Intriguing Indium-salen Complexes as Multicolor Luminophores

Article abstract of DOI:10.1021/acs.inorgchem.6b02797

The series of novel salen-based indium complexes (3-^tBu-5-R-salen)In-Me (3-^tBu-5-R-salen = N,N′-bis(2-oxy-3-tert-butyl-5-R-salicylidene)-1,2-diaminoethane, R = H (1), ^tBu (2), Br (3), Ph (4), OMe (5), NMe₂ (6))

Full text of DOI:10.1021/acs.inorgchem.6b02797

Article
pubs.acs.org/IC
Intriguing Indium-salen Complexes as Multicolor Luminophores
Seon Hee Lee,†,⊥ Nara Shin, § Sang Woo Kwak, Kyunglim Hyun, Won Hee Woo, Ji Hye Lee,
‡,⊥
§
§
§
‡
‡
∥
,§
,‡
Hyonseok Hwang, Min Kim, Junseong Lee, Youngjo Kim,* Kang Mun Lee,*
,†
and Myung Hwan Park*
†
Department of Chemistry Education, Chungbuk National University, Cheongju, Chungbuk 28644, Republic of Korea
‡
Department of Chemistry and Institute for Molecular Science and Fusion Technology, Kangwon National University, Chuncheon,
Gangwon 24341, Republic of Korea
§
Department of Chemistry, Chungbuk National University, Cheongju, Chungbuk 28644, Republic of Korea
∥Department of Chemistry, Chonnam National University, Gwangju 61186, Republic of Korea
*
S Supporting Information
t
ABSTRACT: The series of novel salen-based indium complexes (3- Bu-5-R-salen)In-Me
t
(
3- Bu-5-R-salen = N,N′-bis(2-oxy-3-tert-butyl-5-R-salicylidene)-1,2-diaminoethane,
t
t
R = H (1), Bu (2), Br (3), Ph (4), OMe (5), NMe (6)) and [(3- Bu-5-NMe -
2
3
−
salen)In-Me](OTf)2 (7; OTf = CF SO ) have been synthesized and fully
3
3
characterized by NMR spectroscopy and elemental analysis. All indium complexes
1
3
−7 are highly stable in air and even aqueous solutions. The solid-state structures for
−5, which were confirmed by single-crystal X-ray analysis, exhibit square-pyramidal
geometries around the indium center. Both the UV/vis absorption and PL spectra of
1
−7 exhibit significant intramolecular charge transfer (ICT) transitions based on
the salen moieties with systematically bathochromic shifts, which depend on the
introduction of various kinds of substituents. Consequently, the emission spectra of
these complexes cover almost the entire visible region (λem = 455−622 nm).
INTRODUCTION
the fundamental nature of the emissions induced by these
complexes in detail.
■
Fluorescent/phosphorescent organometallic complexes have
been widely used as efficient functional materials in organic
light-emitting diodes (OLEDs) and photovoltaic cells because of
RESULTS AND DISCUSSION
■
1
−6
t
their outstanding optical properties and high thermal stability.
Synthesis and Characterization. The synthesis of (3- Bu-
5-R-salen)In-Me complexes (1−6) based on ligands L1−L6
is shown in Scheme 1. The salen-type ligands L1−L6 were
analogously synthesized, according to previously reported
The luminescent properties of these luminophores can be
controlled by a systematic modulation of the ligand frameworks.
The incorporation of various substituents into the ligand as a
scaffold for transition-metal complexes can induce fascinating
photophysical properties, such as emission color tuning and
quantum efficiency modifications, leading to an expansion of
2
2,23
procedures.
The indium luminophores 1−6 were obtained
in high yield (63−86%) by the reaction of InMe precursors
with the respective salen ligands in toluene.
3
7−9
their use as promising luminescent materials.
