Secondary Building Unit (SBU) Controlled Formation of a Catalytically Active Metal-Organic Polyhedron (MOP) Derived from a Flexible Tripodal Ligand

A nanosized truncated octahedron-shaped metal-organic-polyhedron (MOP) namely [{Cu-12(TMBTA)(8)(DMA)(4)(H2O)(8)}center dot 8H(2)O center dot X] MOP-TO (X = 48 H2O molecules as per SQUEEZE calculation and TGA data) was successfully derived from a flexible C-3-symmetric ligand (2,4,6-trimethylbenzene)-1,3,5-triacetic acid (TMBTA) and Cu(NO3)(2) in dimethyl acetamide (DMA) and EtOH under solvothermal conditions. The nanocage was well-characterized by single crystal X-ray diffraction (SXRD) and electron spray ionization mass spectrometry (ESI-MS). Remarkably, the nanocage molecules could be seen under high-resolution transmission electron microscope (HR-TEM). It was evident that the Cu(II) paddle wheel secondary building unit (CPWSBU) was responsible for the formation of the nanocage, as the corresponding reactions of TMBTA with other metal ions (e.g., Co(II) and Zn(II) resulted in the formation of two coordination polymers, namely [{Co(mu-TMBTA)-(H2O)(4)}](alpha) TMBTA-Co(II) and [{(H2O)(2)Zn(mu-TMBTA)Zn center dot K}center dot 2H(2)O](alpha) TMBTA-Zn(II). Interestingly, the nanocage MOP-TO was exploited in catalyzing (2,2,6,6-tetramethylpiperidin-1-yl)oxy (TEMPO)-assisted aerobic oxidation of benzyl alcohol to benzaldehyde.