Daengngern, Rathawat

Preferred name

Alternative Name

Daengngern, R.

Main Affiliation

School of Science

rathawat.da@kmitl.ac.th

Now showing 1 - 10 of 10

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Oxotitanium-porphyrin for selective catalytic reduction of NO by NH3: A theoretical mechanism study
(2018-01-01)
Daengngern, Rathawat
;
Maitarad, Phornphimon
;
Shi, Liyi
;
Zhang, Dengsong
;
Kungwan, Nawee
The reaction mechanism of the selective catalytic reduction of NO by NH<inf>3</inf> (NH<inf>3</inf>-SCR) on an oxotitanium-porphyrin catalyst was systematically investigated by using density functional theory calculations with the M06L functional. The reaction was proposed to follow the nitrite mechanism over the two forms of active sites; the oxotitanium-porphyrin Lewis acid site (TiO-por) and the Brønsted acid site (TiOH-por). The reaction path consisted of (i) nitrite formation, (ii) NH<inf>3</inf> oxidation, (iii) formation of NH<inf>2</inf>NO and NHNOH intermediates, and (iv) N<inf>2</inf> and H<inf>2</inf>O product formation. The obtained calculations showed that the formation of the NHNOH intermediate was the rate determining step for both active sites with the energy barriers (E<inf>a</inf>) of 32.2 and 36.2 kcal mol-1 for the Lewis and Brønsted acid sites, respectively. It is worth noting that the activation energy for NHNOH formation over the oxotitanium-porphyrin active sites was found to be in the same range as that of vanadium oxide cluster models. Furthermore, the product formations of N<inf>2</inf> and H<inf>2</inf>O over the Lewis and Brønsted acid sites of oxotitanium-porphyrin were exothermic processes with reaction energies (E<inf>r</inf>) of -67.1 and -39.0 kcal mol-1, respectively. Thus, in conclusion, the oxotitanium-porphyrin could theoretically act as an alternative catalyst for NH<inf>3</inf>-SCR of NO and it would be challenging to test it in experimental studies.
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A spectroscopic study of indigo dye in aqueous solution: A combined experimental and TD-DFT study
(2018-12-01)
Jiwalak, Naparat
;
Daengngern, Rathawat
;
Rungrotmongkol, Thanyada
;
Jungsuttiwong, Siriporn
;
Namuangruk, Supawadee
This study reports UV–Visible spectra and electronic structures of indigo (IG) in aqueous solution using a combination of experimental and theoretical methods. In the visible region, the experimental absorption spectrum of the solution showed a broad peak with the longest wavelength of maximal absorption (λ<inf>max</inf>) value at 708 nm. For the theoretical method, a trans-IG monomer and a trans-IG bound with two water molecules (IG.2W) were optimized in the ground state using the B3LYP and B3LYP-D3 calculations with the 6-31 + G(d,p) basis set and the SCRF-CPCM model for taking solvent effect into account was also applied. Sequentially, the UV–Visible spectra and λ<inf>max</inf> of the optimized trans-IG and IG.2W models in the implicit water were simulated by the time-dependent density functional theory (TD-DFT) calculations. The TD-DFT methods including BLYP, B3LYP, PBE0, CAM-B3LYP, M06-2X, ωB97XD, LC-BLYP, and LC-ωPBE functionals without and with the D3 correction and the 6-31 + G(d,p) basis set were selected. The results pointed out that BLYP and BLYP-D3 were the best methods because they could reproduce the experimental λ<inf>max</inf> value of IG in aqueous solution. The predicted λ<inf>max</inf> values of IG.2W were almost equal to 708 nm (the experimental data), indicating that IG.2W could be responsible for optical properties of IG.
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Theoretical Insights on Solvent Control of Intramolecular and Intermolecular Proton Transfer of 2-(2′-Hydroxyphenyl)benzimidazole
(2017-08-10)
Prommin, Chanatkran
;
Kanlayakan, Narissa
;
Chansen, Warinthon
;
Salaeh, Rusrina
;
Kerdpol, Khanittha
Excited-state proton transfer (ESPT) processes of 2-(2′-hydroxyphenyl)benzimidazole (HBI) and its complexation with protic solvents (H<inf>2</inf>O, CH<inf>3</inf>OH, and NH<inf>3</inf>) have been investigated by both static calculations and dynamics simulations using density functional theory (DFT) at B3LYP/TZVP theoretical level for ground state (S<inf>0</inf>) and time-dependent (TD)-DFT at TD-B3LYP/TZVP for excited state (S<inf>1</inf>). For static calculations, absorption and emission spectra, infrared (IR) vibrational spectra of O-H mode, frontier molecular orbitals (MOs), and potential energy curves (PECs) of proton transfer coordinate were analyzed. Simulated absorption and emission spectra show an agreement with available experimental data. The hydrogen bond strengthening in the S<inf>1</inf> state has been proved by the changes of IR vibrational spectra and bond parameters of the hydrogen moiety with those of the S<inf>0</inf> state. The MOs provide the visual electron density redistribution confirming the hydrogen bond strengthening mechanism. The PECs show that the proton transfer (PT) process is