Search results for "bond"
showing 10 items of 3527 documents
ESI-FTICR investigation of triethylammonium ion-driven resorcin[4]arene dimer formation and structure
2002
In the course of mass spectrometric measurements a self-assembled hydrogen bonded resorcinarene dimer was observed, the formation of which was driven by the binding of triethylammonium ion as a guest and as an ionic label.
Exploring the 2,2′-Diamino-5,5′-bipyrimidine Hydrogen-Bonding Motif: A Modular Approach to Alkoxy-Functionalized Hydrogen-Bonded Networks
1998
The programmed self-association of 2,2’-diamino-4,4’-dialkoxy-5,5’-bipyrimidines allows for the de novo construction of alkoxy-functionalized H-bonded ribbons and sheets as evidenced by X-ray crystallographic analysis. The data provide insight into the interplay of the different structural and interactional features of the molecular components to the generation of the supramolecular assembly. Hydrophobicity of the didodecyl side chains of 4c leads to the dominance of the H-bonding factor, resulting in the formation of a fully interconnected array. These results define the utility of the of 2,2’-diamino-4,4’-dialkoxy-5,5’-bipyrimidines as a potential scaffold for the attachment of electro- o…
Lennard-Jones Parameters for B3LYP/CHARMM27 QM/MM Modeling of Nucleic Acid Bases.
2015
Combined quantum mechanics/molecular mechanics (QM/MM) methods allow computations on chemical events in large molecular systems. Here, we have tested the suitability of the standard CHARMM27 forcefield Lennard-Jones van der Waals (vdW) parameters for the treatment of nucleic acid bases in QM/MM calculations at the B3LYP/6-311+G(d,p)-CHARMM27 level. Alternative parameters were also tested by comparing the QM/MM hydrogen bond lengths and interaction energies with full QM [B3LYP/6-311+G(d,p)] results. The optimization of vdW parameters for nucleic acid bases is challenging because of the likelihood of multiple hydrogen bonds between the nucleic acid base and a water molecule. Two sets of optim…
Protonated malonate: the influence of the hydrogen bonds on the magnetic behaviour
2004
One hydrogen malonato-bridged complex of formula [Cu(Hmal)2] (1) and two polymorphous malonato-bridged complexes of formula [Cu(H2O)(H2mal)(mal)] (2 and 3), in which the three species of the malonate (H2mal, Hmal−, and mal2−) are present, were synthesised and characterized by X-ray diffraction [H2mal = malonic acid]. Their structures consist of corrugated malonate layers of [Cu(Hmal)2] (1) and [Cu(H2O)(H2mal)(mal)] (2 and 3) units bridged by carboxylate–malonate groups. The layers are linked through hydrogen bonds leading to a three-dimensional network. Variable-temperature (1.9–290 K) magnetic susceptibility measurements indicate the occurrence of weak ferromagnetic interactions between th…
Self-assembly by co-ordination and strong hydrogen bonding. X-ray crystal structures of a dimeric trisodium complex of a new acidic complexing ligand…
1993
Abstract The new acidic complexing ligand triethanolamine-O,O,O-triacetic acid, 3, is synthesized by reaction of triethanolamine with chloroacetic acid in the presence of sodium tert-butoxide. The resulting Na complex, 4, and its dihydrate, 5, contain two ligand molecules, both with one Na+ ion interaction and both co-ordinated to a third, central, Na+ ion. In addition the acidic ligands are hydrogen bonded to each other, like carboxylic acids, and in 4, by three crystallographically symmetric hydrogen bonds, while in 5, due to the breakdown of symmetry, two normal and one crystallographically symmetrical hydrogen bond. Inside this extraordinary dimeric assembly (a pseudo-cryptate) are the …
Hydrogen bonded calixarene capsules kinetically stable in DMSO.
2002
Half-life times up to 4 days in DMSO at room temperature are observed for the decomposition of dimeric capsules of urea substituted calix[4]arenes held together by a combination of hydrogen bonds, mechanical entanglement and cation–π interactions.
Hydrophobic interactions and stacking forces: A convenient model system
1980
Abstract We consider solvent–biomolecule interactions and the role of solvent structural and isotopic alterations on the thermodynamic stability of biomolecular structures. Approaches to this problem range from the study of biomolecular functional stability, to that of the stability of small structural entities suitable of being taken as model systems for (parts of) larger molecules. We shall focus on this latter case and shall consider the dimerization process of small planar molecules (Methylene Blue). These are a convenient model system for the study of interactions responsible e.g. for base stacking in DNA. As an additional advantage, they do not form hydrogen bonds. The experimental st…
"Comment on ""Non-symmetric substituted ureas locked in an (E,Z) conformation: an unusual anion binding via supramolecular assembly"" by M. Olivari, …
2014
We propose another point of view on the type of hydrogen bonded complexes that were described in this journal (M. Olivari et al., New J. Chem., 2013, 37, 663). The main difference is the molecular geometry and breakage of the intramolecular hydrogen bond during association. The current comment is to highlight mentioned aspects and to point out that in some cases the interpretation may not be straightforward due to the simultaneous effects associated with complexation.
3-Oxa-6,8-diaza-1,2:4,5-dibenzocycloocta-1,4-dien-7-one: a three-dimensional network assembled by hydrogen-bonding, pi-pi and edge-to-face interactio…
2003
The title compound, C(13)H(10)N(2)O(2), is the first structure in which the urea moiety is incorporated into an eight-membered ring. Two molecules are found in the asymmetric unit, which are almost identical in their conformation and their hydrogen-bond pattern. The carbonyl O atom acts as a double acceptor for the NH groups of two adjacent molecules. In this way, infinite tapes are formed, which are connected via pi-pi and edge-to-face interactions in the second and third dimension. This hierarchical order of interactions is confirmed by molecular mechanics calculations. Force-field and semi-empirical calculations for a single molecule did not find the envelope conformation present in the …
Assembly and encapsulation of coordination tectons driven by hydrogen-bondingand space-filling
2001
[FR] Le composé ¿Fe(LI)3¿2¿Fe(H2O)6¿(ClO4)6 (2), LI = 1,10-phénanthroline-5,6-dione, a été synthétisé et caractérisé. La structure cristalline 2 est définie par un assemblage bidimensionnel non covalent, peu commun, constitué par des tectons chiraux ¿Fe(LI)3¿2+, assemblés par des cations ¿Fe(H2O)6¿2+ encapsulés dans des cages. Ces cages sont formées par 12 liaisons hydrogène établies entre les molécules d¿eau coordinées et les groupes dione appartenant à six molecules chirales ¿Fe(LI)3¿2+ ¿, ¿ alternées.