4′-Phenyl-2,2′:6′,2″-terpyridine derivatives-synthesis, potential application and the influence of acetylene linker on their properties

Article abstract of DOI:10.1016/j.dyepig.2017.07.030

Novel derivatives of 4'-phenyl-2,2':6′,2″-terpyridine (tpy) with ethynyl (T1), 2-ethynyl-9,9-dioctylfluorene (T2), 9,9-dioctylfluorene (T3), 9-ethynyl-10-decyloxyanthracene (T4) substituents were obtained via Sonogashira or Suzuki-Miyaura coupling reactions, respectively, and thoroughly characterized. The presence of ethynyl bridge impacts photophysical properties of novel compounds by shifting absorption and emission spectra towards longer wavelengths as compared to T3, where fluorene is connected with tpy via a single bond. TGA measurements showed that among the new terpyridines those obtained as solids exhibited high thermal stability as opposed to those which were oils (tpy containing fluorene motif). Due to the fact that high thermal stability of 4'-phenyl-2,2':6′,2″-terpyridine derivatives showed photoluminescence (PL) quantum yield (Φ) in the range of 27–84% in solution, their electroluminescence ability was tested in diodes with guest-host configuration. For the compounds dispersed in a matrix consisting of poly(9-vinylcarbazole) (PVK) (50 wt %) and (2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole) (PBD) (50 wt %) radiation with maxima between 374 and 531 nm and characterized with Φ in the range of 8–12% was observed. They exhibited green or violet electroluminescence. The results confirmed the substantial role of aryl groups and the linker in the presented terpyridines in terms of their thermal, electrochemical, optical and electroluminescence properties. In addition, density functional theory (DFT) and time-dependent-density functional theory (TD-DFT) calculations were performed to provide an independent support and deeper insight into the experimental results.

Full text of DOI:10.1016/j.dyepig.2017.07.030

Accepted Manuscript
4′-phenyl-2,2':6′,2″-terpyridine derivatives-synthesis, potential application and the
influence of acetylene linker on their properties
Dawid Zych, Aneta Słodek, Marek Matussek, Michał Filapek, Grażyna Szafraniec-
Gorol, Sławomir Maślanka, Stanisław Krompiec, Sonia Kotowicz, Ewa Schab-
Balcerzak, Karolina Smolarek, Sebastian Maćkowski, Marian Olejnik, Witold
Danikiewicz
PII:
S0143-7208(17)31108-7
10.1016/j.dyepig.2017.07.030
DYPI 6119
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 12 May 2017
Revised Date: 15 June 2017
Accepted Date: 14 July 2017
Please cite this article as: Zych D, Słodek A, Matussek M, Filapek Michał, Szafraniec-Gorol Graż,
Maślanka Sł, Krompiec Stanisł, Kotowicz S, Schab-Balcerzak E, Smolarek K, Maćkowski S, Olejnik
M, Danikiewicz W, 4′-phenyl-2,2':6′,2″-terpyridine derivatives-synthesis, potential application and
the influence of acetylene linker on their properties, Dyes and Pigments (2017), doi: 10.1016/
j.dyepig.2017.07.030.
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4'-Phenyl-2,2':6',2''-terpyridine derivatives - synthesis, potential application and the
influence of acetylene linker on their properties
[a]*
[a]
[a]
[a]
Dawid Zych , Aneta Słodek , Marek Matussek , Michał Filapek , Grażyna
[a]
[a]
[a]
[a]
Szafraniec-Gorol , Sławomir Maślanka , Stanisław Krompiec , Sonia Kotowicz ,
[a][b]
[c]
[c]
Ewa Schab-Balcerzak
, Karolina Smolarek , Sebastian Maćkowski , Marian
[d]
[d]
Olejnik , Witold Danikiewicz
[a] Institute of Chemistry, Faculty of Mathematics, Physics and Chemistry,
University of Silesia, Szkolna 9, 40-007 Katowice, Poland
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[b] Centre of Polymer and Carbon Materials, Polish Academy of Sciences,
M. Curie-Sklodowska 34, 41-819 Zabrze, Poland
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[c] Institute of Physics, Faculty of Physics, Astronomy and Informatics,
Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun, Poland
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[d] Institute of Organic Chemistry, Polish Academy of Sciences,
Kasprzaka 44/52, 01-224 Warszawa 42, Poland
*Corresponding Author: dawidzych92@gmail.com (Dawid Zych)

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Highlights:
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Novel and well-soluble derivatives of 4'-phenyl-2,2':6',2''-terpyridine were obtained
The influence of acetylene linker on thermal, electrochemical, optical and
electroluminescence properties was examined
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Efficient luminophores with high photoluminescence (PL) and quantum yields (Φ)
OLEDs devices containing T1 and T4 as emitters showed green to orange
electroluminescence

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Abstract
Novel derivatives of 4'-phenyl-2,2':6',2''-terpyridine (tpy) with ethynyl (T1), 2-ethynyl-9,9-
dioctylfluorene (T2), 9,9-dioctylfluorene (T3), 9-ethynyl-10-decyloxyanthracene (T4)
substituents were obtained via Sonogashira or Suzuki-Miyaura coupling reactions,
respectively, and thoroughly characterized. The presence of ethynyl bridge impacts
photophysical properties of novel compounds by shifting absorption and emission spectra
towards longer wavelengths as compared to T3, where fluorene is connected with tpy via a
single bond. TGA measurements showed that among the new terpyridines those obtained as
solids exhibited high thermal stability as opposed to those which were oils (tpy containing
fluorene motif). Due to the fact that high thermal stability of 4'-phenyl-2,2':6',2''-terpyridine
derivatives showed photoluminescence (PL) quantum yield (Φ) in the range of 27 - 84% in
solution, their electroluminescence ability was tested in diodes with guest-host configuration.
For the ccompounds dispersed in a matrix consisting of poly(9-vinylcarbazole) (PVK) (50 wt
%) and (2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole) (PBD) (50 wt %) radiation with
maxima between 374 to 531 nm and characterized with Φ in the range of 8 - 12% was
observed. They exhibited green or violet electroluminescence. The results confirmed
substantial role of aryl groups and the linker in the presented terpyridines in terms of their
thermal, electrochemical, optical and electroluminescence properties. In addition, density
functional theory (DFT) and time-dependent-density functional theory (TD-DFT)
calculations were performed to provide an independent support and deeper insight into the
experimental results.
Key words: Terpyridines, Organic electronics, Luminescence, DFT study, Fluorene,
Anthracene

