Aromatic triazole foldamers induced by C-H···X (X = F, Cl) intramolecular hydrogen bonding.
Aryl-triazole oligomers based on isobutyl 4-fluorobenzoate and isobutyl 4-chlorobenzoate were designed and synthesized. Crystal structure and (1)H-(1)H NOESY experiments demonstrate that the oligomers adopt stable helical conformation, which are induced by C(5)-H···X-C (X = F, Cl) intramolecular hydrogen bonding between triazole protons and halogen atoms. The stabilities of the folded conformations are confirmed by DFT calculations, which show that each C(5)-H···F-C planar interaction lowers the energy by ~3 kcal mol(-1) on average, and by ~1 kcal mol(-1) when C(5)-H···Cl-C bridges are formed. The hydrogen-bonding networks are disrupted in competitive hydrogen-bonding media such as DMSO, generating the unfolded oligomers.
Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China.
Jie
J
Shang
Nolan M
NM
Gallagher
Fusheng
F
Bie
Qiaolian
Q
Li
Yanke
Y
Che
Ying
Y
Wang
Hua
H
Jiang
D006846:Hydrocarbons, Halogenated / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D014230:Triazoles / Q000737:chemistry*
D006846:Hydrocarbons, Halogenated; D014230:Triazoles