8,681 research outputs found

    Towards Putting the ‘P’ in Perovskite: Exploring the Reactivity of Phosphonium Salts with Group 14 Halides

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    Inorganic/organic hybrid perovskites have emerged as synthetic materials that exhibit light-harvesting properties. Although perovskites with alkylammonium cations have been previously reported, a perovskite family with phosphonium cations has not been investigated. Firstly, a library of phosphonium salts was made with the intention of further reaction with the group 14 halides towards creating a perovskite crystal. The composition of these salts were elucidated via NMR spectroscopy, and the crystal structures of three of the phosphonium salts were determined. The phosphonium iodide salts were then reacted with the lead, tin, and germanium iodides and bromides to discover if variant perovskitic structures are obtained. The reaction of lead(II) iodide with various phosphonium salts produced a charge-balanced network of PbI3- fragments connecting in a face-sharing octahedral motif. These phosphonium-templated iodoplumbates were found to possess semi-conducting properties, as suggested by the results of UV-Vis and their high thermal stability was confirmed by TGA experiments. Three novel crystal structures were isolated from reaction of phosphonium salts with tin(II) and tin(IV) iodide, each of them producing an iodostannate anion with a unique geometry. In a reaction with SnI4 an unpredictable oxidation of starting material produced a potentially Lewis acidic tin(IV) cation. Finally, the reaction of phosphonium salts with germanium(II) halides produced charge-balanced compounds with an ABX3 general formula that did not crystallize in a perovskitic manner. Germanium(IV) iodide formed a series of co-crystals when reacted with the phosphonium iodide salts. These species were found to form Ge-I‧‧‧‧I halogen-bonding interactions

    Selective functionalization of pyridines and diazines via nucleophilic addition to heterocyclic phosphonium salts

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    2018 Fall.Includes bibliographical references.Nitrogen heterocycles, specifically pyridines and pyrimidines, are common motifs found in pharmaceuticals, agrochemicals and materials. Site-selective functionalization of these azines are highly sought after for medicinal chemistry purposes. It has previously been found in our lab that heterocyclic phosphonium salts can potentially serve as a useful functional handle to selectively functionalize these valuable scaffolds. This work describes the utility of heterocyclic phosphonium salts as electrophiles to selectively form C-O, C-S, C-N and C-Se bonds in a diverse range of pyridines and diazines. First, the addition of thiolate nucleophiles to heterocyclic phosphonium salts to selectively form heteroaryl thioethers is described. This coupling reaction proceeds through deprotonation of the alkyl thiol followed by addition of the heterocyclic phosphonium salt under mild conditions. The reaction scope was tested for a variety of alkyl thiol nucleophiles as well as different pyridine phosphonium salts. The extent of the method's utility was demonstrated through late-stage functionalization of some complex pharmaceuticals. Additionally, initial results on the reactivity of sulfinate nucleophiles with heterocyclic phosphonium salts is communicated. Second, aromatic heteronucleophiles were explored for reactivity with heterocyclic phosphonium salts. Aromatic heteronucleophiles can be classified as either exocyclic or endocyclic. Exocyclic aromatic heteronucleophiles, such as phenols, thiophenols and anilines, were able to be selectively coupled to azines and pharmaceuticals. Endocyclic aromatic heteronucleophiles, such as pyrroles, pyrazoles and imidazoles, also proved to be compatible. All these nucleophiles were able to be coupled to complex drug-like fragments as well as other bioactive molecules via the phosphonium ion. The method also enabled a convergent coupling reaction between two elaborate coupling partners to form a novel tyrosine kinase inhibitor that would be difficult to access using conventional methods

    Radical-Mediated Anti-Markovnikov Hydrophosphonation of Olefins

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    The radical-mediated addition of triphenylphosphonium tetrafluoroborate to olefins (hydrophosphonation) is reported. Both standard radical initiators and photochemical conditions are effective, up to the gram scale. The phosphonium salts are shown to serve as Z-selective Wittig olefination reagents, even without purification

    Amide Synthesis through the In Situ Generation of Chloro- and Imido-Phosphonium Salts

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    We describe a methodology for the amidation of carboxylic acids by generating phosphonium salts in situ from N-chlorophthalimide and triphenylphosphine. Aliphatic, benzylic, and aromatic carboxylic acids can be transformed into their amide counter parts using primary and secondary amines. This functional group interconversion is achieved at room temperature in good to excellent yields. Mechanistic work shows the in situ formation of chloro- and imido-phosphonium salts that react as activating agents for carboxylic acids and generate an acyloxy-phosphonium species

    Triphenylarsonium-functionalised gold nanoparticles: potential nanocarriers for intracellular therapeutics.

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    This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.Two new triphenylarsonium alkylthiolate precursors, a thiosulfate zwitterion and a thioacetate salt, have been structurally characterised and their cytotoxicity evaluated against PC3 cells. The arsonium compounds have been used to prepare gold nanoparticles decorated with triphenylarsonium groups.Sheffield Hallam University and Indian Institute of Science (NL)

