In Situ Coordination-Catalyzed o-Vanillin Underwent a One-Pot Tandem Reaction to Construct Complex Chiral Tetrameric Isomer-Based Hexanuclear Clusters

Abstract

In this work, Dy(NO₃)₃·6H₂O and o-vanillin reacted under “one-pot” conditions, achieving for the first time four efficient condensations of o-vanillin and obtaining a pair of chiral hexanuclear clusters R/S-Dy₆. The four Dy(III) ions in the structure of R/S-Dy₆ are arranged in a planar quadrilateral with a Dy(III) ion derived from each of the upper and lower ends, forming a shape similar to a “chair”. The complex chiral ligands H₄L_R¹ and H₄L_S¹ were obtained from simple o-vanillin through a multistep tandem reaction. Their formation process involved a series of reaction steps, including a free radical coupling reaction to form pinacol and an in situ tandem reaction of pinacol and o-vanillin. Magnetic studies show that the Dy(III) ions in R/S-Dy₆ have magnetic anisotropy and/or low excited states. In addition, R/S-Dy₆ has an outstanding ability to produce reactive oxygen species under low-power light irradiation and shows excellent photodynamic sterilization. The inhibition zones against Escherichia coli are about 2.09 and 2.99 cm, and the inhibition zones against Staphylococcus aureus are about 2.51 and 2.93 cm, respectively. This work not only provides a vivid example for the synthesis of complex chiral organic products but also promotes the progress of lanthanide clusters’ crystal engineering.