Search results for " Hydrogen Bonding"
showing 10 items of 27 documents
From self-inclusion and host-guest complexes to channel structures
2012
Various supramolecular interactions are applied as driving forces in self-assembly and molecular recognition processes. Single crystal X-ray diffraction method is especially important for solid-state studies of non-covalent interactions as it reveals their influence on the molecular and supramolecular structures. This paper discusses structures of two completely different types of compounds in which a variety of intermolecular interactions are involved. It will be shown that strong and weak intermolecular hydrogen bonds in N-alkylammonium resorcinarene salts, depending on the type of anion, inclusion of resorcinarene upper rim pendant group or solvent molecules into the cavity, strongly aff…
Primary- and secondary-octahedral distortion factors in bis(1,4-H2-1,2,4-triazolium) pentabromidoantimonate(III) –1,4-H2-1,2,4-triazolium bromide
2015
Abstract The analysis of octahedral distortion in the structure of inorganic–organic (C2H4N3)2[SbBr5]·(C2H4N3)Br (BTPTB) bromidoantimonate(III) determined at 295 and 85 K, supported by the Hirshfeld surface analysis and the data retrieved from the Cambridge Structural Database, is presented. The anionic substructure of BTPTB is built from distorted [SbBr6]3− octahedra that are connected by the cis corners forming polymeric one-dimensional [{SbBr5}n]2n− zig-zag chains running parallel to the a axis and isolated Br− ions. The organic substructure consists of the fully ordered 1,4-H2-1,2,4-triazolium cations. The oppositely charged substructures are linked by the system of N(C)–H⋯Br hydrogen b…
Naturally occurring polyphenols as building blocks for supramolecular liquid crystals – substitution pattern dominates mesomorphism
2021
A modular supramolecular approach towards hydrogen-bonded liquid crystalline assemblies based on naturally occurring polyphenols is reported. The combination of experimental observations, crystallographic studies and semi-empirical analyses of the assemblies provides insight into the structure–property relationships of these materials. Here a direct correlation of the number of donor OH-groups as well as their orientation with the mesomorphic behavior is reported. We discovered that the number and orientation of the OH-groups have a stronger influence on the mesomorphic behavior of the supramolecular assemblies than the connectivity (e.g. stilbenoid or chalconoid) of the hydrogen bond donor…
Binding Modes of Nonspherical Anions to N-Alkylammonium Resorcinarenes in the Solid State
2012
A series of hydrogen bond stabilized N-alkylammonium resorcinarene salts with nitrate, triflate, and picrate as the counteranions were synthesized and characterized with 1H NMR and electrospray ionization (ESI) mass spectrometry. Together with electrostatic interactions, the binding of the anions with several hydrogen bond donor sites proceeds through a complex array of intra- and intermolecular hydrogen bonds, evidenced by single crystal X-ray diffraction analysis. These N-alkyl ammonium resorcinarenes bind the larger nonspherical anions into deformed cavitand-like structures and enforce a transformation of the resorcinarene conformation from almost symmetrical to extremely distorted.
