Halogen Bonding: From Fundamentals to Applications

Guest Editors Maté Erdélyi, Catharine Esterhuysen, and Weilang Zhu introduce the joint Special Collection on Halogen Bonding published by ChemPlusChem The Chemical Record. This collection is organized in association with 4th International Symposium (ISXB4) features top multidisciplinary contributions where halogen bonding plays a pivotal role, including computational, synthetic catalytic, supramolecular crystal engineering, biological investigations applications. Despite first observations of dating back as far to early 19th century,1 it received marked interest earliest 1950s when Odd Hassel2 reported X-ray crystallographic structure halogen-bonded complex.3 Following impactful yet sporadic discoveries late 20th century that laid groundwork for our current understanding, has developed into distinct quickly growing research field over past two decades. biennial conference series “International (ISXB)” become prime forum discussions around developments field. took off 2014 Porto Cesareo (Italy),4 was continued Gothenburg (Sweden, 2016)5 Greenville (USA, 2018)6 latest edition take place Stellenbosch (South Africa) March 2020; however this became an online event November 2020 result COVID-19 pandemic. latter meeting attracted 229 participants, who presented 71 talks (in mixture live pre-recorded formats) 90 posters spanned wide range topics both fundamental applied character. covered following themes: Nature X-bonding Supramolecular chemistry engineering Solid state properties Understanding behavior Applications synthesis, catalysis industry solution biology Record presents selection were discussed at symposium, giving flavor successful reflecting width discussed, synthetic, supramolecular, role. broad, nature reflected Collection, which also follow themes ISXB-4 conference. They highlight advantage holding such meeting, many cut across themes, combining theoretical calculations, experimental studies, and/or applications fields. diversity highlights how progressed since ISXB 2014. For instance, presentations then focused initial electrostatic model based σ-hole concept,4 subsequent meetings showing concept been challenged gradually refined7 increasing awareness importance polarisation charge transfer. In further probed through investigating effects electronegativity electrophilicity halogen, hydrogen (Legon), tetrel (Saha co-workers). study, even more subtle effect hybridisation C centre X−C⋅⋅⋅O bonds demonstrated. These studies have deepened understanding behavior, particularly respect can be modelled (one major concerns expressed ISXB4), assessment radial potential functions describing (Alkorta Legon) extension cooperativity (Paragi, Fonseca Guerra, As result, matured extent consistently produce assemblies those resorcin[4]arenes (Twum, Rissanen, Beyeh), arylethenynyl helices (Bowling, Speetzen, Bosch) fluorous ionic liquids (Cavallo et al.). Such taken study solid properties, co-crystals 1,4-diiodotetrafluorobenzene 4-biphenylpyridine N-oxide (Wang, Feng, Jin co-workers), adaptively capture aromatic guest molecules hence change their luminescent behavior. Co-crystals bond donors multiple acceptor sites (Aakeröy co-workers) salts organoiodines triiodide anions (McMillen, Pennington, are evidence here stay. bonding‘s broad industry, being shown drive anion-binding (Momiyama al.) [4+2] cycloaddition (Arai catalysis. Similarly, revealed crucial selenol thiol oxidation proteins (Orian found biology, seen from Review role (and other weak interactions) Shing Ho al. its scope limitations, varies within different solvents (Zeng continuously growing. Research led insight electron density distribution covalently bonded atoms anisotropic general, enabling additional elements participate interactions electrophilic sites. Some special reflect kinship bonding, instance. truly interdisciplinary endeavor contributes development number youthful age, not difficult predict rational application will soon contribute new better drugs improved procedures, establishment advanced materials, organic frameworks, employed numerous, so-far unexplored friendly openness community approaches fields important facilitator process, events conferences, provided basis rapid growth we wish express gratitude all colleagues contributed participating contributing discussion ISXB-4, submitting refereeing manuscripts Collection. We thank Jonathan Faiz Dinesh Talwar, Record, efforts carry forward. Esterhuysen: After completing PhD Rand Afrikaans University 2000, Esterhuysen joined University, she promoted professor 2018. An Alexander von Humboldt fellowship allowed her join groups Gernot Frenking Philipps-Universität Marburg Germany 2002 2010, Tim Clark Friedrich-Alexander-Universität Erlangen-Nürnberg 2016. She combines knowledge computational crystallography explain unusual materials. Weiliang obtained his (1998) Shanghai Institute Materia Medica, Chinese Academy Sciences. working visiting lecturer Singapore Polytechnic (1998–2004), he moved Medica (2004) principal investigator, Director Drug Discovery Design Center 2009. His interests molecular modeling, drug design, medicinal natural product. Máté Erdélyi graduated Semmelweis Uppsala University. postdoctoral physical California, San Diego, NMR spectroscopy structural Max Planck Biophysical Chemistry, initiated independent Gothenburg. 2017, currently Chair Organic Chemistry. encompass method development, product, chemistry.