Synthesis, characterization and fluorescent properties of 5-(aryliminomethyl)quinaldine-8-ol derivatives and their trinuclear zinc complexes

Article abstract of DOI:10.1016/j.saa.2014.03.013

A series of 5-[1-(arylimino)methyl]quinaldine-8-ol derivatives L1-L5 and their trinuclear zinc(II) complexes (C1-C5) were synthesized. The compounds L1-L5 were fully characterized by the FT-IR spectra, NMR measurement and elemental analysis, meanwhile the zinc complexes C1-C5 were characterized by the FT-IR spectra and elemental analysis as well as the single crystal X-ray diffraction of a representative complex C3, which revealed a trinuclear zinc complex bearing six organic ligands. The fluorescent properties of both organic compounds and the zinc complexes have been carefully investigated by the UV-Vis absorption in various solvents, indicating the significant influences of the solvents and also double exponential decays.

Full text of DOI:10.1016/j.saa.2014.03.013

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 128 (2014) 790–797
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, characterization and fluorescent properties
of 5-(aryliminomethyl)quinaldine-8-ol derivatives and
their trinuclear zinc complexes
Qing Yan a, Longlong Li a, Wen Li b, Lin Wang a, Wen-Hua Sun a,
⇑
a Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
b Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
Newly synthesized 5-
(aryliminomethyl)quinaldine-8-ol
derivatives.
ꢀ
ꢀ
ꢀ
Trinuclear complexes of zinc 5-
(aryliminomethyl)quinaldin-8-olates.
X-ray diffraction study on zinc
complex.
The luminescent properties enhanced
through coordination.
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of 5-[1-(arylimino)methyl]quinaldine-8-ol derivatives L1–L5 and their trinuclear zinc(II) com-
plexes (C1–C5) were synthesized. The compounds L1–L5 were fully characterized by the FT-IR spectra,
NMR measurement and elemental analysis, meanwhile the zinc complexes C1–C5 were characterized
by the FT-IR spectra and elemental analysis as well as the single crystal X-ray diffraction of a represen-
tative complex C3, which revealed a trinuclear zinc complex bearing six organic ligands. The fluorescent
properties of both organic compounds and the zinc complexes have been carefully investigated by the
UV–Vis absorption in various solvents, indicating the significant influences of the solvents and also dou-
ble exponential decays.
Received 7 February 2014
Received in revised form 7 March 2014
Accepted 8 March 2014
Available online 19 March 2014
Keywords:
5-[1-(Arylimino)methyl]quinaldine-8-ol
Trinuclear zinc complexes
Fluorescence
Ó 2014 Elsevier B.V. All rights reserved.
UV–Vis absorption spectra
Introduction
derivatives have been extensively investigated for their aluminum
complexes [8–15] and zinc complexes [16–20] as well as other
Among electroluminescent and photoluminescent materials,
the metal complexes have drawn more attentions due to easy
preparation and more potential applications [1–6]. Subsequence
to the thermo-stable and good electroluminescence of tris(8-
hydroxyquimoline)aluminum(III) (AlQ3) [7], the 8-hydroxyquinolinyl
metals such as gallium and indium [8,12,21–25]. In order to
control the emission wavelengths and absorption strengths of
compounds, there have been more efforts to adapt the various
substituents on the quinolinyl ring [26–31]. Recently the zinc
complexes bearing derivatives of phenol [32–34] and quinoline
[35,36] showed enhanced photoluminescence, subsequently herein
the 5-[1-(arylimino)methyl]quinaldine-8-ol derivatives have been
synthesized and used to form their zinc complexes. Interestingly
⇑
Corresponding author. Tel.: +86 10 62557955; fax: +86 10 62618239.
E-mail address: whsun@iccas.ac.cn (W.-H. Sun).
http://dx.doi.org/10.1016/j.saa.2014.03.013
1386-1425/Ó 2014 Elsevier B.V. All rights reserved.

Q. Yan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 128 (2014) 790–797
791
Scheme 1. Synthesis of ligands L1–L5 and their zinc complexes C1–C5.
Fig. 1. ORTEP drawing of the molecular structure of C3 (ellipsoids enclose 30% electronic density; H atoms were omitted for clarity).
the trinuclear complexes have been formed through coordinating
three zinc with six organic ligands, and its representative complex
is confirmed by the single crystal X-ray diffraction. Moreover, the
photoluminescent properties of organic compounds and their
zinc complexes have been extensively investigated in different
solvents. The synthesis, characterization and fluorescent properties
of the title compounds are reported in detail.
