A novel highly efficient nanostructured organosilicon luminophore with unusually fast photoluminescence

Article abstract of DOI:10.1039/c6tc00979d

Synthesis and theoretical and experimental investigations of a novel nanostructured organosilicon luminophore (NOL) containing six 2,2′-bithienyl donor units connected via silicon atoms to a 1,4-bis(5-phenylthienyl-2-yl)-benzene acceptor unit with efficie

Full text of DOI:10.1039/c6tc00979d

View Article Online
View Journal
Journal of
Materials Chemistry C
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: T. Starikova, N.
Surin, O. Borshchev, S. Pisarev, E. Svidchenko, Y. V. Fedorov and S. Ponomarenko, J. Mater. Chem. C,
2016, DOI: 10.1039/C6TC00979D.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/materialsC

Please do not adjust margins
Journal of Materials Chemistry C
Page 1 of 10
View Article Online
DOI: 10.1039/C6TC00979D
Journal of Materials Chemistry C
ARTICLE
A Novel Highly Efficient Nanostructured Organosilicon
Luminophore with Unusually Fast Photoluminescence
Received 00th January 20xx,
Accepted 00th January 20xx
T.Yu. Starikova,a,b N.M. Surin,a O.V. Borshchev,a S.A. Pisarev,a,c E.A. Svidchenko,a Yu.V. Fedorovd
and S.A. Ponomarenkoa,e
*
DOI: 10.1039/x0xx00000x
Synthesis, theoretical and experimental investigations of a novel Nanostructured Organosilicon Luminophore (NOL)
containing six 2,2’-bithienyl donor units connected via silicon atoms to 1,4-bis(5-phenylthienyl-2-yl)-benzene acceptor unit
with efficient intramolecular Förster resonance energy transfer is reported. It shows a unique combination of optical
properties: high photoluminescence (PL) quantum yield up to 91%, fast PL decay time down to 800 ps, large pseudo Stocks
shift of 101 nm and huge molar extinction coefficient of 1.4×105 M-1cm-1. These peculiarities caused by the specific
arrangement of the donor and acceptor fragments at the nanoscale distance within the NOL were correlated with the
molecular structure of NOL using theoretical calculations, which for the first time allowed successful prediction of the
oscillator strength, PL decay time and intramolecular energy transfer efficiency. Comparison of the photophysical
properties of the NOL with standard laser dye POPOP in THF and toluene solutions revealed its huge application potential
in organic photonics and high energy physics.
www.rsc.org/
quantum yield (PLQY). Increasing π-conjugation length in organic
luminophores is a powerful tool to increase σ, but it is limitedly
applicable as it also leads to a significant red shift of the optical
1. Introduction
Organic π-conjugated molecules, luminophores and chromophores,
find wide applications as functional materials for engineering
various devices in organic photonics1, photovoltaics2, nuclear and
particle physics3, as well as for biomedical purposes.4 One of the
prospective directions is the development of organic luminophore-
based scintillation detectors.5 Compared to inorganic counterparts,
organic luminophores exhibit much faster photoluminescence (PL)
decay times along with their better compatibility with polymeric
matrices and organic solvents. Thus, organic luminophore-based
plastic or liquid scintillation detectors are easy processable and
provide very high timing resolution in contrast to their inorganic
analogues.6 This is essential for studying ultrafast processes of
elemental particles interactions as well as for biomedical challenges
of time-of-flight positron emission tomography technique.7
8
spectra. An original approach to increase
σ of organic
luminophores avoiding at the same time the red shift has been
recently introduced as Nanostructured Organosilicon Luminophores
(NOLs) architecting.9 NOL is a highly efficient branched or dendritic
organosilicon “molecular antennae”,10 which consists of several
peripheral donor (D) luminophore units connected to a central
acceptor (A) luminophore unit via silicon atoms (Fig.1a).
Silicon atoms in any NOL molecule provide isolation of
π-conjugated electronic systems of each luminophore unit (D or A),
maintaining a very short distance between them at the same time.
Such a close proximity (1-2 nm) of donor to acceptor promotes
efficient nonradiative Förster resonance energy transfer (FRET)
from the former to the latter.11 As a result, electronic excitation
energy absorbed by the whole NOL molecule is re-emitted by the
acceptor unit. Choosing different donor and acceptor units it is
possible to tune independently the absorption and emission spectra
of NOLs in the desired region of the visible spectrum.9b Due to their
“composite” structure, NOLs can serve as both the activator and the
spectral shifter in plastic scintillators leading to their improved
efficiency.9a
A
competitive luminophore for improved scintillation
applications, together with the fast decay time, should possess such
properties as large absorption cross-section (σ) and a high PL
NOLs combine the best features of organic luminophores with
those of inorganic quantum dots (Q-dots) and other luminescent
nanomaterials, like carbon dots (C-dots) or semiconducting polymer
dots (P-dots).12 Similar to inorganic Q-dots, NOLs have an increased
absorption in the short wave-range region and a broadband
absorption spectrum lacking in the organic luminophores. Unlike
most metal-containing nanomaterials, NOLs are not toxic and show
very fast fluorescence.
A combination of excellent solution
processability, high brightness caused by large values of molar
This journal is © The Royal Society of Chemistry 2016
J. Mater. Chem. C, 2016, 8, 1-10 | 1
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 2 of 10
View Article Online
DOI: 10.1039/C6TC00979D
ARTICLE
Journal of Materials Chemistry C
2.1 Synthesis
Synthetic routes to NOL and TMS-PTPTP-TMS are summarized in
Scheme 1, while that for TMS-2T-Hex was reported elsewhere.14
Preparation of these molecules is based on Kumada and Suzuki
organometallic cross-coupling reactions widely used for the
synthesis of various conjugated oligomers and polymers.15
In the case of NOL, two key precursors, 1,4-bis[5-(4,4,5,5-
tetramethyl-1,3,2-dioxaborolane-2-yl)thiophene-2-yl]benzene
(PinB-TPT-BPin) and (4-bromophenyl)trichlorosilane (BrPhSiCl3)
were prepared at first (Scheme 1a). For this purpose 1,4-bis(2-
thienyl)benzene (TPT) was obtained via coupling of 2-thienyl
magnesium bromide with 1,4-dibromobenzene under Kumada
conditions (yield 77%). Lithiation of TPT and following treatment
with
2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane
(IPTMDOB) allowed to obtain Pin-B-TPT-B-Pin in 89% yield.
Synthesis of BrPhSiCl3 was performed in three stages. First, 4-
bromophenylmagnesium bromide BrPhMgBr was prepared via
lithiation of 1,4-dibromobenzene with n-butyl lithium followed by
lithium-magnesium exchange reaction with freshly prepared diethyl
ether complex of magnesium bromide. This step differs from the
previously published method,16 where BrPhMgBr was obtained via
Grignard reaction of 1,4-dibromobenzene with magnesium, in order
to prevent formation of
a disubstituted by-product. Second,
BrPhMgBr was treated with the excess of tetraethoxysilane Si(OEt)4
to form 4-bromophenyl(triethoxy)silane BrPhSi(OEt)3 in 28%
isolated yield. Third, ethoxy groups of the latter were substituted
with Cl via treatment with the excess of thionylchloride, giving rise
to BrPhSiCl3 in 86% isolated yield. It was used for the synthesis of
Fig. 1 Schematic representation of different NOL structures (types I
and II) (a), chemical structure of (PTPTP)2Si2(2T-Hex)6 NOL (b) and
model compounds investigated in this work (c).
extinction coefficient, high PLQY, fast luminescence decay and
possibility to adjust the emission wavelength in a wide spectral
region allows NOLs to be almost ideal luminescent nanomaterials
for various photonic applications.
(4-bromophenyl)[tris(5’-hexyl-2,2’-bithien-5-yl)]silane
BrPhSi(2T-
Hex)3 via its coupling with the lithium derivative of 5-hexyl-2,2’-
bithiophene (2T-Hex) in 65% isolated yield. Finally, BrPhSi(2T-Hex)3
was reacted with Pin-B-TPT-B-Pin under Suzuki conditions to
Most of the previously reported NOLs contained four donors
per one acceptor luminophore units in the molecule (NOL of type I
in Fig 1a),9 while for the NOL reported in this work the D : A ratio is
for the first time increased up to six, thus representing a new type
of NOLs (type II in Fig. 1a). Moreover, we report here the first NOL
with 1,4-bis(5-phenylthienyl-2-yl)-benzene (PTPTP) acceptor unit
(Fig. 1b) and investigate its optical properties both experimentally
and theoretically as compared to model compounds: PTPTP, its
trimethylsilyl derivative TMS-PTPTP-TMS and 1,4-bis(5-phenyl-
oxazol-2-yl)-benzene (POPOP) – organic luminophore widely used
as a laser dye and spectral shifter in plastic scintillators (Fig. 1c).
give
the
desired
1,4-bis[5-{4-[tris(5’-hexyl-2,2’-bithien-5-
yl)silyl]phenyl}thiophene-2-yl]benzene (NOL) in 34% isolated yield.
