Chemical Science
Edge Article
366.2393; found 366.2408; FT-IR (thin lm): nmax/cmꢀ1 2972, 4.48 (s, 2H), 3.53 (q, 2H, J ¼ 7), 1.22 (t, 3H, J ¼ 7); 13C NMR (100
2934, 2874, 1636, 1460, 1433, 1380, 1350, 1265, 1219, 1010.
MHz, CDCl3): dC ¼ 149.1, 149.0, 135.3, 134.0, 123.3, 70.1, 66.1,
Ligand L9f. Sodium hydride (60% dispersion in mineral oil, 15.1; HRMS (ES+): calcd for C8H12NO: 138.0919; found
1.04 g, 26.1 mmol) was added to ethyl glycolate (1.48 g, 14.2 138.0918; FT-IR (thin lm): nmax/cmꢀ1 2976, 2867, 1578, 1479,
mmol) in anhydrous tetrahydrofuran (90 mL) at 0 ꢃC. The 1427, 1374, 1094, 1027, 789, 712.
reaction suspension was stirred for 30 minutes at 0 ꢃC and then
Ligand L10b. Sodium hydride (60% dispersion in mineral
3-(bromomethyl)pyridine hydrobromide (3.00 g, 11.9 mmol) oil, 1.37 g, 34.3 mmol) was added to ethanol (1.70 mL, 29.4
was added in portions. The reaction mixture was allowed to mmol) in anhydrous tetrahydrofuran (50 mL) at 0 ꢃC under the
warm to room temperature, stirred for 16 hours and then protection of nitrogen. The reaction suspension was stirred at
ꢃ
quenched with water (50 mL). The reaction mixture was then 0 C for 20 minutes and then 3 (1.68 g, 4.90 mmol) was added
extracted with ethyl acetate (2 ꢁ 150 mL) and the combined slowly. The reaction mixture was allowed to warm to room
organic layers were washed with water (30 mL), brine (30 mL), temperature, stirred overnight. The solvent was removed on a
dried with magnesium sulfate. The solvent was removed on a rotary evaporator and the residue was dissolved in ethyl acetate
rotary evaporator and the residue was puried on silica eluting (150 mL), washed with water (15 mL), brine (30 mL), dried over
with hexane–ethyl acetate (100 : 0 to 60 : 40). The product was sodium sulfate. The solvent was removed on a rotary evaporator
isolated as a colorless oil (0.97 g, 42%); 1H NMR (400 MHz, and the residue was puried on silica eluting with hexane–ethyl
CDCl3): dH ¼ 8.58 (d, 1H, J ¼ 2), 8.54 (dd, 1H, J ¼ 5, J ¼ 2), 7.74 acetate (60 : 40 to 15 : 85). The product was isolated as a
(dt, 1H, J ¼ 8, J ¼ 2), 7.29 (dd, 1H, J ¼ 8, J ¼ 5), 4.64 (s, 2H), 4.22 colorless oil (0.28 g, 29%); 1H NMR (400 MHz, CDCl3): dH ¼ 8.48
(q, 2H, J ¼ 7), 4.12 (s, 2H), 1.28 (t, 3H, J ¼ 7); 13C NMR (100 MHz, (d, 2H, J ¼ 2), 7.66 (s, 1H), 4.50 (s, 4H), 3.54 (q, 4H, J ¼ 7), 1.23 (t,
CDCl3): dC ¼ 169.9, 149.3, 149.2, 135.6, 132.6, 123.3, 70.7, 67.4, 6H, J ¼ 7); 13C NMR (100 MHz, CDCl3): dC ¼ 148.3, 134.7, 133.8,
60.8, 14.0; HRMS (ES+): calcd for C10H14NO3: 196.0974; found 70.0, 66.1, 15.1; HRMS (ES+): calcd for C11H18NO2: 196.1338;
196.0966; FT-IR (thin lm): nmax/cmꢀ1 1748, 1579, 1427, 1388, found 196.1329; FT-IR (thin lm): nmax/cmꢀ1 2975, 2864, 1582,
1271, 1207, 1126, 1028, 794, 713.
1434, 1373, 1351, 1161, 1095, 1030, 712.