Results and discussion
Synthesis and characterization
The 5-formyl-8-hydroxyquinaldine was freshly prepared by the
Reimer–Tiemann reaction of 8-hydroxyquinaldine [37], and fur-
ther processed the condensation reaction with various anilines to

792
Q. Yan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 128 (2014) 790–797
Table 1
Selected bond lengths and angles for C3.
Bond lengths (Å)
Zn(1)–O(1)
Zn(1)–O(2)
Zn(1)–O(3)
Zn(1)–N(1)
Zn(1)–N(3)
Zn(2)–O(2)
Zn(2)–O(3)
Zn(2)–O(4)
1.983(4)
2.072(4)
2.021(4)
2.143(4)
2.172(5)
2.026(4)
2.143(4)
2.143(4)
Zn(2)–O(5)
Zn(2)–N(9)
Zn(2)–N(11)
Zn(3)–O(4)
Zn(3)–O(5)
Zn(3)–O(6)
Zn(3)–N(5)
Zn(3)–N(7)
2.040(4)
2.140(4)
2.135(5)
2.019(4)
2.066(3)
1.956(4)
2.168(4)
2.136(4)
Bond angles (°)
O(1)–Zn(1)–O(3)
O(1)–Zn(1)–O(2)
O(1)–Zn(1)–N(1)
O(1)–Zn(1)–N(3)
O(2)–Zn(1)–N(1)
O(2)–Zn(1)–N(3)
O(3)–Zn(1)–O(2)
O(3)–Zn(1)–N(1)
O(3)–Zn(1)–N(3)
O(1)–Zn(1)–O(3)
N(1)–Zn(1)–N(3)
O(2)–Zn(2)–O(3)
O(2)–Zn(2)–O(4)
O(2)–Zn(2)–O(5)
O(2)–Zn(2)–N(9)
O(2)–Zn(2)–N(11)
O(4)–Zn(2)–O(3)
O(5)–Zn(2)–O(3)
173.28(15)
96.11(16)
82.06(15)
105.64(17)
118.06(16)
131.66(16)
77.43(16)
102.54(15)
77.84(16)
173.28(15)
107.49(17)
75.70(15)
95.28(15)
167.43(15)
108.91(17)
79.64(17)
88.03(15)
95.23(16)
O(5)–Zn(2)–O(4)
O(5)–Zn(2)–N(9)
O(5)–Zn(2)–N(11)
N(9)–Zn(2)–O(3)
N(9)–Zn(2)–O(4)
N(11)–Zn(2)–O(3)
N(11)–Zn(2)–O(4)
N(11)–Zn(2)–N(9)
O(6)–Zn(3)–O(4)
O(6)–Zn(3)–O(5)
O(6)–Zn(3)–N(7)
O(6)–Zn(3)–N(5)
O(5)–Zn(3)–N(7)
O(5)–Zn(3)–N(5)
O(4)–Zn(3)–O(5)
O(4)–Zn(3)–N(7)
O(4)–Zn(3)–N(5)
N(7)–Zn(3)–N(5)
75.46(14)
79.75(16)
108.83(18)
92.32(16)
155.13(16)
155.28(17)
92.54(17)
97.31(19)
174.64(14)
97.22(15)
81.99(16)
103.89(19)
114.30(16)
131.25(16)
77.62(15)
101.35(16)
78.87(18)
111.85(16)
Fig. 2. UV–Vis absorption spectra of ligands (L1, L2, L5) and zinc complexes (C1, C2,
C5) in methanol.
with n-heptane at room temperature. The complex C3 is a trinu-
clear zinc(II) complex, in which three zinc atoms are bridged by
six oxo-atoms of 8-oxy-5-iminoquinaldinyl ligands; two zinc
atoms (Zn1 and Zn3) are five-coordinated with three oxo-atoms
and two nitrogen atoms meanwhile the middle zinc (Zn2) atom
is six-coordinated with four oxo-atoms and two nitrogen atoms.
Its molecular structure is illustrated in Fig. 1, and the selected bond
lengths and angles are tabulated in Table 1. It is worthy to mention
that there are no direct zinc–zinc bonds with the Zn1–Zn2 length
3.240 Å and the Zn2–Zn3 length 3.243 Å as well as the angle of
Zn1–Zn2–Zn3 113°.
form the 5-(aryliminomethyl)quinaldine-8-ol derivatives (L1–L5)
(Scheme 1) in acceptable yields. All the organic compounds were
well characterized by the FT-IR spectra and NMR measurements,
and their elemental analyses were well consistent to their molec-
ular formula.
These 5-(aryliminomethyl)quinaldine-8-ol derivatives individ-
ually reacted with half-equivalent mole of zinc acetate in tetrahy-
drofuran (THF) at room temperature; in the light of adding
petroleum ether to concentrated THF solution, the precipitated yel-
low solids as their zinc complexes were collected in good yields.
