Synthesis and photoluminescent properties of 1,1'-binaphthyl-based chiral phenylenevinylene dendrimers

New chiral, soluble binaphthyl derivatives that incorporate stilbenoid dendrons at the 6,6'-positions have been prepared. The synthesis of the new enantiopure dendrimers was performed in a convergent manner by Horner-Wadsworth-Emmons (HWE) reaction of the appropriately functionalized 1,1'-binaphthyl derivative (R)-1 and the appropriate dendrons (R)(2n)G(n)-CHO. Different electroactive units were incorporated in the peripheral positions of the dendrons in order to tune both the optical and electrochemical behavior of these systems. Fluorescence measurements on the chiral dendrimers reveal a strong emission with maxima between 409 and 508 nm depending upon the substitution pattern. Finally, the redox properties of the dendrimers were determined by cyclic voltammetry, showing the influence of the functional groups at the peripheral positions of the dendrimer on the redox behavior of these systems.     

Electrochemical investigation of hymecromone at a multi-wall carbon nano-tube/cetyl pyridine bromine composite film electrode

A multi-wall carbon nanotube (MWNT)/cetyl pyridine bromine (CPB) composite film modified glassy carbon electrode (GCE) was developed for the electrochemical determination of hymecromone in phosphonate buffer. Electrochemical behaviour of hymecromone at the composite film electrode was investigated with voltammetry. Compared with an irreversible oxidation of hymecromone at the bare GCE, the oxidation peak current was enhanced greatly at the film electrode. Some parameters such as pH, scan rate, accumulation potential and accumulation time were optimized. Under optimal conditions, an oxidation peak at 0.82 V was employed to determine hymecromone electrochemically. A linearity between the oxidation peak current and the hymecromone concentration was obtained in the range of 3.0 × 10⁻⁷ − 2.0 × 10⁻⁵ mol 1⁻¹ with a detection limit of 8.0 × 10⁻⁸ mol 1⁻¹. The proposed procedure was successfully applied to assay hymecromone in pharmaceutical formulation with satisfactory results. The text was submitted by the authors in English.     

Synthesis and mechanism research of an ethylene glycol-based sol-gel method for preparing PZT nanopowders

Lead zirconate titanate nanopowders Pb(Zr_0.52Ti_0.48)O₃ (PZT) were prepared by modified sol-gel process in ethylene glycol system with zirconium nitrate as the zirconium source. The research showed that it was critical to add lead acetate after the reaction of zirconium nitrate and tetrabutyl titanate in ethylene glycol system for preparing PZT of exact titanium content. The reaction mechanisms of the sol synthesis, preparation of xerogel and agglutinating process were characterized through using FT-IR, NMR, TG-FTIR, and GC-MS. The experiment proved that ethylene glycol system did not rely on hydrolysis and condensation reactions in the process of the sol formation, but on the formation of chain or network large molecules from complexation of ethylene glycol and all Ti and minor Pd, Zr. In the preparation of xerogel, the complexation reaction was so completed that it formed large molecules network composed of metal and dioxyethyl. Bulk weight loss happened before 350°C in the process of sintering xerogel to prepare PZT nanopowders. Volatile matters and vapor phase decomposition resultants were primarily oxy-compounds including ethylene glycol, aldehyde-ketone compounds, carbon dioxide and nitrate radical conversion matters. After 350°C, primary vapor phase decomposition resultants were carbon dioxide and minor carbonyl compound.     

Two novel four-coordinated zinc(II) complexes [Zn(dmatrz)<Subscript>2</Subscript>Cl<Subscript>2</Subscript>] and [Zn(dmatrz)<Subscript>2</Subscript>(SCN)<Subscript>2</Subscript>] exhibiting strong blue fluorescent properties

Two novel complexes, [Zn(dmatrz)₂]Cl₂ (1) and [Zn(dmatrz)₂(SCN)₂] (2), have been prepared and characterized by X-ray crystallography, absorption and luminescence spectrometries (dmatrz=3,5-dimethy-4-amino-1,2,4-triazole). The coordination environment of the zinc(II) ions in (1) and (2) has a distorted tetrahedral geometry completed via two independent nitrogen atoms of two triazole ligands and two anions, respectively. Both (1) and (2) show strong blue luminescence properties. Furthermore, (1) displays stronger blue photoluminescence than (2) as the result of different anions (Cl^- and SCN^-) coordinated to the zinc(II) ions.     

