Aluminium(iii) and zinc(ii) complexes of azobenzene-containing ligands for ring-opening polymerisation of ε-caprolactone and rac-lactide

Abstract

The ability to control the outcome of polymerisations using an external stimulus remains a formidable challenge. Herein, we report a series of photoactive Schiff base ligands bearing azobenzene moieties, as well as seven Al(III) and Zn(II) complexes. Trans–cis isomerisation of the ligands and complexes occurred by exposure to UV light. Photoisomerisation was investigated using spectroscopic techniques and real-time reaction monitoring was conducted using FlowNMR. The activity of the complexes was tested in ring-opening polymerisation (ROP) of ε-caprolactone and rac-lactide under ambient and UV light conditions, with the isomers of the Al(III) complexes displaying marked differences in activity in the ROP of ε-caprolactone.