These zinc complexes were characterized by the FT-IR spectra
and the elemental analysis. To confirm their absolute structure,
the single crystals of complexes C3 were isolated and characterized
by the single-crystal X-ray diffraction method.
Six ligands in the complex C3 are not interacted to each other,
and the quinaldinylimino-aryl groups have been stretched far out
from zinc cores. There is no observation of the imino-coordination
within such complex.
UV–Vis absorption
To understand the fluorescent properties of the 5-(aryliminom-
ethyl)quinaldine-8-ol derivatives and their zinc complexes, their
UV–Vis absorption spectra have been measured in the solvent such
as methanol, THF or toluene with fixing the solution concentration
as 1 ꢁ 10ꢂ5 M. Their data are tabulated in Table 2.
In the typical polar solvent of methanol, the highly similar
curves with four absorption peaks were observed; for example,
the organic compounds (L1, L2, L5) showed absorptions at around
205, 220, 246 and 339 nm in comparison to their Zn complexes
(C1, C2, C5) observed at around 228, 260, 296 and 392 nm, being
illustrated in Fig. 2. In the light of effective coordination between
Molecular structure
Single crystals of complex C3 suitable for X-ray diffraction anal-
yses were obtained from its dichloromethane solution on layering
Table 2
The UV–Vis absorption of ligands and their zinc complexes.
Solvent
Ligands
kabs-max (nm)
e(kmax) (Mꢂ1 cmꢂ1
)
Complex
kabs-max (nm)
e(kmax) (Mꢂ1 cmꢂ1
)
Methanol
THF
Toluene
L1
247
248
284
54,580
24,590
22,920
C1
230
268
286
2,67,960
1,79,470
87,380
Methanol
THF
Toluene
L2
L3
L4
L5
247
248
284
34,890
31,430
19,830
C2
C3
C4
C5
263
269
300
2,01,430
2,34,740
1,59,440
Methanol
THF
Toluene
217
277
284
1,83,100
13,090
22,320
262
269
300
2,24,980
2,05,850
1,43,430
Methanol
THF
Toluene
247
248
284
34,550
23,310
29,840
222
269
286
1,42,660
2,32,920
72,330
Methanol
THF
Toluene
222
250
284
26,430
23,410
17,360
262
270
300
2,10,190
2,43,380
1,45,790

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793
Fig. 3. (a) Absorption spectra of L1–L5 in THF; (b) absorption spectra of C1–C5 in THF; (c) absorption spectra of L1–L5 in toluene; (d) absorption spectra of C1–C5 in toluene.
Table 3
Emission data for compounds L1ꢂL5 and C1ꢂC5.
Solvent
Ligands
Complexes
kmaxEm (nm)
kEx (nm)
D
ka (nm)
kmaxEm (nm)
kEx (nm)
D
ka (nm)
Methanol
THF
Toluene
L1
L2
L3
L4
L5
337
327
329
225
277
291
112
50
38
C1
C2
C3
C4
C5
330
335
332
284
284
293
46
51
39
Methanol
THF
Toluene
340
327
330
226
279
291
114
48
39
342
334
334
233
284
291
109
50
43
Methanol
THF
Toluene
333
325
328
224
279
290
109
46
38
347
331
335
236
284
291
111
47
44
Methanol
THF
Toluene
335
327
328
224
277
290
111
50
38
343
332
332
235
284
293
108
48
39
Methanol
THF
Toluene
339
284
328
226
262
293
113
22
35
343
333
335
236
285
290
107
48
45
a
D
k = Stokes shift.
zinc atoms and organic compounds, their complexes significantly
displayed stronger absorptions with red shifts to their organic
analogs.
along with red-shifts in comparison to the peaks of their corre-
sponding ligands.
On the base of above data, the absorptions of both organic and
its complex were significantly affected by the solvent. In general,
the maximum absorptive wavelengths (kabs-max) of all the ligands
and their corresponding complexes exhibited blue-shifts along
with either incorporation of oxo-solvents or higher polarity of
Subsequently, their UV-absorption were also investigated in
non-polar solvent such as THF or toluene in Fig. 3. All the organic
compounds (L1–L5) exhibited maximum absorption peaks at
around 248 nm in THF (Fig. 3a) and 284 nm in toluene (Fig. 3c);
meanwhile all the zinc complexes (C1–C5) showed at around
268 nm in THF (Fig. 3b) and 300 nm in toluene (Fig. 3d). There
were clearly red-shifted absorptions observed in their THF solu-
tions than those of toluene solutions, about 36 nm for the organic
compounds (L1–L5) and 32 nm for the zinc complexes (C1–C5).
