Copper-amidocarboxylate Based Metal Organic Macrocycle and Framework: Synthesis, Structure and Catalytic Activities towards Microwave assisted Alcohol Oxidation and Knoevenagel reaction

Reactions of 3,3′-{(pyridine-2,6-dicarbonyl)bis(azanediyl)}dibenzoic acid (H2L) with copper(II) nitrate were studied and the obtained compounds [Cu2(1:2κO1O2,2:3κO3O4-L)(μ-NO3)(μ3-OH)(MeOH)2]2·2MeOH·1DMF (1) and [Cu(μ-1κO1:2κO2,3κO3:4κO4-L)(DMF)]n·4n(DMF) (2) were characterized by elemental analysis, FT-IR spectroscopy, and single-crystal and powder X-ray diffraction. Compound 1 is a macrocyclic tetranuclear Cu(II) complex possessing a central, quasi-planar rhomboid shaped {Cu4} cluster, which is the first example of a Cu(II) based macrocyclic tetranuclear complex using such a linker. Compound 2 is a 2D metal organic framework having dinuclear paddlewheel type Cu(II) assemblies that act as secondary building blocks. The topological analysis of framework 2 revealed that it has a 2,4-connected binodal net. Both compounds act as heterogeneous, easily recovered and reusable catalysts (the catalysts could be reused at least four times without significant loss of activity) for the microwave-assisted oxidation of several alcohols, as well as for the Knoevenagel condensation reaction of various aldehydes. The effect of reaction parameters such as temperature, time and type of oxidant was investigated. This study demonstrates that compound 1 can act as an efficient catalyst for the conversion of secondary alcohols (1-phenylethanol) to the corresponding ketones with high selectivity and yields up to 93% after 1 h of reaction at 120 °C and using t-BuOOH as an oxidant. Moreover, these compounds effectively catalyze the Knoevenagel condensation reactions of aldehydes with malononitrile and produce reaction yields between 64 and 99% within a very short period (10 min) under low power microwave irradiation. Furthermore, we have also studied the effectiveness of our catalyst 1 towards peroxidative oxidation/Knoevenagel condensation cascade reactions under microwave conditions.