Four dicopper(II) complexes, [Cu2(µ-X)(bcmp)](ClO4)2 [X = OH (1a) and X = Cl (1b)], [Cu2(µ-OH)(Me4bcmp)](ClO4)2 (2), and [Cu2(bcc)](ClO4)3 (3), were synthesized with three p-cresol-derived ligands, 2,6-bis(1,4,7-triazacyclononylmethyl)-4-meth-ylphenol (Hbcmp), 2,6-bis(1,4,7-triaza-4,7-dimethylcyclonon-ylmethyl)-4-methylphenol (HMe4bcmp), and 2,6-bis(1,4,7,10-tetrazacyclododecylmethyl)-4-methylphenol (Hbcc) to study hydrolytic DNA cleavage. Crystal structures of 1a, 1b, 2, and 3 were determined by X-ray analysis. The pH titrations and spectroscopic studies in the complexations of the ligands with copper(II) perchlorate revealed that the dicopper core structures of 1a, 2, and 3 in the solid state are kept at pH 5–9 in an aqueous solution. DNA binding abilities of 1a, 2, and 3 were examined by isothermal titration calorimetry (ITC). DNA cleavage studies were carried out by using supercoiled plasmid pUC19 DNA. 1a largely accelerated hydrolytic DNA cleavage at pH 5–6 but not at pH 7–8. This is the first example of pH-dependent DNA cleavage by a dicopper complex. Inhibition studies with specific DNA binders, 4′,6-diamidino-2-phenylindole and methyl green, suggested that 1a accelerates the DNA cleavage via GC-specific binding. The mechanistic insights into the pH-dependent DNA cleavage are proposed on the basis of the crystal structures, structures in aqueous solutions, DNA binding modes, and DNA cleavage activities of 1a, 1b, 2, and 3.
Dispersion interaction is one of the most important attractive intermolecular interactions. Because the dispersion interaction is always present, even for neutral molecules, and increases as the number of atoms in a molecule increases, accurate calculations with small computational costs are critical, especially for biosystems and condensed phase systems. In this study, we propose a site-site dispersion potential using a geminal auxiliary basis set that is local, isotropic, and free from empirical parameters. Our method correctly reproduced the Symmetry-Adapted Perturbation Theory (SAPT) data for C6 values and the dispersion energy surface between alkanes and alkenes.
Experimental evidence has been presented on the difference in intermolecular ion-water distances obtained from X-ray and neutron diffraction methods. Simultaneous least squares fitting procedures were performed for X-ray and neutron interference terms observed for (NaCl)x(*H2O)1−x, (x = 0, 0.02, 0.05, and 0.098) and (KCl)x(*H2O)1−x, (x = 0, 0.02, 0.05, and 0.075) solutions at 25 °C, respectively. The null-water mixture was employed for neutron diffraction measurements for these solutions to eliminate structural contribution from hydrogen atoms. It has been revealed that the hydration numbers of Na+ and K+ are concentration dependent and the values for lower-concentration limit are 5 and 6, respectively. The nearest neighbor Na+•••H2O and K+•••H2O distances are obtained to be 2.36–2.37 and 2.75–2.82 Å, respectively. In order to examine the effect of the separate treatment of interactions between ion-oxygen and ion-hydrogen atoms in the X-ray model function, simultaneous fitting procedures were carried out for X-ray and neutron diffraction data observed for 9.8 mol% NaCl and 7.5 mol% KCl solutions by employing the individual atom model for the X-ray interference term. Obtained Na+•••O and K+•••O distances are ca. 0.02 Å shorter than those determined by the simultaneous fit employing the usual united model for water molecules. The nearest neighbor Cl−•••O distance derived from the simultaneous fit by means of the individual atom model exhibits ca. 0.1 Å shorter than that obtained from the fit using the united atom model. The present Cl−•••O distance agrees with that obtained from neutron diffraction measurements on 35Cl/37Cl isotopically substituted aqueous 5 mol% Na*Cl solutions in D2O. The simultaneous fitting analyses employing X-ray model function with the united and individual atom models of water molecule have revealed that the ion-oxygen (water) internuclear distance is significantly shorter than the average separation of electron clouds between ion and neighboring water molecule. The present results indicate that the difference in ion-water distance observed from X-ray and neutron diffraction studies mainly arises from the united atom model of X-ray diffraction data analysis assuming a spherical electron density around oxygen atom within the water molecules.