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1. Introduction
For almost ninety years many derivatives of 2,2':6',2''-terpyridine (tpy) functionalized
at different positions have been synthesised [1-3] and these efforts were mainly driven by
their distinguished photophysical and electrochemical properties [4-6]. In particular, tpy
derivatives due to their high binding affinity toward transition-metal (tridentate ligand
feature), π-stacking ability, directed H-bond formation and synthetic accessibility have
become frequently used units in material chemistry research related to organic electronics,
medicine, catalysis and optoelectronics [6-11].
Simple 2,2':6',2''-terpyridine derivatives can be synthesised based on the Kröhnke reaction,
which is a one-pot reaction using commercially available materials in simple medium [12,
13]. Products obtained in this way can be used in other reactions, i.e. coupling reaction,
which allows to obtain materials with desired photophysical properties. Derivatives of 4'-
phenyl-2,2':6',2''-terpyridine can be obtained in Suzuki-Miyaura cross-coupling reaction from
appropriate precursors. 4'-(4-Ethynylphenyl)-2,2':6',2''-terpyridine and its derivatives can be
synthesised in Sonogashira cross-coupling reaction [14, 15].
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The differences between 4'-phenyl-2,2':6',2''-terpyridine and 4'-(4-ethynylphenyl)-2,2':6',2''-
terpyridine with the same substituent was studied by Guowei Gao et al. based on corannulene
motif [16]. They showed that compound with acetylene linker exhibits a bathochromic shift
of absorption spectrum and higher fluorescence quantum yield in comparison to compound
with substituent connected directly to phenyl. Furthermore, triple bond enhances the
conjugation of the molecule and enables more efficient energy transfer.
In the literature there are described 4'-phenyl-2,2':6',2''-terpyridine derivatives with ethynyl
[17-19], 9,9-dihexylfluorene, [15] and 2-ethynyl-9,9-dihexylfluorene [15, 20] substituents,
but results are focused primarily on the synthesis of these compounds, while either
photophysical or electrochemical properties as well as in silico investigations are rarely
discussed. A series of bis(terpyridine) isomers referred to 2-TerPyB, 3-TerPyB, and 4-
TerPyB was investigated and studied as electron-transport materials in OLEDs with
-2
extremely low operating voltage of 2.2 V at a luminance of 1 cd m [21].
Terpyridine/diphenylamine derivatives used as blue fluorescent emitters and red
phosphorescent hosts in OLEDs provided the maximum external quantum efficiency (EQE)
of 4.9% in non-doped blue fluorescent OLEDs and as host materials in red phosphorescent
OLEDs exhibited maximum EQE of 20.9% [22].
To the best of our knowledge, 4'-(4-ethynylphenyl)-2,2':6',2''-terpyridines with anthracene
motif have not been described.

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Herein, we described the synthesis of 4'-phenyl-2,2':6',2''-terpyridine with ethynyl (T1), 9,9-
dioctylfluorene (T2), 2-ethynyl-9,9-dioctylfluorene (T3), 10-decyloxyanthracene (T4)
substituents. The synthesis effort have been complemented by detailed spectroscopic,
photophysical, theoretical and electrochemical studies with compounds T1 and T4 being
tested in diodes with guest-host configuration.
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Figure 1. Structure of 4'-phenyl-2,2':6',2''-terpyridine derivatives T1-T4.
2. Results and discussion
2.1.
Synthesis and structural characterization
The structure of designed 4'-phenyl-2,2':6',2''-terpyridine derivatives T1-T4 is presented in
Figure 1. Scheme 1 shows the synthesis route to 4'-(4-ethynylphenyl)-2,2':6',2''-terpyridine
(T1) and intermediate 4′-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-2,2′,6′,2″-
terpyridine (2). The first step was conducted based on the well-known procedures from
commercially available 4-bromobenzaldehyde and 2-acetylpyridine in Kröhnke reaction,
which resulted in 4'-(4-bromophenyl)-2,2':6',2''-terpyridine [23]. The Sonogashira cross-
coupling reaction of 1 with trimethylsilylacetylene (TMSA) catalyzed by [Pd(PPh ) ] gave 4'-
3
4
(4-ethynylphenyl)-2,2':6',2''-terpyridine (T1) with 92% yield [24]. Boronate ester 2 was
obtained in the Suzuki-Miyaura coupling reaction between 1 and bis(pinacolato)diboron with

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catalyst [Pd(pddf) Cl ] with 33% yield [25, 26]. The routes of synthesis of aryl intermediates
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2
are presented in Scheme 2. Iodoarene 4 was obtained from commercially available fluorene
upon iodination followed by alkylation under phase-transfer catalysis (PTC) conditions to
afford 2-iodo-9,9-dioctylfluorene (4) with 79% yield [27, 28]. Intermediate 6 was obtained
from commercially available anthrone in alkylation reaction followed by bromination
resulting in 9-bromo-10-decyloxyanthracene with 26% yield.
The target 4'-(4-ethynylphenyl)-2,2':6',2''-terpyridine derivatives T2 and T4 were obtained in
[Pd]/[Cu]-catalyzed Sonogashira cross-coupling reaction with respective haloaromatics 4 or 6
(Scheme 3). The desired 4'-phenyl-2,2':6',2''-terpyridine derivative T3 was obtained in [Pd]-
catalyzed Suzuki-Miyaura cross-coupling reaction with iodoarene 4. The yields of conducted
reactions were in the range of 26 - 92%. The compounds T1 and T4 were obtained as solids
(T1 - beige, T4 - orange), compounds T2 and T3 were obtained as oils (T2 - dark yellow, T3
- yellow-orange).
1
The novel compounds T1-T4 were fully characterized by standard spectroscopic methods H
1
3
and C NMR and mass spectrometry. In addition, all the resulting compounds are perfectly
soluble in organic solvents such as dichloromethane, chloroform, acetone, tetrahydrofuran,
ethyl acetate, what allows to easy purification and characterization. Moreover, they are easy
to handle, what is important for device preparation.

