Multicompartmentalized polymersomes for selective encapsulation of biomacromolecules

Multicompartmentalized polymersomes are formed using block co-polymers PMOXA-PDMS-PMOXA and PS-PIAT, and are subsequently proven to be capable of selective encapsulation of biomacromolecules. This architecture mimics the compartmentalization found in cells and may serve as a simple, albeit robust, model system.     

Fabrication of all-inorganic nanocrystal solids through matrix encapsulation of nanocrystal arrays

A general strategy for low-temperature processing of colloidal nanocrystals into all-inorganic films is reported. The present methodology goes beyond the traditional ligand-interlinking scheme and relies on encapsulation of morphologically defined nanocrystal arrays into a matrix of a wide-band gap semiconductor, which preserves optoelectronic properties of individual nanoparticles while rendering the nanocrystal film photoconductive. Fabricated solids exhibit excellent thermal stability, which is attributed to the heteroepitaxial structure of nanocrystal-matrix interfaces, and show compelling light-harvesting performance in prototype solar cells.     

Interaction between biphenols and anions: selective receptor for dihydrogenphosphate

Biphenol was shown to bind dihydrogenphosphate (H2PO4-) selectively over various other anions (MeCO2-, Cl-, Br-, I-, NO3-, HSO4-). The highly selectivity of biphenol toward dihydrogenphosphate is explained in terms of the basicity and shape of the guest anion.     

Self-assembled metalla-bowls for selective sensing of multi-carboxylate anions

Two new tetranuclear cationic metalla-bowls 4 and 5 were self-assembled from a bis-pyridine amide ligand (H(2)L) (1) and arene-ruthenium acceptors, [(Ru(2)(μ-η(4)-C(2)O(4))(η(6)-p-cymene)(2)](O(3)SCF(3))(2) (2) and [Ru(2)(dhnd)(η(6)-p-cymene)(2)](O(3)SCF(3))(2) (dhnd = 6,11-dihydroxy-5,12-naphthacenedionato) (3), respectively. The metalla-bowls were characterized by multinuclear NMR, ESI-MS, UV-Vis spectroscopy, and single crystal X-ray diffraction study of 4. The crystal structure of 4 reveals unambiguous proof for the molecular shape of the metalla-bowl and the encapsulation of one triflate anion in the cavity through hydrogen bonding. The metalla-bowl 5 has been evaluated for anion binding studies by use of amide ligand as a hydrogen bond donor and arene-Ru acceptor as a signalling unit. UV-Vis titration studies showed that 5 selectively binds with multi-carboxylate anions such as oxalate, tartrate and citrate in a 1?:?1 fashion with high binding constants of 4.0-5.5 × 10(4) M(-1). Furthermore, the addition of multi-carboxylate anions into a solution of 5 gave rise to a large enhancement of fluorescence intensity attributable to the blocking of a photo-induced electron transfer process from the arene-ruthenium moiety to the amidic donor in 5. However, the fluorescence intensity almost remains unchanged upon addition of other anions including F(-), Cl(-), PF(6)(-), MeCOO(-), NO(3)(-) and PhCOO(-), as identically seen in the UV-Vis titration experiments, pointing to the high selectivity of 5 for the sensing of multi-carboxylate anions.     

Dimerization of the allylzinc cation: selective coupling of allyl anions in a metallo-ene reaction

Metal assistance: Dimerization of the allylzinc monocation gives the dimetalated coupling product in quantitative yield. Kinetic and thermodynamic parameters of this reversible metallo-ene reaction have been determined. This reaction serves as a model system for the alkali-metal catalyzed production of 4-methylpentene.     

Self-assembled arene-ruthenium-based rectangles for the selective sensing of multi-carboxylate anions