Two new ionic plastic crystals of [NEtMe2Pr][BEt3Me] and [NEt2MePr][BEt3Me] were found. In contrast, the highest-temperature solid-phase of [NEtMe2Bu][BEt3Me] and [NEt2MeBu][BEt3Me] were assigned to rotator phases. Solid-state 1H and 13C nuclear magnetic resonance (NMR) measurements revealed that both the cations and anions perform isotropic reorientations in the plastic phase. Conversely, the cations of [NEtMe2Bu] and [NEt2MeBu] undergo rotation about an axis. Based on these results, it is revealed that ellipsoidal cations of [NEtMe2Pr]+ and [NEt2MePr]+ can form plastic crystalline phases with [BEt3Me]−. In the lower temperature solid-phase of the plastic phase, a rotator phase was also found in [NEtMe2Pr][BEt3Me] and [NEt2MePr][BEt3Me] salts. This is rarely reported in alkylammonium compounds with [BEt3Me]. 1H NMR spin-lattice relaxation time (T1) measurements showed that activation energies of isotropic reorientation were slightly large when compared to those reported in other ionic plastic crystals constructed with globular cations. This difference can be explained by assuming the aspect ratio. On differential scanning calorimetry (DSC) charts, small entropy changes were recorded at melting points of four compounds. These results support the observation that cations and anions have large degrees of freedom of motion in the highest-temperature solid-phases (plastic and rotator phases).
A variety of organic and inorganic layered compounds are exfoliated into 2D nanomaterials in liquid phase. Improvement of exfoliation yield is a significant challenge for further applications of 2D nanomaterials. However, yield of transition-metal-oxide nanosheets is not so high, such as around 5% for 240 h and 15% for 120 h, in previous exfoliation methods. Here we show a new exfoliation approach to high-yield synthesis of nanosheets. A layered composite of cobalt hydroxide and guest quinone derivative was exfoliated into nanosheets through redox reactions of the interlayer guests in the yield 16–57% for 1 h under mild conditions. The redox reactions of the guest molecules on the layer facilitate efficient exfoliation through improvement of the affinity between the guest and dispersion medium. The present redox-mediated exfoliation approach can be applied to efficient synthesis of a variety of 2D nanomaterials from layered composites.
Fluorous properties represented by water-and-oil repellency are perfluoroalkyl (Rf) compound-specific characteristics, which are widely used for surface coating of glass, electronic devices and textiles for preventing water and grease fouling. According to the stratified dipole-arrays (SDA) theory, the minimum Rf length of (CF2)7 is theoretically necessary for realizing fluorous properties. Unfortunately, however, production of compounds involving this chemical unit is strictly banned because of concerns of environmental pollution, which is a big dilemma. Here, we show that the fluorous properties can be realized by self-assembled monolayer (SAM) even with a short Rf-containing compound, since the SAM technique makes the best use of the self-aggregation property of the Rf groups, and it readily makes the molecules immobile.
A novel tetracationic porphyrin-platinum(II) conjugate was synthesized and characterized. This complex, 4Pt(dach)ClTPyP, showed reasonable water solubility, lack of aggregation, and high singlet oxygen quantum yield. It also exhibited low dark cytotoxicity and excellent photocytotoxicity (Colon26: 0.17 µM; Sarcoma180: 0.25 µM). The mechanisms of cell death have been investigated and are attributed to high singlet oxygen generation, internalization into nucleus, and a caspase-3 induced apoptosis pathway. In the in vivo photodynamic therapy (PDT) assay, 4Pt(dach)ClTPyP completely killed tumor tissue, not simply displaying inhibition of tumor growth, and no recurrence was seen 18 days later after a single administration. All these findings of 4Pt(dach)ClTPyP shed light on a potential clinical use for cancer PDT in the future.
