Synthesis and photophysical properties of fluorescent dyes based on triphenylamine, diphenylamine, diphenyl sulfone or triphenyltriazine derivatives containing an acetylene linkage group

Article abstract of DOI:10.1016/j.dyepig.2020.108617

In this study, ten fluorescent dyes were prepared based on three different kinds of central moiety, such as triphenylamine, diphenylsulfone or triphenyltriazine, which was coupled to either carbazole or naphthalimidinyl group via an acetylene linkage group. N-n-Butyl-carbazole, N-phenyl-carbazole or N-n-butyl-naphthalimide was coupled to the individual central moiety of triphenylamine, diphenyl sulfone, 2,4,6-triphenyl-1,3,5-trazine or diphenylamine using a Sonogashira coupling reaction in the final step. All dyes were confirmed their chemical structure by ¹H NMR, GC-Mass and elemental analyses. The absorption properties and thermal stabilities of the fluorescent dyes were examined. Density Functional Theory (DFT) and Time-Dependent DFT calculations were carried out, in addition to geometry simulation, by using the Gaussian 09 program. In terms of fluorescence properties in this series, two dyes based on diphenyl sulfonyl and three dyes based on triphenylamine substituted by 1–3 of N-n-butyl-carbazole exhibited a blue emission, whereas three dyes based on triphenylamine substituted by 1–3 of N-n-butyl-naphthalimide were observed by a red emitter which can be attributable to both effects the bathochromic shifts in absorption maxima and larger Stokes shifts. In case of corresponding 2,4,6-triphenyl-1,3,5-trazine central moiety coupled to a carbazole ring, a green fluorescence was emitted. Results revealed that the fluorescence of the dyes is affected by the electron-donating strength of the acetylene linkages involved in the π-conjugation systems of the dyes.

Full text of DOI:10.1016/j.dyepig.2020.108617

Journal Pre-proof
Synthesis and photophysical properties of fluorescent dyes based on triphenylamine,
diphenylamine, diphenyl sulfone or triphenyltriazine derivatives containing an
acetylene linkage group
Kyung-Won Kim, Su-Hyeon Kwon, Byung-Jun Lee, Sung-Ok Ahn, Ju-Hong Lee, Jae-
Hong Choi
PII:
S0143-7208(20)31160-8
DOI:
https://doi.org/10.1016/j.dyepig.2020.108617
DYPI 108617
Reference:
To appear in: Dyes and Pigments
Received Date: 1 May 2020
Revised Date: 31 May 2020
Accepted Date: 1 June 2020
Please cite this article as: Kim K-W, Kwon S-H, Lee B-J, Ahn S-O, Lee J-H, Choi J-H, Synthesis and
photophysical properties of fluorescent dyes based on triphenylamine, diphenylamine, diphenyl sulfone
or triphenyltriazine derivatives containing an acetylene linkage group, Dyes and Pigments (2020), doi:
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Synthesis and photophysical properties of fluorescent dyes based on
triphenylamine, diphenylamine, diphenyl sulfone or triphenyltriazine
derivatives containing an acetylene linkage group
Kyung-Won Kima, Su-Hyeon Kwonb, Byung-Jun Leeb, Sung-Ok Ahnb, Ju-Hong Leeb, Jae-Hong Choib,*
a Advanced Organic Materials Science and Engineering, Kyungpook National University, Daegu 41566, Korea.
b Department of Textile System Engineering, Kyungpook National University, Daegu 41566, Korea.
*jaehong@knu.ac.kr
Keywords : acetylene linkage; carbazole; naphthalimide; triphenylamine; fluorescent dye
Abstract
In this study, ten fluorescent dyes were prepared based on three different kinds of central moiety, such as
triphenylamine, diphenylsulfone or triphenyltriazine, which was coupled to either carbazole or naphthalimidinyl
group via an acetylene linkage group. N-n-Butyl-carbazole, N-phenyl-carbazole or N-n-butyl-naphthalimide was
coupled to the individual central moiety of triphenylamine, diphenyl sulfone, 2,4,6-triphenyl-1,3,5-trazine or
diphenylamine using a Sonogashira coupling reaction in the final step. All dyes were confirmed their chemical
1
structure by H NMR, GC-Mass and elemental analyses. The absorption properties and thermal stabilities of the
fluorescent dyes were examined. Density Functional Theory (DFT) and Time-Dependent DFT calculations were
carried out, in addition to geometry simulation, by using the Gaussian 09 program. In terms of fluorescence
properties in this series, two dyes based on diphenyl sulfonyl and three dyes based on triphenylamine substituted
by 1~3 of N-n-butyl-carbazole exhibited a blue emission, whereas three dyes based on triphenylamine
substituted by 1~3 of N-n-butyl-naphthalimide were observed by a red emitter which can be attributable to both
effects the bathochromic shifts in absorption maxima and larger Stokes shifts. In case of corresponding 2,4,6-
triphenyl-1,3,5-trazine central moiety coupled to a carbazole ring, a green fluorescence was emitted. Results
revealed that the fluorescence of the dyes is affected by the electron-donating strength of the acetylene linkages
involved in the π-conjugation systems of the dyes.
1. Introduction
Some fluorescent dyes based on 1,8-naphthalimide derivatives containing an ethynyl linkage group or an
acetylene analogous for blue or red light emission [1-3]. One of interesting uses for these fluorescent dyes can
be applied to improve agricultural productivity when dyes supply the efficient blue or red light which is
contained in the PE film for a green house. Hence, light conversion films have been developed and have
attracted attention. Light conversion films do not use artificial external energy; these films integrate wavelength
favorable for photosynthesis with sunlight, and these films increase the efficiency of photosynthesis. Compared

to artificial LED lights, the light conversion films are advantageous due to that additional equipment and energy
are not required leading to lower cost and improved agricultural productivities [4-11]. Recently, a naphthalimde-
coumarin conjugate based dye was reported that contained an acetylene group between naphthalimide and
coumarin moieties to provide a blue emission of 433 nm with a quantum yield of 0.78, however the thermal
stabilities for this dye was not discussed [12]. As a similar series of 1,8-naphthalimide based dyes connected by
an imine linkage group with N-ethylcarbazole or some other moieties were also prepared to evaluate their
thermal and luminescent properties. Among these dyes, N-ethylcarbazole based analogue exhibited a green
emission of 501 nm in CHCl3 which was shifted 161 nm from its absorption maximum of 340 nm. In addition
the temperature of 5% weight loss by DSC analysis was observed at 363 °C [13]. In case of N-phenylcarbazole
substituted by a thiophene moiety, a blue fluorescence of 442 nm was observed [14].
Naphthalimide-based fluorescent dyes have been studied as one of the blue emitting chromophores
featuring their acceptable durability as well as good light fastness, where comparatively larger Stokes shifts can
afford a blue emission from maximum absorption in the range of 300 to 390 nm. As another kind of fluorescent
dyes, triphenylamine based ones, which exhibits excellent purity and luminous efficiency as well as excellent
thermal stability and photophysical properties, have been also studied. The acetylene linkage was often used by
a linkage group of fluorescent dye molecules due to its high quantum yield and comparatively good thermal
stabilities [15-23].
However, there have been very limited literatures reporting red fluorescent emissions by naphthalimide or
triphenylamine based dyes, it is required to study the possibility to prepare dyes featuring extended emission
maximum upto red light ranges.
In this study, ten fluorescent dyes were prepared by varing three different kinds of central moiety, such as
triphenylamine, diphenylsulfone or triphenyltriazine, which was coupled to either carbazole or naphthalimidinyl
group via an acetylene linkage group, so that the effects of a central moiety and substituted ring system via an
acetylene linkage onto the absorption maxima, Stokes shift and resultant quantum yields were investigated.
2. Experimental
2.1. Materials and instrumentation
1,8-Naphthalic anhydride (Sigma Aldrich), carbazole (Sigma Aldrich), triphenylamine (Sigma Aldrich),
chlorosulfonic acid (TCI Chemical) and triflic acid (TCI Chemical) were used as the starting materials for
synthesizing fluorescent dyes with an acetylene linkage. Based on the dye star synthesis scheme, bromine
(Junsei Chemical), KI (Ducksan), KIO3 (Sigma Aldrich), n-butylamine (TCI Chemical), 1-bromobutane (TCI
Chemical), 2-methyl-3-butyn-2-ol (Sigma Aldrich), bromobenzene (TCI Chemical) and 4-
Bromobenzonitrile(TCI Chemical) were used. Cuprous iodide (Sigma Aldrich), triphenylphosphine (AlfaAesar),
and bis(triphenylphosphine)palladium( )dichloride (Sigma Aldrich) were used as the catalyst for Sonogashira

