Synthesis and characterization of triazine linked carbazole derivatives green-light-emitting molecules

Article abstract of DOI:10.1016/j.dyepig.2017.04.065

Novel 2,4,6-triphenyl-1,3,5-triazine linked carbazole through olefin double bond star shape molecules with different linear and branched chain were synthesized and systematically investigated by aggregation induced emission (AIE) studies and electrochemical properties. These molecules are shows broad absorbance range with good intramolecular charge transfer character (ICT). These derivatives are exhibit positive solvatochromism effect and higher Stokes shift values in the range of 6819–1119?cm^?1. These derivatives are displayed aggregation-induced emission (AIE) property in THF-water mixture (TRZ-hexyl at 10/90%, TRZ-octyl at 30/70%, TRZ-branched at 50/50%). The electrochemical studies show that band gap of TRZ-hexyl, TRZ-octyl, and TRZ-branched at 1.87, 1.73?eV, and 1.86?eV respectively. All these derivatives are exhibit deep-lying highest occupied molecular orbital (HOMO) energy levels at?～??5.04?eV and LUMO energy levels at?～??3.20?eV. The proper AIE, HOMO, and LUMO energy level pave the way for their potential use in OLEDs and solar cell applications.

Full text of DOI:10.1016/j.dyepig.2017.04.065

Accepted Manuscript
Synthesis and characterization of triazine linked carbazole derivatives green-light-
emitting molecules
Govindasamy Sathiyan, Pachagounder Sakthivel
PII:
S0143-7208(17)30252-8
10.1016/j.dyepig.2017.04.065
DYPI 5963
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 9 February 2017
Revised Date: 19 April 2017
Accepted Date: 25 April 2017
Please cite this article as: Sathiyan G, Sakthivel P, Synthesis and characterization of triazine linked
carbazole derivatives green-light-emitting molecules, Dyes and Pigments (2017), doi: 10.1016/
j.dyepig.2017.04.065.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
TRZ-hexyl
TRZ-octyl
H2O
TRZ-branched

ACCEPTED MANUSCRIPT
Synthesis and characterization of triazine linked carbazole
derivatives green-light-emitting molecules
Govindasamy Sathiyana, Pachagounder Sakthivela,b,*
a Department of Chemistry, School of Advanced Sciences, VIT University, Vellore-632014, Tamil Nadu, India.
b Department of Nanoscience and Technology, Bharathiar University, Coimbatore-641046, Tamil Nadu, India.
Corresponding author. E-mail address: sakthivel.p@buc.edu.in, and polysathi@gmail.com (P. Sakthivel)
Abstract
Novel 2,4,6-triphenyl-1,3,5-triazine linked carbazole through olefin double bond star
shape molecules with different linear and branched chain were synthesized and systematically
investigated by aggregation induced emission (AIE) studies and electrochemical properties.
These molecules are shows broad absorbance range with good intramolecular charge transfer
character (ICT). These derivatives are exhibit positive solvatochromism effect and higher Stokes
shift values in the range of 6819-1119 cm-1. These derivatives are displayed aggregation-induced
emission (AIE) property in THF-water mixture (TRZ-hexyl at 10/90%, TRZ-octyl at 30/70%,
TRZ-branched at 50/50%). The electrochemical studies show that band gap of TRZ-hexyl, TRZ-
octyl, and TRZ-branched at 1.87, 1.73 eV, and 1.86 eV respectively. All these derivatives are
exhibit deep-lying highest occupied molecular orbital (HOMO) energy levels at ~ -5.04 eV and
LUMO energy levels at ~ -3.20 eV. The proper AIE, HOMO, and LUMO energy level pave the
way for their potential use in OLEDs and solar cell applications.
Key words: Triazine; Carbazole; Aggregation-induced emission (AIE); D-A type molecules;
Fluorescence emission; OLED.
1. INTRODUCTION
In the past decades, organic π-conjugate materials are received more attention in potential
applications of organic light-emitting diodes (OLEDs) and then organic solar cells because of
their low cost, flexibility and easy to fabrication on the devices [1-5]. Presently, research groups
were focused on three-arm based N-donor molecules due to their excellent electron donating
strength, good thermal stability, photophysical properties and high fluorescence quantum yield
[6-8]. The bipolar materials were used as an emitting layer for achieve high-performance full
colour organic OLEDs device [9,10]. Further, bipolar materials can deliver high balanced carrier
transportation ability and support to enhance the chance for carrier recombination. To improve
the light emitting nature towards design Donor-Acceptor (D-A) type molecules, it’s facilitated
both electron and hole transporting property in the same molecules [11-13]. Triazine is one of the
significant core centre to established wide range of optical and electrical applications, such as
biomolecular labels, photosensitizers, sensors, solar cell, and OLEDs [14-17]. These molecules
have higher electron affinity and symmetrical structure. Triazine molecules could be triply
1

ACCEPTED MANUSCRIPT
functionalized with various electron-donating and electron-acceptors to given star-shaped
architecture. Triazines are three-arm electron-deficient moiety, attached in a centre of electron
rich moieties are certain attention since they are extended the π-conjugation from the hetero-
cyclic triazine-core to the aromatic donor-substituents [18]. This π-conjugation of triazine centre
widely employed different electron-donors such as carbazole, fluorene, diphenyl amine, and
triphenyl amine moieties [19,20]. Among these, carbazole is more attractive electron-donors
because of it could be easy way functionalized with various functional groups. In the presence of
nitrogen moiety provides fully aromatic, high thermal and environmental stability [21-24].
When compared with linear and dendrite molecules, hyper-branched polymers are exhibit
advantage for their process-ability into large-scale devices and simple synthetic access [25-27].
These hyper-branched molecules were compared with linear molecules, which exhibit unique
advantages for their easy synthetic and large-scale device processability. Further, those hyper-
branched molecules are having excellent properties, such as intramolecular charge transfer (ICT)
(between donor and acceptor moiety), low viscosity and high solubility. These are key properties
for the organic solar cells, two-photon absorption materials and organic light-emitting diodes
applications [28,29]. The hyper-branched molecules have been proven the structure correlation
effect which can help two-photon absorption due to their push-pull properties and co-planarity of
the molecules. To improve the solution processability of the organic molecules, it’s one of the
important strategies attachments of (linear or branched) alkyl substituents on the molecule
backbone [30]. Further, these substituent’s affect molecular packing and effective charge
transport properties. To compare linear with branched side chain contain molecule shown more
π-π stacking, lamellar spacing and self-assembling properties in thin-film devices. Matulaitis and
co-workers reported 2,4,6-triphenyl-1,3,5-triazine linked carbazole with different nitrogen
position molecules used as the light emitting materials for OLEDs applications [31]. Kukhta et
al., reported 2,4,6-triphenyl-1,3,5-triazine linked fluorene molecules showed high thermal
stability with good hole transporting properties [21]. Reghu et al., reported triazine linked with
different donor’s molecules were showed good fluorescence quantum yield [32]. Recently, we
are reported triazine linked carbazole based macromolecules were showed AIE property with
good fluorescence quantum yield [33].
In this work, we have reported carbazole and triazine containing star-shaped molecules
with different side chains such as hexyl, octyl, and 2-ethyl hexyl. In the presences of the side
chain on the AIE properties are great interest. We have investigated the results of optical
properties, electrochemical properties, and AIE effect.
2