We newly designed and synthesized two kinds of 1,3,5-triazine-cored star-shaped (D-π)3-A molecules with 1-aza 15-crown 5-ether receptors (TSM-ACE) and dipicolylamino receptors (TSM-DPA), which possess an intramolecular charge transfer (ICT) nature and exhibit ICT-based optical properties (ICT transition absorption and fluorescence from a ICT excited state). Both TSM-ACE and TSM-DPA display proton-induced optical spectral blue-shifts followed by red-shifts depending on their inherent two-step protonation behavior. Furthermore, TSM-ACE displays optical spectral blue-shifts followed by red-shifts upon stepwise complexation of Mg2+, whereas TSM-DPA displays optical spectral blue-shifts upon the complexation of Zn2+. The cation sensing mechanism can be explained as follows: (i) the initial blue shift is caused by the decreased ICT donor abilities of three amino-donor-type receptors (a decrease of the ICT efficiency) upon binding cations, and (ii) the second red shift is caused by an increased acceptor ability of the 1,3,5-triazine core upon binding cations. Consequently, we revealed that TSM-ACE and TSM-DPA with different cation-recognition functionalities serve as a unique optical sensor capable of visual and distinct detection of not only protons but also different kinds of metal ions.
Colorimetric analysis with diphenylcarbazide has been used as a simple method to determine hexavalent chromium (Cr(VI)). However, the low sensitivity of this technique makes it difficult to determine concentrations close to the environmental standard value (0.05 mg/L). We found that the phase separation phenomenon produced a small amount of the extraction phase when a mixture of 2-propanol and a small amount of dimethyl phthalate were added to a water sample, and that the Cr(VI)-diphenylcarbazide complex was extracted into this phase with high efficiency. Based on these findings, we report a simple method for colorimetric analysis for determining Cr(VI) with high sensitivity via homogeneous liquid-liquid extraction using water, 2-propanol, and dimethyl phthalate. As a result, the extraction percentage for Cr(VI) was 88% and the concentration factor improved up to 121-fold (27.4 mL → 226 µL). Using the proposed extraction method, determination limit (10σ) and detection limit (3σ) were 0.11 ppb and 0.03 ppb, respectively. This method can be employed for the determination of hexavalent chromium in groundwater systems by the use of EDTA as masking agent.
Ni3Sn2 alloy catalysts supported on various metal oxides (TiO2, Al2O3, ZrO2, SnO2, and CeO2) were successfully prepared by simple hydrothermal method and then applied to the hydrogenation of 4-nitrostyrene under H2 3.0 MPa at 423 K. All the supported catalysts hydrogenated the nitro group more preferentially than the olefin group from the initial reaction stages, showing 100% chemoselectivities towards the desired 4-aminostyrene. This may be attributed to σ-interaction between the oxygen lone pairs in the nitro group and Sn atoms in Ni3Sn2 alloy. By prolonging the reaction times, the 4-aminostyrene yields increased and finally reached the maximum yields. Among the catalysts, Ni3Sn2/TiO2 alloy catalyst showed the highest catalytic activity with remarkably high chemoselectivity towards 4-aminostyrene. The conversion and chemoselectivity were 100% and 79%, respectively, at a reaction time of only 2.5 h. From the physical and chemical characterization of the supported catalysts, it was clear that the catalytic activity was correlated with H2 uptake. The application of the best catalyst for the hydrogenation of a wide variety of substituted nitroarenes resulted in the chemoselective formation of the corresponding aminoarenes.