coupling, and triethylamine (TCI Chemical) was used as the base. Other reagents included chloroform (TCI
Cheminal), dimethylformamide (DMF, Sigma Aldrich), acetic acid (Ducksan), tetrahydrofuran (Ducksan),
toluene (Ducksan), methanol (Samchun Chemicals), ethanol (Samchun Chemicals), methylene chloride (TCI
Chemical), ammonia water (Ducksan), n-hexane (Samchun), ethyl. All of the above reagents are first-grade
reagents, which are the directors of acetate (Samchun Chemicals), methylene chloride (Samchun Chemicals),
and potassium hydroxide (Ducksan).
High-performance liquid chromatography (HPLC, Acme 9000, Young-Lin, Korea) was employed to
analyze the purity of the fluorescent dyes and the intermediates; mass spectra were recorded on a gas
chromatography–mass spectrometry (GC–MS; 7890/A-5975C GC/MSD, Agilent, USA) system; 1HNMR
spectra (Advance Digit 500, Bruker, Germany) were recorded in DMSO-d6 or CDCl3; elemental analysis was
carried out on a Flash 200 system (Thermo Fisher, Italy); optical analysis was carried out on a tandem mass
spectrometer (LC–MS, Agilent, USA); UV–Visible spectrophotometry was carried out by dissolving samples in
5.0×10−5mol/L of methylene chloride(Thermo Scientific, Evolution 300); and fluorescence spectra were
recorded on a fluorescence spectrophotometer (Scinco, Fluoro Mate FS-2) with the samples dissolved in 5.0 ×
10−5 mol/L of methylene chloride. PMT voltage was measured by the fluorescence intensity at 500, and quantum
yields were calculated using anthracene (Φ=0.36) and rhodamine B (Φ = 0.49 in ethanol) as references for blue
and red fluorescence, respectively. Thermal stability was measured at 30 °C/min from 30 °C to 500 °C under
nitrogen using a Q600 thermal analysis system (TA Instruments, Japan).
2.2. Dye syntheses
2.2.1. Synthesis of Triphenylamine-based dye intermediates T1-T3 : Iodination
X1
Potassium Iodide, Potassium Iodate
N
N
Acetic acid
X3
T1
X2
- X1 : I, X2 : H, X3 : H
Triphenylamine
T2 - X1 : I, X2 : I, X3 : H
T3 - X1 : I, X2 : I, X3 : I
Scheme 1. Synthesis of the triphenylamine derived dye intermediates T1-T3.
2.2.1.1. Synthesis of 4-iodo-N,N-diphenylaniline (T1) :Iodination
Potassium iodide (22.2 mmol, 3.68 g) and triphenylamine (33.3 mmol, 8.16 g) were added to acetic acid (100
mL), followed by stirring the mixture at 85 °C for 5 hrs then followed by stirring the mixture for 5 hrs, the

temperature was lowered to room temperature. In the next stage, potassium iodate (16.7 mmol, 3.57 g) was
slowly added, the temperature was increased to 85 °C, and the reaction was allowed to continue for 5 hrs. When
the reaction was completed, the mixture was cooled to room temperature, and water was added. The formed
crystals were filtered under reduced pressure, affording crystals. These crystals were recrystallized using
methylene chloride, affording the final product in 62.5 % yield. 1H NMR (400MHz, DMSO-d6): 6.95(d, J = 8.6
Hz, 2H, ArH), 7.00(d, J = 8.2 Hz, 4H, ArH), 7.08(d, J = 7.8 Hz, 2H, ArH), 7.24(d, J = 8.6 Hz, 4H, ArH), 7.50(d,
J = 8.2 Hz, 2H, ArH); HRMS (m/z, MALDI): [M + H]+ calculated for C18H14IN: 371.2129; found 371.2132;
Elemental analyses, found C, 58.31; H, 3.79; I, 34.14; N, 3.76; ‘C18H14IN’ requires C, 58.24; H, 3.77; I, 34.21;
N, 3.77.
2.2.1.2. Synthesis of 4-iodo-N-(4-iodophenyl)-N-phenylaniline (T2) : Iodination
Potassium iodate (56 mmol, 12 g), potassium iodide (80 mmol, 13.5 g), and triphenylamine (60 mmol, 15g)
were added to acetic acid (340 mL), followed by stirring the mixture at 80 °C for 1hrs. Secondly, after stirring
the mixture for 1 hr, water (30 mL) was added, and the mixture was stirred at 80 °C for 6 hrs. The generated
crystals were filtered under reduced pressure, affording crystals. Thesecrystals were recrystallized using methyl
chloride, affording the final product in 51.9 % yield. 1H NMR (400MHz, DMSO-d6): 6.95(d, J = 8.6 Hz, 4H, ArH),
7.00(d, J = 8.2 Hz, 2H, ArH), 7.08(d, J = 7.8 Hz, 1H, ArH), 7.24(d, J = 8.6 Hz, 2H, ArH), 7.50(d, J = 8.2 Hz, 4H, ArH);
HRMS (m/z, MALDI): [M + H]+ calculated for C18H13I2N: 497.1095; found 497.1038; Elemental analyses, found
C, 43.41; H, 2.59; I, 51.04; N, 2.80; ‘C18H13I2N’ requires C, 43.48; H, 2.62; I, 51.09; N, 2.82.
2.2.1.3. Synthesis of tris(4-iodophenyl)amine (T3) : Iodination
Potassium iodide (88 mmol, 14.72 g) and triphenylamine (40 mmol, 9.8 g) were added to acetic acid (300 mL),
followed by stirring the mixture at 110 °C for 1 hr. Secondly, after stirring the mixture for 1 hr, the temperature
was lowered to 80 °C. After slowly adding potassium iodate (44 mmol, 7.3 g), the solution was heated to 110 °C,
and the reaction was allowed to continue for 6 hrs. When the reaction was completed, the solution was cooled to
room temperature, and water was added. The generated crystals were filtered under reduced pressure, affording
crystals. These crystals were recrystallized using methyl chloride, affording the final product in 62.5 % yield. 1H
NMR (400MHz, DMSO-d6): 6.95(d, J = 8.6 Hz, 6H, ArH), 7.50(d, J = 8.2 Hz, 6H, ArH); HRMS (m/z, MALDI): [M +
H]+ calculated for C18H12I3N: 623.0061; found 623.0090; Elemental analyses, found C, 34.62; H, 1.89; I, 61.07; N,
2.18; ‘C18H12I3N’ requires C, 34.69; H, 1.93; I, 61.14; N, 2.25.
2.2.2. Synthesis of 4,4'-sulfonylbis(bromobenzene) (S1):
O
Cl S OH
O
O
S
Br
Br
Br
Chloroform
O
Bromobenzene
Chlorosulfonic acid
S1
Scheme 2. Synthesis of the diphenyl sulfone derived dye intermediates S1.

Chlorosulfonic acid (10 mmol, 1.1 g) was added to Chloroform (25 ml), followed by stirring the mixture with
ice-bath at -15°C for 30 min. After slowly adding bromobenzene (20 mmol, 3.1 g), the solution was heated to
50 °C for 2 hr. When the reaction was completed, the solution was cooled to room temperature, and ice water
was added. The generated crystals were filtered under reduced pressure, affording crystals. These crystals were
recrystallized using methyl chloride, affording the final product in 68.7 % yield. 1H NMR (500MHz,DMSO-d)7.72(d,
6
J = 8.1 Hz, 4H, ArH), 7.77(d, J = 8.1 Hz, 4H, ArH); HRMS (m/z, MALDI): [M + H]+ calculated for
C12H8Br2O2S: 376.0618; found 376.0636; Elemental analyses, found C, 38.30; H, 2.11; Br, 42.46; O, 8.47; S,
8.49; calculated for C12H8Br2O2S C, 38.33; H, 2.14; Br, 42.49; O, 8.51; S, 8.53.
2.2.3. 2,4,6-Tris(4-bromophenyl)-1,3,5-triazine(A1) :Trimerization
Triflic acid
CN
N
N
N
Br
4-Bromobenzonitrile
Br
Br
A1
Scheme 3. Synthesis of the triazine derived dye intermediates A1.
Trifilic acid (6 mL) was stirred under 0 °C for 30 mins and 4-Bromobenzonitrile (10 mmol, 2 g) was slowly
added to the solution. The solution was stirred under 0 °C for 2hrs. After stirring, the solution was stirred under
room temperature for 20hrs. Water (50 mL) was added to the solution after stirring was completed, and sodium
hydroxide was used to neutralize. After rinsing with methylene chloride (500 mL) and water (500 mL), the
obtained organic layer was washed with MgSO4 to remove water, followed by evaporation to obtain the reactant.
1
The obtained reaction product was recrystallized using toluene, affording the final product in 90.9% yield. H
NMR (500MHz, DMSO-d6) 7.67(m, 12H, ArH), HRMS (m/z, MALDI): [M + H]+ calculated for C21H12Br3N3:
546.0504; found 546.0519; Elemental analyses, found C, 46.20; H, 2.20; Br, 43.87; N, 7.68 calculated for
C21H12Br3N3 C, 46.19; H, 2.22; Br, 43.90; N, 7.70.
2.2.4. Synthesis of carbazole-based dye intermediates C1-C7

C4H9
N
H
N
H
N
1-bromobutane
Potassium Iodide, Potassium Iodate
Acetic acid
Sodium hydride, DMF
I
I
C1
Carbazole
C2
C4H9
N
C4H9
N
CuI, PPh3, Pd(PPh3)Cl2
2-methyl-3-butyn-2-ol
Potassium hydroxide
Toluene
TEA, THF, N2
C4
C3
OH
Scheme 4. Synthesis of the carbazole derived dye intermediates C1-C4 [1].
H
N
N
bromobenzene
Sodium hydride, DMF
I
I
C1
C5
N
N
CuI, PPh3, Pd(PPh3)Cl2
2-methyl-3-butyn-2-ol
Potassium hydroxide
Toluene
TEA, THF, N2
C7
C6
OH
Scheme 5. Synthesis of the carbazole derived dye intermediates C5-C7.
2.2.4.1. Synthesis of 3-iodo-9H-carbazole(C1) :Iodination [1]
Potassium iodide (22.2 mmol, 3.68 g) and 9H-carbazole (33.3 mmol, 5.57 g) were added into acetic acid (100
mL), followed by stirring at 110 °C for 1hrs. Second, after stirring the mixture for 1 hr, the temperature was
lowered to 80 °C. Finally, potassium iodate (16.7 mmol, 3.57 g) was slowly added, the temperature was
increased to 100 °C, and the reaction was allowed to continue for 10 min. When the reaction was completed, the
solution was cooled to room temperature, and water was added. The formed crystals were filtered under reduced
pressure to obtain crystals. These crystals were recrystallized using methyl chloride, affording the final product
in 72.7 % yield. 1H NMR (400MHz, DMSO-d6): 7.20(d, J = 8.3 Hz, 1H, ArH), 7.35(d, J = 8.0 Hz, 1H, ArH), 7.46(d, J =
8.1 Hz, 1H, ArH), 7.50(d, J = 1.8 Hz, 1H, ArH), 7.63(d, J = 8.1 Hz, 1H, ArH), 7.93(s, 1H, ArH),8.19(s, 1H,ArH),11.66(s,
1H, NH); HRMS (m/z, MALDI): [M + H]+ calculated for C12H8IN: 293.1019; found 293.1051; Elemental analyses,

