Efficient Colorimetric Fluoride Anion Sensor Based on π-Conjugated Carbazole Small Molecule

The ability to detect fluoride anions with high selectivity and sensitivity by using the naked eye is crucial yet challenging. In this study, a novel, simple conjugated organic dye, N-tert-butyldimethylsilyl-3,6-diiodocarbazole (CA-TBMDS) was developed and used for the first time as a colorimetric sensor for fluoride. CA-TBMDS was found to be a highly sensitive fluoride chemosensor, with a detection limit as low as 3 × 10−5 M. The reaction of CA-TBMDS with fluoride anions in a tetrahydrofuran solution resulted in a color change from colorless to yellow under ambient light, which can be discriminated by the naked eye. The sensor operated via intermolecular proton transfer between the amide units and the fluoride anion, as confirmed by proton nuclear magnetic resonance titration. CA-TBMDS is not only highly sensitive to fluoride anions, but also exhibits high sensitivity in the presence of various ions. This work demonstrates that N-butyldimethylchlorosilane-based organic dyes have prospective utility as a type of fluoride anion chemosensor.

Application of Monopotassium Dipropylene Glycoxide for Homopolymerization and Copolymerization of Monosubstituted Oxiranes: Characterization of Synthesized Macrodiols by MALDI-TOF Mass Spectrometry

Monopotassium dipropylene glycoxide, activated by a 18-crown-6 cation complexing agent (K-DPG/L, where DPG (dipropylene glycol) is a mixture of isomers) was used as an effective initiator of the homopolymerization and copolymerization of several monosubstituted oxiranes, i.e., propylene oxide (PO), 1.2-butylene oxide (BO), and some glycidyl ethers such as allyl, isopropyl, phenyl, and benzyl ones (AGE, IPGE, PGE, and BGE, respectively). The copolymers are novel and can be prospectively used for the fabrication of new thermoplastic or crosslinked polyurethanes. All processes were carried out in homogeneous mild conditions, i.e., tetrahydrofuran solution at room temperature and normal pressure. They resulted in new unimodal macrodiols with Mn = Mcalc in the range of 1500–8300, low dispersity Mw/Mn = 1.08–1.18 and a chemical structure well defined by several techniques, i.e., MALDI-TOF, size exclusion chromatography (SEC), 13C NMR, and FTIR. Monopotassium salts of homopolyether-diols, i.e., PPO-diol, PBO-diol, and PAGE-diol, appeared to be useful macroinitiators for the preparation of new triblock copolyether-diols by polymerization of glycidyl ethers. In BO/BGE random copolymerization initiated with K-DPG/L, macromolecules of copolyether-diol were exclusively formed. Macromolecules of copolyether-diol accompanied by homopolyether PPO-diol were identified in the PO/PGE system. However, AGE and PGE reacted by giving random copolyether-diol as well as homopolymer-diols, i.e., PAGE-diol and PPGE-diol. Macromolecules of prepared copolyether-diols contain various numbers of mers deriving from comonomers; the kind of comonomer determines the composition of the product. Several prepared homopolyether-diols and copolyether-diols could be useful for the synthesis of new thermoplastic polyurethanes.

Application of cesium hydroxide monohydrate for ring opening polymerization of monosubstituted oxiranes: characterization of synthesized polyether-diols

Cesium hydroxide monohydrate (CsOH·H2O) activated by cation complexing agents, i.e., 18C6 or C222 was applied as initiator of monosubstituted oxiranes polymerization. Propylene oxide (PO), 1,2-butylene oxide (BO), styrene oxide (SO) and some glycidyl ethers were used as monomers. All processes were carried out in tetrahydrofuran solution at room temperature. Such polymers, as PPO-diols, PBO-diols and PSO-diols, are unimodal and have molar masses Mn = 2000–5100. Their dispersities are rather high (Mw/Mn = 1.17–1.33). Moreover, PPO-diols and PSO-diols are not contaminated by monools with unsaturated starting groups. Poly(glycidyl ether)s are, in general, polymodal. For example, poly(isopropyl glycidyl ether)-diols are bi- or trimodal, whereas poly(allyl glycidyl ether)-diols possess two or even six fractions. Molar masses of main fraction are 4200–6400, and the second fraction is much lower, namely 600–2600. Dispersities of some fractions are very low (Mw/Mn = 1.01–1.07). Polymodality of polymers obtained was discussed in terms of the formation of two or more species propagating with different rate constants. Graphic abstract

New way of anionic ring-opening copolymerization of β-butyrolactone and ε-caprolactone: determination of the reaction course