Similar to the observations in their methanol solutions, the absorp-
tion strengths of all the zinc complexes (C1–C5) were enhanced
the solvents, which were consistent to the energy gap (DE) en-
larged with increasing the polarity of the solvent used [34,38,39].
Fluorescent properties
Fixed the solution concentration at 1 ꢁ 10ꢂ5 M, the emission
data of all the organic compounds and their zinc complexes were
measured in the solvents of methanol, THF and toluene,

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Q. Yan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 128 (2014) 790–797
Fig. 4. Fluorescence spectra of ligands L1–L5 and zinc complexes C1–C5 in different solvents: (a and b) methanol; (c and d) THF; (e and f) toluene.
Table 4
Excited singlet state lifetimes (
s) and the values of radiative decay rate (kr) of ligands (L1ꢂL5) and zinc complexes (C1ꢂC5).
Ligands
Complexes
Solvent
Us
s1 (ns)
kr1 (106 sꢂ1
a
)
s2 (ns)
kr2 (106 sꢂ1
a
)
Us
s1 (ns)
kr1 (106 sꢂ1
a
)
s2 (ns)
kr2 (106 sꢂ1
a
)
Methanol
Methanol
Methanol
Methanol
Methanol
THF
L1
L2
L3
L4
L5
L2
L2
0.1052
0.1435
0.0338
0.1319
0.2027
0.3543
0.4940
7.882
8.490
11.16
9.155
12.00
15.52
10.13
13.34
16.91
3.031
14.40
16.89
22.83
48.77
1.695
1.917
2.131
1.197
1.886
4.432
3.230
62.04
74.87
15.87
110.2
107.5
79.95
152.9
C1
C2
C3
C4
C5
C2
C2
0.1124
0.6795
0.0427
0.1878
0.0579
0.0435
0.0214
9.813
9.452
10.62
10.49
10.01
7.673
8.209
11.45
71.89
4.022
17.09
5.780
5.667
2.609
1.675
1.873
2.132
1.213
1.523
3.806
2.326
67.09
362.8
20.04
154.8
37.99
11.42
9.207
Toluene
Concentration: 1 ꢁ 10ꢂ5 M.
a
kr = UF/s.
individually, and their data are collected in Table 3. All the organic
compounds and their zinc complexes exhibited large Stokes shift in
methanol, however, small Stokes shifts appeared in the non-polar
potential of the hydrogen bond between methanol and compounds
caused the large Stokes shift [33,36]. By verifying solvents, the sim-
ilar Stokes shifts were observed with the solution of both organic
compounds L1–L5 and their corresponding zinc complexes C1–C5.
Their fluorescence spectra are showed in Fig. 4. In methanol,
compounds L1–L5 showed similar curves, and the maximum emis-
sion wavelengths (kmaxEm) were close between organic compound
solvents of THF and toluene. For example, the Stokes shifts (Dk)
for compound L3 is 109 nm in methanol, 46 nm in THF and
38 nm in toluene; whilst the Stokes shifts for complex C3 are
111 nm in methanol, 47 nm in THF and 44 nm in toluene. The

Q. Yan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 128 (2014) 790–797
795
Table 5
as the trinuclear complex by the single-crystal X-ray diffraction.
The UV-absorption spectra and Fluorescence properties of all the
compounds were investigated in the solvents such as methanol,
THF and toluene. The maximum UV-absorptions of both organic
compounds and their zinc complexes exhibited red-shifts in tolu-
ene. In methanol, the fluorescent quantum yields of their corre-
sponding zinc complexes were enhanced. With comparative
study of compounds L2 and C2, the maximum fluorescent quan-
tum yields of complex C2 were quenched in toluene and THF. All
the organic compounds and zinc complexes exhibited double
exponential decays in various solvents, attributing to the two
Summary of crystallographic data for C3.
C3
Empirical formula
Formula weight
Crystal color
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C138H150N12O6Zn3
2268.81
Black
100(2)
0.71073
Monoclinic
P 21/C
16.873(3)
46.679(9)
18.366(4)
90
b (Å)
C (Å)
p-conjugated rings in their molecular structures.