found C, 49.15; H, 2.69; I, 43.23; N, 4.71; ‘C12H8IN’ requires C, 49.17; H, 2.75; I, 43.30; N, 4.78.
2.2.4.2. Synthesis of 9-butyl-3-iodo-9H-carbazole(C2) :Alkylation [1]
First, 60 % of NaH (4.25 mmol, 0.17 g) and intermediate C1 (2.9 mmol, 0.85 g) were stirred at 80 °C for 1 h in
DMF (5 mL). Second, after the solution was stirred for 1 hr, 1-bromobutane (4.35 mmol, 0.59 g) was added.
When the reaction was completed, the solution was poured into warm water. The formed crystals were filtered
under reduced pressure to obtain crystals. These crystals were recrystallized using ethanol, affording the final
product in 89.7 % yield. 1H NMR (400MHz, DMSO-d6): 0.89(t, J = 6.5 Hz, 3H, CH3), 1.26(m, 2H, CH2), 1.74(m, 2H, CH2),
4.16(t, J = 7.4 Hz, 2H, CH2), 7.35(m, 1H, ArH), 7.46(d, J = 8.0 Hz, 2H, ArH), 7.54(m, 1H, ArH), 7.64(s, 1H, ArH), 7.93(s,
1H, ArH), 8.17(s, 1H, ArH); HRMS (m/z, MALDI): [M + H]+ calculated for C16H16IN: 349.2071; found 349.2066;
Elemental analyses, found C, 55.01; H, 4.57; I, 36.24; N, 4.07; ‘C16H16IN’ requires C, 55.03; H, 4.62; I, 36.34; N,
4.01.
2.2.4.3. Synthesis of 4-(9-butyl-9H-carbazol-3-yl)-2-methylbut-3-yn-2-ol (C3) :Sonogashira coupling [1]
Anhydrous tetrahydrofuran (10 mL) was added to a solution of intermediate C2 (1 mmol, 349 mg), cuprous
iodide (0.05 mmol, 15.9 mg), triphenylphosphine (0.05 mmol, 13.1 mg), and bis(triphenylphosphine)
palladium(II) dichloride (0.1 mmol, 115 mg), and the solution was stirred under nitrogen for 15 min. Secondly,
after the addition of trimethylamine (10 mL) and stirring for 15 min, 2-methyl-3-butyn-2ol (3 mmol, 252 mg)
was added, and the solution was stirred for 30 min, followed by reflux for 1hrs. The solution was cooled after
the reaction was completed. Next, the solution was added into ammonia water, and ethyl acetate was used to
separate the layers, followed by rinsing with water. The obtained organic layer was washed with MgSO4 to
remove water, followed by evaporation to obtain the reactant. The obtained reaction product was purified by
column chromatography (absorbent: silica gel, eluent: ethyl acetate/n-hexane), affording the final product in
65.1 % yield. 1H NMR (400MHz, DMSO-d6): 0.89(t, J = 6.5 Hz, 3H, CH3), 1.26(m, 2H, CH2), 1.46(s, 6H, 2хCH3), 1.74(m,
2H, CH2), 4.16(t, J = 7.4 Hz, 2H, CH2), 5.40(s, 1H, OH), 7.24(d, J = 8.0 Hz, 1H, ArH), 7.42(d, J = 8.2 Hz, 2H, ArH),
7.55(m, 2H, ArH), 7.71(s, 1H, ArH), 8.17(d, J = 1.9 Hz, 1H, ArH); HRMS (m/z, MALDI): [M + H]+ calculated for
C21H23NO: 305.4098; found 305.4056; Elemental analyses, found C, 82.15; H, 7.51; N, 4.47; O, 5.19; ‘C21H23NO’
requires C, 82.25; H, 7.59; N, 4.59; O, 5.24.
2.2.4.4. Synthesis of 9-butyl-3-ethynyl-9H-carbazole(C4) : Hydrolysis [1]
Intermediate C3 (1 mmol, 305 mg) and KOH (3 mmol, 168 mg) were charged with anhydrous toluene and
refluxed under nitrogen for 3 hrs, and after the reaction was completed, the solution was cooled. The reaction
product was filtered under reduced pressure to remove KOH and impurities, followed by evaporation. Finally,
the obtained reaction product was purified by flash column chromatography (absorbent: silica gel, eluent: ethyl
acetate/n-hexane), affording the final product in 76.4 % yield. 1H NMR (400MHz, CDCl3): 0.89(t, J = 6.5 Hz, 3H,
CH3), 1.26(m, 2H, CH2), 1.74(m, 2H, CH2), 3.15(s, 1H, CH), 4.16(t, J = 7.4 Hz, 2H, CH2), 7.24(d, J = 8.0 Hz, 1H, ArH),
7.33(d, J = 8.2 Hz, 2H, ArH), 7.55(m, 2H, ArH), 7.71(s, 1H, ArH), 8.17(d, J = 1.9 Hz, 1H, ArH); HRMS (m/z, MALDI):

[M + H]+ calculated for C18H17N: 247.3319; found 247.3353; Elemental analyses, found C, 87.38; H, 6.91; N, 5.56;
‘C18H17N’ requires C, 87.41; H, 6.93; N, 5.66.
2.2.4.5. Synthesis of 3-iodo-9-phenyl-9H-carbazole (C5) : Phenylation
C5 was synthesized using intermediate C1 (2.9 mmol, 0.85 g) based on the C2 synthetic method using
Bromobenzene(12.5mmol, 0.72g) instead of 1-bromobutane, affording the final product in 65.1 % yield.1H NMR
(500MHz, DMSO-d6) 7.25(t, J = 8.4 Hz, 2H, ArH), 7.40(m, 3H, ArH), 7.50(d, J = 8.2 Hz, 2H, ArH), 7.58(t, J =
8.2 Hz, 2H, ArH), 7.94(d, J = 8.2 Hz, 2H, ArH), 8.55(d, J = 1.8 Hz, 1H, ArH); HRMS (m/z, MALDI): [M + H]+
calculated for C18H12IN: 369.1973; found 369.1990; Elemental analyses Found C:58.55, H:3.24, I:34.32, N:3.74
calculated for C18H12IN C:58.56, H:3.28, I:34.37 N:3.79.
2.2.4.6. Synthesis of 2-methyl-4-(9-phenyl-9H-carbazol-3-yl)but-3-yn-2-ol (C6) :Sonogashiracoupling
C6 was synthesized using intermediate C5 (1.5 mmol, 0.5g) based on the C3 synthetic method, affording the
final product in 62.8 % yield. 1H NMR (500MHz, DMSO-d6) 1.46(s, 6H, CH3), 5.45(s, 1H, OH), 7.24(m, 3H,
ArH), 7.45(m, 3H, ArH), 7.60(d, J = 8.1 Hz, 3H, ArH), 7.71(s, 1H, ArH), 7.94(s, 1H, ArH), 8.55(d, J = 1.9 Hz,
1H, ArH); HRMS (m/z, MALDI): [M + H]+ calculated for C23H19NO: 325.4000; found 325.4011; Elemental
analyses, found C:84.82, H:5.86, N:4.27, O:4.90 calculated for C23H19NO C:84.89, H:5.89, N:4.30, O:4.92.
2.2.4.7. Synthesis of 3-ethynyl-9-phenyl-9H-carbazole (C7) : Hydrolysis
C7 was synthesized using intermediate C6 (3 mmol, 1.0g) based on the C4 synthetic method, affording the final
product in 67.1 % yield. 1H NMR (500MHz, DMSO-d6) 4.05(s, 1H, CH), 7.24(m, 3H, ArH), 7.45(m, 3H, ArH),
7.60(d, J = 8.1 Hz, 3H, ArH), 7.71(s, 1H, ArH), 7.94(s, 1H, ArH), 8.55(d, J = 1.9 Hz, 1H, ArH); HRMS (m/z,
MALDI): [M + H]+ calculated for C20H13N: 267.3221; found 267.3235; Elemental analyses, found C:89.82,
H:4.85, N:5.21 calculated for C20H13N C:89.86, H:4.90, N:5.24.
2.2.5. Synthesis of naphthalimidyl dye intermediates N1-N4 [1]

