfer in hydrated phosphoric acid clusters

Dynamics and mechanism of structural diffusion in linear hydrogen bond

Proton transfer reactions and dynamics in CH₃OH–H₃O⁺–H₂O complexes

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Test-particle model potentials for hydrogen-bonded complexes: Complexes formed from HCN, HF, H2O, NH3, HCONH2, HCONHCH3, guanine and cytosine

Cited by 24 publications

References 43 publications

Proton dissociation and transfer in hydrated phosphoric acid clusters

Proton dissociation and transfer in hydrated phosphoric acid clusters

Dynamics and mechanism of structural diffusion in linear hydrogen bond

Proton transfer reactions and dynamics in CH3OH–H3O+–H2O complexes

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Product

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Proton transfer reactions and dynamics in CH₃OH–H₃O⁺–H₂O complexes