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H
N
N
N
Br
CH
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T1 (Y = 92%)
b, c
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H C
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O
d
CH
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(Y = 42%)
Br
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(Y = 33%)
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Scheme 1. Synthesis route of compounds 1, 2, and T1. Reagents and conditions: a) KOH,
NH3 aq, EtOH, room temp., 24 h; b) TMSA, [Pd(PPh ) ], CuI, NEt , reflux, 16 h; c) KF, THF,
3 4
3
MeOH, room temp., 24 h; d) bis(pinacolato)diboron, [PdCl (dppf)], KOAc, DMSO, 80 °C,
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OC10H21
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6 (Y = 26%)
1
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Scheme 2. Synthesis routes of compounds 3-6. Reagents and conditions: a) I , H IO ,
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AcOH/H O/H SO , 70 °C, 6 h; b) 50% NaOH , TBAB, n-C H Br, DMSO, room temp.,
2
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4
(aq)
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12 h; c) n-C H Br; TBAI, KOH, H O, toluene, rf, 5 h; d) NBS, DMF, room temp., 12 h.
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8 17
H17C8
[
Pd(PPh ) ], CuI
T2 (Y = 60%)
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THF, NEt , 78 °C
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H21C10
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Scheme 3. Synthetic routes for the preparation of T2-T4.
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2.2.
Thermal properties
The thermal stability of the prepared 4'-phenyl-2,2':6',2''-terpyridine derivatives was
evaluated using thermogravimetric analysis (TGA) under nitrogen atmosphere and the
obtained data are presented in Table 1, whereas Figure 2 depicts representative TGA and
DTG thermograms of compounds T2 and T4.

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Table 1. Thermal stability of T1-T4 compounds.
TGA
Code
Char residue
at 900 °C [%]
T [°C]
d
Tmax [°C]
T1
T2
T3
T4
309
137
145
286
307, 441, 565, 638, 734
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460
468, 507
348, 394
T – temperature of 5% weight loss, T – the maximum decomposition
d
max
rate from DTG thermograms.
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Figure 2. TGA with DTG curves of T2 (a) and T4 (b).
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The TGA curves showed that the beginning of decomposition (T ), which corresponds to the
d
temperature of 5% sample weight loss during heating, was the highest for T1 and T4.
Introduction of fluorene unit to tpy frame (T2 and T3) significantly lowered T . The
d
presence of acetylene bond provided higher amount of the char residue. It was found that
compound T1 possessing only the ethylene substituent has better thermal stability than other
compounds. DTG curves revealed that compounds with fluorene derivative exhibit one (for
T2) and two (for T3) weight-loss peaks. The presence of acetylene linker has minimal impact
on the thermal stability. In the case of T4 the weight-loss peak with two maxima was
registered. Additionally, for compounds which were in a solid state, that is T1 and T4, the
differential scanning calorimetry (DSC) measurements were carried out. The first heating
scan of T1 revealed two endotherms with maximum at 129 and 175 °C. DSC thermogram
registered at second heating run after rapid cooling showed only glass transition temperature
(T ) at 62 °C. During further heating of T1 above 175 °C at first heating run the exotherme
g
was seen with a maximum at 198 °C. 4'-Phenyl-2,2':6',2''-terpyridine derivative denoted as
T4 was also molecular glass with T at 33 °C obtained in second heating DSC scan. Further
g

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heating above T revealed crystallization and melting peaks at 143 and 157 °C, respectively.
g
The first heating of T4 yields crystallization and melting peaks at 87 and 156 °C, typical of a
monophase crystalline solid.
2.3.
DFT studies
To gain useful information about the geometry and optical properties of obtained terpyridines
T1-T4 the density functional theory (DFT) and time-dependent-density functional theory
(TD-DFT) calculations were performed. The B3LYP exchange-correlation functional with 6-
31G** basis set, as implemented in the Gaussian 09 program, was employed [29]. The
B3LYP/6-31G** geometries were optimized in dichloromethane solution in the polarisable
continuous model (PCM), structures for T1-T4 are presented in Table 2. It can be seen that
the connecting phenyl ring and the central pyridine ring are twisted by about 35º with respect
to each other. The substituents connected via triple bond in T2 and T4 are in coplanar
position to phenyl ring, while in T3 the fluorene motif is twisted by about 35º. One can see
that acetylene linkage improves the planarity of the substituents. The geometry affects the
photophysical properties, for instance, the T2 compound due to its coplanarity shows higher
quantum yield in comparison to the compound with substituent connected direct to phenyl
T3. The triple bond causes the faster and more efficient energy transfer.
Electrostatic potential energy maps for T1-T4 are showed in Figure S10 (Supporting
Information), they illustrate three-dimensional charge distributions of molecules. It
determines mutual interactions between molecules, but also – which is important in our case -
it confirms the tridentate ligands feature.
A schematic representation of the frontier molecular orbitals and the energy gaps (∆E)
between the highest occupied molecular orbital (HOMO) and the lowest unoccupied
molecular orbital (LUMO) for described compounds is presented in Figure 3. The value of
∆E for T1-T4 is respectively 4.60, 3.63, 3.98, and 2.79 eV.
In the case of T2 and T4 the electrons in the HOMO are mainly localized on the aryl
substituents, ethynyl linkage, and terminal phenyl ring. The HOMO of T3 is located on the
aryl motif and terminal ring. The LUMOs of T2 and T4 are mainly delocalized on ethynyl
bridge, phenyl ring and, partially, on central pyridine ring and aryl motif. Localization of
LUMO in T3 is similar, but due to the absence of triple bond, a larger part of LUMO is
delocalized on terpyridine unit. Moreover, the alkyl chains participate neither in HOMO nor
in LUMO energy levels, thus giving little influence on the optical properties, but on the other

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hand, their existence significantly improves the solubility of compounds. The introduction of
acetylene linker to T3 has no effect on the localization of frontier molecular orbitals.
Occupied frontier orbital for T1 is also localized on ethynyl linkage, and terminal phenyl
ring, but the HOMO is delocalized on almost the whole molecule.
The next part of in silico studies concerns prediction of absorption spectra by using TD-DFT
calculations, which were also carried out at the B3LYP level of theory with a 6-31G** basis
set. Calculated wavelengths in absorption spectra, oscillator frequencies (f) and transitions for
the highest oscillators (f > 0.20) are listed in Table 3. The obtained results compared to
experimental data show shifts. In the range of calculated absorption spectra five (T1), six
(T2, T3) and twelve (T4) main bands were seen. What is more, the experimental absorption
bands are wide, what can cause diminishing of other, less intense bands. The differences of
the absorption energies of examined compounds T1-T4 with experimental data may be
related to solvent polarity and explained by specific solvent effects.
Table 2. B3LYP/6-31G** calculated geometries for T1-T4.
T1
T2
T3

