Search

To study the effect of fatty acid unsaturation on low-rank coal flotation, oleic acid, linoleic acid, and linolenic acid with the same number of carbon atoms but an increasing number of double bonds were selected as flotation collectors and compared with conventional nonpolar collector diesel oil. Adhesion force measurements between particles and bubbles and molecular dynamics simulation of reagent adsorption were used to reveal the mechanism of unsaturated fatty acids enhancing low-rank coal flotation. The flotation results show that unsaturated fatty acid collectors surpass nonpolar diesel oil in flotation performance, and the flotation yield of low-rank coal increases with fatty acid unsaturation. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to analyze the surface morphology and surface functional groups of low-rank coal. SEM results show that the surface of low-rank coal is loose and contains many pores and cracks, which is not conducive to the spreading of chemicals on coal surfaces and the mineralization of bubbles and particles. The results of FTIR and XPS show that the surface of low-rank coal contains several oxygen-containing functional groups and has poor hydrophobicity, resulting in low flotation recovery. The adhesion force between bubbles and coal surfaces was measured in different collector solutions. The maximum adhesion between bubbles and coal surfaces increased with collector unsaturation in diesel oil, oleic acid, linoleic acid, and linolenic acid systems, indicating an increase in the floatability of coal particles with collector unsaturation. Furthermore, the molecular dynamics simulation of unsaturated fatty acid adsorption showed that unsaturated fatty acids spread on coal surfaces through hydrogen bonding between the polar groups of these molecules and surfaces. With an increasing number of double bonds, unsaturated fatty acids become more polar, and the spread of unsaturated fatty acids on coal surfaces gradually becomes more extensive, which leads to increasing particle floatability. This is the main reason for the increase in flotation recovery of low-rank coal with unsaturated fatty acids.

The design of porphyrin-based dendrimers featuring conjugated fluorenyl dendrons via alkene spacers allows evaluating the importance of the role of these spacers on the optical properties of interest. In the continuation of previous studies, a second-generation porphyrin-based dendrimer was synthesized and metalated by Zn(II) along with its known first-generation homologue. The targeted free-base porphyrin was obtained by repetitively cycling a Michaelis–Arbuzov reaction and a Horner–Wadsworth–Emmons reaction to construct the desired vinyl-containing dendrons. After metalation by Zn(II), meso-tetraphenylporphyrin-cored dendrimers with eight (ZnTPP-D1) and sixteen (ZnTPP-D2) fluorenyl arms at their periphery were eventually isolated. These species allow evaluating the influence of the central metal and of the 1,2-alkyne for 1,2-alkene exchange on fluorescence, oxygen photosensitization, and two-photon absorption. Such structure–property relationships are currently needed for the design of optimal dendrimeric photosensitizers allowing combined two-photon-based photodynamic therapy (2P-PDT) and imaging.

In this review, the latest achievements in the field of multiply bonded organogermanium derivatives, mostly reported within the last two decades, are presented. The isolable Ge-containing analogues of alkenes, alkynes, 1,3-dienes, allenes, and vinylidenes are discussed, and for each class of unsaturated organogermanium compounds, the most representative examples are given. The synthetic approaches toward homonuclear multiply bonded combinations solely consisting of germanium atoms, and their heteronuclear variants containing germanium and other group 14 elements, both acyclic and cyclic, are discussed. The peculiar structural features and nonclassical bonding nature of the abovementioned compounds are discussed based on their spectroscopic and structural characteristics, in particular their crystallographic parameters (double bond length, trans-bending at the doubly bonded centers, and twisting about the double bond). The prospects for the practical use of the title compounds in synthetic and catalytic fields are also briefly discussed.

In the present investigation, 48 new tertiary amine derivatives of cinnamic acid, phenylpropionic acid, sorbic acid and hexanoic acid (4d–6g, 10d–12g, 16d–18g and 22d–24g) were designed, synthesized and evaluated for the effect on AChE and BChE in vitro. The results revealed that the alteration of aminoalkyl types and substituted positions markedly influences the effects in inhibiting AChE. Almost of all cinnamic acid derivatives had the most potent inhibitory activity than that of other acid derivatives with the same aminoalkyl side chain. Unsaturated bond and benzene ring in cinnamic acid scaffold seems important for the inhibitory activity against AChE. Among them, compound 6g revealed the most potent AChE inhibitory activity (IC50 value: 3.64 µmol/L) and highest selectivity over BChE (ratio: 28.6). Enzyme kinetic study showed that it present a mixed-type inhibition against AChE. The molecular docking study suggested that it can bind with the catalytic site and peripheral site of AChE.

Two 2-phenyl-benzofurans, moracin C {2-[3′,5′-dihydroxy-4′-(3-methlbut-2-enyl)phenyl]-6-hydroxybenzofuran} and its isomer iso-moracin C{2-[3′,5′-dihydroxy-4′-(3-methlbut-1-enyl)phenyl]-6-hydroxybenzofuran}, were comparatively studied using redox-related antioxidant assays and non-redox antioxidant assays. Moracin C always resulted in higher IC50 values than iso-moracin C in the redox-related antioxidant assays, including •O2−-inhibition, Cu2+-reducing power, DPPH•-inhibition, and ABTS+•-inhibition assays. In the non-redox antioxidant assay, moracin C and iso-moracin C underwent similar radical-adduct-formation (RAF), evidenced by the peaks at m/z 704 and m/z 618 in HPLC-MS spectra. In conclusion, both moracin C and iso-moracin C can act as 2-phenyl-benzofuran antioxidants; their antioxidant mechanisms may include redox-related ET and H+-transfer, and non-redox RAF. A double bond at the conjugation position can enhance the redox-related antioxidant potential, but hardly affects the RAF potential.