Masaaki Akamatsu, Koji Yamanaga, Kohei Tanaka, Yurina Kanehara, Masato Sumita, Kenichi Sakai, Hideki Sakai "Anion–π Interactions in Monolayers Formed by Amphiphilic Electron-Deficient Aromatic Compounds at the Air/Water Interfaces",
Langmuir, 39, 5833-5839 (2023).
Biological systems precisely and selectively control ion binding through various chemical reactions, molecular recognition, and transport by virtue of effective molecular interactions with biological membranes and proteins. Because ion binding is inhibited in highly polar media, recognition systems for anions in aqueous media, which are relevant to biological and environmental systems, are still limited. In this study, we explored the anion binding of Langmuir monolayers formed by amphiphilic naphthalenediimide (NDI) derivatives with a series of substituents at air/water interfaces via anion-π interactions. Density functional theory (DFT) simulations revealed that the binding of anions originating from anion-π interactions is related to the electron density of the anions. At the air/water interfaces, amphiphilic NDI derivatives formed Langmuir monolayers, and the addition of anions caused expansion of the Langmuir monolayers. The anions with larger hydration energies related to electron density showed larger binding constants (Ka) for 1:1 stoichiometry with the NDI derivatives. The loosely packed monolayer formed by the amphiphilic NDI derivatives with bromine groups showed a better anion response. In contrast, the binding of NO3− was significantly enhanced in the highly packed monolayer. These results indicate that the packing of NDI derivatives with rigid aromatic rings influenced the binding of the anions. These results provide insight into ion binding using the air/water interface as a promising recognition site for mimicking biological membranes. In future, sensing devices can be developed using Langmuir-Blodgett films on electrodes. Furthermore, the capture of anions on electron-deficient aromatic compounds can lead to doping or composition technologies for n-type semiconductors.
Mandeep K. Chahal, Masato Sumita, Jan Labuta, Daniel T. Payne, Jonathan P. Hill, Yusuke Yamauchi, Takashi Nakanishi, Takeshi Tanaka, Hiromichi Kataura, Kenji Koga, Hiroyuki Miyamura, Yoshihiro Kon, Dachao Hong, and Shinsuke Ishihara "Selective Detection of Toxic C1 Chemicals Using Hydroxylamine-based Chemiresistive Sensor Array",
ACS Sens., 8, 1585-1592 (2023).
Formaldehyde (FA) is a deleterious C1 pollutant commonly found in the interiors of modern buildings. C1 chemicals are generally more toxic than the corresponding C2 chemicals, but the selective discrimination of C1 and C2 chemicals using simple sensory systems is usually challenging. Here, we report the selective detection of FA vapor using a chemiresistive sensor array composed of modified hydroxylamine salts (MHAs, ArCH2ONH2·HCl) and single-walled carbon nanotubes (SWCNT). By screening 32 types of MHAs, we have identified an ideal sensor array that exhibits a characteristic response pattern for FA. Thus, trace FA (0.02-0.05 ppm in air) can be clearly discriminated from the corresponding C2 chemical, acetaldehyde (AA). This system has been extended to discriminate methanol (C1) from ethanol (C2) in combination with the catalytic conversion of these alcohols to their corresponding aldehydes. Our system offers portable and reliable chemical sensors that discriminate the subtle differences between C1 and C2 chemicals, enabling advanced environmental monitoring and healthcare applications.
Naruki Yoshiwakawa, Masato Sumita "Automatic Differentiation for the Direct Minimization Approach to the Hartree-Fock Method",
J. Phys. Chem. A , 126, 8487-8493 (2022).
Automatic differentiation (AD) has become an important tool for optimization problems in computational science, and it has been applied to the Hartree-Fock method. Although the reverse-mode AD is more efficient than the forward-mode, eigenvalue calculation in the self-consistent field (SCF) method has impeded the use of the reverse-mode AD. Here, we propose a method to directly minimize Hartree-Fock energy under the orthonormality constraint of the molecular orbitals using reverse-mode AD by avoiding eigenvalue calculation. According to our validation, the proposed method was more stable than the conventional SCF method and achieved comparable accuracy.
Masato Sumita, Naruki Yoshiwakawa "Augmented Lagrangian method for spin-coupled wave function",
Int. J. Quantum Chem. , 121, e26746 (2021).
