Search results for " hydrogen bonds"
showing 10 items of 19 documents
Intrinsic fluorescence in non-aromatic peptide structures is induced by collective vibrations, charge reorganisation and short hydrogen bonds, as sho…
2020
Abstract Disentangling the origin of the optical activity of non-aromatic proteins is challenging due to their size and thus their high computational requisites. Here we show, in a much smaller model system, that the single amino acid glutamine undergoes a chemical transformation leading to an unreported glutamine-like structure which has a similar broad absorption spectrum reported previously for non-aromatic proteins. We further show computationally that the optical activity of the glutamine-like structure is directly coupled to short-hydrogen bonds, but also displays charge and vibrational fluctuations, the latter of which are also present in less optically active structures such as in L…
Crystal structure of 2-methyl-1H-imidazol-3-ium hydrogen oxalate dihydrate
2016
In the title molecular salt 2-methyl-1H-imidazol-3-ium hydrogen oxalate dihydrate, N—H⋯(O,O) and O—H⋯O hydrogen bonds link the components into a bilayer-like assembly.
Crystal structure and Hirshfeld surface analysis of dimethyl (1R*, 3aS*, 3a(1)R*, 6aS*, 9R*, 9aS*)-3a(1),5,6,9a-tetrahydro-1H,4H,9H-1,3a:6a,9-diepoxy…
2019
The title diepoxyphenalene derivative, C17H18O6, comprises a fused cyclic system containing four five-membered rings (two dihydrofuran and two tetrahydrofuran) and one six-membered ring (cyclohexane). The five-membered dihydrofuran and tetrahydrofuran rings adopt envelope conformations, and the six-membered cyclohexane ring adopts a distorted chair conformation. Two methyl carboxylate groups occupy adjacent positions (2- and 3-) on a tetrahydrofuran ring. In the crystal, two pairs of C-H center dot center dot center dot O hydrogen bonds link the molecules to form inversion dimers, enclosing two R-2(2)(6) ring motifs, that stack along the a-axis direction and are arranged in layers parallel …
Simple Rules for Complex Near-Glass-Transition Phenomena in Medium-Sized Schiff Bases
2022
Glass-forming ability is one of the most desired properties of organic compounds dedicated to optoelectronic applications. Therefore, finding general structure–property relationships and other rules governing vitrification and related near-glass-transition phenomena is a burning issue for numerous compound families, such as Schiff bases. Hence, we employ differential scanning calorimetry, broadband dielectric spectroscopy, X-ray diffraction and quantum density functional theory calculations to investigate near-glass-transition phenomena, as well as ambient- and high-pressure molecular dynamics for two structurally related Schiff bases belonging to the family of glycine imino esters. Firstly…
(E)-1-(1,3-Benzodioxol-5-yl)-3-(2,4,5-trimethoxyphenyl)prop-2-en-1-one
2017
The molecule of the title compound C19H18O6, adopts anEconformation about the C=C double bond and the C—C=C—C torsion angle is −179.30 (16)°. The molecule is nearly planar, as indicated by the dihedral angle of 6.99 (6)° between the benzene ring and the benzodioxalane ring. In the crystal, molecules are linkedviaweak C—H...O hydrogen bonds, forming zigzag chains propagating along thebaxis.
Bioconjugates of 1’-Aminoferrocene-1-carboxylic Acid with (S)-3-Amino-2-methylpropanoic Acid and L-Alanine
2010
Formal CH 2 insertion in bioconjugates composed of 1'-aminoferrocene-1-carboxylic acid (Fca) and alanine Boc-Ala-Fca-Ala-OCH 3 gives Fca bioconjugates with the β-amino acid (S)-3-amino-2-methylpropanoic acid (Aib). The novel homologous conjugates of ferrocene were fully characterized by spectroscopic and analytical methods. NMR, CD and IR spectroscopy in concert with DFT calculations suggest that the formal "L-Ala-to-(S)-β-Aib mutations" can exert ferrocene helix inversion due to the different stereogenic carbon atoms of L -Ala and (S)-β-Aib. Furthermore, the mutation (de-)stabilizes the conserved secondary structure with two intramolecular hydrogen bonds, depending on the "mutation site". …
Crystal structure of 2-(adamantan-1-yl)-5-(4-bromophenyl)-1,3,4-oxadiazole
2014
In the title molecule, C18H19BrN2O, the benzene ring is inclined to the oxadiazole ring by 10.44 (8)°. In the crystal, C—H...π interactions link the molecules in a head-to-tail fashion, forming chains extending along thec-axis direction. The chains are further connected by π–π stacking interactions, with centroid–centroid distances of 3.6385 (7) Å, forming layers parallel to thebcplane.
The Molecular and Crystal Structure of tert-Butyl N.ALPHA.-tert-Butoxycarbonyl-L-(S-trityl)cysteinate and the Conformation-Stabilizing Function of We…
2001
The title compound, C31H37NO4S [systematic name: (R)-tert-butyl-2-[(tert-butoxycarbonyl)amino]-3-(tritylsulfanyl)propanoate] is an L-cysteine derivative with three functions: NH2, COOH and SH, blocked by protecting groups tert-butoxycarbonyl, tert-butyl and trityl, respectively. The main chain of the molecule adopts the extended, nearly all-trans C5 conformation with the intramolecular N-H...O=C hydrogen bond. The urethane group is not involved in any intermolecular hydrogen bonding. Only weak intermolecular hydrogen bonds and hydrophobic contacts are observed in the crystal structure. These are C-H...O hydrogen bonds and CH/pi interactions with donor...acceptor distances, C...O ca. 3.5 A a…
Crystal structure of 2-{[1-(2-methyl-5-nitro-1H-imidazol-1-yl)propan-2-yloxy]carbonyl}benzoic acid
2014
In the title compound, C15H15N3O6, the dihedral angle between the planes of the benzene and imidazole rings is 34.93 (10)°. An intramolecular C—H...O hydrogen bond is observed. In the crystal, O—H...N hydrogen bonds link the molecules into chains parallel to thecaxis.
Crystal structure and Hirshfeld surface analysis of (E)-4-chloro-N-{2-[2-(4-nitrobenzylidene)hydrazin-1-yl]-2-oxoethyl}benzenesulfonamide N,N-di…
2018
Reaction of N-(4-chlorobenzenesulfonyl)glycinyl hydrazide with 4-nitrobenzaldehyde gives the N,N-dimethylformamide monosolvated N-acylhydrazone derivative, (E)-N-{2-[2-(4-nitrobenzylidene)- hydrazine-1-yl]-2-oxoethyl}-4-χhlorobenzenesulfonamide. Rings of (10) and (11) graph-set motifs are formed in the crystal structure by N—H⋯O and C—H⋯O hydrogen bonds. The two-dimensional fingerprint (FP) plots for significant intermolecular interactions indicate that the greatest contribution is from the O⋯H/H⋯O contacts (31.3%), corresponding to N⋯H⋯O/C⋯H⋯O interactions.