**2.1 Materials**

2-Bromo-5-nitro-1,3-bis(trifluoromethyl)benzene (**1**) and 2,6-bis (trifluoromethyl)benzidine (**3**) were synthesized as reported in our previous papers [31, 48]. The aromatic tetracarboxylic dianhydrides of pyromellitic dianhydride (PMDA), 3,30 ,4,40 -biphenyltetracarboxylic dianhydride (BPDA), 3,30 ,4,40 -benzophenone-tetracarboxylic dianhydride (BTDA), 4,40 -oxydiphthalic anhydride (ODPA), and 4,40 -hexafluoroisopropylidenediphthalic anhydride (6-FDA) were purified by vacuum sublimation. *m*-Cresol was stirred in the presence of P2O5 overnight and then distilled under reduced pressure. All other commercially available reagent-grade chemicals were used without further purification.
