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Analyses on Molecular Properties of the Diamidinate Cr-I-Cr-I Complex by Multireference and DFT Approaches
(2019-09-12)
Huang, Gou-Tao
;
Yu, Jen-Shiang K.
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交大名義發表
;
生物科技學系
;
生物資訊及系統生物研究所
The model system of the diamidinate Cr-I-Cr-I complex is investigated by wave function theory (WET) and Kohn-Sham density functional theory (KS-DFT). The multireference perturbation theory (RASPT2) estimates a stabilization energy of ca. 20 kcal mol(-1) for the delta bonding. The multiconfiguration pair-density functional theory (MC-PDFT) with the ftPBE functional well predicts the singlet energy curve comparable to the RASPT2 level. For the KS-DFT scheme based on a single determinant, seven functionals including BP86, BLYP, PBE, B3LYP, M06-L, M06, and omega B97X-D are assessed: two types of functionals are classified according to the nature of the restricted and broken symmetry potential energy curves. The broken symmetry scheme with the type I functionals can give good results for the energy curve in agreement with the multireference calculations. In regard to the metal-metal bonding, the restricted KS-DFT calculations performed by all of the seven functionals yield inferior description due to the lack of significant multiconfigurational character. The Mayer bond order, the electron localization function, and electron density predicted by the broken symmetry formalism with the type II functionals are consistent with those obtained with the multireference theory.
Can the Radical Channel Contribute to the Catalytic Cycle of N-Heterocyclic Carbene in Benzoin Condensation?
(2018-12-21)
Hsieh, Ming-Hsiu
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Huang, Gou-Tao
;
Yu, Jen-Shiang K.
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交大名義發表
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生物科技學系
NHC can catalyze benzoin condensation via the key Breslow intermediate. EPR spectroscopy recently confirmed the existence of the radical species, but its catalytic role is still unclear. Herein, we use density functional approaches to study the radical-associated pathway in comparison with the nonradical mechanism reported previously. Theoretical investigations show that the nonradical path (Delta G(double dagger) = 18.7 kcal/mol) is more kinetically favorable than the radical route (Delta G(double dagger) = 27.6 kcal/mol), which is initialized by the hydrogen abstraction from the Breslow intermediate by benzaldehyde, leading to a radical pair. The product formation is thus dominated by the nonradical pathway. In addition, the Breslow intermediate is less stable than its keto form, which blocks the benzoin condensation, and the radical species could play an important role in assisting the tautomerization and promoting the catalytic reaction.
High-Rate Hydrogen Generation by Direct Sunlight Irradiation with a Triruthenium Complex
(2019-02-04)
Wu, Tung-Kung
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Chen, Yi-Ting
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Peng, Chun-Sheng
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Lin, Jia-Hoa
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Gliniak, Jacek
Herein we report a biomimetic triruthenium catalyst that, when under direct sunlight irradiation, facilitates high-rate H-2 production from formic acid (FA) dehydrogenation. The system consists of 2 mu mol of catalyst and 6 mu mol of tri-o-tolylphosphine in 1 mL of dimethylformamide (DMF) and 4 mL of FA/triethylamine (TEA; 5:2). With 0.4 mM catalyst loaded, a high turnover frequency of 1.15 X 10(6) h(-1) was detected when under direct sunlight irradiation. In an experiment with 0.2 mM catalyst loaded, more than 140 L of H-2 (280 L of H-2 + CO2) was produced, and a turnover number of approximately 2.78 X 10(6) was obtained within 5 h without decline in H-2 generation activity, making it suitable for high-rate H-2 production.