In particular,
InCl
based indium complexes; however, InMe
from the aspects of mild reaction conditions and better
yield with no side product. InCl gave inseparable mixtures
of reaction products. Additionally, the di-ionic complex 7 was
3
and InMe
3
could be applied to the synthesis of salen-
organometallic complexes based on group 13 metals such as
aluminum and gallium have been recently reported as prominent
optoelectronic materials due to their excellent electronic and
3
was more convenient
3
10−13
photophysical properties.
Since the first discovery of
readily produced by methylation of the NMe substituents in the
tris(8-hydroxyquinolinato)aluminum (Alq ) by Tang and
2
3
14
neutral complex 6 with an excess of MeOTf (Scheme 1, 95%).
Although the neutral complexes 1−6 showed high solubility in
common organic solvents such as THF, toluene, and chloroform,
the di-ionic complex 7 was only soluble in polar MeCN and
DMSO. Importantly, in contrast to group 13 based salen
VanSlyke in 1987, a wide range of aluminum-based complexes
1
1,15−23
as prominent optoelectronic materials have been developed.
In a continuous effort to explore a novel class of color-tunable
luminophores, we investigated salen-based indium complexes,
which are heavier congener systems of well-known luminescent
2
3,26
24,25
complexes such as Al-salen complexes with Al−Me bonds,
Al-salen complexes.
To the best of our knowledge, there
complexes 1−7 with In−Me bonds were highly stable in air and
Received: November 21, 2016
have been no reported studies on monomeric indium complexes
that display multicolor emission features due to the simple altera-
tion of their substituents. Therefore, we have prepared a series
of indium-based complexes with salen ligands and investigated
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.6b02797
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Inorganic Chemistry
Article
Scheme 1. Synthetic Routes for Indium Complexes 1−7,
Containing Modified salen Ligands
(red, 6), which covered the entire visible region (Figure 2b).
Importantly, complex 7, which was produced by methylation of
the NMe -appended 6, exhibited a considerable emission shift
2
of 167 nm, which is similar to the previous results obtained for
23
Al-salen complexes. These optical findings are correlated with
27
the respective Hammett constants except for 3 and 4; this is
23
similar to what was observed in other complexes. The orders of
the emission and absorption maxima for all of the complexes
were identical.
More importantly, the emission spectra of 1−7 clearly
exhibited bathochromic shifts with increasing solvent polarity,
which indicate the presence of polarized excited states for
all of the complexes (Figures S9 and S10 in the Supporting
Information). In addition to the broad nature of the emission
spectra, these results also revealed that the emission features
originated from salen-centered intramolecular charge transfer
(ICT) transitions. Most importantly, due to the observation of
multicolor emission through substituent variation and electronic
modification at the benzene ring in 1−7, the indium complexes
could be considered a novel class of luminophores. Furthermore,
the emission spectra of 1−7 in the solid state showed emission
features that were comparable to those obtained in solution
even aqueous solutions, which were definitely confirmed by
23
1
H NMR experiments for 3 and 4 in THF-d with D O (THF/
8
2
D O (v/v) = 4/1) (Figure S1 in the Supporting Information).
2
1
Compounds 1−7 were fully characterized by H and
1
3
C NMR spectroscopy (Figures S2−S8 in the Supporting
1
Information) and elemental analysis. In particular, the H NMR
spectra of 1−7 clearly showed two multiplets at ca. 3.9 and
(Figure S11 in the Supporting Information). The fluorescence
3
.7 ppm, which correspond to ethylene bridge protons
quantum efficiency (Φ ) of these complexes was in the range of
em
(
−CH CH −), indicating the complete formation of a
2
2
23
0
.10−0.36, which is similar to those of Al-based luminophores
tetradentate [N O ] coordination between indium(III) and
2
2
except for 6 (Φ = 0.01) and 7 (Φ = 0.09). Moreover, the
the salen moiety. In addition, a specific singlet peak attributed
em
em
emission decay lifetime, measured as 0.20−1.1 ns in 1−7,
revealed that the emissions of all the indium complexes were
fluorescent (Figure S12 in the Supporting Information).
to In−CH protons was clearly detected in 1−7 at ca. −0.3 ppm.
