The Chalcogen Bond in Crystalline Solids: A World Parallel to Halogen Bond

Abstract

Conspectus The distribution of the electron density around covalently bonded atoms is anisotropic, and this determines the presence, on atoms surface, of areas of higher and lower electron density where the electrostatic potential is frequently negative and positive, respectively. The ability of positive areas on atoms to form attractive interactions with electron rich sites became recently the subject of a flurry of papers. The halogen bond (HaB), the attractive interaction formed by halogens with nucleophiles, emerged as a quite common and dependable tool for controlling phenomena as diverse as the binding of small molecules to proteinaceous targets or the organization of molecular functional materials. The mindset developed in relation to the halogen bond prompted the interest in the tendency of elements of groups 13–16 of the periodic table to form analogous attractive interactions with nucleophiles. This Account addresses the chalcogen bond (ChB), the attractive interaction formed by group 16 elements with nucleophiles, by adopting a crystallographic point of view. Structures of organic derivatives are considered where chalcogen atoms form close contacts with nucleophiles in the geometry typical for chalcogen bonds. It is shown how sulfur, selenium, and tellurium can all form chalcogen bonds, the tendency to give rise to close contacts with nucleophiles increasing with the polarizability of the element. Also oxygen, when conveniently substituted, can form ChBs in crystalline solids. Chalcogen bonds can be strong enough to allow for the interaction to function as an effective and robust tool in crystal engineering. It is presented how chalcogen containing heteroaromatics, sulfides, disulfides, and selenium and tellurium analogues as well as some other molecular moieties can afford dependable chalcogen bond based supramolecular synthons. Particular attention is given to chalcogen containing azoles and their derivatives due to the relevance of these moieties in biosystems and molecular materials. It is shown how the interaction pattern around electrophilic chalcogen atoms frequently recalls the pattern around analogous halogen, pnictogen, and tetrel derivatives. For instance, directionalities of chalcogen bonds around sulfur and selenium in some thiazolium and selenazolium derivatives are similar to directionalities of halogen bonds around bromine and iodine in bromonium and iodonium compounds. This gives experimental evidence that similarities in the anisotropic distribution of the electron density in covalently bonded atoms translates in similarities in their recognition and self-assembly behavior. For instance, the analogies in interaction patterns of carbonitrile substituted elements of groups 17, 16, 15, and 14 will be presented. While the extensive experimental and theoretical data available in the literature prove that HaB and ChB form twin supramolecular synthons in the solid, more experimental information has to become available before such a statement can be safely extended to interactions wherein ele...

An Overview of Strengths and Directionalities of Noncovalent Interactions: σ-Holes and π-Holes

“…Through these positive potentials, the molecule can interact attractively with negative sites, such as lone pairs, π-electrons, and anions [2][3][4][5]. This accounts for numerous noncovalent interactions that have been known for many years [3,4,[11][12][13][14][15][16][17][18], and provides important routes to self-assembly in crystal engineering [19,20].…”

Anion Recognition by Neutral Chalcogen Bonding Receptors: Experimental and Theoretical Investigations

“…The hydrogen bond is undoubtedly the most important and prevalent noncovalent interaction . However, other elements belonging to groups 14 to 17 of the periodic table have a similar function . The electron density distribution in covalently bonded heavy atoms of groups 15 to 17 is anisotropic and frequently presents regions of positive (σ‐holes) and negative (σ‐lumps) electron density .…”

Charge‐Assisted Chalcogen Bonds: CSD and DFT Analyses and Biological Implication in Glucosidase Inhibitors

“…Among the comprehensive topic of noncovalent interactions, the hydrogen bond (HB) is undoubtedly the most important and prevalent bonding . In HB the hydrogen atom is the electrophilic site, but other elements of the p‐block of the periodic table can behave as electrophile and give rise to attractive interactions with electron rich sites . The electron density distribution in covalently bonded atoms of p‐block is frequently anisotropic and presents regions of lower or higher electron density where the electrostatic potential is typically positive or negative, respectively .…”

“…The interest in ChB has increased exponentially in the last ten years . It has been recently used in catalysis, molecular recognition, and crystal engineering .…”