C4H9
N
O
O
O
O
O
O
O
O
Aminolysis
Bromination
Br
Br
1,8-Naphthalimide
N1
N2
C4H9
N
C4H9
O
O
O
N
O
Sonogashira coupling
Hydrolysis
N3
OH
N4
Scheme 6. Synthesis of the naphthalimidyl dye intermediates N1-N4.
2.2.5.1. Synthesis of 3-Bromo-1,8-naphthalic anhydride (N1) : Bromination [1]
Silver(I) sulfate (5 mmol, 1.56 g) and 1,8-naphthalic anhydride (10 mmol, 1.98 g) were added to sulfuric acid
(40 mL), and the solution was stirred. Second, after the slow addition of bromine (13 mmol, 6.3 mL), the
solution was heated to 60 °C and reacted for 12 hrs. When the reaction was complete, the solution was cooled to
room temperature, and water was added. The formed crystals were filtered under reduced pressure to obtain
crystals. These crystals were recrystallized using ethanol, affording the final product in 56.7 % yield. 1H NMR
(400MHz, DMSO-d6): 7.39(d, J = 8.2 Hz, 1H, ArH), 7.74(d, J = 7.8 Hz, 1H, ArH), 8.17(s, 1H, ArH), 8.56(d, J = 8.2 Hz,
1H, ArH), 8.58(s, 1H, ArH); HRMS (m/z, MALDI): [M + H]+ calculated for C12H5BrO3: 277.0684; found 277.0670;
Elemental analyses, found C, 52.01; H, 1.79; O, 17.38; ‘C12H5BrO3’ requires C, 52.02; H, 1.82; O, 17.32.
2.2.5.2. Synthesis of 5-Bromo-2-butyl-1H-Benzo [de] isoquinoline-1,3(2H)-dione (N2) : Aminolysis [1]
Intermediate N1 (5 mmol, 1.66 g) and n-butylamine (7.5 mmol, 0.74 mL) were added into ethanol (15 mL), and
the solution was maintained at reflux conditions for 1 hr. The reaction mixture was cooled after the reaction was
completed. Once the solution was completely cooled, the crystals produced were filtered under reduced pressure
to obtain crystals. The reaction product was recrystallized using ethanol, affording the final product in 74.2 %
yield. 1H NMR (400MHz, DMSO-d6): 0.90(t, J = 6.5 Hz, 3H, CH3), 1.30(m, 2H, CH2), 1.54(m, 2H, CH2), 3.13(t, J = 7.7
Hz, 2H, CH2), 7.85(d, J = 7.8 Hz, 1H, ArH), 8.11(d, J = 8.2 Hz, 1H, ArH), 8.40(s, 1H, ArH), 8.50(d,J = 1.9 Hz, 2H, ArH);
HRMS (m/z, MALDI): [M + H]+ calculated for C16H14BrNO2: 332.1891; found 332.1899;Elemental analyses, found
C, 57.81; H, 4.21; N, 4.15; O, 9.59; ‘C16H14BrNO2’ requires C, 57.85; H, 4.25; N, 4.22; O, 9.63.
2.2.5.3. Synthesis of Butyl-5-(3-hydroxy-3-methylbut-1-ynyl)1H-benzo [de] isoquinoline-1,3(2H)-dione (N3):
Sonogashira coupling [1]
Anhydrous tetrahydrofuran (10 mL) was added to a solution of intermediate N2 (1 mmol, 349 mg), cuprous

iodide (0.05 mmol, 15.9 mg), triphenylphosphine (0.05 mmol, 13.1 mg), and bis(triphenylphosphine)
palladium(II) dichloride, and the solution was stirred under nitrogen for 15 min. In the next step, after the
addition of triethylamine (10 mL) and stirring for 15 min, 2-methyl-3-butyn-2ol (3 mmol, 252 mg) was added,
and the solution was stirred for 30 min, followed by reflux for 1 hr. After the reaction was completed, it was
cooled. Next, the solution was added into ammonia water, and ethyl acetate was added to separate the layers,
followed by rinsing with water. The obtained organic layer was washed with MgSO4 to remove water and then
evaporated to obtain a reactant. The obtained reaction product was purified by column chromatography
1
(absorbent: silica gel, eluent: ethyl acetate/n-hexane), affording the final product in 75.8 % yield. H NMR
(400MHz, DMSO-d6): 0.90(t, J =6.5 Hz, 3H, CH3), 1.30(m, 2H, CH2), 1.46(s, 6H, 2хCH3), 1.54(m, 2H, CH2), 3.13(t, J = 7.7
Hz, 2H, CH2), 5.40(s, 1H, OH), 7.90(d, J = 8.0 Hz, 1H, ArH), 8.11(d, J = 8.2 Hz, 1H, ArH), 8.28(d, J = 8.0 Hz, 1H, ArH),
8.45(d, J = 1.8 Hz, 2H, ArH); HRMS (m/z, MALDI): [M + H]+ calculated for C21H21NO3: 335.3922; found
335.3920; Elemental analyses, found C, 75.15; H, 6.34; N, 4.17; O, 14.29; ‘C21H21NO3’ requires C, 75.22; H, 6.27;
N, 4.18; O, 14.33.
2.2.5.4. Synthesis of 2-Butyl-5-ethynyl-1H-benzo [de] isoquinoline-1,3(2H)-dione (N4) : Hydrolysis [1]
Intermediate N3 (1 mmol, 305 mg) and KOH (3 mmol, 168 mg) were charged to anhydrous toluene and
refluxed under nitrogen for 3 hrs. Second, after the reaction was completed, the solution was cooled. Next, the
reaction product was filtered under reduced pressure to remove KOH and impurities, followed by evaporation.
The obtained reaction product was purified by flash column chromatography (absorbent: silica gel, eluent: ethyl
acetate/n-hexane), affording the final product in 76.4 % yield. 1H NMR (400MHz, CDCl3): 0.90(t, J = 6.5 Hz, 3H,
CH3), 1.30(m, 2H, CH2), 1.54(m, 2H, CH2), 3.13(t, J = 7.7 Hz, 2H, CH2), 4.08(s, 1H, CH), 7.90(d, J = 8.0 Hz, 1H, ArH),
8.11(d, J = 8.2 Hz, 1H, ArH), 8.28(s, 1H, ArH), 8.45(d, J = 1.8 Hz, 2H, ArH); HRMS (m/z, MALDI): [M + H]+
calculated for C18H15NO2: 277.3143; found 277.3141; Elemental analyses, found C, 77.68; H, 5.51; N, 4.96; O,
11.79; ‘C18H15NO2’ requires C, 77.98; H, 5.42; N, 5.05; O, 11.55.
2.2.6. Synthesis of fluorescent dyes 1-6

n-C4H9
N
X1
R1
N
C4
Sonogashira coupling
or
+
N
n-C4H9
X2
X3
R2
R3
O
N
O
Fluorescent dye 1 : R1=C4, R2=H, R3=H
Fluorescent dye 2 : R1=C4, R2=C4, R3=H
Fluorescent dye 3 : R1=C4, R2=C4, R3=C4
Fluorescent dye 4 : R1=N4, R2=H, R3=H
Fluorescent dye 5 : R1=N4, R2=N4, R3=H
Fluorescent dye 6 : R1=N4, R2=N4, R3=N4
T1 : X1=I, X2=H, X3=H
T2 : X1=I, X2=I, X3=H
T3
: X1=I, X2=I, X3=I
N4
Scheme 7. Synthetic routes of fluorescent dyes 1–6.
2.2.6.1. Synthesis of fluorescent dye 1 : Sonogashira coupling
First, anhydrous tetrahydrofuran (10 mL) was added to a solution of intermediate C4 (1 mmol, 349 mg),
cuprous iodide (0.05 mmol, 15.9 mg), triphenylphosphine (0.05 mmol, 13.1 mg), and bis(triphenylphosphine)
palladium(II) dichloride, and the solution was stirred under nitrogen for 15 min. Secondly, triethylamine (10 mL)
was added, and the solution was stirred for 15 min, followed by the addition of intermediate T1 (1.1 mmol, 305
mg) and stirring for 30 min. Finally, the solution was refluxed for 1 hr. After the reaction was completed, the
solution was cooled. Next, the solution was added into ammonia water, and ethyl acetate was used to separate
the layers, followed by rinsing with water. The obtained organic layer was washed with MgSO4 to remove water
and then evaporated to obtain a reactant. The obtained reaction product was purified by column chromatography
1
(absorbent: silica gel, eluent: ethyl acetate/n-hexane), affording the final product in 73.5 % yield. H NMR
(400MHz, DMSO-d6): 0.89(t, J = 6.5 Hz, 3H, CH3), 1.26(m, 2H, CH2), 1.74(m, 2H, CH2), 4.16(t, J = 7.5 Hz, 2H, CH2),
7.08(m, 6H, ArH), 7.14(m, 2H, ArH), 7.24(m, 9H, ArH), 7.64(m, 3H, ArH), 8.17(d, J = 8.2 Hz, 1H, ArH); 13C NMR (75
MHz, DMSO-d6, δ, ppm) 147.72, 146.12, 140.65, 140.30, 132.98, 132.95, 129.25, 127.69, 126.44, 124.72,
124.44, 123.39, 122.93, 122.64, 120.74, 120.45, 119.42, 109.37, 108.98, 107.87, 90.45, 86.65, 43.31, 20.07,
13.85; HRMS (m/z, MALDI): [M + H]+ calculated for C36H30N2: 490.6326; found 490.6318; Elemental analyses,
found C, 88.11; H, 6.12; N, 5.68; ‘C36H30N2’ requires C, 88.13; H, 6.16; N, 5.71.
2.2.6.2. Synthesis of fluorescent dye 2 : Sonogashira coupling
Fluorescent dye 2 was synthesized using intermediate C4 (1 mmol, 330 mg) and intermediate T2 (2.2 mmol,
610 mg) based on the above method, affording the final product in 68.5 % yield. 1H NMR (400 MHz, DMSO-d6):
0.89(t, J = 6.5 Hz, 6H, 2хCH3), 1.26(m, 4H, 2хCH2), 1.74(m, 4H, 2хCH2), 4.16(t, J = 7.5 Hz, 4H, 2хCH2), 7.08(d, J = 7.8
Hz, 6H, ArH), 7.14(m, 1H, ArH), 7.51(m, 16H, ArH),7.75(m, 3H,ArH), 8.17(d, J = 8.2 Hz, 1H, ArH);13C NMR (75 MHz,