easier to occur in the S<inf>1</inf> state than the S<inf>0</inf> state. Moreover, on-the-fly dynamics simulations of all systems were carried out to provide the detailed information on time revolution. The results revealed that the excited-state intermolecular proton transfer for HBI is fast, whereas the excited-state intermolecular proton transfer for HBI with protic solvents are slower than that of HBI because the competition between intra- and intermolecular hydrogen-bonds between HBI and protic solvent. These intermolecular hydrogen-bonds hinder the formation of tautomer, hence explaining the low quantum yield found in the protic solvent experiment. Especially for HBI complexing with methanol, only ESIntraPT occurs with small probability compared to HBI with water and ammonia.
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Theoretical study on influence of geometry controlling over the excited-state intramolecular proton transfer of 10-hydroxybenzo[h]quinoline and its derivatives
(2017-08-01)
Chansen, Warinthon
;
Salaeh, Rusrina
;
Prommin, Chanatkran
;
Kerdpol, Khanittha
;
Daengngern, Rathawat
A structural modification on quinoline as a proton donor of 10-hydroxybenzo[h]quinoline (HBQ) giving different HBQ derivatives greatly affects their photophysical properties. In this study, the excited-state intramolecular proton transfer (ESIPT) reactions of HBQ and its derivatives with different geometries have been systematically investigated using DFT and TD-DFT at B3LYP/TZVP. Calculated absorption and emission spectra are used to describe the photophysical changes in which the absorption spectra of HBQ derivatives are blue-shifted compared with that of HBQ while their emission spectra are blue-shifted except those of 3,4-dihydro indene[1,2-b]pyrrole-8-ol (IPRO) and 2-(4H-pyrrol-2-yl)phenol (PRP) compounds with different proton donor and connecting moiety are red-shifted. From results of potential energy curves along the proton transfer (PT) coordinate, PT is favorable in the excited-state but not in the ground state. On-the-fly dynamics simulations in the excited-state are further employed to determine reaction mechanisms and the time evolution of PT. The ESIPT process easily occurs in most of the compounds except the IPRO with much high PT barrier. The ESIPT times in most compounds take place within 100 fs and PT probability is nicely anti-correlated with the PT barrier. Thus, the geometry changes alter the electronic spectra but do not affect ESIPT of HBQ derivatives. Moreover, once the PT is complete, the internal conversion is initiated by twisted skeleton, leading to lower intensity of tautomer emission.
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The effect of protic solvents on the excited state proton transfer of 3-hydroxyflavone: A TD-DFT static and molecular dynamics study
(2018-02-01)
Salaeh, Rusrina
;
Prommin, Chanatkran
;
Chansen, Warinthon
;
Kerdpol, Khanittha
;
Daengngern, Rathawat
The effect of intermolecular hydrogen bonding played by protic solvents (ammonia, methanol and water) on the excited state proton transfer (ESPT) reaction of 3-hydroxyflavone (3HF) was theoretically investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT). The formation of intermolecular hydrogen bond induced by protic solvents indicates that the intramolecular hydrogen bond may be interrupted in favor of a complex causing low quantum yield of keto emission and exhibiting dual emission (both enol and keto) in experiment. The strengthening of intermolecular hydrogen bond in the S<inf>1</inf> state has been confirmed by the red-shift of IR vibrational spectra and shorter bond distances involving proton transfer (PT) process in comparison with those of the S<inf>0</inf> state. From potential energy curves (PECs) of PT coordinate, PT process is likely to proceed in S<inf>1</inf> state and PT in 3HF(NH<inf>3</inf>) occurs more easily than those of 3HF(CH<inf>3</inf>OH) and 3HF(H<inf>2</inf>O) due to its lower barrier. Moreover, on-the-fly dynamics simulations of all complexes were carried out to provide the detailed information on the PT mechanism. The dynamic results show that ESPT process of 3HF with protic solvent takes place through intermolecular hydrogen bond with slower PT time (259, 117 and 104 fs for 3HF(NH<inf>3</inf>), 3HF(CH<inf>3</inf>OH) and 3HF(H<inf>2</inf>O), respectively) than that of 3HF (76 fs) via intramolecular hydrogen bond. Furthermore, the ultrafast PT time is found to be nicely correlated with polarity of solvent and PT probability is also anti-correlated with PT barrier.
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Excited-state intramolecular proton transfer reactions of 2,5-bis(2′-benzoxazolyl)hydroquinone and its water cluster exhibiting single and double proton transfer: A TD-DFT dynamics simulation
(2019-07-15)
Daengngern, Rathawat
;
Salaeh, Rusrina
;
Saelee, Tinnakorn
;
Kerdpol, Khanittha
;
Kungwan, Nawee
