Dr. Bill Pennington came to UNCG from Clemson University to talk about his research in halogen bonding. He starts off by saying that halogen bonding has been around for quite a long time that even got recognized in 1863. Even in 1896 researchers didn't know what was happening and there was a lot of debate surrounding this topic, whether it was a salt, compound, etc. But it turns out it was a complex. The term halogen bonding was coined in the 1990s by Tony Legand. Halogen bonding means any non-covalent interaction involving halogens as acceptors of electron density.
Applications of Halogen Bonding
Crystal Chemistry
Dr. Pennington goes on to explain his research in crystal chemistry. Hydrogen bonding acts as an electrophilic species and is selective and strong. This makes it great for crystal chemistry. Hadi Arman came to work with Dr. Pennington and ended up making 75 halogen bond crystal structures and became an outstanding crystalographer. This mostly involves Lewis acid and Lewis base interactions and with polymorphism, any subtle change, even if it is the same compound, molecule, etc. the interactions can result in big crystal changes. The crystal form of a drug you take is going to determine its solubility, the solution rate, how quickly it gets into your system, etc and this is very important to the pharmaceutical companies.
Overall this seminar was very interesting. Dr. Bill Pennington has peaked my interest with his research. A complex that has halogen bonding that can make intricate and amazing crystal structures is beyond fascinating.
Sources:
1. http://blogs.rsc.org/ce/files/2012/09/GA11.gif
2. http://www.halogenbonding.eu/img/fig1.jpg
3. Seminar notes
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