Scheme 1. Synthetic routes to NOL (a) and TMS-PTPTP-TMS (b).
a)
1) Mg, THF, reflux
O
Br
Br
S
1. n-BuLi
2. IPTMDOB
THF, -20oC
B
O
2)
Br
S
S
O
B
S
S
O
Pd(dppf)Cl2,
THF, 0 - 20 °C
PinB-TPT-BPin
TPT
1) BuLi
Br
2) MgBr2*Et2
C
S
C
l
O
SOCl2
Si(OEt)4
THF, 0oC
Br
O
Br
M
Br
iC
l
l
O
Br
Si
O
g
THF, -78oC
50-75oC
B
r
BrPhMgBr
BrPhSiCl3
BrPhSi(OEt)3
C 6
Br
H
3
1
S
1) n-BuLi
N
O
L
2. Results and discussion
S
PinB-PTPTP-BPin
2) BrPhSiCl3
S
S
S
i
S
H
3
1 C 6
Pd(dppf)Cl2
toluene/ethanol
THF, -78oC
S
For the NOL reported in this work, 2,2’-bithiophene (2T) was chosen
as a donor, like in the most previously reported NOLs, while a novel
acceptor based on 1,4-bis(5-phenylthienyl-2-yl)-benzene (PTPTP,
also reported as AC5) known for its high PLQY13 was used. For
increasing solubility of the NOL, each of six donor units was end-
capped with n-hexyl (Hex) groups. Thus, the NOL could be
abbreviated as (PTPTP)Si2(2T-Hex)6, while trimethylsilyl (TMS)
derivatives of the donor and acceptor units also investigated in this
work for comparison reasons are marked as TMS-2T-Hex and TMS-
PTPTP-TMS (Fig. 1b,c).
(PTPTP)Si2(2T-Hex)6
S
2T-Hex
2M Na2CO3 aq.,
S
C 6
H
3
110oC
1
H
3
1 C 6
BrPhSi(2T-Hex)3
b)
1) Mg, THF, reflux
Br
S i
2)
1) n-BuLi
O
B
S
TMS-PT-BPin
S
2) IPTMDOB
S
i
Br
S
S
i
S
O
S
Pd(dppf)Cl2,
THF, 0 - 20 °C
TMS-PT
S
i
Pd(PPh3)4
S
i
+
Br
Br
TMS-PT-BPin
Toluene/ethanol
2M Na2CO3 aq.,
TMS-PTPTP-TMS
110oC
2 | J. Mater. Chem. C, 2016, 8, 1-10
This journal is © The Royal Society of Chemistry 2016
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 3 of 10
View Article Online
DOI: 10.1039/C6TC00979D
Journal of Materials Chemistry C
ARTICLE
(a)
(b)
(c)
(d)
(e)
(f)
14
1,4-bis[5-{4-(trimethylsilyl)phenyl}thiophene-2-yl]benzene
(TMS-PTPTP-TMS) was prepared through a three steps synthesis
(Scheme 1b). First, trimethyl[4-(2-thienyl)phenyl]silane (TMS-PT)
was synthesized via Kumada coupling of 2-thienylmagnesium
bromide with 1-bromo-4-(trimethylsilyl)benzene (Br-P-TMS) in 99%
isolated yield. Subsequent lithiation of TMS-PT followed by its
treatment with IPTMDOB gave rise to {4-[5-(4,4,5,5-tetramethyl-
1,3,2-dioxaborolan-2-yl)thiophene-2-yl]phenyl}(trimethyl)silane
(TMS-PT-B-Pin, 80%). The latter was reacted with 1,4-dibromo-
benzene under Suzuki conditions to yield TMS-PTPTP-TMS (53%).
Chemical structure and purity of all precursors and final
compounds were proved by a combination of TLC, GPC, 1H-, 13C-
and 29Si-NMR, MALDI-TOF MS and elemental analysis. Detailed
synthetic procedures and full characterization of the precursors and
final compounds can be found in the Experimental part and ESI.
12
10
8
(g)
6
4
2
0
300
350
400
450
500
550
600
650
Wavelength [nm]
Fig. 2 Absorption spectrum of NOL (a), it donor TMS-2T-Hex (b) and
acceptor TMS-PTPTP-TMS components (c); theoretical absorption
spectrum of NOL obtained by a superposition of b (multiplied by
6.1) and c (multiplied by 1.2) (d); emission spectra of NOL (ꢀꢃꢁꢂ
338 nm (e); ꢀꢄꢁꢂ = 389 nm (f); emission spectrum of TMS-2T-Hex (g).
2.2 UV-Vis absorption and photoluminescence measurements
=
Optical spectra of NOL, its model donor (TMS-2T-Hex) and
acceptor (TMS-PTPTP-TMS) components in dilute THF solutions are
shown in Fig. 2. For comparison reasons absorption spectra are
plotted as molar extinction coefficients (ε) distributions. The
absorption spectrum of NOL (Fig. 2a) has two maxima at 338 and
389 nm, corresponding to its donor and acceptor components,
respectively (Table 1). The model compounds, TMS-2T-Hex and
TMS-PTPTP-TMS, show absorption maxima at 317 and 383 nm,
respectively (Fig. S30-S32 in ESI). These are 21 nm and 6 nm blue
shifted as compared to the donor and acceptor components of the
luminophores within the NOL. ε of the donor peak of NOL (138300
M-1cm-1) is ca. 6 times higher as those of TMS-2T-Hex (19300
M-1cm-1) meaning that all six donor components contribute to the
absorption spectrum of NOL additively. ε of the acceptor peak of
NOL (75500 M-1cm-1) is ca. 20% higher as those of TMS-PTPTP-TMS
(62700 M-1cm-1) and ca. 45% higher as those of PTPTP (52000
M-1cm-1). Such gradual increase in ε of the acceptor and its model
compounds can be explained both by the influence of silicon atoms
and closely located donor luminophores within the NOL.
A
model absorption spectrum of NOL obtained by a
superposition of the absorption spectra of TMS-2T-Hex and
TMS-PTPTP-TMS with a ratio of 6.1 : 1.2 with the corresponding
spectral shifts results in an accurate approximation of the
experimental absorption spectrum of NOL (Fig.2, d). Slight deviation
from the theoretical D : A ratio of 6 : 1 comes from the difference in
ε of the model compounds and the corresponding NOL fragments,
the origin of which will be discussed below.
Since absorption efficiency depends on the oscillator strength of
the particular luminophore, we estimated the oscillator strength
from the experimental data (ꢅꢁꢂꢉ) according to formula (1):
ꢆꢇꢈ
ꢐꢑ
ꢅꢁꢂꢉ = 4.32 ∗ 10ꢊꢋ
ꢍꢄ ꢓꢔꢕꢖꢇ →ꢇ ꢙꢚꢕꢖ,
(1)
ꢌ
ꢆꢇꢈ
ꢎꢏ
ꢗ
ꢘ
ꢒ
where ꢕꢖꢇ →ꢇ is the transition frequency into the first excited singlet
ꢗ
ꢘ
state S0→S1, ꢓꢔꢕꢖ
ꢙ is the corresponding molar extinction
ꢇꢗ→ꢇꢘ
coefficient, ꢍꢎꢏ is the refractive index.
Table 1. Experimentally measured and theoretically estimated optical properties of the luminophores in dilute THF solutions.
