Discs, dumbbells and superdiscs: molecular and supermolecular architecture dependent magnetic behavior of mesogenic Blatter radical derivatives

A series of isomeric supermolecular bi-and tri-radicals, in which half disc mesogens are connected 1,4- and 1,3,5-through benzene, respectively, are investigated for liquid crystalline (optical, thermal and powder XRD methods) and magnetic properties (SQUID and VT-EPR methods). The results demonstrate diverse phase structures of the bi- and tri-radicals, which self-organize into Col(r), Col(h), and Col(h(3D)) phases. Magnetic data revealed intermolecular ferromagnetic interactions in the solid-state only in bi- and tri-radicals with the connection at the C(3) position, for which the Weiss constant theta (7.8 and 5.2 K, respectively; from Curie-Weiss analysis) and J/k(B) exchange interaction energy (2.74 and 3.14 K, respectively; from Baker thermal expansion analysis) were obtained. Variable temperature EPR data demonstrated an increase of signal intensity in most liquid crystalline phases and continuous increase above the mesophase-isotropic liquid transition in two biradicals. Overall results indicate that the dumbbell shape (biradicals) and connection through the C(3) position are most favorable for mesogenic and non-trivial magnetic properties in the series.

Automated summary

A series of isomeric supermolecular bi-and tri-radicals with half disc mesogens connected at different positions show diverse phase structures and magnetic properties. The connection through the C(3) position is found to be most favorable for mesogenic and non-trivial magnetic properties in the series.