The hydrogen bond is the most important of all directional intermolecular interactions. It is operative in determining molecular conformation, molecular aggregation, and the function of a vast number of chemical systems ranging from inorganic to biological. Research into hydrogen bonds experienced a stagnant period in the 1980s, but re-opened around 1990, and has been in rapid development since then. In terms of modern concepts, the hydrogen bond is understood as a very broad phenomenon, and it is accepted that there are open borders to other effects. There are dozens of different types of X-H.A hydrogen bonds that occur commonly in the condensed phases, and in addition there are innumerable less common ones. Dissociation energies span more than two orders of magnitude (about 0.2-40 kcal mol(-1)). Within this range, the nature of the interaction is not constant, but its electrostatic, covalent, and dispersion contributions vary in their relative weights. The hydrogen bond has broad transition regions that merge continuously with the covalent bond, the van der Waals interaction, the ionic interaction, and also the cation-pi interaction. All hydrogen bonds can be considered as incipient proton transfer reactions, and for strong hydrogen bonds, this reaction can be in a very advanced state. In this review, a coherent survey is given on all these matters.

The hydrogen bond in the solid state.

The coordination chemistry of pyrazole-derived ligands

Aromaticity as a cornerstone of heterocyclic chemistry.

Die Wasserstoffbrucke ist die wichtigste der gerichteten intermolekularen Wechselwirkungen. Sie spielt fur die molekulare Konformation, Aggregation und Funktion einer grosen Anzahl chemischer Systeme, die vom anorganischen bis zum biologischen Sektor reichen, wichtige Rollen. Die Forschung uber Wasserstoffbrucken stagnierte in den 1980er Jahren, wurde um 1990 aber wieder belebt und ist seither in schneller Bewegung. Die Wasserstoffbrucke wird heute als ein sehr breites Phanomen mit offenen Grenzen zu anderen Effekten begriffen. In den kondensierten Phasen gibt es dutzende Arten von haufig vorkommenden X−H⋅⋅⋅A-Wasserstoffbrucken und zusatzlich sehr viele weniger haufige Typen. Die Dissoziationsenergien uberstreichen mehr als zwei Grosenordnungen (etwa 0.2 bis 40 kcal mol−1). Innerhalb dieses Bereiches ist die Natur der Wechselwirkung nicht konstant, sondern ihre elektrostatischen, kovalenten und dispersiven Anteile variieren in ihren relativen Beitragen. Die Wasserstoffbrucke hat breite Ubergangsbereiche zur kovalenten Bindung, zur Van-der-Waals-Wechselwirkung, zur ionischen Wechselwirkung und zur Kation-π-Wechselwirkung. Wasserstoffbrucken konnen als beginnende Protonentransferreaktion aufgefasst werden, und fur starke Wasserstoffbrucken kann diese Reaktion bereits in einem fortgeschrittenen Stadium sein. In diesem Aufsatz wird versucht, einen zusammenhangenden Uberblick uber alle diese Aspekte zu geben.

Die Wasserstoffbrücke im Festkörper

https://cyberleninka.org/article/n/1038964.pdf

Biological activities of curcuminoids, other biomolecules from turmeric and their derivatives – A review

Synthesis and physicochemical studies on 1,2‐bisazolylethanes

Rhodium(I) complexes with bis(pyrazolyl)methane ligands. Crystal structure of [Rh(COD)(CH2(Pz)2)]ClO4· C2H4Cl2

Publisher Summary This chapter deals mainly with aromatic systems, describes the concept of heteroaromaticity, and considers the aromaticity of heteropentalenes, particularly azapentalenes. Azapentalenes can be broadly defined as the heterocyclic analogs of pentalene which are aromatic by virtue of a 10- Π -electron system, and compounds of this type can thus be iso- Π -electronic with the pentalene dianion. Methods of synthesis, chemical reactivity, and spectroscopic properties of azapentalenes are also presented. The chapter concludes with a brief discussion on azapentalenes industrial uses and their biological activities. In specific, type A azapentalenes systems behave as two separate aromatic rings, as there is lack of interaction between the two parts. Type B azapentalenes behave as one ring, but the aromatic character in certain systems is more localized in the ring that lacks the heteroatom X. Only type C azapentalenes can accurately be represented by a delocalized Π -system extending over both rings. Certain benzo derivatives of type B and C systems behave as a benzene ring and a heteroaromatic ring joined by a bridge.

The Chemistry of Aromatic Azapentalenes

Synthesis and biological evaluation of curcuminoid pyrazoles as new therapeutic agents in inflammatory bowel disease: Effect on matrix metalloproteinases

J. Elguero

Papers

Synthesis and physicochemical studies on 1,2‐bisazolylethanes

Rhodium(I) complexes with bis(pyrazolyl)methane ligands. Crystal structure of [Rh(COD)(CH2(Pz)2)]ClO4· C2H4Cl2

The Chemistry of Aromatic Azapentalenes

Synthesis and biological evaluation of curcuminoid pyrazoles as new therapeutic agents in inflammatory bowel disease: Effect on matrix metalloproteinases

Les benzazoles (indazole, benzimidazole, benzotriazole) structure moleculaire et proprietes fondamentales