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Figure 3. Schematic representation of the molecular orbitals for T1-T4.
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Table 3. Wavelength maxima [nm] of absorption spectra together with oscillator strengths
calculated for T1-T4 molecules with TD-DFT method.
Calculated
Code
wavelengths [nm]
Transitions
(
oscillator strengths)
302 (0.17)
H-2→LUMO (25%), HOMO→LUMO (62%),
H-1→LUMO (4%)
295 (0.58)
H-2→LUMO (53%), HOMO→LUMO (30%),
H-6→LUMO (3%), H-5→LUMO (5%),
H-2→L+2 (3%)
T1
294 (0.29)
H-1→L+1 (86%), H-3→L+1 (3%),
HOMO→L+2 (4%)
264 (0.27)
2
50 (0.24)
84 (1.86)
H-1→L+2 (78%), H-4→L+1 (8%), H-1→L+4 (3%)
HOMO→LUMO (98%)
3
T2
314 (0.26)
03 (0.15)
HOMO→L+2 (95%), H-2→LUMO (2%)
3

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291 (0.10)
263 (0.13)
258 (0.18)
347 (1.16)
HOMO→LUMO (97%)
295 (0.40)
HOMO→L+2 (87%), H-1→LUMO (6%)
H-1→LUMO (74%), H-2→L+1 (2%), H-1→L+2 (2%),
HOMO→L+1 (8%), HOMO→L+2 (7%)
294 (0.22)
T3
270 (0.11)
263 (0.19)
253 (0.18)
480 (0.89)
HOMO→LUMO (99%)
H-1→LUMO (85%), H-2→LUMO (2%),
HOMO→L+1 (2%), HOMO→L+3 (7%)
HOMO→L+3 (86%), H-1→LUMO (8%)
3
32 (0.24)
318 (0.29)
278 (0.14)
277 (0.16)
H-10→LUMO (20%), H-3→LUMO (20%),
HOMO→L+6 (14%), HOMO→L+8 (18%)
H-11→LUMO (4%), H-7→LUMO (2%), H-5→L+2
276 (0.27)
T4
(
2%), H-3→L+1 (6%)
273 (0.12)
272 (0.15)
267 (0.16)
263 (0.22)
H-2→L+2 (84%)
H-3→L+1 (78%), HOMO→L+6 (11%), H-1→L+6
2
54 (0.47)
47 (0.18)
(
5%)
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2
2
2
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67
2.4.
Photophysical properties
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2.4.1. UV-Vis absorption and photoluminescence in solution
The UV-Vis absorption and photoluminescence emission (PL) spectra of the terpyridine
derivatives T1-T4 were investigated in dichloromethane (CH Cl ) solution at room
2
2
temperature and are presented in Figure 4a and b. The terpyridines T1-T4 exhibit broad
absorption spectra between 239 and 449 nm. The absorption set of each compound consists at
least of three peaks. The first absorption bands for T1-T4 are located between 239 and
324 nm and can be identified with π→π* transitions of the conjugated pyridine rings [30].
For compounds T2-T4 the additional absorption bands appear between 340 and 449 nm,
which can be ascribed to the intramolecular charge transfer (ICT) states between fluorene and
anthracene units acting as donors and electron-accepting terpyridines. The absorption bands
of T4 are considerably red-shifted compared to T2 and T3, indicating stronger ICT

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interaction in T4 caused by higher donor ability of 9-decyloxyanthracene substituent.
Moreover, the maximum absorption peaks of T3, with a single bond, is shifted to shorter
wavelengths by around 19 nm as compared to compound T2 with acetylene linkage between
tpy and fluorene units. The observed red-shift with respect to T3 is attributed to extension of
π conjugation.
Photoluminescence properties of compounds T1-T4 recorded in CH Cl solutions are
2
2
presented in Figure 4b and the obtained data are collected in Table 4. The PL spectra of T1-
T4 in solution feature strong emission peaks in the range of 349-495 nm. The maxima of
emission decrease from T1 (359 nm) through T3 (407 nm) and T2 (410 nm) to T4 (495 nm),
which is related to the structure of the investigated terpyridine derivatives. The compound T1
emits blue light, whereas the presence of additional terminal substituents, such as fluorene
(T2 and T3) and anthracene (T4) in the backbone, generates the blue-reddish (T2 and T3)
and orange (T4) emission. The emission maximum of compound T3 possessing fluorene
connected with tpy backbone via single bond, is centered at 407 nm, which is shifted by
about 3 nm towards shorter wavelengths with respect to that of T2, which is modified by
extended spacer. Furthermore, the introduction of the pendant 9-decyloxyanthracene
fragment in T4 generates a considerable red-shift of emission maximum, as compared to the
other three compounds (T1-T3). This points out at the strongest electron-donating capacity of
anthracene unit, and thus the resulting highly conjugated π-electron structure of T4.
The quantum yields of T1-T4 emission are in the range from 27 to 84%. The addition of
terminal substituents into phenyl-terpyridine backbone significantly increases the quantum
yields from 27% for T1 ended by ethynyl chain to 84% for T2, which possesses 9,9-
dioctylfluorene and ethylene linkage. In addition, in the case of T2 and T3, the difference
only in the character of spacer yields to large (>20%) change in quantum efficiencies.
Comparing the value of quantum yield of T3 (Φ =0.62) and T2 (Φ =0.84) varying only by
f
f
ethylene linker, to that of the described 4'-(4-(9,9-dihexyl-9H-fluoren-2-yl)phenyl)-2,2':6',2″-
terpyridine (Φ =0.92) [31], the Φ value of the former is higher than that of T3 and
f
comparable to T2. This implies that the presence of additional linker connecting the
peripheral substituents to terpyridine moiety contribute to the enhancement of Φ value.
Furthermore, the obtained Φ values for T1-T4 are considerably higher than that observed for
symmetrically substituted bis(terpyridines) with different aromatic spacer (Φ =0.20-0.58)
f
[32]. The measured lifetime (τ) values for T1-T4 range from 1.02 to 2.97 ns. Among the
studied compounds, compound T1 exhibits the longest fluorescence lifetime (τ=2.97 ns)
resulted from the most planar geometry. Meanwhile, the rigid connection of fluorene unit

