## Materials and Methods
#### Synthesis of Perfluoroheptyl 1,2,4-Oxadiazolylpyridinium Salts **1a-c** and **2a-c**  
The salts **1a-c** and **2a-c** were synthesized according to Scheme 1 by 5-(Perfluoroheptyl)-3-(pyridin-4-yl)-1,2,4-oxadiazole **(1)** or 3-(Perfluoroheptyl)-5-(pyridin-4-yl)-1,2,4-oxadiazole **(2)** (100 mg, 0.1941 mmol) in acetonitrile (5 mL, Sigma-Aldrich, St. Louis, MO, USA) and by subsequent addition of 5 mole eq. 1-iododecane (98%, Sigma-Aldrich) **(1a, 2a)**, 1-bromododecane (97%, Sigma-Aldrich, St. Louis, MO, USA) **(1b, 2b)** or 1-bromotetadecane(97%, Sigma-Aldrich, St. Louis, MO, USA) (**1c, 2c**), respectively. The mixture was stirred in an oil bath for one week at 80 \({}^{\circ}\)C. The reaction was monitored by TLC (petroleum ether and ethyl acetate 2:1 (Sigma-Aldrich and 99.9% VWR-Chemicals, respectively)). After cooling, the mixture was dried under vacuum. Impurities were extracted with petroleum ether (Sigma-Aldrich, St. Louis, MO, USA) several times and the product was dried under vacuum. Dissolving in acetonitrile (Sigma-Aldrich, St. Louis, MO, USA) and drying under vacuum yielded the desired products.  
**1-decyl-4-(5-(perfluoroheptyl)-1,2,4-oxadiazol-3-yl) pyridin-1-ium iodide (1a)**: Orange solid. Yield: 88%. 1H-NMR (300 MHz, CD\({}_{3}\)CN) 8: 9.96 (d, J = 6.8 Hz, 2H, Ar), 8.64 (d, J = 6.2 Hz, 2H, Ar), 4.64 (t, J = 7.7 Hz, 2H), 1.34 (m, 16H), 0.89 (t, J = 7 Hz, 3H). MS analysis: Calc.: 656.1752 g mol\({}^{-1}\), exp.: 656.1759 g mol\({}^{-1}\).  
**1-dodecyl-4-(5-(perfluoroheptyl)-1,2,4-oxadiazol-3-yl) pyridin-1-ium bromide (1b)**: White solid. Yield: 77%. 1H-NMR (300 MHz, CDCl\({}_{3}\)) 8: 9.75 (d, J = 5.9 Hz, 2H, Ar), 8.70 (d, J = 5.8 Hz, 2H, Ar), 5.20 (t, J = 7.2 Hz, 2H), 2.11 (q, 2H), 1.32 (m, 18H), 0.89 (t, J = 6.0 Hz, 3H). MS analysis: Calc.: 684.2065 g mol\({}^{-1}\), exp.: 684.2042 g mol\({}^{-1}\).  
**1-tetradecyl-4-(5-(perfluoroheptyl)-1,2,4-oxadiazol-3-yl) pyridin-1-ium bromide (1c)**: White solid. Yield: 63%. 1H-NMR (300 MHz, CDCl\({}_{3}\)) 8: 9.74 (d, J = 6.4 Hz, 2H, Ar), 8.69 (d, 2H, J = 6.9 Hz, Ar), 5.18 (t, J = 7.3 Hz, 2H), 2.09 (q, J = 7 Hz, 2H), 1.31 (m, 22H), 0.89 (t, J = 6.5 Hz, 3H). MS analysis: Calc.: 712.2378 g mol\({}^{-1}\), exp.: 712. 2370 g mol\({}^{-1}\).  
**1-decyl-4-(3-(perfluoroheptyl)-1,2,4-oxadiazol-5-yl) pyridin-1-ium iodide (2a)**: Orange/red solid. Yield: 93%. 1H-NMR (300 MHz, CDCl\({}_{3}\)) 8: 9.75 (d, J = 6.5 Hz, 2H, Ar), 8.78 (d, J = 6.6 Hz, 2H, Ar), 5.09 (t, J = 7.5 Hz, 2H), 1.32 (m, 16H), 0.88 (t, J = 6.6 Hz, 3H). MS analysis: Calc.: 656.1752 g mol\({}^{-1}\), exp.: 656.1764 g mol\({}^{-1}\).  
**1-dodecyl-4-(3-(perfluoroheptyl)-1,2,4-oxadiazol-5-yl) pyridin-1-ium bromide (2b)**: White solid. Yield: 63%. 1H-NMR (300 MHz, CD\({}_{3}\)CN) 8: 9.80 (d, J = 6.6 Hz, 2H, Ar), 8.73 (d, J = 6.5 Hz, 2H, Ar), 5.19 (t, J = 7.4 Hz, 2H), 2.12 (q, 2H), 1.26 (m, 20H), 0.89 (t, J = 6.6 Hz, 3H). MS analysis: Calc.: 684.2065 g mol\({}^{-1}\), exp.: 684.2045 g mol\({}^{-1}\).  
**1-tetradecyl-4-(3-(perfluoroheptyl)-1,2,4-oxadiazol-5-yl) pyridin-1-ium bromide (2c)**: White solid. Yield: 49%. 1H-NMR (300 MHz, CD\({}_{3}\)CN) 8: 9.80 (d, J = 5.9 Hz, 2H, Ar), 8.74 (d, J = 6.1 Hz, 2H, Ar), 5.20 (t, J = 7.3 Hz, 2H), 1.26 (m, 24H), 0.88 (br s, -). MS analysis: Calc.: 712.2378 g mol\({}^{-1}\), exp.: 712. 2374 g mol\({}^{-1}\).