3
The carbon signals corresponding to In−CH were observed
3
only in 1 (1.00 ppm), 2 (−0.01 ppm), and 3 (5.13 ppm), despite
the prolonged acquisition times. Furthermore, the molecular
solid-state structures for 3−5 (Figure 1 and Tables S1 and S2 in
the Supporting Information) revealed that the bond between
indium and the methyl group was nearly perpendicular to the
tetradentate plane of the indium center, which indicates a
square-pyramidal geometry around the In center. It was clearly
demonstrated that the values of the trigonality parameter (τ) for
Electrochemical Properties. Cyclic voltammetry (CV)
measurements were performed to get the electrochemical
properties for the In-salen complexes 1−7 (Figure S13 in the
Supporting Information). While complex 6 underwent rever-
sible oxidation, complexes 1−5 and 7 exhibited quasi-reversible
oxidation processes. The measured oxidation potentials and,
thus, the calculated HOMO energy levels for 1−7 largely
depended on the electron-donating ability at the benzene ring
3
−5 are as 0.28, 0.18, and 0.12, respectively.
(Table 1). Consequently, there was a tendency for the HOMO
Photophysical Properties. To get the optical data for
levels for all complexes to be destabilized as the electron-
donating effect of benzene ring gradually increased.
complexes 1−7, UV/vis absorption and photoluminescence
(
PL) experiments were performed in THF solution (Table 1
and Figure 2). Major absorption bands from 360 to 424 nm,
which are attributed to π−π* transitions in the salen moiety,
were observed, and other salen-based transition-metal complexes
have shown similar absorption trends. Among the complexes,
the absorption maximum (λabs = 360 nm) of the cationic
Theoretical Calculations. To clarify the nature of the
electronic transitions and multicolor emission features of
1−7, time-dependent density functional theory (TD-DFT)
calculations (Figures S14−S20 and Tables S3−S16 in the
23
Supporting Information) on the ground state (S
) and the first
0
NMe -appended complex 7 was observed in the highest energy
singlet excited state (S , Figure 3) optimized structures of all
1
3
region. Accordingly, the absorption maxima of these complexes
typically displayed a gradual red shift as the electron-donating
effect of substituents at the benzene ring increased. The PL
spectra of 1−7 were observed from 455 (blue, 7) to 622 nm
complexes were performed with the B3LYP/6-31G(d) basis
sets. To check the effects of the THF solvent, the conductor-
28,29
like polarizable continuum model (CPCM) was also used.
The calculation results for 1−7 in the S state showed that the
0
Figure 1. X-ray crystal structures of 3 (left), 4 (center), and 5 (right) (50% thermal ellipsoids). For clarity, the H atoms and diethyl ether molecules
for 4) are omitted.
(
B
DOI: 10.1021/acs.inorgchem.6b02797
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Inorganic Chemistry
Article
Table 1. Photophysical Data for 1−7
λem/nm
a
b
b
b
a
,
c
d
e
a
compound
λabs /nm (log ε)
λex/nm
cyclohexane
THF
DMSO
solid
Φem
Vox /V
HOMO /eV
τobs /ns
1
2
3
4
5
6
7
363 (4.24)
375 (4.16)
382 (4.01)
388 (4.10)
402 (4.10)
424 (3.78)
371
376
377
388
403
432
473
482
477
502
481
595
450
476
484
486
502
521
622
479
486
491
503
525
625
459
473
479
481
497
499
574
456
0.24
0.36
0.15
0.28
0.10
0.01
0.09
0.50
0.48
−5.30
−5.28
−5.18
−5.13
−4.99
−4.67
−5.35
0.86
1.1
0.38
0.66
1.1
0.33
0.19
1.1
−0.13
0.53
0.20
1.0
360 (4.18)
362
−5
455
c
a
c = 1.0 × 10−5 M in THF. c = 1.0 × 10 M, determined at 298 K. Quinine sulfate (Φ = 0.55) used as a standard. The oxidation onset potential
in DMSO (c = 5.0 × 10 M, scan rate 100 mV s ) with reference to the ferrocene/ferrocenium (Fc/Fc ) redox couple. Calculated from E .