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with terpyridine backbone in T3 gives rise to longer lifetime (τ=1.24 ns) than the flexible
ethylene spacer in T2 (τ=1.02 ns).
3
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18
(a)
(b)
3
3
19
20
Figure 4. (a) The UV-Vis and (b) PL spectra of T1-T4 in dichloromethane solution
(c = 10 mol/L).
–
5
3
3
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3
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22
23
24
Table 4. UV-Vis, PL, quantum yield and lifetime data of T1-T4 compounds dissolved in
-5
dichloromethane (c=10 mol/L).
λ
[nm]
PL λem [nm]/
Stokes shift [cm ] [%]
Φ
max
Code
PL λ [nm]
-1
τ [ns]
-5
−1
−1
ex
(
ε/10 M cm )
3
3
49/6682;
59/7480
T1
T2
256 (0.41), 283 (0.64)
320
338
27
84
2.93
1.02
239 (0.23), 343 (0.59)
410/4764
2
2
48 (0.20), 288 (0.32),
97 (0.32), 324 (0.36)
T3
T4
327
421
407/6294
62
55
1.24
2.73
274 (0.53), 325 (0.16),
495/3217
4
27 (0.17), 449 (0.14)
3
3
25
26
The results of optical spectroscopy studies in solution show that the character of substituents
and spacer has prominent influence on the photophysical properties of the terpyridine
derivatives T1-T4. Summarizing, the tpy derivatives are promising luminescent materials
with relatively high quantum yields, broad absorption spectra and enhanced ICT interactions,
when the electron-donating units and highly π-electron spacers are introduced into the
terpyridine molecule.
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3
3
3
3
27
28
29
30
31
32
33
34
35
36
2.4.2. UV-Vis photoluminescence and electroluminescence in solid state
The investigations of ability to photo- and electroluminescence (EL) in solid state as film and
in a matrix consisting of poly(9-vinylcarbazole) (PVK) (50 wt %) and (2-tert-butylphenyl-5-

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biphenyl-1,3,4-oxadiazole) (PBD) (50 wt %) were performed for T1 and T4 compounds.
Their good thermal stability, solubility and solid state character with high PL quantum field
in solution suggested that they can be considered as promising candidates for OLEDs.
Additionally, UV-Vis spectra of T1 and T4 as thin films on glass substrate were registered.
As compared to absorption spectra obtained in solution, bathochromic shift of λmax by about
27 and 4 nm for T1 and T4 in films was seen, respectively (Figure 5a). Photoluminescence
data are gathered in Table 5, whereas the representative PL spectra are depicted in Figure 5.
Table 5. Photoluminescence data of T1 and T4 layers.
Code
Medium
PL λ [nm]
PL λem [nm]
Φ [%]
ex
sh
3
3
10
40
378, 510
8.02
-
Film
sh
374, 510
T1
310
340
410
410
10.60
a
Blend PVK:PBD
-
3
3
3
3
50
10
40
50
410
377, 467, 531
414, 513
414, 437, 520
-
1.75, -, 1.81
-
-
Film
sh
T4
380
10
340
50
439, 522
2.05
11.41, 8.74
3
404, 464
404, 464
411
a
Blend PVK:PBD
-
-
3
a
2
wt % content of compound in PVK:PBD (50:50 in weight %). – not measured.
Bold data indicated the most intense luminescence.
3
3
46
47
PL spectra were registered for various excitation wavelength (λ ). The most intense emission
ex
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49
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was observed under λ equal to 310 nm, except for T4 in film. Contrary to T4, in the case of
ex
T1 as film one emission band with a shoulder was seen. In the PL spectra of T4 two main
emission bands are observed, which changed their respective intensities with decrease of λex
energy and finally under λ =380 nm band with λ at 439 and with shoulder at 522 nm was
ex
em
seen (Figure 5b). The maximum emission band in film and blend of T1 was bathochromically
shifted compared to solution and the opposite behaviour was registered for T4 (Table 4 and
Table 5). The higher PL quantum yield (Φ) was found for T1. In both cases the PL Φ were
higher for blends than for films.

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(a)
(b)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
2500
40
λex=310 nm
λex=340 nm
λex=350 nm
λex=380 nm
λex=400 nm
λex=430 nm
λex=450 nm
Film
Solution CH Cl2
2
2000
PL PVK:PBD
30
T
4
1500
20
1000
T4
10
500
0
0
250
300
350
400
450
500
550
600
650
700
350
400
450
500
550
600
650
700
Wavelength [nm]
Wavelength [nm]
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62
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(c)
(d)
1600
180
T1
T4
Film
2
000
1
400
160
140
120
Blend PVK:PBD 2%
PVK:PBD
Blend PVK:PBD 2%
1200
λex=340 nm
λex=310 nm
1500
1000
500
0
1000
T4
100
8
00
00
00
00
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6
4
2
60
40
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0
300
350
400
450
500
550
600
350
400
450
500
550
600
650
Wavelength [nm]
Wavelength [nm]
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65
Figure 5. (a) UV-Vis spectra of T4 with PL spectrum of matrix, (b) PL spectra of T4 as film
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under various excitations wavelength, (c) PL spectra of T1 and T4 under λ =310 nm, and
ex
(d) PL spectra of T4 in film and blend under λ =340 nm.
ex
Considering UV-Vis spectra of T4 film and PL spectra of matrix in the guest - host diode
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configuration, Förster energy transfer from host (PVK:PBD) to guest can be expected (Figure
5a). In PL spectrum of T4 dispersed molecularly in PVK:PBD under λ =340 nm, which is
ex
the best for excitation of binary matrix, two emission bands were found with λem
hypsochromically shifted as compared to film. The PL band with λ at 404 nm of blend may
em
overlap with the emission band of matrix, thus, it is difficult to conclusively comment on the
completeness of the energy transfer.
In the next step, electroluminescence ability of T1 and T4 was tested in diode with
configuration: ITO/PEDOT:PSS/PVK:PBD:compound/Al. The current density-voltage (J-V)
characteristics were registered up to 5 V (Figure 6).
(a)

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.35
10
T1
T4
0.30
8
6
4
2
0
0
.25
0.20
0.15
0.10
0.05
0.00
-1
0
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2
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-1
0
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Voltage [V]
Voltage [V]
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81
82
(b)
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84
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85
86
87
88
89
Figure 6. (a) Current density – voltage characteristic of devices based on T1 and T4 and (b)
EL spectra of investigated compounds for increasing external voltage together with photo of
diode based on T4 under applied voltage.
The diodes showed low value of turn-on voltage (V ), that is, 1.4 and 2.5 eV for devices
on
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96
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99
00
01
based on T1 and T4, respectively. It is worth noting that the OLED device based on
terpyridine-substituted triphenylamine with rigid benzyl unit exhibited the turn-on voltage at
6.0 V with blue EL at 460 nm [33]. Both diodes with chromospheres T1 and T4 emitted light
under applied voltage and their EL spectra are depicted in Figure 6. The diodes differ in both
intensity of EL and the position of maximum of emission band (λ ). Devices based on T1
em
and T4 emitted light from the orange and green spectral region, respectively. The
significantly more intense EL was measured for the diode based on T4.
2.5.
Electrochemical properties
The electrochemical properties of T1-T4 were investigated in CH Cl solution by means of
2
2
cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The representative

