The catalytic performance of novel (Co, Ni, Cu, Zn) phthalocyanines containing 2-methylresorcinol azo dyes in transfer hydrogenation reactions of aldehydes and ketones

Hydrogen transfer reduction systems have attracted increasing attention from synthetic chemists due to their operational simplicity. Herein, we report the synthesis, characterization and catalytic activity of four newly designed metallophthalocyanines containing Co ( 2a ), Ni ( 2b ), Cu ( 2c ), and Zn ( 2d ) prepared from an azo-phthalonitrile derivative incorporating 2-methylresorcinol into the ligand framework. All synthesized compounds were characterized by FT-IR and UV–Vis spectroscopy, as well as elemental analysis. The catalytic activities of the metallophthalocyanines were evaluated in the transfer hydrogenation (TH) reactions of various aldehydes, ketones, and their derivatives under an inert atmosphere using 2-propanol as the hydrogen source. Nickel phthalocyanine ( 2b ) exhibited the highest catalytic performance, affording 99% conversion of acetophenone within 5 h and benzaldehyde within 1 h. The catalytic results revealed that the transfer hydrogenation activity depends not only on the metal center but also on the structural properties of the ligand environment surrounding the complex. Therefore, the catalytic efficiency of these systems is strongly governed by both the electronic nature of the central metal ion, and the substituent groups present in the ligand framework.