Construction of preorganized uracil based polytopic tectons for hydrogen-bonded supramolecular architectures

Construction of preorganized uracil based polytopic tectons for hydrogen-bonded supramolecular architectures

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Multitopic uracil linkers as building blocks for supramolecular architectures are very important due to the ability of the Uracil moiety to form Hydrogen bonds. Several polytopic ligands decorated with 1-methyluracil moieties at their ends have been synthesized in high yield. Single crystal X-ray diffraction analyses of bis-uracil conjugate (bis(1-methyluracilyl-5yl-)4-nitrobenzyl methane) and tetra-uracil conjugate (1,3-bis[di(1-methyluracilyl)methyl]benzene) indicate presence of distinctly different hydrogen bonding patterns in the supramolecular framework. While self-assembly of the bis-uracil conjugate utilizes a wobble type (mismatch) self-pairing, no base-pairing interaction of any kind is observed in the packing of tetra-uracil conjugate. In the latter case, the presence of an acyclic water trimer reinforces the supramolecular framework. However, in the presence of HClO4, molecules of the tetra conjugate are again associated via wobble (mismatched) complimentary self-base pairing. The tetra conjugate represents the first nucleobase based tetratopic ligand till date. Investigation, as to how the hydrogen bonded supramolecular framework is affected on increasing the number of hydrogen-bonding pendants, was reported in the Journal of Molecular Structure (2012, 1015, 99-105).