ACCEPTED MANUSCRIPT
Scheme 1. Synthesis of triazine derivatives
R
N
N
N
N
N
R
N
R
TRZ-hexyl; R =
TRZ-octyl; R =
TRZ-branched; R =
Fig. 1. Structure of triazine derivatives
3

ACCEPTED MANUSCRIPT
2. Experiments
2.1. Materials
p-Bromomethylbenzonitrile, trifluoromethanesulfonic acid, triethylphosphite, 18-crown-
6, carbazole, 1-bromohexane, 2-ethyl hexyl bromide and 1-bromooctane were purchased from
Sigma-Aldrich. Phosphoryl chloride (POCl3), dry dimethylformamide (DMF), dichloromethane
and chloroform solvent were obtained from SD Fine-Chem Limited. Potassium tert-butoxide (t-
BuOK), sodium hydroxide (NaOH) and potassium hydroxide (KOH) were purchased from
AVRA Company. Other solvents were purchased commercially as AR-grade quality and then
used without further purification. Column chromatography was performed using silica gel Merck
(60-120 mesh).
2.2. Instrumentation
IR Spectrum was recorded on SHIMADZU Infrared spectrophotometer (400-4000 cm-1)
1
with resolution IV. H and 13C-NMR spectrum was carried using a Bruker 400 MHz
spectrometer in CDCl3 using tetramethylsilane as an internal standard. The UV-visible
absorption spectrum was recorded with a JASCO V-670 spectrophotometer at room temperature.
Fluorescence spectrum was recorded using Hitachi F-7000FL spectrometer. The cyclic
voltammetry (CV) studies were carried out with (CH Instruments) at a scan rate of 100 mV/s.
The surface morphology of the sample was investigated by scanning electron microscopy (Carl
Zeiss EVO-185H, UK) equipped with an energy-dispersive X-ray spectrometer (EDX).
2.2.1. Synthesis of 2,4,6-tris [4-(diethylphosphonomethyl) phenyl]-1,3,5-triazine (TRZ)
The compound was synthesized according to our previous reported procedure method
1
[34]. (2.45 g, yield: 92%). H-NMR (CDCl3, 400 MHz, ppm): 8.71-8.69 (d, 6H, J = 7.6 Hz),
7.51-7.49 (d, 6H, J = 7.2 Hz), 4.06-4.02 (t, 12H, J = 7.2 Hz), 3.30-3.25 (d, 6H, J = 22 Hz), 1.28-
1.24 (t, 18H, J = 6.8 Hz). 13C-NMR: 171.51, 136.83, 136.74, 135.13, 135.09, 130.37, 130.30,
129.35, 62.58, 62.52, 34.97, 33.60, 16.63, 16.57.
2.2.2. Synthesis of 9-hexyl-9H-carbazole (R1)
Carbazole (3.30 g, 20 mmol), potassium hydroxide (2.96 g, 52.8 mmol) dissolved in
DMF (40 mL) and then 1-bromohexane (3.30 g, 20 mmol) was added in dropwise. The reaction
mixture was stirred at room temperature for 48 h. The reaction mixture was poured into water
and extracted with chloroform and dried over anhydrous magnesium sulphate. The solvent was
removed by rotary evaporator, the residue was re-crystallized in n-hexane to afford compound Ia
(4.8 g, yield: 92%) as a white solid. 1H-NMR (400 MHz, CDCl3, ppm): 8.11–8.09 (d, 2H, J = 2.4
Hz), 7.46–7.42 (m, 2H), 7.42–7.39 (d, 2H, J = 8.4 Hz), 7.26–7.20 (m, 2H), 4.31–4.28 (t, 2H, J =
7.2 Hz), 1.88–1.85 (m, 2H), 1.41–1.37 (m, 6H), 0.86 (t, 3H).
4

