Isolation and Characterization of ZnII and HgII Coordination Polymers with a Designed Azo-Aromatic Ligand: Identification of Micrometer- and Nanometer-Sized Particles

✍ Scribed by Priyabrata Banerjee; Soumitra Kar; Asim Bhaumik; Gene-Hsiang Lee; Shie-Ming Peng; Sreebrata Goswami

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 433 KB
• Volume: 2007
• Category: Article
• ISSN: 1434-1948
• DOI: 10.1002/ejic.200600878

✦ Synopsis

Abstract

Controlled layering of the deprotonated methanolic solution of the azo‐aromatic ligand [L^3^]^–^ (HL^3^ = 2‐[3‐(pyridylamino)phenylazo]pyridine) over the aqueous/methanolic solutions of metal chlorides MCl~2~ (M = Zn, Hg) afforded nano‐ and micrometer‐sized particles of the metal–organic polymeric complexes of [HgCl(C~16~H~12~N~5~)]~∞~ (1) and [ZnCl(C~16~H~18~N~5~O~3~)]~∞~ (2). Time‐dependent growth of the above particles is followed by the SEM and TEM analyses of the samples at different time intervals. The X‐ray structure of the mercury polymer reveals that two infinite 1D, zigzag chains composed of [HgCl(L^3^)]~∞~ units run along the a axis antiparalelly. The polynuclear Zn compound, in contrast, agglomerates fast to form hemispherical microcrystals with a diamondoid surface morphology, and no suitable X‐ray quality crystal of this complex could be isolated. Powder XRD analyses of the samples as well as thermogravimetric analysis (TGA) are used for their characterization. Unusually, these metal–organic polymers of the reference d^10^ metal ions are green and absorb in the low‐energy region of the visible spectrum, 660–675 nm. Semiempirical calculations on a representative complex 1 suggest that the transitions in the complexes involve ligand orbitals. These also show multiple emissions in the blue‐green region. The Zn complex, which is microporous, shows reversible adsorption/desorption of N~2~ and H~2~ gasses. The mercury polymer, on the other hand, shows poor adsorption ability. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)