Physical Chemistry Chemical Physics最新文献

The electronic transport properties of molecular junctions based on four boron clusters, B₃₂, B₃₉, B₄₂, and B₄₅, that have tubular ground state structures were studied using first principles calculations and non-equilibrium Green's function simulations. Spin polarized calculations indicate that the charge transport properties are almost spin-independent at low bias voltages. In fact, only the junction based on B₃₉ exhibits the spin polarization effect, while the other open-shell cluster (B₄₅) shows no spin dependence due to its coupling with the electrodes. The calculated current-voltage characteristics show that the four types of molecular junctions have diverse functionalities, with the B₃₂ and B₃₉ junctions exhibiting current limiting features, while a clear negative differential resistance effect was found in the B₄₂ and B₄₅ junctions. These results suggest that molecular junctions based on boron clusters, which support rich geometrical and electronic properties, could serve as an important group of candidates for constructing functional molecular devices.

Excited-state intramolecular proton transfer (ESIPT) is a fundamental photochemical process in which photoexcitation induces proton transfer within a molecule, leading to the formation of a tautomeric excited state. It was observed experimentally that the 3-hydroxychromone (3-HC) system exhibits two distinct proton-transfer time scales upon excitation to the lowest bright singlet excited state: an ultrafast component on the femtosecond time scale and a slower one on the picosecond time scale, largely insensitive to solvent effects. Up to now, the microscopic origin of the second time constant has only been hypothesised. Here, using mixed quantum-classical non-adiabatic dynamics simulations, we explicitly observe the two ESIPT time constants and we rationalise the origin of the second time scale by the presence of a competitive out-of-plane hydrogen torsional motion. Comprehensive analysis of the excited-state potential energy surfaces and non-adiabatic trajectories enables us to construct an explicit reaction network for 3-HC, delineating the interplay between direct ESIPT and torsion-mediated pathways. This unified mechanistic framework reconciles the coexistence of ultrafast and slower ESIPT components, offering new insights into the non-adiabatic excited-state dynamics of the system.

In this work, the reaction mechanism of crotonaldehyde (CRAL) hydrogenation to crotyl alcohol (CROL) over graphitic carbon nitride (g-CN) supported TM-Ru diatomic catalysts with hydrazine as a hydrogen source was systematically studied by using density functional theory (DFT) calculations. The computational results show that hydrazine can achieve efficient hydrogen transfer at TM-Ru dual sites through a cooperative six-membered-ring transition state, with the energy barrier of the rate-determining step being only 1.15-1.21 eV, which is significantly lower than that of organic hydrogen sources such as ethanol and isopropanol (1.70-2.92 eV). Further side-reaction analysis reveals that only Sc-Ru and Ti-Ru can effectively suppress competing reactions such as deoxygenation, decarbonylation, and enolization, thereby achieving optimal selectivity. Electronic structure studies indicate that the d-band center of the metal sites exhibits a good linear correlation with the energy barrier of the rate-determining step of hydrogen transfer, and can serve as a key electronic descriptor for tuning hydrogenation selectivity. A dual-atom catalyst design principle is proposed with the d-band center as the core descriptor, providing a theoretical basis and general mechanistic insights for hydrogen source optimization and the rational design of efficient dual-site catalysts in hydrogen-transfer hydrogenation processes.

A recent article in this journal (F. Parisi et al., Phys. Chem. Chem. Phys., 2024, 26, 28037-28045) misassigned the infrared spectrum of liquid diethylmethylammonium triflate (DEMA TfO), a room-temperature ionic liquid. Results from a fresh simulation similar to theirs are shown here, to explain the error and probe the related question of the degree of hydrogen bonding (there does appear to be some). The two peaks in the NH stretch region are due to intensity borrowing (Fermi resonance) from the one NH stretch fundamental by overtone or combination state(s) involving the NH bend.

Joo and East have recently published a Comment on our article (F. Parisi et al., Phys. Chem. Chem. Phys., 2024, 26, 28037, https://doi.org/10.1039/D3CP06047K). The Comment is based on the wrong assumption that we misassigned the infrared spectrum of liquid diethylmethylammonium triflate [DEMA][TfO]. The authors incorrectly claim that our hypothesis was that the two bands are due to the NH stretch mode in two different ion-pair structural types. We clarify here that our original analysis did not invoke two separate, static ion-pair structures, but rather a continuum of dynamically evolving hydrogen-bonding environments that naturally produce a broadened, bimodal band shape. The results presented in our paper are aligned with the ones presented in the Comment. The Comment brings up the concept of Fermi resonance, which indeed gives a plausible explanation of the features seen in the experimental absorption spectra.

Piezocatalysis is a promising method for generating green hydrogen peroxide (H₂O₂), however, improving the surface charge transfer kinetics remains challenging. In this study, we develop tetragonal barium titanate (BTO) nanoparticles modified with surface-anchored rhodium single-atom (RhSA) cocatalysts. Detailed structural characterization confirmed that the Rh species are atomically dispersed as Rh³⁺ coordinated with surface oxygen of BTO without forming clusters or being incorporated into the BTO lattice. Piezoresponse force microscopy revealed that RhSA does not affect the intrinsic piezoelectric polarization of the BTO. However, the BTO-RhSA catalyst produced 1.5 times more H₂O₂ than pristine BTO did under ultrasonic excitation. Mechanistic studies using (piezo)electrochemical measurements demonstrated that unlike conventional noble metal cocatalysts, which typically enhance the reduction kinetics, the RhSA sites on BTO do not promote the oxygen reduction reaction (ORR). Instead, they significantly accelerate the oxidation of isopropanol as a sacrificial reagent by efficiently utilizing the piezo-generated positive charges. This work establishes a surface-engineering strategy in which isolated atomic sites selectively boost positive charge-driven reactions, enabling the independent control of reduction and oxidation pathways and providing new design principles for high-performance piezocatalytic systems.