A multifunctional use of bis(methylene)bis(5-bromo-2-hydroxyl salicyloylhydrazone): from metal sensing to ambient catalysis of A3 coupling reactions.

The potential use of bis(methylene)bis(5-bromo-2-hydroxylsalicyloylhydrazone) as a multifunctional fluorescence sensor for Cu, Ni, Co and Fe ions was investigated. The optical behaviour shows an increase in an absorption band at 408 nm which can be ascribed to the d-d transition (UV-vis) of the metal ions and a concomitant decrease in fluorescence intensity at 507 nm. The crystallographic analysis shows the binding site of the sensor to two Cu ions and confirms the stoichiometry of 1 : 2 (ligand to metal) which is in good agreement with a Job plot analysis. Furthermore the Cu-complex catalyses A3 coupling reactions at 1 mol% catalytic loading; chiral propargylamine derivatives were obtained in high yield after 24 h reaction time under ambient conditions.