DMSO-d6, δ, ppm) 147.72, 146.12, 140.65, 140.30, 132.98, 132.95, 129.25, 127.69, 126.44, 124.72, 124.44,
123.39, 122.93, 122.64, 120.74, 120.45, 119.42, 109.37, 108.98, 107.87, 90.45, 86.65, 43.31, 31.01, 20.07,
13.85; HRMS (m/z, MALDI): [M + H]+ calculated for C54H45N3: 735.9489; found 735.9483; Elemental analyses,
found C, 88.13; H, 6.13; N, 5.69; ‘C54H45N3’ requires C, 88.16; H, 6.12; N, 5.71.
2.2.6.3. Synthesis of fluorescent dye 3 : Sonogashira coupling
Fluorescent dye 3 was synthesized using intermediate C4 (1 mmol, 330 mg) and intermediate T3 (3.3 mmol,
915 mg) based on the above method, affording the final product in 53.1 % yield. 1H NMR (400 MHz, DMSO-d6):
0.89(t, J = 6.5 Hz, 9H, 3хCH3), 1.26(m, 6H, 3хCH2), 1.74(m, 6H, 3хCH2), 4.16(t, J = 7.5 Hz, 6H, 3хCH2), 7.14(d, J = 8.3
Hz, 6H, ArH), 7.51(m, 19H, ArH), 7.75(m, 5H, ArH), 8.17(d, J = 8.2 Hz, 3H, ArH); 13C NMR (75 MHz, DMSO-d6, δ,
ppm) 146.12, 140.65, 140.30, 132.98, 132.95, 127.69, 123.39, 122.93, 122.64, 120.74, 120.45, 119.42, 109.37,
108.98, 107.87, 90.45, 86.65, 43.31, 31.01, 20.07, 13.85; HRMS (m/z, MALDI): [M + H]+ calculated for
C72H60N4: 981.2652; found 981.2665; Elemental analyses, found C, 88.07; H, 6.14; N, 5.65; ‘C72H60N4’ requires C,
88.07; H, 6.12; N, 5.71.
2.2.6.4. Synthesis of fluorescent dye 4 : Sonogashira coupling
Anhydrous tetrahydrofuran (10 mL) was added to a solution of intermediate N4 (1 mmol, 349 mg), cuprous
iodide (0.05 mmol, 15.9 mg), triphenylphosphine (0.05 mmol, 13.1 mg), and bis(triphenylphosphine)
palladium(II) dichloride, and the solution was stirred under nitrogen for 15 min. Second, after triethylamine (10
mL) was added, and the solution was stirred for 15 min, intermediate T1 (1.1 mmol, 305 mg) was added, and
the solution was stirred for 30 min, followed by reflux for 1hr. After the reaction was completed, the solution
was cooled. Next, the cooled solution was added into ammonia water, and ethyl acetate was used to separate the
layers, followed by rinsing with water. The obtained organic layer was washed with MgSO4 to remove water,
followed by evaporation to obtain a reactant. The obtained reaction product was purified by column
chromatography (absorbent: silica gel, eluent: ethyl acetate/n-hexane, affording the final product in 63.7 % yield.
1H NMR (400 MHz, DMSO-d6): 0.90(t, J = 6.6 Hz, 3H, CH3), 1.30(m, 2H, CH2), 1.54(m, 2H, CH2), 3.13(t, J = 11 Hz, 2H,
CH2), 7.08(d, J = 8.3 Hz, 6H, ArH), 7.14(d, J = 8.0 Hz, 2H, ArH), 7.51(d, J = 7.3 Hz, 6H, ArH), 7.89 (d, J = 7.5 Hz,
1H, ArH), 8.11(d, J = 8.3 Hz, 1H, ArH), 8.28(s, 1H, ArH), 8.42(d,J = 2.0 Hz, 2H, ArH); 13C NMR (75 MHz, DMSO-d6,
δ, ppm) 147.72, 146.12, 138.85, 133.95, 132.95, 130.38, 129.25, 128.37, 125.50, 124.72, 124.44, 124.22, 122.93,
121.56, 107.87, 91.05, 90.45, 55.19, 53.68, 29.73, 20.07, 13.85; HRMS (m/z, MALDI): [M + H]+ calculated for
C36H28N2O2: 520.6150; found 520.6153; Elemental analyses, found C, 83.01; H, 5.42; N, 5.49; O, 6.12; ‘C36H28N2O2’
requires C, 83.05; H, 5.52; N, 5.42; O, 6.15.
2.2.6.5. Synthesis of fluorescent dye 5 : Sonogashira coupling
Fluorescent dye 5 was synthesized using intermediate N4 (1 mmol, 330 mg) and intermediate T2 (2.2 mmol,
610 mg) based on the above method, affording the final product in 65.7 % yield. 1H NMR (400 MHz, DMSO-d6):
0.90(t, J = 6.6 Hz, 6H, 2хCH3), 1.30(m, 4H, 2хCH2), 1.54(m, 4H, 2хCH2), 3.13(t, J = 11 Hz, 4H, 2хCH2), 7.08(d, J = 8.3
Hz, 6H, ArH), 7.14(d, J = 8.0 Hz, 1H, ArH), 7.51(d, J = 7.3 Hz, 6H, ArH), 7.90(d, J = 7.5 Hz, 2H, ArH), 8.11(d, J = 8.3

Hz, 2H, ArH), 8.28(s, 4H, ArH), 8.45(d, J = 2.0 Hz, 2H, ArH); 13C NMR (75 MHz, DMSO-d6, δ, ppm) 147.72,
146.12, 138.85, 133.95, 132.95, 130.38, 129.25, 128.37, 127.69, 125.50, 124.72, 124.44, 124.22, 122.93, 121.56,
107.87, 91.05, 90.45, 55.19, 53.68, 29.73, 20.07, 13.85; HRMS (m/z, MALDI): [M + H]+ calculated for
C54H41N3O4: 795.9137; found 795.9134; Elemental analyses, found C, 81.46; H, 5.14; N, 5.12; O, 8.02; ‘C54H41N3O4’
requires C, 81.49; H, 5.19; N, 5.28; O, 8.04.
2.2.6.6. Synthesis of fluorescent dye 6 : Sonogashira coupling
Fluorescent dye 6 was synthesized using intermediate N4 (1 mmol, 330 mg) and intermediate T3 (2.2 mmol,
610 mg) based on the above method, affording the final product in 51.2 % yield. 1H NMR (400 MHz, DMSO-d6):
0.90(t, J = 6.6 Hz, 9H, 3хCH3), 1.30(m, 6H, 3хCH2), 1.54(m, 6H, 3хCH2), 3.13(t, J = 11 Hz, 6H, 3хCH2), 7.08(d, J = 8.3
Hz, 6H, ArH), 7.51(d, J = 8.0 Hz, 6H, ArH), 7.90(d, J = 7.5 Hz, 3H, ArH), 8.11(d, J = 8.3 Hz, 3H,ArH),8.28(s,6H,ArH),
8.45(d, J = 2.0 Hz, 3H, ArH); 13C NMR (75 MHz, DMSO-d6, δ, ppm) 146.12, 138.85, 133.95, 132.95, 130.38,
128.37, 127.69, 125.5, 124.22, 122.93, 121.56, 107.87, 91.05, 90.45, 55.19, 53.68, 29.73, 20.07, 13.85; HRMS
(m/z, MALDI): [M + H]+ calculated for C72H54N4O6: 1071.2124; found 1071.2168; Elemental analyses, found C,
80.28; H, 5.02; N, 5.17; O, 8.26; ‘C72H54N4O6’ requires C, 80.37; H, 5.08; N, 5.23; O, 8.29.
2.2.7. Synthesis of fluorescent dyes 7-8
n-C4H9
N
C4
O
S
O
S
CuI, PPh3, Pd(PPh3)Cl2
2-methyl-3-butyn-2-ol
or
R4
R5
Br
Br
+
O
O
TEA, THF, N2
Fluorescent dye 7 : R4=C4, R5=C4
Fluorescent dye 8 : R4=C7, R5=C7
S1
N
C7
Scheme 8. Synthetic routes of fluorescent dyes 7–8.
2.2.7.1. Synthesis of blue fluorescent dye 7
Fluorescent dye 7 was synthesized using intermediate C4 (16mmol, 3.9g) and intermediate S1 (8mmol, 3.0g)
based on the above method, affording the final product in 75.8 % yield. 1H NMR (500MHz,DMSO-d) 0.9(t,J = 6.5
6
Hz, 6H,CH3),1.31(m, 4H,CH2),1.74(m,4H,CH2),4.16(t, J = 6.4 Hz, 4H,CH2),7.32(m,4H,ArH),7.47(t,J = 6.6 Hz, 2H,ArH),

