Ashwani Vij

Nonporous Organic Solids Capable of Dynamically Resolving Mixtures of Diiodoperfluoroalkanes

Halogen bonding has increasingly facilitated the assembly of diverse host-guest solids. Here, we show that a well-known class of organic salts, bis(trimethylammonium) alkane diiodides, can reversibly encapsulate α,ω-diiodoperfluoroalkanes (DIPFAs) through intermolecular interactions between the hosts I– anions and the guests terminal iodine substituents. The process is highly selective for the fluorocarbon that forms an I–···I(CF2)mI···I– superanion that is matched in length to the chosen dication. DIPFAs that are 2 to 12 carbons in length (common industrial intermediates) can thereby be isolated from mixtures by means of crystallization from solution upon addition of the dissolved size-matched ionic salt. The solid-state salts can also selectively capture the DIPFAs from the vapor phase, yielding the same product formed from solution despite a lack of porosity of the starting lattice structure. Heating liberates the DIPFAs and regenerates the original salt lattice, highlighting the practical potential for the system in separation applications.

Fluorinated Polyhedral Oligomeric Silsesquioxanes (F-POSS)†

Abstract : Partical contents: Hybrid Inorganic/Organic Polymers, Anatomy of a POSS Nanostructure, Poss Synthesis, FluoroPOSS Synthesis, Fluoropropyl(nTn), Fluorodecyl(8T8), Contact Angle of Water on Fluorodecyl POSS Surface, Contact Angle of Mercury on Fluorodecyl POSS Surface, AFM Image of Spin-Cast Fluorodecyl(8T8) Surface, Surface Energy of Fluorosiloxanes, Contact Angle and Chain Length, POSS Polymer Incorporation, Importance of R groups: Affect compatibility with polymer matrix, PVDF/Fluoroocytl(8T8) POSS,PVDF/Fluoroocytl(nTn) POSS, Fluorinated Ethylene/Propylene, Poly(chlorotrifluoroethylene), Amorphous FEP, Water Contact Angle.

Sapphyrin Supramolecules through C−H⋅⋅⋅S and C−H⋅⋅⋅Se Hydrogen Bonds—First Structural Characterization of meso- Arylsapphyrins Bearing Heteroatoms

An unprecedented coupling reaction of heteroatom-containing tripyrranes leads to the formation of core-modified sapphyrins 1 and 2, which self-assemble in the solid state to form supramolecular ladders. Weak C-H⋅⋅⋅S and C-H⋅⋅⋅Se hydrogen-bonding interactions in addition to C-H⋅⋅⋅N hydrogen bonds are responsible for the observed structures.

Solid state synthesis under supramolecular control of a 2D heterotetratopic self-complementary tecton tailored to halogen bonding

We describe the synthesis and characterization, by single crystal X-ray analysis, of a 1D heteroditopic self-complementary tecton for halogen bonding. It was designed to also incorporate double bonds and to possess heteropolar π–π stacking groups in order to carefully control its supramolecular organization in the solid state. As a result of this supramolecular control, by UV irradiation in the solid state the compound dimerizes forming a 2D heterotetratopic self-complementary tecton tailored to halogen bonding based self-assembly. This 2D tecton crystallizes clathrating chloroform molecules.

Some fluorine-containing nitrogen acids and their derivatives

Abstract Fluorine-containing nitrogen acids and their derivatives are highly useful compounds in a variety of applications. For example, the acids find practical use as electrolytes or additives for electrolytes in fuel cells, the lithium salt of (CF 3 SO 2 ) 2 NH is being developed for use in batteries, polymeric nitrogen acid electrolytes have been prepared, and the N -fluoro derivatives of some of the nitrogen acids are the most useful electrophilic fluorinating agents available. The first XeN bond was prepared using (FSO 2 ) 2 NH. Interest in these materials has been increasing rapidly over the last 10 years because of the large number of applications in which their physical and chemical properties make them suitable candidates for study.

