Halogen bonding is an emerging noncovalent interaction for constructing supramolecular assemblies. Though similar to the more familiar hydrogen bonding, four primary differences between these two ...interactions make halogen bonding a unique tool for molecular recognition and the design of functional materials. First, halogen bonds tend to be much more directional than (single) hydrogen bonds. Second, the interaction strength scales with the polarizability of the bond-donor atom, a feature that researchers can tune through single-atom mutation. In addition, halogen bonds are hydrophobic whereas hydrogen bonds are hydrophilic. Lastly, the size of the bond-donor atom (halogen) is significantly larger than hydrogen. As a result, halogen bonding provides supramolecular chemists with design tools that cannot be easily met with other types of noncovalent interactions and opens up unprecedented possibilities in the design of smart functional materials. This Account highlights the recent advances in the design of halogen-bond-based functional materials. Each of the unique features of halogen bonding, directionality, tunable interaction strength, hydrophobicity, and large donor atom size, makes a difference. Taking advantage of the hydrophobicity, researchers have designed small-size ion transporters. The large halogen atom size provided a platform for constructing all-organic light-emitting crystals that efficiently generate triplet electrons and have a high phosphorescence quantum yield. The tunable interaction strengths provide tools for understanding light-induced macroscopic motions in photoresponsive azobenzene-containing polymers, and the directionality renders halogen bonding useful in the design on functional supramolecular liquid crystals and gel-phase materials. Although halogen bond based functional materials design is still in its infancy, we foresee a bright future for this field. We expect that materials designed based on halogen bonding could lead to applications in biomimetics, optics/photonics, functional surfaces, and photoswitchable supramolecules.
Hybrid organic–inorganic halide perovskites (HOIHPs) have recently emerged as a flourishing area of research. Their easy and low‐cost production and their unique optoelectronic properties make them ...promising materials for many applications. In particular, HOIHPs hold great potential for next‐generation solar cells. However, their practical implementation is still hindered by their poor stability in air and moisture, which is responsible for their short lifetime. Optimizing the chemical composition of materials and exploiting non‐covalent interactions for interfacial and defects engineering, as well as defect passivation, are efficient routes towards enhancing the overall efficiency and stability of perovskite solar cells (PSCs). Due to the rich halogen chemistry of HOIHPs, exploiting halogen bonding, in particular, may pave the way towards the development of highly stable PSCs. Improved crystallization and stability, reduction of the surface trap states, and the possibility of forming ordered structures have already been preliminarily demonstrated.
Hybrid organic–inorganic halide perovskites hold great potential for next‐generation solar cells. However, their poor stability in air and moisture still hinders their practical implementation. Preliminary data have shown that halogen bonding affords improved crystallization and stability, reduction of the surface trap states, and the possibility of forming ordered structures, paving the way towards the development of highly stable PSCs.
Halogen Bonding in Supramolecular Chemistry Metrangolo, Pierangelo; Meyer, Franck; Pilati, Tullio ...
Angewandte Chemie (International ed.),
August 4, 2008, Letnik:
47, Številka:
33
Journal Article
Recenzirano
Halogen bonding is the noncovalent interaction where halogen atoms function as electrophilic species. The energetic and geometrical features of the interaction are described along with the atomic ...characteristics that confer molecules with the specific ability to interact through this interaction. Halogen bonding has an impact on all research fields where the control of intermolecular recognition and self-assembly processes plays a key role. Some principles are presented for crystal engineering based on halogen-bonding interactions. The potential of the interaction is also shown by applications in liquid crystals, magnetic and conducting materials, and biological systems.
Halogen bonding has been extensively described in the context of a variety of self-assembled supramolecular systems and efficiently utilized in the rational design of materials with specific ...structural properties. However, it has so far received only little recognition for its possible role in the stabilization of small molecule-protein complexes. In this tutorial review, we provide a few examples of halogen bonds occurring between small halogen-substituted ligands and their biological substrates. Examples were drawn from a diverse set of compounds, ranging from chemical additives and possible environmental agents such as triclosan to pharmacologically active principles such as the volatile anesthetic halothane or HIV-1 reverse transcriptase inhibitors or a subset of non-steroidal anti-inflammatory drugs (NSAIDs) that are halogen-substituted. The crystal structures presented here, where iodine, bromine, or chlorine atoms function as halogen bonding donors and a variety of electron rich sites, such as oxygen, nitrogen and sulfur atoms, as well as aromatic π-electron systems, function as halogen bonding acceptors, prove how halogen bonds can occur in biological systems and provide a class of highly directional stabilizing contacts that can be exploited in the process of rational drug design.
