Rolling two-dimensional covalent organic framework (COF) sheets into one-dimensional electronic and proton-conductive nanotubes.

Mimicking the interconvertible carbon allotropes of 2-dimensional (2D) graphene and 1-dimensional (1D) carbon nanotubes (CNTs), herein we report the in situ transformation of 2D π-conjugated covalent organic frameworks (COFs) sheet into 1D nanotubular structures via self-assembly the sheets at solvent interfaces. The facile "roll-sheets" self-assembly resulted in coaxial nanotubes with uniform cross-sectional diameter, which was realized for diazapyrene-based COFs but not for the corresponding pyrene COF, although both possess similar chemical structures. Upon replacing the carbon atoms at 2,7-positions of pyrene with nitrogen, contrasting optical and electronic properties were realized, reflecting the rolled structure of the conjugated 2D sheets.

A theoretical study of the molecular passivation of p-/n-type defects on tin- and germanium-mixed perovskite surfaces using Lewis base/acid.

Perovskite solar cells have been attracting considerable attention because of their high power conversion efficiency (PCE). However, their efficiency is compromised by the defect sites on the perovskite surfaces, where charge carriers (excitons) are trapped and recombined. In this study, based on the density functional theory method, we theoretically explore a molecular passivation process for coating a perovskite surface to reduce the defect concentration.

Inclusion of gold ions in tiara-like nickel hexanuclear nanoclusters.

Tiara-like metal nanoclusters (TNCs) composed of group 10 transition metals and thiolates can easily change their number of polymerization and include various molecules or metal ions as guests within their ring structures. Therefore, they are expected to be applied in sensing, storage, and catalyst materials based on their selective inclusion characteristics. However, there are very few reports regarding the principles of selective inclusion for guest molecules/ions in TNCs.

Theoretical and machine learning models for reaction-barrier predictions: acrylate and methacrylate radical reactions.

We propose density functional theory (DFT)- and random forest (RF)-based theoretical and machine learning (ML) models, respectively, for predicting reaction barriers (Δ) using acrylate and methacrylate radical reactions as representatives. DFT is used to determine 100 transition state (TS) structures of both radicals, after which the obtained data are used to determine theoretical relationships (explained with Bell-Evans-Polanyi or Brønsted-Evans-Polanyi (BEP) and Marcus-like models) between Δ and stabilization energy of the product. Next, we construct several theoretical regression models for predicting Δ of the representative reactions based on our theoretical analyses, presenting an RF-based ML model that eases Δ predictions by circumventing time-consuming DFT calculations.

Efficient quantum mechanical minimum free energy path calculation by combining path integral hybrid Monte Carlo and climbing image nudged elastic band methods, and its application to the addition reaction of hydrogen isocyanide to formaldehyde.

We propose an efficient algorithm for a minimum free energy path calculation based on the path integral hybrid Monte Carlo (PIHMC) method by combining the climbing image-nudged elastic band (CI-NEB) and the thermodynamic integration (TI) methods. Here, the CI-NEB and the TI methods are used to find a transition state along the reaction path and evaluate the free energy path, respectively. Our algorithm is applied to the Walden inversion reaction of the hydronium ions (H3O+).

Ultrafine Spatial Modulation of Diazapyrene-Based Two-Dimensional Conjugated Covalent Organic Frameworks.

Tailormade bottom-up synthesis of covalent organic frameworks (COFs) from various functional building blocks offer not only tunable topology and pore size but also multidimensional properties. High crystallinity is one of the prerequisites for their structures and associated physicochemical properties. Among different π-conjugated motifs for constructing COFs, pyrene-based tetragonal structures are effective in achieving highly ordered and crystalline states.

Theoretical Study of the Molecular Passivation Effect of Lewis Base/Acid on Lead-Free Tin Perovskite Surface Defects.

Extensive research has been recently conducted to improve the power conversion efficiency (PCE) of perovskite solar cells. However, the charge carriers are easily trapped by the defect sites located at the interface between the perovskite layer and the electrode, which decreases the PCE. To reduce such defect sites, the passivation technique is frequently employed to coat small molecules on the perovskite surface during the manufacturing process.

Improved activity for the oxygen evolution reaction using a tiara-like thiolate-protected nickel nanocluster.

Practical electrochemical water splitting and carbon-dioxide reduction are desirable for a sustainable energy society. In particular, facilitating the oxygen evolution reaction (OER, the reaction at the anode) will increase the efficiency of these reactions. Nickel (Ni) compounds are excellent OER catalysts under basic conditions, and atomically precise Ni clusters have been actively studied to understand their complex reaction mechanisms.

Fullerene C/porphyrin hybrid nanoarchitectures: single-cocrystal nanoribbons with ambipolar charge transport properties.