ꢢꢞꢨ
ꢬꢭꢊꢬꢮ
ꢢꢞꢨ
ꢰꢠꢩ
ꢢꢜ
ꢝꢟꢠ
ꢩꢝꢪꢩ
ꢩꢝꢪꢩ
ꢰꢠꢩ
Luminophore
NOL
ꢛ
,
ꢣꢤꢥꢦ, ꢧꢢꢞꢨ/ꢧꢩꢝꢪꢩ
,
ꢱꢲꢱꢢꢞꢨ/
ꢛ
,
ꢡꢜꢝꢞ×104,
ꢫꢖ
/ꢫꢖ
,
ꢯ
/ꢯ
ꢜꢝꢞ
ꢜꢝꢞ
ꢬꢭꢊꢬꢮ
nm
M-1cm-1
ns
ꢱꢲꢱꢩꢝꢪꢩ, %
cm-1
nm
%
338
389
317
383
376
361
13.83
7.55
1.93
6.27
5.20
5.72
439,468
439,468
377
89
91
5.5
88
83
94
0.90b/
-
-
-
0.93a/0.88
≈0.17c/1.53
1.01a/0.95
1.03a/1.08
1.19a/1.01
23600/24800
28500/32900
23900/25600
24300/26000
25840/26810
2.85/2.77
0.89/0.90
2.46/2.41
2.18/2.10
2.11/2.07
97/98
TMS-2T-Hex
TMS-PTPTP-TMS
PTPTP
431,459
424,450
393,416
РОРОР
Notes: ꢀꢴꢳꢵꢴꢇꢂ — absorption maximum wavelength; ꢓꢳꢴꢂ — molar extinction coefficient corresponding to ꢀꢴꢳꢵꢴꢇꢂ; ꢀꢁꢳꢳꢴꢂ — emission maximum wavelength;
ꢶꢷꢸꢹ — photoluminescence quantum yield; ꢺꢁꢂꢉ and ꢺꢈꢴꢻꢈ, ꢕꢖ ꢁꢂꢉ and ꢕꢖꢼꢈꢴꢻꢈ , ꢅꢁꢂꢉ and ꢅꢈꢴꢻꢈ, ꢽꢾꢽꢁꢂꢉ and ꢽꢾꢽꢈꢴꢻꢈ are experimentally and theoretically
ꢊꢼ
ꢘ
ꢆꢇꢈ
ꢆꢇꢈ
ꢼ
ꢗ
ꢊꢼ
ꢘ
ꢗ
estimated values of PL decay time, S0→S1 transition frequency, oscillator strength and intramolecular energy transfer efficiency, respectively. ꢀꢿꣀꣁ
=
( )
369 ꢍꣂ (ꣃ); 340 ꢍꣂ (꣄); 310 ꢍꣂ ꣅ .
This journal is © The Royal Society of Chemistry 2016
J. Mater. Chem. C, 2016, 00, 1-8 | 3
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 4 of 10
View Article Online
DOI: 10.1039/C6TC00979D
ARTICLE
Journal of Materials Chemistry C
The data obtained revealed that ꢅꢁꢂꢉ of the NOL acceptor unit 88% and 83%, respectively. At this point we conclude that NOL
ꢆꢇꢈ
(2.85) exceeds that of PTPTP (2.18) by 31% and that of TMS-PTPTP- shows
a higher fluorescence rate constant ꣆꣇ = ꢶꢷꢸꢹ/ꢺ . As
TMS (2.46) by 16% (Table 1). The larger value of the oscillator follows, the presence of donor fragments in a close proximity to
strength for the acceptor unit of NOL is manifested in its higher acceptor within the NOL does not lead to aggregation PL quenching.
absorptivity that gradually increases from PTPTP itself first by the
2.3 Theoretical calculations
inductive influence of silicon atoms (in TMS-PTPTP-TMS) and
Optical properties of the NOL could be rationalized better on the
second by the influence of the donor luminophores located in the
basis of the results of computer simulations of its molecular
close proximity to the acceptor within the NOL.
geometry and frontier orbitals. Geometry optimization and TD DFT
PL spectra of NOL registered at excitation wavelengths ꢀꢃꢁꢂ
338 nm (e) and ꢀꢄꢁꢂ = 389 nm (f) have nearly identical shapes with
=
calculations for the excited states of the compounds investigated
revealed that molecular orbitals (MO) of the donor units in their
ground and the first excited states (HOMO-1 and LUMO+1 energy
levels of NOL in Fig.3) do not significantly overlap with the MO of
the acceptor unit in its ground and the first excited states (HOMO
and LUMO energy levels of NOL in Fig.3). That is in a sharp contrast
to the orbitals mixing within the model luminophores themselves,
the frontier MO of which can be found in Table S1 of the ESI. These
calculations for the first time undoubtedly confirm that silicon
atoms in the NOL brake the conjugation between the adjacent
luminophores. Therefore, the only possible mechanism of the
intramolecular excitation energy transfer within the NOL is FRET.
Theoretically estimated ETE (ETEcalc) for NOL was deduced from
PL spectra of the donor units and absorption spectra of the
acceptor using the Förster formula11 considered in details for the
first organosilicon “molecular antennas” elsewhere.10 Spectral
distribution of the acceptor extinction coefficient was deduced
from its model absorption spectrum (Fig. 2c). Orientation factor
was calculated for the angles between directions of transition
moments S0→S1 either for the donor or for the acceptor. The angles
were estimated after molecular geometry optimization. The
calculated energy transfer efficiency ETEcalc was found to be 98±2%,
which is in a good agreement with the experimentally determined
value of ETEexp = 97±2% (Table 1).
two luminescence maxima at 439 and 468 nm. They correspond
very well to the emission spectrum of TMS-PTPTP-TMS modelling
the acceptor (Fig. S32 in ESI). Any traces of the emission from the
donor fragments modelled by TMS-2T-Hex with PL maximum at 377
nm (Fig. 2g) are absent. These observations evidence for a very
efficient intramolecular excitation energy transfer from the donor
to the acceptor fragments within the NOL. The estimated
intramolecular energy transfer efficiency (ETE) as a ratio of PLQYs,
registered at ꢀꢃꢁꢂ and ꢀꢄꢁꢂ was found to be ETEexp
= 97±2%.
Interestingly, that PLQY of NOL (91%) was undoubtedly higher as
those of TMS-PTPTP-TMS (88%) and especially as those of PTPTP
(83%) measured under the same conditions with the relative
experimental error of +/-0.5%.
It should be also noted that the Stocks shift (difference between
the absorption and luminescence maxima of the same electronic
transition) in the series of compounds PTPTP, TMS-PTPTP-TPS and
(PTPTP)Si2(2T-Hex)6 is almost the same (48, 48 and 50 nm,
respectively) due to simultaneous red shift of both the absorption
and luminescence maxima of PTPTP core. However, the highly
efficient ETE within the NOL leads to a large pseudo Stocks shift
(difference between the maxima of the donor absorption and
acceptor emission spectra) of 101 nm, which has a primary
importance for NOL due to the absence of any emission from the
donor units.
The calculated/experimentally measured frequencies of S0 → S1
transitions ꢕꢖꢇ →ꢇ of the NOL acceptor unit (24800/23600cm-1) are
ꢗ
ꢘ
For better understanding photophysical properties of the
compounds under investigation, PL kinetics of NOL and model
compounds was measured by time-correlated single photon
counting technique (Table 1 and Figs. S33-S37 in ESI). 17 The
experimentally measured PL lifetime (ꢧꢢꢞꢨ) for NOL in dilute THF
solution (0.93 ns) was found to be significantly shorter than those
for TMS-PTPTP-TMS (1.01 ns) and PTPTP (1.11 ns) by 8% and 16%,
respectively (Fig.S34-S37 in ESI), bearing in mind that the
experimental error of the lifetime measurements was +/-0.005 ns.
Moreover, ꢧꢢꢞꢨ measured for NOL at ꢀꢃꢁꢂ (0.90 ns) turned out to be
shorter as compared to that measured at ꢀꢄꢁꢂ (0.93 ns) by 3-4 %, as
well as PLQY at ꢀꢃꢁꢂ is lower compared to PLQY at ꢀꢄꢁꢂ by the same
value. This obviously follows from the equation: ꢶꢷꢸꢹ (ꢀꢃꢁꢂ) =
only 1200/1300cm-1 and 800/300cm-1 lower as compared to the
corresponding values for PTPTP and TMS-PTPTP-TMS, respectively.
The difference between the experimentally measured and the
calculated values of the frequencies of S0 → S1 transitions are 1700
cm-1 for both PTPTP and TMS-PTPTP-TMS and only 1300 cm-1 for
NOL. Since TD DFT calculations were made in vacuum, these results
show that the solvent influence on ꢕꢖꢇ →ꢇ of NOL is smaller as
ꢗ
ꢘ
compared to its impact on PTPTP and TMS-PTPTP-TMS. We assign
this effect to a partial shielding of the emitting core in NOL by six
donor fragments from the solvent molecules and stabilization of
the solvation shell.
