Liquid crystalline derivatives of heterocyclic radicals

Spin Symmetry Breaking: Superparamagnetic and Spin Glass-Like Behavior Observed in Rod-Like Liquid Crystalline Organic Compounds Contacting Nitroxide Radical Spins

“…In fact, the highly enantiomerically-enriched compounds (S,S)-1 always exhibited a larger positive magneto-LC effect than the corresponding racemic ones trans-1 [35,36]. Due to the latest comprehensive review as well as database-like article regarding the preparation, characterization, and magnetic properties of a wide array of all-organic LC radicals synthesized, thus, far, an excellent one entitled "Liquid crystalline derivatives of heterocyclic radicals" by Kaszyński is strongly recommended to refer to Reference [27].…”

“…Only a few all-organic LC radical compounds were prepared until 2003 because it was believed that the geometry and bulkiness of the radical-stabilizing substituents were detrimental to the stability of liquid crystals, which requires molecular linearity or planarity [25][26][27]. Although several rod-like organic LC compounds with a stable cyclic nitroxide unit as the spin source were prepared ( Figure 2), their molecular structures were limited to those containing a nitroxyl group in the terminal alkyl chain, away from the rigid core, and, thereby, allowed the free rotation of the nitroxyl moiety inside the molecule, resulting in a very small dielectric anisotropy (∆ε) of the whole molecule [25][26][27]. Only a few all-organic LC radical compounds were prepared until 2003 because it was believed that the geometry and bulkiness of the radical-stabilizing substituents were detrimental to the stability of liquid crystals, which requires molecular linearity or planarity [25][26][27].…”

“…Although several rod-like organic LC compounds with a stable cyclic nitroxide unit as the spin source were prepared ( Figure 2), their molecular structures were limited to those containing a nitroxyl group in the terminal alkyl chain, away from the rigid core, and, thereby, allowed the free rotation of the nitroxyl moiety inside the molecule, resulting in a very small dielectric anisotropy (∆ε) of the whole molecule [25][26][27]. Only a few all-organic LC radical compounds were prepared until 2003 because it was believed that the geometry and bulkiness of the radical-stabilizing substituents were detrimental to the stability of liquid crystals, which requires molecular linearity or planarity [25][26][27]. Although several rod-like organic LC compounds with a stable cyclic nitroxide unit as the spin source were prepared ( Figure 2), their molecular structures were limited to those containing a nitroxyl group in the terminal alkyl chain, away from the rigid core, and, thereby, allowed the free rotation of the nitroxyl moiety inside the molecule, resulting in a very small dielectric anisotropy (∆ε) of the whole molecule [25][26][27].…”

“…Although several rod-like organic LC compounds with a stable cyclic nitroxide unit as the spin source were prepared ( Figure 2), their molecular structures were limited to those containing a nitroxyl group in the terminal alkyl chain, away from the rigid core, and, thereby, allowed the free rotation of the nitroxyl moiety inside the molecule, resulting in a very small dielectric anisotropy (∆ε) of the whole molecule [25][26][27]. Rod-like LC organic mono-radicals synthesized before 2004 and their LC transition temperatures [25][26][27].…”

“…Such thermal and impurity effects are known to be commonly observed for metallic spin glass materials. Rod-like LC organic mono-radicals synthesized before 2004 and their LC transition temperatures [25][26][27].…”