Ligand L10f. Sodium hydride (60% dispersion in mineral
oil, 0.58 g, 14.4 mmol) was added to ethyl glycolate (1.25 g, 12.0
mmol) in anhydrous tetrahydrofuran (50 mL) at 0 ꢃC. The
reaction suspension was stirred for 20 minutes at 0 ꢃC and
then 3 (0.72 g, 2.08 mmol) was added slowly. The reaction
mixture was allowed to warm to room temperature, and stirred
overnight. The solvent was removed under on a rotary evapo-
rator and the residue was dissolved in ethyl acetate (150 mL),
washed with water (15 mL), brine (30 mL), dried with sodium
sulfate. The solvent was removed on a rotary evaporator and
the residue was puried on silica eluting with hexane–ethyl
acetate (50 : 50 to 5 : 95). The product was isolated as a col-
ourless oil (0.35 g, 54%); 1H NMR (400 MHz, CDCl3): dH ¼ 8.51
(d, 2H, J ¼ 2), 7.77–7.75 (m, 1H), 4.63 (s, 4H), 4.20 (q, 4H, J ¼ 7),
4.10 (s, 4H), 1.26 (t, 6H, J ¼ 7); 13C NMR (100 MHz, CDCl3): dC ¼
170.0, 148.8, 135.3, 132.7, 70.7, 67.7, 61.0, 14.2; HRMS (ES+):
calcd for C15H22NO6: 312.1447; found 312.1443; FT-IR (thin
lm): nmax/cmꢀ1 2983, 1747, 1582, 1433, 1384, 1274, 1202,
1119, 1025, 712.
Automated UV/Vis absorption titrations
UV/Vis titrations were carried out using a BMG FLUOstar
Omega plate reader equipped with a UV/Vis detector and
equilibrated at 298 K. A 5 mL solution of porphyrin was
prepared at known concentration (1–5 mM) in spectroscopic
grade solvent. A 10 mL solution of ligand was prepared at
known concentration (8–40 000 mM) using spectroscopic grade
solvent. 150 mL of the porphyrin solution was added to a well of
a Hellma quartz microplate, and the absorbance at ve wave-
lengths was recorded. Aliquots of the ligand solution (3, 6 or 10
mL) were successively added to the well, and the absorbance was
recorded aer each addition. Changes in absorbance were t to
a 1 : 1 binding isotherm in Microso Excel to obtain the asso-
ciation constant. Each titration was repeated at least three
times, and the experimental error is quoted as twice the stan-
dard deviation at a precision of one signicant gure.
Manual uorescence titrations
Ligand L9b. Sodium hydride (60% dispersion in mineral oil,
1.00 g, 26.9 mmol) was added to ethanol (1.20 mL, 20.2 mmol) Fluorescence titrations were carried out using a Hitachi F-4500
in anhydrous tetrahydrofuran (50 mL) at 0 ꢃC under the Fluorescence Spectrophotometer at 298 K. A 10 mL solution of
protection of nitrogen. This reaction suspension was stirred for porphyrin at known concentration (0.04–0.05 mM) was prepared
20 minutes at 0 ꢃC and then 3-(bromomethyl)pyridine hydro- in spectroscopic grade solvent. Then, 2 mL of this host solution
bromide (1.70 g, 6.72 mmol) was added slowly. The reaction was loaded into a 1 cm path length uorescence cuvette, and the
mixture was allowed to warm to room temperature, stirred uorescence emission spectra was recorded from 500 to 750 nm
overnight. The solvent was removed on a rotary evaporator and exciting at 427 nm. A 2 mL solution of ligand (0.1–1 mM) was
the residue was dissolved with ethyl acetate (150 mL), washed prepared using the host stock solution, so that the concentra-
with water (15 mL), brine (30 mL), dried with sodium sulfate. tion of host remained constant throughout the titration.
The solvent was removed on a rotary evaporator and the residue Aliquots of ligand solution were added successively to the
was puried on silica eluting with hexane–ethyl acetate (55 : 45 cuvette, and the emission spectrum was recorded aer each
to 45 : 55). The product was isolated as a yellow oil (0.43 g, 47%); addition. Changes in uorescence emission were t to a 1 : 1
1H NMR (400 MHz, CDCl3): dH ¼ 8.54 (d, 1H, J ¼ 2), 8.50 (dd, 1H, binding isotherm in Microso Excel to obtain the association
J ¼ 5, J ¼ 2), 7.65 (dt, 1H, J ¼ 8, J ¼ 2), 7.24 (dd, 1H, J ¼ 8, J ¼ 5), constant. Each titration was repeated at least three times, and
1452 | Chem. Sci., 2015, 6, 1444–1453
This journal is © The Royal Society of Chemistry 2015