Daengngern, Rathawat

Preferred name

Alternative Name

Daengngern, R.

Main Affiliation

School of Science

rathawat.da@kmitl.ac.th

Now showing 1 - 10 of 23

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Nitric Oxide Decomposition via Selective Catalytic Reduction by Ammonia on a Transition-Metal Cluster of W2TcO6
(2022-06-23)
Daengngern, Rathawat
;
Kaewprasong, Kittikorn
Decomposition of nitric oxide (NO) gas on a reactive transition-metal cluster of W<inf>2</inf>TcO<inf>6</inf>has been examined and investigated via selective catalytic reduction by ammonia (NH<inf>3</inf>-SCR) using the M06-L density functional method. The transition-metal cluster of W<inf>2</inf>TcO<inf>6</inf>can be employed to transform NO to N<inf>2</inf>gas efficiently over an active site of tungsten (W). A reaction mechanism of NO conversion based on the NH<inf>3</inf>-SCR process has been elucidated by a potential energy surface along the reaction pathways. The reaction pathways of this NH<inf>3</inf>-SCR process begin with adsorption of NH<inf>3</inf>, adsorption of NO to the cluster, formation of nitrosamine (NH<inf>2</inf>NO) and NHNO/NHNOH intermediates, and rearrangement of NHNO/NHNOH to obtain N<inf>2</inf>and H<inf>2</inf>O, respectively. Notably, a significant NH<inf>2</inf>NO as a key intermediate, namely, "nitrosamine", must be formed before further steps can take place in the generation of N<inf>2</inf>from NO, followed by the involvement of the NHNO or NHNOH intermediate. From our calculated results, the NHNO intermediate via TS3a is found in pathway a, while NHNOH is found in pathway b via TS3b. Pathway b has a lower energy barrier of 35.1 kcal/mol than pathway a with an energy barrier of 41.8 kcal/mol, indicating that pathway b should be more energetically favorable. The step for NHNO intermediate rearrangement is a rate-determining step for the reaction occurring through pathway a, which is found to be more difficult in accordance with a difficult N-H bond cleavage to form the NNOH intermediate before N<inf>2</inf>formation. The overall reaction is an exothermic process with thermodynamic and kinetic favors. Thus, this bimetallic W<inf>2</inf>TcO<inf>6</inf>cluster could be used as a promising and active catalyst for NO decomposition via the NH<inf>3</inf>-SCR process to an eco-friendly gas, that is, N<inf>2</inf>
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Unlocking efficient CO2–to–methanol conversion on frustrated Lewis pair-functionalized UiO–67: A synergistic approach using DFT and SISSO
(2025-10-01)
Yodsin, Nuttapon
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Pimbaotham, Pimjai
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Maihom, Thana
;
Daengngern, Rathawat
;
Tachikawa, Masanori
Metal–organic framework-based catalysts demonstrate considerable promise for converting CO<inf>2</inf> into valuable chemicals, particularly when combined with Frustrated Lewis Pairs (FLPs) to enhance H<inf>2</inf> dissociation during hydrogenation reactions. This study employs density functional theory (DFT) calculations to investigate modified UiO–67 frameworks wherein FLPs are introduced via eight different functional groups (UiO–67–X) into the organic linker to facilitate H<inf>2</inf> activation during CO<inf>2</inf> hydrogenation to methanol (CH<inf>3</inf>OH). The reaction proceeds through three stages: (i) hydrogenation of CO<inf>2</inf> to formic acid (HCOOH), (ii) conversion of HCOOH to formaldehyde (HCHO), and (iii) hydrogenation of HCHO to CH<inf>3</inf>OH. This study specifically focuses on steps (ii) and (iii), analyzing the detailed reaction mechanisms using optimized molecular structures and Gibbs free energy calculations to acquire insights into methanol formation on UiO–67–X. During HCOOH conversion to HCHO, adsorbed H<inf>2</inf> undergoes heterolytic cleavage at the FLP sites, producing a proton (H+) and a hydride (H−) for subsequent HCOOH hydrogenation and dehydration. The energy barriers identified at this stage represent key kinetic limitations hindering efficient CO<inf>2</inf>-to-methanol conversion. Similarly, HCHO conversion to CH<inf>3</inf>OH proceeds via H<inf>2</inf> dissociation, followed by concerted H+/H− transfer. Among the tested UiO–67–X catalysts, UiO–67–B(CH<inf>3</inf>)<inf>2</inf> exhibits the highest catalytic activity for CO<inf>2</inf> hydrogenation to methanol. Kinetic analyses are performed to assess reaction rates across a relevant temperature range, highlighting the notable influence of functional groups on catalytic performance. Additionally, the Sure Independence Screening and Sparsifying Operator (SISSO) machine-learning approach is used to identify optimal physical descriptors and derive a predictive model for the energetic span (δG), considerably lowering the computational cost associated with full reaction pathway calculations. Statistical validation confirms the robustness of these predictions. Overall, these findings underscore the vital role of FLP-assisted H<inf>2</inf> dissociation in promoting CO<inf>2</inf> hydrogenation to CH<inf>3</inf>OH, with UiO–67–B(CH<inf>3</inf>)<inf>2</inf> serving as a promising catalyst.
