Duy Quang Dao

Explicit solvent effect on the redox thermodynamics of Fe(III)/Fe(II)–quercetin complexes in aqueous solution was investigated using a multiscale approach combining density functional theory (DFT) and molecular dynamics (MD) simulations. Complexation of quercetin with Fe was initially evaluated at the ωB97XD/def2-TZVP//def2-SVP level of theory using the implicit solvation model (SMD). The most stable 1:1 ML complex was identified as a bidentate Fe(III) complex at the O6O7 position, while the lowest-energy 1:2 ML2 complex corresponded to model C2, with approximately orthogonal quercetin ligands. Local solvent interactions were studied by adding up to 15 explicit water molecules around the quercetin–Fe solute, resulting in reduced reaction enthalpy and free energy of the clusters compared to the purely implicit model. Furthermore, the enthalpy and free energy of the reduction of Fe(III) in the presence of an ascorbate anion generally increase with the number of explicit waters. The differential solvent contribution was also examined using free energy perturbation (FEP) calculations within MD simulations. Overall, our findings underscore the role of the explicit solvation model in calculating the redox thermodynamics properties of iron couples in aqueous environments, highlight quercetin’s potential as an anti-Fenton agent, and offer valuable insights for antioxidant research, biological, and environmental applications.

Achieving high selectivity in alkyne semi-hydrogenation without relying on toxic modifiers remains a major challenge in heterogeneous catalysis. In this work, we have explored the design of a series of heteroatom-functionalized porous organic polymer (POP)-supported Pd catalysts (S-Pd-POP, O-Pd-POP, and N-Pd-POP) to systematically tune catalytic behavior for semi-hydrogenation of 2-methyl-3-butyn-2-ol (MBY) through p-d orbital hybridization. These materials were synthesized via a scalable free-radical polymerization approach followed by Pd incorporation, yielding an amorphous porous network with a distinct electronic microenvironment. Notably, S-Pd-POP contains ultrasmall and well-dispersed Pd nanoparticles (∼2.5 nm), significantly smaller than those in O-Pd-POP (∼6.5 nm) and N-Pd-POP (∼8.5 nm), leading to greater exposure of active sites. Synchrotron X-ray absorption fine structure (XAFS) analysis confirms Pd exists predominantly in a metallic state, while EXAFS results reveal a clear decrease in Pd-Pd coordination numbers from O-Pd-POP to N-Pd-POP to S-Pd-POP, consistent with progressively smaller Pd clusters. We have achieved a good catalytic activity with S-Pd-POP with 95.3% conversion and 97.2% selectivity under mild conditions (60 °C, 5 bar H2), along with a lower activation energy (24.6 kcal mol-1) than its counterparts. Comprehensive density functional theory calculations validate experimental findings, which show strong overlap between S(p) and Pd(d) orbitals near the Fermi level, indicating pronounced p-d orbital hybridization, which is further supported by significant sulfur-to-Pd electron interaction donation from natural bond orbital analysis. In contrast, nitrogen- and oxygen-based systems show much weaker electronic interactions, corroborating their hydrogenation activity data. In situ ATR-IR spectroscopy studies reveal that the reaction proceeds via weakly bound π-intermediates, which promote rapid product desorption and effectively suppress over-hydrogenation. Overall, this work highlights p-d orbital hybridization as a key factor governing catalytic selectivity and provides a practical strategy for designing efficient, modifier-free hydrogenation catalysts.

This work reports the rational design of bio-inspired metal-functionalized POPs as robust platforms for sustainable catalysis and paves the way for the development of next-generation nanozyme-mimetic materials.

L 'objectif de ce travail consiste à étudier les influences de principaux paramètres de fonctionnement sur la performance de réduction de NO par les procédés de Recombustion et de Réduction Sélective Non-Catalytique (RSNC) en utilisant respectivement le méthane (CH4) et l'ammoniac (NH3) comme agent réducteur. Les études paramétriques de réduction de NO ont été réalisées sur un réacteur de type piston à l'échelle de laboratoire. Les gaz brûlés sont analysées par un système d'analyse Infrarouge à Transformée de Fourrier (lRTF). Les principaux paramètres de fonctionnement tels que la température des fumés, le temps de passage, la concentration initiale en NO et la quantité d'agent réducteur injecté ont été systématiquement analysés en mode de Recombustion et de RSNC. En conséquence, les taux de réduction maximaux de NO prés de 90% et de 80% ont été obtenus respectivement en mode de Recombustion et de RSNC classique. Plusieurs composés chimiques tels que CH4, C2H2, C2H4, C2H6, CH3OH, C2H5OH, CO et H2 sont évalués comme additifs pour le procédé de réduction de NO par NH3. Les résultats expérimentaux obtenus en mode de Recombustion ont été comparés à ceux issus de la modélisation par le code de calcul SENKIN-CHEMKIN Il en utilisant quatre mécanismes de référence: GDF-Kin®3.0_NCN (El Bakali et col, 2006), Glarborg (Glarbarg et col, 1998), GRI3.0 (Smith et col, 1999) et Konnov (Kannov et col. 2005). Le mécanisme AA2006 de Coda Zabetta et Hupa, (2008) est modifié pour analyser l'aspect cinétique chimique d'effets des additifs sur la réduction de NO par NH3