7.54(t, J = 8.4 Hz, 2H,ArH),7.65(t,J = 8.5 Hz, 2H,ArH),7.76(d,J = 7.3 Hz, 11H,ArH),8.36(d,J = 8.4 Hz, 1H,ArH);13C
NMR (75 MHz, DMSO-d6, δ, ppm) 143.89, 140.70, 140.65, 140.30, 132.98, 132.97, 131.10, 131.04, 129.23,
128.35, 127.69, 126.73, 126.44, 124.65, 123.396, 122.64, 121.00, 120.74, 120.45, 119.42, 117.29, 109.37,
108.98, 90.45, 86.65, 58.06, 49.56, 43.31, 34.74, 31.01, 30.12, 20.07, 13.85; HRMS (m/z, MALDI): [M + H]+
calculated for C H NOS:708.9020; found 708.9036;Elemental analyses, found C, 81.29; H, 5.65; N, 3.94; O,
48 40
2 2
4.49; S, 4.49 calculatedforC H NOSC, 81.32; H, 5.69; N, 3.95; O, 4.51; S, 4.52.
48 40
2 2
2.2.7.2. Synthesis of blue fluorescent dye 8
Fluorescent dye 8 was synthesized using intermediate C7 (16mmol, 4.2g) and intermediate S1 (8mmol, 3.0g)
based on the above method, affording the final product in 68.3 % yield. 1H NMR (500MHz,DMSO-d)7.72(m, 5H, ArH),
6
7.45(t, J = 7.9 Hz, 2H, ArH),7.63(m, 11H,ArH),7.75(s, 2H,ArH),7.79(d, J = 7.9 Hz, 8H,ArH),7.94(d,J = 7.5 Hz, 2H, ArH),,
8.55(d, J = 6.2 Hz, 2H, ArH); 13C NMR (75 MHz, DMSO-d6, δ, ppm) 141.38, 140.70, 140.62, 137.60, 132.98,
132.97, 129.25, 128.35, 127.69, 127.10, 126.44, 124.72, 123.39, 123.23, 121.00, 120.74, 120.45, 119.42, 109.95,
109.37, 90.45, 86.65; HRMS (m/z, MALDI): [M + H]+ calculated for C52H32N2O2S: 748.8824; found 748.8801;
Elemental analyses, found C, 83.36; H, 4.27; N, 3.73; O, 4.24; S, 4.25 calculatedforC52H32N2O2S C, 83.40; H, 4.31;
N, 3.74; O, 4.27; S, 4.28.
2.2.8. Synthesis of Fluorescent dyes 9-10
n-C4H9
N
R6
Br
C4
CuI, PPh3, Pd(PPh3)Cl2
2-methyl-3-butyn-2-ol
or
+
N
N
N
N
TEA, THF, N2
N
N
R7
R8
Br
Br
N
Fluorescent dye 9
Fluorescent dye 10
: R6=C4, R7=C4, R8=C4
: R6=C7, R7=C7, R8=C7
A1
C7
Scheme 9. Synthetic routes of fluorescent dyes 9–10.
2.2.8.1. Synthesis of green fluorescent dye 9
A1 (1 mmol, 1.4 g) was added to a solution of triethylamine (30 mL) and toluene (30 mL), and the solution was

stirred under nitrogen for 30 min. Secondly, after the addition of copper iodide (0.04 mmol, 0.02 g),
triphenylphosphine (0.02 mmol, 0.014 g) and bis(triphenylphosphine) palladium(II) dichloride (0.08 mmol, 0.15
g), and the solution was stirred under nitrogen at 50 °C for 1hrs. After the stirring was completed, intermediate
C4 (3.6 mmol, 2.3 g) was slowly added and followed by reflux for 10 hrs. The solution was filtered under
reduced pressure after the reaction was completed. Next, the solution was added into ammonia water and ethyl
acetate was used to separate the layers, followed by rinsing with water. The obtained organic layer was washed
with MgSO4 to remove water, followed by evaporation to obtain the reactant. Finally, the obtained reaction
1
product was purified by flash column chromatography, affording the final product in 57.3 % yield. H NMR
(500MHz, DMSO-d6) 0.9(t, J = 6.5 Hz, 9H, CH3), 1.31(m, 6H, 3хCH2), 1.74(m, 6H, 3х CH2), 4.16 (m, 6H, 3х
CH2), 7.28(d, J = 7.6 Hz, 3H, ArH), 7.41(t, J = 6.2 Hz, 6H, ArH), 7.62(m, 12H, ArH), 7.75(d, J = 7.6 Hz, 9H,
ArH), 8.17(d, J = 5.9 Hz, 3H, ArH); 13C NMR (75 MHz, DMSO-d6, δ, ppm) 171.46, 143.89, 140.65, 140.30,
131.63, 136.12, 133.00, 132.98, 131.63, 129.23, 129.00, 128.45, 127.69, 126.73, 126.44, 126.02, 124.31, 124.50,
123.39, 122.64, 122.28, 121.58, 120.74, 120.45, 119.42, 116.80, 112.32, 109.37, 108.98, 95.12, 90.45, 86.65,
86.49, 58.06, 49.56, 43.31, 34.74, 31.01, 30.12, 20.07, 13.85; HRMS (m/z, MALDI): [M + H]+ calculated for
C75H60N6: 1045.3107; found 1045.3124; Elemental analyses, found C, 86.15; H, 5.77; N, 8.05 calculated for
C75H60N6 C, 86.17; H, 5.79; N, 8.04.
2.2.8.2. Synthesis of green fluorescent dye 10
Fluorescent dye 10 was synthesized using intermediate C7 (3.6mmol, 2.48g) and intermediate A1 (1mmol, 1.4g)
based on the above method, affording the final product in 61.3 % yield. 1H NMR (400MHZ, DMSO-d6) 7.29(m,
9H, ArH), 7.47(m, 9H, ArH), 7.58(m, 9H, ArH), 7.65(d, J = 7.7 Hz, 6H, ArH), 7.75(d, J = 6.9 Hz, 9H, ArH),
7.94(d, J = 5.1 Hz, 3H, ArH), 8.55(d, J = 1.8 Hz, 3H, ArH); 13C NMR (75 MHz, DMSO-d6, δ, ppm) 171.46,
141.38, 140.62, 137.60, 136.12, 132.98, 131.63, 129.25, 128.45, 127.69, 127.10, 126.44, 124.72, 124.50, 123.39,
123.23, 120.74, 120.45, 119.42, 109.95, 109.37, 90.45, 86.65; HRMS (m/z, MALDI): [M + H]+ calculated for
C81H48N6: 1105.2813; found 1105.2823; Elemental analyses, found C, 88.04; H, 4.35; N, 7.57 calculated for
C81H48N6 C, 88.02; H, 4.38; N, 7.60.
2.3. Geometryoptimization of dyes
Time-dependent density functional theory (TD-DFT) and discrete Fourier transform (DFT) were carried
out using the Gaussian 09 programs using the B3LYP, 6-31G as the standard. Hence, the geometry type and
Frontier molecular orbital (FMO) are calculated. The core twist angle in intermolecular interactions was
analyzed by geometry calculations. In case of naphthalimide, the carbazole angle was calculated from the center
of the triphenylamine main body, the angle between the acetylene linkage and naphthalimide, carbazole, and the
substituent. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO),
band gap, and electron density were calculated by FMO calculations.

3. Results and Discussion
3.1 Dye synthesis
Some dyes and intermediates were reported in the previous studies [1,4] featuring their excellent quantum
yields for the acetylene-linked fluorescent dyes containing an n-butyl or a phenyl ring at the N-position of 1,8-
naphthalimide. The six fluorescent dyes 1-6 were synthesized in six steps, such as iodination, bromination,
alkylation, aminolysis, Sonogashira coupling, and hydrolysis, respectively [1,24].
The iodination of carbazole was carried out under acidic conditions to be substituted at position 3 of
carbazole, resulting in reaction yield of 72.7 % yield. In case of extension of the reaction time after the addition
of KI the di-iodinated side product formed mainly, thereby the yield of intermediate C1 was decreased to 42 %.
For N-alkylation reaction, the use of polar aprotic solvent, such as DMF, could enhance the reactivity of
typical SN2 reaction. The Sonogashira coupling reaction for 3rd step was successfully carried out by using
anhydrous toluene, 10 mol % of bis(triphenylphosphine)palladium(II) dichloride, catalytic amounts of CuI and
triphenylphosphine, under these conditions the reaction completed in 1 hr. The reaction rate of the following
hydrolysis was increased by the use of comparatively less polar solvent, such as toluene, to compare that of
polar solvent, such as iso-propylalcohol, resulting in the reaction yield of 76 % [1,25].
In scheme 6, the bromination of 1,8-naphthalic anhydride was carried out under acidic conditions to
increase the selectivity to substitute at the 3-position of 1,8-naphthalimide ring, therefore the reaction yield of
56.7 % obtained. The consequent aminolysis reaction was readily carried out using n-butylamine and ethanol,
under these conditions a reflux for 1 hr provided reaction yield of 74.2 %.
The synthetic schemes for dye intermediates were shown in Scheme 1, Scheme 5, and Scheme 6 for
intermediates T1-3, intermediate C4, and intermediate N4, respectively. For the synthetic scheme of six final
fluorescent dyes 1-6 was also illustrated in Scheme 7.
Two dyes 7-8 containing a central group of diphenylsulfone were prepared via an intermediate S1 which
was readily synthesized from bromobenzene and chlorosulfonic acid, as shown in Scheme 2, then two bromo
atoms were substituted by an acetylene group of N-n-butyl-carbazole (C4) or N-phenyl-butyl-carbazole (C7)
using Sonogashira coupling reaction conditions (Scheme 8) resulting in reasonable reaction yield of 75.8% and
68.3 %, respectively. For a dye intermediate C7, three consequent reaction steps were carried out, as shown in
Scheme 6.
The other dyes 9-10 containing a central group of triphenyltriazine were similarly synthesized via an
intermediate A1 which was prepared from 4-bromobenzonitrile and triflic acid, as shown in Scheme 3, then two
bromo atoms were also substituted by an acetylene group of N-n-butyl-carbazole (C4) or N-phenyl-butyl-
carbazole (C7) utilising Sonogashira coupling reaction conditions (Scheme 9), where comparatively lower
reaction yields were found by 57.3% and 61.3 %, respectively. The higher reaction yields in Sonogashira
coupling for dyes 7-8 can be explained by the enhanced electrophilicity of phenyl ring by the presence of an
electron-withdrawing group, sulfone group, however a triazine ring also exerted an electron-withdrawing effect
therefore the difference in reaction yield was not too significant.

