A Series of Trifacial Pd6 Molecular Barrels with Porphyrin Walls

Abstract

Three new nanoscopic trigonal prisms, [(tmen)6Pd6(H2L)3](NO3)12 (1), [(Meen)6Pd6(H2L)3](NO3)12 (2), and [(2,2′-bipy)6Pd6(H2L)3](NO3)12 (3), have been synthesized in excellent yields through single-step metal–ligand-coordination-driven self-assembly using 5,10,15,20-tetrakis(3-pyridyl)porphyrin (H2L) as a donor and cis-blocked PdII 90° acceptors. These complexes were fully characterized by spectroscopic studies and single-crystal X-ray diffraction. All of these barrels quantitatively bind ZnII ions in the N4 pockets of the porphyrin walls at room temperature. Their corresponding zinc-embedded complexes, [(tmen)6Pd6(ZnL)3](NO3)12 (1 a), [(Meen)6Pd6(ZnL)3](NO3)12 (2 a), and [(2,2′-bipy)6Pd6(ZnL)3](NO3)12 (3 a), were synthesized under ambient conditions by the post-synthetic binding of ZnII ions into the H2N4 pockets of the porphyrin walls of these complexes. These zinc-embedded complexes were characterized by electronic absorption, fluorescence emission, 1H NMR spectroscopy, as well as elemental analysis. Complexes 1–3 exhibited considerable microporosity in their solid state. Complex 1 was an efficient adsorbent for nitrogen gas and EtOH, MeOH, and water vapors.