    Biological and structural studies of phosphonium 'masked thiolate' compounds

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    The ability of phosphonium cations to act as intracellular transport vectors is well-established. Phosphonioalkylthiosulfate zwitterions, and (omega)-thioacetylalkylphosphonium salts, which act as 'masked thiolate' ligands, are useful precursors for the formation of phosphonium-functionalised gold nanoparticles, enabling the nanoparticles to be transported into cells for diagnostic and therapeutic purposes. In this study we have completed cytotoxicity studies of (omega)-thioacetylpropylphosphonium salts derived from triphenylphosphine and tri(4-fluorophenyl)phosphine, which show that the compounds are only toxic towards PC3 prostate cancer cells at high concentrations and at prolonged incubation periods and display IC50 values of 67uM and 252uM respectively, significantly higher than those of other phosphonium salts. MALDI-TOF-MS has been used to investigate the uptake of the compounds by PC3 cells and to quantify detectable levels of the compounds inside the cells. The structures of (omega)-thioacetylpropyl(tri-4-fluorophenyl) phosphonium bromide and the corresponding tri(4-fluorophenyl)phosphonio-propylthiosulfate zwitterion have been investigated by single crystal X-ray crystallography. The results show that molecules of the zwitterion are held together through an extensive array of electrostatic and non-covalent interactions. The unit cell of (omega)-thioacetylpropyl(tri-4-fluorophenyl)phosphonium bromide contains eight cations together with eight bromide anions and two waters of crystallisation, all held together through a complex network of hydrogen bonds. The differences in the molecular packing of the two compounds may account for the lower solubility of the zwitterion in aqueous solutions, compared with that of the phosphonium salt

    Trypanocidal action of bisphosphonium salts through a mitochondrial target in bloodstream form Trypanosoma brucei

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    Lipophilic bisphosphonium salts are among the most promising antiprotozoal leads currently under investigation. As part of their preclinical evaluation we here report on their mode of action against African trypanosomes, the etiological agents of sleeping sickness. The bisphosphonium compounds CD38 and AHI-9 exhibited rapid inhibition of T. brucei growth, apparently the result of cell cycle arrest that blocked the replication of mitochondrial DNA, contained in the kinetoplast, thereby preventing the initiation of S-phase. Incubation with either compound led to a rapid reduction in mitochondrial membrane potential, and ATP levels decreased by approximately 50% within 1 h. Between 4 and 8 h, cellular calcium levels increased, consistent with release from the depolarized mitochondria. Within the mitochondria, the Succinate Dehydrogenase complex (SDH) was investigated as a target for bisphosphonium salts, but while its subunit 1 (SDH1) was present at low levels in the bloodstream form trypanosomes, the assembled complex was hardly detectable. RNAi knockdown of the SDH1 subunit produced no growth phenotype, either in bloodstream or in the procyclic (insect) forms and we conclude that in trypanosomes SDH is not the target for bisphosphonium salts. Instead, the compounds inhibited ATP production in intact mitochondria, as well as the purified F1 ATPase, to a level that was similar to 1 mM azide. Co-incubation with azide and bisphosphonium compounds did not inhibit ATPase activity more than either product alone. The results show that, in Trypanosoma brucei, bisphosphonium compounds do not principally act on succinate dehydrogenase but on the mitochondrial FoF1 ATPase

    Spontaneous dehydrocoupling in peri-substituted phosphine-borane adducts

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    This work was financially supported by the EPSRC and COST action CM1302 SIPs.Bis(borane) adducts Acenap(PiPr2·BH3)(PRH·BH3) (Acenap = acenaphthene-5,6-diyl; 4a, R = Ph; 4b, R = ferrocenyl, Fc; 4c, R = H) were synthesised by the reaction of excess H3B·SMe2 with either phosphino-phosphonium salts [Acenap(PiPr2)(PR)]+Cl− (1a, R = Ph; 1b, R = Fc), or bis(phosphine) Acenap(PiPr2)(PH2) (3). Bis(borane) adducts 4a–c were found to undergo dihydrogen elimination at room temperature, this spontaneous catalyst-free phosphine-borane dehydrocoupling yields BH2 bridged species Acenap(PiPr2)(µ-BH2)(PR·BH3) (5a, R = Ph; 5b, R = Fc; 5c, R = H). Thermolysis of 5c results in loss of the terminal borane moiety to afford Acenap(PiPr2)(µ-BH2)(PH) (14). Single crystal X-ray structures of 3, 4b and 5a–c are reported.Publisher PDFPeer reviewe

    Organic phosphonium salts

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    Crystalline structure and thermotropic behavior of alkyltrimethylphosphonium amphiphiles

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    Quaternary organophosphonium salts bearing long alkyl chains are cationic surfactants of interest owing to their physical and biological properties. In the present work, the crystal structure and thermotropic behavior of the homologous series of alkyltrimethylphosphonium bromides (nATMP·Br), with the alkyl chain containing an even number (n) of carbon atoms from 12 to 22, have been examined within the 0–300 °C range of temperatures. These compounds were shown to be resistant to heat up to ~390 °C. The phases adopted at different temperatures were detected by DSC, and the structural changes involved in the phase transitions have been characterized by simultaneous WAXS and SAXS carried out in real-time, and by polarizing optical microscopy as well. Three or four phases were identified for n = 12 and 14 or n = 16, respectively, in agreement with the heat exchange peaks observed by DSC. The phase existing at room temperature (Ph-I) was found to be fully crystalline and its crystal lattice was determined by single-crystal X-ray diffraction methods. Ph-II consisted of a semicrystalline structure that can be categorized as Smectic-B with the crystallized ionic pairs hexagonally arranged in layers and the molten alkyl chain confined in the interlayer space. Ph-II of 12ATMP·Br and 14ATMP·Br directly isotropicized upon heating at ~220 °C, whereas for n = 16, it converted into a Smectic-A phase (Ph-III) that needed to be heated above ~240 °C to become isotropic (Ph-Is). The correlation existing between the thermal behavior, phase structure and length of the alkyl side chain has been demonstrated.Peer ReviewedPostprint (published version
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