SYNTHESIS AND PROPERTIES OF PANCHROMATIC BODIPYs WITH DONOR‐ANTENNA GROUPS: A NEW SYNTHETIC ROUTE
1. Synthesis Procedures
Preparation of 8‐(4‐formylphenyl)‐1,3,5,7‐tetramethyl‐2,6‐diethyl‐4,4‐difluoro‐4‐bora‐3a,4a‐
diaza‐s‐indacene 4. 3 (200.0 mg, 0.463 mmol) is dissolved in THF (50 mL) and 5 % HClaq (10 mL) is added. The solution is stirred for 3.5 h. Then CH2Cl2 (100 mL) is added and the solution is washed with diluted NaHCO3 aq (50 mL) and water (4 x 80 mL) until neutrality. The organic phase is dried over Na2SO4, filtered and the solvent is removed under vacuum to yield the pure product. Yield:
189 mg (red solid), 100 %.
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1H‐NMR (300 MHz, CDCl3): δ = 1.00 (t, 6H; 2/6‐CH2CH3), 1.27 (s, 6H; 1/7‐CH3), 2.32 (q, 4H;
2/6‐CH2CH3), 2.56 (s, 6H; 3/5‐CH3), 7.53 (d, 2H; 8‐Har), 8.04 (d, 2H; 8‐Har), 10.14 (s, 1H; COH).
Preparation of 8‐[4‐(2‐carboxy‐2‐cyanovinyl)phenyl]‐1,3,5,7‐tetramethyl‐2,6‐diethyl‐4,4‐
difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene 5. 2‐Cyanoacetic acid (218.7 mg, 2.572 mmol, 7 eq) and 4 (150.0 mg, 0.367 mmol, 1 eq) are dissolved in dry acetonitrile (35 mL) and piperidine (50µL) is added. Then, the solution is heated to reflux for 3 h. The solvent is removed and the residue is dissolved in CH2Cl2 washed with water (4 x 80 mL), dried over Na2SO4 and is concentrated. The raw product is purified by column chromatography with toluene/methanol 5:1 as eluent. Yield after freeze‐drying from 1,4‐dioxane: 158 mg (red‐orange solid, Rf (SiO2; toluene/methanol 5:1) = 0.20), 90 %.
1H‐NMR (300 MHz, DMSO‐d6): δ = 0.94 (t, 6H; 2/6‐CH2CH3), 1.28 (s, 6H; 1/7‐CH3), 2.27 (q, 4H; 2/6‐CH2CH3), 2.44 (s, 6H; 3/5‐CH3), 7.57 (d, 2H; 8‐Har), 8.14 (d, 2H; 8‐Har), 8.27 (s, 1H; Ph‐
CH=C(COOH)(CN)).
Preparation of 8‐[4‐(1,3‐dioxolan‐2‐yl)phenyl]‐1,7‐dimethyl‐3,5‐di[4‐(di(p‐methoxyphenyl)‐
amino)styryl]‐2,6‐diethyl‐4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene 6. To a solution of 3 (100.0 mg, 0.221 mmol, 1 eq) and 4‐(di(4‐methoxyphenyl)amino)‐benzaldehyde (221.1 mg, 0.663 mmol, 3 eq) in benzene (20 mL) are added piperidine (0.3 mL) and glacial acetic acid (0.25 mL). After heating the solution to reflux over a glass frit containing molecular sieve (4 Å) for 11 h, the solvent is removed and the raw product is purified by column chromatography using cyclohexane/ethyl acetate 2:1 as eluent. Yield: 77 mg (green‐black solid, Rf (SiO2; cyclohexane: ethyl acetate 2:1) = 0.30), 32 %.
