## 3 Results and Discussion
### Thermotropic Liquid Crystalline Phase Behavior  
The thermotropic liquid crystalline phase behavior of the salts has been characterized using a combination of differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The DSC analyses were conducted at first to obtain a clear picture about the thermal behavior of the samples. Afterwards, POM was used to examine the samples very carefully to determine the mesophase types exhibited by the samples. Starting with the precursor perfluoroheptyl 1,2,4-oxadiazolylpyridinium salts with iodide or bromide as counterion, the melting points for **1a-c** and **2b-c** could not be determined in the DSC traces, indicating decomposition before melting--except for sample 2a. Furthermore, no melting points were observed during the POM analyses, indicating that these salts decompose at temperatures higher than 200 \({}^{\circ}\)C. In the previous study about the salts containing 1,2,4-oxadiazol connected through its C(5) or C(3) to an \(N\)-methylated 4-pyridyl moiety and a perfluoroheptyl chain, a demethylation reaction was experimentally observed, which is likely through a retro \(S_{\text{N}}2\) mechanism [10]. Similarly, this has been reported for imidazolium halides and could justify the instability at higher temperatures of the alkylated salts **1a-c** and **2b-c** having iodide and bromide as counterion [21]. Only the salt **2a** with iodide as the counter ion possesses an ionic liquid crystalline phase behavior in the POM analysis as well as in the DSC traces. However, this is not further discussed as the halide salts are considered as precursors for the preparation of ILCs observed by following metathesis due to the envisaged LC properties. In fact, the alkylation with alkyl halides is efficient and feasible to obtain the precursors salts, since the halides act as good leaving groups. Importantly, the metathesis resulting in [Tf\({}_{2}\)N\({}^{-}\)] as the counterion is necessary to lower the melting point of the salts and stress the structure in order to observe ionic liquid crystalline phase behavior. In our preliminary metathesis experiments with different counterions such as hexafluorophosphate, we did not detect in any case ionic liquid or liquid crystal behavior. We observed thermal degradation of the samples, and this observation lead us to exclude those different counterions from this study set. A possible explanation for the thermal instability could be related to the coordinating ability of the anion: the decomposition temperature is following the order of Cl\({}^{-}<\) [BF\({}_{4}\)\({}^{-}\)] \(\sim\) [PF\({}_{6}\)\({}^{-}\)] \(<\) [Tf\({}_{2}\)N\({}^{-}\)], which is inversely proportional to the tendency to form a stable alkyl-X species. Moreover, increasing the anion size reduces the Coulombic attraction contributions to the lattice energy of the crystal, which leads to lower melting points and explains the choice of the bigger anion [Tf\({}_{2}\)N\({}^{-}\)] [22]. After the metathesis, the six salts **1d-f** and **2d-f** with [Tf\({}_{2}\)N\({}^{-}\)] as the counterion were investigated by means of DSC. While the precursor salts, except of **2a**, were identified as not mesomorphic, the DSC traces for all salts with [Tf\({}_{2}\)N\({}^{-}\)] as the counterion show relevant events on heating (endotherm) and cooling (exotherm) as shown in the second heating and cooling cycle for all six salts in Figure 1. All salts possess, at least, three reversible transitions in the cooling and heating cycles. Concentrating on the cooling cycles, three relevant events are observed for each salt, whereby the second transition seems to be the most pronounced. Considering the temperatures of the second transition, they seem not to shift drastically within each of the salt series **1d-f** and **2d-f**. The temperatures of the first and third transition instead shift to higher temperatures for the longer alkyl chain within the series.