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 [{Cu12(TMBTA)8(DMA)4(H2O)8}·8H2O·X] MOP-TO (X = 48 H2O molecules as per SQUEEZE calculation
and TGA data) was successfully derived from a flexible C3-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(μ-TMBTA)­(H2O)4}]∝ TMBTA-Co­(II) and [{(H2O)2Zn­(μ-TMBTA)­Zn·K}·2H2O]∝ 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.