ACCEPTED MANUSCRIPT
2.2.3. Synthesis of 9-(2-ethylhexyl)-9H-carbazole (R3)
To the mixture of carbazole (5 g, 30 mmol) and sodium hydroxide (7.2 g, 185 mmol)
were dissolved in 100 mL of DMSO and the reaction mixture was stirred at room temperature for
1 h. The 2-ethylhexyl bromide (6.9 g, 36 mmol) was added in a drop wise to the reaction mixture
at room temperature for a period of 30 min. The resulting reaction mixture was further stirred for
24 h. After cool to room temperature, the mixture was poured into water and the organic layer
was extracted with dichloromethane and dried over anhydrous magnesium sulphate. The crude
product was further purified by column chromatography using hexane: ethyl acetate (9:1) as the
eluent. Compound Ib (6.9 g, yield: 82 %, colourless oil). 1H-NMR (400 MHz, CDCl3, ppm): 8.23
(d, 2H), 7.57 (t, 2H), 7.51 (d, 2H), 7.36-7.33 (t, 2H), 4.25-4.22 (m, 2H), 2.33-2.15(m, 1H), 1.41-
1.37 (m, 8H), 1.04 (m, 6H).
2.2.4. Synthesis of 9-octyl-9H-carbazole (R2)
The compound R2 was synthesized by followed similar procedure for compound R3.
1
Yellow liquid (yield: 85%). H-NMR (CDCl3, ppm): 8.18 (d, 2H, J = 7.60 Hz), 7.54–7.50 (m,
2H), 7.46 (d, 2H, J = 8.00 Hz), 7.31–7.27 (m, 2H), 4.34–4.31 (t, 2H, J = 7.20 Hz), 1.95–1.87 (m,
2H), 1.36–1.33 (m, 10H), 0.92 (t, 3H, J = 6.40 Hz).
2.2.5. Synthesis of 9-hexyl-9H-carbazole-3-carbaldehyde (Cz-hexyl)
POCl3 (25 mL, 0.27 mole) was added drop wise to DMF (35 mL, 0.45 mole) for 30 min
at 0 oC. Compound R1 (4.00 g, 16 mmol) or R2 or R3 in dichloromethane (20 mL) was added to
the above solution at room temperature after that increase the temperature to 90 oC and stirred for
4 h. The reaction mixture was poured into ice-cubes and neutralized with NaOH solution. The
solution was extracted three times with ethyl acetate and dried over anhydrous magnesium
sulphate. The excess of dichloromethane was removed by vacuum distillation. The crude product
was purified by column chromatography (eluent: hexane/ethyl acetate- 9:1) given the product as
white colour solid compound (9-hexyl-9H-carbazole-3-carbaldehyde (Cz-hexyl), yield: 68%).
1H-NMR (CDCl3, ppm): 10.07 (s, 1H), 8.57 (s, 1H), 8.14–8.12 (d, 1H, J = 8 Hz), 8.00–7.98 (dd,
1H, J = 6.8 Hz), 7.55–7.51 (t, 1H, J = 8 Hz), 7.44–7.42 (d, 2H, J = 8.4 Hz), 7.33–7.30 (t, 1H, J =
7.2 Hz), 4.30–4.26 (t, 2H, J = 7.6 Hz), 1.90–1.82 (m, 2H), 1.31–1.28 (m, 6H), 0.87 (m, 3H).
Synthesis of Cz-octyl: The compound Cz-octyl was synthesized by followed similar procedure
for compound Cz-hexyl. White colour solid (yield: 68%), 1H-NMR (CDCl3, ppm): 10.08 (s, 1H),
8.59 (s, 1H), 8.15-8.13 (d, 1H, J = 7.6 Hz), 8.01- 7.99 (dd, 1H, J = 8.8 Hz), 7.55-7.51 (t, 1H, J =
8 Hz), 7.46-7.44 (d, 2H, J = 8 Hz), 7.34-7.30 (t, 1H, J = 7.6 Hz), 4.32-4.29 (t, 2H, J = 7.2 Hz),
1.89-1.86 (m, 2H), 1.40-1.24 (m, 10H), 0.88 (m, 3H).
5

ACCEPTED MANUSCRIPT
Synthesis of Cz-branched: The compound Cz-branched was synthesized by followed similar
1
procedure for compound Cz-hexyl. colourless liquid (Cz-branched, yield: 68%), H-NMR
(CDCl3, ppm): 10.09 (s, 1H), 8.60 (s, 1H), 8.16-8.14 (d, 1H, J = 8 Hz), 8.01- 7.98 (dd, 1H, J =
8.4 Hz), 7.54-7.50 (t, 1H, J = 8 Hz), 7.46-7.43 (m, 2H), 7.34-7.30 (t, 1H, J = 7.6 Hz), 4.21-4.19
(d, 2H, J = 7.6 Hz), 2.09-2.05 (m, 1H), 1.38-1.26 (m, 8H), 0.88 (m, 6H).
2.2.6. Synthesis of TRZ-hexyl, TRZ-octyl, TRZ-branched
Common procedure:
To mixture of TRZ and Carbazole monomer in dry THF taken in 100 mL round bottom
flask under N2 atm. The potassium tert-butoxide and 18-crown-6 were added into the reaction
mixture, stirred overnight after poured into water. The compound was extracted with DCM and
washed with brine. The compound finally purified with column chromatography.
(2,4,6-tris(4-((E)-2-(9-hexyl-9H-carbazol-3-yl)vinyl)phenyl)-1,3,5-triazine (TRZ-hexyl): yield-
35%, yellow powder. 1H-NMR (CDCl3, ppm): 8.7 (s, 2H), 8.25 (s, 1H), 8.14-8.12 (d, 1H, J = 7.6
Hz), 7.72-7.70 (d, 2H, J = 8 Hz), 7.69-7.50 (t, 1H, J = 5.2 Hz), 7.50-7.44 (d, 2H, J = 8.4 Hz),
7.40-7.34 (t, 1H, J = 8.4 Hz), 7.27-7.20 (s, 2H), 4.25-4.22 (t, 2H, J = 7.2 Hz), 1.89-1.82 (m, 2H),
1.36-1.26 (m, 6H), 0.87 (m, 3H). 13C-NMR- 171.00, 142.03, 140.87, 140.49, 134.87,131.60,
129.38, 128.19, 126.30, 125.84, 125.36, 124.67, 123.25, 122.90, 120.49.119.13, 108.95, 43.20,
31.59, 28.98,26.98, 22.52, 14.03.FT-IR (cm-1): 2924 (CH3 stretch), 2208 (C triple bond N
stretch), 1581 (C-C stretch aromatic), 831 (alkyl halide). HRMS: Calculated for C81H78N6,
1134.6288; found 1134.6286.
(2,4,6-tris(4-((E)-2-(9-octyl-9H-carbazol-3-yl)vinyl)phenyl)-1,3,5-triazine (TRZ-octyl): yield-
1
25%, yellow powder. H-NMR (CDCl3, ppm): 8.77 (s, 2H), 8.29 (s, 1H), 8.15 (d, 1H, J = 4.8
Hz), 7.74- 7.25 (d, 3H, J = 6.4 Hz), 7.48-7.28 (m, 3H), 7.26 (s, 2H), 4.30-4.26 (t, 2H, J = 10.8
Hz), 1.88-1.87 (d, 2H, J = 5.6 Hz), 1.35-1.25 (m, 12H), 0.87 (m, 3H). 13C-NMR- 171.28, 142.29,
141.10, 140.78, 135.09,131.87, 129.65, 126.55, 126.10, 125.58, 124.90, 123.48, 123.11, 120.71,
120.51, 119.36, 109.19, 43.45, 32.04, 29.94, 29.62, 29. 43, 27.43, 22.85, 14.32. FT-IR (cm-1):
2924 (CH3 stretch), 2208 (C triple bond N stretch), 1581 (C-C stretch aromatic), 831 (alkyl
halide). HRMS: Calculated for C87H90N6, 1218.7227; found 1218.7225.
(2,4,6-tris(4-((E)-2-(9-(2-ethylhexyl)-9H-carbazol-3-yl)vinyl)phenyl)-1,3,5-triazine
(TRZ-
branched): yield- 30%, yellow powder. 1H-NMR (CDCl3, ppm): 8.79 (m, 2H), 8.29-8.28 (d, 1H,
J = 5.6 Hz), 8.14 (s, 1H), 7.72- 7.20 (d, 2H, J = 8 Hz), 7.52-7.48 (d, 2H, J = 7.6 Hz), 7.48-7.30
(m, 2H), 7.28-7.24 (m, 2H), 4.16-4.05 (t, 2H, J = 8 Hz), 2.09-2.04 (m, 1H), 1.36-1.25 (m, 8H),
0.91 (m, 6H). 13C-NMR- 171.11, 142.11, 141.40, 141.05, 134.94,131.69, 129.42, 128.22, 126.34,
125.86, 124.67, 123.28, 122.92, 120.43, 119.42, 119.07, 109.28, 47.59, 39.46, 29.72, 28.85,
24.47, 23.08, 14.02,10.93. FT-IR (cm-1): 2924 (CH3 stretch), 2208 (C triple bond N stretch),
6

