Chalkogenbrücken: eine Übersicht

Abstract

In den letzten Jahrzehnten haben sich “unübliche” nichtkovalente Wechselwirkungen wie Anion‐π oder Halogenbrücken in vielen Forschungsbereichen zu interessanten Alternativen zu den allgegenwärtigen Wasserstoffbrücken entwickelt. Dies trifft – zu einem etwas geringeren Grad – auch auf Chalkogenbrücken zu, die nichtkovalenten Wechselwirkungen Lewis‐acider Chalkogenzentren. Dieser Kurzaufsatz soll einen Überblick über den Einsatz von Chalkogenbrücken in der kondensierten Phase geben, mit einem Fokus auf den neuesten Entwicklungen bei der Anwendung intermolekularer Chalkogenbrücken in Lösung. Im Festkörper wurden Chalkogenbrücken zum Aufbau nanoskaliger Strukturen und für die Selbstorganisation ausgefeilter selbstkomplementärer Komplexe verwendet. Bis vor kurzem konzentrierten sich die Anwendungen in Lösung vor allem auf intramolekulare Wechselwirkungen, welche die Konformation von Intermediaten oder Reagentien stabilisierten. In den letzten Jahren wurden nun aber auch intermolekulare Chalkogenbrücken zunehmend in Lösung eingesetzt, besonders für Anionenerkennung und ‐transport sowie in der organischen Synthese und der Organokatalyse.

Fluorescent Flippers: Small‐Molecule Probes to Image Membrane Tension in Living Systems

“…The original flipper probes such as Flipper‐TR® 5 are DTT [22, 38–40] dimers twisted out of co‐planarity due to methyl groups next to the single bond connecting the two monomers (Figure 2). The molecular electrostatic potential (MEP) [41] surface of flipper 5 in planar conformation ( p ) shows that flipper deplanarization does not originate from steric hindrance but from electrostatic repulsion between the methyls and the σ holes [42–49] on the endocyclic sulfur atoms (Figure 1). This repulsion represents the opposite of a chalcogen bond, [42–49] that is “repulsive chalcogen bonding” or an “anti‐chalcogen bond” (Figure 2).…”

“…The molecular electrostatic potential (MEP) [41] surface of flipper 5 in planar conformation ( p ) shows that flipper deplanarization does not originate from steric hindrance but from electrostatic repulsion between the methyls and the σ holes [42–49] on the endocyclic sulfur atoms (Figure 1). This repulsion represents the opposite of a chalcogen bond, [42–49] that is “repulsive chalcogen bonding” or an “anti‐chalcogen bond” (Figure 2). The mechanosensitivity of flipper probes is designed to originate from planarization by physical compression.…”

A Quantitative Molecular Orbital Perspective of the Chalcogen Bond

“…The chalcogen-bond (ChB) is the net-attractive intermolecular interaction, often referred to as noncovalent interaction, between a Lewis-basic chalcogen-bond acceptor A and a Lewisacidic chalcogen-bond donor D 2 Ch featuring a chalcogen (group 16) atom Ch to which A binds. [1] Nearly 40 years ago, the first systematic study appeared of the chalcogen bond in which S•••Y (e. g., Y = S, O, F, Cl, or Br) nonbonded atomic contacts were investigated. [2] Early studies generally characterized chalcogen bonds as being predominantly electrostatic in nature.…”

“…[3] Later on, the significance of charge transfer from the occupied orbital of a Lewis base into an empty σ*-type orbital of a chalcogen molecule controlling the chalcogen bond strength was recognized. [4] Chalcogen-bonding has since found applications in various fields of chemistry, [1] including, supramolecular, [5] biochemistry, [6] spectroscopy [7] and catalysis. [8] In this study, we have computationally analyzed a range of chalcogen-bonded D 2 Ch•••A À complexes (Ch = O, S, Se, Te; D, A = F, Cl, Br; see Scheme 1), using relativistic density functional theory (DFT) at ZORA-M06/QZ4P.…”

Chalcogen Bonding Catalysis of the Cloke‐Wilson Rearrangement

“…Chalcogen bonding operates through the weak interaction between an electron donor and the chalcogen centre of a molecular entity, [11–12] representing a subclass of σ‐hole interactions [13] . Chalcogen bonding phenomenon was initially observed in the crystal structures of proteins and small organic molecules that contain disubstituted chalcogen fragments [14–17] .…”