W. Liao et al.
Dyes and Pigments 178 (2020) 108350
solution was slowly poured into 500 mL of ice water, and saturated
2.2.5. Synthesis of ditertbutyl 2-(2, 4-bis(diethylamino)benzylidene)malo-
NaHCO
neutral. The mixture was extracted with CH
organic layers were combined and washed with water (100 mL X 3). The
organic phase was dried over anhydrous MgSO . After stripped off the
volatile substances, the residue was purified by SiO column chroma-
3
aqueous solution was used to adjust the pH of the solution to
nate (CA-3)
2
Cl (100 mL X 4). The
2
It was synthesized following the method of CA-2 and purified by SiO
2
1
column chromatography. A yellow solid was obtained in 78.3% yield. H
–
4
NMR (400 MHz, CDCl
6.28 (m, 2H, Ar–H), 3.36 (q, J ¼ 7.1 Hz, 4H, -NCH
Hz, 4H, -NCH CH ), 1.52 (s, 9H, –C(CH
), 1.53 (s, 9H, –C(CH
(t, J ¼ 7.1 Hz, 6H, -NCH CH ), 1.04 (t, J ¼ 7.1 Hz, 6H, -NCH CH
NMR (101 MHz, CDCl
) δ 167.62 (-C
149.61, 139.72, 130.78, 122.48, 116.61, 105.74, 103.46, 81.22 (-C
(CH ), 80.07 (-C(CH ), 47.79 (-NCH CH ), 44.44 (-NCH CH ), 28.28
(-C(CH ), 28.01 (-C(CH ), 12.77 (-NCH CH ), 12.46 (-NCH CH ).
M/z (ESI) 447.3 ([MþH] , 100%).
3
) δ 7.92 (s, 1H, –C
–
CH-Ar), 7.40 (m, 1H, Ar–H),
CH
), 3.06 (q, J ¼ 7.1
), 1.17
2
2
3
tography using ethyl acetate and petroleum ether (1:10 V/V) as an
elution. The yellow liquid (7.42 g) was obtained with a yield of 74.8%.
2
3
3
)
3
3 3
)
1
3
2
3
2
3
).
–
–
O), 165.02 (-C O), 153.69,
C
1
–
–
–
H NMR (400 MHz, CDCl
H, Ar–H), 6.30 (dd, J ¼ 8.9, 2.3 Hz, 1H, Ar–H), 6.15 (d, J ¼ 2.4 Hz, 1H,
CH
3
) δ 10.00 (s, 1H, O
–
C–H), 7.66 (d, J ¼ 8.9 Hz,
3
1
Ar–H), 3.33 (q, J ¼ 7.1 Hz, 4H, -NCH
2
3
), 3.10 (q, J ¼ 7.1 Hz, 4H,
3
)
3
3
)
3
2
3
2
3
-
-
NCH
NCH
2
CH
3
), 1.13 (t, J ¼ 7.1 Hz, 6H, -NCH
2
CH ), 1.00 (t, J ¼ 7.1 Hz, 6H,
3
3
)
3
3
)
þ
3
2
3
2
3
1
3
–
–
O), 156.89
2
CH
3
). C NMR (101 MHz, CDCl
3
) δ 189.59 (-C
(ArC), 152.50 (ArC), 131.36 (ArC), 119.53 (ArC), 106.16 (ArC), 102.48
(ArC), 48.57 (-NCH CH ), 44.67 (-NCH CH ), 12.69 (-NCH CH ), 12.37
(-NCH CH ).
