Visible-Light-Driven Self-Coupling and Oxidative Dehydrogenation of Amines to Imines via a Mn(II)-Based Coordination Polymer
Imines are versatile and valuable organic intermediates in the synthesis of fine chemicals, pharmaceuticals and agrochemicals. The direct synthesis of imines through one-pot procedure via an oxidative process to reduce energy consumption and waste emission has long been pursued. In this study, we prepared a novel visible-light-responsive coordination polymer with one-dimensional structure for the direct photocatalytic synthesis of imine in presence of green and economy oxidant of molecular oxygen. Photocatalytic experiment suggests the synthesized coordination polymer is not only efficient for self-coupling of primary amines to generate homo-coupled imines, but also capable for oxidative dehydrogenation of secondary amines in high selectivity to produce hetero-coupled imines. Mechanism studies have demonstrated that both photocatalytic reactions depend on reactive oxygen species of singlet oxygen and superoxide radical in the system, indicating effective electron and energy transfer from photoexcited coordination polymer to molecular oxygen. The study not only presents a rare example of visible-light-driven coordination polymer with low-dimensional structure capable for direct photocatalytic synthesis of imines, but also demonstrates the great potential of photoactive coordination polymers for organics transformation.