Hydrogen peroxide oxidation of di(hydroxo)platinum(II) species in carboxylic acids

A facile procedure for synthesizing the mono(hydroxo)tris(carboxylato)platinum(IV) species has been achieved. The reaction of [Pt^II(OH)₂(dmpda)] (dmpda=2,2-dimethyl-1,3-propanediamine) with a 30% aqueous solution of H₂O₂ in the presence of a carboxylic acid produces a stable [Pt^IV(OOCR)₃(OH)(dmpda)] (R=Me, Et) complex in high yield. The crystal structures of [Pt^IV(OOCMe)₃(OH)(dmpda)] . H₂O (triclinic P1 bar, a=8.761(2) Å, b=9.245(3) Å, c=10.659(2) Å, =106.25(2)°, =93.90(2)°, =98.92(2)°, V=813.1(3) ų, Z=2, R= 0.0474) and [Pt^IV(OOCEt)₃(OH)(dmpda)] (monoclinic P2₁/c, a=12.777(4) Å, b=10.514(2) Å, c=14.971(3) Å, =107.40(2)°, V=1919.2(8) ų, Z=4, R=0.0611) show that the hydroxyl group has been selectively positioned at an axial site. The intramolecular hydrogen bond between the OH and C=O moiety exists (O(H)...=C, 2.83 Å for [Pt^IV(OOCMe)₃(OH)(dmpda)] · H₂O; 2.72 Å for [Pt^IV(OOCEt)₃(OH)(dmpda)]. Formation of the axial-mono(hydroxo)tris(carboxylato)platinum(IV) species may be ascribed to a combination of `reactive-equatorial effects' with `cis-addition' in the carboxylic acid.     

2020 Roadmap on two-dimensional nanomaterials for environmental catalysis

This roadmap demonstrates a series of two-dimensional nanomaterials, such as graphene, black phosphorus, oxides, layered double hydroxides, chalcogenides, bismuth-based layered compounds, MXenes, metal organic frameworks, covalent organic frameworks, and others, for environmental catalysis.     

Study on multimers and their structures in molecular association mixture

Self-association system of(R)-1,3-butanediol in dilute carbon tetrachloride(CCl4)solution is studied as a model of molecular association mixture.Analysis methods including FSMWEFA(fixed-size moving window evolving factor analysis)combined with PCA(principal component analysis),SIMPLISMA (simple-to-use interactive self-modeling mixture analysis),and ITTFA(iterative target transformation factor analysis)are adopted to resolve infrared spectra of(R)-1,3-butanediol solution.Association number and equilibrium constant are computed.(R)-1,3-butanediol in dilute inert solution is determined as a monomer-trimer equilibrium system.Theoretical investigation of trimer structures is carried out with DFT(density functional theory),and structural factors are analyzed.     

<Emphasis Type="Italic">Brønsted</Emphasis> Acids in Ionic Liquids: Fundamentals,Organic Reactions,and Comparisons

Summary. A background for studying acids in various solvents is developed, emphasizing the importance of knowing to what extent a solvent conducts electricity and is therefore ionized, the dissociation equilibria of common molecular solvents and the acidic and basic species generated by solvent leveling. Acidity measurements in the atypical solvent water are discussed and the common method of expressing acidity in other systems – by Hammett values – is introduced. Representative examples of reactions involving Br?nsted acids in ionic liquids are presented and attention paid to the questions of speciation and acidity values. It is found that the gas phase proton affinity of a base is often a better guide to the acidity of its conjugate acid in an ionic liquid than is the dissociation constant of the said acid in water.     

Phenanthroline complexes bearing diamide-anion recognition sites

The synthesis and anion binding properties of new ruthenium(II) and cobalt(II) phenanthroline complexes, containing two amide subunits are described. Evidence for anion binding in dimethyl sulfoxide (DMSO) solution was obtained from u.v.–vis titration experiments. Results indicated that these receptors showed strong affinity for F⁻ and AcO⁻, and showed weak affinity for OH⁻ and H₂PO ₄ ⁻ , and showed no affinity for Cl⁻, Br⁻, I⁻. These receptors interacted with various anions examined through hydrogen-bond formation.     

Sensitively probing the cofactor redox species and photo-induced electron transfer of wild-type and pheophytin-replaced photosynthetic proteins reconstituted in self-assembled monolayers

An ultrathin, ordered, and packed protein film, consisting of the 2-mercaptoacetic acid (MAA), polydimethyldiallylammonium chloride (PDDA), and wild-type (WT) photosynthetic reaction center (RC; termed as WT-RC) or its pheophytin (Phe)-replaced counterpart (termed as Phe-RC), was fabricated by self-assembling technique onto gold electrode for facilitating the electron transfer (ET) between RC and the electrode surface. Near-infrared (NIR)-visible (Vis) absorption and fluorescence (FL) emission spectra revealed the influence of pigment substitution on the cofactors arrangement and excitation relaxation of the proteins, respectively. Square wave voltammetry (SWV) and photoelectric tests were employed to systematically address the differences between the WT-RC films and mutant ones on the direct and photo-induced ET. The electrochemical results demonstrated that ET initiated by the oxidation of the primary donor (P) was obviously slowed down, and the formed P⁺ had more population as well as more positive redox potential in the Phe-RC films compared with those in the WT ones. The photoelectrochemical results displayed the dramatically enhanced photoelectric performances of the mutant ones, further suggesting the slow-down formation of final charge-separated state in Phe-RC. The functionalized protein films introduced in this paper provided an efficient approach to sensitively probe the redox cofactors and ET differences resulting from only minor changes in pigment arrangement in the pigment–protein complex. The favored ET process observed for the membrane proteins RC was potentially valuable for a deep understanding of the multi-step biological ET process and development of versatile bioelectronic devices.