ACCEPTED MANUSCRIPT
1581 (C-C stretch aromatic), 831 (alkyl halide). HRMS: Calculated for C87H90N6, 1218.7227;
found 1218.7226.
3. Results and discussion
3.1. Synthesis
The synthetic scheme of TRZ derivatives are shown in Scheme 1, names are 2,4,6-tris(4-
((E)-2-(9-hexyl-9H-carbazol-3-yl)vinyl)phenyl)-1,3,5-triazine (TRZ-hexyl), 2,4,6-tris(4-((E)-2-
(9-octyl-9H-carbazol-3-yl)vinyl)phenyl)-1,3,5-triazine (TRZ-octyl) and 2,4,6-tris(4-((E)-2-(9-(2-
ethylhexyl)-9H-carbazol-3-yl)vinyl)phenyl)-1,3,5-triazine (TRZ-branched). Its important key
step of this synthesis is Witting-Horner coupling reaction between carbazole aldehyde and TRZ
1
13
monomer. Those synthesized compounds were confirmed by FT-IR, H, C-NMR, and HRMS
(Fig S1- S20).
3.2. Photophysical properties
The solvatochromism effect of TRZ derivatives were examined in seven different
solvents with 1×10-5 M. The absorption, excitation and emission spectra of TRZ derivatives are
illustrated in Fig. 2, 3 (TRZ-hexyl), Fig. 4, 5 (TRZ-octyl), and Fig. 6, 7 (TRZ-branched). These
corresponding data were summarized in Table 1. From UV-visible spectra of TRZ derivatives
observed absorption (λmax) with wavelength ranging from 280 nm to 460 nm. The three
derivatives have shown very close absorption maximum at 403 nm. The solvent polarity of the
TRZ derivatives have shown negligible shift for ground state. The emission studies of TRZ
derivatives are more sensitive towards solvent polarity, its exhibit broad red-shift emission for
increasing solvents polarity. The emission shift moved in the solvent from cyclohexane to DMF
it’s quite interesting. As per emission maxima was disturbed, while increasing solvent polarity
cyclohexane to DMF solvent, a red shift of 116 nm. The TRZ derivatives shows a structured
emission in non-polar solvent like cyclohexane, whereas in all other solvents it shows moderate
to high polarity with a broad and structureless emission [35]. In the case of TRZ hexyl in
cyclohexane solvent two emission bands were observed at 434 nm and 464 nm. The 434 nm
peak assigned to emission from the local excited state of the TRZ-hexyl and the band at 464 nm
to ICT from the carbazole group to triazine moiety [36]. The three TRZ derivatives are shown a
large bathochromic shift because lack of solvent induced interactions in excited state. Generally,
donor-acceptor kind pattern molecules were attributed charge transfer induced effect.
Particularly, we have observed more stock shift respect to TRZ-hexyl in solution of ACN (FL
λemi = 550 nm, ꢀss = 6571 cm-1). Similarly, we have observed TRZ-branched blue (FL λemi = 433
nm, ꢀss = 1119 cm-1) to red shift emission with a large stokes shifts (FL λemi = 547 nm, ꢀss =
6160 cm-1). In particular, octyl containing molecules have shown more stokes shift (FL λemi
=
550 nm, ꢀss = 6819 cm-1) compare with others derivatives. These effects suggest that possibility
7

ACCEPTED MANUSCRIPT
of strong ICT interactions between carbazole donors to triazine acceptors. Moreover, the hexyl
and branched alkyl chain containing TRZ derivatives have exhibited similar behaviour, whereas
octyl chain containing carbazole acts as a donor and triazine moiety act as an acceptor with better
ICT. Further, we have investigated solid absorption and emission spectra were obtained shown in
Fig. 8 and Fig. 9. In solid UV spectra were displayed negligible difference with same absorption
pattern was observed. The solid emission maximum of TRZ-hexyl, TRZ-octyl and TRZ-
branched was observed 539, 556, and 548 nm, respectively. The emission maximum difference
of TRZ-hexyl to TRZ-octyl was observed 17 nm a red shift. The fluorescence quantum yields
(ΦF) for TRZ derivatives are 0.30, 0.31, 0.30 in chloroform solution used as a reference to
riboflavin (ΦF = 0.36 in ethanol). To understand the mechanism behind excited state properties,
we have measured fluorescence lifetime in low polar cyclohexane to high polar ACN excitation
state at 398 to 413 nm using the time-correlated single-photon-counting technique and the
obtained data’s are shown in Fig. 10, 11 and Fig. 12. The curve shows low to high polar solvents
increasing with a lifetime of two to three folds. The lifetime at maximum TRZ-hexyl, TRZ-octyl,
and TRZ-branched molecules in DMF solvent of 4.7×10-08 sec, 5.0×10-08 sec, and 1.5×10-08 sec,
respectively. The lifetime was significantly affected varying the alkyl chain length also we have
observed good lifetime in TRZ-Octyl compound for all the solvents.
a
b
Fig. 2. (a) Solvatochromism UV-visible and (b) excitation spectra of TRZ-hexyl measured in
different solvents
8