1H‐NMR (300 MHz, CDCl3): δ = 1.15 (t, 6H; 2/6‐CH2CH3), 1.32 (s, 6H; 1/7‐CH3); 2.61 (q, 4H;
2/6‐CH2CH3), 3.83 (s, 12H; OMe), 4.09‐4.26 (m, 4H, O‐CH2CH2‐O), 5.90 (s, 1H, Ph‐CH), 6.86 (d, 8H;
3/5‐Har), 6.93 (d, 4H; 3/5‐Har), 7.10 (d, 8H; 3/5‐Har), 7.19 (d, 3J1H/1H = 16.4 Hz, 2H; 3/5CH=CH), 7.36 (d, 2H; 8‐Har), 7.42 (d, 4H; 3/5‐Har), 7.64 (d+d, 2H+2H; 3/5CH=CH + 8‐Har).
Preparation of 8‐(4‐formylphenyl)‐1,7‐dimethyl‐3,5‐di[4‐(di(p‐methoxyphenyl)amino)styryl]‐
2,6‐diethyl‐4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene 7. 6 (100.0 mg, 0.092 mmol) is dissolved
in THF (40 mL) and 5 % HClaq (5 mL) is added. The solution is stirred overnight. Then CH2Cl2 (100 mL) is added and the solution is washed with diluted NaHCO3 aq (50 mL) and water (4 x 100 mL) until neutrality. The organic phase is dried over Na2SO4, filtered and the solvent is removed under vacuum to yield the pure product. Yield: 95 mg (green‐black solid), 99 %.
1H‐NMR (300 MHz, CDCl3): δ = 1.16 (t, 6H; 2/6‐CH2CH3), 1.30 (s, 6H; 1/7‐CH3); 2.61 (q, 4H;
2/6‐CH2CH3), 3.83 (s, 12H; OMe), 6.87 (d, 8H; 3/5‐Har), 6.93 (d, 4H; 3/5‐Har), 7.10 (d, 8H; 3/5‐Har), 7.20 (d, 3J1H/1H = 16.6 Hz, 2H; 3/5CH=CH), 7.45 (d, 4H; 3/5‐Har), 7.55 (d, 2H; 8‐Har), 7.64 (d, 3J1H/1H = 16.6 Hz, 2H; 3/5CH=CH), 8.04 (d, 2H; 8‐Har), 10.15 (s, 1H; COH).
Preparation of 8‐[4‐(2‐carboxy‐2‐cyanovinyl)phenyl]‐1,7‐dimethyl‐3,5‐di[4‐(di(p‐methoxy‐
phenyl)amino)styryl]‐2,6‐diethyl‐4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene 8. 2‐Cyanoacetic acid (65.6 mg, 0.772 mmol, 7 eq) and 7 (114.3 mg, 0.110 mmol, 1 eq) are dissolved in dry acetonitrile (35 mL) and three drops of piperidine are added. Then, the solution is heated to reflux for 5 h. The solvent is removed and the residue is dissolved in CH2Cl2 washed with water (4 x 80 mL), dried over Na2SO4 and is concentrated. The raw product is purified by column chromatography with CH2Cl2/methanol 15:1 as eluent. Yield after freeze‐drying from 1,4‐
dioxane: 72 mg (brown‐black solid, Rf (SiO2; CH2Cl2/methanol 15:1) = 0.45), 59 %.
1H‐NMR (300 MHz, DMSO‐d6): δ = 1.07 (t, 6H; 2/6‐CH2CH3), 1.31 (s, 6H; 1/7‐CH3); 2.58 (q, 4H; 2/6‐CH2CH3), 3.76 (s, 12H; OMe), 6.78 (d, 4H; 3/5‐Har), 6.93 (d, 8H; 3/5‐Har), 7.07 (d, 8H;
3/5‐Har), 7.21 (d, 3J1H/1H = 16.6 Hz, 2H; 3/5CH=CH), 7.41 (d + d, 2H + 4H; 3/5CH=CH +3/5‐Har), 7.56 (d, 2H; 8‐Har), 8.10 (d, 2H; 8‐Har), 8.16 (s, 1H; Ph‐CH=C(COOH)(CN)).
