A Series of Trifacial Pd sub(6) Molecular Barrels with Porphyrin Walls

• Published in: Chemistry : a European journal 2012-07, Vol.18 (31), p.9571-9579
• Main Authors: Bar, Arun Kumar, Mohapatra, Sudip, Zangrando, Ennio, Mukherjee, Partha Sarathi
• Format: Article
• Language: English
• Subjects: Barrels; Diffraction; Nanostructure; Pocket; Porphyrins; Self assembly; Spectroscopy; Walls
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201201077

Three new nanoscopic trigonal prisms, [(tmen) sub(6)Pd sub(6)(H sub(2)L) sub(3)](NO sub(3)) sub(12) (1), [(Meen) sub(6)Pd sub(6)(H sub(2)L) sub(3)](NO sub(3)) sub(12) (2), and [(2,2'-bipy) sub(6)Pd sub(6)(H sub(2)L) sub(3)](NO sub(3)) sub(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 (H sub(2)L) as a donor and cis-blocked Pd super(II) 90 degree acceptors. These complexes were fully characterized by spectroscopic studies and single-crystal X-ray diffraction. All of these barrels quantitatively bind Zn super(II) ions in the N sub(4) pockets of the porphyrin walls at room temperature. Their corresponding zinc-embedded complexes, [(tmen) sub(6)Pd sub(6)(ZnL) sub(3)](NO sub(3)) sub(12) (1a), [(Meen) sub(6)Pd sub(6)(ZnL) sub(3)](NO sub(3)) sub(12) (2a), and [(2,2'-bipy) sub(6)Pd sub(6)(ZnL) sub(3)](NO sub(3)) sub(12) (3a), were synthesized under ambient conditions by the post-synthetic binding of Zn super(II) ions into the H sub(2)N sub(4) pockets of the porphyrin walls of these complexes. These zinc-embedded complexes were characterized by electronic absorption, fluorescence emission, super(1)HNMR 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. Like shooting fish in a barrel: Three nanoscopic trifacial Pd sub(6) molecular barrels with porphyrin walls were characterized by spectroscopy and X-ray diffraction. These water-soluble barrels bound Zn super(II) ions in the N sub(4) pockets of the porphyrin walls.