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Proton exchange of carbonic acid and methylamine complex accelerated by a single-water molecule via intermolecular hydrogen bonding: A theoretical investigation
(2024-06-01)
Panbo, Pakuna
;
Payaka, Apirak
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Salaeh, Rusrina
;
Daengngern, Rathawat
A theoretical investigation of the microsolvation effect on proton exchange (PE) between carbonic acid and methylamine (CA-MTA) has been explored by quantum dynamics simulations. The structural, energy, and dynamic properties of the CA-MTA complex with and without an explicit water molecule are elucidated at the molecular level. The reactions from this study have been clarified into different types: single-step PE (SSPE) and stepwise PE (SWPE). Without the water molecule, the SSPE mechanism is hardly found but observable with a low probability of 0.2. In particular, the water molecule interacting through intermolecular hydrogen-bonded network between CA and MTA in CA-MTA-W<inf>in</inf> could affect PE by showing both SSPE and SWPE mechanisms. In addition, the existing water molecule plays the significant role in shortening intermolecular hydrogen bonding interactions within the complex resulting in increasing the probability of PE up to 0.92 especially in CA-MTA-W<inf>out</inf>. Hence, one water molecule could be used to provide reliable results to represent the significant activity that occurs for the proton exchangeability of the CA and MTA complex.
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Ultrasonic-driven synthesis of Cu-chlorophyllin-stabilized silver nanoparticles for high-efficiency antimicrobial surgical suture coatings
(2025-12-01)
Sombutjiraporn, Saran
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Mathaweesansurn, Arjnarong
;
Daengngern, Rathawat
;
Detsri, Ekarat
A novel Cu-chlorophyllin-stabilized silver nanoparticle (Ag0<inf>NPs</inf>-Chl<inf>Cu</inf>) with potent antimicrobial properties was synthesized for the first time using an ultrasonically driven chemical reduction approach. In this approach, Cu-chlorophyllin (Chl<inf>Cu</inf>) acts as a stabilizing ligand, while sodium borohydride functions as the chemical reductant. The formation mechanism of Ag0-NPs<inf>CHL</inf> was elucidated, revealing that ultrasonic irradiation facilitates the in situ reduction of Ag (I) and its subsequent incorporation into the Chl<inf>Cu</inf> complex. Four pyrrole rings coordinate with Ag0<inf>NPs</inf> through four nitrogen atoms, which serve as adsorption sites for the anchorage of Ag0-NPs<inf>CHL</inf>. Characterization by XPS revealed the presence of Ag-N bonding involving pyrrole units on the FCC structure of Ag0<inf>NPs</inf>. Ag0<inf>NPs</inf>-Chl<inf>Cu</inf> demonstrated a zeta potential of (-) 35.57±3.54 mV with a spherical shape and an average size of 6.72±1.72 nm, resulting in a stable colloidal dispersion with a monodispersed index. The synthesized Ag0-NPs<inf>CHL</inf> nanocomposites were subsequently deposited onto polyamide surgical sutures via an electrostatic Layer-by-Layer (LbL) self-assembly technique. The coated sutures exhibited >99.9 % antibacterial efficiency against E. coli (ATCC25922), S. aureus (ATCC25923), and A. baumanii (ATCC19606). While nanoparticle accumulation was observed in human primary epidermal keratinocyte (HEKa) cells, no cytotoxic effects were detected in the epidermis. This study highlights the effectiveness of Chl<inf>Cu</inf> as a dual stabilizing and coordinating agent for Ag⁰<inf>NPs</inf>, offering a promising approach for developing antimicrobial surgical materials.
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The synergy of CHEF and ICT toward fluorescence ‘turn-on’ probes based on push-pull benzothiazoles for selective detection of Cu2+ in acetonitrile/water mixture
(2021-06-15)
Nootem, Jukkrit
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Daengngern, Rathawat
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Sattayanon, Chanchai
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Wattanathana, Worawat
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Wannapaiboon, Suttipong
