Journal of Computational Chemistry最新文献

Macrocyclic receptors play a crucial role in supramolecular chemistry, enabling the selective binding of guest molecules through non-covalent interactions. This study investigates the anion binding properties of three shape-persistent macrocycles, triazolophane, cyanostar, and tricarb, each featuring preorganized cavities with polarized CH hydrogen bond donors. In the 1:1 binding stoichiometries, the macrocycles preferentially bind anions that fit inside their two-dimensional cavities, with this preference being more pronounced in solution. Specifically, the triazolophane favors smaller anions like chloride and bromide, while the larger cavities offered by cyanostar and tricarb macrocycles preferentially bind the larger iodide. For large, polyatomic anions (SCN⁻, BF₄⁻, ClO₄⁻, and PF₆⁻), the macrocycles self-assemble to form stable 2:1 sandwich complexes, exhibiting stronger binding. This shift in selectivity highlights the versatility of the macrocycles, making them promising candidates for anion sensing and regulation with various complexation stoichiometries.

Rice–Ramsperger–Kassel–Marcus (RRKM) theory was implemented in Eyringpy to enable the computation of microcanonical rate constants, densities of states (DOS), and sums of states. Input can be provided either as experimental data or directly from electronic-structure output files, requiring minimal user specification. The Stein–Rabinovitch algorithm was employed for accurate state counting, and tunneling corrections were introduced through the Eckart model to account for light-particle transfer and narrow barriers. To validate the implementation, the DOS of hydrogen peroxide was evaluated with anharmonic-vibrational corrections, and three gas-phase reactions were analyzed: thermal decomposition of digermane, bromine-atom loss from CH₂BrO·, and hydrofluoric-acid elimination from CF₃CH₃. The validation confirms that Eyringpy provides accurate and efficient RRKM calculations, providing reliable kinetic analyses of unimolecular reactions across a broad energy range.

Molecules characterized by an inverted singlet-triplet gap () hold potential for optoelectronic applications. Electronic correlation and environmental polarization are key factors influencing negative $��\Delta �E_{\mathrm{ST}}�$, and the latter is gaining attention for its possible role in “mimicking” correlation contributions to yield negative $��\Delta �E_{\mathrm{ST}}�$. However, a comprehensive study of solvation effects on both structures and energy gaps is still lacking. In this work, we evaluate computational strategies for calculating gaps, incorporating electronic correlation and solvent polarization in molecules exhibiting singlet-triplet inversion. Using RMS–CASPT2 as a benchmark, we demonstrate that double-hybrid density functionals and mixed-reference spin-flip TD-DFT (MRSF–TD-DFT) can partially recover electronic correlation. Furthermore, we investigate solvation effects on both singlet and triplet excited states, highlighting the limitations of linear-response schemes in continuum solvation models. We finally develop a protocol combining electronic correlation and state-specific solvent polarization using double-hybrid functionals and the Vertical Excitation Model (VEM), leveraging its Lagrangian implementation to compute structures and adiabatic energies. Applying our B2PLYP/VEM(UD) protocol to larger systems with experimentally observed negative

Enhanced sampling methods have become powerful techniques to investigate complex systems and rare molecular events by facilitating greater access to configurational space. In parallel, the continuous development of polarizable force fields augments such techniques, allowing the investigation of the role of electronic polarization in transitional barriers that might be overlooked in nonpolarizable simulations. Together, improved sampling methods and polarizable force fields should accelerate computational discoveries. Here, we present an implementation of a weighted ensemble strategy for the Drude polarizable force field using the WESTPA software package in conjunction with the OpenMM simulation engine. We demonstrate its use for backbone conformational sampling in a model system (alanine dipeptide) and in studying functional sidechain rotations in an enzyme (Abl1 kinase). We further discuss possible consequences related to the inclusion of explicit electronic polarization in the model. This software implementation and validation should facilitate the use of WESTPA-Drude strategies throughout the simulation community.

We performed a hierarchical, convergent ab initio benchmark study and systematically analyzed the performance of density functional approximations for describing hydrogen bonds in small neutral, cationic, and anionic complexes, as well as in larger systems involving amide, urea, deltamide, and squaramide moieties. Focal point analyses (FPA), extrapolating to the ab initio limit, were carried out using correlated wave function methods up to CCSDT(Q) for the small complexes and CCSD(T) for the larger systems, together with correlation-consistent Gaussian basis sets up to the complete basis set limit. Optimized geometries and vibrational frequencies were obtained at the CCSD(T) level. The resulting FPA hydrogen-bond energies converge within a few tenths of a kcal mol⁻¹. These reference data were used to evaluate 60 density functionals (including 12 dispersion-corrected), spanning the local-density approximation (LDA), generalized gradient approximations (GGAs), meta-GGAs, hybrids, meta-hybrids, double-hybrids, and range-separated hybrids. Overall, the meta-hybrid M06-2X provides the best performance for both hydrogen bond energies and geometries, while the dispersion-corrected GGAs BLYP-D3(BJ) and BLYP-D4 also yield accurate hydrogen-bond data and can serve as cost-effective options for studying large and complex systems.