## 2 Materials and Methods
### Amidation  
General procedure. The chlorophyll substrate (10 mmol), dissolved in tetrahydrofuran (THF, 10 mL), was added dropwise to formamide (FA) (20, 40, or 60 mmol, for one, two, or three chloromethyl groups, respectively), which was kept at 60 \({}^{\circ}\)C inside a round-bottomflask. The reaction mixture was then stirred at reflux for 3 h. Once cooled to RT, the mixture was washed with brine (3 \(\times\) 10 mL) and dried over sodium sulfate. The product was obtained by vacuum-drying. _N_-(5-formyl-2-hydroxy-3-methoxybenzyl)formamide (**3a**): Following the general procedure, **2a** (10 mmol) and FA (20 mmol) afforded the monoamide product as a brown thick liquid, in 99% yield. \({}^{1}\)H NMR (400 MHz, CDCl\({}_{3}\)) \(\delta\)(ppm): 9.84 (s, 1H, Ar-C(=O)H), 8.17 (s, 1H, N-C(=O)H), 7.51 (d, 1H, Ar-H), 7.42 (d, 1H, Ar-H), 6.47 (br s, 1H, Ar-OH), 5.33 (s, 2H, Ar-CH\({}_{2}\)-N), 3.99 (s, 3H, O-CH\({}_{3}\)). EA found: C 57.54%, H 5.13%, N 6.83%; calcd for (C\({}_{10}\)H\({}_{11}\)NO\({}_{4}\)): C 57.41%, H 5.30%, N 6.70%. \(N\),_N_-(5-formyl-4-hydroxy-1,3-phenylene)bis(methylene))diformamide (**3b**): Following the general procedure, **2b** (10 mmol) and FA (40 mmol) afforded the diamide product as a pale yellow thick liquid, in 98% yield. \({}^{1}\)H NMR (600 MHz, CDCl\({}_{3}\)) \(\delta\)(ppm): 11.43 (s, 1H, Ar-OH), 9.92 (s, 1H, Ar-C(=O)H), 8.17 (s, H, o-N-C(=O)H), 8.13 (s, H, pC-N-C(=O)H), 7.65 (d, 1H, Ar-H), 7.61 (d, 1H, Ar-H), 5.31 (s, 2H, Ar-OCH\({}_{2}\)-N), 5.19 (s, 2H, Ar-pCH\({}_{2}\)-N), EA found: C 56.05%, H 5.21%, N 11.99%; calcd for (C\({}_{11}\)H\({}_{12}\)N\({}_{2}\)O\({}_{4}\)): C 55.93%, H 5.12%, N 11.86%. _N_-(5-acetyl-2-hydroxybenzyl)formamide (**3c**): Following the general procedure, **2c** (10 mmol) and FA (20 mmol) afforded the monoamide product as a pale pink thick liquid, in 97% yield. \({}^{1}\)H NMR (400 MHz, CDCl\({}_{3}\)) \(\delta\)(ppm): 8.16 (s, H, N-C(=O)H), 7.96 (d, 1H, Ar-H), 6.97 (d, 1H, Ar-H), 6.97 (d, 1H, Ar-H), 5.87 (br s, 1H, Ar-OH), 5.27 (s, 2H, Ar-CH\({}_{2}\)-N), 2.56 (s, 3H, CH\({}_{3}\)-(C=O)-Ar). EA found: C 62.36%, H 5.65%, N 7.40%; calcd for (C\({}_{10}\)H\({}_{11}\)NO\({}_{3}\)): C 62.17%, H 5.74%, N 7.25%. \(N\),_N_-((5-acetyl-2-hydroxy-1,3-phenylene)bis(methylene))diformamide (**3c**): Following the general procedure, **2c** (10 mmol) and FA (40 mmol) afforded the monoamide product as a pale pink thick liquid, in 92% yield. \({}^{1}\)H NMR (400 MHz, CDCl\({}_{3}\)) \(\delta\)(ppm): 8.16 (s, 2H, N-C(=O)H), 7.99 (s, 2H, Ar-H), 5.75 (br s, 1H, Ar-OH), 5.28 (d, 2H, Ar-CH\({}_{2}\)-N), 2.57 (s, 3H, CH\({}_{3}\)-(C=O)-Ar). EA found: C 57.43%, H 5.78%, N 11.02%; calcd for (C\({}_{12}\)H\({}_{14}\)N\({}_{2}\)O\({}_{4}\)): C 57.59%, H 5.64%, N 11.19%. \(N\),_N_-((6-allyl-3-hydroxy-4-methoxy-1,2-phenylene)bis(methylene))diformamide (**3d**): Following the general procedure, **2d** (10 mmol) and FA (20 mmol) afforded the diamide product as a dark thick liquid, in 94% yield. \({}^{1}\)H NMR (400 MHz, CDCl\({}_{3}\)) \(\delta\)(ppm): 8.10 (s, 1H, N-C(=O)H), 8.06 (s, 1H, N-C(=O)H), 6.75 (s, 1H, Ar-H), 5.91 (m, 1H, C-CH=C), 5.43 (s, 2H, Ar-CH\({}_{2}\)-N), 5.28 (s, 2H, Ar-CH\({}_{2}\)-N), 5.07 (dd, 1H, -C=CH\({}_{2}\)), 4.97 (dd, 1H, -C=CH\({}_{2}\)), 3.91 (s, 3H, Ar-OCH\({}_{3}\)), 3.44 (dt, 2H, Ar-CH\({}_{2}\)-C=C). EA found: C 61.03%, H 5.69%, N 9.96%; calcd for (C\({}_{14}\)H\({}_{16}\)N\({}_{2}\)O\({}_{4}\)): C 60.86%, H 5.84%, N 10.14%. \(N\),\(N\),_N_-_((4-hydroxy-5-methoxybenzene-1,2,3-triyl)tris(methylene))triformamide (**3e**). Following the general procedure, **2e** (10 mmol) and FA (60 mmol) afforded the triamide product as a dark thick liquid, in 96% yield. \({}^{1}\)H NMR (400 MHz, CDCl\({}_{3}\)) \(\delta\)(ppm): 8.10 (s, H, N-C(=O)H), 8.09 (s, H, N-C(=O)H), 8.06 (s, H, N-C(=O)H), 6.98 (s, 1H, Ar-H), 6.14 (s, 1H, Ar-OH), 5.45 (s, 2H, Ar-CH\({}_{2}\)-N), 5.38 (s, 2H, Ar-CH\({}_{2}\)-N), 5.30 (s, 2H, Ar-CH\({}_{2}\)-N), 3.94 (s, 3H, Ar-OCH\({}_{3}\)).