Electrochemically addressable trisradical rotaxanes organized within a metal-organic framework.
The organization of trisradical rotaxanes within the channels of a Zr6-based metal-organic framework (NU-1000) has been achieved postsynthetically by solvent-assisted ligand incorporation. Robust Zr(IV)-carboxylate bonds are forged between the Zr clusters of NU-1000 and carboxylic acid groups of rotaxane precursors (semirotaxanes) as part of this building block replacement strategy. Ultraviolet-visible-near-infrared (UV-Vis-NIR), electron paramagnetic resonance (EPR), and 1H nuclear magnetic resonance (NMR) spectroscopies all confirm the capture of redox-active rotaxanes within the mesoscale hexagonal channels of NU-1000. Cyclic voltammetry measurements performed on electroactive thin films of the resulting material indicate that redox-active viologen subunits located on the rotaxane components can be accessed electrochemically in the solid state. In contradistinction to previous methods, this strategy for the incorporation of mechanically interlocked molecules within porous materials circumvents the need for de novo synthesis of a metal-organic framework, making it a particularly convenient approach for the design and creation of solid-state molecular switches and machines. The results presented here provide proof-of-concept for the application of postsynthetic transformations in the integration of dynamic molecular machines with robust porous frameworks.
Department of Chemistry, Northwestern University, Evanston, IL 60208;
Paul R
PR
McGonigal
Department of Chemistry, Northwestern University, Evanston, IL 60208;
Pravas
P
Deria
Department of Chemistry, Northwestern University, Evanston, IL 60208;
Idan
I
Hod
Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208;
Peyman Z
PZ
Moghadam
Department of Chemistry, Northwestern University, Evanston, IL 60208;
Alyssa-Jennifer
AJ
Avestro
Department of Chemistry, Northwestern University, Evanston, IL 60208;
Noah E
NE
Horwitz
Department of Chemistry, Northwestern University, Evanston, IL 60208;
Ian C
IC
Gibbs-Hall
Department of Chemistry, Northwestern University, Evanston, IL 60208;
Anthea K
AK
Blackburn
Department of Chemistry, Northwestern University, Evanston, IL 60208;
Dongyang
D
Chen
National Center for Nano Technology Research, King Abdulaziz City for Science and Technology, Riyadh 11442, Kingdom of Saudi Arabia, University Research Office, Intel Labs, Santa Clara, CA 95054;
Youssry Y
YY
Botros
Department of Chemistry, Northwestern University, Evanston, IL 60208;
Michael R
MR
Wasielewski
Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208;
Randall Q
RQ
Snurr
Department of Chemistry, Northwestern University, Evanston, IL 60208;
Joseph T
JT
Hupp
Department of Chemistry, Northwestern University, Evanston, IL 60208; Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah 22254, Kingdom of Saudi Arabia.
Omar K
OK
Farha
Department of Chemistry, Northwestern University, Evanston, IL 60208; stoddart@northwestern.edu.
J Fraser
JF
Stoddart
mechanically interlocked molecules; metal–organic framework; molecular switches; radicals; rotaxanes