The multifunctional properties of aaptodine A in preventing oxidative stress and inhibiting amyloid-beta (Aβ) aggregation, both of which are considered the main causes of Alzheimer's disease (AD), are the focus of this study. Using the M06-2X and M06 density functional theory (DFT) methods, the study examines the scavenging of HO^· and HOO^· radicals, as well as the reactions involving Fe³⁺/Cu²⁺ chelation. Docking and molecular dynamics (MD) simulations further assess the inhibitory effect of aaptodine A on Aβ aggregation. The findings indicate that aaptodine A exhibits a strong ability to scavenge the HO^· radical (rate constant k = 1.69 × 10¹⁰ M^-1 s^-1); however, it is ineffective against the HOO^· radical. Furthermore, aaptodine A demonstrates significant chelating activity with Cu²⁺, particularly showing effective scavenging ability for both Cu²⁺ and Fe³⁺ ions when the complex formation occurs with two ligands. These bioactivities help suppress the formation of reactive free radicals, often associated with metal ions, and mitigate Cu²⁺-induced neurotoxicity linked to Aβ in AD. Additionally, analyses using MM/PBSA and the accelerated weight histogram (AWH) methods reveal that aaptodine A exhibits a strong binding affinity to Aβ42 fibril structures. Its binding affinities are comparable to those of curcumin, a well-known compound recognized for its ability to inhibit the formation of Aβ fibrils and oligomers. The AWH results with tetramer indicate that aaptodine A binds to both toxic oligomeric species and the mature fibril. As a result, aaptodine A exhibits potential antioxidant activity through a secondary mechanism and may serve as a promising candidate for inhibiting toxic Aβ aggregates associated with AD.

The development of efficient and sustainable heterogeneous catalysts remains central to the advancement of green oxidation chemistry. Herein, we report a Ni-salphen-derived metalated porous organic polymer (Ni@CAB), synthesized via a simple Friedel-Crafts alkylation strategy that integrates atomically dispersed Ni-N₂O₂ active sites into a robust carbazole-linked framework. A combination of 2D solid-state ¹³C-¹H double cross-polarization (CP) correlation NMR, XPS, synchrotron-based XAS, and electron microscopy techniques confirmed the structural integrity, amorphous porous architecture, and uniform dispersion of Ni centers. Electronic analyses revealed reduced surface electron density at the Ni sites, enhancing their Lewis acidity and catalytic reactivity. Ni@CAB demonstrated exceptional performance in the aerobic allylic oxidation of cyclohexene under ambient conditions, affording complete conversion with high selectivity and remarkable recyclability over multiple cycles without detectable Ni leaching. Complementary DFT calculations unveiled favorable charge transfer and energetically viable pathways consistent with experimental observations. This study establishes surface electron density as a powerful activity descriptor and underscores the promise of rationally engineered metalated porous polymers for sustainable oxidation catalysis.

The enzyme inhibitory activities of a dataset of 28 aaptamines are performed to identify potential multifunctional drugs for neurodegenerative diseases (NDs). First, the drug-like properties and pharmacokinetic (ADMET) study excluded seven molecules, mostly for the non-permeability of the blood–brain barrier. The binding activities of the remaining 21 candidates towards acetylcholinesterase (AChE), monoamine oxidase B (MAOB) and catechol-O-methyltransferase (COMT) enzymes are initially screened by molecular docking. The top binding complexes ( A12 @MAOB, A24 @COMT and A27 @AChE) are simultaneously studied by molecular dynamics in water for 500 ns time-scale and compared with the references such as safinamide (SAG), tolcapone (TOL) or donepezil (DON). The results show that two aaptamines A12 and A27 are well-positioned within the active pocket of the enzymes, exhibiting structural stability, with a root mean square deviation of about 0.15–0.2 nm. MM-PBSA calculation indicates that the binding energy of the ligands to the corresponding targets is equal to ( A12 versus SAG) or much lower than the references ( A24 versus TOL and A27 versus DON). The van der Waals interactions contribute more strongly to enzyme binding than the electrostatic energy. The study results suggest that A27 (lowest binding energy, −170.42 ± 14.24 kJ mol ⁻¹ ) is the most prominent aaptamine candidate for the treatment of NDs.

Curcumin possesses various effective medicinal properties, such as anti-cancer, anti-Alzheimer's, anti-inflammatory, and antioxidant effects, where its free radical scavenging activities play a crucial role in its therapeutic mechanisms. Although the antioxidant properties of curcumin and its derivatives have been previously studied, a systematic investigation of the thermodynamics and kinetics of the reaction with the hydroperoxide radical (HOO˙) – a standardized free radical – in different solvents is lacking. This study examined the HOO˙ radical scavenging activities of two curcumin derivatives, specifically curcumin I (Cur-I) and curcumin III (Cur-III), in water and pentyl ethanoate (PEA) solutions using Density Functional Theory (DFT) approaches. The antioxidant properties of the neutral and anionic forms of their tautomers, including the keto–enol and diketone forms, were explored via three standard mechanisms: hydrogen abstraction (Abs), radical addition (Add), and single electron transfer (SET). Intrinsic parameters, thermochemical parameters, and kinetics of the curcumin-HOO˙ reactions were systematically characterized. As a result, the overall rate constant for the reaction of Cur-I in the water (9.36 × 10⁷ M⁻¹ s⁻¹) is approximately 3.6 times higher than that of Cur-III (2.60 × 10⁷ M⁻¹ s⁻¹). Meanwhile, the rate constants in PEA solvent are less significant, being 4.02 × 10¹ M⁻¹ s⁻¹ and 8.16 × 10² M⁻¹ s⁻¹ for Cur-I and Cur-III, respectively. Due to the dominant molar fraction of the keto–enol form compared to the diketone, the reaction rates are primarily attributed to the keto–enol form. The SET reaction of dianionic form contributes a decisive proportion to the overall rate constants of both Cur-I and Cur-III. Finally, an analysis of the chemical nature of the Abs reactions reveals that the most predominant hydrogen transfer at the phenolic –OH groups (i.e., O22H and O23H) occurs via a proton-coupled electron transfer (PCET) mechanism.