The Effect of Surfactant-Modified Montmorillonite on the Cross-Linking Efficiency of Polysiloxanes

Polymer–clay mineral composites are an important class of materials with various applications in the industry. Despite interesting properties of polysiloxanes, such matrices were rarely used in combination with clay minerals. Thus, for the first time, a systematic study was designed to investigate the cross-linking efficiency of polysiloxane networks in the presence of 2 wt % of organo-montmorillonite. Montmorillonite (Mt) was intercalated with six quaternary ammonium salts of the cation structure [(CH3)2R’NR]+, where R = C12, C14, C16, and R’ = methyl or benzyl substituent. The intercalation efficiency was examined by X-ray diffraction, CHN elemental analysis, and Fourier transform infrared (FTIR) spectroscopy. Textural studies have shown that the application of freezing in liquid nitrogen and freeze-drying after the intercalation increases the specific surface area and the total pore volume of organo-Mt. The polymer matrix was a poly(methylhydrosiloxane) cross-linked with two linear vinylsiloxanes of different siloxane chain lengths between end functional groups. X-ray diffraction and transmission electron microscopy studies have shown that the increase in d-spacing of organo-Mt and the benzyl substituent influence the degree of nanofillers’ exfoliation in the nanocomposites. The increase in the degree of organo-Mt exfoliation reduces the efficiency of hydrosilylation reaction monitored by FTIR. This was due to physical hindrance induced by exfoliated Mt particles.

Chloride Salts of Triethyl- and Benzyl-Triethyl-Ammonium: A New Antifungal for Giant Bamboo (Dendrocalamus asper) Preservation

In this study, quarternary ammonium salts based on triethylammonium and benzyltriethylammonium cations with the anion of chloride are successfully used for giant bamboo (Dendrocalamus Asper) preservation. These salts are new biocides as well as new salts which penetrate bamboo well. The prepared salts with hydrogen and benzyl substituent at the cation and consisted of chloride anion, exhibited fungicidal activity against Aspergillus Flavus. The effective and lethal doses were measured by the agar-plate method. In their activity against bamboo degrading fungi, salt of benzyl-triethyl-ammonium chloride was comparable with commercially available benzalkonium chloride and didecyldimethylammonium. Keywords: Triethylammonium, Benzyltriethylammonium, chloride, antifungal, and giant bamboo (Dendrocalamus Asper) and Aspergillus Flavus

Antiplasmodial Activity of p-Substituted Benzyl Thiazinoquinone Derivatives and Their Potential against Parasitic Infections

Malaria is a life-threatening disease and, what is more, the resistance to available antimalarial drugs is a recurring problem. The resistance of Plasmodium falciparum malaria parasites to previous generations of medicines has undermined malaria control efforts and reversed gains in child survival. This paper describes a continuation of our ongoing efforts to investigate the effects against Plasmodium falciparum strains and human microvascular endothelial cells (HMEC-1) of a series of methoxy p-benzyl-substituted thiazinoquinones designed starting from a pointed antimalarial lead candidate. The data obtained from the newly tested compounds expanded the structure–activity relationships (SARs) of the thiazinoquinone scaffold, indicating that antiplasmodial activity is not affected by the inductive effect but rather by the resonance effect of the introduced group at the para position of the benzyl substituent. Indeed, the current survey was based on the evaluation of antiparasitic usefulness as well as the selectivity on mammalian cells of the tested p-benzyl-substituted thiazinoquinones, upgrading the knowledge about the active thiazinoquinone scaffold.

Stereoselective Synthesis and Antiproliferative Activity of Steviol-Based Diterpen Aminodiols

A library of steviol-based trifunctional chiral ligands was developed from commercially available natural stevisoide and applied as chiral catalysts in the addition of diethylzinc to benzaldehyde. The key intermediate steviol methyl ester was prepared according to literature procedure. Depending on the epoxidation process, both cis- and trans-epoxyalcohols were obtained. Subsequent oxirane ring opening with primary and secondary amines afforded 3-amino-1,2-diols. The ring opening with sodium azide followed by a “click” reaction with alkynes resulted in dihydroxytriazoles. The regioselective ring closure of N-substituted aminodiols with formaldehyde was also investigated. The resulting steviol-type aminodiols were tested against a panel of human adherent cancer cell lines (A2780, SiHa, HeLa, and MDA-MB-231). It was consistently found that the N-benzyl substituent is an essential part within the molecule and the ring closure towards N-benzyl substituted oxazolidine ring system increased the antiproliferative activity to a level comparable with that of cisplatine. In addition, structure–activity relationships were examined by assessing substituent effects on the aminodiol systems.

