Interplay of Bridge Topology and Conformation in Phenylene‐Bridged Trityl Diradicals
- 1Clausius‐Institute for Physical and Theoretical Chemistry University of Bonn Bonn Germany
- 2Department of Industrial Chemistry “Toso Montanari” University of Bologna Bologna Italy
- 3Mulliken Center Clausius‐Institute for Physical and Theoretical Chemistry University of Bonn Bonn Germany
Abstract
Tuning the exchange coupling constant J is a valuable tool in the design of molecular systems for applications in molecular magnetism and quantum information science. The phenylene group is an archetypal bridge to influence the sign and magnitude of J via topology and substitution. Motivated by this, we synthesized an m‐phenylene‐bridged trityl diradical ( m‐ben‐(TAM)2 •• ) and explored its magnetic coupling in comparison to the p‐phenylene‐ and p‐xylene‐bridged analogues. We find a weak antiferromagnetic coupling of −4 GHz for m‐ben‐(TAM)2 •• in the powder, which increases to −169 GHz in solution. The antiferromagnetic nature of the spin‐spin coupling is rationalized by the large dihedral angle between the trityl and bridge aryl groups, which diminishes the ferromagnetic π‐contribution. The increase in the magnitude of J by going from the powder to the solution state is rationalized by a large structural change, as investigated by density functional theory (DFT) calculations and molecular dynamics (MD) simulations. We speculate that these geometric changes lead to changes in the intramolecular through‐bond and through‐space contributions to J, but can't rule out that it is also connected to intermolecular contributions in the powder. These results highlight that the design of ferromagnetic coupling cannot be based only on the topological rule.
Related
- Conformationally locked planar-chiral single- and double-bridged perylene diimides with highly twisted structures: topology-controlled synthesis and chiroptical properties
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- Bridging [8]cyclo- para -phenylene with carbonyl and dicyanovinylene functionalities to access electron-deficient nanohoops for n-type OFET applications
- Molecular Spiral Staircases: Stepwise Construction of Multilayer Phenylene Stacks.
BibTeX
@article{kopp2026interplay,
title = {{Interplay of Bridge Topology and Conformation in Phenylene‐Bridged Trityl Diradicals}},
author = {Kevin Lars Kopp and Tobias Hett and Andrea Pellegrini and Stefan Grimme and Olav Schiemann},
journal = {Chemistry (Weinheim an Der Bergstrasse, Germany)},
year = {2026},
month = jul,
doi = {10.1002/chem.71384},
url = {https://doi.org/10.1002/chem.71384},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Interplay of Bridge Topology and Conformation in Phenylene‐Bridged Trityl Diradicals
AU - Kevin Lars Kopp
AU - Tobias Hett
AU - Andrea Pellegrini
AU - Stefan Grimme
AU - Olav Schiemann
PY - 2026
DA - 2026/07/09
JO - Chemistry (Weinheim an Der Bergstrasse, Germany)
DO - 10.1002/chem.71384
UR - https://doi.org/10.1002/chem.71384
AB - Tuning the exchange coupling constant J is a valuable tool in the design of molecular systems for applications in molecular magnetism and quantum information science. The phenylene group is an archetypal bridge to influence the sign and magnitude of J via topology and substitution. Motivated by this, we synthesized an m‐phenylene‐bridged trityl diradical ( m‐ben‐(TAM)2 •• ) and explored its magnetic coupling in comparison to the p‐phenylene‐ and p‐xylene‐bridged analogues. We find a weak antiferromagnetic coupling of −4 GHz for m‐ben‐(TAM)2 •• in the powder, which increases to −169 GHz in solution. The antiferromagnetic nature of the spin‐spin coupling is rationalized by the large dihedral angle between the trityl and bridge aryl groups, which diminishes the ferromagnetic π‐contribution. The increase in the magnitude of J by going from the powder to the solution state is rationalized by a large structural change, as investigated by density functional theory (DFT) calculations and molecular dynamics (MD) simulations. We speculate that these geometric changes lead to changes in the intramolecular through‐bond and through‐space contributions to J, but can't rule out that it is also connected to intermolecular contributions in the powder. These results highlight that the design of ferromagnetic coupling cannot be based only on the topological rule.
SN - 0947-6539
SN - 1521-3765
ER -