Novel arene-ruthenium [2+2] metalla-rectangles 4 and 5 have been synthesized by self-assembly using dipyridyl amide ligand 3 and arene-ruthenium acceptors (arene: benzoquinone (1), naphthacenedione (2)) and characterized by NMR spectroscopy and ESI-MS. The solid-state structure of 5 was determined by X-ray diffraction and shows encapsulated diethyl ether molecule in the rectangular cavity of 5. The luminescent 5 was further used for anion sensing with the amidic linkage serving as a hydrogen-bond donor site for anions and the ruthenium moiety serving as a signaling unit. A UV/Vis titration study demonstrated that although 5 interacts very weakly with common monoanions as well as with flexible dicarboxylate anions such as malonate and succinate, it displays significant binding affinity (K>10(3) in MeOH) for rigid multi-carboxylate anions such as oxalate, citrate, and tartrate, exhibiting a 1:1 stoichiometry. It has been suggested that 1:1 bidentate hydrogen bonding assisted by appropriate geometrical complementarity is mainly responsible for the increased affinity of 5 towards such anions. A fluorescence titration study revealed a large fluorescence enhancement of 5 upon binding to multi-carboxylate anions, which can be attributed to the blocking of the photoinduced electron-transfer process from the arene-Ru moiety to the amidic donor in 5 as a result of hydrogen bonding between the donor and the anion.     

Naked eye detection of anions by alkynyl-ruthenium exo-receptors: selective recognition of fluoride anion

Alkynyl-ruthenium complexes bearing terminal hydrogen-bonding receptors act as efficient anion sensors exhibiting large guest-induced colour changes and show unexpectedly high selectivity to fluoride ions.     

Unexpected solids from enantiopure cationic palladium complexes and racemic anions: A structural study of chiral non-discrimination

Enantiomerically pure cationic complexes were obtained via cyclopalladation of primary amines and subsequent addition of a chelating ethylendiamine ligand. No diastereomeric resolution was observed upon combining these cations with racemic mandelate or hydratropate anions, but four less popular products, namely three double salts and a solid solution, were obtained and structurally characterized. For one of the double salts, the alternative ionic compounds based on different stereoisomers of the same residues were synthesized independently: The conventional racemic solid and both diastereomeric salts formed by enantiopure cations and anions were studied by single crystal X-ray diffraction. Lattice energy calculations confirm that the diastereomeric salts differ significantly; formation of the partially racemic double salt, however, is energetically favourable and precludes resolution.     

Ion chromatography with the selective adsorption of anions during the analysis

A method of the selective removal of certain anions from the eluate in an ion chromatographic experiment (the adsorption column method) is proposed for the qualitative and quantitative determination of the removed anions and/or coeluted unadsorbed sample components. The method is suitable for some complex cases of anion analysis (F–/IO₃^- Cl–/NO₂^-) using a METROHM ion chromatograph.     

An anthracene based bispyridinium amide receptor for selective sensing of anions

A new receptor has been designed and synthesized for selective recognition of anions through hydrogen bonding and electrostatic interactions. The recognition ability has been studied by fluorescence, UV-vis and ¹H NMR spectroscopic methods. The results demonstrate that the receptor exhibits good recognition ability towards anions and shows strong binding to AcO⁻, and F⁻.     

Ester-armed cyclens having quadruplicated helical geometry: remarkably stable and selective encapsulation of Na+ ion

A new series of ester-armed cyclens nicely accommodated a Na+ ion in their quadruplicated helical binding spheres and effectively discriminated the cation from Li+ and K+ ions. Crystallographic studies revealed that four ester-functionalized sidearms provided effective coordination with the Na+ ion trapped in the 12-membered cyclen ring. Log K values for their Na+ complexes were estimated as 9-11 in CD3CN or C2D5OD, which were comparable to those of common bicyclic cryptands. FAB-MS, liquid-liquid extraction, and NMR binding experiments demonstrated that the cooperative action of the parent cyclen ring and ester-functionalized sidearms offered stable and selective encapsulation of the Na+ ion based on unique quadruplicated helical geometry.     

A quinoline based bis-urea receptor for anions: a selective receptor for hydrogen sulfate

A dipodal bis-urea receptor has been synthesized from the reaction of 8-amino quinoline and 1,4-phenylene diisocyanate in dichloromethane, and the anion binding ability of the receptor has been studied using fluoride, chloride, bromide, iodide, perchlorate, nitrate, dihydrogen phosphate and hydrogen sulfate by UV-Vis titrations in DMSO. The results show that the receptor binds each of the anions with a 1:1 stoichiometry, showing high affinity and moderate selectivity for hydrogen sulfate among the anions studied. Ab initio calculations based on density functional theory (DFT) suggest that an anion (X(-)) is bonded within the cleft formed by the two arms of the receptor through two NH...X(-) and two aromatic CH...X(-) interactions. The results from solution and theoretical studies suggest that binding is predominantly influenced by hydrogen bonding interactions and the basicity of anions.     