Reinvestigation of the Synthesis of "Covalent-Assembly" Type Probes for Fluoride Ion Detection. Identification of Novel 7-(Diethylamino)coumarins with Aggregation-Induced Emission Properties

An unprecedented C-3 functionalization of 4-(diethylamino)salicylaldehyde through a Friedel-Crafts type alkylation reaction has been discovered during the synthesis of "covalent-assembly"-based fluorescent probes for detection of fluoride ions. The resulting Friedel-Crafts adduct was successfully used for the preparation of two novel 8-substituted 7-(diethylamino)coumarin dyes. The photophysical study of these fluorophores has enabled us to highlight their remarkable aggregation-induced emission (AIE) properties characterized by a yellow-orange emission of aggregates in water. Therefore, 4-(tert butyldimethylsilyloxy)benzyl substituent was identified as a novel AIE-active moiety which could be seen as a possible alternative to popular tetraphenylethylene (TPE).

Reinvestigation of the Synthesis of "Covalent-Assembly" Type Probes for Fluoride Ion Detection. Identification of Novel 7-(Diethylamino)coumarins with Aggregation-Induced Emission Properties

An unprecedented C-3 functionalization of 4-(diethylamino)salicylaldehyde through a Friedel-Crafts type alkylation reaction has been discovered during the synthesis of "covalent-assembly"-based fluorescent probes for detection of fluoride ions. The resulting Friedel-Crafts adduct was successfully used for the preparation of two novel 8-substituted 7-(diethylamino)coumarin dyes. The photophysical study of these fluorophores has enabled us to highlight their remarkable aggregation-induced emission (AIE) properties characterized by a yellow-orange emission of aggregates in water. Therefore, 4-(tert butyldimethylsilyloxy)benzyl substituent was identified as a novel AIE-active moiety which could be seen as a possible alternative to popular tetraphenylethylene (TPE).

3-Benzyl-5,5-diphenylimidazolidine-2,4-dione

The asymmetric unit of the title compound, C22H18N2O2, consists of two independent molecules differing primarily in the orientation of the benzyl substituent. The two independent molecules are associated through complementary C—H...π interactions and are elaborated into corrugated sheets by paired N—H...O and C—H...O hydrogen bonds. Additional C—H...O hydrogen bonds bind the sheets together.

A cinnamaldehyde Schiff base ofS-(4-methylbenzyl) dithiocarbazate: crystal structure, Hirshfeld surface analysis and computational study

The title dithiocarbazate ester (I), C18H18N2S2[systematic name: (E)-4-methylbenzyl 2-[(E)-3-phenylallylidene]hydrazinecarbodithioate, comprises an almost planar central CN2S2residue [r.m.s. deviation = 0.0131 Å]. The methylene(tolyl-4) group forms a dihedral angle of 72.25 (4)° with the best plane through the remaining non-hydrogen atoms [r.m.s. deviation = 0.0586 Å] so the molecule approximates mirror symmetry with the 4-tolyl group bisected by the plane. The configuration about both double bonds in the N—N=C—C=C chain isE; the chain has an alltransconformation. In the crystal, eight-membered centrosymmetric thioamide synthons, {...HNCS}2, are formedviaN—H...S(thione) hydrogen bonds. Connections between the dimersviaC—H...π interactions lead to a three-dimensional architecture. A Hirshfeld surface analysis shows that (I) possesses an interaction profile similar to that of a closely related analogue with anS-bound benzyl substituent, (II). Computational chemistry indicates the dimeric species of (II) connectedviaN—H...S hydrogen bonds is about 0.94 kcal mol−1more stable than that in (I).