10.1002/chem.202001470
Chemistry - A European Journal
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25 °C): δ (ppm) 173.1, 153.4, 147.4, 141.7, 140.96, 138.9, 138.5, 137.8,
133.5, 129.6, 128.4, 128.4, 127.4, 123.9, 119.5, 118.9, 109.0, 23.6, 21.4.
11B NMR (128 MHz, CDCl3, 25 °C): δ (ppm) 74.3. ESI-MS, (positive ion
mode): calcd for C35H34BNO 495.2733 Da, observed 496.2810 [M+H]+.
142.4, 141.0, 140.6, 139.9, 131.7, 129.9, 129.6, 129.0, 128.2, 125.2,
122.4, 120.7, 119.4, 108.9, 23.2, 23.1, 21.4. 11B NMR (128 MHz, CDCl3,
1
25 °C): δ (ppm) 0.98 (t, JBF = 13.61 Hz, 11B of BF2), 63.2 (broad, 11B of
2
TAB).19F NMR (470 MHz, CDCl3, 25 °C): δ (ppm) -134.54 (dq, JFF
=
=
84.00 Hz, 1JFB = 12.00 Hz, 11.41 Hz), -135.23 (dq, 2JFF = 84.00 Hz, 1JFB
Synthesis of 3a: Compound 3a was synthesized following the same
procedure used for 1a. Quantities of the reactants/reagents used and the
charactersization data as follows : Borylaniline 3b (535mg, 1.45 mmol)
and β-hyroxynapthaldehyde (279 mg, 1.45 mmol). Appearance: Orange
color solid. Yield = 87%, 660 mg. 1H NMR (500 MHz, CDCl3, 25 °C): δ
(ppm) 15.55 (s, 1H), 9.26 (s, 1H), 8.06 (d, J = 8.5 Hz, 1H), 7.75 (d, J =
9.00 Hz, 1H), 7.66 (d, J = 8.00, 1H), 7.49 (t, J = 7.50 Hz, 1H), 7.30 (t, J =
7.25 Hz, 1H), 7.00 (d, J = 9.50 Hz, 1H), 6.95 (s, 2H), 6.76 (s, 4H), 2.28 (s,
6H), 2.08 (s, 6H), 2.01 (s, 6H), 2.00 (s, 6H).13C NMR (126 MHz, CDCl3,
25 °C): δ (ppm) 174.1, 152.1, 146.1, 144.0, 142.7, 140.9, 140.6, 139.6,
137.6, 133.7, 129.5, 128.9, 128.9, 128.3, 127.2, 123.8, 123.6, 119.0,
119.0, 108.6, 23.2, 23.0, 23.0, 21.4.11B NMR (128 MHz, CDCl3, 25 °C): δ
(ppm) 74.1 ppm. ESI-MS, (positive ion mode): calcd for C37H38BNO
523.3046 Da, observed 524.3125 [M+H]+.
12.00 Hz, 11.41 Hz). ESI-MS, (positive ion mode): calcd. for
C37H37B2F2NO 571.3029 Da, observed 594.2926 [M+Na]+.
For compound 3, the 19F resonance showed multiple splitting pattern with
significantly different chemical shift, which clearly suggests the
chemically and magnetically non-equivalent nature of the two fluorine
atoms (Figure S23). Each peak for the two fluorine atoms (-134.54 ppm
and -135.23 ppm) is splitted into doublet by coupling with the other
fluorine (I = ½) (2JFF = 84.00 Hz) followed by the splitting of each doublet
into quartet (1JBF = 12.00 Hz and 11.41 Hz) by coupling with quadruple
11B atom (I = 3/2). The presence of two methyl group in 3 makes the
molecule rigid and is the reason behind the magnetic nonequivalence of
fluorine atoms. This type multiple splitting is quite common for BODIPYs
where the molecular conformation is locked in some specific
conformation.[59]
Synthesis of 4a:[51] Compound 4a was also synthesized following the
same procedure used for 1a. Quantities of the reactants/reagents used
and the charactersization data as follows : aniline 4b (0.5 ml, 5.48 mmol)
and β-hyroxynapthaldehyde (943 mg, 5.48 mmol). Appearance: Yellow
color solid. Yield = 81%, 1.1 g.1H NMR (500 MHz, CDCl3, 25 °C): δ (ppm)
= 15.47 (s, 1H), 9.26 (s, 1H), 8.04 (d, J = 8.5 Hz, 1H), 7.75 (d, J = 9.00
Hz, 1H), 7.66 (d, J = 9.00, 1H), 7.48 (t, J = 7.50 Hz, 1H), 7.43 (t, J = 7.25
Hz, 2H), 7.28-7.34 (m, 4H), 7.04 (d, J = 9.00 Hz, 1H). 13C NMR (126 MHz,
CDCl3, 25 °C): δ (ppm) = 171.2, 154.4, 145.0, 137.0, 133.4, 129.8, 129.5,
128.2, 127.4, 126.6, 123.6, 122.6, 120.3, 118.9, 108.8. ESI-MS, (positive
ion mode): calcd for C17H13NO 247.0997 Da, observed 248.1076 [M+H]+.
