The forgotten liquid crystals of Daniel Vorländer: A new look at mesogenic 4-pyridones

Three classes of 4-pyridone (1H-pyridin-4-one) terminated liquid crystals were synthesized and their mesogenic properties examined. These liquid crystal classes differ in the composition of the aromatic core group which vary among azobenzene, stilbene or tolane groups. The synthesis of the 4-pyridones was accomplished by aromatic nucleophilic substitution reaction of the appropriate activated aryl fluoride with 4-hydroxypyridine. These pyridone liquid crystals possess broad enantiotropic nematic and smectic A phases and may possess useful properties such as high birefringence and polarity including hydrogen bonding capability. The original report of a 4-pyridone containing liquid crystal due to Vorländer has been substantiated.