a
(°)
b (°)
104.87(3)
90
13981(5)
4
1.078
0.580
c
(°)
Experimental
Volume (Å3)
Z
D calcd (mg mꢂ3
)
General consideration
l
(mmꢂ1
)
F (000)
Crystal size (mm)
h range (°)
Limiting indices
4800
All manipulations of air and/or moisture-sensitive compounds
were carried out under an atmosphere of nitrogen using standard
Schlenk techniques. THF was refluxed over sodium–benzophenone
and distilled under nitrogen prior to use. IR spectra were recorded
on a Perkin Elmer FT-IR 2000 spectrometer in the range of 4000–
400 cmꢂ1. Elemental analysis was performed on a Flash EA 1112
microanalyzer. 1H NMR and 13C NMR spectra were recorded on a
Bruker DMX 400 MHz instrument at ambient temperature using
TMS as an internal standard. The steadystate fluorescent spectra
were measured on an F4500-FL fluorescence spectrophotometer;
fluorescence lifetimes were obtained using the time-correlated sin-
gle-photon counting technique (Edinburgh Analytical Instruments
F900 fluorescence spectrofluorimeter). Thin films of the samples
were prepared on quartz slides (1 cm) through spin-coating. The
fluorescence quantum yield for samples in solution was measured
by using the solution containing coumarin 307 in methanol
0.51 ꢁ 0.21 ꢁ 0.20
1.44–25.00
ꢂ19 6 h 6 19
ꢂ54 6 k 6 55
ꢂ21 6 l 6 21
70,964
24,472
0.0528
99.4 (h = 25.00)
1.056
R1 = 0.0983
wR2 = 0.2781
R1 = 0.1203
wR2 = 0.2997
1.259 and ꢂ0.681
No. of rflns collected
No. of unique rflns
Rint
Completeness to h (%)
Goodness-of-fit on F2
Final R indices [I > 2
R indices (all data)
r(I)]
Largest diff. peak and hole (e Åꢂ3
)
and their zinc complex. For example, the kmaxEm for compounds
L1–L5 were 337, 340, 333, 335, 339 nm, respectively; whilst the
kmaxEm for complexes C1–C5 were 330, 342, 347, 343, 343 nm,
respectively. The tendency of observed data was similar in other
solvents, however, different fluorescence intensities were ob-
served, indicating the substituent effect on the fluorescence spec-
tra. As a fact, the verified substituents are not centred in the
molecules, and their causes are not understood and waiting for fur-
ther investigation.
(Ur = 0.56) standard as the reference, U was calculated according
to the following equation: [36,40].
R
R
ꢀ
ꢁꢀ
ꢁꢀ
ꢁ
ArðkrÞ IðkrÞ n2s
AsðksÞ IðksÞ n2r
Fs
Fr
Us
¼
Ur
where r represents the standard, s represents the samples, Ar (kr)
and As (ks) are the respective absorbance of the standard and the
measured samples, I (kr) and I (ks) are the respective emission inten-
The fluorescence quantum yields, excited singlet state lifetimes
(s) and the values of radiative decay rate (kr) are tabulated in Table 4.
sities of the standards and samples, n is the refractive index of the
corresponding solvents, F is the integral area of one-photon fluo-
rescence, and U represents the fluorescence quantum yield.
R
In methanol, the quantum yield of all the ligands were observed to
be in the order L5 > L2 > L4 > L1 > L3. Howerver, for the complexes,
the quantum yield of complex C2 is significantly higher than those
of other complexes with the order C2 > C4 > C1 > C5 > C3. In general,
the fluorescent quantum yields of their corresponding zinc com-
plexes were enhanced to some extent, this is described to the newly
formed rings through the coordination of zinc and the ligands and
leading to bigger and more rigid structures. Therefore the interac-
tion between the excited molecules and solvent molecules were re-
duced to result the reducing of energy transfer, which could be
beneficial to the fluorescence emission. In using THF or toluene as
the solvent, the fluorescence of complex C2 was significantly
quenched in the comparison to organic L2. In addition, the fluores-
cence decay of all organic compounds and zinc complexes followed
a double exponential decay in various solvents, probably due to two
Synthesis of 5-[1-(arylimino)methyl]quinaldine-8-ol derivatives (L1–
L5)
2-Methyl-5-(1-(2,6-dimethylphenylimino)methyl)quinolin-8-ol (L1).