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cyclic voltammograms are presented in Figure 7 (reduction) and Figure 8 (oxidation). DPV is
depicted in Figure 9. The electrochemical oxidation and reduction onset potentials were used
for estimation of the HOMO and LUMO energies (or rather, ionization potentials and
electron affinities) of the materials (assuming that IP of ferrocene equals to 5.1 eV) [34]. The
calculated HOMO and LUMO levels together with electrochemical energy band gap (E ) are
g
presented in Table 6.
For deeper understanding of the photophysical properties of investigated compounds a series
of electrochemical measurements was carried out. The electrochemical properties of T1-T4
were investigated in CH Cl solution using glassy carbon (GC) as working electrode. First,
2
2
the electrochemical properties during reduction process were investigated (Figure 7). All of
the tested compounds undergo reduction between -2.07 (T4), and -2.30 V (T3) (so, at very
similar potentials). Moreover, trends in LUMO energy are consistent in tendency with the
values obtained by DFT calculations. On the other hand, differences observed during the
oxidation process are more significant. The value of onsets of the first oxidation step for T2
and T3 is approximately equal. Thus, incorporation of acetylene linker into molecule does
not affect this parameter. However, the type of this process is slightly different. As can be
seen in Figure 8, for T2 oxidation is irreversible, while in the case of T3 it is rather
reversible. Additionally, we have observed strong influence of electrode materials on
determined values. As can be seen in Figure 8 (brown line) when measurement is carried out
using gold electrode, oxidation take place at significantly lower potential (0.68 compared to
1.04 V in the case of GC electrode). In our opinion it is the consequence of strong interaction
between terpyridine and the metallic surface, yielding species similar to gold complex.
Determined value of E is the lowest for T4 (0.45 V), what can be attributed to strong
ox
electron donating character of alkoxy group. The electrochemically determined band gaps for
all tested compounds differ significantly depending on the substituent. Also, as can be seen in
Table 6, in each case above mentioned values agree well with calculated from UV-Vis
spectroscopy.
4
29
Table 6. Electrochemical data for T1-T4.
Eg el
Eg opt
HOMO
LUMO
[eV]
Eg (DFT)
[eV]
Eox(CV) Eox(DPV) Ered(CV) Ered(DPV)
1
2
3
4
[
eV]
[eV]
[eV]
T1 1.49
T2 1.04
T3 0.99
1.45
1.02
0.93
-2.22
-2.15
-2.30
-2.18
-2.12
-2.24
-6.59
-6.14
-6.09
-2.88
-2.95
-2.80
3.71
3.19
3.29
3.87
3.18
3.10
4.60
3.63
3.98

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T4 0.45
0.33
-2.07
-2.06
-5.55
-3.03
2.52
2.64
2.79
1
2
3
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4
4
30
31
32
EHOMO= - 5.1 - Eox, onset; ELUMO= - 5.1 - Ered, onset; E = Eox, onset - Ered, onset = EHOMO - ELUMO
g el
4
calc. from: Eg=1240/λabs
1
0
0
-
-
-
10
20
30
T1
T2
T3
T4
-
2.7
-2.4
-2.1
-1.8
-1.5
+-1.2
-0.9
-0.6
-0.3
0.0
E (vs. Fc/Fc ) (V)
4
33
4
4
4
34
35
36
Figure 7. Cyclic voltammograms of T1-T4 during oxidation; GC as working electrode;
sweep rate ν = 100 mV/s, 0.1 M Bu NPF in CH Cl Peak onset potentials were used for
estimation of the LUMO energies.
4
6
2
2.
1
1
1
1
1
8
6
4
2
0
8
6
4
2
0
2
4
T1
T2
T3
T4
T2; Au as working electrode
-
-
-
1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
+
E (vs. Fc/Fc ) (V)
4
37
4
4
4
4
38
39
40
41
Figure 8. Cyclic voltammograms of T1-T4 during oxidation; GC as working electrode
(unless otherwise stated) ; sweep rate ν = 100 mV/s, 0.1 M Bu NPF in CH Cl Arrow
indicates additionals peaks while measurment is carried out using gold electrode. Peak onset
potentials were used for estimation of the HOMO energies.
4
6
2
2.

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7
6
5
4
3
2
1
0
T1
T2
T3
T4
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
+
E (vs. Fc/Fc ) (V)
4
42
4
4
43
44
Figure 9. Differential pulse voltammograms of T1-T4; GC as working electrode; potential
step = 2.5 mV/s, 0.1 M Bu NPF in CH Cl
4
6
2
2.
4
45
4
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4
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48
3. Experimental Section
Materials
4
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All chemicals and starting materials were commercially available and were used without
further purification. Solvents were distilled as per the standard methods and purged with
nitrogen before use. All reactions were carried out under argon atmosphere unless otherwise
indicated. Column chromatography was carried out on Merck silica gel. Thin layer
chromatography (TLC) was performed on silica gel (MerckTLCSilicaGel60).
4'-(4-Bromophenyl)-2,2':6',2''-terpyridine [24], 4′-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-
2-yl)phenyl)-2,2′,6′,2″-terpyridine [25, 26], 2-iodofluorene [27], 2-iodo-9,9-dioctylfluorene
[28] were synthesized according to the reported procedures with minor modifications; 9-
decyloxyanthracene, 9-bromo-10-decyloxyanthracene were obtained in innovative way. All
1
compounds were characterized by H NMR spectroscopic analysis (see the Supporting
Information for details).
Procedure for the synthesis of 4′-(4-ethynylphenyl)-2,2′:6′,2′′-terpyridine T1
4
4
4
4
4
62
63
64
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66
4'-(4-Bromophenyl)-2,2':6',2''-terpyridine (5.15 mmol, 2 g) and 140 mL of triethylamine were
placed in two-neck round-bottom flask and bubbled with argon for 15 minutes. After this
time [Pd(PPh ) ] (0.52 mmol, 0.60 g), CuI (0.52 mmol, 0.10 g) were added. The resulting
3
4
solution was stirred and then TMSA (10.3 mmol, 1.46 g) was added by using a syringe.
Mixture was heated at 92 °C for 16 hours. The solution was evaporated and purified by