b
d
−4
−1
+
e
ox
Furthermore, on the basis of the theoretical results for the
S1-optimized structures of all the complexes, the major con-
tribution to low-energy emission involved the HOMO-1 →
LUMO transition, except for 6 (HOMO → LUMO+1
transition) and 7 (HOMO → LUMO transition) (Table 2
and Figure 3), indicating the presence of ICT features attributed
to salen-centered π−π* transitions; this was identical with the
phenomena observed for the S -optimized structures of 1−7.
0
Indeed, the broad and intense low-energy emission bands were
also clearly observed in the solid state (Figure S11 in the
Supporting Information). In addition, while the C5 substituents
contribute considerably to the HOMO-1 (1−5) or HOMO
(
6 and 7), the LUMO (1−5 and 7) or LUMO+1 (6) exhibited
negligible contributions at the benzene ring moiety. Notably,
the order (7 > 1 > 2 > 3 > 4 > 5 > 6) of the computed lowest-
energy emission maxima was in complete agreement with that
of the experimentally observed emission bands (Table 1).
From these results, we were convinced that the introduction of
various kinds of substituents in the salen ligand chelated to
indium affects the HOMO or HOMO-1 energy levels, which
can systematically modulate their fluorescence color.
CONCLUSION
■
We have synthesized and fully characterized novel monomeric
indium-salen complexes 1−7 with various substituents at the
benzene ring. These In complexes were highly stable in air
and aqueous solutions. The UV/vis absorption and PL spectra
of 1−7 revealed salen-centered ICT transitions with gradual
bathochromic shifts depending on substituent modification and
electronic effects at the benzene ring, as supported by theoretical
calculations. In particular, the emission spectra of all complexes
cover the entire visible region (λem = 455−622 nm). Ongoing
efforts are underway to develop versatile indium-salen complexes
as promising optoelectronic materials.
Figure 2. (a) UV/vis absorption and (b) PL spectra in THF
−5
(
1.0 × 10 M) for 1−7. The inset gives the emission color observed
under a hand-held UV lamp (λex = 365 nm).
largest contribution (f > 0.7) to low-energy absorptions was
predominantly associated with the electronic transition from
the HOMO-1 to LUMO (Figure S21 in the Supporting
Information). The HOMO-1 for all of the complexes was
mainly localized on the benzene ring moieties (89−93%)
containing C5 substituents, whereas the LUMO was distributed
over the bridging imine group (53−56%) and benzene ring
moieties (43−47%). These findings indicate that low-energy
electronic transitions for 1−7 originate from π−π* electronic
transitions based on salen moieties with a substantial ICT
character between the benzene ring moieties and bridging
imine groups, similar to those observed in salen-based Al
EXPERIMENTAL SECTION
General Considerations. All air- and moisture-sensitive oper-
ations were carried out under an atmosphere of dinitrogen by using
standard Schlenk line and glovebox techniques.
available chemicals were purchased from Aldrich and Alfa Aesar and
used as supplied without any further purification. All solvents were
passed through an activated alumina column and stored over activated
molecular sieves (5 Å). Deuterated solvents such as CDCl , CD CN,
■
3
0,31
All commercially
3
3
and THF-d (Cambridge Isotope Laboratories) were used after storing
8
over activated molecular sieves (5 Å).