2
3
2
3
2
3
2.2.6. Synthesis of ditertbutyl 2-(4-(diphenylamino)benzylidene)malonate
2
3
(TA)
It was synthesized following the method of CA-2 and purified by SiO
2
1
2
.2.3. Synthesis of (E)-ethyl -3-(2, 4-bis(diethylamino)phenyl)acrylate
CA-1)
An oven-dried flask was charged under argon with 2, 4-bis(diethyla-
column chromatography. A yellow solid was obtained in 76.4% yield. H
–
(
NMR (400 MHz, CDCl
3
) δ 7.37 (s, 1H, –C CH-Ar), 7.28 (m, 2H, Ar–H),
–
7.20 (m, 4H, Ar–H), 7.02 (m, 6H, Ar–H), 6.88 (m, 2H, Ar–H), 1.46 (s,
1
3
mino) benzaldehyde (0.496 g, 2 mmol), NaH (0.24 g, 10 mmol) and 5
mL of THF. Then the dried ethyl acetate (0.176 g, 2 mmol) was slowly
9H, –C(CH
165.59 (-C
3
)
–
–
3
), 1.45 (s, 9H, –C(CH
3
)
3
). C NMR (101 MHz, CDCl
O), 148.63, 145.75, 138.44, 129.97,
),
), M/z (ESI) 472.2
3
) δ
–
–
O), 163.01 (-C
�
dropped into the flask with stirring. The solution was stirred at 0 C for 6
128.34, 124.85, 124.80, 124.45, 123.02, 120.03, 81.61 (-C(CH
81.05 (-C(CH ), 27.10 (-C(CH ), 26.91 (-C(CH
3 3
)
h. Ethyl acetate and petroleum ether (1:6 V/V) was added and the liquid
mixture was separated by centrifugation. The volatile substances were
stripped off under vacuum afterwards. The viscous mixture was purified
3
)
3
3
)
3
3 3
)
([MþH]þ, 100%).
by SiO
2
column chromatography using ethyl acetate and petroleum
2.3. Computation procedure
ether (1:6 V/V) as an elution. The yellow liquid (0.53 g) was obtained
1
with a yield of 83.3%. H NMR (400 MHz, CDCl
3
) δ 8.08 (d, J ¼ 16.1 Hz,
CH-Ar), 7.45 (d, J ¼ 8.8 Hz, 1H, Ar–H), 6.37 (dd, J ¼ 8.8, 2.5
Hz 1H, Ar–H), 6.30 (d, J ¼ 2.6 Hz, 1H, Ar–H), 6.19 (d, J ¼ 16.0 Hz, 1H,
Density function theory (DFT) calculation was performed on
Gaussian 09 program (Revision D09). The ground state (S ) geometries
–
–
1
H, –CH
0
were optimized with the Becke three-parameter exchange functional
along with the Lee Yang Parr correlation functional (B3LYP) using 6-
31G basis sets.
–
NCH
OCH
NCH
HC
–
CH-), 4.21 (q, J ¼ 7.2 Hz, 2H, -OCH
2
CH
CH
CH
3
), 3.37 (q, J ¼ 7.1 Hz, 4H,
-
-
-
2
CH
3
3
3
), 3.04 (q, J ¼ 7.1 Hz, 4H, -NCH
), 1.17 (t, J ¼ 7.1 Hz, 6H, -NCH
2
3
), 1.31 (t, J ¼ 7.2 Hz, 3H,
2
CH
2
3
), 1.04 (t, J ¼ 7.1 Hz, 6H,
1
3
–
–
2
CH
). C NMR (101 MHz, CDCl
3
) δ 168.60 (-C
O), 153.07,
2.4. Redox potential measurements
1
49.63, 142.97, 129.15, 117.99, 111.31, 106.74, 104.29, 59.81
-OCH CH ), 47.84 (-NCH CH ), 44.51 (-NCH CH ), 14.49 (-OCH CH ),
), 12.36 (-NCH CH
). M/z (ESI) 319.2 ([MþH] ,
(
2
3
2
3
2
3
2
3
þ
Electrochemical cyclic voltammetry was performed with a CHI 660
voltammetric analyzer with Pt disk, Pt plate, and Ag/Ag þ electrode as
working electrode, counter electrode, and reference electrode, respec-
1
2.76 (-NCH
00%).