ACCEPTED MANUSCRIPT
Fig. 3. Solvatochromism emission spectra of TRZ-hexyl measured in different solvent
1.0
1.0
0.8
0.6
0.4
0.2
0.0
b
a
Cyclohexane
Toluene
0.8
0.6
0.4
0.2
0.0
CHCl
3
THF
Acetone
ACN
DMF
Cyclohexane
Toluene
THF
Acetone
ACN
DMF
350
400
450
500
300
325
350
375
400
425
450
Wavelength (nm)
Wavelength(nm)
Fig. 4. (a) Solvatochromism UV-visible and (b) excitation spectra of TRZ-octyl measured in
different solvents
Cyclo
1.0
0.8
0.6
0.4
0.2
0.0
Tolu
CHCl3
THF
Ace
ACN
DMF
Cyclohexane
Toluene
CHCl
3
THF
Acetone
ACN
DMF
450
500
550
600
650
700
Wavelength (nm)
Fig. 5. Solvatochromism emission spectra of TRZ-octyl measured in different solvent
9

ACCEPTED MANUSCRIPT
a
b
Fig. 6. (a) Solvatochromism UV-visible and (b) excitation spectra of TRZ-branched measured
in different solvents
Fig. 7. Solvatochromism emission spectra of TRZ-branched measured in different solvent
1.0
TRZ-Hexyl
TRZ-Octyl
TRZ-Branched
0.8
0.6
0.4
0.2
200
250
300
350
400
450
500
550
Wavelength (nm)
Fig. 8. Solid state UV-visible spectra of TRZ derivatives
10

ACCEPTED MANUSCRIPT
1.0
TRZ-Hexyl
TRZ-Octyl TRZ-Branched
0.8
0.6
0.4
0.2
0.0
TRZ-Hexyl
TRZ-Octyl
TRZ-Branched
500
550
600
650
700
Wavelength (nm)
Fig. 9. Solid state FL emission spectra of TRZ derivatives
10000
IRF
Cyclohexane
Toluene
CHCl
1000
100
10
3
THF
Acetone
ACN
DMF
1
20
40
60
80
100
Time (ns)
Fig. 10. Lifetime decay curve of TRZ-hexyl
10000
IRF
Cyclohexane
Toluene
CHCl
3
1000
100
10
THF
Acetone
ACN
DMF
1
20
40
60
80
Time (ns)
Fig. 11. Lifetime decay curve of TRZ-octyl
11

ACCEPTED MANUSCRIPT
10000
1000
100
10
IRF
Cyclohexane
Toluene
CHCl
3
THF
Acetone
ACN
DMF
1
20
40
60
80
100
Time (ns)
Fig. 12. Lifetime decay curve of TRZ-branched
Table 1. Photophysical properties of TRZ derivatives in different solvents
Solvents
Cyclo
-hexane 413
Toluene 398
TRZ-Hexyl
ΦF ꢀss
(cm-1) (ns) (UV) (FL)
TRZ-Octyl
TRZ-Branched
λemi ΦF ꢀss
λabs
(UV) (FL)
λemi
τ
λabs
λemi
ΦF ꢀss
τ
λabs
τ
(cm-1) (ns) (UV) (FL)
(cm-1) (ns)
393,
434, 1.00 2474
464
6.3 393,
413
2.3 399
3.1 401
434, 1.6 2379 5.6
394,
433, 0.2 1119 2.8
4133 459
458
462
504
464
504
1.07 3574
0.30 4972
0.9 3417 2.4
0.3 5096 3.0
399
403
460
503
1.5 3190
1.0
3.0
CHCl3
403
0.3 4933
1.9 4569
0.6 6087
0.1 6532
0.1 6160
THF
407
508
538
550
550
0.89 4808
0.35 6413
0.04 6571
0.10 6209
3.5 401
3.1 402
4.3 400
0.4 407
508
534
550
550
0.7 5175 3.5
0.5 6149 2.2
0.1 6819 3.3
0.1 6389 0.5
409
403
403
409
505
534
547
547
3.5
2.6
2.7
0.1
Acetone 400
ACN
DMF
404
410
3.3Aggregation Induced Emission (AIE)
All the TRZ derivatives are insoluble in water but soluble in organic solvents, we have
observed that THF/H2O fractions significantly effect of UV-vis and emission intensity. In UV-
vis spectra had shown increasing percentage of water fraction as well as slowly increase the FL
emission intensity also with a small red shift. Fig. 13-15 has shown emission spectra of TRZ-
octyl, TRZ-branched in different percentage of THF/H2O mixtures. Emission spectra had shown
when added a large amount of water in THF solution absorption gradually increases reached
maxima absorption of TRZ-hexyl at 10/90%, TRZ-octyl at 30/70%, TRZ-branched at 50/50%
12

ACCEPTED MANUSCRIPT
(THF/H2O) respectively. The fluorescence emission spectra of TRZ derivatives in the THF/H2O
different mixtures of water content are shown in Fig. 13. The triazine derivatives are shown good
AIE property due to the retraction of intramolecular rotations. The THF solvent used as organic
phase, as THF slowly evaporates the triazine derivatives are transferred into aqueous phase with
the formation of nanoparticle via aggregation of triazine molecules. The TRZ-hexyl FL spectra
had showed emission at 510 nm, when excitation have performed at 407 nm. The addition of
water ration into TRZ-hexyl in THF solution, the FL emission intensity was significantly
increased with a slight red-shift, with colour change from green (0% H2O) to yellow (90% H2O)
and then maximum intensity was observed at 90% H2O. Depending upon increased the water
ratio, TRZ-hexyl has shown linear plot with 3.34-fold increases of emission intensity at 514 nm.
Another reason for why we could believe aqueous media restricted intramolecular rotation
because of the formation of nano-aggregates and the number of emissive molecules per unit
volume also decreased. In case of TRZ-octyl compound maximum emission intensity was
observed for 70% H2O. Further addition of water higher than 70%, the emission intensity was
decreased, due to the low solubility of the compound. The water fraction of 70% has shown 6 nm
a red shift or higher intensities at 268 nm with a 2.85-fold increases. The colour changes with a
change in water volume were from green (0% water) to greenish yellow (70% water). Similarly,
the TRZ-branched molecule has shown maximum emission intensity at 50% H2O ratio with 13
nm a red shift emission of 5.31-fold increases. The increase water ratio into TRZ-branched the
emission intensity was moderated increase at 10%, 20% H2O ratio. The 30%, 40% H2O water the
emission intensity was sudden increases observed and the maximum was reached at 50% H2O
ratio. The alkyl chain length hexyl, 2-ethyl hexyl to octyl the peak emission intensity increases of
AIE state 3.34, 5.32, and 2.85 folds respectively. These are recognised to the fact that a long
alkyl chain hinders intermolecular tight stacking. In the different number of alkyl chains are
controlling the nature of the molecular packing and fluorescence properties. Branched alkyl side
chains have shown more AIE properties compared with linear alkyl side chains due to the more
π-π stacking and fusible packing capability. The AIE properties are mainly alkyl length-
dependent fluorescence properties, those conjugated molecules with twisted backbone
conformations and these molecules usually have shown aggregation-induced emission (AIE) and
the mechano-chromic luminescence phenomenon [37,38].
13