This review focuses on the design of poly(N-isopropylacrylamide) (PIPAAm)-grafted surfaces for cell sheet preparation and manipulation, which are revolutionary tools for the creation of transplantable two-dimensional (2D) and engineered three-dimensional (3D) cellular tissues. Particularly, the thickness of grafted PIPPAm chains in the perpendicular direction is regulated to achieve temperature-dependent alteration of cell sheet preparation/harvesting. The 2D positioning of grafted PIPAAm in a direction parallel to the material surfaces facilitates spatially controlled micropatterns containing heterotypic cells. This review also describes the 2D manipulation of cell sheets and the creation of cell sheet-layered 3D tissue using the PIPAAm-grafted surface. With the aid of supporting materials such as membranes and gelatin hydrogels, cell sheets on PIPAAm-grafted surfaces can be manipulated and applied for transplantation in clinical settings and for the formation of 3D tissues in vitro. For the next generation of cell sheet-based tissue engineering, a challenging issue is the creation of large, thick tissues/organs such as cardiac and hepatic tissues/organs. The integration of various technologies including bioreactors and micropatterning is essential to achieve the creation of functional engineered 3D organs.
This study aims to synthesize C-4-hydroxy-3-methoxyphenylcalixresorcinarene and investigate the kinetics of its application as an adsorbent for lead(II), copper(II) and chromium(III) ions. The interaction between this adsorbent and these metal ions was also studied. In this work, C-4-hydroxy-3-methoxyphenylcalixresocinarene was synthesized from vanillin and resorcinol as a light red solid in 84% yield, and its ability to adsorb the metal ions was conducted in a batch system. The kinetics and interaction of the adsorbent with these metal ions were analyzed by FAAS spectrometry and FT-IR respectively. The optimum pH values of this adsorbent to adsorb Pb(II), Cu(II) and Cr(III) ions were determined to be 5.48, 5.70 and 4.50 respectively. The adsorption rate order of these metal ions onto adsorbent was found to be Pb(II) > Cu(II) > Cr(III). The competitive adsorption of these heavy metal ions was also investigated. FT-IR spectra showed the presence of interaction between Pb(II) and the adsorbent, but no such interaction was observed between the adsorbent and Cr(III) or Cu(II). Further studies based on the 1H NMR and UV spectra of the free and metal ion loaded adsorbents confirmed the presence of interaction between the adsorbent and all metal cations.
Polyacrylonitrile (PAN)-derived carbon beads with uniform size and high surface area were successfully prepared by the carbonization of PAN and activation by KOH. Physicochemical analysis revealed that the PAN-derived carbon beads activated by KOH possessed larger pore volume and pore width than the same types of carbon beads activated by CO2 and commercially available activated carbon powder. Even if the PAN-derived carbon beads were made into an electrode without any conducting supplements, the electrode possessed a higher specific capacitance than an electrode composed of commercially available activated carbon in the presence of conducting acetylene black powders. Origins of such desirable properties as carbon materials used for electric double layer capacitors were investigated by AC impedance measurements in both aqueous and non-aqueous electrolyte solutions.
Supported NiO nanocluster catalysts were synthesized by using Ni colloid as a precursor and applied to the aerobic oxidation of 1-phenylethanol. Obtained catalysts were characterized through X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS) and in situ X-ray diffraction (XRD). Activated carbon (AC) supported NiO nanocluster catalyst showed catalytic activity toward the aerobic oxidation of 1-phenylethanol without any additives. Only the AC support allowed the NiO catalyst to be active although other supports did not. XAFS and in situ XRD revealed that NiO nanocluster was fixed on the supports successfully. XAFS and XPS gave information about differences in the local structure, chemical state and electronic state of Ni among the different supports. The obtained catalyst showed activity more effectively compared to conventional nickel-based catalysts.
