B.S. Arslan et al.
DyesandPigments164(2019)188–197
10.11 (s, 1H), 9.60 (d, J = 1.9 Hz, 1H), 9.41 (s, 1H), 9.13 (s, 1H), 8.34
(d, J = 8.5 Hz, 1H), 8.12 (dd, J = 8.5, 2.2 Hz, 1H), 8.05 (s, 4H), 7.60 (s,
1H), 4.23 (s, 3H), 4.15 (s, 3H), 4.05 (s, 3H). 13C NMR (75 MHz, CDCl3)
δ 192.25, 159.23, 154.89, 148.87, 147.66, 147.19, 146.86, 146.20,
140.81, 138.59, 135.54, 132.17, 130.59, 130.36, 129.45, 128.38,
125.71, 123.06, 119.90, 118.52, 103.41, 62.00, 61.72, 56.68. HRMS-
ESI(+) m/z: [M+H]+ calcd for C26H21N2O4+, 425.1501; found,
425.1501.
2.2.9. Synthesis of 2-cyano-3-(4-(9-(dimethylamino)dibenzo[b,h] [1,6]
naphthyridin-2-yl)phenyl)acrylic acid, 5c
Compound 5c was synthesized using the same procedure employed
for compound 5a, using compound 4c (0.178 g, 80% yield). Reddish
brown solid, Mp; 285–287 °C. 1H NMR (600 MHz, DMSO‑d6) δ 9.33 (s,
1H), 9.27 (s, 1H), 8.78 (s, 1H), 8.17 (s, 1H), 8.15–8.04 (m, 5H), 8.00 (d,
J = 7.6 Hz, 2H), 7.73 (d, J = 8.8 Hz, 1H), 7.02 (s, 1H), 3.06 (s, 6H).13
C
NMR (150 MHz, DMSO‑d6) δ 163.84, 155.29, 149.82, 148.52, 145.04,
144.91, 143.38, 142.95, 137.97, 134.31, 132.39, 131.09, 130.32,
130.09, 129.34, 128.40, 127.99, 125.81, 124.15, 121.38, 120.45,
118.58, 110.24, 103.91, 40.48. HRMS-ESI(+) m/z: [M+H]+ calcd for
C28H21N4O2+, 445.1665; found, 445.1666.
2.2.5. Synthesis of 4-(9-methoxydibenzo[b,h] [1,6]naphthyridin-2-yl)
benzaldehyde, 4b
Compound 4b was synthesized according to the same procedure
used for compound 4a, starting with compound 3b (0.259 g, 71%
yield). Yellow solid, Mp; 221–223 °C. 1H NMR (300 MHz, CDCl3) δ
10.12 (s, 1H), 9.56 (d, J = 2.1 Hz, 1H), 9.39 (s, 1H), 8.75 (s, 1H), 8.31
(d, J = 9.4 Hz, 1H), 8.27 (d, J = 8.4 Hz, 1H), 8.10 (dd, J = 8.5, 2.1 Hz,
1H), 8.06 (s, 4H), 7.63 (dd, J = 9.3, 2.8 Hz, 1H), 7.30 (d, J = 2.6 Hz,
1H), 4.02 (s, 3H). 13C NMR (75 MHz, CDCl3) δ 192.29, 158.19, 154.67,
147.46, 146.90, 146.03, 145.76, 138.95, 135.59, 135.39, 131.47,
130.64, 130.46, 129.26, 128.60, 128.44, 126.94, 126.03, 122.94,
120.26, 104.52, 55.98. HRMS-ESI(+) m/z: [M+H]+ calcd for
2.3. Instruments
1H and 13C NMR spectra of the compounds were recorded on
Agilent 600 MHz and Varian 300 MHz spectrometers. HRMS measure-
ments were performed on a Waters SYNAPT MS system. The absorption
spectra of the dyes and the sensitized films were measured using
Shimadzu UV 2600 spectrophotometer. The dye loading amount was
estimated by the absorbance of the dyes desorbed from the photoanode
24H17N2O2+, 365.1290; found, 365.1291.
using
a
0.1 M NaOH solution in EtOH/H2O (1/1, v/v).
C
Photoluminescence measurements were carried out with a Hitachi F-
7000 fluorescence spectrophotometer. All electrochemical studies for
the dyes were performed on a potentiostat/galvanostat (PARSTAT
2273, Princeton Applied Research). Cyclic voltammetry (CV) mea-
surements were recorded in ACN with TBABF4 (0.1 M) as electrolyte
and glassy carbon as working electrode, Pt disk as reference electrode,
Pt wire as counter electrode at a scan rate of 0.050 V s−1. The results
were calibrated using Fc/Fc+ as an external standard.
2.2.6. Synthesis of 4-(9-(dimethylamino)dibenzo[b,h] [1,6]naphthyridin-
2-yl)benzaldehyde, 4c
Compound 4c was synthesized using the same procedure employed
for compound 4a, using compound 3c (0.298 g, 79% yield). Orange-
brown solid, Mp; 206–208 °C. 1H NMR (300 MHz, CDCl3) δ 10.10 (s,
1H), 9.48 (d, J = 2.1 Hz, 1H), 9.29 (s, 1H), 8.53 (s, 1H), 8.26–8.18 (m,
2H), 8.09–7.97 (m, 5H), 7.64 (dd, J = 9.6, 2.8 Hz, 1H), 6.92 (d,
J = 2.7 Hz, 1H), 3.13 (s, 6H). 13C NMR (75 MHz, CDCl3) δ 192.29,
154.97, 148.50, 147.02, 145.62, 145.39, 144.46, 138.64, 135.49,
133.88, 130.58, 130.50, 130.31, 129.40, 128.58, 128.37, 126.35,
123.58, 122.65, 120.67, 103.87, 40.80. HRMS-ESI(+) m/z: [M+H]+
calcd for C25H20N3O+, 378.1606; found, 378.1610.