A
solution of 8-hydroxyquinaldine-5-carbaldehyde (1.87 g,
10 mmol) and 2,6-dimethylbenzenamine (1.45 g, 12 mmol) and a
catalytic amount of p-toluenesulfonic acid in toluene (150 mL)
was refluxed for 12 h, then the solvents was evaporated at reduced
pressure. The product, 2-methyl-5-(1-(2,6-dimethylphenylimi-
no)methyl)quinolin-8-ol (L1), was purified by column chromatog-
raphy (silica gel, Vpetroleum ether:Vethyl acetate = 30:1), and was a
yellow powder, which was collected in 26.6% (0.77 g). 1H NMR
(400 MHz, CDCl3, ppm):d 9.90 (d, J = 8.0 Hz, 1H), 8.48 (s, 1H),
7.74 (d, J = 8.0 Hz, 1H), 7.49 (d, J = 8.8 Hz, 1H), 7.24 (d, J = 7.6 Hz,
1H), 7.11 (d, J = 7.6 Hz, 2H), 6.98 (d, J = 7.6 Hz, 1H), 2.80 (s, 3H),
2.20 (s, 6H). 13C NMR (100 MHz, CDCl3, ppm): d 163.3, 157.4,
154.7, 151.9, 137.9, 135.4, 134.0, 128.2, 127.3, 125.2, 124.4,
123.7, 122.6, 109.1, 24.9, 18.6. FT-IR (cmꢂ1): 3295 (m), 2981 (w),
2914 (w), 1637 (m), 1608 (m), 1590 (m), 1564 (s), 1503 (s), 1472
(m), 1431 (w), 1410 (w), 1369 (m), 1330 (m), 1269 (m), 1253
p
-conjugated rings existed.
Conclusion
A series of 5-[1-(arylimino)methyl]quinaldine-8-ol derivatives
L1–L5 and their Zn(II) complexes (C1–C5) were synthesized and
full characterized. The molecular structure of C3 was confirmed

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Q. Yan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 128 (2014) 790–797
(w), 1234 (w), 1194 (m), 1150 (m), 1087 (m), 982 (m), 836 (s), 799
(s), 760 (s), 713 (s). Anal. Calcd. For C19H18N2O (290.36): C, 78.59;
H, 6.25; N, 9.65. Found: C, 78.28; H, 6.33; N, 9.59%.
C22H24N2O (332.44): C, 79.48; H, 7.28; N, 8.43. Found: C, 79.16;
H, 7.39; N, 8.39%.
2-Methyl-5-(1-(2,6-diethylphenylimino)methyl)quinolin-8-ol (L2).
Using the same procedure as for the synthesis of L1, but 2,6-dieth-
ylbenzenamine was used instead of 2,6-dimethylbenzenamine.
The 2-methyl-5-(1-(2,6-diethylphenylimino)methyl)quinolin-8-ol
was obtained as a yellow solid in 44.9% (1.43 g) yield. 1H NMR
(400 MHz, CDCl3, ppm): d 9.93 (bs, 1H), 8.49 (s, 1H), 7.74 (d,
J = 7.6 Hz, 1H), 7.50 (d, J = 8.8 Hz, 1H), 7.25 (d, J = 7.2 Hz, 1H),
7.13 (d, J = 7.6 Hz, 2H), 7.06 (d, J = 7.6 Hz, 1H), 2.82 (s, 3H), 2.56
(m, 4H), 1.16 (t, J = 7.6 Hz, 6H). 13C NMR (100 MHz, CDCl3, ppm):
d 162.9, 157.4, 154.7, 151.1, 137.9, 135.3, 134.1, 133.3, 126.5,
125.2, 124.5, 123.9, 122.5, 109.1, 25.0, 24.9, 14.9. FT-IR (cmꢂ1):
3305 (m), 2964 (w), 2868 (w), 1639(m), 1608 (s), 1563 (s), 1503
(s), 1447 (m), 1369 (w), 1331 (w), 1261 (w), 1224 (s), 1186 (w),
1155 (s), 1097 (w), 1046 (w), 904 (w), 837 (s), 792 (m), 749 (s),
710 (m). Anal. Calcd. For C21H22N2O (318.17): C, 79.21; H, 6.96;
N, 8.80. Found: C, 78.89; H, 6.90; N, 8.76%.
The synthesis of the zinc complexes (C1–C5)
The synthesis of complex C1 To a THF solution (6 ml) of 0.29 g
(1.00 mmol)
2-methyl-5-(1-(2,6-dimethylphenylimino)methyl)
quinolin-8-ol (L1), then an ethanol solution (4 ml) of 0.11 g
(0.50 mmol) zinc acetate dehydrate was added. The reaction mix-
ture was stirred at room temperature for 18 h. Then the solvent
was removed under vacuum, and petroleum ether was added to
precipitate the complex. The resulting precipitate was filtered,
washed with petroleum ether, and dried under vacuum to furnish
the product C1 as a yellow powder in 67.6% (0.22 g) yield. FT-IR
(cmꢂ1): 3079 (w), 1629 (s), 1604 (s), 1578 (s), 1514 (s), 1467 (w),
1433 (w), 1376 (m), 1345 (s), 1315 (s), 1249 (w), 1226 (m), 1202
(m), 1174 (s), 1104 (m), 1066 (m), 981 (w), 857 (w), 838 (s), 799
(m), 754 (s), 734(m). Anal. Calcd. For
(1932.28): C, 70.86; H, 5.32; N, 8.70. Found: C, 70.68; H, 5.35; N,
8.56%.