Preparation of 8‐[(trimethylsilyl)ethynyl]‐1,3,5,7‐tetramethyl‐2,6‐diethyl‐4,4‐difluoro‐4‐bora‐
3a,4a‐diaza‐s‐indacene 10. Under dry conditions, 3‐ethyl‐2,4‐dimethyl‐1H‐pyrrole (13.664 g, 110.909 mmol, 2 eq) is dissolved in dry CH2Cl2 (300 mL), cooled to ‐5 °C and degassed with argon for 30 min. Then 9 (7.000 g, 55.454 mmol, 1 eq) and one drop of trifluoroacetic acid is added.
The solution instantly becomes orange, and changes the colour firstly to red and then to deep violet. After 1 h 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (12.588 g, 55.454 mmol, 1 eq) is added at RT and stirring is continued overnight. NEt3 (46.4 mL, 332.726 mmol, 6 eq) and 30 min later BF3OEt2 (55.7 mL, 443.635 mmol, 8 eq) are added slowly. Stirring is continued for further 3 h. Then the solvent is removed under reduced pressure and the raw product is purified by
Synthesis and Properties of Panchromatic BODIPYs with Donor‐Antenna Groups:
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column chromatography using cyclohexane/ethyl acetate 13:1 as eluent. Yield: 9.66 g (pink‐black solid, Rf (SiO2; cyclohexane: ethyl acetate 13:1) = 0.49), 44 %.
1H‐NMR (300 MHz, CDCl3): δ = 0.31 (s, 9H; Si(CH)3), 1.06 (t, 6H; 2/6‐CH2CH3), 2.41 (s, 6H;
1/7‐CH3), 2.41 (q, 4H; 2/6‐CH2CH3), 2.51 (s, 6H; 3/5‐CH3).
Preparation of 8‐ethynyl‐1,3,5,7‐tetramethyl‐2,6‐diethyl‐4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐
indacene 11. 10 (400.0 mg, 0.999 mmol, 1 eq) is dissolved in methanol (80 mL), KF (290.2 mg, 4.995 mmol, 5 eq) is added and the reaction solution is stirred for 1.5 h at RT. After full consumption of the starting material, 1% CH3COOHaq (50 mL) is added. Then, CH2Cl2 (150 mL) is added and the organic layer is washed with water (4 x 80 mL) until neutrality. It is dried over
Na2SO4 and the solvent is removed under vacuum. Yield: 327 mg (pink‐black solid), 100 %.
1H‐NMR (300 MHz, CDCl3): δ = 1.07 (t, 6H; 2/6‐CH2CH3), 2.41 (s, 6H; 1/7‐CH3), 2.41 (q, 4H;
2/6‐CH2CH3), 2.52 (s, 6H; 3/5‐CH3), 3.89 (s, 1H; ‐≡H).
Preparation of 2‐cyano‐3‐(4‐iodophenyl)acrylic acid 12. Under dry conditions, 4‐iodo‐
benzaldehyde (7.400 g, 31.894 mmol, 1 eq) is dissolved in benzene (90 mL). Piperidine (0.90 mL), glacial acetic acid (0.75 mL) and 2‐cyanoacetic acid (18.990 g, 0.223 mol, 7 eq) are added. The solution is heated to reflux over a glass frit containing molecular sieve (4 Å) for 40 h. Then, the solvent is removed and the raw product is purified by repetitive recrystallisation from CH2Cl2. Yield: 5.03 g (white solid), 53 %.