New push-pull schiff base ligands based on benzothiazole (BZ) unit were developed for the selective detection of Cu2+ through fluorescence ‘turn-on’ mechanism. These derivatives with electron withdrawing trifluoromethyl (-CF<inf>3</inf>) and cyano (-CN) substituents (BZ2 and BZ3) demonstrated a prominent fluorescence enhancement upon copper ion binding which could be the results from the synergistic effect between the chelation-enhanced fluorescence (CHEF) and the intramolecular charge transfer (ICT) processes. In addition, these compounds displayed 1:1 binding with Cu2+ with low limits of detection of 0.77 μM and 0.64 μM for BZ2 and BZ3, respectively, in acetonitrile-water (3:1 v/v) media. The electronic and photophysical properties of these BZ ligands and the copper ion complexes were modelled by the density functional theory (DFT) and the time-dependent density functional theory (TD-DFT) calculations, respectively. Analysis of X-ray absorption spectra probed at Cu K-edge of Cu2+-BZ mixtures revealed the complex formation of BZ ligands with the targeted Cu2+ and confirmed the non-centrosymetric structures of the complexes as predicted by the DFT calculation. The electron density distributions of the HOMO-LUMOs in the computational results as well as large stokes shifts of the ligand-metal complexes in the experimental data confirmed the strong ICT effect after Cu2+ binding which is a key process promoting fluorescence ‘turn-on’ mechanism.
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Tautomeric enhancement of 2-(1H-pyrazol-5-yl)pyridine in photoinduced proton transfer by water-assisted molecules
(2024-09-20)
Salaeh, Rusrina
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Inporn, Wutthana
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Chansen, Warinthon
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Kungwan, Nawee
;
Daengngern, Rathawat
Theoretical insight of excited state proton transfer (ESPT) in 2-(1H-pyrazol-5-yl)pyridine abbreviated as PPP interacting with water wires: PPP(H<inf>2</inf>O)<inf>n</inf> where n = 1–3 has been presented in both static and dynamics studies. Explicit water molecules placed around PPP have been simulated to elucidate the intermolecular hydrogen bonding interactions between them. Hydrogen bond strengthening in the excited state (S<inf>1</inf>) has been verified by shorter bond distances and redshift of IR vibrational spectra involving the proton transfer (PT) process. Furthermore, on-the-fly excited state dynamics simulations of all complexes have been performed to provide detailed information on the PT mechanism. The dynamic results show that one water molecule added to the neighboring PPP as an intermolecular hydrogen bonding bridge can promote double excited state intermolecular proton transfer up to 36% compared with its intrinsic intramolecular hydrogen bond of the PPP system. Meanwhile adding a second or third water molecule could decrease the probabilities of PT. Especially in PPP(H<inf>2</inf>O)<inf>3</inf>, a rearrangement of water molecules is observed that PT occurs via one water molecule. Hence, the models with explicit water molecules interacting with PPP as intermolecular hydrogen bonding bridge are a great representative role played by water molecules of the PT process at the molecular level.
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A theoretical investigation into the demethylation mechanism of dimethylsulfide over the W3O6 cluster
(2025-07-01)
Aziz, Hafiz Aji
;
Kungwan, Nawee
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Gleeson, Duangkamol
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Saelee, Tinnakorn
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Daengngern, Rathawat
Understanding how dimethyl sulfide (DMS) breaks down to form value-added products such as methanol on transition metal oxide catalysts is important for improving desulfurization processes. In this study, the reaction mechanism over a tungsten oxide cluster (W₃O₆) is elucidated using density functional theory (DFT) at the M06-L/LANL2DZ/aug-cc-pVTZ level of theory. Two competing mechanistic pathways were discovered over the W₃O₆ cluster: Pathway A) direct demethylation followed by methanol desorption and Pathway B) a water-assisted concerted demethylation pathway. Pathway A involves sequential steps with a moderate demethylation barrier (49.43 kcal/mol), but a significantly higher barrier (68.78 kcal/mol) for subsequent methanol formation, imposing a kinetic bottleneck. Remarkably, Pathway B, mediated by an explicit water molecule, facilitates a lower-barrier concerted transformation (56.19 kcal/mol), effectively bypassing the high-energy intermediate. Kinetic modeling via Transition State Theory and the Energetic Span Model reveal that despite the very low turnover frequency (TOF = 9.29 × 10−30 s⁻¹), the water-assisted pathway is energetically superior. These findings highlight the important role of water in helping the reaction proceed and offer insight for designing better catalysts for sulfur removal from DMS to methanol over the W₃O₆ cluster.
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Experimental and Theoretical Exploration of Ultrafast Excited State Double Proton Transfer in 2,5-Bis(2-benzimidazolyl)hydroquinone
(2025-07-01)
Prommin, Chanatkran
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Chaihan, Komsun
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Daengngern, Rathawat
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Mori, Seiji
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Akutsu-Suyama, Kazuhiro
