TY - JOUR
T1 - Discrete Open-Shell Tris(bipyridinium radical cationic) Inclusion Complexes in the Solid State
AU - Anamimoghadam, Ommid
AU - Jones, Leighton O.
AU - Cooper, James A.
AU - Beldjoudi, Yassine
AU - Nguyen, Minh T.
AU - Liu, Wenqi
AU - Krzyaniak, Matthew D.
AU - Pezzato, Cristian
AU - Stern, Charlotte L.
AU - Patel, Hasmukh A.
AU - Wasielewski, Michael R.
AU - Schatz, George C.
AU - Stoddart, J. Fraser
N1 - Funding Information:
The authors thank Northwestern University (NU) for their continued support of this research. We would also like to thank Tyler J. Pearson and Danna E. Freedman for their assistance with the collection of SQUID data. This work was also supported by the Department of Energy, Office of Science, Office of Basic Energy Sciences Award No. DE-SC0019356 (M.R.W.) and Award No. DE-SC0004752 (L.O.J. and G.C.S.) for theory applications. The contribution of the Integrated Molecular Structure Education and Research Center (IMSERC) at NU is also gratefully acknowledged. This research was supported in part by the computational resources and staff contributions provided for by the Quest High Performance Computing Facility at NU, which is jointly supported by the Office of the Provost, the Office for Research, and Northwestern University Information Technology.
PY - 2021/1/13
Y1 - 2021/1/13
N2 - The solid-state properties of organic radicals depend on radical-radical interactions that are influenced by the superstructure of the crystalline phase. Here, we report the synthesis and characterization of a substituted tetracationic cyclophane, cyclobis(paraquat-p-1,4-dimethoxyphenylene), which associates in its bisradical dicationic redox state with the methyl viologen radical cation (MV•+) to give a 1:1 inclusion complex. The (super)structures of the reduced cyclophane and this 1:1 complex in the solid state deviate from the analogous (super)structures observed for the reduced state of cyclobis(paraquat-p-phenylene) and that of its trisradical tricationic complex. Titration experiments reveal that the methoxy substituents on the p-phenylene linkers do not influence binding of the cyclophane toward small neutral guests - such as dimethoxybenzene and tetrathiafulvalene - whereas binding of larger radical cationic guests such as MV•+ by the reduced cyclophane decreases 10-fold. X-ray diffraction analysis reveals that the solid-state superstructure of the 1:1 complex constitutes a discrete entity with weak intermolecular orbital overlap between neighboring complexes. Transient nutation EPR experiments and DFT calculations confirm that the complex has a doublet spin configuration in the ground state as a result of the strong orbital overlap, while the quartet-state spin configuration is higher in energy and inaccessible at ambient temperature. Superconducting quantum interference device (SQUID) measurements reveal that the trisradical tricationic complexes interact antiferromagnetically and form a one-dimensional Heisenberg antiferromagnetic chain along the a-axis of the crystal. These results offer insights into the design and synthesis of organic magnetic materials based on host-guest complexes.
AB - The solid-state properties of organic radicals depend on radical-radical interactions that are influenced by the superstructure of the crystalline phase. Here, we report the synthesis and characterization of a substituted tetracationic cyclophane, cyclobis(paraquat-p-1,4-dimethoxyphenylene), which associates in its bisradical dicationic redox state with the methyl viologen radical cation (MV•+) to give a 1:1 inclusion complex. The (super)structures of the reduced cyclophane and this 1:1 complex in the solid state deviate from the analogous (super)structures observed for the reduced state of cyclobis(paraquat-p-phenylene) and that of its trisradical tricationic complex. Titration experiments reveal that the methoxy substituents on the p-phenylene linkers do not influence binding of the cyclophane toward small neutral guests - such as dimethoxybenzene and tetrathiafulvalene - whereas binding of larger radical cationic guests such as MV•+ by the reduced cyclophane decreases 10-fold. X-ray diffraction analysis reveals that the solid-state superstructure of the 1:1 complex constitutes a discrete entity with weak intermolecular orbital overlap between neighboring complexes. Transient nutation EPR experiments and DFT calculations confirm that the complex has a doublet spin configuration in the ground state as a result of the strong orbital overlap, while the quartet-state spin configuration is higher in energy and inaccessible at ambient temperature. Superconducting quantum interference device (SQUID) measurements reveal that the trisradical tricationic complexes interact antiferromagnetically and form a one-dimensional Heisenberg antiferromagnetic chain along the a-axis of the crystal. These results offer insights into the design and synthesis of organic magnetic materials based on host-guest complexes.
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U2 - 10.1021/jacs.0c07148
DO - 10.1021/jacs.0c07148
M3 - Article
C2 - 33347315
AN - SCOPUS:85099090623
VL - 143
SP - 163
EP - 175
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 1
ER -