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

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, 2) and tetra-uracil conjugate (1,3-bis[di(1-methyluracilyl)methyl]benzene, 3) indicate presence of distinctly different hydrogen bonding patterns in the supramolecular framework. While self-assembly of 2 utilizes a wobble type (mismatch) self-pairing, no base-pairing interaction of any kind is observed in the packing of tetra-uracil conjugate 3. In the latter case, the presence of an acyclic water trimer reinforces the supramolecular framework. However, in the presence of HClO4, molecules of 3 are again associated via wobble (mismatched) complimentary self-base pairing. 3 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, is reported here.

► Preparation and characterization of uracil based polytopic tectons.
► First example of structurally characterized tetra-uracil conjugate.
► H-bonding network is dependent on number of uracil units or presence of a guest.