Supramolecular substitution reactions between hydrazide-based molecular duplex strands: complexation induced nonsymmetry and dynamic behavior.
Supramolecular substitution reactions between hydrazide-based oligomers 1a- c and 2a- c were systematically investigated. Each oligomer existed as hydrogen-bonding mediated molecular duplex strands or a polymeric zipper structure in apolar solvents. But when another oligomer with complementary hydrogen bonding sites was added, a heterodimer structure formed due to supramolecular substitution reaction driven by the formation of more hydrogen bonds, which was evidenced by NMR experiments, sometimes gel-sol transition. When a nonsymmetric oligomer and a symmetric oligomer were involved, complexation-induced nonsymmetry was observed. When two nonsymmetric oligomers were involved, two hydrogen-bonded isomers were observed in solution. Variable-temperature (1)H NMR experiments further revealed unique dynamic behavior for the individual oligomer and the complexes. When diacetyl-terminated oligomer 1c was involved, slides perpendicular to hydrogen bonds between two constituent molecules were observed, which led to complicated (1)H NMR spectra at lower temperature; otherwise, high selectivity was obtained. Combined with the results we reported previously, a detailed picture of the structure-property relationship for our hydrazide-based oligomers was depicted, which would provide guidelines for the design of hydrazide-based fine-tuning functional materials.
Yang
Yong
Y
Beijing National Laboratory for Molecular Sciences, Center for Chemical Biology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Xiang
Jun-Feng
JF
Xue
Min
M
Hu
Hai-Yu
HY
Chen
Chuan-Feng
CF
D005563:Formic Acid Esters / Q000737:chemistry; D006834:Hydrazines / Q000737:chemistry*; D006860:Hydrogen Bonding; D046911:Macromolecular Substances / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods
D005563:Formic Acid Esters; D006834:Hydrazines; D046911:Macromolecular Substances; C000345:t-butyloxycarbonyl group