We applied augmented Lagrangian method coupled with derivative-free methods to optimize molecular wave function based on non-orthogonal orbitals, that is called spin-coupled generalized valence bond (SCGVB), for its ground-state energy. In contrast to the orthogonal-orbital-based electronic structure theory, the SCGVB includes spin eigenfunctions to satisfy the eigenstates as the operator of the square of the spin. To obtain the ground-state energy of SCGVB, therefore, it is necessary to optimize the orbital and the spin-coupling coefficients simultaneously. In this study, we validated feasibility of the derivative-free augmented Lagrangian method for optimizing the spin-coupling and the orbital coefficients with the constraint of normality of the wave function. We employed this SCGVB method to compute dissociative potential energy curves (PECs) of H2, H2-, He2+, and LiH. The obtained PECs by the SCGVB method are close to these by full configuration interaction theory. These results indicate that the augmented Lagrangian method is effective to optimize the wave function of SCGVB.
Kazuyoshi Takimoto, Shinsuke Ishihara, Jan Labuta, Vaclav Brezina, Daniel Tony Payne, Jonathan P Hill, Katsuhiko Ariga, Masato Sumita, Shigeki Mori, and Hisako Sato "Enantiomeric Excess Dependent Splitting of NMR Signal Through Dynamic Chiral Inversion and Co-Ligand Exchange in a Coordination Complex",
J. Phys. Chem. Lett. , 11, 8164-8169 (2020).
NMR spectroscopy cannot be used to discriminate enantiomers, and NMR resonances of enantiomeric mixtures are generally not affected by enantiomeric excess (ee). Here we report that a coordination complex (L · 2Zn · 3C), where L is a salen-like prochiral ligand and C is an exchangeable acetate co-ligand, exhibits symmetrical splitting of one of the 1H-NMR resonances of L with the degree of splitting linearly proportional to ee of the chiral guest co-ligand C, 2-phenoxypropionic acid (PPA). Despite the well-defined chirality in the crystal structure of L · 2Zn · 3C, concurrent fast chiral inversion and co-ligand exchange in solution renders L · 2Zn · 3C the primary example of prochiral solvating agent (pro-CSA) based on a coordination complex. Notably, the NMR resonances remain split even in dilute solution due to the lack of chiral guest dissociation in the co-ligand exchange system. This work provides new insights into chiral transfer events in metal-ligand complexes.
Qin TANG, Shufang ZHANG, Xinbang LIU, Masato SUMITA, Shinsuke ISHIHARA, Harald FUCHS, Qingmin JI, Lock Kumar SHRESTHA, Katsuhiko ARIGA, "Manipulation of fullerene superstructures by complexing with polycyclic aromatic compounds",
Phys. Chem. Chem. Phys , 19, 29099-29105 (2017).
Polycyclic aromatic compounds (naphthalene, anthracene and pyrene) have been intercalated into the superstructures of fullerene nanowhiskers, using a facile liquid-liquid interfacial precipitation (LLIP) method. Due to the interaction between polycyclic molecules and fullerene, the growth of fullerene crystals was interfered in comparison to the fullerene crystal growth without the polycyclic molecules, resulting in the formation of fullerene superstructures with various nanofeatures. Moreover, the fluorescence emissions of the fullerene superstructures were significantly changed due to the intercalation of the polycyclic molecules, implying the influence of molecular packing on the electron transfer within the nanostructures. These results may bring new insights on the control of fullerene nanostructures and to manipulate their optical properties in optoelectronic devices.
"Wood-mimetic skins prepared using horseradish peroxidase catalysis to induce surface wrinkling of chitosan film upon drying ",
Carbohydrate Polymers , 173, 519-525 (2017).
We previously developed bio-based wrinkled surfaces induced by wood-mimetic skins upon drying in which microscopic wrinkles were fabricated on a chitosan (CS) film by immersing it in a phenolic acid solution, followed by horseradish peroxidase (HRP)-catalyzed surface reaction and drying. However, the detailed structure of the resulting wood-mimetic skins, including crosslinking mode and thickness, has not been clarified due to the difficulty of the analysis. Here, we prepare wrinkled films using ferulic acid (FE), vanillic acid (VA), and homovanillic acid (HO) and characterize their structures to clarify the unknown characteristics of wood-mimetic skin. Chemical and structural analyses of wood-mimetic skins prepared using VA and HO indicate that the crosslinking structure in the skin is composed of ionic bonds between CS and an oligophenolic residue generated by the HRP-catalyzed reaction on the CS surface. Moreover, the quantity of these ionic bonds is related to the skin hardness and wrinkle size. Finally, SEM and TOF-SIMS analyses indicate that the skin thickness is on the submicron order (<200 nm).
"Effects of the lateral substituent on the cubic phase formation of two analogous compounds, 4'-n-hexadecyloxy-3'-cyanobiphenyl-4-carboxylic acid (ACBC-16) and its 3'-nitro compound (ANBC-16)",
Liquid Crystals , 42, 143-157 (2015).