3.2. Absorption and fluorescence spectroscopic properties
Based on the TD-DFT theory using the Gaussian 09 package, the geometry of the six synthesized
fluorescent dyes 1-6 was analyzed, and the calculated maximum absorption wavelengths and oscillator strength
were summarized in Table 1. By comparison between the calculated absorption maxima and the observed
absorption maxima, as shown in Table 2, for dyes 1-6, it was more reliable to predict for two dyes 1 & 2, which
mono-carbazole or di-carbazole substituted analogous, where the deviations were less than 3 nm [26], whereas
the difference of 16 nm became bigger for dye 3 that substituted by tri-carbazole groups. In case of N-n-butyl-
naphthalimidyl analogous, the deviations in absorption maxima were observed by 14 nm, 6 nm, and 9 nm for
dyes 4-6, respectively.
Table 1
Calculated absorption maxima and F values for fluorescent dyes 1–6.
Calculated absorption maxima (nm) and F values
Fluorescent dyes
cal
λmax
330
333
357
418
430
431
F
1.57
1.39
1.42
1.61
1.57
1.98
1
2
3
4
5
6
Fluorescent dyes 1–3 exhibited the maximum absorbance at 330–341 nm, whereas fluorescent dyes 4–6
bathochromically shifted leading to the absorption maxima at 432–440 nm, as shown in Table 2. It was clearly
found that as the number of acetylene group which introduced to the triphenylamine moiety increased, the more
bathochromic shift was exhibited for all six dyes 1-6. This red shifts can be attributable to the increased
conjugation of π-orbitals, where the presence of three acetylene linkage groups connected to a carbazole ring
contributed a bathochromic shift of 11 nm comparing to that of corresponding dye 1 containing an acetylene
linkage group. The same red shift was also observed by 8 nm comparing the dye 6 containing three acetylene
groups to the corresponding dye 4. It was unusual that the absorption maxima of dyes 4-6 substituted by
naphthalimidyl group were bathochromic shifted significantly comparing to the corresponding dyes 1-3 which
containing the same number of carbazole analogous. These red shifts that exhibited in the range of 99 nm ~ 102
nm may be arisen by the more efficient conjugations between central triphenylamine system and naphthalimidyl
group via an acetylene linkage group than performed by corresponding carbazole analogous. It can be also
assumed that the planarity of π-conjugations throughout the dye molecule for naphthalimidyl based dyes 4-6
retained. By comparing the dye 3 containing three N-n-butylcarbazole substituents to the corresponding dye 9,
the triphenyltriazine ring as a central moiety contributed a bathochromic shift of 21 nm due to the increased π-
conjugations by a triazine ring. It was also found that the presence of a N-phenyl ring in the carbazole system

created a bathochromic shift comparing to that of N-n-butyl group, therefore dye 10 exhibited a bathochromic
shift of 8 nm to the that of dye 9 due to the increased π-conjugations.
Judging from the results of Density Functional Theory (DFT) and Time-Dependent DFT calculations, as in
Fig. 2 and Table 3, the carbazole and naphthalimide groups were twisted around the acetylene linkage; therefore
the efficiency of π-conjugations decreased led to the increased energy difference between HOMO and LUMO
levels. In contrast, the connection between the triphenylamine and the acetylene linkage group retained a planar
structure at the center contributing to the delocalization of π orbitals on the dye molecule.
The molar extinction coefficients of fluorescent dyes 1–3 ranged from 16,000 to 17,000, which were
apparently similar regardless of the difference in the number of carbazole group, and the molar extinction
coefficient of fluorescent dyes 4–6 ranged from 17,000 to 19,000, where the more substituents the stronger in
molar extinction coefficient. It was also found that the dyes 7-10 those contained a central group of diphenyl
sulfone or 2,4,6-triphenyl-1,3,5-trazine group provided higher molar extinction coefficients to compare that of
corresponding dyes 1-6. Although the relationships between the dye structure and the molar extinction
coefficients to be often difficult to explain, in these dye series the stronger electron-withdrawing effect by two
central moieties can be attributable to the increased molar extinction coefficients. In other words, both the
sulfonyl group and triazine ring exerted readily enhanced effects to accept π-electrons from the electron donor, a
nitrogen atom in N-substituted carbazole ring.
The maximum emission wavelengths of 1–3 were observed at 401 nm, 416 nm, and 430 nm, respectively,
whereas corresponding dyes 4–6 exhibited 580 nm, 595 nm, and 604 nm, respectively, therefore the bigger
Stokes’ shifts were observed by naphthalimidyl analogous, as summarized in Table 2. As the number of
substituent coupled to the central moiety increased, the Stokes shifts tended to increase. It can emphasize that
both contributions of the bathochromic shifts at absorption maxima and larger Stokes shifts by naphthalimidyl
substituted dyes 4-6 readily provide a red emission, whereas the corresponding carbazole substituted dyes
emitted a blue fluorescence. In similar, two dyes 9-10 containing a central moiety of triphenyltriazine also
exhibited comparatively larger Stokes shifts of 140 nm or 145 nm, than that of corresponding triphenylamine
based analogous 1-3 combined with a bathochromic shift in absorption maxima leading to a green fluorescence
emission. As shown in Figure 1, all dye solutions were prepared at 100 ppm concentration in CH2Cl2. Strictly
speaking, the visual color depths of dye 3 and dye 6 seem to be comparatively stronger than other two dyes
among 2 set of blue and red three dyes that coincides to the relative strength of quantum yields, as in Table 2.
In terms of quantum yield, there was a tendency that dyes 7–10 containing a central moiety of
triphenyltriazine or diphenylsulfone exhibited consistently higher quantum yields of 0.83 to 0.85, whereas the
other dyes 1–6 varied their quantum yields from 0.34 to 0.89 depending on the substituent. In this series, the
highest quantum yield was observed by dye 3 where as the number of substituent, such as N-n-butyl carbazole
or N-n-butyl naphtalimidyl, increased the higher quantum yield was provided, therefore it can be explained that
the enhanced π-conjugations could contribute the stronger emission.

Table 2
Absorption and fluorescence properties of the synthesized dyes.
ab
em
Fluorescent dyes
λmax
λmax
Stokes shift
(nm)
71
εmax
(dm3 mol-1 cm-1)
16,000
Quantum yield
(nm)
330
336
341
432
436
440
346
358
362
370
(nm)
401
416
430
580
595
604
444
452
502
515
0.68
0.72
0.89
0.34
0.44
0.78
0.83
0.85
0.83
0.85
1
2
3
4
5
6
7
8
9
80
89
148
159
164
98
94
140
145
17,000
16,000
17,000
18,000
19,000
43,000
44,000
41,000
42,000
10
λmaxab, λmaxem: determined in methylene chloride(1.0×10−5 mol/L)
Reference: Anthracene.
Fig. 1. Optical images of fluorescent dyes 1–10 in methylene chloride solutions (100 ppm) under a UV light of
365 nm.
3.3. Calculations of dye structure geometry
The presence of any substituent at the N-position of carbazole or naphthalimide ring, it can affect readily
the geometry of dyes by the resultant π–π interactions by a substituent. This tendency was observed when the
geometry of dye molecule was analyzed on the basis of time-dependent density functional theory (TD-DFT) of
the six dyes 1-6 [27-30]. The dihedral angles between central nitrogen atom and three individual phenyl rings
were calculated in Table 3, in which n-butyl substituent at the N-position of the carbazole or naphthalimide ring

exhibited a distorted structure with some extents of dihedral angles. The calculated dihedral angles were
revealed 0.14 °, 3.13 °, and 3.19 ° for three individual phenyl rings 1-3 of dye 1, where the least distortion was
calculated by a carzole substituted phenyl ring 1 due to the efficient conjugation of π-orbitals, thus it can be
assumed that dye 1 contained a planar bond, between a carbazole connected acetylene group and phenyl ring 1,
and two comparatively distorted bonds unsubstituted phenyl rings 2-3. In contrast, the dihedral angles of three
corresponding bonds for dye 3 were appeared to be 0.48 °, 0.39 °, and 0.42 ° indicating all bonds retained a
planar geometry. These calculated results suggested that as the number of substituents to triphenylamine central
moiety increased, the planarity of the dyes was comparatively enhanced which mainly related to the efficient π -
conjugations between carbazole ring and triphenylamine system.
The similarity of the effect of substituents was also observed by dyes 4-6, those substituted by
corresponding N-n-butyl-naphthalimide, where the dihedral angles of mono-substituted triphenylamine of dye 4
were calculated as 1.02 °, 3.22 °, 4.02 °, thus phenyl ring 1 retained its planarity but other two analogues 2-
exhibited more distorted angle. The dihedral angles for dye 6 were calculated by 0.97 °, 1.13 °, and 1.31 °
revealing three individual bond angles to be comparatively planar that should be also attributable to the
increased conjugations of π-orbitals between naphthalimide, acetylene group and triphenylamine systems. In
case of dye 5, an unsubstituted phenyl ring 3 was calculated by its highly distorted form accounting for dihedral
angle of 7.82, whereas two other phenyl rings 1-2 retained planarity as calculated for 1.75 and 1.62.
It can be emphasized that the enhanced planarity directly contributed the improved thermal stability, as
summarized in Table 4. In comparisons of the weight reductions for dyes 1-6, it was apparently found that the
increased planarity of dye directly contributed to the higher thermal stability, where dye 3 and dye 6 exhibited
better stabilities in weight reduction.
The geometry-optimized structures of the fluorescent dyes 1-6 were illustrated in Figure 2, and the results
of the calculated dihedral angles for dyes 1-6 were also summarized in Table 3.