Detailed pictures of the excited-state intramolecular proton transfer (ESIPT)of 2,5-bis(2′-benzoxazolyl)hydroquinone (BHQ)and its water cluster have been investigated by dynamics simulations on the first lowest-excited energy using time-dependent density functional theory (TD-DFT). We focused on the structural, photophysical and dynamic properties of BHQ in the absence and presence of water molecules through intermolecular hydrogen bonds (interHBs). Our dynamics simulations reveal three possible mechanisms of the ESIPT processes: i)no proton transfer (No PT); ii)single PT (SPT); and iii)double PT (DPT), that could take place within the PT time of 160 fs via intrinsic intramolecular hydrogen bonds (intraHBs). The ESIPT mechanism of isolated BHQ elucidates that back PT is likely to be found at 64% rather than the SPT (32%)and DPT (4%), which is in good agreement with the experiments of dual fluorescence from di-enol and mono-keto emissions. Notably, the results from BHQ with water (BHQ-(H<inf>2</inf>O)<inf>2</inf>)reveal that the participation of water might produce a remarkable effect on promoting the SPT process up to 60% and DPT up to 7 times when compared to conditions of no water. The simulated probability of PT is well related to possible PT mechanisms regarding different tautomers in the fluorescence spectra found in previous experiments. The existence of di-keto tautomer arose from the DPT of BHQ and its water cluster and was not observed in the UV/Vis spectrum.
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Physico-chemical characterization of natural lake pigments obtained from Caesalpinia Sappan Linn. and their composite films for poly(lactic acid)-based packaging materials
(2018-10-01)
Girdthep, Sutinee
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Sirirak, Jitnapa
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Daranarong, Donraporn
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Daengngern, Rathawat
;
Chayabutra, Supanee
A newly colored biodegradable PLA-based film was fabricated from a compatibilized poly(lactic acid) poly(butylene adipate-co-terephthalate) blend (PLA/PBAT/TBT) using the natural lake pigment of Sappan. The natural lake pigment of Sappan was prepared as a Sappan colorant-adsorbed kaolinite (S-KT). S-KT composite in the form of an insoluble pigment and was prepared via co-precipitation and adsorption under basic conditions. It had a pinkish-red color and a maximum absorption of 516 nm. The stability of the natural lake pigment was improved and was confirmed by the improvement of the initial and maximum degradation temperatures from the TGA results, which could be attributed to the electrostatic attraction due to the process of chelation. The chelation that occurred between the Al(III) ion, the oxygen atoms of kaolinite surface and the brazilein molecules was proposed. The influence of S-KT content in the compatibilized blended films, known as S-KT composite films, was investigated by comparison with the KT composite film and the film without fillers. When the content of S-KT increased, the S-KT composite films exhibited a darker pinkish-red color. The mechanical properties in terms of strength increased due to KT acting as a nucleating agent with a 92% increase in the heat of crystallization in the S-KT7 film when compared with the film without fillers. The exfoliated-intercalated structure of S-KT resulted from the KT platelet disaggregation by brazilein adsorption and the intercalating of Al3+cations chelation as a hybrid interaction on the KT surface, which was indicated by the SEM. In addition, S-KT composite film could effectively resist heat at high temperatures with the maximum degradation temperature ranging from 337 to 393° C. This occurred as a result of KT clay acting as a superior insulator. Based on these results, the natural lake pigments presented the potential to be employed in the biodegradable polymer and could be used as a substitute for more toxic pigments. The biodegradable PLA-based colored films described here have a potential to be used in packaging applications. They offer the potential to increase the value-added appeal of products, with the benefit of being considered environmentally friendly by the consumer.
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Theoretical Prediction and Analysis of the UV/Visible Absorption and Emission Spectra of Chiral Carbon Nanorings
(2018-09-20)
Daengngern, Rathawat
;
Camacho, Cristopher
;
Kungwan, Nawee
;
Irle, Stephan
