Oxidation of dipyrromethane 8 to dipyrromethene 9
(CDCl3) d 7.12 (dd, 1H, J = 1.8 Hz, J = 8.4 Hz, H-11), 6.92
(d, 1H, J = 2.1 Hz, H-7), 6.89 (d, 1H, J = 8.8 Hz, H-10), 6.76
(d, 2H, J = 4.0 Hz, H-2/3), 6.27 (d, 2H, J = 4.0 Hz, H-2/3),
4.65 (s, 2H, OCH2), 4.28 (s, 4H, NCH2), 3.79 (s, 9H, OCH3),
To a solution of 1 eq. of dipyrromethane 8, a solution of 1 eq. of
p-chloranil in dichloromethane was added. The reaction mixture
was stirred for 1 h, the solvent removed by distillation and the
residue chromatographed on silica using dichloromethane and
gradually increasing the polarity by adding ethyl acetate (up to
10% (v) EtOAc).
2.65 (s, 6H, H-m1); 13C NMR (CDCl3) d 171.92 (s, NCH2C O),
=
=
169.05 (s, OCH2C O), 157.40 (s, C-1/4), 148.68 (s, C-8), 141.72
(s, C-9), 134.68 (s, C-1/4), 130.58 (d, C-7), 127.82 (s), 125.63
(d, C-10), 119.52 (d, C-11), 118.57 (d, C-2), 116.89 (d, C-3),
66.13 (t, CH2O), 54.05 (t, CH2N), 52.64 (q, OCH3(O)), 52.3
(q, OCH3(N)), 15.24 (q, m1-C); MS (EI, 70 eV) m/z 544 (M+,
11), 543 (M+, 38), 542 (M+, 9), 511 (3), 485 (28), 484 (100),
483 (24), 470 (2). HRMS (EI+): calcd for C26H28BF2N3O7 (M+)
543.19884; found 543.19774.
Trimethyl 1,9-bis-(4-methoxyphenyl)-5-(3-hydroxy-4-
aminophenyl-N,N,O-triacetate)dipyrromethene (9)
Trimethyl 4,4-difluoro-8-(3-hydroxy-4-aminophenyl-N,N,O-
triacetate)-3,5-bis-(4-methoxyphenyl)-4-bora-3a,4a-diaza-s-
indacene (11)
Deep blue crystals, 100 mg (90%); mp 53 ◦C; 1H NMR (CDCl3) d
7.86 (d, 4H, J = 8.8 Hz, H–P2), 7.15 (dd, 1H, J = 1.4, J = 8.0 Hz,
H-11), 7.02 (d, 4H, J = 8.8 Hz, H–P3), 6.99 (d, 1H, J = 1.4 Hz,
H-7), 6.90 (d, 1H, J = 8.0 Hz, H-10), 6.77 (d, 2H, J = 4.4 Hz,
H-3), 6.73 (d, 2H, J = 4.4 Hz, H-2), 4.67 (s, 2H, OCH2), 4.32
(s, 4H, NCH2), 3.89 (s, 6H, PhOCH3), 3.80 (s, 6H, OCH3(N)),
3.78 (s, 3H, OCH3(O)), NH is not seen; 13C NMR (CDCl3) d
Deep blue crystals, 80 mg (74%); mp 80 ◦C; recrystallized
three times from chloroform–cyclohexane mixture; H NMR
=
=
172.20 (s, NCH2C O), 169.37 (s, OCH2C O), 160.64 (s, C–P4),
153.86 (s, C-1/4), 148.49 (s, C-8), 141.57 (s, C-1/4), 140.52 (s,
C-9), 131.40 (s, C-5), 130.26 (d, C-3), 128.00 (d, C–P2), 126.45 (s,
C–P1), 126.05 (d, C-11), 125.29 (s, C-6), 118.39 (d, C-7), 117.37
(d, C-10), 115.24 (d, C-2), 114.84 (d, C–P3), 66.15 (t, CH2O),
55.83 (q, PhOCH3) 54.04 (t, CH2N), 52.61 (q, OCH3(O)), 52.35
(q, OCH3(N)); MS (EI 70 eV) m/z 679 (M+, 90), 680 (M+, 40),
606 (60), 547 (40), 510 (50), 474 (70), 451 (75), 310 (50), 206
(100).
