Solving the electron and electron-nuclear Schrodinger equations for the excited states of helium atom with the free iterative-complement-interaction method

Very accurate variational calculations with the free iterative-complement-interaction (ICI) method for solving the Schrödinger equation were performed for the 1sNs singlet and triplet excited states of helium atom up to N=24. This is the first extensive applications of the free ICI method to the calculations of excited states to very high levels. We performed the calculations with the fixed-nucleus Hamiltonian and moving-nucleus Hamiltonian. The latter case is the Schrödinger equation for the electron-nuclear Hamiltonian and includes the quantum effect of nuclear motion. This solution corresponds to the nonrelativistic limit and reproduced the experimental values up to five decimal figures. The small differences from the experimental values are not at all the theoretical errors but represent the physical effects that are not included in the present calculations, such as relativistic effect, quantum electrodynamic effect, and even the experimental errors. The present calculations constitute a small step toward the accurately predictive quantum chemistry

NMR spectrum prediction for dynamic molecules by machine learning: A case study of trefoil knot molecule

Nuclear magnetic resonance (NMR) spectroscopy is one of the indispensable techniques in chemistry because it enables us to obtain accurate information on the chemical, electronic, and dynamic properties of molecules. Computational simulation of the NMR spectra requires time-consuming density functional theory (DFT) calculations for an ensemble of molecular conformations. For large flexible molecules, it is considered too high-cost since it requires time-averaging of the instantaneous chemical shifts of each nuclear spin across the conformational space of molecules for NMR timescales. Here, we present a Gaussian process/deep kernel learning-based machine learning (ML) method for enabling us to predict, average in time, and analyze the instantaneous chemical shifts of conformations in the molecular dynamics trajectory. We demonstrate the use of the method by computing the averaged H-1 and C-13 chemical shifts of each nuclear spin of a trefoil knot molecule consisting of 24 para-connected benzene rings (240 atoms). By training ML model with the chemical shift data obtained from DFT calculations, we predicted chemical shifts for each conformation during dynamics. We were able to observe the merging of the time-averaged chemical shifts of each nuclear spin in a singlet H-1 NMR peak and two C-13 NMR peaks for the knot molecule, in agreement with experimental measurements. The unique feature of the presented method is the use of the learned low-dimensional deep kernel representation of local spin environments for comparing and analyzing the local chemical environment histories of spins during dynamics. It allowed us to identify two groups of protons in the knot molecule, which implies that the observed singlet H-1 NMR peak could be composed of the contributions from protons with two distinct local chemical environments

Investigation of post-grafted groups of a porous coordination polymer and its proton conduction behavior.

We investigated the configuration of substituent groups that are post-synthetically bound to the pore surface in a porous coordination polymer. This study demonstrates the observations of orientation and coordination fashions of the grafted groups, which contribute towards improved proton conductivity in porous frameworks

Solving the electron and electron-nuclear Schrodinger equations for the excited states of helium atom with the free iterative-complement-interaction method

Very accurate variational calculations with the free iterative-complement-interaction (ICI) method for solving the Schrödinger equation were performed for the 1sNs singlet and triplet excited states of helium atom up to N=24. This is the first extensive applications of the free ICI method to the calculations of excited states to very high levels. We performed the calculations with the fixed-nucleus Hamiltonian and moving-nucleus Hamiltonian. The latter case is the Schrödinger equation for the electron-nuclear Hamiltonian and includes the quantum effect of nuclear motion. This solution corresponds to the nonrelativistic limit and reproduced the experimental values up to five decimal figures. The small differences from the experimental values are not at all the theoretical errors but represent the physical effects that are not included in the present calculations, such as relativistic effect, quantum electrodynamic effect, and even the experimental errors. The present calculations constitute a small step toward the accurately predictive quantum chemistry

Strain-Induced Ring Expansion Reactions of Calix[3]pyrrole-Related Macrocycles

The recent discovery of calix[3]pyrrole, a porphyrinogen-like tripyrrolic macrocycle, has provided an unprecedented strain-induced ring expansion reaction into calix[6]pyrrole. Here, we synthesized calix[n]furan[3-n]pyrrole (n=1 similar to 3) macrocycles to investigate the reaction scope and mechanism of the ring expansion. Single crystal X-ray analysis and theoretical calculations revealed that macrocyclic ring strain increases as the number of inner NH sites increases. While calix[1]furan[2]pyrrole exhibited almost quantitative conversion into calix[2]furan[4]pyrrole within 5 minutes, less-strained calix[2]furan[1]pyrrole and calix[3]furan were inert. However, N-methylation of calix[2]furan[1]pyrrole induced a ring-expansion reaction that enabled the isolation of a linear reaction intermediate. The mechanism analysis revealed that the ring expansion consists of regioselective ring cleavage and subsequent cyclodimerization. This reaction was further utilized for synthesis of calix[6]-type macrocycles

Multicolour photochromic fluorescence of a fluorophore encapsulated in a metal-organic framework

A fluorophore encapsulated in a metal-organic framework showed photochromic multicolour fluorescence. Irradiation with an ultraviolet laser induced the relocation of the fluorophore from a polar to a nonpolar environment, altering the emission from red to blue. This change in emission color can be repeatably recovered by heating the fluorophore-MOF composite

Siloxane D4 capture by hydrophobic microporous materials

Porous substances, including crystalline coordination materials and an amorphous organic polymer, were studied for their selective adsorption of siloxane D4. The investigated materials demonstrated a level of uptake comparable to that of conventional activated carbon

Ligand-based solid solution approach to stabilisation of sulphonic acid groups in porous coordination polymer Zr_{6}O_{4}(OH)_{4}(BDC)_{6} (UiO-66).

By adopting a ligand-based solid solution approach, the sulphonic acid functional group can be successfully incorporated into a porous coordination polymer with UiO-66 structure type. Zr_{6}O_{4}(OH)_{4}(BDC-SO_{3}H)_{1.1}(BDC)_{4.9} possesses enhanced heat of adsorption for carbon dioxide and acetone compared to Zr_{6}O_{4}(OH)_{4}(BDC)_{6}