Near‐Infrared‐III‐Absorbing and ‐Emitting Dyes: Energy‐Gap Engineering of Expanded Porphyrinoids via Metallation

The synthesis of organometallic complexes of modified 26π‐conjugated hexaphyrins with absorption and emission capabilities in the third near‐infrared region (NIR‐III) is described. Symmetry alteration of the frontier molecular orbitals (MOs) of bis‐Pd^II and bis‐Pt^II complexes of hexaphyrin via N‐confusion modification led to substantial metal d_π–p_π interactions. This MO mixing, in turn, resulted in a significantly narrower HOMO–LUMO energy gap. A remarkable long‐wavelength shift of the lowest S₀→S₁ absorption beyond 1700 nm was achieved with the bis‐Pt^II complex, t ‐Pt₂‐3 . The emergence of photoacoustic (PA) signals maximized at 1700 nm makes t ‐Pt₂‐3 potentially useful as a NIR‐III PA contrast agent. The rigid bis‐Pd^II complexes, t ‐Pd₂‐3 and c ‐Pd₂‐3 , are rare examples of NIR emitters beyond 1500 nm. The current study provides new insight into the design of stable, expanded porphyrinic dyes possessing NIR‐III‐emissive and photoacoustic‐response capabilities.     

Long-term behavior of 137Cs and 3H activities from TEPCO Fukushima NPP1 accident in the coastal region off Fukushima,Japan

Journal of Radioanalytical and Nuclear Chemistry - Decreasing trends of both 137Cs and 3H activity concentrations and an increasing trend of 3H/137Cs activity ratio at Fukushima Dai-ichi Nuclear...     

Akaike's Information Criterion for Stoichiometry Inference of Supramolecular Complexes

“How do we decide the stoichiometry of host–guest complexes?” This question has long been answered by the Job plot since its first report in 1928. However, as the Job plot was claimed to be misleading in 2016, the question became an open question again and called for renewed investigations. An information-theoretic approach, called Akaike's information criterion, is introduced in this study to select the best model of host–guest complexes, which can rank the models with weight of evidence. A few test cases with unique cylindrical hosts were examined to demonstrate the applicability of the information-theoretic method. Consequently, reasonable views over the thermodynamic behaviors of dumbbell-and-cylinder complexes were obtained. Akaike's information criterion can be a useful and superior alternative to statistical null hypothesis testing, which was proposed as a remedy in place of the Job plot.     

Facile Processing of Unsubstituted π-Conjugated Aromatic Polymers through Water-solubilization Using Aromatic Micelles

π-Conjugated aromatic polymers (πCAPs) are central components of functional materials yet suffer from insolubility without multiple covalent substituents on their backbones. We herein disclose a new strategy for the facile processing of unsubstituted heterocyclic πCAPs (i.e., poly(para-phenylene-2,6-benzobisoxazole) and poly(benzimidazobenzo-phenanthroline)), independent of the polymer length, via non-covalent encircling with aromatic micelles, composed of bent aromatic amphiphiles, in water. The UV/Visible studies reveal that the efficiencies of the present encircling method are ≈10 to 50-fold higher than those using conventional amphiphiles under the same conditions. The AFM and SEM analyses of the resultant aqueous polymer composites show that otherwise insoluble πCAPs form fine bundles (e.g., ≈1 nm in thickness) in the tubular aromatic micelles, through efficient π-stacking interactions. In the same way, pristine poly(para-phenylene) can be dissolved in water, displaying enhanced fluorescence (10-fold), relative to the polymer solid. Two types of unsubstituted πCAPs are likewise co-encircled in water, indicated by UV/Visible analysis. Importantly, aqueous processing of the encircled πCAPs into free-standing single- or multicomponent films with submicrometer thickness is demonstrated through a simple filtration-annealing protocol.     

Reconfigurable Photonic Crystal Reversibly Exhibiting Single and Double Structural Colors

Unlike absorption-based colors of dyes and pigments, reflection-based colors of photonic crystals, so called “structural colors”, are responsive to external stimuli, but can remain unfaded for over ten million years, and therefore regarded as a next-generation coloring mechanism. However, it is a challenge to rationally design the spectra of structural colors, where one structure gives only one reflection peak defined by Bragg's law, unlike those of absorption-based colors. Here, we report a reconfigurable photonic crystal that exhibits single-peak and double-peak structural colors. This photonic crystal is composed of a colloidal nanosheet in water, which spontaneously adopts a layered structure with single periodicity (407 nm). After a temperature-gradient treatment, the photonic crystal segregates into two regions with shrunken (385 nm) and expanded (448 nm) periodicities, and thus exhibits double reflection peaks that are blue- and red-shifted from the original one, respectively. Notably, the transition between the single-peak and double-peak states is reversible.     

Fluorescence Response and Self-Assembly of a Tweezer-Type Synthetic Receptor Triggered by Complexation with Heme and Its Catabolites

There is increasing interest in the development and applications of synthetic receptors that recognize target biomolecules in aqueous media. We have developed a new tweezer-type synthetic receptor that gives a significant fluorescence response upon complexation with heme in aqueous solution at pH 7.4. The synthetic receptor consists of a tweezer-type heme recognition site and sulfo-Cy5 as a hydrophilic fluorophore. The receptor–heme complex exhibits a supramolecular amphiphilic character that facilitates the formation of self-assembled aggregates, and both the tweezer moiety and the sulfo-Cy5 moiety are important for this property. The synthetic receptor also exhibits significant fluorescence responses to biliverdin and bilirubin, but shows very weak fluorescence responses to flavin mononucleotide, folic acid, and nicotinamide adenine dinucleotide, which contain smaller π-scaffolds.     

Application of the thermal history of copper sulfate solution to industrial crystallization (I). Crystallization with pilot plant

The relationship between the thermal history and the waiting time in nucleation decided for the aqueous solution of sodium chlorate was verified for the aqueous solution of copper sulfate using pilot crystallizers. The following items were clarified as the result of the experiments.

• (1) The cooling method is more stable to nucleation in comparison with the vacuum cooling method even at the same operational conditions.
• (2) The desirable effect of the thermal history is recognized only in the case in which the solution is heated up to a high degree of undersaturation.
• (3) The residence time at an undersaturated state has an important role to dissociate embryos in solution.

     

Inclusion Complexation of a Seleno-Organic Antioxidant, Ebselen, with Cyclodextrins in Aqueous Solution

The interaction of ebselen, 2-phenyl-1,2-benzisoselenazol-3(2H)-one, a novel neuroprotective agent, with cyclodextrins (CyDs) in aqueous solution was studied by the solubility method and spectroscopic methods. The ability of sulfobutyl ether -CyD (SBE7--CyD, average degree of substitution= 6.2) to solubilize ebselen was greater, and its stability constant (> 2000 M^-1) was significantly higher than those (< 1000 M^-1) of other CyD complexes employed. The stability constant of the complexes rose as hydrophobicity of the substituents of CyDs increased, whereas it was negligibly affected by change in ionic strength of the medium, indicating a significant contribution of hydrophobic interaction in the complexation. SBE7--CyD gave positive and negative CD bands at around 320 and 350 nm, respectively, indicating that the guest is embedded in the asymmetric locus of the CyD cavity. ¹H-NMR spectroscopic studies suggested that the mono-substituted benzene ring of ebselen is preferably included in the cavity of SBE7--CyD. The results indicate that SBE7--CyD is useful as a solubilizing agent for ebselen.