Enhanced hydrogen generation from formic acid by a biomimetic ruthenium complex with a covalently bonded phosphine ligand
(2017-04-13)
Chen, Mei-Hua
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Lin, Jia-Hoa
;
Li, Chuen-Ru
;
Gliniak, Jacek
;
Chang, Chin-Hao
A series of [Ru-2(CO)(5)(mu-SCH2CH2CH2S)PXS] complexes (Ru-2-S-2-PXS, X = phosphine ligands, S = 1-8) have been synthesized and evaluated for their photocatalytic H-2 generation efficiencies from formic acid decomposition. The [Ru-2(CO)(5)(mu-SCH2CH2CH2S)P(o-C6H4CH3)(3)] (Ru-2-S-2-PX4) catalyst + P(CH3)(3) ligand exhibited a high turnover frequency of 15,840h(-1) and turnover number of 24,536. A mechanistic investigation of the Ru-2-S-2-PX4 + FA/TEA catalyzed photocatalytic H-2 generation reaction using ATR-IR, EI-MS, and NMR techniques suggested that when Ru2-S2-PX4 was photoirradiated, the P(o-C6H4CH3)(3) was dissociated from the complex to form a new species, [Ru-2(CO)(5)(mu-SCH2CH2CH2S)]* (I). The free P(o-C6H4CH3)(3) then attacks a second molecule of Ru-2-S-2-PX4 to form Ru-2-S-2-(PX4)(2) and release of free CO, which is then combined with species I to form Ru-2-S-2. Subsequent attachment of formate ion to species Ru-2-S-2-PX4, Ru-2-S-2, and Ru-2-S-2-(PX4)(2) to form [Ru-2(CO)(5)(mu-SCH(2)CH(2)CH(2)SA]-HC00(-) (II), Ru-2-S-2-HCOO- (II') and Ru-2-S-2-PX4-HCOO- (II"), respectively. Rearrangement of complex II (or II' or II") and evolution of CO2 generate a transient complex [Ru-2(CO)(5)(mu-SCH2CH2CH2S)H (III), which then undergoes a protonation process to yield complex [Ru-2(CO)(5)(mu-SCH2CH2CH2S)H-2] (IV). Release of H-2 and re-incorporation of the formate anion as well as evolution of CO2 regenerates the active complex III and the cycle begins again. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Catalytic Roles of Histidine and Arginine in Pyruvate Class II Aldolase: A Perspective from QM/MM Metadynamics
(2017-12-01)
Huang, Gou-Tao
;
Yu, Jen-Shiang K.
;
生物科技學系
;
生物資訊及系統生物研究所
;
分子醫學與生物工程研究所
The retro-aldol reaction catalyzed by pyruvate class II aldolase is investigated with QM/MM metadynamics; this enzyme transforms the substrate of 4-hydrox-y-2-ketoacid into pyruvate and aldehyde through the aldol cleavage. The hydroxyl group of the substrate is deprotonated by His45 with the aid of the metal-bound water, while the metal-bound hydroxide proposed in the literature is observed as a transient species. The deprotonation appears to enhance substrate binding between the deprotonated substrate and the active site. The reactive alkoxide is further stabilized by the salt bridge of Arg70-Asp42, facilitating the following aldol cleavage. The simulations show that the C-C bond cleavage is the rate-determining step, and the calculated barrier of approximately 14 kcal mol(-1) agrees reasonably with experimental data.
Reversible Cleavage/Formation of the Chromium-Chromium Quintuple Bond in the Highly Regioselective Alkyne Cyclotrimerization
(2017-11-27)
Huang, Yu-Siang
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Huang, Gou-Tao
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Liu, Yao-Lun
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Yu, Jen-Shiang K.
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Tsai, Yi-Chou
Herein we report the employment of the quintuply bonded dichromium amidinates [Cr{(2)-HC(N-2,6-(Pr2C6H3)-Pr-i)(N-2,6-R2C6H3)}](2) (R=iPr (1), Me (7)) as catalysts to mediate the [2+2+2] cyclotrimerization of terminal alkynes giving 1,3,5-trisubstituted benzenes. During the catalysis, the ultrashort Cr-Cr quintuple bond underwent reversible cleavage/formation, corroborated by the characterization of two inverted arene sandwich dichromium complexes (-(6):(6)-1,3,5-(Me3Si)(3)C6H3)[Cr{(2)-HC(N-2,6-(Pr2C6H3)-Pr-i)(N-2,6-R2C6H3)}](2) (R=Pr-i (5), Me (8)). In the presence of sigma donors, such as THF and 2,4,6-Me3C6H2CN, the bridging arene 1,3,5-(Me3Si)(3)C6H3 in 5 and 8 was extruded and 1 and 7 were regenerated. Theoretical calculations were employed to disclose the reaction pathways of these highly regioselective [2+2+2] cylcotrimerization reactions of terminal alkynes.