Theoretically estimated oscillator strength ( ꢅꢈꢴꢻꢈ
) was
ꢆꢇꢈ
evaluated using calculations of the transition probabilities by means
ꢽꢾꢽ × ꢶꢷꢸꢹ (ꢀꢄꢁꢂ
)
(and, consequently, ꢺꢁꢂꢉ (ꢀꢃꢁꢂ) = ꢽꢾꢽ ×
of TD DFT. The calculation revealed that ꢅꢈꢴꢻꢈ of the NOL acceptor
ꢺꢁꢂꢉ(ꢀꢄꢁꢂ)). Indeed, the variation of ꢺꢁꢂꢉ measured is in a good
agreement with ETEexp value.
ꢆꢇꢈ
unit (2.77) exceeds that of PTPTP (2.1) by 31.9% and that of TMS-
PTPTP-TMS (2.41) by 14.9% (Table 1). These values are in a good
agreement with the experimentally determined values of the
It is noteworthy that the lifetime reduction discussed above is
not accompanied by a decrease in PLQY, as it normally happens:
compare with τ = 0.17 ns and PLQY = 5.5% for TMS-2T-Hex (Table 1
and Fig. S33 in ESI). On the contrary, the PLQY of NOL measured at
ꢀꢄꢁꢂ is equal to 91%, while those of TMS-PTPTP-TMS and PTPTP are
oscillator strength ꢅꢁꢂꢉ discussed above, thus confirming the
ꢆꢇꢈ
conclusions about the influence of silicon atoms and close proximity
of the donor luminophores within the NOL on its higher
absorptivity. Low values of the oscillator strength determined both
4 | J. Mater. Chem. C, 2016, 8, 1-10
This journal is © The Royal Society of Chemistry 2016
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 5 of 10
View Article Online
DOI: 10.1039/C6TC00979D
Journal of Materials Chemistry C
ARTICLE
ꢃ.꣈
ꢺꢈꢴꢻꢈ
=
(2)
꣇꣋꣌꣍꣋ꢎꢏ꣊꣎
꣉꣊꣋
→꣊
ꢘ
ꢗ
These theoretical calculations are in a good agreement with the
experimentally measured PL lifetime (ꢧꢢꢞꢨ for NOL, TMS-PTPTP-
)
TMS and PTPTP in dilute THF solution discussed above. Hence, NOL
demonstrates a faster PL decay time as the model acceptor
luminophores. Since MOs of donor and acceptor fragments in NOL
do not overlap, we can conclude that the increase in ꢅꢈꢴꢻꢈ and the
ꢆꢇꢈ
reduction of
τ for the acceptor fragment is a result of inductive
influence of the donor fragments on the acceptor within the NOL.
Thus, we have demonstrated that optical properties of NOL,
including the donor to acceptor energy transfer efficiency ETEcalc
,
frequencies of S0 → S1 transitions ꢕꢖꢇ →ꢇ , oscillator strength ꢅꢈꢴꢻꢈ
ꢆꢇꢈ
ꢗ
ꢘ
and PL lifetime ꢺꢈꢴꢻꢈ, can be successfully estimated by the standard
calculation methods used for conjugated organic molecules. This
should allow prediction of the optical properties of novel NOLs
before their synthesis. That looks very promising, since a number of
new structures, which is possible to synthesize by chemical linking
of various organic luminophores via silicon atoms into different
types of NOLs is almost unlimited.9b
3.4 Comparison of NOL with the standard laser dye POPOP
To reveal further
a high application potential of NOL
(PTPTP)Si2(2T-Hex)6, let’s compare its optical properties to those of
POPOP – one of the standard organic luminophores, widely used in
organic photonics as a laser dye and in plastic scintillators as a
highly efficient spectral shifter. As can be seen from Table 1 and Fig.
4, in dilute THF solutions NOL has ca. 2.4 times higher molar
extinction coefficient at the absorption maximum (13.8 × 104
M-1cm-1 vs 5.72 × 104 M-1cm-1) and ca. 3 times higher integral
extinction coefficient as those of POPOP. This leads to a more
efficient UV light absorption by NOL, especially in high-energy
region of 300-350 nm. Both luminophores has very high PLQY (91%
and 94% in THF, respectively), while NOL has ca. 30% faster
luminescence decay (0.90 ns vs 1.19 ns – see Fig. S38 in ESI).
More important for various photonic applications is
a
comparison of their optical properties in toluene, which is a good
model for such optical media as polystyrene or linear alkyl
benzenes (LAB) often used in plastic or liquid scintillators, 18
respectively, (Table 2). In dilute toluene solutions, some quenching
(a)
(b)
(c)
(d)
14
12
10
8
Fig. 3 Visualization of the frontier molecular orbitals of NOL
(isosurfaces at ±0.015).
6
experimentally and theoretically for model donor molecule TMS-
2T-Hex (ꢅꢁꢂꢉ = 0.89 and ꢅꢈꢴꢻꢈ = 0.90) also correlate very well
ꢆꢇꢈ
ꢆꢇꢈ
4
with its low ε = 19300 M-1cm-1.
2
The first excited singlet state PL lifetime ꢺꢈꢴꢻꢈ for the S0→S1
transition in NOL theoretically calculated according to formula (2)
was found to be reduced as compared to TMS-PTPTP-TMS and
initial PTPTP by 7.4% and 16 %, respectively: 0.88 ns vs 0.95 ns and
1.05 ns (Table 1):
0
250
300
350
400
450
500
550
600
650
Wavelength [nm]
Fig. 4 Comparison the absorption spectra of NOL (a) and POPOP (b);
the emission spectra of NOL (c) and POPOP (d).
This journal is © The Royal Society of Chemistry 2016
J. Mater. Chem. C, 2016, 8, 1-10 | 5
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 6 of 10
View Article Online
DOI: 10.1039/C6TC00979D
ARTICLE
Journal of Materials Chemistry C
Table 2. Comparison of the optical properties of NOL and POPOP in and toluene were distilled and degassed in argon flow. Unless
dilute toluene solutions.
otherwise stated, all glassware before the reactions was dried at
150°C, assembled while hot, and cooled in argon flow, and the
reactions were carried out in air-free conditions.
Characteristic
ꢀꢴꢳꢵꢴꢇꢂ, nm
ꢓꢳꢴꢂ
×104, M-1cm-1
POPOP
NOL
1Н NMR spectra were recorded on a Bruker WP-250 SY
spectrometer working at a frequency of 250.13 MHz or a Bruker
Avance II 300 spectrometer working at a frequency of 300 MHz
utilizing CDCl3 residual signal (7.25 ppm) as the internal standard.
13C NMR spectra were recorded using Bruker Avance II 300
spectrometer at 75 MHz or a Bruker DRX500 spectrometer at 125
MHz.29Si NMR spectra were recorded using Bruker Avance II 300
362
6.00
415
88
388
339
15.06
439, 468
88
,
7.73
439, 468
89
ꢀꢁꢳꢳꢴꢂ, nm
PLQY, %
1.07a
0.83b
0.80a
τ
fast , ns
1
2.83a
1.45b
2.20a
spectrometer working at 60 MHz. In case of H NMR spectroscopy,
τslow
, ns
compounds were studied in 1% CDCl3 solution. In case of 13C or 29Si
NMR spectroscopy, the compounds to be analysed were taken in
the form of 5% solutions in CDCl3.
Ιslow Ιfast
0.42
0.082
0.065
Notes: ꢀꢴꢳꢵꢴꢇꢂ is absorption maximum wavelength; ꢓꢳꢴꢂ is molar extinction
coefficient corresponding to ꢀꢴꢳꢵꢴꢇꢂ; ꢀꢳꢁꢳꢴꢂ is emission maximum wavelength;
ꢶꢷꢸꢹ is photoluminescence quantum yield; ꢺ꣇ꢴꢇ꣏ and ꢺꢇꢻꢆ꣐ are fast and
slow components of the experimentally measured values of PL decay time at
GPC analysis was performed using a Shimadzu LC10Avp series
chromatograph (Japan) equipped with an RID-10Avp refractometer
and SPD-M10Avp diode matrix as detectors and a 7.8×300 mm2
Phenomenex column (USA) filled with Phenogel sorbent with a pour
size of 500 Å. THF was used as an eluent. For thin layer
chromatography(TLC), “Sorbfil” (Russia) plates were used. In the case
of column chromatography, silica gel 60 (“Merck”) was utilized.
