|M.Sc Student||Solel Moroshko Ephrath|
|Department||Department of Chemistry||Supervisor||PROFESSOR EMERITUS Ehud Keinan|
The notion that molecular containers can be obtained by total synthesis and assembly of small molecules is largely inspired by the fascinating architecture of the virus particles, particularly the spherical viral capsids. Our proposed general strategy to meet this challenge is based on the construction of non-protein molecular capsids having the icosahedral geometry by synthesis and self-assembly of 12 pentagonal tiles that bear appropriate “sticky” edges.
For the synthesis of the desired tiles we have chosen the corannulene molecule as the core skeleton due to its bowl shape, rigid polyaromatic nature and 5-fold symmetry. The choice of functional groups on the corannulene core was guided by the need to form strong, thermodynamically stable bonds between the tiles. Yet, these bonds had to be kinetically dynamic in order to enable fast equilibration and movement from the local minima of various aggregates to the global energy minimum of the spherical capsid. We have chosen the thiol functionality because it can form strong, but kinetically labile disulfide bonds and coordination bonds to most of the transition metals.
We performed the multistep synthesis of corannulene, followed by symmetric chlorination on five or ten positions on corannulene. 1,3,5,7,9-pentachlorocorannulene and decachlorocorannulene were further converted to a variety of building blocks bearing 5 or 10 sulfur derivatives, including 1,3,5,7,9-penta(tert-butylthio)corannulene, pentathiolcorannulene, and deca(tert-butylthio)corannulene. With these molecules in hand we have investigated various conditions for either oxidative self-assembly via disulfide bonds or self-assembly via metal coordination using complexes of palladium, copper and mercury. We have used various analytical and imaging techniques, including NMR, MS, X-ray crystallography, cryo-electron microscopy and high resolution TEM for analysis of the desired capsid structures. Very promising results were obtained by electron microscopy.