Fig. 4. Gels formed by compound 18 with different metal ions (a–d) and vitamin B₂ (e–f) in DMSO : H₂O (v/v 1 : 8). The molar ratio of gelator 18 to the metal ions are 1 : 5 for (a–d). The vitamin B₂ to gelator molar ratio was 1 : 19 in (e) and 1 : 2 in (f).