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chromatography by using CH Cl and EtOAc (20:1) as eluent resulting in white crystals.
2
2
Obtained intermediate was dissolved in 50 mL of MeOH and 80 mL THF and bubbled with
argon. Potassium fluoride (4.34 mmol, 0.25 g) was added and mixture was stirred at room
temperature for 24 hours. The solution was evaporated and the residue was dissolved in 50
mL of CH Cl and extracted with water (3 x 25 mL). The combined organic layers were dried
2
2
under anhydrous MgSO and filtered. After removing the solvent under reduced pressure the
4
crude product was purified by chromatography by using CH Cl and EtOAc (20:1) as eluent.
2
2
General Procedure for the synthesis of 4'-(4-ethynylphenyl)-2,2':6',2"-terpyridine
derivatives in Sonogashira Cross-Coupling reaction for T2 and T4: 4'-(4-Ethynylphenyl)-
2,2':6',2"-terpyridine (1.0 mmol, 0.33 g), Pd(PPh ) (0.06 mmol, 0.070 g) and CuI (0.06
3
4
mmol, 0.01 g) were placed in a 150 mL dry Schlenk flask. Then the flask was evacuated to
vacuum and filled with argon for three times. Appropriate heteroaryl halide (1.2 mmol) was
dissolved in 50 mL solution of THF and NEt (1:1) and under inert atmosphere added to
3
reaction flask. The resulting mixture was stirred at 78 °C for 48 hours. After the reaction was
completed, the mixture was cooled down to room temperature and the solvents were
evaporated under reduced pressure. The residue was dissolved in CH Cl and extracted with
2
2
water and brine and dried over anhydrous MgSO . The solvent was evaporated under reduced
4
pressure, and the crude product was purified on column chromatography on silica gel, eluent:
CH Cl : EtOAc (20:1).
2
2
Procedure for the synthesis of 4'-(4-phenyl)-2,2':6',2"-terpyridine derivative in Suzuki -
Miyaura Cross-Coupling reaction for T3: 4′-(4-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-
yl)phenyl)-2,2′,6′,2″-terpyridine (0.82 mmol, 0.36 g), 2-iodo-9,9-dioctyl-9H-fluorene
(0.69 mmol, 0.35 g), 15 mL THF and solution of Na CO (2.87 mmol, 0.30 g in 3 mL H O)
2
3
2
were placed in a 50 mL round-bottomed flask. Then the flask was filled with argon and
Pd(PPh ) (0.04 mmol, 0.05 g) was added. The resulting mixture was stirred at 80 °C for 30
3
4
hours. After the reaction was completed, the mixture was cooled down to room temperature
and the solvents were evaporated under reduced pressure. The residue was dissolved in
CH Cl and extracted with water and brine and dried over anhydrous MgSO . The solvent
2
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4
was evaporated under reduced pressure, and the crude product was purified on column
chromatography on silica gel, eluent: CH Cl followed by EtOAc.
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T1 (1.7 g, 92 %) as beige solid
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H NMR (400 MHz, CDCl ) δ 8.73 (d, J = 2.1 Hz, 4H), 8.68 (d, J = 8.0 Hz, 2H), 7.91 – 7.86
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(m, 4H), 7.66 – 7.62 (m, 2H), 7.36 (ddd, J = 7.5, 4.8, 1.1 Hz, 2H), 3.18 (s, 1H). C NMR
(101 MHz, CDCl ) δ 156.24, 156.22, 149.43, 149.29, 138.97, 137.02, 132.83, 127.38,
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124.04, 122.95, 121.50, 118.85, 83.47, 78.67.
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HRMS (ESI): m/z calcd. for C H N [MH] 334.1344; found 334.1363.
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T2 (433 mg, 60 %) as dark yellow oil
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H NMR (400 MHz, CDCl ) δ 8.77 (s, 2H), 8.75 (d, J = 4.0 Hz, 2H), 8.69 (d, J = 7.9 Hz, 2H),
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7.94 (d, J = 8.4 Hz, 2H), 7.89 (td, J = 7.8, 1.7 Hz, 2H), 7.70 (dd, J = 9.7, 5.9 Hz, 4H), 7.57 (d,
J = 1.2 Hz, 1H), 7.55 (s, 1H), 7.39 – 7.32 (m, 5H), 2.03 – 1.94 (m, 4H), 1.28 – 0.96 (m, 16H),
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0.82 (t, J = 7.1 Hz, 8H), 0.63 (d, J = 7.8 Hz, 6H). C NMR (101 MHz, CDCl ) δ 156.02,
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155.92, 151.00, 150.79, 149.02, 141.61, 140.36, 137.87, 136.67, 132.06, 130.75, 128.46,
128.34, 127.57, 127.17, 126.91, 125.99, 124.26, 123.75, 122.84, 121.33, 121.24, 120.04,
119.68, 118.46, 92.18, 89.25, 55.13, 40.35, 31.79, 30.02, 29.23, 23.75, 22.60, 14.10.
+
HRMS (ESI): m/z calcd. for C H N [MH ] 722.4474; found 722.4466.
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T3 (256 mg, 55 %) as yellow-orange oil
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H NMR (400 MHz, CDCl ) δ 8.89 (s, 2H), 8.76 (d, J = 4.4 Hz, 2H), 8.71 (d, J = 7.9 Hz, 2H),
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8.05 (d, J = 8.2 Hz, 2H), 7.87 – 7.80 (m, 4H), 7.80 – 7.69 (m, 2H), 7.66 (d, J = 8.2 Hz, 2H),
7.40 – 7.28 (m, 5H), 2.17 – 1.98 (m, 4H), 1.35 – 1.01 (m, 16H), 0.91 – 0.83 (m, 8H), 0.79 (d,
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J = 4.5 Hz, 6H). C NMR (101 MHz, CDCl ) δ 156.24, 155.94, 151.51, 151.03, 149.58,
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149.07, 142.25, 140.83, 140.68, 139.15, 137.02, 136.70, 128.82, 127.65, 127.57, 127.03,
126.86, 126.01, 123.73, 122.90, 121.31, 121.27, 120.07, 119.85, 118.57, 55.20, 40.38, 31.79,
30.05, 29.22, 23.85, 22.62, 14.11.
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HRMS (ESI): m/z calcd. for C H N [MH] 698.4474 found 698.4464.
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T4 (173 mg, 26 %) as orange solid
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H NMR (400 MHz, CDCl ) δ 8.80 (s, 2H), 8.76 (d, J = 3.8 Hz, 2H), 8.69 (dd, J = 8.3, 2.7
3
Hz, 4H), 8.34 (d, J = 8.6 Hz, 2H), 8.00 (d, J = 8.3 Hz, 2H), 7.89 (dd, J = 11.7, 5.1 Hz, 4H),
7.67 – 7.60 (m, 2H), 7.55 (dd, J = 11.4, 3.8 Hz, 2H), 7.36 (ddd, J = 9.8, 4.9, 2.5 Hz, 2H), 4.23
(t, J = 6.6 Hz, 2H), 2.12 – 2.01 (m, 2H), 1.74 – 1.62 (m, 3H), 1.51 – 1.25 (m, 10H), 0.91 (t, J
= 6.8 Hz, 4H).

