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Probing the Dynamic Environment-Associated Conformational Conversion from Secondary to Supersecondary Structures in Oligo(phenanthroline dicarboxamide)s

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journal contribution
posted on 2009-07-17, 00:00 authored by Hai-Yu Hu, Wei Xue, Zhi-Qiang Hu, Jun-Feng Xiang, Chuan-Feng Chen, Sheng-Gui He
The special structural features of the oligo(phenanthroline dicarboxamide)s and their dynamic environment-associated conformational conversion from secondary helical structure to supersecondary helix-turn structure, owing to the conversion of the CONH bond from s-cis form to s-trans form, have been experimentally and theoretically characterized by X-ray crystallographic, variable-temperature 1H NMR, variable-temperature circular dichroism techniques, and computational studies. It has been demonstrated that the solvent effects together with intramolecular hydrogen bonds and π−π stacking play a key role in stabilizing both the secondary and supersecondary structures. Furthermore, by introducing the intramolecular F···H−N hydrogen bond to restrict the rotation about the CONH−aryl bonds, the oligomers 6 and 7 have been synthesized, which showed well-defined and predictable secondary helical conformations in solution and in the solid state.