Binding of the terephthalate dianion by di- tri- and tetrathiourea functionalised fused [3] and [5]polynorbornane based hosts

The affinity of new di-, tri- and tetrathiourea functionalised fused [3] and [5]polynorbornane based hosts 1-6 towards terephthalate2- was proportional to the size of the preorganised cleft/cavity imparted by the polynorbornane scaffold. Receptors based on the [5]polynobornane framework had greater affinities for the anion due to a higher degree of host:guest size complementarity. Hosts 1-5 formed 1:1 host:guest complexes with the rigid dianion, yet remarkably, host 6 was found to bind two terephthalate guests.