Synthesis of 4: Compound 4 was also synthesized following the same
procedure described for 1. Quantities of the reactants/reagents used and
the characterization data as follows: Anil (4a) 400 mg (1.62 mmol),
BF3.OEt2 60µl (4.85 mmol) and DIPEA (90µl, 4.85 mmol). Appearance:
Green colour solid. Yield = 220 mg, 46%. 1H NMR (500 MHz, CDCl3,
25 °C): δ (ppm) = 9.12 (s, 1H), 8.12 (d, J = 9.00 Hz, 1H), 8.05 (d, J = 8.50
Hz, 1H), 7.85 (d, J = 8.00, 1H), 7.65 (t, J = 7.50 Hz, 1H), 7.61 (d, J = 8.00
Hz, 2H), 7.54 (t, J = 7.50 Hz, 2H), 7.48-7.51 (m, 2H). 13C NMR (126 MHz,
CDCl3, 25 °C): δ (ppm) = 162.8, 158.4, 143.0, 141.2, 131.6, 129.9, 129.8,
1297, 129.2, 128.2, 125.3, 123.8, 120.6, 1193, 108.8. 11B NMR (128 MHz,
1
CDCl3, 25 °C): δ (ppm) = 1.01 (t, JBF = 13.16 H), 19F NMR (470 MHz,
Synthesis of 1: To a pre-cooled (0 °C) dichloromethane (10 ml),
solution of anil 1a (100 mg, 0.2 mmol), DIPEA (100 µl, 0.60 mmol) and
BF3.OEt2 (70 µL, 0.60 mmol) were added successively. The resulting
reaction mixture was warmed to 25 °C and stirring was continued for
another 24 hours. The progress of the reaction was monitored by TLC,
after the completion of the reaction; the dichloromethane solution was
washed with a saturated aqueous sodium bicarbonate solution followed
by water (3 X 50 ml). The combined organic layer was dried over
anhydrous sodium sulphate and organic volatiles were removed under
reduced pressure gave crude product. The product was purified by
column chromatography over silica-gel with hexane: ethyl acetate (1:9)
mixture as eluent, to furnish the analytically pure compound as a
greenish solid. (Yield = 62 %, 68 mg). 1H NMR (500 MHz, CDCl3, 25 °C):
δ (ppm) 9.97 (s, 1H), 8.09 (d, J = 9.00 Hz, 1H), 7.96 (d, J = 8.00 Hz, 1H),
7.84 (d, J = 8.00, 1H), 7.62-7.64 (m, 2H), 7.47-7.53 (m, 3H), 7.28 (d, J =
9.50 Hz, 1H), 6.84 (s, 4H), 2.30 (s, 6H), 2.04 (s, 12H). 13C NMR (126
MHz, CDCl3, 25 °C): δ (ppm) 162.8, 158.4, 147.9, 143.1, 141.1, 141.1,
139.5, 136.9, 130.5, 129.9, 129.6, 129.5, 128.6, 128.2, 127.7, 125.2,
1
CDCl3, 25 °C): δ (ppm) = -134.55 (q, JFB = 14.12 Hz). ESI-MS, (positive
ion mode): calcd. for C17H12BF2NO 295.0980 Da, observed 318.0876
[M+Na]+.
Acknowledgements
P.T, P. S and N. K. K thank Science and Engineering Research
Board (SERB), New Delhi, India for financial support.and IISc
Bangalore for instrumental facilities. R.P.N. and P.S. thank IISc
Bangalore for research fellowship.
Keywords: Triarylborane • Anil • Boranil • Luminescence •
120.7, 119.2, 108.7, 23.7, 21.4.11B NMR (128 MHz, CDCl3, 25 °C): δ
Mechanofluorochromism
1
(ppm) 0.96 (t, JBF = 14.12 Hz, 11B of BF2), 63.0 (broad, 11B of TAB) .19
F
NMR (470 MHz, CDCl3, 25 °C): δ (ppm) -134.7 (q, 1JFB = 11.76 Hz). ESI-
MS, (positive ion mode): calcd for C35H33B2F2NO 543.2716 Da, observed
566.2616 [M+Na]+.
References
Synthesis of 2: Compound 2 was synthesized following the same
procedure described for 1. Quantities of the reactants/reagents are as
follows: Anil (2a) (100 mg, 0.20 mmol), BF3.OEt2 (70 µL,0.60 mmol) and
DIPEA (110µL, 0.60 mmol). Appearance: Orange color solid. Yield =
60%, 65 mg. 1H NMR (500 MHz, CDCl3, 25 °C): δ (ppm) 9.15 (s, 1H),
8.12 (d, J= 9.00 Hz, 1H), 8.08 (d, J = 8.00 Hz, 1H), 7.86 (d, J = 8.00, 1H),
7.64-7.67 (m, 3H), 7.57 (d, J = 8.00 Hz, 2H), 7.50-7.51 (m, 1H), 7.30 (d, J
= 9.00 Hz, 1H), 6.85 (s, 4H), 2.32 (s, 6H), 2.03 (s, 12H). 13C NMR (126
MHz, CDCl3, 25 °C): δ (ppm) 163.2, 158.2, 145.5, 141.6, 141.0, 137.7,
131.7, 130.0, 130.0, 128.5, 128.3, 125.4, 123.3, 120.7, 119.4, 109.0. 11B
NMR (128 MHz, CDCl3, 25 °C): δ (ppm) 1.03 (t, 1JBF = 12.84 Hz, , 11B of
BF2), 62.3 (broad, 11B of TAB). 19F NMR (470 MHz, CDCl3, 25 °C): δ
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BF3.OEt2 (60µl, 0.45 mmol) and DIPEA (80µl, 0.45 mmol). Appearance:
Green color solid. Yield = 80%, 70 mg. 1H NMR (500 MHz, CDCl3,
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7.65 (t, J = 7.00 Hz, 1H), 7.48 (t, J = 7.50 Hz, 1H), 7.30 (d, J = 9.00 Hz,
1H), 7.16 (s, 2H), 6.77 (s, 4H), 2.28 (s, 6H), 2.11 (s, 6H), 2.01 (s, 12H).
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8
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