1H‐NMR (300 MHz, DMSO‐d6): δ = 7.79 (d, 2H; 2‐Har), 7.98 (d, 2H; 3‐Har), 8.30 (s, 1H; Ph‐
CH=C(COOH)(CN)), 14.04 (s (broad), 1H; COOH). 13C‐NMR (125 MHz, DMSO‐d6): δ = 163.19 (d,
3J1H13C = 6.7 Hz; COOH), 153.46 (d, 1J1H/13C = 162.2 Hz; CH=C(COOH)(CN)), 138.29 (d, 1J1H/13C = 167.6 Hz; 3/5‐Car), 132.06 (d, 1J1H/13C = 162.8 Hz; 2/6‐Car), 130.91 (s; 1‐Car), 115.97 (3J1H/13C = 13.9 Hz; CN), 104.43 (s; CH=C(COOH)(CN)), 101.50 (s; 4‐Car).
Preparation of 8‐[(4‐(2‐carboxy‐2‐cyanovinyl)phenyl)ethynyl]‐1,3,5,7‐tetramethyl‐2,6‐diethyl‐
4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene 13. Under dry and oxygen‐free conditions, 12 (820.0 mg, 2.742 mmol, 3 eq), Pd(PPh3)4 (63.4 mg, 0.055 mmol, 0.06 eq), CuI (6.9 mg,
0.036 mmol, 0.04 eq) and NEt3 (0.60 mL, 4.296 mmol, 4.7 eq) are dissolved in dry THF (13 mL).
Then, 11 (300.0 mg, 0.914 mmol, 1 eq) is dissolved in dry THF (20 mL) and added dropwise over 3 h at RT to the reaction solution. After further 60 min stirring at RT, the solvent is removed. The residue is dissolved in CHCl3 and washed with water (4 x 100 mL). The organic fraction is dried over Na2SO4 and filtered. After removal of the solvent, the raw product is purified by column chromatography with cyclohexane/ethyl acetate 2:1 + 1% of glacial acetic acid, then the solvent is changed to CH2Cl2 followed by a change to CH2Cl2/methanol 20:1 with a gradient to 10:1.
Yield: 218 mg (purple‐black solid, Rf (SiO2; CH2Cl2/methanol 10:1) = 0.50), 48 %.
1H‐NMR (300 MHz, DMF‐d7): δ = 1.07 (t, 6H; 2/6‐CH2CH3), 2.46 (q, 4H; 2/6‐CH2CH3), 2.53 (s, 6H; 3/5‐CH3), 2.58 (s, 6H; 1/7‐CH3), 7.87 (d, 2H; 8‐Har), 8.09 (d, 2H; 8‐Har), 8.29 (s, 1H; Ph‐
CH=C(COOH)(CN)).
Preparation of 8‐[(trimethylsilyl)ethynyl]‐1,7‐dimethyl‐3,5‐di[4‐(di(p‐methoxyphenyl)amino)‐
styryl]‐2,6‐diethyl‐4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene 14. Under dry conditions 4‐(di(4‐
methoxyphenyl)amino)benzaldehyde (1.873 g, 5.620 mmol, 3 eq) is dissolved in dry benzene (40 mL). Piperidine (0.30 mL), glacial acetic acid (0.25 mL) and then 10 (750.0 mg, 1.873 mmol, 1 eq) are added. The reaction solution is heated to reflux over a glass frit containing molecular sieve (4 Å) to remove the formed water. After complete consumption of the starting material (21 h), the solvent is removed and the raw product is purified by column chromatography using CH2Cl2/hexane 9:1 as eluent. Yield: 800 mg (blue‐black solid, Rf (SiO2; CH2Cl2/hexane 9:1) = 0.23), 41 %.
1H‐NMR (300 MHz, benzene‐d6): δ = 0.22 (s, 9H; Si(CH)3), 1.07 (t, 6H; 2/6‐CH2CH3), 2.36 (s, 6H; 1/7‐CH3), 2.55 (q, 4H; 2/6‐CH2CH3), 3.37 (s, 12H; OMe), 6.75 (d, 8H; 3/5‐Har), 6.84 (d, 4H;
3/5‐Har), 7.04 (d, 8H; 3/5‐Har), 7.38 (d, 3J1H/1H = 16.6 Hz, 2H; 3/5CH=CH), 7.48 (d, 4H; 3/5‐Har), 8.42 (d, 3J1H/1H = 16.5 Hz, 2H; 3/5CH=CH).