ACCEPTED MANUSCRIPT
TRZ-Hexyl
500
400
300
200
100
a
b
0
20
40
60
80
Water fraction (vol %)
Fig. 13. (a) Emission spectra of TRZ-hexyl in aqueous THF with different water ratios and (b)
FL intensity of TRZ-hexyl with different water fractions mixture
a
280
Octyl-TRZ
b
240
200
160
120
80
0
20
40
60
80
Water fraction (vol%)
Fig.14. (a) Emission spectra of TRZ-octyl in aqueous THF with different water ratios and (b) FL
intensity of TRZ-octyl with different water fractions mixture
14

ACCEPTED MANUSCRIPT
700
600
500
400
300
200
100
0
40%
50%
0%
10%
20%
30%
a
700
600
500
400
300
200
100
Branched -TRZ
0% H
O
2
10% H
20% H
30% H
40% H
50% H
60% H
70% H
80% H
90% H
O
2
2
2
2
2
2
2
2
2
O
O
O
O
O
O
O
O
b
450
500
550
600
650
700
0
20
40
60
80
Wavelength (nm)
Water fraction (vol%)
Fig. 15. (a) Emission spectra of TRZ-branched in aqueous THF with different water ratios and
(b) FL intensity of TRZ-branched with different water fractions mixture
In additional, solvatochromism effect of the molecules correlated with Stokes shift
against Lippert–Mataga and Reichardt–Dimorth’s ET(30) parameters are shown in Fig. 16, 17
[30,39]. The TRZ derivatives displayed reasonable linear relationship demonstrating the
presence of general solvent effects. Furthermore, these TRZ derivatives are showed moderate
quantum yield in non-polar solvent as cyclohexane to polar ACN. It was significantly increased
by the increasing solvent polarity.
TRZ- Hexyl
7000
TRZ-Octyl
TRZ-Branched
6000
5000
4000
3000
2000
1000
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Orientation polarizability
Fig. 16. Lippert-Mataga plot of TRZ derivatives
15

ACCEPTED MANUSCRIPT
TRZ-Hexyl
TRZ-Octyl
7000
TRZ-Branched
6000
5000
4000
3000
2000
1000
32
36
E
40
44
(30) (Kcal/mol)
T
Fig. 17. Plot of ET (30) Vs Stokes shift of TRZ derivatives
3.4 DFT calculation
In theoretical studies of the density functional theoretical (DFT) study, further
identification of geometry of these molecules and photophysical studies. The obtained geometry
of HOMO and LUMO of the TRZ derivatives are shown in Fig. 18. In the carbazole moiety a
large contribution in HOMO energy level due to the electron-donating property. Whereas the
LUMO energy levels mainly focused on the triazine core, and then slight contribution from the
double bond linkage. Further, it is interesting to note that the molecules look like star shape due
to their contribution of all the molecules. The HOMO and LUMO energy levels are -4.97 eV and
-1.79 eV, respectively. The HOMO and LUMO energy level of TRZ derivatives displayed
almost identical.
Fig. 18. Density functional theory calculation of LUMO and HOMO energy level diagram of
TRZ derivatives
16

ACCEPTED MANUSCRIPT
3.5 Electrochemical properties
The electrochemical properties of the TRZ derivatives were investigated using cyclic
voltammetry using DCM solutions at 100 mV/s scan rate. The obtain CV spectra are shown in
Fig. 19, and corresponding data’s are summarized in Table 2. The onset oxidation potential was
observed in the range of 1.35, 1.20 eV, and 1.43 eV for TRZ-hexyl, TRZ-octyl, and TRZ-
branched, respectively. From these onset value, we have calculated the HOMO energy levels of -
5.48, -5.33 eV, and -5.48 eV for TRZ-hexyl, TRZ-octyl and TRZ-branched respectively. The
onset reduction potential and LUMO were observed almost similar ~ -0.52 eV and ~ -3.61 eV for
TRZ derivatives. The band gap of TRZ-hexyl, TRZ-octyl, and TRZ-branched molecules are
1.87, 1.73 eV, and 1.86 eV respectively. Among these three molecules, octyl chain containing
molecule shows low HOMO and low band gap due to their side-chain interference and self-
assembly of the molecular packing [33]. It suggested that the synthesized TRZ derivatives are
good donor materials for organic solar cell applications [23,24].
HOMO and LUMO energy levels are calculated by following equations
onset
onset
HOMO= -eV (Eox
- E1/2ferrocene + 4.4); LUMO= -eV (Ered
- E1/2ferrocene + 4.4)
TRZ-Hexyl
TRZ-Octyl
0.00004
TRZ-Branched
0.00002
0.00000
-0.00002
-0.00004
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Voltage (V)
Fig. 19. Cyclic voltammograms of TRZ derivatives in DCM at a scan rate of 100 mV s-1
Table 2. Optical and electrochemical properties of TRZ derivatives
Sample
Optical properties (thin film)
UV (nm)
Electro chemical data (CV)
PL (nm) ꢀss (cm-1) Eoxonset / HOMO Eredonset /LUMO
Band gap
(eV)
(eV)
(eV)
-0.52/ -3.21
TRZ-Hexyl
TRZ-Octyl
406
401
406
540
554
550
6112
6887
6449
1.30/ -5.08
1.87
1.20/ -4.93
1.43/ -5.08
-0.53/ -3.20
-0.52/ -3.21
1.73
1.86
TRZ-
Branched
17

ACCEPTED MANUSCRIPT
3.6 Morphology studies
The morphology of TRZ derivatives was analysed by Atomic force microscopy (AFM)
and the obtained images are shown in Fig. 20. All the molecules are showed a smooth surface,
which reveals that the molecule can easily make a good surface in the film. Furthermore, the
molecules are investigated by scanning electron microscopy (SEM) and the images are shown in
Fig. 21, 22, and 23 with and without water fractions respectively. The sample was prepared by
using ITO coated plated. The SEM images of TRZ derivatives are shown different structures
such as cactaceae chapati kalli (TRZ-hexyl), rocky mountain (TRZ-octyl) star shape (TRZ-
branched) like structure morphology particle are agglomerate, after the presence of water show
spherical structures for all the TRZ derivatives. This is due to the presence of molecules are
absorption water to form mechanism.
b
c
a
Fig. 20. (a) AFM images of TRZ-hexyl, (b) TRZ-octyl and (c) TRZ-branched
b
a
Fig. 21. (a) SEM image of TRZ-hexyl and (b) TRZ-hexyl + H2O
18