Measurements. 1H and 13C NMR analyses were performed at
ambient temperature on a 400 MHz NMR spectrometer using standard
parameters. All chemical shifts are reported in ppm referenced to the
2
3
1
13
complexes. This feature was in agreement with the broad
absorption bands observed for the In-salen complexes 1−7.
signals of residual CDCl (δ 7.24 for H NMR; δ 77.0 for C NMR) or
3
1
13
CD CN (δ 1.94 for H NMR; δ 1.32 and 118.26 for C NMR).
3
C
DOI: 10.1021/acs.inorgchem.6b02797
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Inorganic Chemistry
Article
Figure 3. Frontier molecular orbitals for 1−7 at their first excited singlet state (S ) with their relative energies from DFT calculation (isovalue 0.04).
1
The transition energy (in nm) was calculated using the TD-B3LYP method with 6-31G(d) basis sets.
Table 2. Major Low-Energy Electronic Transitions for 1−7
a 20 mL toluene solution of salen ligands L1−L6 (0.5 mmol) at room
temperature. The reaction mixture was stirred for 12 h, and then the
solvent was removed in vacuo. The crude product was washed with
n-hexane (50 mL), and then drying in vacuo afforded the desired
at Their First Excited Singlet State (S ) Calculated using the
1
a
TD-B3LYP Method with 6-31G(d) Basis Sets
λcalc/nm
fcalc
assignment
products 1−6.
1
Data for 1 (R = H): ivory solid (0.18 g, 70%). H NMR (CDCl ):
1
2
3
4
5
6
7
438.73
451.33
454.46
463.85
513.97
530.41
418.75
0.0154
0.0180
0.0174
0.0685
0.0170
0.0647
0.0882
HOMO-1 → LUMO (99.1%)
HOMO-1 → LUMO (99.3%)
HOMO-1 → LUMO (99.2%)
HOMO-1 → LUMO (97.8%)
HOMO-1 → LUMO (99.4%)
HOMO → LUMO+1 (89.4%)
HOMO → LUMO (98.0%)
3
δ 8.18 (s, 2H), 7.32 (d, J = 8.0 Hz, 2H), 6.91 (d, J = 8.0 Hz, 2H), 6.54
(
(
1
t, J = 12.0 Hz, 2H), 3.86 (m, 2H), 3.70 (m, 2H), 1.45 (s, 18H), −0.30
13
s, 3H, In−CH ). C NMR (CDCl ): δ 170.75, 169.97, 143.07,
3
3
32.90, 131.32, 119.41, 114.26, 55.42, 35.36, 29.38, 1.00 (In−CH ).
3
Anal. Calcd for C H InN O : C, 59.07; H, 6.54; N, 5.51. Found:
25
33
2
2
C, 58.62; H, 6.19; N, 5.28.
Data for 2 (R = Bu): pale yellow solid (0.27 g, 86%). H NMR
t
1
a
(
2
(
1
CDCl ): δ 8.24 (s, 2H), 7.39 (d, J = 4.0 Hz, 2H), 6.86 (d, J = 4.0 Hz,
Singlet energies for the vertical transition calculated at the optimized
3
H), 3.89 (m, 2H), 3.67 (m, 2H), 1.45 (s, 18H), 1.27 (s, 18H), − 0.32
S1 geometries.
13
s, 3H, In−CH ). C NMR (CDCl ): δ 170.88, 168.06, 142.28,
3
3
35.88, 129.49, 128.24, 118.10, 55.50, 35.57, 33.84, 31.39, 29.46,
0.01 (In−CH ). Anal. Calcd for C H InN O : C, 63.87; H, 7.96;
An EA3000 (Eurovector) analyzer, Jasco V-530 spectrophotometer,
and Spex Fluorg-3 Luminescence spectrophotometer were used to
obtain elemental analyses, UV/vis spectra, and photoluminescence
spectra, respectively. Emission decay lifetime curves were obtained
by a time-correlated single-photon counting (TCSPC) spectrometer
−
3
33 49
2
2
N, 4.51. Found: C, 63.55; H, 8.13; N 4.37.
