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Journal of Materials Chemistry B
Page 3 of 8
DOI: 10.1039/C7TB00726D
Journal Name
ARTICLE
The synthetic rout of L3 was similar to that of L1. L3 was red density of the reactive site of the alkenylꢀbridge, leading to easier for
1
the nucleophilic addition. The designed molecular structures of L1ꢀ
L4 were shown in Scheme 1, and the corresponding synthetic routes
were presented in Scheme S1. As best known, the trend of electronꢀ
withdrawing ability was indolium > benzoindolium > pyridine>
solid, 3.80 g. Yield: 86 %. Melting point: 215 – 218 °C. H NMR
(400 MHz, d6ꢀDMSO) δ 8.84 (d, J = 5.9 Hz, 2H), 8.46 (dd, J = 16.8,
12.6 Hz, 2H), 8.35 (d, J = 9.0 Hz, 1H), 8.26 (d, J = 8.1 Hz, 1H), 8.18
(d, J = 9.0 Hz, 1H), 8.13 (d, J = 6.0 Hz, 1H), 7.96 (d, J = 16.7 Hz,
1H), 7.85 (dd, J = 11.3, 4.1 Hz, 1H), 7.78 (t, J = 7.5 Hz, 1H), 4.40 – chinoline moiety. Hence, the indolium and benzoindolium were of
4.37 (s, 3H), 2.03 (s, 6H). 13C NMR (100 MHz, d6ꢀDMSO) δ 182.9, the acceptor “A”, while the pyridine and chinoline groups were of
151.2, 148.7, 141.8, 139.9, 139.4, 134.0, 131.5, 130.5, 129.0, 128.1,
127.0, 123.9, 123.3, 117.4, 114.1, 54.8, 36.2, 24.9. ESIꢀMS (m/z)
Calculated: 313.1699; Found: 313.1698. IR (KBr, cmꢀ1): 3414, 2996,
1616, 1595, 1550, 1465, 1417, 1386, 1350, 11319, 1236, 1213, 975,
806, 763, 669, 524. Anal. Calcd. for C22H21N2I: C, 60.01; H, 4.81;
N, 6.36. Found: C, 59.96; H, 4.77; N, 6.39.
the acceptor “A′”.
Crystal structure of L1 and L2
The single crystals of L1 and L2 suitable for Xꢀray diffraction
analysis were obtained by slow inꢀdiffusion from isopropanol to
ethanol at roomꢀtemperature for five days. Crystal data collection
and refinement parameters were summarized in Table S2 and S3.
The crystal structures of L1ꢀL2 were shown in Figure 1.
Synthesis of L4
The synthetic rout of L4 was similar to that of L1. Red solid, L4,
L1 belonged to orthorhombic system with Cmc21 space group,
while L2 crystalized in monoclinic system with P21/c space group.
With regard to L1, the pyridine and indoium moieties were almost in
a coplanar (Figure 1C directly displayed the planarity of L1, the
dihedral angle between P1 and P2 was < 2.0°). In contrary, the
introduction of chinoline ring would alter the planarity of the
molecule (L2 in Figure 1D), and the dihedral angle between P3
(chinoline moiety) and P4 (indolium moiety) was 7.12°, which might
lead to changes in optical properties. In addition, the main CꢀC/CꢀN
bond distance was located between normal CꢀC/CꢀN single bond and
C=C/C=N double bond length (especially C8ꢀN2, N2ꢀC11 in L1;
and C12ꢀN2, N2ꢀC15 in L2), indicating high πꢀelectron
delocalization within the molecules, which would be in favour of
their good nonlinear optical properties.
1
4.10 g. Yield: 84 %. Melting point: 222 – 225 °C. H NMR (400
MHz, d6ꢀDMSO) δ 9.17 (d, J = 4.5 Hz, 1H), 9.04 (d, J = 16.4 Hz,
1H), 8.49 (dd, J = 8.2, 3.5 Hz, 2H), 8.38 (d, J = 9.0 Hz, 1H), 8.33 –
8.15 (m, 4H), 8.08 – 7.74 (m, 5H), 4.43 (s, 3H), 2.10 (s, 6H). 13C
NMR (100 MHz, d6ꢀDMSO) δ 173.1, 150.0, 149.5, 146.7, 137.9,
134, 133.5, 132.6, 129.6, 129.5, 128.6, 126.5, 125.8, 125.6, 124.2,
118.7, 113.0, 52.9, 32.6, 27.7. ESIꢀMS (m/z) Calculated: 363.1856;
Found: 363.1852. IR (KBr, cmꢀ1): 3424, 3062, 2988, 1613, 1560,
1504, 1462, 1396, 1354, 1248, 1211, 955, 876, 815, 792, 756, 526.
Anal. Calcd. for C26H23N2I: C, 63.68; H, 4.73; N,5.71. Found: C,
63.72; H, 4.76; N, 5.67.
Results and Discussion
Design and synthesis
UVꢀvis absorption spectra
Indolium derivative, with AꢀπꢀD model, were considered as
The absorption spectra of indolium derivatives (L1ꢀL4) in
different solvents were shown in Figure S1, and the corresponding
spectroscopic data were listed in Table 1 and S4.
ꢀ
2ꢀ 1,4,9,14
good ratiometric fluorescence probes to detect HSO3 /SO3
.
ꢀ
2ꢀ
During this detecting process, HSO3 /SO3 were utilized as
nucleophilic reagents to attack the alkenylꢀbridge of the molecules.
Hence, the key point was the electron density of alkenylꢀbridge. The
“donor group” was replaced by pyridine and chinoline moieties as
acceptor groups, which could significantly decrease the electron
As shown in Figure 1, the UVꢀvis absorption spectra of L1ꢀL4
displayed two kinds of bands between 275 nm and 500 nm. The low
energy bands could be ascribed as the intramolecular charge transfer
(ICT) transition, while the high energy bands ranging from 290ꢀ300
nm could be assigned as πꢀπ* transition of the indolium moiety.36
Interestingly, all the low energy bands located at about 360 nm with
slight changes from L1 to L4, revealing that the terminal moiety had
little effect on absorption bands of these AꢀπꢀA′ typological
indolium derivatives. Meanwhile, the experimental data also
confirmed the affection of solvents. As shown in Figure S1, the
Figure 1. Crystal structures of compounds L1 (A) and L2 (B) with
thermal ellipsoids at 50% probability (H atoms and anions have been
omitted for clarity). The illustrative diagrams of planarity for L1 (C)
and L2 (D).
Figure 2. The UVꢀvis absorption spectra (A) and fluorescence
emission spectra (B) of L1ꢀL4 in tetrahydrofuran with concentration
10 ꢀM.
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