Hydrogen bond-stabilised N-alkylammonium resorcinarene halide cavitands
2010
A family of hydrogen bond-stabilised N-alkylammonium resorcinarene chloride and bromide cavitands were synthesised and characterised with 1H NMR and ESI mass spectrometry. The seven compounds exhibit interestingly either self-inclusion or guest complexation in the solid state evidenced by single crystal X-ray diffraction. The four dimers show self-inclusion of the upper rim propyl chains and consist of two hydrogen-bonded resorcinarene tetracations and six halide anions, while the remaining two halide anions are located in between the dimers linking them via hydrogen bonding. Small solvent molecules such as dichloromethane, methanol, n-butanol or chloroform are complexed into the resorcinar…
Solubility and solvation features of native cyclodextrins in 1-ethyl-3-methylimidazolium acetate
2022
The comprehension of the mechanism entailing efficient solvation of cyclodextrins (CD) by green solvents is of great relevance to boost environmentally sustainable usages of smart supramolecular systems. Here, 1-ethyl-3- methylimidazolium acetate, an ecofriendly ionic liquid (IL), is considered as an excellent solvent for native CDs. This IL efficiently dissolves up to 40 wt.% β- and γ-CD already at ambient temperature and X-ray scattering indicates that CDs do not tend to detrimental flocculation under these drastic concentration conditions. Simu- lation techniques reveal the intimate mechanism of CD solvation by the ionic species: while the strong hydrogen bonding acceptor acetate anion i…
Conformational analysis of α,β-dehydropeptide models at the HF and DFT levels
2004
Abstract The Ramachandran potential energy surfaces of N-acetyl-α,β-dehydroamino acid N′-monomethylamides Ac-ΔXaa-NHMe (ΔXaa=ΔAla, (Z)-ΔPhe; 1, 2) and N-acetyl-α,β-dehydroamino acid N′,N′-dimethylamides Ac-ΔXaa-NMe2 (ΔXaa=ΔAla, (Z)-ΔPhe, (Z)-ΔAbu; 3–5) were calculated at the HF/6-31G*//HF/3-21G level. The conformers localised were fully optimised at the DFT/B3LYP/6-31+G** level and their relative stabilities were analysed in terms of both π-conjugation and internal hydrogen bonding. The Ac-ΔXaa-NMe2 molecules reveal the low-energy conformer H/F, φ=−41±4°, ψ=128±4°, which is not too easily accessible for common amino acid residues. This conformer is stabilised by the bifurcated N2–CH3 O1 int…
Oleochemical carbonates: A comprehensive characterization of an emerging class of organic compounds
2022
Dialkyl carbonates (DAC) with short-medium alkyl length - oleochemical carbonates – are attracting attention because of their appealing properties, including low viscosity, flammability, toxicity, environ- mental impact and wide range of applications: lubricants, personal care, fuel additives etc. However, not much is known concerning their chemical physical properties and, more importantly, on the nature of microscopic correlations that eventually determine bulk performances. In view of this paucity, we pre- sent a large exploration of a series of chemical physical properties of a set of DACs ranging from dimethyl up to didodecyl carbonate. This study extends previously determined database…
Structure and vibrational features of the protic ionic liquid 1,8-diazabicyclo[5.4.0]-undec-7-ene-8-ium bis(trifluoromethanesulfonyl)amide, [DBUH][TF…
2022
Abstract The Protic Ionic Liquid (PIL) formed by neutralization of the super-strong base 1,7-diazabicyclo[5.4.0]undec-7-ene (DBU) with the super-strong acid bis(trifluoromethanesulfonyl)-imide (TFSI), indicated as [DBUH][TFSI], has been investigated. Its chemical physical properties and structural features have been explored using a synergy of experimental and computational tools. Molecular Dynamics-rationalised X-ray diffraction patterns highlight the major role played by hydrogen bonding (HB) in affecting morphology in this PIL. A comparison between HB features in this and in related PILs has been presented, on the base of far-IR experiments and DFT analysis. Indications of a weaker HB in…
Halogenido ligand exchange synthesis, spectroscopic properties and thermal behaviour of the inorganic–organic hydrogen-bonded network solid [4,4′-H2b…
2014
Abstract Dark-red single crystals of 4,4′-bipyridinium triaquahydrogen(1+) hexabromidorhodate(III) [4,4′-H2bipy][H7O3][RhBr6] (1) have been synthesized by a diffusion-controlled ligand exchange process from rhodium(III) chloride trihydrate and 4,4′-bipyridine dissolved in hydrochloric and hydrobromic acid, respectively. 1 could be considered as an inorganic–organic hydrogen-bonded network solid built up from the inorganic isolated hexabromidorhodate [RhBr6]3− octahedra, organic 4,4′-bipyridinium(2+) [4,4′-H2bipy]2+ and triaquahydrogen(1+) [H7O3]+ cations with nearly symmetrical O⋯O distances. The oppositely charged components in the structure of 1 are bound together by an intricate system o…