Data for 3 (R = Br): pale yellow solid (0.27 g, 81%). H NMR
(CDCl ): δ 8.06 (s, 2H), 7.34 (d, J = 4.0 Hz, 2H), 7.01 (d, J = 4.0 Hz,
2H), 3.86 (m, 2H), 3.72 (m, 2H), 1.41 (s, 18H), −0.28 (s, 3H,
1
3
(FLS920, Edinburgh Instruments) equipped with a microchannel plate
13
photomultiplier tube (MCP-PMT, 200−850 nm) as a detector at room
temperature and an EPL-375 ps pulsed semiconductor diode laser
as an excitation source. The lifetimes were calculated by exponential
curve fittings. Cyclic voltammetry measurements using an AUTOLAB/
PGSTAT12 system were investigated in DMSO (0.5 mM) with a
three-electrode cell configuration (Pt working and counter electrodes
In−CH
134.18, 120.54, 105.79, 55.34, 35.61, 29.15, 5.13 (In−CH
Calcd for C25 InN : C, 45.07; H, 4.69; N, 4.21. Found:
C, 44.83; H, 4.50; N 4.14.
Data for 4 (R = Ph): pale yellow solid (0.28 g, 85%). H NMR
(CDCl ): δ 8.30 (s, 2H), 7.61 (d, J = 4.0 Hz, 2H), 7.51 (d, J = 8.0 Hz,
3
). C NMR (CDCl
3
): δ 169.82, 168.72, 145.67, 134.36,
). Anal.
3
H31Br
O
2 2
2
1
3
and a Ag/AgNO (0.1 M in MeCN) reference electrode) at room
4H), 7.38 (t, J = 12.0 Hz, 4H), 7.24 (t, J = 16.0 Hz, 2H), 7.16 (d, J =
4.0 Hz, 2H), 3.93 (m, 2H), 3.77 (m, 2H), 1.52 (s, 18H), −0.23 (s, 3H,
3
temperature. Tetrabutylammonium hexafluorophosphate (nBu PF ,
4
6
13
0
.1 M in DMSO) as a supporting electrolyte was used. The oxidative
In−CH ). C NMR (CDCl ): δ 170.92, 169.61, 143.43, 141.29,
3 3
−1
potentials were observed at a scan rate of 100 mV s and measured
with reference to the Fc/Fc redox couple.
130.92, 130.69, 128.65, 127.07, 126.24, 126.00, 119.33, 55.47, 35.57,
+
29.45. Anal. Calcd for C37
Found: C, 67.35; H, 5.97; N, 3.97.
Data for 5 (R = OCH
(CDCl
2H), 3.84 (m, 2H), 3.72 (m, 2H), 3.72 (s, 6H), 1.44 (s, 18H), −0.33
H41InN
O
2
: C, 67.28; H, 6.26; N, 4.24.
2
Synthesis. 3-tert-Butyl-5-R-2-hydroxybenzaldehyde (R = Br, Ph,
3
2−35
36
1
OMe, NMe2),
salen ligands L1−L6, and InMe were synthesized
3
): yellow solid (0.15 g, 65%). H NMR
3
from the reaction between InCl and 3.5 equiv of MeLi in THF at −78 °C
using literature procedures. After 1 h, all volatiles were removed
3
): δ 8.12 (s, 2H), 7.02 (d, J = 4.0 Hz, 2H), 6.34 (d, J = 4.0 Hz,
3
37
13
under vacuo. Recrystallization from hexane gave InMe as a colorless
(s, 3H, In−CH ). C NMR (CDCl ): δ 170.17, 165.36, 148.32,
3 3
3
crystalline solid (Figure S22 in the Supporting Information).
