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.
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA.
Lei
L
Fang
Mohamad
M
Hmadeh
Jishan
J
Wu
Mark A
MA
Olson
Jason M
JM
Spruell
Ali
A
Trabolsi
Ying-Wei
YW
Yang
Mourad
M
Elhabiri
Anne-Marie
AM
Albrecht-Gary
J Fraser
JF
Stoddart
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