Facile synthesis of hydrophobic fluoroalkyl functionalized silsesquioxane nanostructures

New fluorinated polyhedral oligomeric silsesquioxane (F-POSS) structures possessing a high degree of hydrophobicity have been prepared via a facile corner-capping methodology.

Durch C−H⋅⋅⋅S- und C−H⋅⋅⋅Se-Brücken stabilisierte Sapphyrin-Supermoleküle – erste strukturelle Charakterisierung von Heteroatome enthaltenden meso-Arylsapphyrinen

Eine unerwartete Kupplungsreaktion heterosubstituierter Tripyrrane lieferte die Sapphyrin-Analoga 1 und 2, die im Kristall supramolekulare Leitern bilden. Schwache C−H⋅⋅⋅S- bzw. C−H⋅⋅⋅Se-Brucken sind neben den ublicheren C−H⋅⋅⋅N-Brucken entscheidend fur das Auftreten dieser Strukturen.

Weak intermolecular interactions and molecular aggregation in isostructural dihaloperfluoroethanes

A series of 1,2-dihalotetrafluoroethanes X(CF2)2X (X = Br, I) has been in-situ pressure crystallized in a diamond-anvil cell (DAC), their structures determined by single crystal X-ray diffraction and rationalized by weak intermolecular interactions. For isoelectronic and isostructural 1,2-dibromotetrafluoroethane (BrCF2CF2Br), 1,2-diiodotetrafluoroethane (ICF2CF2I) and 1-bromo-2-iodotetrafluoroethane (BrCF2CF2I), the crystals are monoclinic, space groupP21/n, with the midpoint of the C–C bond located at the centre of inversion. The freezing pressures of these compounds have been determined to be 0.80 GPa, 0.30(5) GPa and 0.10(5) GPa for BrCF2CF2Br, BrCF2CF2I and CF2ICF2I, respectively. In the structure of ICF2CF2I, the –CF2–CF2– moiety is orientationally disordered at 0.16 GPa, but it becomes ordered at 0.86 GPa; in the BrCF2CF2I crystal the Br and I atoms are substitutionally disordered; and the BrCF2CF2Br structure is completely ordered. The formation of isostructural crystals by these compounds and different types of molecular disorder can be rationalized by the intermolecular interactions at varied thermodynamical conditions. The phenomenon of “self-healing” has been observed, in which crystal defects, formed during initial crystallization in the DAC, repaired themselves during the annealing process, which greatly facilitates the formation of single crystals. Pressure considerably affects the crystal morphology of ICF2CF2I, where the elimination of –CF2–CF2– disorder coincides with the appearance of dendritic forms of the crystal phases.

Liquid azide salts.

Ionic liquid azides from azidoethyl, alkyl, and alkenyl substituted derivatives of 1,2,4- and 1,2,3-amino-triazoles were prepared and examined for the first time to investigate their structural and physical properties. All reported salts possess melting points below 100 degrees C. The unique character of these newly discovered ionic liquid azides is based upon the fact that these molecules are not simple protonated salts like previously reported substituted hydrazinium azides. The presence of quaternary nitrogen confers both thermal stability and negligible volatility.

Crystal structures of bis(4-dimethylaminopyridinium) tetrachlorocobaltate(II) and bis-[1,3-di (ammoniummethyl)benzene]tetrachlorocobaltate(II)

The crystal structures consist of organoammonium cations hydrogen bonded to tetrahedral CoCl42− anions. In the 4-dimethylaminopyridinium salt, [(CH3)2NC5H5NH]2CoCl4, pairs of cations hydrogen bond in an asymmetric fashion to two of the chlorines in each anion. The planar cations form two sets of π–π stacks, first parallel to the a axis and the second parallel to the b axis. The anions lie between these two nonintersecting sets of stacks. In contrast, for the second compound, [C6H4(CH2NH3)2]CoCl4, the tetrahedral CoCl42− anions form layers lying parallel to the bc plane. The 1,3-di(ammoniummethyl)benzene cations crosslink adjacent anionic layers, forming a lamellar structure of alternating organic and inorganic layers.