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C NMR (101 MHz, CDCl ) δ 156.33, 156.23, 153.02, 149.56, 149.30, 138.29, 137.03,
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133.81, 132.20, 127.54, 127.25, 127.00, 125.59, 124.82, 124.72, 124.03, 123.05, 121.54,
118.80, 112.93, 99.84, 88.12, 77.37, 32.06, 30.81, 29.80, 29.76, 29.74, 29.49, 26.37, 22.85,
14.27.
+
HRMS (ESI): m/z calcd. for C H N O [MH ] 666.3484; found 666.3483.
4
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44
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Measurements: NMR spectra were recorded in CDCl with Bruker Advance 400 MHz
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instruments (for H and
C NMR). High-resolution mass spectrometry (HRMS)
measurements were performed using Synapt G2-S mass spectrometer (Waters) equipped with
the electrospray ion source and quadrupole-Time-of-flight mass analyzer. Methanol was used
as a solvent with the flow rate 100 µl/min. The measurement was performed in positive ion
mode with capillary voltage set to 3 kV. The desolvation gas flow was 400 L/h and
temperature 150 °C. The sampling cone was set to 20 V and the source temperature was 120
°C. To ensure accurate mass measurements, data were collected in centroid mode and mass
was corrected during acquisition using leucine enkephalin solution as an external reference
+
(Lock-SprayTM), which generated reference ion at m/z 556.2771 Da ([M + H] ) in positive
ESI mode. The results of the measurements were processed using the MassLynx 4.1 software
(Waters) incorporated with the instrument. Differential Scanning Calorimetry (DSC) was
performed with a TA-DSC 2010 apparatus, under nitrogen atmosphere with heating/cooling
rate of 20 deg/min. Thermogravimetric analysis (TGA) was recorded using TGA/DSC1
Mettler-Toledo thermal analyzer with a heating rate of 10 ºC/min in a stream of nitrogen.
Spectroscopic Measurements: UV-Vis spectra were recorded using Evolution 300
ThermoFisherScientific spectrophotometer at room temperature in denoted solvents with a
conventional 1.0 cm quartz cell. Photoluminescence (PL) spectra in solutions were measured
using Hitachi F-2500 Spectrometer. Quantum yields (Φ ) were estimated using the integrating
f
sphere Avantes AvaSphere-80 with FLS-980 Spectrophotometer (Edinburgh Instruments).
Quantum yields were determined by absolute method using the excitation wavelength with
the most intense luminescence.
Electrochemical Measurements: Electrochemical measurements were carried out using Eco
Chemie Autolab PGSTAT128n potentiostat, glassy carbon electrode (diam. 2 mm), platinum
coil and silver wire as working, auxiliary and reference electrode, respectively. Potentials are
referenced with respect to ferrocene (Fc), which was used as the internal standard. Cyclic

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voltammetry experiments were conducted in a standard one-compartment cell, in CH Cl2
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(Carlo Erba, HPLC grade), under argon. 0.2 M Bu NPF (Aldrich, 99%) was used as the
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supporting electrolyte. The concentration of compounds was equal 1.0·10 mol/dm .
Deaeration of the solution was achieved by argon bubbling through the solution for about
10 min before measurement. All electrochemical experiments were carried out under ambient
conditions.
Film and blend PVK:PBD on glass preparation: Films and blends in PVK:PBD (50:50 in
weight %) were prepared by spin-coating (1000 rpm, 60 s) on a glass substrate from
homogenous chloroform solution (10 mg/mL) and dried 5 min in a vacuum oven at 100 ºC.
OLED preparation and EL measurements: Devices with the following sandwich structure
configuration ITO/PEDOT:PSS/PVK:PBD:compound/Al with 2 wt. % complex content in
blend were prepared. Devices were prepared on OSSILA substrates with pixilated ITO
anodes, cleaned by OSSILA procedure recommendation. Substrates were covered with
PEDOT:PSS film by spin coating at 5000 rpm for 60 s and annealed for 15 min at 120 °C.
Active layer was spin-coated on top of the PEDOT:PSS layer from CHCl solution
3
(10 mg/mL) at 1000 rpm for 60 s and annealed for 5 min at 100 °C. Finally Al was vacuum-
deposited. J-V characteristic were registered using Keithley SourceMeter.
Electroluminescence (EL) spectra were measured with the voltage applied using a precise
voltage supply (Gw Instek PSP-405) and the sample was fixed to an XYZ stage. Light from
the OLED device was collected through a 30 mm lens, focused on the entrance slit (50 µm)
of a monochromator (Shamrock SR-303i) and detected using a CCD detector (Andor iDus
12305). Typical acquisition times were equal to 10 seconds. The pre-alignment of the setup
was done using a 405 nm laser.
4. Conclusions
We presented the synthesis and comprehensive characterization of derivatives of 4'-phenyl-
2,2':6',2''-terpyridine with ethynyl (T1), 2-ethynyl-9,9-dioctylfluorene (T2), 9,9-
dioctylfluorene (T3), 9-ethynyl-10-decyloxyanthracene (T4) substituents. Described
molecules T1-T4 were prepared by Sonogashira or Suzuki-Miyaura coupling reaction,
respectively, with yields between 26 - 92%. Two of obtained molecules are in solid state (T1,
T4), whereas T2 and T3 containing fluorene motif are oils. All reported compounds are

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soluble and photo- and electroluminescent. T1 and T4 are thermally stable, while T2 and T3
exhibit significantly lower melting temperature, the temperature of 5% sample weight loss is
also lower. T2 exhibits a bathochromic shift in its absorption and emission spectra and shows
higher quantum yield in comparison to T3. Obtained data suggest that the acetylene bridge
enhances the conjugation of the compound and promotes more efficient energy transfer. It
was found that the presence of terminally substituted group, such as alkoxyanthracene via
triple bond to 4'-phenyl-2,2':6',2''-terpyridine, significantly modified a wide range of their
properties. The introduction of 9-decyloxyanthracene motif increases the PL quantum yield in
the solid state in the form of blend with PVK:PBD and EL intensity. Results obtained from
electrochemical, optical and DFT studies are consistent, the values of the band gaps are very
similar. The results showed that the terpyridines are very promising candidates for the
construction of OLEDs.
Acknowledgments
This work was supported by the Ministry of Science and Higher Education, Poland
(Diamentowy Grant number 0215/DIA/2015/44).
Calculations have been carried out using resources provided by Wroclaw Centre for
Networking and Supercomputing (http://wcss.pl), grant No.18.
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