C114H102N12O6Zn3
2-Methyl-5-(1-(2,6-diisopropylphenylimino)methyl)quinolin-8-ol
(L3). Using the same procedure as for the synthesis of L1, but 2,6-
diisopropylbenzenamine was used instead of 2,6-dimethylbenzen-
amine. The 2-methyl-5-(1-(2,6-diisopropylphenylimino)methyl)
quinolin-8-ol was obtained as a yellow solid in 56.2% (1.94 g) yield.
1H NMR (400 MHz, CDCl3, ppm): d9.80 (d, J = 8.8 Hz, 1H), 8.48
(s, 1H), 7.74 (d, J = 8.0 Hz, 1H), 7.49 (d, J = 8.8 Hz, 1H), 7.22 (d,
J = 8.0 Hz, 1H), 7.20 (d, J = 7.6 Hz, 2H), 7.13 (t, J = 7.6 Hz, 1H),
3.10–3.03 (m, 2H), 2.77 (s, 3H), 1.19 (d, J = 6.8 Hz, 12H). 13C NMR
(100 MHz, CDCl3, ppm): d 162.7, 157.4, 154.7, 150.0, 137.8, 135.3,
134.0, 125.2, 124.5, 124.1, 123.2, 122.5, 109.2, 28.2, 24.9,
23.6. FT-IR (cmꢂ1): 3310 (m), 2961 (m), 1637 (m), 1612 (s),
1563 (s), 1506 (s), 1468 (w), 1363 (w), 1327 (m), 1262 (s), 1223
(m), 1183 (w), 1156 (m), 1101 (w), 1077 (w), 1049 (m), 903 (w),
842 (s), 789 (m), 745 (s), 711 (s). Anal. Calcd. For C23H26N2O
(346.47): C, 79.73; H, 7.56; N, 8.09. Found: C, 79.73; H, 7.75;
N, 8.05%.
2-Methyl-5-(1-(2,4,6-trimethylphenylimino)methyl)quinolin-8-ol
(L4). Using the same procedure as for the synthesis of L1, but 2,4,6-
trimethylbenzenamine was used instead of 2,6-dimethylbenzen-
amine. The 2-methyl-5-(1-(2,4,6-trimethylphenylimino) methyl)
quinolin-8-ol was obtained as a yellow solid in 30.3% (0.92 g) yield.
1H NMR (400 MHz, CDCl3, ppm): d 9.83 (d, J = 8.4 Hz, 1H), 8.48 (s,
1H), 7.71 (d, J = 8.0 Hz, 1H), 7.46 (d, J = 8.8 Hz, 1H), 7.20 (d,
J = 7.6 Hz, 1H), 6.93 (s, 2H), 2.76 (s, 3H), 2.31 (s, 3H), 2.18 (s, 6H).
13C NMR (100 MHz, CDCl3, ppm): d 163.3, 157.3, 154.6, 149.5,
137.9, 135.4, 133.7, 132.9, 128.9, 127.2, 125.1, 124.3, 122.7,
109.0, 24.9, 20.8, 18.5. FT-IR (cmꢂ1): 3305 (m), 2913 (w), 2846
(w), 1639 (m), 1605 (s), 1563 (s), 1506 (m), 1474 (m), 1372 (w),
1331 (w), 1266 (m), 1199 (m), 1170 (w), 1142 (s), 1031 (m), 834
(s), 797 (w), 710 (m). Anal. Calcd. For C20H20N2O (304.39): C,
78.92; H, 6.62; N, 9.20. Found: C, 78.77; H, 6.62; N, 9.07%.