It is proposed that noncovalent interactions, wherein it is possible to identify an element or moiety working as the electrophile, are named by referring to the Group of the Periodic Table the ...electrophilic atom belongs to. The resulting terminology generalizes a criterion which was used in the recent IUPAC definition of halogen bond and inspired the definition of hydrogen bond. A systematic, unambiguous, and periodic naming is obtained and applies to the majority of the attractive interactions formed by the elements of Groups 1, 2, 13–17 and, possibly, to some interactions formed by the elements of other Groups.
Cl/Br/I alternative substitutions in a series of dihalophenols indicate that type I and type II halogen···halogen contacts have different chemical nature. Only the latter ones qualify as true halogen ...bonds, according to the recent IUPAC definition.
Supramolecular Hierarchy among Halogen-Bond Donors Aakeröy, Christer B.; Baldrighi, Michele; Desper, John ...
Chemistry : a European journal,
November 25, 2013, Letnik:
19, Številka:
48
Journal Article
Recenzirano
Through a combination of structural chemistry, vibrational spectroscopy, and theory, we have systematically examined the relative structure‐directing importance of a series of ditopic halogen‐bond ...(XB) donors. The molecular electrostatic potential surfaces of six XB donors were evaluated, which allowed for a charge‐based ranking. Each molecule was then co‐crystallized with 21 XB acceptors and the results have made it possible to map out the supramolecular landscape describing the competition between I/Br–ethynyl donors, perfluorinated I/Br donors, and I/Br–phenyl based donors. The results offer practical guidelines for synthetic crystal engineering driven by robust and directional halogen bonds.
Joining the ranks: The halogen‐bonding strength of iodo and bromo analogues of ethynyl, perfluorinated, and phenyl‐based donors are compared theoretically, through the electrostatic potential surfaces of the donors, and experimentally, through the formation of co‐crystals by co‐grinding, in order to provide a “supramolecular ranking” of these moieties for crystal engineering applications (see graphic).
Halogen bonding has increasingly facilitated the assembly of diverse host-guest solids. Here, we show that a well-known class of organic salts, bis(trimethylammonium) alkane diiodides, can reversibly ...encapsulate α,ω-diiodoperfluoroalkanes (DIPFAs) through intermolecular interactions between the host's I⁻ anions and the guest's terminal iodine substituents. The process is highly selective for the fluorocarbon that forms an I⁻···I(CF₂)mI···I⁻ superanion that is matched in length to the chosen dication. DIPFAs that are 2 to 12 carbons in length (common industrial intermediates) can thereby be isolated from mixtures by means of crystallization from solution upon addition of the dissolved size-matched ionic salt. The solid-state salts can also selectively capture the DIPFAs from the vapor phase, yielding the same product formed from solution despite a lack of porosity of the starting lattice structure. Heating liberates the DIPFAs and regenerates the original salt lattice, highlighting the practical potential for the system in separation applications.
The confined space inside a self‐assembled cage enhanced halogen bonding (XB) between iodoperfluorocarbons (XB donors) and NO3− anions or H2O molecules (XB acceptors), as confirmed by NMR ...spectroscopy in solution and by X‐ray crystallography in the solid state. The cavity also bound an XB donor–acceptor pair, C6F3I3 and C6H5NMe2, in a selective pairwise fashion.
Close but comfortable: Iodoperfluorocarbons were efficiently included in a self‐assembled cage owing to halogen bonding (XB) with NO3− anions or H2O molecules (see picture: C gray, N blue, O red, F green, I purple, Pd brown). The confined cavity of the cage enhanced XB, as confirmed by NMR spectroscopy in solution and X‐ray crystallography in the solid state. Pairwise selective XB between C6F3I3 and C6H5NMe2 within the cavity was also observed.
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