Caution! Since solid InMe3 is a highly pyrophoric material, its
144.70, 121.85, 117.72, 112.35, 55.78, 55.50, 35.54, 29.29. Anal. Calcd
for C H InN O : C, 57.05; H, 6.56; N, 4.93. Found: C, 56.64;
27
37
2
4
careful manipulation is required. Solid InMe should be stored and
H, 6.94; N, 4.49.
Data for 6 (R = N(CH ) ): orange solid (0.19 g, 63%). H NMR
3
1
must be handled under an inert atmosphere.
3
2
t
General Synthesis of (3- Bu-5-R-salen)In-Me (1−6). A 10 mL
(CDCl ): δ 8.20 (s, 2H), 7.10 (d, J = 4.0 Hz, 2H), 6.35 (d, J = 4.0 Hz,
3
toluene solution of InMe (90 mg, 0.55 mmol, 1.1 equiv) was added to
2H), 3.85 (m, 2H), 3.69 (m, 2H), 2.77 (s, 12H), 1.45 (s, 18H),
3
D
DOI: 10.1021/acs.inorgchem.6b02797
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Inorganic Chemistry
Article
1
3
−
0.34 (s, 3H, In−CH ). C NMR (CDCl ): δ 170.54, 164.72, 143.71,
ORCID
3
3
1
40.46, 123.39, 118.21, 116.46, 55.54, 43.10, 35.65, 29.39. Anal. Calcd
for C H InN O : C, 58.59; H, 7.29; N, 9.42. Found: C, 58.86;
H, 7.00; N, 9.17.
Synthesis of [(3- Bu-5-NMe -salen)In-Me](OTf) (7). An excess
Youngjo Kim: 0000-0001-8571-0623
Author Contributions
29
43
4
2
⊥
t
These authors contributed equally.
3
2
of MeOTf (0.058 g, 0.35 mmol, 3.5 equiv) was added to a 20 mL
dichloromethane solution of 6 (0.060 g, 0.10 mmol) at room
temperature. The reaction mixture was stirred for 0.5 h and the
insoluble parts were removed by the filtration. Additional washing
of insoluble filtrate with dichloromethane (2 × 10 mL) followed by
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the Basic Science Research
Program through the National Research Foundation of Korea
(NRF) funded by the Ministry of Education (NRF-
2015R1D1A1A01057396 for K.M.L.) and the Ministry of
Science, ICT & Future Planning (NRF-2016R1C1B1008452
for M.H.P.). Y.K. and M.K. thank the NRF through the
Creative Human Resource Training Project for Regional
Innovation (NRF-2014H1C1A1066874).
drying in vacuo afforded 7 as a colorless solid (0.088 g, 95%).
1
H NMR (CD CN): δ 8.44 (s, 2H), 7.50 (d, J = 4.0 Hz, 2H), 7.47 (d,
3
J = 4.0 Hz, 2H), 4.02 (m, 2H), 3.82 (m, 2H), 3.49 (s, 18H, N(CH ) ),
3
3
1
3
1
1
2
.46 (s, 18H), −0.21 (s, 3H, In−CH ). C NMR (CD CN): δ 171.98,
70.52, 145.95, 134.57, 125.14, 122.94, 119.46, 58.10, 55.94, 36.94,
9.52. Anal. Calcd for C H InN O S F : C, 42.96; H, 5.35; N, 6.07.
3
3
33
49
4
8 2 6
Found: C, 42.53; H, 5.71; N, 5.64.
X-ray Crystallography. The slow diffusion method of Et O into a
2
solution of 3−5 in THF was used to get single crystals of 3−5 suitable
for X-ray crystallographic analyses. The obtained crystals of 3−5 were
coated with Paratone oil to maintain the crystallinity of complexes and
mounted onto the end of a glass capillary. A Bruker D8QUEST CCD
area detector diffractometer with Mo Kα (λ = 0.71073 Å) radiation was
used for the crystallographic measurements. The structures were solved
by using direct methods, and all non-hydrogen atoms were subjected
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