Two cubic (Cub) phase forming compounds, 4′-n-hexadecyloxy-3′-cyanobiphenyl-4-carboxylic acid (ACBC-16) and its 3′-nitro analogue (ANBC-16) were studied by infrared (IR) spectroscopy. In the temperature region of the Cub phase, the molar fraction of hydrogen-bonded COOH groups estimated for ACBC-16 was by ≈0.05 at maximum larger than that for ANBC-16 and the aromatic ring C=C stretching (ν(C=C)ring) band frequency of ACBC-16 was by 3 cm−1 lower than that of ANBC-16. The quantum chemical calculation at DFT/B3LYP level, on the one hand, showed no meaningful difference in the stabilisation energy for dimerisation and the ν(C=C)ring band frequency between the respective model compounds. These results can be ascribed to the different steric effects of the side groups; the CN group would make possible the close contact of neighbouring phenyl rings while the bulky NO2 group would not, giving slightly more stabilised dimerisation of ACBC-16 in the Cub phase than in ANBC-16.
"Nanoporous Carbon Sensor with Cage-in-Fiber Structure: Highly Selective Aniline Adsorbent toward Cancer Risk Management",
ACS Applied Materials & Interfaces, 5, 2930-2934 (2013).
Carbon nanocage-embedded nanofibrous film works as a highly selective adsorbent of carcinogen aromatic amines. By using quartz crystal microbalance techniques, even ppm levels of aniline can be repetitively detected, while other chemical compounds such as water, ammonia, and benzene give negligible responses. This technique should be applicable for high-throughput cancer risk management.
" β-Cyclodextrin-crosslinked alginate gel for patient-controlled drug delivery systems: regulation of host-guest interactions with mechanical stimuli",
Journal of Materials Chemistry B , 1, 2155-2161 (2013).
Macroscopic mechanical force has attracted much attention as an existing yet novel energy source for modification of molecular interactions and molecular reactivity. Although various molecular level phenomena have been controlled by using macroscopic mechanical forces, control of host-guest inclusion has not been a research target. Here we report a novel controlled release system triggered by a mechanical stimulus. Release of ondansetron (ODN), an anti-emetic drug, from a designer hydrogel composed of a β-cyclodextrin (CyD) derivative and alginate (AL) can be controlled by mild mechanical compressions that mimic operation by a patient's hand. ODN is released in response to mechanical compressions by changing the inclusion ability of CyD moieties, which may be conformationally distorted, and/or suppressed stabilization of the inclusion complex when an external stress is applied. It is revealed that the release can be induced even by the slight conformational restriction for β-CyD due to the mechanical stimulus. This controlled release technology provides a novel dosing strategy enabling on-demand administration of medicines through a mechanical stimulus generated intentionally by the patient.
"Micrometer-level Naked-eye Detection of Caesium Particulates in the Solid State",
Science and Technology of Advanced Materials , 14, 015002(14pp) (2013).
Large amounts of radioactive material were released from the Fukushima Daiichi nuclear plant in Japan, contaminating the local environment. During the early stages of such nuclear accidents, iodine I-131 (half-life 8.02 d) is usually detectable in the surrounding atmosphere and bodies of water. On the other hand, in the long-term, soil and water contamination by Cs-137, which has a half-life of 30.17 years, is a serious problem. In Japan, the government is planning and carrying out radioactive decontamination operations not only with public agencies but also non-governmental organizations, making radiation measurements within Japan. If caesium (also radiocaesium) could be detected by the naked eye then its environmental remediation would be facilitated. Supramolecular material approaches, such as host-guest chemistry, are useful in the design of high-resolution molecular sensors and can be used to convert molecular-recognition processes into optical signals. In this work, we have developed molecular materials (here, phenols) as an optical probe for caesium cation-containing particles with implementation based on simple spray-on reagents and a commonly available fluorescent lamp for naked-eye detection in the solid state. This chemical optical probe provides a higher spatial resolution than existing radioscopes and gamma-ray cameras.
"Redox Reaction Mechanisms with Non-triiodide Mediators in Dye-Sensitized Solar Cells by Redox Potential Calculations ",
The Journal of Physical Chemistry Letters , 3, 3581-3584 (2012).
We investigate reaction mechanisms of the redox mediators in dye-sensitized solar cells through systematic calculations of redox potentials of possible cobalt complexes and iodides in acetonitrile solution by use of the thermodynamic cycle method with continuum solvent model. The calculated redox potentials were in good agreement with the experimental values, although the experimentalists used different reference electrodes. The maximum open circuit voltage (VOC) of the mediators calculated in this work indicate that the I2 •−/2I− and I2/I2•− as well as the net I2/2I− redox reactions can dominate at both photoanode and counter-electrode.