The electronic properties and excited-state intramolecular double proton transfer of 2,5-bis(2-benzimidazolyl)hydroquinone (bis-HBI) in a nonpolar solvent were investigated using a combined experimental and theoretical approach. Bis-HBI was successfully synthesized and its characterization was confirmed through 1H NMR and FT-IR. Three distinct emission peaks of bis-HBI were observed at 484, 597, and 730 nm, which were theoretically assigned to the di-enol (EE), mono-keto (EK), and di-keto (KK) species, respectively. The emission peaks at longer wavelengths (597 and 730 nm) are attributed to tautomerization upon photoexcitation and are assigned to the mono-keto and di-keto species, which result from multiple proton transfers. These species exhibit kinetically and thermodynamically favorable behaviors. On-the-fly dynamics simulations reveal that the double proton transfer process occurs ultrafast, within 433 fs. Additionally, both backward and forward proton transfers are observed during the first and second proton transfers, indicating tautomeric equilibria between the three species—EE, EK, and KK—on the excited-state surface. This is consistent with the potential energy surface along the proton transfer coordinate.
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Effect of water microsolvation on the excited-state proton transfer of 3-hydroxyflavone enclosed in -cyclodextrin
(2021-02-02)
Kerdpol, Khanittha
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Daengngern, Rathawat
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Sattayanon, Chanchai
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Namuangruk, Supawadee
;
Rungrotmongkol, Thanyada
The effect of microsolvation on excited-state proton transfer (ESPT) reaction of 3-hydroxyflavone (3HF) and its inclusion complex with -cyclodextrin (-CD) was studied using computational approaches. From molecular dynamics simulations, two possible inclusion complexes formed by the chromone ring (C-ring, Form I) and the phenyl ring (P-ring, Form II) of 3HF insertion to -CD were observed. Form II is likely more stable because of lower fluctuation of 3HF inside the hydrophobic cavity and lower water accessibility to the encapsulated 3HF. Next, the conformation analysis of these models in the ground (S0) and the first excited (S1) states was carried out by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations, respectively, to reveal the photophysical properties of 3HF influenced by the -CD. The results show that the intermolecular hydrogen bonding (interHB) between 3HF and -CD, and intramolecular hydrogen bonding (intraHB) within 3HF are strengthened in the S1 state confirmed by the shorter interHB and intraHB distances and the red-shift of O-H vibrational modes involving in the ESPT process. The simulated absorption and emission spectra are in good agreement with the experimental data. Significantly, in the S1 state, the keto form of 3HF is stabilized by -CD, explaining the increased quantum yield of keto emission of 3HF when complexing with -CD in the experiment. In the other word, ESPT of 3HF is more favorable in the -CD hydrophobic cavity than in aqueous solution.
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Bodipy-pyridylhydrazone probe for fluorescence turn-on detection of fe3+ and its bioimaging application
(2021-07-01)
Nootem, Jukkrit
;
Sattayanon, Chanchai
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Daengngern, Rathawat
;
Kamkaew, Anyanee
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Wattanathana, Worawat
A novel pyridylhydrazone-tethered BODIPY (BODIPY-PH) was synthesized, fully characterized via nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopic (FTIR), and single-crystal X-ray diffraction (SC-XRD) techniques, and developed for the selective detection of Fe3+ through fluorescent enhancement process. This derivative showed 1:1 binding with Fe3+ in an acetonitrile-water mixture (1:9 v/v) with the binding constant (K) of 5.4 × 104 M−1 and the limit of detection of 0.58 µM. The Fe3+ complexation reaction has been proved to be a reversible process and could be effectively repeated up to three cycles. The electronic properties of BODIPY-PH and its Fe3+ complex modeled by the density functional theory (DFT) method suggested the presence of chelation-enhanced fluorescence (CHEF) effect in the Fe3+ binding reaction. The X-ray absorption spectroscopy (XAS) probed at Fe K-edge confirmed the complex formation between BODIPY-PH and the Fe3+ in an octahedral geometry. Finally, bioimaging against human embryonic kidney (Hek293) cell, through confocal fluorescence microscopic technique indicated that the BODIPY-PH displayed good permeability and low toxicity toward the tested cell lines and showed enhanced fluorescent signal in the cells incubated with Fe3+ proving its capability for Fe3+ analysis in cellular matrix.

Daengngern, Rathawat

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