1
(CDCl3) d 7.87 (d, 4H, J = 8.8 Hz, H–P2), 7.18 (dd, 1H, J =
1.4, J = 8.0 Hz, H-11), 7.00 (d, 1H, J = 1.4 Hz, H-7), 6.98 (d,
4H, J = 8.8 Hz, H–P3), 6.92 (d, 1H, J = 8.0 Hz, H-10), 6.89
(d, 2H, J = 4.4 Hz, H-3), 6.01 (d, 2H, J = 4.4 Hz, H-2), 4.68
(s, 2H, OCH2), 4.32 (s, 4H, NCH2), 3.86 (s, 6H, PhOCH3), 3.80
(s, 9H, OCH3(N), OCH3(O)); 13C NMR (CDCl3) d 171.99 (s,
=
=
NCH2C O), 169.17 (s, OCH2C O), 161.05 (s, C–P4), 158.28
(s, C-1/4), 148.69 (s, C-8), 142.44 (s, C-1/4), 141.72 (s, C-9),
136.44 (s, C-5), 131.49(d, C–P2), 130.68 (d, C-3), 128.21 (s, C–
P1), 125.88 (d, C-11), 125.69 (s, C-6), 120.68 (d, C-7), 118.56 (d,
C-10), 116.99 (d, C-2), 114.19 (d, C–P3), 66.10 (t, CH2O), 55.69
(q, PhOCH3) 54.09 (t, CH2N), 52.70 (q, OCH3(O)), 52.43 (q,
OCH3(N)); MS (EI 70 eV) m/z 726 (M+, 25), 727 (M+, 100),
728 (M+, 40), 668 (30), 595 (70), 576 (80), 521 (50), 334 (60).
HRMS (EI+): calcd for C38H36BF2N3O9 (M+) 727.26272; found
727.26654.
R
Preparation of BODIPYsꢀ
General procedure. A dichloromethane solution of 1 eq. of
dipyrromethene was purged with argon. To the solution was
added 10 eq. of triethylamine and the solution stirred for 0.5 h,
then BF3 etherate was added and the reaction mixture was
stirred for 1 h. The reaction was quenched by addition of
1 M aqueous solution of sodium hydroxide. The layers were
separated and the water layer extracted with dichloromethane.
The combined organic layers were dried over MgSO4, the solvent
was evaporated and the residue chromatographed on silica. For
10, hexane–ethyl acetate 7/3, v/v, was used as eluent. For 11,
dichloromethane was used as eluent and gradually ethyl acetate
was added (up to 10% (v) EtOAc).
R
Hydrolysis of the BODIPYꢀ–APTRA ester derivatives
To investigate the Ca2+ binding properties of the new indicators
R
in aqueous solution, the water-insoluble BODIPYꢀ–APTRA
ester derivatives 10 and 11 were saponified to yield the corre-
sponding water-soluble carboxylate salts 12 and 13. A methanol
solution of the ester derivative 10 (or 11) was mixed with a very
concentrated Milli-Q water solution of 10 eq. of spectroscopic
grade CsOH·H2O. The reaction mixture was refluxed for 16 h
under argon. When TLC showed the disappearance of the
starting compound, the mixture was allowed to cool down to
rt. More Milli-Q water was added and the solution washed with
spectroscopic grade CHCl3 to extract any residual unreacted
starting compound. The separated water layer was evaporated
to dryness in a rotary evaporator. The residue was then used to
prepare stock solutions of the indicator for further fluorescence
measurements. Comparison of the absorption and fluorescence
emission spectra of the esters in methanol and the caesium salts
in water indicates that the fluorophore structure remains intact
for the compounds 10, 12 and 11, 13.
Trimethyl 4,4-difluoro-8-(3-hydroxy-4-aminophenyl-N,N,O-
triacetate)-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (10)
Orange–red needles, 30 mg (54%); mp 169 ◦C; recrystallized
1
three times from chloroform–cyclohexane mixture; H NMR
2 7 6 0
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 2 7 5 5 – 2 7 6 1