Hydrogen-bonded frameworks of bis(2-carboxypyridinium) hexafluorosilicate and bis(2-carboxyquinolinium) hexafluorosilicate dihydrate

Abstract

In bis(2-carboxypyridinium) hexafluorosilicate, 2C(6)H(6)NO(2)+.SiF6(2-), (I), and bis(2-carboxyquinolinium) hexafluorosilicate dihydrate, 2C(10)H(8)NO(2)+.SiF6(2-).2H2O, (II), the Si atoms of the anions reside on crystallographic centres of inversion. Primary inter-ion interactions in (I) occur via strong N-H...F and O-H...F hydrogen bonds, generating corrugated layers incorporating [SiF6](2-) anions as four-connected net nodes and organic cations as simple links in between. In (II), a set of strong N-H...F, O-H...O and O-H...F hydrogen bonds, involving water molecules, gives a three-dimensional heterocoordinated rutile-like framework that integrates [SiF6](2-) anions as six-connected and water molecules as three-connected nodes. The carboxyl groups of the cation are hydrogen bonded to the water molecule [O...O = 2.5533 (13) A], while the N-H group supports direct bonding to the anion [N...F = 2.7061 (12) A].

Hexafluorosilicates of bis(carboxypyridinium) and bis(2-carboxyquinolinium)

“…In spectrum for IV the complicated bands in the range 3420-3125 cm À1 can be assigned to the n(OH) vibrations of water molecules involved in the system of H-bonding (upfield components 3420, 3310, 3205 cm À1 ), and n(N + H) vibrations for protonated quinoline-2-carbonic acid (preferred contribution in the downfield component at 3125 cm À1 ). The presence of fuzzy absorption bands in the spectra I-IV in the field of 2720-2525 cm À1 can be assigned to strong interionic OHÁ Á ÁF hydrogen bonds [9,10]. In the field of 800-650 cm À1 (Table 4) vibrations is in agreement with the X-ray data indicating the distortion of the octahedral geometry of the [SiF 6 ] 2À anion in I-IV due to interionic hydrogen bonds.…”

“…In continuation of our previous examinations on relationship between structure and properties of ''onium'' hexafluorosilicates the preparation, spectral data, thermochemical transformations and solubility of salts of three isomeric bis(carboxypyridinium) hexafluorosilicates (I-III) and bis(2-carboxyquinolinium) hexafluorosilicate (IV) are described alongside with the crystal structure of bis(4-carboxypyridinium) hexafluorosilicate (III). The structural characteristics for hexafluorosilicates of the general formula (LH) 2 [SiF 6 ]ÁnH 2 O (L = 2-, 3-carboxypyridine, n = 0; L = 2-carboxyquinoline, n = 2) have been reported earlier [9,10].…”

Determination of thermodynamic and transport properties of solvents and non solvents in poly(L‐lactide‐co‐glycolide)

“…It has been already reported that noncovalent Si … F interactions can stabilize fluoroalkylated rod‐like polysilanes 31. In addition, it is well known that traditional organic salts such as pyridinium, aminopyridinium, carboxyquinolinium, diisopropylammonium, phenylammonium, N ‐methylpiperidine betaine, and acridinium salts can interact with hexafluorosilicate anion to have two‐ and three‐dimensional framework topologies through the strong H … F hydrogen bonds 32–39. Hexafluorosilicate anions obtained in the nanocomposite reactions in the presence of guest molecules such as CPC and bisphenol AF would afford the synergistic interactions derived from not only hydrogen bonding interaction between the fluorines in hexafluorosilicate and hydrogen atoms in the guest molecules but also noncovalent Si … F interactions between the silica gel in the composites and hexafluorosilicate, and such effective interactions should enable encapsulated CPC and bisphenol AF to exhibit a perfectly nonflammable characteristic at 800 °C.…”

UV resistance of encapsulated low molecular weight aromatic compounds in fluoroalkyl end‐capped trimethoxyvinylsilane oligomer/silica nanocomposites

“…Thus, in our present sol–gel reactions of R F ‐(VM) n ‐R F oligomer in the presence of BINOL and HMB, of whose compounds possess phenol‐type acidic protons, under the similar alkaline conditions, the smooth dehydrofluorination of the phenol‐type acidic protons in BINOL and HMB with fluorines in R F ‐(VM) n ‐R F oligomer catalyzed by both ammonia and silica nanoparticle units in oligomer would proceed, and hydrogen fluoride thus obtained can react with silica nanoparticle units in oligomer to afford ammonium hexafluorosilicate. Hitherto, traditional organic compounds such as pyridinium and phenylammonium salts are well known to interact with hexafluorosilicate anion to have two‐ and three‐dimensional framework topologies through the strong H … F hydrogen bonds . Hexafluorosilicate anions obtained in the nanocomposite reactions in the presence of BINOL or HMB would afford the synergistic interactions derived from not only hydrogen bonding interaction between the fluorines in hexafluorosilicate and hydrogen atoms in these guest molecules but also noncovalent Si … F interactions derived from the silica nanoparticle units in oligomer and hexafluorosilicate, and such synergistically effective interactions should afford not only a nonflammable characteristic but also an excellent UV resistance toward BINOL and HMB in the nanocomposite matrices.…”