The general procedure for the synthesis of 4'-(4-aminophenyl)-2,2':6',2''-terpyridine from 4'-(4-nitrophenyl)-2,2':6',2''-terpyridine is as follows: the synthesis was carried out by referring to the method reported by Das et al. with appropriate modifications [30]. The procedure was as follows: in a 500 mL round bottom flask, 0.95 g of 4'-(4-nitrophenyl)-2,2':6',2''-terpyridine (2.7 mmol), 250 mg of palladium-carbon catalyst (5% Pd loading), and 200 mL of anhydrous ethanol were added. The resulting suspension was purged with argon for 15 min, followed by refluxing under argon protection. 3.4 mL of hydrazine monohydrate (3.5 g, 70 mmol) was added to the reaction system and refluxing was continued under argon protection for 2 h until 4'-(4-nitrophenyl)-2,2':6',2''-terpyridine was completely dissolved. After completion of the reaction, the reaction solution was cooled to room temperature, the catalyst was removed by vacuum filtration through a short column of diatomaceous earth and the filter cake was washed with dichloromethane (3 x 100 mL). The filtrate was concentrated under reduced pressure to about 75 mL until white needle-like crystals were observed to start precipitating. Subsequently, the saturated solution was placed at 4 °C for overnight crystallization. The precipitated crystals were collected by vacuum filtration and washed with cold ethanol (3 x 50 mL) to give the final 4'-(4-aminophenyl)-2,2':6',2''-terpyridine as white needle-like crystals. Yield: 547 mg (1.7 mmol, 63% yield). The 1H NMR spectrum of the product was in agreement with data reported in the literature [30].