Enzyme Catalysis that Paves the Way for S-Sulfhydration via Sulfur Atom Transfer
(2016-05-26)
Huang, Gou-Tao
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Yu, Jen-Shiang K.
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生物科技學系
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生物資訊及系統生物研究所
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Department of Biological Science and Technology
S-sulfhydration is generally anticipated to proceed through the transfer of the SH group (Nu-SH center dot center dot center dot S--R -> Nu(-)center dot center dot center dot HS-S-R). The other route involves the sulfur atom (5) transfer between two sulfhydryl anions (Nu-S-center dot center dot center dot S--R -> Nu(-)center dot center dot center dot S--S-R) and is considered electrostatically unfavorable. Mercaptopyruvate sulfurtransferase (MST, PDB code: 4JGT) catalyzes sulfur transfer from mercaptopyruvate to sulfur acceptors, and the first step of the reaction is the formation of cysteine (Cys248) persulfide via S-sulfhydration. Mechanistic studies on S-sulfhydration in MST using QM/MM methods show that the sulfur atom transfer initialized by the deprotonation of the Ser250/His74/Asp63 triad is kinetically preferred to the SH-promoted sulfur transfer. The calculated barrier of approximately 16 kcal mol(-1) for the S-0 transfer agrees well with experimental results. The electrostatic repulsion during the S-0 transfer can be sophisticatedly reduced by the aid of the Cys248-Gly249-Ser250-Gly251-Val252-Thr253 (CGSGVT) loop. Electrostatic potentials and frontier orbitals are also analyzed for the persulfide anion surrounded by the loop. The sulfur atom transfer which is seldom regarded possible is therefore facilitated with the assistance of the triad and the loop in the enzyme.
A Ruthenium-Based Biomimetic Hydrogen Cluster for Efficient Photocatalytic Hydrogen Generation from Formic Acid
(2015-04-20)
Chang, Chin-Hao
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Chen, Mei-Hua
;
Du, Wan-Shan
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Gliniak, Jacek
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Lin, Jia-Hoa
A ruthenium-based biomimetic hydrogen cluster, [Ru-2(CO)(6)(-SCH2CH2CH2S)] (1), has been synthesized and, in the presence of the P ligand tri(o-tolyl)phosphine, demonstrated efficient photocatalytic hydrogen generation from formic acid decomposition. Turnover frequencies (TOFs) of 5500h(-1) and turnover numbers (TONs) over 24700 were obtained with less than 50ppm of the catalyst, thus representing the highest TOFs for ruthenium complexes as well as the best efficiency for photocatalytic hydrogen production from formic acid. Moreover, 1 showed high stability with no significant degradation of the photocatalyst observed after prolonged photoirradiation at 90 degrees C.
Theory-Guided Experiments on the Mechanistic Elucidation of the Reduction of Dinuclear Zinc, Manganese, and Cadmium Complexes
(2011)
Lu, Duan-Yen
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Yu, Jen-Shiang K.
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Kuo, Ting-Shen
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Lee, Gene-Hsiang
;
Wang, Yu
Electronic Structure of Open-Shell Tetrahedral {Fe(NO)(2)}(9) Dinitrosyliron Complexes
(2014-10-20)
Liu, Kuan-Yu
;
Yu, Jen-Shiang K.
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生物科技學系
;
生物資訊及系統生物研究所
;
Department of Biological Science and Technology
High-level ab initio excited-state theory is employed to investigate the electronic structure of doublet {Fe(NO)(2)}(9) species in the ground state and compared with the results obtained by density functional theory. Both of the approaches consistently suggest that the linear NO ligands in dinitrosyliron complexes (DNICs) feature a radical character. Theoretical calculations also predict that the cyanide-supported DNIC anion of [(NC)(2)Fe(NO)(2)](-) features C-2 nu symmetry with a Fe-C-N bonding motif, and multireference theories suggest a minimal active space of CAS(9,9) to describe these {Fe(NO)(2)}(9) compounds, while larger CAS(13,13) calculations do not tend to significantly improve the geometries. Experimental vibration modes of NO ligands are also accurately assigned due to second-order n-electron valence state perturbation theory.

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