Topic
Hydrogen bond
About: Hydrogen bond is a research topic. Over the lifetime, 57701 publications have been published within this topic receiving 1306326 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: This tutorial review highlights recent developments in host-guest chemistry based on the use of neutral and cationic CH hydrogen bond donors and various structural classifications, including alkyl CH, phenyl CH, triazole-based CH, imidazolium (CH)(+) and triazolio-basedCH hydrogen bond donor systems.
Abstract: The design and synthesis of anion selective receptors and chemosensors continues to attract considerable interest within the supramolecular community. In recent years, increasing attention has focused on the use of neutral and cationic CH hydrogen bond donors as anion recognition elements. Over the last five years, motifs that support CH⋯X (X = anion) hydrogen bonds have been actively used in various shape persistent macrocycles, foldamers and “molecular machines”. This tutorial review highlights recent developments in host–guest chemistry based on the use of neutral and cationic CH hydrogen bond donors. Also discussed are various structural classifications, including alkyl CH, phenyl CH, triazole-based CH, imidazolium (CH)+ and triazolium (CH)+ hydrogen bond donor systems.
176 citations
TL;DR: Insight is provided into the structural characteristics of complexes involving heterocyclic bases and carboxylic acids, and X-ray crystallography and 15N solid-state NMR are truly complementary in elucidating hydrogen bonding interactions and the degree of proton transfer of these complexes.
Abstract: A cancer candidate, compound 1, is a weak base with two heterocyclic basic nitrogens and five hydrogen-bonding functional groups, and is sparingly soluble in water rendering it unsuitable for pharmaceutical development. The crystalline acid−base pairs of 1, collectively termed solid acid−base complexes, provide significant increases in the solubility and bioavailability compared to the free base, 1. Three dicarboxylic acid−base complexes, sesquisuccinate 2, dimalonate 3, and dimaleate 4, show the most favorable physicochemical profiles and are studied in greater detail. The structural analyses of the three complexes using crystal structure and solid-state NMR reveal that the proton-transfer behavior in these organic acid−base complexes vary successively correlating with ΔpKa. As a result, 2 is a neutral complex, 3 is a mixed ionic and zwitterionic complex and 4 is an ionic salt. The addition of the acidic components leads to maximized hydrogen bond interactions forming extended three-dimensional networks....
176 citations
TL;DR: Theoretical ab initio calculations were carried out to simulate the hydrolysis of the siloxane bond under neutral and acidic conditions in this article, where the most important factors reducing the energy barrier of the reaction are the protonation of the nucleophile (acid catalysis) and the basic assistance provided by hydrogen bond complexes, which help to transfer a proton from a nucleophile to the leaving group.
176 citations
TL;DR: Water molecules at binding sites bridge the protein and ligand, and interact with other water molecules to form a complex network of interconnecting hydrogen bonds that are probably crucial for the stability of the protein-ligand complex.
Abstract: Water is known to play an important role in the recognition and stabilization of the interaction between a ligand and its site. This has important implications for drug design. Analyses of 19 high-resolution crystal structures of protein-ligand complexes reveal the multiple hydrogen-bonding feature of water molecules mediating protein-ligand interactions. Most of the water molecules (nearly 80%) involved in bridging the protein and the ligand can make three or more hydrogen bonds when distance and bond angles are used as criteria to define hydrogen-bonding interactions. Isotropic B-factors have been used to take into account the mobility of water molecules. The water molecules at binding sites bridge the protein and ligand, and interact with other water molecules to form a complex network of interconnecting hydrogen bonds. Some water molecules at the site do not directly bridge between the protein and the ligand, but may contribute indirectly to the stability of the complex by holding bridging water molecules in the right position through a network of hydrogen bonds. These water networks are probably crucial for the stability of the protein-ligand complex and are important for any site-directed drug design strategies.
176 citations
TL;DR: Intermolecular hydrogen bonding of acidic alcohols to the hydride ligand of WH(CO)2(NO)L2 (L = PMe3), PEt3 (2), P(OiPr)3 (3), PPh3 (4)) has been observed and characterized by IR and NMR spectroscopy in hexane, toluene-d8, and CD2Cl2 solutions as mentioned in this paper.
Abstract: Intermolecular hydrogen bonding of acidic alcohols (PhOH, (CF3)2CHOH (HFIP), (CF3)3CHOH (PFTB)) to the hydride ligand of WH(CO)2(NO)L2 (L = PMe3 (1), PEt3 (2), P(OiPr)3 (3), PPh3 (4)) has been observed and characterized by IR and NMR spectroscopy in hexane, toluene-d8, and CD2Cl2 solutions. The H-bonding is an equilibrium process with medium −ΔH° of 4.1−6.9 kcal/mol; the enthalpy increases on going from 4 to 1, i.e., the strongest bonding is found for the smallest and the most basic L = PMe3. The value of −ΔH° depends on the pKa of the proton donors, increasing as the acidity does (PhOH < HFIP < PFTB). The IR and NMR data suggest C2v symmetry around tungsten in the ROH···HW(CO)2(NO)L2 adduct, with the H···H distance of 1.77 A (L = PMe3) estimated from the hydride T1min relaxation time. The relevance of the hydrogen bonding to the mechanism of protonation of metal hydrides is suggested.
176 citations