New π-Extended Watersoluble Squaraines as Singlet Oxygen ...

2-(N-(4-bromophenylhydrazonomethyl)-1-methylpyrrole (6d). A mixture of 4-
bromophenylhydrazine hydrochloride (3.00 g, 13.42 mmol) and 5a (1.47 g, 13.42 mmol) was
suspended in degassed THF (50 ml) and stirred at room temperature for 6 h under nitrogen
atmosphere. The color turns from light yellow to dark blue. The solvent was removed and the black
sticky residue purified by chromatography (SiO 2, CH 2 Cl 2 ) to give the pure compound as a yellow
powder (1.02 g, 3.67 mmol, 33 %). 1 H NMR (CDCl 3 ) δ 7.68 (1H, s), 7.34 (2H, d, J = 8.8 Hz), 6.88
(2H, d, J = 8.8 Hz), 6.71 (1H, t, J = 2.2 Hz), 6.34 (1H, dd, J = 3.7, 1.8 Hz), 6.14 (1H, dd, J = 3.6,
2.6), 3.96 (3 H, s).
1-[4-pyridyl]-2-(N-(3,6,9-trioxadecyl)-2-pyrrolyl)ethylene (7a). tBuOK (2.56 g, 22.80 mmol)
was added portionwise under nitrogen atmosphere to a solution of 4-picoline (1.93 g, 20.70 mmol)
and 5b (5.00 g, 20.74 mmol) in anhydrous DMF (20 ml). The resulting red solution was stirred at
80 °C for 1 h and at room temperature overnight. The reaction mixture was poured into 200 ml of
crushed ice to give a yellow suspension that was extracted with AcOEt (3 x 200 ml). The combined
organic phase was washed with brine (4 x 200 ml), dried over Na 2 SO 4 and evaporated affording the
product as a dark yellow oil that was used directly without further purification in the subsequent
step (5.00 g, 15.80 mmol, 76.3 %). 1 H NMR (DMSO-d 6 ) δ 8.49 (2H, d, J = 5.5 Hz), 7.27 (2H, d, J =
5.5 Hz), 7.24 (1H, d, J = 16.1 Hz), 6.77 (1H, s, broad), 6.73 (1H, d, J = 16.1 Hz), 6.58 (1H, d, J =
3.5 Hz), 6.17 (1H, t, J = 3.2 Hz), 4.16 (2H, t, J = 5.6 Hz), 3.72 (2H, t, J = 5.6 Hz), 3.59-3.53 (6H,
m), 3.47 (2H, m), 3.23 (3H, s).
1-[4-quinolyl]-2-(N-(3,6,9-trioxadecyl)-2-pyrrolyl)ethylene (7b). tBuOK (1.12 g, 10.01 mmol)
was added portionwise under nitrogen atmosphere to a solution of 4-methylquinoline (1.30 g, 9.10
mmol) and 5b ( 2.20 g, 9.12 mmol) in anhydrous DMF (15 ml). The resulting red fluorescent
solution was stirred at 80 °C for 1 h and at room temperature overnight. The reaction mixture was
poured into 200 ml of crushed ice to give a red-orange suspension that was extracted with AcOEt (3
x 200 ml). The combined organic phase was washed with brine (4 x 200 ml), dried over Na 2 SO 4 and
evaporated affording a red oil that was purified by chromatography (SiO 2 AcOEt) to give the
product as an orange oil (1.92 g, 5.50 mmol, 60.0 %). 1 H NMR (CDCl 3 ) δ 8.85 (1H, d, J = 4.7 Hz),
8.21 (1H, d, J = 8.3 Hz), 7.72 (1H, t, J = 8.5 Hz), 7.55 (1H, d, J = 5.1 Hz), 7.57 (1H, d, J = 8.5 Hz),
7.58 (1H, d, J = 15.8 Hz), 7.31 (1H, d, J = 15.8 Hz), 6.83 (1H, dd, J = 2.5, 1.7 Hz), 6.72 (1H, dd,
3