MALDI-TOF mass-spectra were registered using an Autoflex II
Bruker spectrometer (resolution FWHM 18000), equipped with a
nitrogen laser (operating wavelength 337 nm, time-of-flight mass
detector working in reflector mode). The accelerating voltage was
20kV. Samples were applied to a polished stainless steel substrate.
Spectra were recorded in positive ion mode. The resulting spectrum
was the sum of 300 spectra obtained at different points of the
sample. 2,5-dihydroxybenzoicacid (DHB, Acros, 99%) and α-cyano-4-
hydroxycinnamic acid (HCCA, Acros, 99%) were used as matrices.
Elemental analysis of C, H elements was carried out using C H
( )
( )
ꢀꢿꣀꣁ = 369 ꢍꣂ ꣃ or 340 ꢍꣂ ꣄ .
of PL for both luminophores as compared to their THF solutions was
observed, albeit this negative effect was less pronounced for NOL:
PLQY decreases from 94% to 88% for POPOP (6% loss), while it
decreases from 91% to 89% for NOL (2% loss). As a result, in
toluene NOL has even higher PLYQ than POPOP. Fluorescence
decay in toluene became bi-exponential for both luminophores (see
Fig. S39 in ESI), while its both (fast and slow), components are faster
for NOL: 1.07 ns and 2.83 ns for POPOP as compared to 0.80 ns and
2.2 ns for NOL exited at 340 nm (in its donor constituent).
Interestingly that impact of the slow component to fluorescence
decay time for POPOP (2.87 ns) is 42%, while influence of the slow
component for NOL (2.20 ns) is limited to 6.5%. This fact makes PL
of NOL in toluene even faster, since 93.5% of its fluorescence decay
comes from the fast component with the characteristic constant of
just 800 ps. To the best of our knowledge, NOL (PTPTP)Si2(2T-Hex)6
is the fastest highly efficient luminophore as compared either to
that of commonly used or state-of-the-art inorganic luminophores,
and to organic luminophores having high PLQY.19
analyzer CE1106 (Italy). The settling
using BaCl
2
Nautomatic
titration
was applied to analyse
sulphur. Content of Br element was
determined by visual titration technique using Hg(NO3)2 and
diphenylcarbazone as indicators. Spectrophotometry technique was
used for the Si analysis. Experimental error for the elemental
analysis was within 0.30-0.50%.
Thermogravimetric analysis was carried out in dynamic mode in
30 ÷ 900°C interval using Mettler Toledo TG50 system equipped
with M3 microbalance allowing measuring the weight of samples in
1 - 150 mg range with 1 μg precision. Heating/cooling rate was
chosen to be 10 °C/min. Every compound was studied twice: in air
and in nitrogen flow of 200 mL/min. DSC scans were obtained with
Mettler Toledo DSC30 system with 10°C/min heating/cooling rate in
temperature range of +20 - +290°C. Nitrogen flow of 50 mL/min
was used.
3. Experimental
3.1 Materials and methods
Thiophene, 1.6 M and 2.5 M n-butyllithium (n-BuLi) solutions in
hexane, 1-bromohexane, 2-hexylthiophene, N-bromosuccinimide
(NBS), magnesium powder, [1,1′-bis(diphenylphosphino)ferrocene]
palladium(II)
1,2-dibromoethane,
Pd(PPh3)4, 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane
dichloride
Pd(dppf)Cl2,
1,4-dibromobenzene,
Optical properties of the compounds synthesized were
investigated by UV-Vis absorption and PL spectroscopy in a form of
THF (UV-grade) dilute (10-5 M for absorption and 10-6 M for PL)
solutions using standard 10 mm photometric quartz cuvettes.
Absorption profiles were recorded on a Shimadzu UV-2501PC
spectrophotometer (Japan) in the spectral region from 190 to 800
nm. PL spectra were recorded at elaborated and prepared in ISPM
RAS scanning spectrofluorimeter ALS-01M; its detailed
characteristics can be found elsewhere.14 The fluorescence intensity
was measured in the mode of single photons counting on the
tetrakis(triphenylphosphine)palladium(0)
(IPTMDOB, Sigma–Aldrich Co.) were used without further
purification. Tetraethoxysilane (Penta-91, Russia) and thionyl
chloride (Chimmed, Russia) were distilled prior to use. 5-hexyl-2,2’-
bithiophene (2T-Hex),20 (4-bromophenyl)trimethylsilane 21 and 5-
hexyl-5'-(trimethylsilyl)-2,2'-bithiophene (TMS-2T-Hex)14
were
synthesized according to procedures published elsewhere for these
or similar compounds. THF and diethyl ether (Et2O) were dried over
CaH2 and distilled, DMF was dried over BaO and distilled. Ethanol
6 | J. Mater. Chem. C, 2016, 8, 1-10
This journal is © The Royal Society of Chemistry 2016
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 7 of 10
View Article Online
DOI: 10.1039/C6TC00979D
Journal of Materials Chemistry C
ARTICLE
consecutive time intervals. PLQY was determined by comparison phase was separated, washed with water, and dried over sodium
with the known PLQY of fluorescent standards according to a sulfate. The solvent was evaporated to give 2.03 g (98%) of white
technique described elsewhere. 22 Five standards were used: crystals, containing 89% of PinB-TPT-BPin and 11% of
p-terphenyl, 2,5-diphenyloxazole, anthracene, POPOP and minosubstituted by-product TPT-BPin (GPC, see Fig.S1 in ESI). The
rhodamine 6G. The resulting quantum yields are the averages of product was used in the subsequent synthesis without further
comparison to all five standards. In all cases the optical density of purification. 1H NMR (300 MHz, CDCl3): δ 7.65 (s, 4H), 7.57 (d, J =
the solutions used for the measurements of PLQY did not exceed 3.7, 2H), 7.36 (d, J = 3.5, 2H), 1.36 (s, 24 H). 13C NMR (125 MHz,
0.05 in a 10 mm thick quartz cuvette. Relative accuracy of the PLQY CDCl3): δ 150.59, 138.22, 133.68, 126.55, 124.55, 84.16, 24.75.
measurements done under the same conditions are +/-0.5%.
(4-bromophenyl)triethoxysilane (BrPhSi(OEt)3). A solution of 1,2-
Picosecond luminescence lifetimes were measured using a dibromoethane (19 mL) in diethyl ether (165 mL) was added
spectrofluorimetric system FluoroLog-3 (Horiba Scientific) equipped dropwise through a dropping funnel to a suspension of magnesium
with solid-state pulsed Nano LEDs emitting at 310, 340 and 369 nm. powder (5.46 g, 0.23 mol) in diethyl ether (15 mL) under continuous
Relative accuracy of the lifetime measurements done under the stirring. The solution was refluxed during 1 h. As a result, diethyl
same conditions were +/-0.005 ns.
ether solution of MgBr2*Et2O complex was formed at the bottom as
Spatial and electronic structures of the luminophores under a viscous grey liquid.
investigation were simulated using the calculations “from the first
1,4-dibromobenzene (48.94 g, 0.2 mol) was dissolved in THF
principles”. The molecules involved were PTPTP, TMS-PTPTP-TMS, (900 mL) in a separate three-neck flask. The solution was cooled to
TMS-2T-CH3 and (PTPTP)Si2(2T-CH3)6, the latter two being the temperature below -70oC and 83 mL of 2.5 M n-BuLi solution in
model structures for TMS-2T-Hex and NOL, respectively, with the hexane (0.21 mol) were added dropwise maintaining the reaction
methyl, rather than hexyl, substituents. The density functional mixture temperature below -60oC. Then the solution was stirred
theory (DFT) B3LYP/6-31G[d] approximation23 was used throughout during
the calculations, as implemented in the ORCA quantum chemistry MgBr2*Et2O complex as described above was added in one portion.
2 h. Then freshly prepared diethyl ether solution of
24
package.
optimization was followed by the TD DFT calculation over the was allowed to warm to room temperature under vigorous stirring.
For each molecule the unconstrained geometry After that the cooling bath was removed and the reaction mixture
optimized structure for the 16 lowest energy excited states using
the Tamm-Dancoff approximation (TDA).
