Fluorescence Properties and Exciplex Formation of Emissive Naphthyridine Derivatives: Application as Sensors for Amines

Water-soluble donor–acceptor-type fluorophore 15Nap-Cl having two trifluoromethyl groups and a Cl group on a 1,5-aminonaphthyridine framework was prepared. Fluorophore 15Nap-Cl showed strong solvatochromic fluorescence, and, as the solvent polarity increased, a bathochromic shift was observed accompanied by an increase in the fluorescence quantum yield. In addition, in the presence of amines such as ethylamine, diethylamine, and aniline, further considerable bathochromic shifts in the fluorescence were observed. Density functional calculations identified the source of the fluorescence behavior as exciplex formation between 15-Nap-Cl and the corresponding amine. The fluorescence behavior was exploited to fabricate a sensor that can identify various primary, secondary, and tertiary amines.     

Albidosides H and I,two new triterpene saponins from the barks of Acacia albida Del. (Mimosaceae)

Two new triterpene saponins, albidosides H (1) and I (2), along with the three known saponins were isolated from the barks of Acacia albida. Their structures were elucidated on the basis of extensive 1D- and 2D-NMR studies and mass spectrometry. Albidosides H (1) and I (2) were assayed for their cytotoxicity against HeLa and HL60 cells using MTT method.     

Total Biosynthesis of Melleolides from Basidiomycota Fungi: Mechanistic Analysis of the Multifunctional GMC Oxidase Mld7

Mushroom terpenoids are biologically and chemically diverse fungal metabolites. Among them, melleolides are representative sesquiterpenoids with a characteristic protoilludane skeleton. In this study, we applied a recently established hot spot knock-in method to elucidate the biosynthetic pathway leading to 1α-hydroxymelleolide. The biosynthesis of the sesquiterpene core involves the cytochrome P450 catalyzing stepwise hydroxylation of the Δ⁶-protoilludene framework and a stereochemical inversion process at the C5 position catalyzed by short-chain dehydrogenase/reductase family proteins. The highlight of the biosynthesis is that the flavoprotein Mld7 catalyzes an oxidation-triggered double-bond shift accompanying dehydration and acyl-group-assisted substitution with two different nucleophiles at the C6 position to afford the Δ⁷-protoilludene derivatives, such as melleolide and armillarivin. The complex reaction mechanism was proposed by DFT calculations. Of particular importance is that product distribution is regulated by interaction with the cell membrane.     

Ruthenium complexes with ferrocene-based P,C,P pincer ligand

First ruthenium complexes with a ferrocene-based pincer ligand were synthesized. The cyclometallation of 1,3-bis[(di-tert-butylphosphino)methyl]ferrocene with RuCl₂(DMSO)₄ in 2-methoxyethanol afforded the RuCl(CO)[{2,5-(Bu^t ₂PCH₂)₂C₅H₂}Fe(C₅H₅)](RuCl(CO) ) complex (5). Complex 5 reversibly binds CO to form the RuCl(CO)₂ complex (6). The analogous reaction in the presence of NaBAr′₄ (Ar′ = 3,5-(CF₃)₂C₆H₃) produced the cationic complex {Ru(CO)₂ }BAr′₄ (7). The structures of complexes 5 and 7 were established by single-crystal X-ray diffraction. The X-ray diffraction study revealed an agostic interaction between one of the C-H bonds of the axial (exo-oriented with respect to the ferrocene iron atom) tert-butyl group and the Ru atom in complexes 5 and 7. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1695–1701, September, 2007.     

Discrete Approximations of Determinantal Point Processes on Continuous Spaces: Tree Representations and Tail Triviality

We prove tail triviality of determinantal point processes \( \mu \) on continuous spaces. Tail triviality has been proved for such processes only on discrete spaces, and hence we have generalized the result to continuous spaces. To do this, we construct tree representations, that is, discrete approximations of determinantal point processes enjoying a determinantal structure. There are many interesting examples of determinantal point processes on continuous spaces such as zero points of the hyperbolic Gaussian analytic function with Bergman kernel, and the thermodynamic limit of eigenvalues of Gaussian random matrices for \(\hbox {Sine}_2 , \hbox {Airy}_2 , \hbox {Bessel}_2 \), and Ginibre point processes. Our main theorem proves all these point processes are tail trivial.     

Modified Vonk's Method to Determine Crystallinity and Crystal Distortion in Polymers

Using a modified method developed from Vonk's method, detailed values of crystallinity and crystal disorder were obtained by wide angle X-ray diffraction (WAXD). In Vonk's method, the crystallinity (w) is determined by extrapolation of the WAXD experimental curve back to zero scattering angle, while the distortion factor (k) is determined by the inclination of the experimental curve at zero scattering angle. In our new method, both w and k are determined at the same time by using the least squares method. In order to show the efficiency of our method, the new fitting procedure was applied to the experimental values of polyethylene and polyethylene terephthalate as measured by Vonk, and the values of w and k determined by our new method were compared with those found by Vonk's method. The new fitting method has the advantage that it uses the whole experimental curve. Moreover, our modified Vonk's method enables us to discuss crystal distortions as arising from first-kind (thermal) disorder and second-kind (paracrystalline) disorder.     

Interrelation between inhomogeneity and cyclability in O3‐NaFe1/2Co1/2O2

O3‐NaFe_1/2Co_1/2O₂ shows initial capacity of 160 mAh/g and an average operating voltage of 3.1 V (vs. Na) with good cyclability, and is a promising candidate of the cathode materials for sodium‐ion secondary batteries (SIBs). Here, we found that the cyclability of the slowly‐cooled sample is much worse than that of quenched one, even though the former sample keeps the O3‐type structure. The energy dispersive X‐ray spectroscopy (EDX) images suggest that the slow‐cooled sample (Na_x Fe_1–yCo_y O₂) is inhomogeneous in the Fe concentration (1 – y), perhaps triggered by the Na deficiency (1 – x). We ascribed the poor cyclability in the slowly‐cooled sample to the concentration inhomogeneity (Δy). The Δy is further responsible for the fluctuation of the lattice constants (a and c), as revealed by the Williamson–Hall plot. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Facile formation of five-membered N-heterocyclic zirconacycloallenoids

The reaction of η(2)-iminozirconocene chloride complexes with trimethylsilylethynyl lithium leads to rapid C-C coupling at room temperature to yield the corresponding five-membered aza-zirconacycloallenoids. Such compounds were also obtained by trapping of in situ generated zirconocene with alkynyl imines.     

Synthesis of 3,3-disubstituted α-tetralones by rhodium-catalysed reaction of 1-(2-haloaryl)cyclobutanols

The rhodium-catalysed reaction of 1-(2-haloaryl)cyclobutanols afforded 3,3-disubstituted α-tetralones. The reaction was applied to the asymmetric synthesis of α-tetralones bearing a chiral quaternary carbon centre at the 3-position, which was otherwise difficult to execute.