2.4. Fabrication and characterization of DSSCs
TiO2 film composed of two transparent layers was prepared using
the doctor-blade technique on a well-cleaned FTO substrate, as reported
earlier [36]. The active area of the TiO2 film was 0.196 cm2. Dye-sen-
sitized photoanodes were prepared by immersing the TiO2 films in
0.3 mM solution of dyes with or without 4 mM CDCA as the co-ad-
sorbent in EtOH/THF (1/1, v/v) at room temperature for 20 h. For
comparison, the TiO2 film was also immersed in a solution made of
0.5 mM N719 and 5 mM CDCA in EtOH for 6 h. The Pt counter electrode
was obtained by casting platinum paste solution on FTO substrate [37].
This Pt counter electrode was then assembled with the dye-sensitized
photoanode using the sealing film. Finally, the electrolyte was injected
between the photoanode and the counter electrode.
The photocurrent density-voltage (J–V) curves of the DSSCs were
recorded using the potentiostat/galvanostat under AM 1.5G illumina-
tion from a solar simulator (96000, Newport) calibrated with a silicon
detector (918D-SL-OD3, Newport). The active area was guaranteed by a
black mask during the measurements. To check the reproducibility of
the J–V curves, at least three devices were fabricated for each dye and a
compensating curve was utilized. The incident photon-to-current con-
version efficiency (IPCE) of the devices were measured with a mono-
chromator (74004, Oriel). The electrochemical impedance spectroscopy
(EIS) measurements of the DSSCs were performed using the same po-
tentiostat/galvanostat at a forward bias voltage of −0.60 V in the dark
between 0.1 and 105 Hz.
2.2.7. Synthesis of 2-cyano-3-(4-(8,9,10-trimethoxydibenzo[b,h] [1,6]
naphthyridin-2-yl)phenyl)acrylic acid, 5a
A solution of compound 4a (0.212 g, 0.5 mmol), cyanoacetic acid
(85 mg, 1 mmol) and piperidine (0.2 mL) in acetonitrile (20 mL) was
refluxed for 6 h. The mixture was cooled to room temperature and then
poured to 50 mL ice water. A precipitate formed was filtered through
sintered glass, washed with ethanol and dichloromethane to give 5a as
yellow solid (0.204 g, 83% yield), Mp; 220–222 °C. 1H NMR (600 MHz,
DMSO‑d6) δ 9.49 (s, 1H), 9.40 (s, 1H), 9.21 (s, 1H), 8.29–7.97 (m, 7H),
7.50 (s, 1H), 4.13 (s, 3H), 4.07 (s, 3H), 3.95 (s, 3H). 13C NMR
(150 MHz, DMSO‑d6)
δ 163.61, 159.23, 155.42, 149.70, 148.32,
146.99, 146.80, 145.95, 142.75, 140.80, 137.97, 132.60, 132.55,
131.11, 130.43, 129.39, 128.02, 125.22, 121.88, 119.42, 118.59,
118.35, 103.82, 62.25, 61.55, 56.98. HRMS-ESI(+) m/z: [M+H]+
calcd for C29H22N3O5+, 492.1559; found, 492.1559.
2.2.8. Synthesis
of
2-cyano-3-(4-(9-methoxydibenzo[b,h]
naphthyridin-2-yl)phenyl)acrylic acid, 5b
Compound 5b was synthesized according to the same procedure
used for compound 5a, starting with compound 4b (0.183 g, 85%
yield). Yellow solid, Mp; 257–260 °C. 1H NMR (600 MHz, DMSO‑d6) δ
9.53 (s, 1H), 9.46 (s, 1H), 9.17 (s, 1H), 8.37 (s, 1H), 8.30 (d, J = 9.2 Hz,
1H), 8.26 (d, J = 8.4 Hz, 1H), 8.21 (d, J = 8.4 Hz, 3H), 8.12 (d,
2.5. Computational details
J = 7.5 Hz, 2H), 7.70 (d, J = 9.2 Hz, 1H), 7.65 (s, 1H), 3.99 (s, 3H). 13
C
Quantum chemical calculations were carried out by using Q-CHEM
4.3 and the output files were visualized via IQmol program [38,39].
The optimized molecular structures of 5a−c in the ground states were
obtained at the B3LYP/6-31G(d,p) [40] level of density functional
theory (DFT). Afterwards, the UV–vis absorption wavelengths, oscil-
lator strengths of 5a−c in gas phase were calculated by using the same
NMR (150 MHz, DMSO‑d6) δ 163.68, 157.90, 155.49, 146.80, 145.63,
145.22, 144.01, 138.14, 136.65, 131.87, 131.61, 131.16, 130.61,
129.37, 128.76, 128.27, 127.08, 125.56, 121.91, 120.17, 117.02,
105.83, 56.25. HRMS-ESI(+) m/z: [M+H]+ calcd for C27H18N3O3
,
+
432.1348; found, 432.1349.
190