Acid-base actuation of [c2]daisy chains.
A versatile synthetic strategy, which was conceived and employed to prepare doubly threaded, bistable [c2]daisy chain compounds, is described. Propargyl and 1-pentenyl groups have been grafted onto the stoppers of [c2]daisy chain molecules obtained using a template-directed synthetic protocol. Such [c2]daisy chain molecules undergo reversible extension and contraction upon treatment with acid and base, respectively. The dialkyne-functionalized [c2]daisy chain (AA) was subjected to an [AA+BB] type polymerization with an appropriate diazide (BB) to afford a linear, mechanically interlocked, main-chain polymer. The macromolecular properties of this polymer were characterized by chronocoulometry, size exclusion chromatography, and static light-scattering analysis. The acid-base switching properties of both the monomers and the polymer have been studied in solution, using (1)H NMR spectroscopy, UV/vis absorption spectroscopy, and cyclic voltammetry. The experimental results demonstrate that the functionalized [c2]daisy chains, along with their polymeric derivatives, undergo quantitative, efficient, and fully reversible switching processes in solution. Kinetics measurements demonstrate that the acid/base-promoted extension/contraction movements of the polymeric [c2]daisy chain are actually faster than those of its monomeric counterpart. These observations open the door to correlated molecular motions and to changes in material properties.
Fang
Lei
L
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA.
Hmadeh
Mohamad
M
Wu
Jishan
J
Olson
Mark A
MA
Spruell
Jason M
JM
Trabolsi
Ali
A
Yang
Ying-Wei
YW
Elhabiri
Mourad
M
Albrecht-Gary
Anne-Marie
AM
Stoddart
J Fraser
JF
D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives* / Q000737:chemistry; D001555:Benzene Derivatives / Q000737:chemistry; D047248:Crown Compounds / Q000737:chemistry*; D043844:Crown Ethers; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
D001555:Benzene Derivatives; D047248:Crown Compounds; D043844:Crown Ethers; D011108:Polymers; C071087:dibenzo-24-crown-8; D015082:2,2'-Dipyridyl