Preparation of 8‐ethynyl‐1,7‐dimethyl‐3,5‐di[4‐(di(p‐methoxyphenyl)amino)styryl]‐2,6‐diethyl‐
4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene 15. 14 (790.0 mg, 0.766 mmol, 1 eq) is dissolved in THF/methanol 1:1 (80 mL of each), KF (222.6 mg, 3.831 mmol, 5 eq) is added and the reaction solution is stirred for 30 min at RT. Then 1 % CH3COOHaq (50 mL) and CH2Cl2 (150 mL) are added.
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The organic layer is washed with water (4 x 100 mL) until neutrality, dried over Na2SO4, filtered and the solvent is removed under vacuum. Yield: 710 mg (blue‐black solid), 97 %.
1H‐NMR (300 MHz, THF‐d8): δ = 1.24 (t, 6H; 2/6‐CH2CH3), 2.53 (s, 6H; 1/7‐CH3), 2.78 (q, 4H; 2/6‐CH2CH3), 3.80 (s, 12H; OMe), 4.69 (s, 1H; ‐≡H), 6.88 (d + d, 4H + 8H; 3/5‐Har), 7.08 (d, 8H;
3/5‐Har), 7.28 (d, 3J1H/1H = 16.7 Hz, 2H; 3/5CH=CH), 7.41 (d, 4H; 3/5‐Har), 7.63 (d, 3J1H/1H = 16.6 Hz, 2H; 3/5CH=CH).
Preparation of 8‐[(4‐(2‐carboxy‐2‐cyanovinyl)phenyl)ethynyl]‐1,7‐dimethyl‐3,5‐di[4‐(di(p‐
methoxyphenyl)amino)styryl]‐2,6‐diethyl‐4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene 16.
Under dry and oxygen‐free conditions, 12 (280.1 mg, 0.939 mmol, 3 eq), Pd(PPh3)4 (21.7 mg, 0.019 mmol, 0.06 eq), CuI (2.4 mg, 0.013 mmol, 0.04 eq) and NEt3 (0.20 mL, 1.408 mmol, 4.5 eq) are dissolved in dry THF (15 mL). Then, 15 (300.0 mg, 0.313 mmol, 1 eq) is likewise dissolved in dry THF (20 mL) and added dropwise over 3 h at RT to the reaction solution. After further 60 min stirring at RT, the solvent is removed. The raw product is purified by column chromatography starting with cyclohexane/ethyl acetate 2:1 + 1 % of glacial acetic acid, then the solvent is changed to CH2Cl2 followed by a change to CH2Cl2:methanol 20:1 with a gradient to 10:1. The product fractions are collected and concentrated. The pure product is precipitated from ethanol, washed with ethanol, methanol, hexane and water. Yield: 170 mg (green‐black solid, Rf (SiO2; CH2Cl2/methanol 10:1) = 0.41), 48 %.
1H‐NMR (300 MHz, DMSO‐d6): δ =1.13 (t, 6H; 2/6‐CH2CH3), 2.49 (s, 6H; 1/7‐CH3), 2.67 (q, 4H; 2/6‐CH2CH3), 3.75 (s, 12H; OMe), 6.76 (d, 4H; 3/5‐Har), 6.92 (d, 8H; 3/5‐Har), 7.05 (d, 8H; 3/5‐
Har), 7.20 (d, 3J1H/1H = 16.4 Hz, 2H; 3/5CH=CH), 7.38 (d, 3J1H/1H = 16.9 Hz + d, 2H + 4H; 3/5CH=CH + 3/5‐Har), 7.72 (d, 2H; 8‐Har), 7.95 (d, 2H; 8‐Har), 8.00 (s, 1H; Ph‐CH=C(COOH)(CN)).