Dual Roles of Polyhydroxy Matrices in the Homocoupling of Arylboronic Acids Catalyzed by Gold Nanoclusters under Acidic Conditions

Polyhydroxy biopolymers play dual roles in the stabilization of gold clusters as well as the activation of arylboronic acids through reversible binding. In acidic pH (4.57), the electronic state of boron is changed into that observed at pH 9 in the vicinity of Au/chit or Au/starch, which favors the transmetalation process; this change is why homocoupling product was observed even in acidic solutions.