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BULLETIN OF THE
ISSN (Print) 0253-2964 | (Online) 1229-5949
KOREAN CHEMICAL SOCIETY
1
used to prepare fluorescent dye 1. Yield: 64.3%; H NMR
(500 MHZ, DMSO‑d6) 0.90 (m, 6H, CH3), 1.31 (m, 4H,
CH2), 1.56 (t, 4H, CH2), 3.14 (t, 4H, CH2), 6.59 (m, 4H,
ArH), 7.34 (m, 4H, ArH), 7.79 (t, 2H, ArH), 8.19 (d, 4H,
ArH), 8.35 (s, 2H, ArH), 8.36 (s, 1H, NH), 8.41 (d, 2H,
ArH); LC–MS 719(M − 1); elemental analysis found
C:80.07, H:5.12, N:5.81O:8.84 calculated for C48H37N2O4
C:80.09, H:5.18, N:5.84, O:8.89.
The absorption maxima of fluorescent dyes 1–4 were
observed in the range 315–346 nm so the fluorescent color by
these dyes will be in the blue region, as shown in Table 1. In
particular, the absorption maxima of fluorescent dyes 2 and
4 were bathochromically shifted relative to those of analogue
dyes 1 and 3. The absorption maximum of fluorescent dye
2 exhibited a bathochromic shift of 6 nm compared with that
of dye 1, which could be caused by increased π-conjugation
(Figure 1). The bigger shift was observed for dye 4 in compari-
son to analogue 3, where the introduction of a further electron-
withdrawing group in the form of a naphthalimidyl moiety cau-
sed a red shift of 19 nm. In terms of the Stokes shift, it was
found that the dyes substituted with two acetylene linkage
groups tended to shift more, thus dye 4 exerted the greatest
shift. The quantum yields ranged from 0.61 to 0.78, with
higher fluorescent efficiency with more extended π-conjugation
by an acetylene group (Figure 1).
As shown in Figure 2 and Table 2, for fluorescent dyes
1–2, the electrons of the HOMO and LUMO levels are
delocalized, whereas in the case of dyes 3–4, the electrons
are localized at the HOMO and LUMO levels, respectively.
Fluorescent dyes 1–2 feature higher energy levels and can
more readily donate electrons, leading to an increase in their
HOMO energy levels. As a result, fluorescent dyes 1 and
2 have higher HOMO energy levels (−4.77 to −4.57 eV)
than analogue dyes 3 and 4 (−5.88 to −5.83 eV). In con-
trast, for dyes 3 and 4, in which an acetylene group is linked
Scheme 3. Reagents and conditions18: (a) KI, KIO3, AcOH,
10 ꢀC, 5 h; (b) KI, KIO3, AcOH, 80 ꢀC, 5 h.
acetate layer was rinsed with excess water. The obtained
organic layer was dried using MgSO4Áanhydrous as a dry-
ing agent and then evaporated to obtain the reaction prod-
uct. The obtained reaction product was purified via column
chromatography (absorbent: silica gel, eluent: ethyl acetate/
n-hexane 1:5). Yield: 75.5%; 1H NMR (500 MHZ,
DMSO‑d6) 0.90 (m, 3H, CH3), 1.31 (m, 2H, CH2), 1.74
(m, 2H, CH2), 4.16 (m, 2H, CH2), 6.59 (m, 2H, ArH), 6.81
(t, 1H, ArH), 7.20 (m, 2H, ArH), 7.28 (m, 3H, ArH), 7.34
(m, 2H, ArH), 7.42 (m, 2H, ArH), 7.59 (d, 2H, ArH), 7.75
(s, 1H, ArH), 8.17 (s, 1H, ArH), 8.36 (d, 1H, NH); GC–
MS 414(M+1); elemental analysis found C:86.88, H:6.27,
N:6.71 calculated for C36H26N2 C:86.92, H:6.32, N:6.76.
Synthesis of Fluorescent Dye 2. Fluorescent dye 2 was
synthesized using intermediate D2 (11.87 mmol, 5 g) and
intermediate C4 (33.88 mmol, 8.36 g) via the method used
to prepare fluorescent dye 1. Yield: 68.7%; 1H NMR
(500 MHZ, DMSO‑d6) 0.90 (m, 6H, CH3), 1.31 (m, 4H,
CH2), 1.74 (m, 4H, CH2), 4.16 (m, 4H, CH2), 6.59 (m, 4H,
ArH), 7.34 (m, 8H, ArH), 7.56 (m, 4H, ArH), 7.78 (m, 4H,
ArH), 8.36 (d, 2H, ArH), 8.36 (s, 1H, NH); GC–MS 659
(M + 1); elemental analysis found C:87.35, H:6.23, N:6.33
calculated for C48H41N3 C:87.37, H:6.26, N:6.37.
Synthesis of Fluorescent Dye 3. Fluorescent dye 3 was
synthesized using intermediate D1 (16.94 mmol, 5 g) and
intermediate N4 (16.94 mmol, 4.69 g) via the procedure
Table 1. Photochemical properties of fluorescent dyes 1–4.
Fluorescent
dye
Stokes
shift (nm)
1
used to prepare fluorescent dye 1. Yield: 79.1%; H NMR
a,b
em*
λmax
*
λmax
εmax
фa
(500 MHZ, DMSO‑d6) 0.90 (m, 3H, CH3), 1.31 (m, 2H,
CH2), 1.56 (m, 2H, CH2), 3.14 (t, 2H, CH2), 6.59 (d, 2H,
ArH), 6.81 (t, 1H, ArH), 7.20 (m, 2H, ArH), 7.28 (d, 2H,
ArH), 7.34 (d, 2H, ArH), 7.79 (t, 1H, ArH), 8.14 (s, 1H,
ArH), 8.19 (s, 1H, ArH), 8.36 (d, 1H, NH), 8.41 (m, 2H,
ArH); LC–MS 444(M − 1); elemental analysis found
C:81.05, H:5.43, N:5.43, O:7.16 calculated for
C30H24N2O2 C:81.06, H:5.44, N:6.30, O:7.20.
1
2
3
4
340
406
66
82
88
94
31 000
33 000
32 000
34 000
0.61
0.71
0.64
0.78
346
315
328
428
403
422
a Reference: Anthracene.
b Determined in methylene chloride.
Synthesis of Fluorescent Dye 4. Fluorescent dye 4 was
synthesized using intermediate D2 (11.87 mmol, 5 g) and
intermediate N4 (23.74 mmol, 6.58 g) via the procedure
Scheme 4. Reagents and conditions: (a) Pd(PPh3)2Cl2, Pd(II),
CuI, TEA, under nitrogen, reflux, 2 h.
Figure 1. Fluorescence emissions of fluorescent dyes 1–4 in meth-
ylene chloride (10 ppm) under UV light (λmax = 365 nm).
Bull. Korean Chem. Soc. 2019
© 2019 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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