In recent years, supramolecular cocrystals containing organic donors and acceptors have been explored as active components in organic field-effect transistors (FETs). Herein, we report the synthesis of novel single-cocrystal nanoribbons with ambipolar charge transport characteristics from C and 5,10,15,20-tetrakis(3,5-dimethoxyphenyl)porphyrin (3,5-TPP) in a 3 : 2 ratio. The C/3,5-TPP nanoribbons exhibited a new strong absorption band in the near-infrared region, indicating the presence of charge-transfer interactions between C and 3,5-TPP in the cocrystals.

Global Search for Crystal Structures of Carbon under High Pressure.

In this study, a systematic search for structures of carbon crystals under high pressure was performed by using the artificial force induced reaction method including periodic boundary conditions. To perform a search under an arbitrary pressure, an algorithm to take account of the pressure was implemented in the GRRM program. At 100 GPa, the search generated 710 unique structures automatically.

Computational searches for crystal structures of dioxides of group 14 elements (CO, SiO, GeO) under ultrahigh pressure.

In this study, we focused on the effect of pressure on the crystal structures of dioxides of group 14 elements, SiO, GeO, and CO. Systematic searches for their crystal structures using the artificial force induced reaction method generated 219 and 147, 102 and 63, and 148 and 76 structures for SiO, GeO, and CO, respectively, at 1 and 10 atm. At 1 atm, cristobalite-like, quartz, anatase-like, and stishovite were stable structures for SiO and GeO.

One-Dimensional Fullerene/Porphyrin Cocrystals: Near-Infrared Light Sensing through Component Interactions.

Recently, organic donor-acceptor (D-A) cocrystals have attracted special interest as functional materials because of their unique chemical and physical properties that are not exhibited by simple mixtures of their components. Herein, we report the preparation of one-dimensional novel D-A cocrystals from C and 5,10,15,20-tetrakis(3,5-dimethoxyphenyl)porphyrin (3,5-TPP); these cocrystals have near-infrared (NIR) light-sensing abilities, despite each of their component molecule individually having no NIR light-sensing properties. Micrometer-sized rectangular columnar C-3,5-TPP cocrystals were produced by a simple liquid-liquid interfacial precipitation method.

Understanding CO oxidation on the Pt(111) surface based on a reaction route network.

Analysis of a reaction on a solid surface is an important task for understanding the catalytic reaction mechanism. In this study, we studied CO oxidation on the Pt(111) surface by using the artificial force induced reaction (AFIR) method. A systematic reaction path search was done, and the reaction route network was created.

Combined Automated Reaction Pathway Searches and Sparse Modeling Analysis for Catalytic Properties of Lowest Energy Twins of Cu.

In nanocatalysis, growing attention has recently been given to investigation of energetically low-lying structural isomers of atomic clusters, because some isomers can demonstrate better catalytic activity than the most stable structures. In this study, we present a comparative investigation of catalytic activity for NO dissociation of a pair of the energetically degenerated isomers of Cu cluster having C and C symmetries. It is shown that although these isomers have similar structural, electronic, and optical properties, they can possess very different catalytic activities.

Exploring potential crossing seams in periodic systems: Intersystem crossing pathways in the benzene crystal.

The intersystem crossing (ISC) pathways of triplet benzene molecules in a benzene crystal were investigated theoretically. A combination of the gradient projection (GP) method, which is a standard method for optimizing the crossing seam of two potential energy surfaces, and the single-component artificial-force-induced reaction (SC-AFIR) method (GP/SC-AFIR) was used. This is the first reported use of a GP/SC-AFIR calculation using a density functional theory calculation with periodic boundary conditions.

Implementation and performance of the artificial force induced reaction method in the GRRM17 program.

This article reports implementation and performance of the artificial force induced reaction (AFIR) method in the upcoming 2017 version of GRRM program (GRRM17). The AFIR method, which is one of automated reaction path search methods, induces geometrical deformations in a system by pushing or pulling fragments defined in the system by an artificial force. In GRRM17, three different algorithms, that is, multicomponent algorithm (MC-AFIR), single-component algorithm (SC-AFIR), and double-sphere algorithm (DS-AFIR), are available, where the MC-AFIR was the only algorithm which has been available in the previous 2014 version.

Artificial Force Induced Reaction (AFIR) Method for Exploring Quantum Chemical Potential Energy Surfaces.

In this account, a technical overview of the artificial force induced reaction (AFIR) method is presented. The AFIR method is one of the automated reaction-path search methods developed by the authors, and has been applied extensively to a variety of chemical reactions, such as organocatalysis, organometallic catalysis, and photoreactions. There are two modes in the AFIR method, i.