Novel peripherally and non-peripherally hydrobenzoin substituted optically active phthalocyanines: Synthesis, characterization, aggregation, electrochemical properties and catalytic applications

Abstract

The novel optically active two zinc(II)phthalocyanines and two cobalt(II)phthalocyanines with four chiral hydrobenzoin moieties at the non-peripheral (4 and 5) and peripheral positions (6 and 7) of the phthalocyanine ring have been synthesized. The structures of the synthesized compounds are characterized by H-1 NMR, IR, UV-Vis, circular dichroism (CD) and MALDI-TOF MS spectral data. The comparative studies of the spectral, aggregation properties, voltammetry and catalytic applications of novel zinc(II) and cobalt (II)phthalocyanines, tetra-substituted with hydrobenzoin at peripheral and non-peripheral positions, were investigated. All synthesized phthalocyanines are highly soluble in most common organic solvents. In the enantioselective addition of diethylzinc to aldehydes, the best catalytic activity was obtained with 3-methoxybenzaldehyde in the presence of non-peripherally hydrobenzoin substituted zinc(II)phthalocyanine 4 and afforded the corresponding chiral secondary alcohol with the yield of 38% and the enantiomeric excess of 33%. In the oxidation of benzyl alcohol, the highest conversion of benzyl alcohol to benzaldehyde was obtained with non-peripherally substituted cobalt(II)phthalocyanine 5 as 91% with the highest selectivity of 83%. (C) 2018 Elsevier Ltd. All rights reserved.