Poly(ε-caprolactone)-block-poly(β-butyrolactone) copolymers were prepared in two-step synthesis. Firstly, poly(ε-caprolactone) (PCL) was obtained by anionic ring-opening polymerization of CL initiated with anhydrous KOH activated 12-crown-4 cation complexing agent. Reaction was carried out in tetrahydrofuran solution and argon atmosphere at room temperature. Then, β-butyrolactone (BL) and 18-crown-6 were added to the system, resulting in PCL-block-PBL copolymer, which contains after methylation hydroxyl starting group and methyl ester end group. The main product was contaminated with PCL and PBL homopolymers formed in a side reactions. 13C NMR technique was used for determination of chemical structure of polymers obtained. The course of the studied processes was proposed. MALDI-TOF technique was used to reveal the macromolecules’ architecture where several series were found. The identified series shown that mainly copolymeric macromolecules were formed with scare contribution of homopolymeric polybutyrolactone with trans-crotonate starting groups and polycaprolactone, which is congruent with the proposed reaction mechanism. Moreover, critical approach concerning previously reported PCL-block-PBL copolymer synthesis by use of NaH as initiator was also presented.

The Photocatalytic Degradation of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin in the Presence of Silver–Titanium Based Catalysts

Polychlorinated dibenzo-p-dioxins (PCDD) are persistent toxic compounds that are ubiquitous in the environment. The photodegradation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the presence of silver titanium oxide (AgTi) and silver titanium doped into the Y-zeolite (AgTiY) was tested using high (254 nm) and mid (302 nm) energy UV irradiation sources. AgTi and AgTiY, both showed success in the photodegradation of 2,3,7,8-TCDD dissolved in methanol/tetrahydrofuran solution. Both catalysts were found to effectively decompose TCDD at 302 nm (lower energy) reaching in between 98–99% degradation after five hours, but AgTiY showed better performance than AgTi at 60 min reaching 91% removal. Byproducts of degradation were evaluated using Gas chromatography/mass spectrometry (GC–MS), resulting in 2,3,7-trichlorodibenzo-p-dioxin, a lower chlorinated congener and less toxic, as the main degradation product. Enzyme Linked Immunosorbent Assay (ELISA) was used to evaluate the relative toxicity of the degradation byproducts were a decrease in optical density indicated that some products of degradation could be potentially more toxic than the parent TCDD. On the other hand, a decrease in toxicity was observed for the samples with the highest 2,3,7,8-TCDD degradation, confirming that AgTiY irradiated at 302 nm is an excellent choice for degrading TCDD. This is the first study to report on the efficiency of silver titanium doped zeolites for the removal of toxic organic contaminants such as dioxins and furans from aquatic ecosystems.

DETERMINATION OF DISSOCIATION STAGE OF GAS HYDRATES BASED ON THE ANALYSIS OF NMR RELAXOMETRY METHOD DATA

A model of synthetic gas hydrates in a mixture of quartz pellets is considered using by tetrahydrofuran solution based on distilled water. The analysis of the NMR-characteristics of tetrahydrofuran hydrate in clayed sand is performed. The stages of hydrate dissociation excluding water contribution are established and it is shown that the NMR-relaxometry method is sensitive to the clay content. The obtained results allow us to more detailed study the processes of hydrate formation in real reservoir rocks and their physical characteristics.

The synthesis and crystal structure of bis[3,3-diethyl-1-(phenylimino-κN)thiourea-κS]silver hexafluoridophosphate

The structure of the title complex, [Ag(C11H15N3S)2]PF6, has monoclinic (P21/c) symmetry, and the silver atom has a distorted square-planar geometry. The coordination complex crystallized from mixing silver hexafluoridophosphate with a concentrated tetrahydrofuran solution of N,N-diethylphenylazothioformamide [ATF; systematic name: 3,3-diethyl-1-(phenylimino)thiourea] under ambient conditions. The resultant coordination complex exhibits a 2:1 ligand-to-metal ratio, with the silver(I) atom having a fourfold AgN2S2 coordination sphere, with a single PF6 counter-ion. In the crystal, however, one sulfur atom from an ATF ligand of a neighboring complex coordinates to the silver atom, with a bond distance of 2.9884 (14) Å. This creates a polymeric zigzag chain propagating along the c-axis direction. The chains are linked by C—H...F hydrogen bonds, forming slabs parallel to the ac plane.

STUDYING OF THE PROPERTIES OF CLAYED HYDRATE-CONTAINING SAMPLES USING HEAVY WATER BY THE DATA OF NMR RELAXOMETRY METHOD

A model of synthetic hydrates in a mixture of quartz pellets with kaolin clay is considered using by tetrahydrofuran solution based on distilled water and heavy water. The dissociation of tetrahydrofuran is investigated under atmospheric pressure. The analysis of the NMR-characteristics of tetrahydrofuran hydrate in a clayed sand is performed. The stages of hydrate dissociation excluding water contribution are established and it is shown that the NMR-relaxometry method is sensitive to the clay content. The obtained results allow us to simulate the processes of hydrate formation in real rocks and study their physical characteristics.