Synthesis, x-ray structure and reactivity of a sterically protected azobisphenol ligand: on the quest for new multifunctional active ligands

Abstract

Different synthetic routes have been explored for the synthesis of the sterically protected 2,2'-dihydroxy-4,3,4,3'-tetratert-butylazobenzene ligand (2), which is an excellent candidate for the development of valence tautomeric complexes. As expected, such a ligand exhibits good reactivity with transition-metal ions, as shown by the synthesis and characterization of the new cobalt complex [Co(22–)(H2O)3]Cl·2.5EtOH·H2O (8). This fact together with the reversible deprotonation/protonation of the phenol groups has been used to create a chromophoric array of three states with significantly different colours, which can interconvert reversibly between them.