ACCEPTED MANUSCRIPT
a
b
Fig. 22. (a) SEM image of TRZ-octyl and (b) TRZ-octyl + H2O
b
a
Fig. 23. (a) SEM image of TRZ-branched and (b) TRZ-branched + H2O
3. Conclusions
The novel three star shaped molecules containing triazine centre has been designed,
synthesized, studied for fluorescence and AIE studies. The TRZ derivatives are displayed high
optical properties in excitation states compare to ground. The emission spectra show large extent
emission of non-polar to polar solvents in the range of 432 to 549 nm with high quantum yields.
The DFT and the electrochemical band gap of TRZ derivatives showed ~1.80 eV suggested that
good solar cell materials. The TRZ derivatives in organic solvents displayed less emission
compared to aggregation state. The introduction of different side chains can enrich the flexibility
of molecules, but not much difference in optical properties and electrochemical behaviour. The
obtain results communicate that the presence of triazine with carbazole molecules showed
efficient fluorescence and AIE properties and also provide useful information for the further
design of OLEDs and solar cell materials.
19

ACCEPTED MANUSCRIPT
Acknowledgements
The authors are thankful to VIT University for providing laboratory facilities and VIT SIF for
the spectral studies. The authors thank the DST for the financial support of this work through the
SERB research grant (SERB-SB/FT/CS-185/2011) and Solar Energy Research Initiative (SERI)
Programme (DST/TM/SERI/FR/172(G)).
References
1. Li Y, Molecular design of photovoltaic materials for polymer solar cells: toward suitable
electronic energy levels and broad absorption. Acc Chem Res 2012;45:723-33.
2. Sakthivel P, Song H-S, Chakravarthi N, Lee J-W, Gal Y-S, Hwang S, Jin S-H, Synthesis
and characterization of new indeno [1,2-b] indole-co-benzothiadiazole-based π-
conjugated ladder type polymers for bulk heterojunction polymer solar cells. Polym
2013;54:4883-93.
3. Yang X, Zhou G, Wong W-Y, Functionalization of phosphorescent emitters and their
host materials by main-group elements for phosphorescent organic light-emitting devices.
Chem Soc Rev 2015;44:8484-757.
4. Sasaki S, Drummen G-P, Konishi G-I, Recent advances in twisted intramolecular charge
transfer (TICT) fluorescence and related phenomena in materials chemistry. J Mater
Chem C 2016: 4:2731-43.
5. Reddy S-S, Gunasekar K. Heo J-H, Im S-H, Kim C-S, Kim D-H, Moon J-H, Lee J-Y,
Song M, Jin S-H. Highly efficient organic hole transporting materials for perovskite and
organic solar cells with long‐term stability. Adv Mater 2016;28: 686-693.
6. Chen H-F, Yang S-J, Tsai Z-H, Hung W-Y, Wang T-C, Wong K-T, 1,3,5-Triazine
derivatives as new electron transportp-type host materials for highly efficient green
phosphorescent OLEDs. J Mater Chem 2009;19:8112-18.
7. Blotny G, Recent applications of 2,4,6-trichloro-1,3,5-triazine and its derivatives in
organic synthesis. Tetrahedron 2006;62:9507-9522.
8. Chakravarthi N, Gunasekar K, Cho W, Long D-X, Kim Y-H, Song C-E, Lee J-C,
Facchetti A, Song M, Noh Y, Jin S-H, A simple structured and efficient triazine-based
molecule as an interfacial layer for high performance organic electronics. Energy Environ
Sci 2016:9;2595-2602.
9. Reddy S-S, Sree V-G, Gunasekar K, Cho W, Gal Y-S, Song M, Jin S-H, Highly efficient
bipolar deep‐blue fluorescent emitters for solution‐processed non‐doped organic light‐
emitting diodes based on 9,9‐dimethyl‐9,10‐dihydroacridine/phenanthroimadazole
derivatives. Adv Opt Mater 2016;4: 1236-1246.
10. Reddy S-S, Cho W, Sree V-G, Jin S-H, Multi-functional highly efficient bipolar 9,9-
dimethyl-9,10-dihydroacridine/imidazole-based materials for solution-processed organic
light-emitting diode applications. Dyes Pigm 2016;134: 315-324.
20

ACCEPTED MANUSCRIPT
11. Jeong H, Shin H, Lee J, Kim B, Park Y-I, Yook K-S, An B-K, Park J, Recent progress in
the use of fluorescent and phosphorescent organic compounds for organic light-emitting
diode lighting. J Photon Energy 2015;5:057608-057608.
12. Chen T, Zheng L, Yuan J, An Z, Chen R, Tao Y, Li H, Xie X, Huang W, Understanding
the Control of Singlet-Triplet Splitting for Organic Exciton Manipulating: A Combined
Theoretical and Experimental Approach. Sci Rep 2015;5:10923.
13. Liu X-K, Zheng C-J, Xiao J, Ye J, Liu C-L, Wang S-D, Zhao W-M, Zhang X-H, Novel
bipolar host materials based on 1,3,5-triazine derivatives for highly efficient
phosphorescent OLEDs with extremely low efficiency roll-off. Phys Chem Chem Phys
2012;14:14255-14261.
14. Reddy S-S, Sree V-G, Cho W, Jin S-H, Achieving pure deep‐blue electroluminescence
with CIE y≤ 0.06 via a rational design approach for highly efficient non‐doped solution‐
processed organic light‐emitting diodes. Chem Asian J 2016;11: 3275-3282.
15. Banerjee T, Kar D, Krishna P-R, Prabhakar S, Nomula R, Mallula V-S, Ravindranath H,
Sridhar G, Adepu R, Srikanth G, Mabalirajan U, A novel triazine-aryl-bis-indole
derivative inhibits both phosphodiesterase IV and expression of cell adhesion molecules.
RSC Adv 2015;5:70271-70281.
16. Chen D, Su S-J, Cao Y, Nitrogen heterocycle-containing materials for highly efficient
phosphorescent OLEDs with low operating voltage. J Mater Chem C 2014;2:9565.
17. Nakanotani H, Masui K, Nishide J, Shibata T, Adachi C, Promising operational stability
of high-efficiency organic light-emitting diodes based on thermally activated delayed
fluorescence. Sci Rep 2013;3:2127.
18. Adachi C., Third-generation organic electroluminescence materials. Jpn J Appl Phys
2014;53:060101.
19. Hung W-Y, Fang G-C, Lin S-W, Cheng S-H, Wong K-T, Kuo T-Y, Chou P-T, The first
tandem, all-exciplex-based WOLED. Sci Rep 2014;4:5161.
20. Jiang Y, Wang Y, Hua J, Tang J, Li B, Qian S, Tian H, Multibranched triarylamine end-
capped triazines with aggregation-induced emission and large two-photon absorption
cross-sections.Chem Commun 2010;46:4689.
21. Kukhta N-A, Simokaitiene J, Volyniuk D, Ostrauskaite J, Grazulevicius J-V, Juska G,
Jankauskas V, Effect of linking topology on the properties of star-shaped derivatives of
triazine and fluorene. Synth Met 2014;195:266-275.
22. Sathiyan G, Thangamuthu R, Sakthivel P, Synthesis of carbazole-based copolymers
containing carbazole-thiazolo[5,4-d]thiazole groups with different dopants and their
fluorescence and electrical conductivity applications. RSC Adv 2016;6:69196-69205.
23. Sakthivel P, Ban T-W, Kim S, Kim S, Gal Y-S, Chae E-A, Shin W-S, Moon S-J, Lee J-C,
Jin S-H, Synthesis and studies of methyl ester substituted thieno-o-quinodimethane
fullerene multiadducts for polymer solar cells.Sol Energ Mat Sol Cells 2013;113:13-19.
21

