Table 2. Band Assignments for the PDA Phaseb.
| wavenumber (cm–1) | intensity | band assignment | molecular structure | structure unit | refs |
|---|---|---|---|---|---|
| 3612–3140 | w-m, broad | ν(OH) | O–H | phenolic 36 | (66) |
| ν(NH) | N–H | ||||
| 3033 | m, broad | ν(CH) | aromatic C–H | aromatic ring, pyrrole, indole | (66) |
| 2963 | w | νas(CH) | CH3 | (66) | |
| 2954 | w | νas(CH) | CH2 | (66) | |
| 2916 | m | νs(CH) | CH3 | (66) | |
| 2850 | m | νs(CH) | CH2 | (66) | |
| 1725 | w-m | ν(C=O) | carbonyl group | (66, 68) | |
| 1574 | s | ν(C–C), δ(C–H) | ring | aromatic ring, pyrrole, indole, catechol | (66, 70) |
| 1502 | vs | ν(C–C), ν(C=N) | aromatic C–C, C=N | aromatic ring, pyrrole, indole | (66, 68) |
| 1472 | w | ν(C=C) | C–H | pyrrole, indole ring | (68, 75) |
| 1436 | s | νring(C–C) + ν(C–N) + δ(O–H), δ(C–H) + δ(N–H) + ν(C–N) | C–H, C–N, O–H | aliphatic CHx indole ring | (66, 67, 69) |
| 1347 | m | νring(C–C) + ν(C–N) + δ(O–H) | C–N, O–H, aromatic ring, C–N–C | aliphatic CHx, indole ring | (66, 67, 75) |
| 1266 | w | ν(C–O) + δ(N–H) + δ(C–H), ν(C–O) + δ(C–H) + δring | C–O | catechol | (66, 68−70) |
| 1198 | s | δ(OH) + δ(CH), ν(C–O) | C–O–C, C–O | (66) | |
| 1153 | w | δ (OH) + δ(CH), ν(C–O) | C–O | (66) | |
| 1115 | w | δ(OH) + δ(CH) +ν(C–O) | C–O | (66) | |
| 1035 | w | δ(CH) + δ(NH) + ν(C–O) | aromatic ring | indole ring | (66) |
| 954 | m | δring + δ(C–H) | indole ring | (66) | |
| 864 | m | γ(C–H) | indole ring | (66, 67) | |
| 807 | s | γ(C–H) + γring | indole ring | (66, 67) | |
| 632 | w | ||||
| 589 | w | ||||
| 455 | m |
b
Abbreviations for band intensities. vw: very weak; w: weak; m: medium; s: strong; vs: very strong.