A solution of tetraethoxysilane (275 mL, 1.24 mol) in THF (250
mL) was added dropwise to the ice cooled reaction mixture. The
cooling was removed and the solution was left to warm to room
temperature and subsequently refluxed until the solution became
clear. After that a saturated water solution of ammonium chloride
was added dropwise under vigorous stirring. The water layer was
rejected and the organic layer was extracted twice with toluene and
washed with distilled water, dried over Na2SO4 and evaporated
using rotovapour. The product was filtered through a paper filter
and distilled off (104±1оС, 0.64-0.65 mbar). Pure (97% GC) product
was isolated as a colourless liquid (16.54 g, 27.6 %). 1H-NMR (250
MHz, CDCl3): 7.52 (s, 4H), 3.85 (q, J = 7.0 Hz, 6H), 1.23 (t, J = 7.0 Hz,
9H).
3.2 Synthetic procedures
1,4-bis(2-thienyl)benzene (TPT). A solution of 2-bromothiophene
(14.51 g, 89 mmol) in THF (90 mL) was added dropwise to a
dispersion of magnesium powder (2.25 g, 94 mmol) in THF (10 mL).
The reaction mixture was stirred under reflux over 1 hour to yield
2-thienylmagnesium bromide. A separate three-neck flask was
charged with 1,4-dibromobenzene (10 g, 42 mmol), Pd(dppf)Cl2
(0.45 g, 0.6 mmol) and THF (150 mL). Freshly prepared solution of
2-thienylmagnesium bromide was added dropwise through
a
dropping funnel maintaining the reaction mixture temperature
within 0-10oC. The cooling bath was removed and the reaction
mixture was stirred at room temperature overnight. The desired
compound TPT was isolated by means of Et2O/water extraction,
recrystallization from toluene followed by column chromatography
(4-bromophenyl)trichlorosilane (BrPhSiCl3). A Claisen flask was
charged with 16.54 g (52 mmol) of BrPhSi(OEt)3, 30 mL (0.413 mol)
SOCl2 and a catalytic amount (1-2 drops) of DMF. The mixture was
stirred at 75oC over ca. 100 h. The pure (94% GC) product was
1
1
distilled off the reaction mixture (12.9 g, 86%). H NMR (300 MHz,
(eluent toluene) to yield 7.9 g (77%) of pure product. H NMR (300
CDCl3): δ 7.65 (s, 4H). 13C NMR (125 MHz, CDCl3): δ 134.57, 131.90,
130.32, 128.22. 29Si-NMR (60 MHz, CDCl3): δ -1.15.
MHz, CDCl3): δ 7.62 (s, 4H), 7.33 (dd, J1 = 3.7 Hz, J2= 0.9 Hz, 2H), 7.28
(dd, J1= 4.9 Hz, J2= 0.9 Hz, 2H), 7.08 (dd, J1 = 4.9 Hz, J2= 3.7 Hz,
2H).13C NMR (125 MHz, CDCl3): δ 144.09, 133.73, 128.05, 126.42,
124.88, 123.16.
4-bromophenyl[tris(5’-hexyl-2,2’-bithien-5-yl)]silane (BrPhSi(2T-
Hex)3). A solution of 2T-Hex (12 g, 48 mmol) in THF (400 mL) was
cooled to -70oC and 1.6 M n-BuLi in hexanes (30 mL, 48 mmol) was
added dropwise. The solution was stirred over 30 minutes at -75oC.
The cooling was removed, and the solution was allowed warm to
room temperature and subsequently cooled to temperature below
-80oC. After that freshly distilled BrPhSiCl3 (4.34 g, 15 mmol) was
added in one portion. The reaction mixture was stirred over ca. 30
minutes and warmed to room temperature. 3 mL of 1:1 mixture of
distilled water and THF were added to terminate the reaction. The
product was isolated by Et2O/H2O extraction and purified by column
chromatography (eluent petroleum ether) as a thick yellowish liquid
1,4-bis[5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolane-2-yl)thiophene-
2-yl]benzene (PinB-TPT-BPin). TPT (1.0 g, 4.1 mmol) dissolved in
THF (100 mL) was cooled to -20oC. After that 2.5 M solution of
n-BuLi in hexanes (3.4 mL, 8.0 mmol) was added dropwise, and the
reaction mixture was stirred during 1 hour at -20oC. After that the
temperature was allowed to rise to 10oC, then lowered to 0oC, and
IPTMDOB (1.6 mL, 8.0 mmol) was added to the reaction mixture.
The solution was stirred at 0oC during 15 minutes, warmed to 23oC.
After completion of the reaction, 300 mL of diethyl ether and 200
mL of ice water containing 4 mL of 1 N HCl were added. The organic
1
(9.27 g, 65%). H NMR (300 MHz, CDCl3): δ 7.57 (s, 4H), 7.30 (d, J =
This journal is © The Royal Society of Chemistry 2016
J. Mater. Chem. C, 2016, 8, 1-10 | 7
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 8 of 10
View Article Online
DOI: 10.1039/C6TC00979D
ARTICLE
Journal of Materials Chemistry C
3.7 Hz, 3H), 7.22 (d, J = 3.7 Hz, 3H), 7.05 (d, J = 3.7 Hz, 3H), 6.68 (d, J {4-[5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)thiophen-2-
= 3.7, 3H), 2.80 (t, J = 7.6, 6H), 1.68 (m, 6H), 1.46-1.24 (overlapped yl]phenyl}(trimethyl)silane (TMS-PT-BPin). A 1.6 M solution of
peaks, 18H), 0.90 (t, J = 6.7 Hz, 9H).13C NMR (125 MHz, CDCl3): δ n-butyl lithium (4.0 mL, 6.45 mmol) in hexane was added dropwise
146.16, 146.01, 139.33, 137.03, 134.13, 132.56, 131.30, 130.62, to a solution of TMS-PT (1.5 g, 6.45 mmol) in anhydrous THF (40
125.64, 124.88, 124.38, 124.16, 31.53, 31.51, 30.15, 28.70, 22.55, mL), keeping the temperature below -70 °C. The reaction mixture
14.06. 29Si NMR (MHz, CDCl3):
δ –29.99. Anal. calcd. for was stirred for 30 min at -75 °C, the cooling was removed, and the
C48H55BrS6Si: C, 61.84; H, 5.95, Br, 8.57, S, 20.64; Si, 3.01 Found: C, temperature was allowed to rise to 0 °C. Then it was lowered again
61.75; H, 6.06, Br, 8.45, S, 20.35; Si, 2.85. MALDI MS: found m/z to -75°C, and IPTMDOB (1.2 g, 6.45 mmol) was added in one
932.89; calculated for [M+H]+ 933.37.
portion. The reaction mixture was stirred for 1 h at -78°C, the
cooling was removed, and stirring was continued for 1 h. After
4-bis[5-{4-[tris(5’-hexyl-2,2’-bithien-5-yl)silyl]phenyl}thiophene-2-
yl]benzene (NOL). 50 mL of toluene, 8 mL of ethanol and 8 mL of completion of the reaction, 300 mL of diethyl ether and 200 mL of
2M Na2CO3 (0.016 mol) aqueous solution were added to a mixture ice water containing 6 mL of 1 M HCl were added. The organic
of BrPhSi(2T-Hex)3 (3.07 g, 3.0 mmol), PinB-TPT-BPin (0.815 g, 1.6 phase was separated, washed with water, and dried over sodium
mmol) and Pd(PPh3)4 (0.124 g, 0.1 mmol) under vigorous stirring. sulfate. The solvent was evaporated to give 2.27 g (90%) of white
The mixture was stirred under reflux during 16h and cooled down crystals, containing 90% of TMS-PT-BPin and 10% of the initial
to room temperature. The bottom water-based layer was separated compound TMS-PT (GPC, see Fig.S3 in ESI). The product was used in
with a syringe and rejected. The remaining organic solvent was the subsequent synthesis without further purification. MALDI MS:
evaporated, the residual mixture was diluted with toluene and found m/z 358.378; calculated for [M]+ 358.205. 1H-NMR (300 MHz,
passed through a silica gel to remove the catalyst. Toluene was CDCl3): δ 7.64 (d, J = 8.2 Hz, 2H), 7.61 (d, J = 3.6 Hz, 1H), 7.55 (d, J =
evaporated from the filtrate and the product was purified by 8.2 Hz, 2H), 7.40 (d, J = 3.6, 1H), 1.36 (s, 12H), 0.31 (s, 9H). 13C-NMR
column chromatography on silica gel (eluent toluene - petroleum (75 MHz, CDCl3): δ 151.30, 140.28, 138.11, 134.45, 133.89, 133.84,
ether mixture 1:3) in a 34% yield as a yellow solid. mp: 118oC, ꢀHm
=
125.36, 124.82, 84.10, 24.73, -1.20. 29Si-NMR (60 MHz, CDCl3):