ACCEPTED MANUSCRIPT
24. Sathiyan G, Sivakumar E-K-T, Ganesamoorthy R, Thangamuthu R, Sakthivel P, Review
of carbazole based conjugated molecules for highly efficient organic solar cell
application. Tetrahedron Lett 2016;57:243-252.
25. Xue S, Qiu X, Sun Q, Yang W, Alkyl length effects on solid-state fluorescence and
mechanochromic behavior of small organic luminophores. J Mater Chem C 2016;4:1568-
1578.
26. Li Y, Zou J, Yip H-L, Li C-Z, Zhang Y, Chueh C-C, Intemann J, Xu Y, Liang P-W,
Chen Y, Jen A-K-Y, Side-chain effect on cyclopentadithiophene/fluorobenzothiadiazole-
based low band gap polymers and their applications for polymer solar cells.
Macromolecules 2013;46:5497.
27. Balakrishnan K, Datar A, Naddo T, Huang J, Oitker R, Yen M, Zhao J, Zang L, Effect of
side-chain substituents on self-assembly of perylene diimide molecules:morphology
control. J Am Chem Soc 2006;128:7390-7398.
28. Balasaravanan R, Duraimurugan K, Sivamani J, Thiagarajan V, Siva A, Synthesis and
photophysical properties of triphenylamine-based multiply conjugated star-like
molecules. New J Chem 2015; 39:7472-7480.
29. Hua B, Gao Y, Ying S, Liu W, Xue S, Yang W, Synthesis and optoelectronic properties
of a solution-processed red-emitting tetra (arylvinyl) anthracene cruciform. Dyes Pigm
2015;123:26-31.
30. Konidena R-K, Thomas K-J, Singh M, Jou J-H, Thienyl phenothiazine integrated
pyrenes: an account on the influence of substitution patterns on their optical and
electroluminescence properties. J Mater Chem C 2016;4:4246-4258.
31. Matulaitis T, Kostiv N, Grazulevicius J-V, Peciulyte L, Simokaitiene J, Jankauskas V,
Luszczynska B, Ulanski J, Synthesis and properties of bipolar derivatives of 1, 3, 5-
triazine and carbazole. Dyes Pigm 2016;127:45-58.
32. Reghu R-R, Grazulevicius J-V, Simokaitiene J, Matulaitis T, Miasojedovas A,
Kazlauskas K, Jursenas S, Data P, Lapkowski M, Zassowski P, Glass forming donor-
substituted s-triazines: photophysical and electrochemical properties. Dyes Pigm
2013;97:412-422.
33. Sathiyan G, Sakthivel P, A multibranched carbazole linked triazine based fluorescent
molecule for the selective detection of picric acid. RSC Adv 2016;6:106705-106715.
34. Taddei M, Costantino F, Marmottini F, Comotti A, Sozzani P, Vivani R, The first route
to highly stable crystalline microporous zirconium phosphonate metal-organic
frameworks. Chem Commun 2014;50:14831-14834.
35. Subuddhi U, Haldar S, Sankararaman S, Mishra A-K, Photophysical behaviour of 1-(4-N,
N-dimethylaminophenylethynyl) pyrene (DMAPEPy) in homogeneous media.
Photochem Photobiol Sci 2006;5:459-466.
36. Nandy R, Sankararaman S, Donor-acceptor substituted phenylethynyltriphenylenes–
excited state intramolecular charge transfer, solvatochromic absorption and fluorescence
emission. Beilstein J Org Chem 2010;6:992-1001.
22

ACCEPTED MANUSCRIPT
37. Lasitha P, Prasad E, Orange red emitting naphthalene diimide derivative containing
dendritic wedges: aggregation induced emission (AIE) and detection of picric acid (PA).
RSC Adv 2015;5:41420-41427.
38. Vij V, Bhalla V, Kumar M, Attogram detection of picric acid by hexa-peri-
hexabenzocoronene-based chemosensors by controlled aggregation-induced emission
enhancement. ACS Appl Mater Interfaces 2013;5:5373-5380.
39. Goel A, Kumar V, Singh S-P, Sharma A, Prakash S, Singh C, Anand R-S, Non-
aggregating Solvatochromic Bipolar Benzo[f]quinolines and Benzo[a]acridines for
Organic Electronics. J Mater Chem 2012;30:14880-14888.
23

ACCEPTED MANUSCRIPT
Justification
•
•
•
•
Three novel star shaped molecules have been designed, synthesized, studied for
fluorescence and AIE studies.
The synthesized molecules are displayed high optical properties in excitation states
compare to ground state.
The electrochemical band gap of TRZ derivatives showed ~1.80 eV suggested that good
donor materials for organic solar cell materials.
The presence of different side chains can enrich the flexibility of molecules. These results
conclude the molecules provided useful information for the further design of OLEDs and
solar cell materials.