Spectrophotometric investigation of interaction between iodine and pentadentate Schiff base ligands

Winning Strategy for Iron-Based ATRP Using In Situ Generated Iodine as a Regulator

“…According to the mechanism shown in Scheme , the reaction of EIPA with FeBr 2 (1 equiv) and TEMPO (1.5 equiv) will eventually yield I 2 , FeBr 2 , and EPA-TEMPO. After 12 h, three peaks around 234, 292, and 368 nm appear in the UV–vis spectrum of the reaction mixture (Figure c, purple line), perfectly matching those of the preconceived three products (I 2 , FeBr 2 , and EPA-TEMPO), either an individual one or their mixture. , Besides, iodine also contributes to a wide visible light wavelength range extended to about 690 nm. We employed the same method to track the reaction of FeBr 3 with Bu 4 NI (1 equiv).…”

“…Next, we attempted to detect the generation of I 2 using the UV–vis analysis, which is a widely used method to detect iodine. , In order to avoid the absorption peak of I 2 being masked by the strong signals of our ligands, the catalyst system was simplified to FeBr 3 /Fe­(0) or FeBr 2 . As shown in Figure S6, the signals of I 2 (around 292 and 368 nm) are detected.…”

“…Furthermore, the polymer obtained with 3/1 ratio of n (EIPA)/ n (FeBr 3 ) [ n (I) 0 / n (Br) 0 = 1/1] was subjected to elemental analysis (Table S8). In literature, ,− in a mixed halide initiating system for traditional ATRP, R-X/Mt-Y (X, Y = Br or Cl), the bulk of the polymer chains is terminated by chlorine because of the stronger alkyl–chloride bond. Accordingly, if FeBr n I 3– n (with the I – from the initiator EIPA during the atom-transfer process) acts as a deactivator (eq ) via a traditional ATRP process rather than I 2 (eq ) to regulate the polymerization, the polymer obtained with 3/1 ratio of n (EIPA)/ n (FeBr 3 ) ( n (I) 0 / n (Br) 0 = 1/1) should be mostly terminated by bromine (path a) because of the stronger alkyl–bromide bond than alkyl–iodide bond.…”

“…After 12 h, three peaks around 234, 292, and 368 nm appear in the UV−vis spectrum of the reaction mixture (Figure 3c, purple line), perfectly matching those of the preconceived three products (I 2 , FeBr 2 , and EPA-TEMPO), either an individual one or their mixture. 55,56 Besides, iodine also contributes to a wide visible light wavelength range extended to about 690 nm. We employed the same method to track the reaction of FeBr 3 S6) and (b) in situ block copolymerization of poly(MMA-b-BMA) (Table S7).…”