2
CH
3
2
3
1
3
tively, in nitrogen-purged anhydrous CH CN with tetrabutylammonium
2
.2.4. Synthesis of diethyl 2-(2, 4-bis(diethylamino)benzylidene)malonate
hexafluorophosphate (TBAPF ) as the supporting electrolyte (scanning
6
(
CA-2)
An oven-dried flask equipped with a condenser was charged under
rate: 100 mV/s). The ferrocene/ferrocenium redox couple was used for
potential calibration. The concentration of investigated PIs were 4 ꢀ
À 4
argon with 2, 4-bis(diethylamino)benzaldehyde (0.496 g, 2 mmol),
diethyl malonate (0.32 g, 2 mmol) cyclohexylamine (0.20 g, 1 mmol),
acetic acid (0.12 g, 2 mmol) and 10 mL of toluene. The solution was
10 mol/L.
2.5. Electron paramagnetic resonance spin trapping (EPR-ST)
experiments
�
stirred at 100 C for 72 h. After the mixture was cooled down to room
temperature, the volatile substances were stripped off under vacuum.
Ethyl acetate and petroleum ether (1:10 V/V) was added and the liquid
mixture was separated by centrifugation. Then, the volatile substances
were stripped off under vacuum. The viscous mixture was purified by
EPR spin-trapping experiments were carried out using a Bruker X-
band A200. The radicals were produced at room temperature under
LED@405 nm irradiation and trapped by phenyl-N-tertbutylnitrone
(PBN). Tertbutyl benzene was used as a solvent. The concentration of
PBN, photoinitiators and N-methyldiethanolamine (MDEA) were 5 ꢀ
SiO
2
column chromatography using ethyl acetate and petroleum ether
(
1:10 V/V) as an elution. The red liquid (0.62 g) was obtained with a
1
–
À 2
À 3
À 2
yield of 79.5%. H NMR (400 MHz, CDCl
3
) δ 8.02 (s, 1H, –C
.23 (m, 1H, Ar–H), 6.26 (m, 2H, Ar–H), 4.23 (m, 4H, -OCH CH
q, J ¼ 7.1 Hz, 4H, -NCH CH ), 2.99 (q, J ¼ 7.0 Hz, 4H, -NCH CH
m, 6H, -OCH CH CH ), 1.00 (t, J ¼ 7.0
), 1.11 (t, J ¼ 7.0 Hz, 6H, -NCH
CH
) δ 167.62 (-C
O), 153.69, 149.61, 139.72, 130.78, 122.48, 116.61,
05.74, 103.46, 61.10 (-OCH CH ), 60.81 (-OCH CH ), 47.79
CH ), 44.44 (-NCH CH ), 14.31 (-OCH CH ), 14.06 (-OCH CH ),
), 12.46 (-NCH CH
). M/z (ESI) 391.3 ([MþH] ,
–
CH-Ar),
), 3.30
), 1.26
10 , 8 ꢀ 10 and 2.4 ꢀ 10 mol/L, respectively. The aN and a stand
H
7
2
3
for the hyperfine coupling constants in the PBN radical adducts for the
(
(
2
3
2
3
nitrogen and the hydrogen, respectively. The EPR spectra simulations
were carried out with the bimolecular EPR spectroscopy software. And
the sweep width was 150.00 G, sweep time was 30.72 s, time constant
was 163.84 ms, modulation frequency was 100.00 kHz, modulation
2
3
2
3
1
3
–
–
O),
Hz, 6H, -NCH
2
3
). C NMR (101 MHz, CDCl
3
–
–
1
1
65.02 (-C
4
2
3
2
3
amplitude was 1.00 G, receiver gain was 1.00 ꢀ 10 , microwave power
(
-NCH
2
3
2
3
2
3
2
3
þ
was 21.64 mW, and the number of X-scans was 3.
1
2.77 (-NCH
00%).
2
CH
3
2
3
1
2.6. Steady photolysis experiments
The photolysis of photoinitiators followed through the changes in the
absorption intensity at the wavelength of maximum absorption (λmax).
3