Development of colorimetric receptors for selective discrimination between isomeric dicarboxylate anions

Three new chromogenic receptors (1, 2, and 3) containing p-nitrophenyl or p-nitronaphthyl group appended to the thiourea units or containing p-nitrophenyl group appended to the urea moiety were synthesized and characterized. Upon addition of a series of isomeric dicarboxylate anions to receptor 1 in DMSO/H₂O (80:20 v/v), the appearance of the solution of receptor 1 with maleate or phthalate showed color changes from blue to green or blue to dark-green, respectively, which those can be detected by naked eye at parts per million. Similar experiments were repeated using 2, the solution showed a distinct color change from blue to pink only when 2 is formed as a complex with maleate. Whereas, the addition of the same isomeric dicarboxylate anions to receptor 3, did not induce any color change. Thus, for unique color change, both receptors 1 and 2 can act as optical chemosensors for recognition of maleate versus fumarate. In addition, the receptor 1 can also be a colorimetric receptor for selective discrimination between aromatic isomeric dicarboxylate anions.     

Synthesis of colorimetric sensors for isomeric dicarboxylate anions: selective discrimination between maleate and fumarate

Four new colorimetric receptors (1-4) were synthesized and characterized. Upon addition of maleate to receptor in DMSO, the appearance of the solution of receptor 1 showed a color change from dark-blue to dark-red, which can be detected by the naked eye at parts per million. Similar experiments were repeated using receptors 2-4; the solution showed a distinct color change from blue to violet for receptor 2 and from blue-green to purple for both receptors 3 and 4, when they are formed as complexes with maleate. The striking color changes are thought to be due to the deprotonation of the thiourea moiety of the 4-nitronaphthyl chromophore. Whereas, in the addition of fumarate to receptors 1-4, the color of the solution changed from dark-blue to bright yellow for receptor and did not induce any color change for receptors 2-4. Thus, for a distinct color change, receptors 1-4 can act as optical chemosensors for recognition of maleate versus fumarate. Especially, only receptor 1 has a unique color change for the recognition of fumarate, accordingly it can be used for detection of the fumarate anion. In this research it was also found that the performance of the receptor is highly dependent on the substituent group on the phenyl ring; a stronger electron-withdrawing group resulted in a receptor with a higher binding constant with the maleate anion.     

A selective chromogenic molecular sensor for acetate anions in a mixed acetonitrile-water medium

Quinonehydrazone compound , as a new chromogenic anion sensor, can selectively detect AcO(-) over F(-) and other anions in mixed acetonitrile-water media. The deprotonation of the N-H proton of the sensor is responsible for the drastic color change. An acidic C-H group in the receptor, probably acting as an accessorial binding site, is essential to the selectivity and affinity for sensing the acetate anions.     

Controlled diastereoselectivity at the alkene-geometry through selective encapsulation: E-Z photoisomerization of oxazolidinone-functionalized enecarbamates within hydrophobic nano-cavities

Photoisomerization of encapsulated Z-enecarbamates within the hydrophobic chiral cavities of gamma-CD showed higher diastereoselectivities in the photoproducts than those obtained in solution. The selective encapsulation of the enecarbamates and the following isomerization process are both diastereoselectively controlled by gamma-CD.     

A selective synthesis of hydroxyborate anions as novel anchors for zirconocene catalysts

A new family of hydroxytris(pentafluorophenyl)borate anions [B(C6F5)3OH](-) associated with organic and aprotic cations c+ (imidazolium, pyrrolidinium and phosphonium) has been prepared by a general one-pot synthesis that implies the chloride borate analogues [B(C6F5)3Cl](-)[c]+. The [c]+[B(C6F5)3OH](-) salts have been isolated and fully characterized. The borate anion [B(C6F5)3OH](-) has been shown to protonate the Zr-Me bond in the Cp2ZrMe2 complex forming CH4 and the first published example of anionic [Cp2Zr(Me)OB(C6F5)3](-) species. Standard spectroscopic methods demonstrate the covalent character of the Zr metal center and the anionic character of the boron atom. This protonolysis methodology using [B(C6F5)3OH](-) anion affords a new route for the incorporation of a covalently bonded anionic functionality on organometallic complexes. This provides a new way to immobilize transition metal complexes in ionic liquids.