###### Abstract  
The synthesis and characterization of a new class of 1,2,4-oxadiazolplypyridinium as a cationic scaffold for fluorinated ionic liquid crystals is herein described. A series of 12 fluorinated heterocyclic salts based on a 1,2,4-oxadiazol moiety, connected through its C(5) or C(3) to an \(N\)-alkylpyridinium unit and a perfluoroheptyl chain, differing in the length of the alkyl chain and counterions, has been synthesized. As counterions iodide, bromide and bis(trifluoromethane)sulfonimide have been considered. The synthesis, structure, and liquid crystalline properties of these compounds are discussed on the basis of the tuned structural variables. The thermotropic properties of this series of salts have been investigated by differential scanning calorimetry and polarized optical microscopy. The results showed the existence of an enantiotropic mesomorphic smectic liquid crystalline phase for six bis(trifluoromethane)sulfonimide salts.  
ionic liquids; liquid crystals; fluorinated salts; heterocyclic; mesogens 1]Dipartimento di Scienze e Tecnologie Biologiche, Chimiche e Farmaceutiche (STEBICEF), University of Palermo, Viale delle Scienze, Ed. 17, 90128 Palermo, Italy;  
[PERSON]SS] [On leave of the 1,2,4-oxadiazol moiety][PERSON]. [PERSON], [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON]; [PERSON], [PERSON]; [PERSON], [PERSON].  
of the counterion [4,8]. In this context, a variety of 1,2,4-oxadaazoles and 1,2,4-triazolees have been investigated with tuned structural variables [3,8,9,10,11,12,13]. The latest studies have focused on a series of 1,2,4-triazoleolium ions with chain length variation of the attached fluoroalkyl (m = 3, 7, 9) and alkyl chains (n = 10, 12, 14) as well as different counterions such as trifluoromentanesulfonate ([OTf\({}^{-}\)]), bis(trifluoromethane)sulfonimide ([TT\({}_{2}\)N\({}^{-}\)]), and tetrafluoroborate ([BF\({}_{4}\)\({}^{-}\)]). This family is proposed as thermotropic triphilic ionic liquid crystals, showing predominantly smectic A (SmA) phases, which can be dominantly attributed to the ionic nature of these materials as well as to the alkyl and perfluoroalkyl chains [10,14,15,16,17]. Compared to this family, the perfluoroheptly 1,2,4-oxadaazoles bearing a \(N\)-methylated-4-pyridyl moiety (visualized in Chart 1) with iodide [I\({}^{-}\)] or [OTf\({}^{-}\)] as counterions behave as ionic liquids, thus, being low-melting organic salts. However, the \(N\)-methylated-3-pyridyl moiety has been found to exhibit thermally induced liquid crystalline behavior [10]. In order to drive 1,2,4-oxadaazoles with the 4-substituted pyridinium to LC formation, the combination of perfluoroheptyl chains and the introduction of long alkyl chains into the system are a promising way to obtain micro-segregation resulting in ionic liquid crystalline behavior. Thus, we focused on the synthesis and characterization of a new class of 1,2,4-oxadaizoylpyridinium salts as cationic scaffold for fluorinated ionic liquid crystals. The 12 salts of this work are summarized in Chart 1 and differ in the reciprocal position of the perfluoroheptyl chain and the pyridinium moieties on the interspacing oxadaizole ring, resulting in **1a-f** and **2a-f** being reigoisomers. Furthermore, alkyl chains of different length (C\({}_{10}\)H\({}_{21}\) for **1a,d** and **2a,d**; C\({}_{12}\)H\({}_{25}\) for **1b,e** and **2b,e**; C\({}_{14}\)H\({}_{29}\) for **1c,f** and **2c,f**) are inserted into the system. Additionally, iodide [I\({}^{-}\)], bromide [Br\({}^{-}\)] or bis(trifluoromethane)sulfonimide [TT\({}_{2}\)N\({}^{-}\)] are considered as counterions. The synthesis, metathesis, structure, and liquid crystalline properties of these compounds are discussed on the basis of the tuned structural variables. The thermotropic properties of this series of salts have been investigated by a combination of differential scanning calorimetry and polarized optical microscopy.