2-Methyl-5-(1-(2,6-diethyl-4-methylphenylimino)methyl)quino-
lin-8-ol (L5). Using the same procedure as for the synthesis of L1,
but 2,6-diethyl-4-methylbenzenamine was used instead of 2,6-
dimethylbenzenamine. The 2-methyl-5-(1-(2,6-diethyl-4-methyl
phenylimino)methyl)quinolin-8-ol was obtained as a yellow solid
in 44.1% (1.46 g) yield. 1H NMR (400 MHz, CDCl3, ppm): d 9.89
(bs, 1H), 8.47 (s, 1H), 7.73 (d, J = 7.6 Hz, 1H), 7.48 (d, J = 8.8 Hz,
1H), 7.23 (d, J = 8.0 Hz, 1H), 6.94 (s, 2H), 2.80 (s, 3H), 2.55–2.48
(m, 4H), 2.34 (s, 3H), 1.15 (t, J = 7.4 Hz, 6H). 13C NMR (100 MHz,
CDCl3, ppm): d 163.0, 157.4, 154.6, 148.7, 137.9, 135.4, 133.9,
133.3, 133.2, 127.2, 125.2, 124.5, 122.7, 109.1, 25.0, 24.9, 21.1,
15.0. FT-IR (cmꢂ1): 3311 (m), 2966 (m), 2927 (w), 2870 (w),
1638 (m), 1614 (s), 1566 (s), 1503 (s), 1460 (w), 1371 (w), 1331
(w), 1268 (s), 1236 (w), 1199 (s), 1169 (m), 1139 (s), 1078 (w),
1049 (w), 882 (m), 839 (s), 800 (s), 714 (s). Anal. Calcd. For
The synthesis of C2 Using the same procedure as for the synthe-
sis of C1, C2 was prepared by using L2 instead of L1 and a yellow
powder was obtained in 68.2% (0.24 g) yield. FT-IR (cmꢂ1): 2971
(m), 2932 (w), 1629 (s), 1603 (s), 1557 (s), 1513 (s) 1455 (s),
1378 (w), 1345 (m), 1312 (s), 1220 (m), 1169 (s), 1105 (m), 1063
(m), 861 (w), 835 (s), 797 (s), 747.1 (s). Anal. Calcd. For C126H126-
N12O6Zn3 (2100.6): C, 72.04; H, 6.05; N, 8.00. Found: C, 72.25; H,
6.14; N, 7.83%.
The synthesis of C3 Using the same procedure as for the synthe-
sis of C1, C4 was prepared by using L3 instead of L1 and a yellow
powder was obtained in 84.5% (0.093 g) yield. FT-IR (cmꢂ1): 2958
(m), 2865 (w), 1628 (m), 1604 (m), 1552 (s), 1513 (s), 1454 (s),
1378 (w), 1336 (w), 1305 (s), 1219 (m), 1166 (s), 1099 (s), 1058
(m), 914 (w), 836 (m), 792 (m), 733 (m). Anal. Calcd. For C138H150-
N12O6Zn3 (2268.91): C, 73.06; H, 6.66; N, 7.41. Found: C, 73.01; H,
6.62; N, 7.33%.
The synthesis of C4 Using the same procedure as for the synthe-
sis of C1, C4 was prepared by using L4 instead of L1 and a yellow
powder was obtained in 90.6% (0.15 g) yield. FT-IR (cmꢂ1): 2916
(w), 2857 (w), 1631 (s), 1601 (s), 1556 (s), 1513 (s), 1433 (s),
1374 (w), 1344 (m), 1312 (m), 1203 (w), 1180 (w), 1139 (w),
1100 (w), 1065 (w), 1033 (w), 836 (m), 797 (w). Anal. Calcd. For
C120H114N12O6Zn3 (2016.44): C, 71.48; H, 5.70; N, 8.34. Found: C,
71.32; H, 5.68; N, 8.29%.
The synthesis of C5 Using the same procedure as for the synthe-
sis of C1, C5 was prepared by using L5 instead of L1 and a yellow
powder was obtained in 76.7% (0.084 g) yield. FT-IR (cmꢂ1): 2973
(w), 1628 (m), 1601 (m), 1560 (s), 1513 (s), 1460 (m), 1376 (m),
1348 (m), 1316 (s), 1273 (w), 1227 (w), 1206 (m), 1185 (m),
1160 (w), 1141 (m), 1105 (m), 1063 (m), 990 (w), 862 (m), 837
(s), 797 (m), 740 (m). Anal. Calcd. For
C132H138N12O6Zn3
(2184.75): C, 72.57; H, 6.37; N, 7.69. Found: C, 72.68; H, 6.42; N,
7.68%.
X-ray diffraction study
Single crystals of complex C3 suitable for single-crystal X-ray
analysis were obtained by laying n-heptane on the dichlorometh-
ane solutions. Single-crystal X-ray diffraction for complex C3 were
performed on a Rigaku RAXIS Rapid IP diffractometer with graph-
ite-monochromated Mo K
a radiation (k = 0.71073 Å) at 173(2) K.
Cell parameters were obtained by global refinement of the posi-
tions of all collected reflections. Intensities were corrected for Lor-
entz and polarization effects and empirical absorption. The
structures were solved by direct methods and refined by full-ma-
trix least-squares on F2. All non-hydrogen atoms were refined
anisotropically. Structure solution and refinement were performed

Q. Yan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 128 (2014) 790–797
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for Zn3(L3)6 (C3). This data can be obtained free of charge via
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