43.11 J g-1,Tg: -2oC, ΔCp = 0.229 J g-1K-1. 1H NMR (300 MHz, CDCl3): δ δ -3.88.
7.69 (d, J = 8.1 Hz, 4H), 7.67 (d, J = 8.1 Hz, 4H), 7.64 (s, 4H), 7.39- 1,4-bis[5-{4-(trimethylsilyl)phenyl}thiophene-2-yl]benzene (TMS-
7.29 (overlapped peaks, 10H), 7.23 (d, J = 3.5 Hz, 6H), 7.03 (d, J = PTPTP-TMS). 40 mL of toluene, 4 mL of ethanol and 3.1 mL of 2M
3.6 Hz, 6H), 6.68 (d, J = 3.4 Hz, 6H), 2.75 (t, J = 7.5 Hz, 12H), 1.70 (m, Na2CO3 (6.2 mmol) aqueous solution were added to a mixture of
12H), 1.45 – 1.19 (overlapped peaks, 36H), 0.84 (t, J = 6.7 Hz, TMS-PT-BPin (2.20 g, 6.15 mmol), 1,4-dibromobenzene (0.61 g,
18H).13C NMR(125 MHz, CDCl3): δ 146.05, 146.85, 145.85, 143.61, 2.56 mmol) and Pd(PPh3)4 (0.1 g, 0.09 mmol), and the mixture was
143.24, 139.26, 136.13, 136.02, 134.25, 133.34, 132.62, 131.18, heated to reflux. The reaction mixture was stirred under reflux for
125.98, 125.02, 124.86, 124.38, 124.17, 124.10, 31.54, 31.51, 30.15, 14 h, when the reaction yield achieved 82% (according to GPC).
28.7, 22.55, 14.06. 29Si NMR (MHz, CDCl3): δ –30.31. Calcd. for Upon cooling to 20 °C, a yellow precipitate appeared. The filtrate
C110H118S14Si2: C, 67.92; H, 6.11; S, 23.08; Si, 2.98. Found: C, 68.14; was removed, and the product was purified by recrystallization
H, 6.11; S, 22.74; Si, 2.82. MALDI MS: m/z calculated for [M]+ from toluene followed by sublimation to give pure TMS-PTPTP-TMS
1945.195. The compound presumably undergoes decomposition as a yellow solid (0.74 g, 53%). mp: 276oC. MALDI MS: found m/z
under ionization conditions as no peak with m/z value close to 1945 538.915; calculated for [M]+ 538.110. 1H NMR (250 MHz, CDCl3): δ
was revealed. Peaks with m/z 1696.10 ([M -2T-Hex -H-]+: 1695.78) 7.64 (s, 4H), δ 7.62 (d, J = 8.1 Hz, 4H), 7.55 (d, J = 8.1 Hz, 4H), 7.31 (s,
and 775.08 ([Si(2T-Hex)3 – H-]+: 775.3219) were registered.
[4-(2-thienyl)phenyl](trimethyl)silane (TMS-PT).
4H), 0.30 (s, 18H). 13C NMR (125 MHz, CDCl3): δ 144.14, 143.38,
A
solution of 140.10, 134.76, 133.97, 133.71, 126.14, 125.05, 124.23, 124.13, -
2-bromothiophene (3.91 g, 24.0 mmol) in anhydrous THF (30 mL) 1.15. 29Si NMR (60 MHz, CDCl3): δ -3.88. Anal. Calcd for C32H34S2Si2:
was added dropwise to a suspension of magnesium (0.6 g, 25.1 C, 71.32; H, 6.36; S, 11.90; Si, 10.42. Found: C, 71.33; H, 6.39; S,
mmol) in THF (5 mL). The reaction mixture was refluxed during 1 h 11.70; Si, 10.29.
to yield 2-thienylmagnesium bromide, cooled to room temperature
Full characterization of the precursors and final compounds can
and added dropwise to an ice cooled solution of (4-bromophenyl) be found in the ESI.
trimethylsilane (5.00 g, 21.8 mmol) and Pd(dppf)Cl2 (0.127 g, 0.24
mmol) in anhydrous THF (50 mL). Then the cooling was removed,
4. Conclusions and outlook
and stirring was continued for 5 h at room temperature. Afterwards
the reaction mixture was poured into water (500 mL), and extracted In this work we synthesized a novel nanostructured organosilicon
twice with diethyl ether (400 mL). The organic phase was separated, luminophore (NOL) (PTPTP)Si2(2T-Hex)6 and investigated in details
washed with water, dried over sodium sulfate and evaporated. The its optical properties both theoretically and experimentally. For this
product was purified by column chromatography on silica gel purpose herein we introduce for the first time TD DFT method as an
(eluent toluene) to give pure TMS-PT (5.04 g, 99%). MALDI MS: efficient tool for NOLs electronic and optical properties explanation
found m/z 232.416; calculated for [M]+ 232.040. 1H NMR (300 MHz, and prediction. As a result we conclude that the central light-
CDCl3): δ 7.63 (d, J = 8.2 Hz, 2H), 7.56 (d, J = 8.2 Hz, 2H), 7.35 (dd, J1 emitting PTPTP unit within the NOL experiences a strong inductive
= 3.6, J2 = 1.2, 1H), 7.29 (dd, J1 = 5.2, J2 = 1.2, 1H), 7.09 (dd, J1 = 5.2, influence of the outer donor fragments located in a close proximity
J2 = 3.6, 1H), 0.31 (s, 9H). 13C NMR (125 MHz, CDCl3): δ 144.43, (1.5 nm, see Fig. S40 in ESI) to the central acceptor unit. These
139.66, 134.68, 133.86, 127.97, 125.17, 124.83, 123.11, -1.16. 29Si- interactions provoke an efficient increase in the oscillator strength
NMR (60 MHz, CDCl3): δ -3.95.
of the NOL molecule compared to the initial PTPTP acceptor core
8 | J. Mater. Chem. C, 2016, 8, 1-10
This journal is © The Royal Society of Chemistry 2016
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 9 of 10
View Article Online
DOI: 10.1039/C6TC00979D
Journal of Materials Chemistry C
ARTICLE
end even to its organosilicon derivative TMS-PTPTP-TMS. This trend
was revealed both experimentally and computationally in PL decay
acceleration along with an increase in molar extinction coefficient.
Furthermore, it was found that efficient shielding of the emitting
core from the surrounding solvent molecules by donor outer
fragments leads to a rise in fluorescence decay rate constant and
consequently to an unusual rise in PLQY.
5
(a) J. A. Brown, B. L. Goldblum, L. A. Bernstein, et.al., J. Appl.
Phys., 2014, 115, 193504; (b) E. Auffray, O. Buganov, A.
Fedorov, M. Korjik, P. Lecoq, G. Tamulaitis, S. Tikhomirov, A.
Vasil’ev, J. Phys. Conf. Ser., 2015, 587, 012056; (c) H. A. Yemam,
A. Mahl, U. Koldemir, T. Remedes, S. Parkin, U. Greife, A.
Sellinger, Sci. Rep., 2015, 5, 13401; (d) J. Zhu, Y. Ding, J. Zhu, D.
Qi, M. Su, Y. Xu, Y. Bi, R. Lin and L. Zhang, Nucl. Instrum. Meth.
A, 2015, 817, 30-34.
It was found that (PTPTP)Si2(2T-Hex)6 representing NOL of type
II exhibits the improved light harvesting efficiency as compared to
NOLs of type I reported earlier due to a larger D : A ratio (6 vs 4).9
6
7
(a) S. Heller and P. T. Zanzonico, Semin. Nucl. Med., 2011, 41,
166; (b) R. J. Hu, C. Kim, B. Hong M. Jo, K. S. Lee, S. Park and K.
S. Sim, J. Korean Phys. Soc., 2009, 54, 586.
ꢡ
ꢜꢝꢞ of the former is 1.4×105 M-1 cm-1, which is ~1.5 times higher in
comparison to the best values for the latter and is close to those of
inorganic Q-dots.25 Moreover, the NOL reported combines such
unique photophysical characteristics as high pseudo Stokes shift of
101 nm, emission spectrum lying entirely in the visible range with
maxima at 439 and 469 nm, and extremely shot PL decay time of
0.80 – 0.90 ns along with very high PLQY of 88-91%. Owing to such
properties, it demonstrates a great potential for application in
various fields of organic optoelectronics and photonics as well as
for the development of new generation of plastic and liquid
scintillation detectors with improved timing resolution required by
further modification of current and construction of novel
megascience equipment such as LHC and others used in a search for
novel elementary particles, cosmic rays and dark matter.26
(a) S. Stapnes, Nature, 2007, 448, 290; (b) M. Conti, Eur. J. Nucl.
