Tuning receptors for the encapsulation of beryllium²

Two series of tetradentate tripodal di-pyridine-based receptors designed to bind Be²⁺ cations have been studied in the aqueous phase at the B3LYP/6-311++G(d,p) computational level. The first series comprise simple tetrahedral receptors; the second series incorporates additional scaffolding groups capable of second sphere hydrogen-bonding in order to more finely tune the binding strength towards the Be²⁺ cation. Out of the five ligand candidates, one containing a tri-pyridyl N-donor along with a phenolato O-donor (L1) exhibited a significant improvement in binding energy stabilisation (47.8 kJ mol^-1) towards the Be²⁺ cation in the presence of second-sphere H-bonding interactions.