Phytase was immobilized onto electrochemically prepared polypyrrole (PPy) films either in the free, native form (Phy) or encapsulated in phospholipid dipalmitoyl phosphatidylglycerol (DPPG) liposomes (lipo-Phy). The incorporation of Phy into the PPy matrix was verified using cyclic voltammetry, polarization-modulated infrared reflection absorption spectroscopy, and scanning electron microscopy. PPy, PPy/Phy and PPy/lipo-Phy films were characterized by amperometric experiments in phytic acid (PA) solutions at different concentrations. PPy/lipo-Phy showed a more sensitive response, which was confirmed in stable current vs concentration and current vs time curves, and by a superior analytical performance with a saturation concentration of 3.0 mmol L−1 PA. A multidimensional projection technique, IDMAP, was used to project the voltammetric data, and confirmed the higher selectivity for PPy/lipo-Phy by distinguishing PA in a specific range of concentrations.
There are increasing numbers of studies on the design and evaluation of functional ionic liquids (ILs). Recent progress of functional ILs has been reviewed here. Applications of ILs as solvents for hardly-soluble materials in ordinary solvents are discussed mainly from the viewpoint of energy conversion. We focus on a potential application of ILs as electrolyte solution substituents not only for battery but also other electrochemical devices. Also, the uses of ILs as solvents for biomolecules, especially for dissolution of proteins are summarized. Recent progress with zwitterionic ILs and polymerized ILs are also reviewed as unique morphology ILs. Mixtures of molecular liquids and ILs are quite interesting systems, and thermotropic phase change of these mixtures is described including some applications.
To determine why silicic acid elution is often incomplete during regeneration of strong base anion exchange resin columns, an OH− type anion exchange resin (OH− type resin) adsorbing silicic acid was prepared and the desorption (elution) behavior of silicic acid adsorbed to the resin was examined by batch and column experiments. It was first found that silicic acid adsorbed to an OH− type resin polymerizes to form polysilicic acids (Q1, Q2 and Q3 structures) even when a smaller amount of silicic acid than the ion exchange capacity was adsorbed (unsaturated adsorption). Consequently, elution of silicic acid from the OH− type resin column is most likely caused by hydrolytic decomposition of polysilicic acid. Silicic acids with Q0, Q1 and Q2 structures can be easily desorbed from the OH− type resin by immersing them in a 1% NaOH solution for 5 min. On the other hand, silicic acid with the Q3 structure is barely desorbed. In this study, incomplete elution of silicic acid from OH− type resin columns has been found to be caused by polymerization of adsorbed silicic acid and the elution behavior may depend on the polymerization mode.
Although porous materials based on coordination compounds, including metal-organic frameworks (MOFs) and porous coordination polymers (PCPs), have well-defined pore structures and promising properties, they can efficiently be prepared by conventional and facile methods. Among coordination compounds, Prussian blue (PB) and its analogues (PBA) show high physical/chemical properties and potential as a multifunctional platform for various applications such as information records, sensing, batteries, biomedicine, imaging, and water purification. This review introduces versatile paths for nano- and meso-structural controls and demonstrates strong relationship between nanoarchitectures and properties with regard to PB and PBAs. This review will provide some guidance for future derivations of nanoarchitectonics based on coordination compounds which are PB and PBA.
Phosphorus is an essential element in living organisms. Evaluating prebiotic processes that lead to phosphorylated biomolecules is an important step toward understanding the origin of life. Schreibersite ([Fe,Ni]3P) is a meteoritic phosphorus mineral which releases various phosphorus species reactive toward biomolecules. We studied the reactions between biomolecules and pyrophosphorus acid (H4P2O5), which is a phosphorous acid derivative released from schreibersite. The reactions between pyrophosphorous acid and molecules having hydroxy groups were carried out under mild alkaline conditions. Notably, some biologically important molecules such as L-serine, L-tyrosine, L-threonine, D-ribose, and D-glyceraldehyde reacted with pyrophosphorous acid to give corresponding phosphonates. These results suggested that if schreibersite and the biomolecules co-existed in the prebiotic earth, they formed the phosphonates which were able to play roles as surrogates or precursors of phosphorylated biomolecules.