Fig. 2. Geometry-optimized structures of the fluorescent dyes 1-6.
Table 3
Theoretically calculated dihedral angles.
R1
C4H9
N
C4H9
N
1
O
O
N
3
2
R3
R2
Carbazole
Naphthalimide
Triphenylamine
Α (°)
Β (°)
Γ (°)
Fluorescent
dyes
R1
R2
R3
1
2
3
1
2
-
3
-
1
2
-
3
-
C
C
C
H
C
C
H
H
C
0.14
2.13
0.48
3.13
3.19
0.45
0.32
1
2
3
4
5
6
2.62
0.39
4.68
0.42
1.1
1.6
-
1.2
1.4
-
0.86
0.79 0.81
0.62
0.54
0.66
N
N
N
H
N
N
H
H
N
1.02
1.75
0.97
3.22
1.62
1.13
4.02
7.82
1.31
0.71
1.74
6.93
-
-
-
0.60
0.84
6.93
-
-
-
1.61
1.02
4.17
5.30 4.25
3.26

*α1(°)=N of triphenylaminebenzene(1) of triphenylamine bond dihedral angles, R1-acetylene bond dihedral angles, α2(°)=N of
triphenylamine-benzene(2) of triphenylamine bond dihedral angles, α3(°)=N of triphenylamine-benzene(2) of triphenylamine bond dihedral
angles, β1(°)=R1- acetylene bond dihedral angles, β2(°)=R2- acetylene bond dihedral angles, β3(°)=R3- acetylene bond dihedral angles,
γ(°)=C- acetylene bond dihedral angles
3.4 Thermal stability of dyes 1-10
Factors such as π–π interactions, intermolecular hydrogen bonding, and van der Waals forces affect heat
resistance; however, in the case of π–π interactions, it becomes sufficiently strong to have a planar molecular
structure. The temperature at which the acetylene linkage in the synthesized fluorescent dyes 1–3 was
decomposed and the thermal decomposition temperature of the fluorescent dyes was in the range of 297 °C to
333 °C. In case of fluorescent dyes 1 and 2, the thermal decomposition temperature was 297 °C, which was less
than that of fluorescent dye 3, comprising a structure in which carbazole is twisted around tripheylamine: π–π
interaction decreased and the relative paralysis was low. Fluorescent dyes 1 and 2 in which the carbazole moiety
was not on the same plane as tripheylamine were thermally decomposed at a temperature less than that of
fluorescent dye 3.
The temperature at which the acetylene linkage of the synthesized fluorescent dyes 4 to 6 was destroyed
and the thermal decomposition temperature of fluorescent dyes was in the range of 320 °C to 357 °C. For
fluorescent dyes 4 and 5, the thermal decomposition temperature was 320 °C, which was less than that of
fluorescent dye 6, comprising a structure in which naphthalimide was twisted around triphenylamine, and π–π
interactions decreased, with a relatively low heat decomposition temperature. The naphthalimide moiety was not
present on the same plane as triphenylamine. Fluorescent dyes 4 and 5 were paralyzed at a temperature less than
that of fluorescent dye 6. When triphenylamine and the substituent were not present in the same plane and
became a twisted structure, heat resistance was not satisfactory. For a comparison of the substituent effects
between N-n-butyl group and N-phenyl group, it was observed that N-phenyl group afforded higher resistance to
the weight reductions at 300 °C than that of N-n-butyl analogue, as shown in table 4. This contribution can be
explained by the extended conjugations of π-orbitals, caused by a phenyl ring, resulting in the more efficient
delocalization of π-electrons throughout the dye molecule. Therefore, it can also assume that the most
substituted analogue 10 by N-phenyl carbazole systems in these series exerted the least weight reduction of 0.19
% at 300 °C.
As previously discussed in the calculations of dye structure geometry, the planarity of dye molecule was one
of important parameters to affect thermal stabilities. In the series of carbazole substituted dyes 1-3, the less
weight reductions observed by the more presence of carbazole substituents those afforded comparatively more
planar geometry. The same tendency was found in the corresponding series of dyes 4-6, in which more
substitutions by naphthalimide ring and acetylene linkage exerted improved thermal stabilities.
Table 4 summarizes the results of thermogravimetric analysis (TGA) for the dyes 1–10 [31].

Table 4
Thermogravimetric analysis (TGA) of fluorescent dyes 1–6.
Thermal stability
Fluorescent Dyes
Weight reduction (%, 300 °C)
4.40
0.76
0.23
1
2
3
3.20
1.81
1.93
4.20
1.02
1.65
0.19
4
5
6
7
8
9
10
3.5. TD-DFT and frontier molecular orbital (FMO)
As illustrated in Figure 3, the comparison of the HOMO and LUMO levels of the synthesized fluorescent
dyes revealed that the LUMO-level electrons are localized on the substituent carbazole, 1,8-naphthalimide
position, while the HOMO level is localized on the triphenylamine position. Hence, electrons are confirmed to
be localized by the removal of the alkyl chain and N-position substituent in the N-position at the LUMO level,
verifying that electrons are localized, while the alkyl chain substituents in the N-position are structurally twisted.
The figure possibly confirmed, but in the case of a fluorescent dyes in which the alkyl chain is substituted at the
N-position and the acetylene linkage was substituted for the carbazole or 1,8-naphthalimidyl ring, the acetylene
linkage in the center the π electrons became delocalized.
The HOMO and LUMO values calculated by the TD-DFT theory revealed similar values for the HOMO
(0.07) and LUMO (0.05) for the number of acetylene linkages which due to the interruption in the π-conjugation,
including acetylene linkage, by an alkyl chain due to the twisting of the structure; hence, the substituted butyl
group does not considerably affect the N-position [32-33].
The ΔE values were clearly determined by the effect of the HOMO and LUMO values according to the
number of substituents in the acetylene linkage, as shown in Table 5. This trend was observed for all six

synthesized fluorescent dyes. By considering the ΔE for each fluorescent dye, the ΔE value for the synthesized
fluorescent dyes 1–3 exhibited a large difference of 0.09 due to the increase in the π-conjugation when a dye
comprising an acetylene linkage exhibits a twisted structure centered on the acetylene linkage.
`
Fig. 3. Molecular orbital models of the HOMOs and LUMOs of fluorescent dyes 1–6.
The ΔE values were clearly determined by the energy difference between the HOMO and LUMO values
according to the number of substituents in the acetylene linkage, as summarized in Table 5. As it was calculated
by TD-DFT method, the less ΔE values for dyes 4-6 compared to that of corresponding dyes 1-3 can be
explained by more efficient π-conjugations arisen from a planar structure between naphthalimide ring and

acetylene group [34-35]. In contrast, comparatively less planar forms between carbazole ring and acetylene
group can be responsible for the increased ΔE values. These calculated results were in accordance with the
observed absorption maxima for dyes 1-6, as summarized in Table 2.
Table 5
Results of TD-DFT calculations for energy difference values between the HOMO and the LUMO of the
synthesized dyes 1-6.
Fluorescent dyes
HOMO
LUMO
ΔE (HOMO-LUMO)
2.58
2.50
2.46
1.76
1.68
1.65
1
2
3
4
5
6
−7.67
−7.62
−7.60
−7.70
−7.78
−7.61
−5.09
−5.12
−5.14
−5.94
−6.10
−5.96
3.6. Electron density
From the calculated electron densities for the dyes 1–3, the carbazole system exhibited higher electron
densities than the central moiety of triphenylamine that indicated both nitrogen atoms in the carbazole and
triphenylamine rings exerted as an electron donor, thus these dyes 1-3 can be a donor-π-donor chromogen. In
contrast, other dyes 4–6, higher electron densities of carbonyl groups in the naphthalimidyl ring were calculated,
therefore it can be assumed that these carbonyl groups may act as an electron acceptor leading to stronger
donor-π-acceptor chromogen [36-37]. The calculated electron densities of dyes 1-6 were illustrated in Figure 4.
Fig. 4. Electron densities of fluorescent dyes 1–6.

4. Conclusions
Judging from the absorption maxima of dyes 1-6 prepared, it was found that increase of the number of
acetylene group which introduced to the triphenylamine moiety readily exhibited a bathochromic shift. This red
shifts can be attributable to the increased conjugation of π-orbitals. It was unusual that the absorption maxima
of dyes 4-6 substituted by naphthalimidyl group were bathochromic shifted significantly comparing to the
corresponding dyes 1-3 which containing the same number of carbazole analogous. These red shifts may be
arisen by the more efficient conjugations between central triphenylamine system and naphthalimidyl group via
an acetylene linkage group than performed by corresponding carbazole analogous due to the retention of
planarity of π-conjugations throughout the dye molecule for naphthalimidyl based dyes 4-6. It was also
observed that the presence of a N-phenyl ring in the carbazole system created a bathochromic shift comparing to
that of N-n-butyl group that can be also attributable to the increased π-conjugations.
Both contributions of the bathochromic shifts at absorption maxima and larger Stokes’ shifts by
naphthalimidyl substituted dyes 4-6 readily provide a red emission, whereas the corresponding carbazole
substituted dyes emitted a blue fluorescence. In contrast, two dyes 9-10 containing a central moiety of
triphenyltriazine exhibited comparatively larger Stokes’ shifts than that of corresponding triphenylamine based
analogous 1-3 combined with a bathochromic shift in absorption maxima leading to a green fluorescence
emission.
From the geometry analysis based on the TD-DFT theory of the six synthesized fluorescent dyes,
carbazole-based fluorescent dyes 1–3 did not exhibit the twisting of the substituents at the N-position, and
naphthalimide-based fluorescent dyes 4–6 exhibit a planar structure with the 1,8-naphthalimide and carbazole
moieties located in the same plane except for the twisting of the substituents at the N-position.
In terms of quantum yield, there was a tendency that dyes 7–10 containing a central moiety of
triphenyltriazine or diphenylsulfone exhibited consistently higher quantum yields of 0.83 to 0.85, whereas the
other dyes 1–6 varied their quantum yields from 0.34 to 0.89 depending on the substituent.
With respect to heat stability, carbazole- and naphthalimide- based fluorescent dyess exhibited thermal
decomposition temperatures of >250 °C and >300 °C, respectively. The introduction of acetylene linkages in
fluorescent dyes improved the planarity, which in turn lead to excellent heat resistance due to the considerably
strong π–π interactions.
Acknowledgements
This work was supported by the Technology Innovation Program funded by the Ministry of Trade, Industry and
Energy (KOREA).

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