UV/vis absorption and emission spectra of recently synthesized chiral carbon nanorings were simulated using first-principles-based molecular dynamics and time-dependent density functional theory (TD-DFT). The chiral carbon nanorings are derivatives of the [n]cycloparaphenylene ([n]CPP) macrocycles, containing an acene unit such as naphthalene, ([n]CPPN), anthracene ([n]CPPA), and tetracene ([n]CPPT), in addition to n paraphenylene units. In order to study the effect of increasing molecular size on absorption and emission spectra, we investigated the cases where n = 6 and 8. Frontier molecular orbital analysis was carried out to give insight into the degree of excitation delocalization and its relationship to the predicted absorption spectra. The lowest excited singlet state S<inf>1</inf> corresponds to a HOMO-LUMO π-π∗ transition, which is allowed in all chiral carbon nanorings due to lack of molecular symmetry, in contrast to the forbidden HOMO-LUMO transition in the symmetric [n]CPP molecules. The S<inf>1</inf> absorption peak exhibits a blue-shift with increasing number of paraphenylene units in particular for [n]CPPN and [n]CPPA and less so in the case of [n]CPPT. In the case of CPPN and CPPA, the transition density is mainly localized over a semicircle of the macrocycle with the acene unit in its center but is strongly localized on the tetracene unit in the case of CPPT. Molecular dynamics simulations performed on the excited state potential energy surfaces reveal red-shifted emission of these chiral carbon nanorings when the size of the π-conjugated acene units is increased, although the characteristic [n]CPP blue-shift with increasing paraphenylene unit number n remains apparent. The anomalous emission blue-shift is caused by the excited state bending and torsional motions that stabilize the π HOMO and destabilize the π∗ LUMO, resulting in an increasing HOMO-LUMO gap.
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Heteroatom effect on photophysical properties of 2-(2′-hydroxyphenyl)benzimidazole and its derivatives as fluorescent dyes: A TD-DFT study
(2017-08-01)
Manojai, Natthaporn
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Daengngern, Rathawat
;
Kerdpol, Khanittha
;
Ngaojampa, Chanisorn
;
Kungwan, Nawee
The effects of hetero nitrogen substitution on the photophysical properties and excited-state intramolecular proton transfer (ESIPT) of HBX derivatives (HBI, HBO and HBT where X=NH, O and S, respectively) were investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations at B3LYP/6-311+G(d,p) level, which is the suitable method of choice validated from various density functionals. Geometries and absorption spectra of all derivatives as well as emission spectra of selected derivatives were calculated at the same level of theory. The hetero nitrogen substitution of HBX resulted in the red shift emission spectra, which implies that the lone pair of electron in the substituted nitrogen has the effect on the π-conjugated system. In addition, results of frontier molecular orbital analysis show that vertical S<inf>0</inf>→S<inf>1</inf> transition of these molecules corresponds essentially to the excitation from HOMO (π) to LUMO (π*). The potential energy curves (PECs) of selected derivatives were used to investigate the occurrence of ESIPT and the chance was found in this order: HBT>HBI>HBO. The hetero nitrogen substituted on 1,4 and 3,4 position of HBX derivatives could easily facilitate the ESIPT process, because the nitrogen substitution makes O–H bond of selected HBX derivatives weaker than those of other derivatives and the hydrogen bond in N–H becomes stronger in the excited state, resulting in lower PT barrier. The obtained information of the electronic structure, the photophysical property and the chance of ESIPT of hetero nitrogen substituted HBX molecules is useful for molecular design of fluorescent molecular probes.
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Nitric oxide oxidation on warped nanographene (C80H30): a DFT study
(2019-01-01)
Roongcharoen, Thantip
;
Kungwan, Nawee
;
Daengngern, Rathawat
;
Sattayanon, Chanchai
;
Namuangruk, Supawadee
The possible use of the recently synthesized warped nanographene C<inf>80</inf>H<inf>30</inf> for NO oxidation by O<inf>2</inf> molecule has been investigated using density functional theory. The reaction starts with the adsorption and dissociation of O<inf>2</inf> molecule on the central pentagon of C<inf>80</inf>H<inf>30</inf> with the activation energies of 24.2–26.6 kcal/mol depending on the active sites. Then, the dissociated O atoms readily oxidize NO to NO<inf>2</inf> twice. The first NO oxidation occurs with barrierless, while the second NO oxidation requires a small energy barrier of 16.0 kcal/mol. The low activation energy barrier pathway indicates high catalytic activity of this nanographene for NO oxidation. Charge analysis reveals that such high catalytic activity of nanographene is attributed to the charge transfer from the saddle-shaped C<inf>80</inf>H<inf>30</inf> to the dissociated O atoms which makes it reactive to NO molecule. Desorption of NO<inf>2</inf> product, which is the rate-limiting step of NO oxidation in some catalysts, is easily occurred in this nanographene (less than 2 kcal/mol), indicating the prevention of catalyst poisoning. This study suggests that C<inf>80</inf>H<inf>30</inf> nanographene is a promising catalyst for NO removal in ambient condition.

Daengngern, Rathawat

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