Med. Mol. Imaging, 2011, 38, 1147; (c) J. Seco, B. Clasie and M.
Partridge, Phys. Med. Biol., 59, 2014, 303; (d) S. Seifert, H. T. van
Dam and D. R. Schaart, Phys. Med. Biol., 2012, 57, 1797.
Yamaguchi, Y. Matsubara, T. Ochi, T. Wakamiya and Z.-I.
Yoshida, J. Am. Chem. Soc., 2008, 130, 13867.
8
9
(a) S. A. Ponomarenko, N. M. Surin, O. V. Borshchev et.al., Sci.
Rep., 2014, 4, 6549; (b) S. A. Ponomarenko, N. M. Surin, O. V.
Borshchev, M. S. Skorotetcky and A. M. Muzafarov, Proc. of
SPIE, 2015, 9545, 954509; (c) M. S. Skorotetcky, O. V.
Borshchev, N. M. Surin, I. B. Meshkov, A. M. Muzafarov and S.
A. Ponomarenko, Silicon, 2015, 7, 191; (d) Yu. N. Luponosov, N.
M. Surin, D. K. Susarova, M. I. Buzin, D. V. Anokhin, D. A. Ivanov,
P. A. Troshin and S. A. Ponomarenko, Org. Photonics Photovolt.
2015, 3, 148.
Acknowledgements
10
(a) Yu. N. Luponosov, S. A. Ponomarenko, N. M. Surin, O. V.
Borshchev, E. A. Shumilkina and A. M. Muzafarov, Chem.
Mater., 2009, 21, 447; (b) O. V. Borshchev, S. A. Ponomarenko,
E. A. Kleymyuk, Yu. N. Luponosov, N. M. Surin and A. M.
Muzafarov, Rus. Chem. Bull., 2010, 59, 797.
This work was supported by Russian Foundation for basic
Research (grants 13-03-01315 and 13-03-12451). O.V.B. thanks
Foundation of President of the Russian Federation (projects
МК-6501.2015.3) for financial support. Authors thank P.V.
Dmitryakov (NRC Kurchatov Institute) for TGA and DSC
measurements.
11
12
T. Förster, Discuss. Faraday Soc., 1959, 27, 7.
(a) K. Feldman, Nanoscale, 2011, 3, 1947; (b) P. Anilkumar, X.
Wang, L. Cao, S. Sahu, J.-H. Liu, P. Wang, K. Korch, K. N. Tackett
II, A. Parenzan and Y.-P. Sun, Nanoscale, 2011, 3, 2023; (c) C.
Wu and D. T. Chiu, Angew. Chem. Int. Ed. 2013, 52, 2.
(a) S. A. Lee, S. Hotta and F. Nakanishi, J. Phys. Chem. A, 2000,
104, 1827-1833; (b) T. Yamao, Y. Taniguchi, K. Yamamoto, T.
Miki, S. Ota, S. Hotta, M. Goto and R. Azumi, Jpn. J. Appl. Phys.,
2007, 46, 7478; (c) S. Hotta and T. Yamao, J. Mater. Chem.,
2011, 21, 1295.
References
1
(a) J. Clark and G. Lanzani, Nat. Photonics, 2010, 4, 438; (b) G. C.
13
La Rocca, Nat. Photonics, 2010, 4, 343; (c) C. Santato, F. Cicoira
and R. Martel, Nat. Photonics, 2011, 5, 392.
2
(a) Y. Sun, G. C. Welch, W. L. Leong, C. J. Takacs, G. C. Bazan and
A. J. Heeger, Nat. Materials, 2012, 11, 44; (b) S. B. Darling and F.
You, RSC Adv., 2013, 3, 17633; (c) J. Hodgkiss, G. Conboy, G.
Hutchings at.al., Faraday Discuss., 2014, 174, 341; (d) J. Huang,
C.-Z. Li, C.-C. Chueh, S.-Q.Liu, J.-S. Yu, and A. K.-Y. Jen, Adv.
Energy Mater., 2015, 1500406.
14
E. A. Shumilkina, O. V. Borshchev, S .A. Ponomarenko, N. M.
Surin, A. P. Pleshkova and A. M. Muzafarov, Mendeleev
Commun., 2007, 17, 34.
15
16
17
18
3
V. P. Ananikov, L. L. Khemchyan, Y. V. Ivanova et.al., Russ. Chem.
Rev., 2014, 83, 885.
(a) T. Baumann, A. M. Amthor, D. Bazin, et.al., Nature, 2007,
449, 1022; (b) D. Yu. Akimov, A. V. Akindinov, I. S. Alexandrov,
at.al, Nucl. Instrum. Meth. A, 2012, 695, 403; (c) N. Surin, O.
Borshchev, S. Ponomarenko, M. Skorotetcky, B. Lubsandorzhiev,
N. Lubsandorzhiev and A. Pakhorukov, Nucl. Instrum. Meth. A,
2014, 766, 160.
P. G. Taylor, A. R. Bassindale, Y. El Aziz, M. Pourny, R. Stevenson,
M. B. Hursthouse and S. J. Coles, Dalton Trans., 2012, 41, 2048.
D. V. O. O’Connor and D. Phillips, Time-correlated Single Photon
Counting, Academic Press, London, 1984.
4
(a) J. K. Ahn, S. Chebotaryov, J. H. Choi, at. al., Phys. Rev. Lett.
2012, 108, 191802; (b) J. Maneira (for the SNO+ Collaboration),
J. Phys. Conf. Ser., 2013, 447, 012065.
(a) R. Alford, H. M. Simpson, J. Duberman, G. C. Hill, M. Ogawa,
C. Regino, H. Kobayashi and P. L. Choyke, Mol. Imaging, 2009, 8,
341; (b) M. Heilemann, S. van de Linde, A. Mukherjee andM.
Sauer, Angew.Chem. Int. Ed., 2009, 48, 6903.
19
(a) H. Sumikura, E. Kuramochi, H. Taniyama and M. Notomi, Sci.
Rep., 2014, 4, 5040; (b) K. A. Walther, B. Papke, M. B. Sinn, K.
This journal is © The Royal Society of Chemistry 2016
J. Mater. Chem. C, 2016, 8, 1-10 | 9
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry C
Page 10 of 10
View Article Online
DOI: 10.1039/C6TC00979D
ARTICLE
Journal of Materials Chemistry C
Michel and A. Kinkhabwala, Mol. BioSyst., 2011, 7, 322; (c) P.
Sarder, D. Maji and S. Achilefu, Bioconjugate Chem., 2015, 26,
963.
20
21
S. Ponomarenko and S. Kirchmeyer, J. Mater. Chem., 2003, 13,
197.
V. A. Postnikov, Y. I. Odarchenko, A. V. Iovlev, V. V. Bruevich, A.
Y. Pereverzev, L. G. Kudryashova, V. V. Sobornov, L. Vidal, D.
Chernyshov, Y. N. Luponosov, O. V. Borshchev, N. M. Surin, S. A.
Ponomarenko, D. A. Ivanov and D. Y. Paraschuk, Cryst. Growth
Des., 2014, 14, 1726.
22
N. M. Surin, O. V. Borshchev, Yu. N. Luponosov, S. A.
Ponomarenko and A. M. Muzafarov, Russ. J. Phys. Chem., 2010,
84, 1979.
23
24
25
R. H. Hertwig and W. Koch, Chem. Phys. Lett. 1997, 268, 345.
F. Neese, Wiley Interdiscip. Rev.: Comput. Mol. Sci., 2012, 2, 73.
U. Resch-Genger, M. Grabolle and S. Cavaliere-Jaricot, Nat.
Methods, 2008, 5, 763.
26
C. Joram, G. Haefeliand and B. Leverington, J. Inst., 2015, 10,
C08005.
A table of Contents entry:
For the first time successful experimental and theoretical treatment of
Nanostructured Organosilicon Luminophores (NOLs) with unique optical
properties is considered.
10 | J. Mater. Chem. C, 2016, 8, 1-10
This journal is © The Royal Society of Chemistry 2016
Please do not adjust margins