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Metalloporphyrin-Based Inclusion Materials:  Exploiting Ligating Topologies and Hydrogen-Bonding Backbones in Generating New Supramolecular Architectures

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posted on 03.09.2007, 00:00 by D. Krishna Kumar, Amitava Das, Parthasarathi Dastidar
By coordination of the metal center of tetraphenylmetalloporphyrins (TPMP) [metal center = Zn(II) or Mn(II)] with pyridyl-based bidentate ligands, namely, N,N‘-bis(4-pyridyl)urea (4BPU), N,N‘-bis(3-pyridyl)urea (3BPU), and N-(4-pyridyl)isonicotinamide (4PIN), various axially modified tetraarylmetalloporphyrins (AMTAMPs) have been crystallographically characterized in their corresponding lattice inclusion complexes. Nine such inclusion crystals are prepared by crystallizing TPMP and the corresponding bidentate ligands in 1:2 molar ratio from suitable solvent systems. While the metal center Zn(II) of TPMP leads to the formation of both dimeric and monomeric AMTAMPs due to its preference for pentacoordinated geometry, the Mn(II) metal center of TPMP forms both polymeric and discrete hexacoordinated AMTAMPs due to its preference for hexacoordinated geometry. However, there seem to be no control on the formation of a particular AMTAMP. Structural analyses suggest that most of the AMTAMPs display new types of packing in the corresponding inclusion crystals.