Syntheses, luminescences and Hirshfeld surfaces analyses of structurally characterized homo-trinuclear ZnII and hetero-pentanuclear ZnII-LnIII (Ln?=?Eu, Nd) bis(salamo)-like complexes

Article abstract of DOI:10.1016/j.ica.2019.02.040

Homo-trinuclear [Zn₃(L)(μ₂-OAc)₂(H₂O)].CH₂Cl₂ (1) and hetero-pentanuclear [Zn₄(L)₂Eu(NO₃)₃(H₂O)] (2) and [Zn₄(L)₂

Full text of DOI:10.1016/j.ica.2019.02.040

Inorganica Chimica Acta 490 (2019) 6–15
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Syntheses, luminescences and Hirshfeld surfaces analyses of structurally
II
II
III
characterized homo-trinuclear Zn and hetero-pentanuclear Zn -Ln
(
Ln = Eu, Nd) bis(salamo)-like complexes
⁎
Qing Zhao, Xiao-Xin An, Ling-Zhi Liu, Wen-Kui Dong
School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou, Gansu 730070, PR China
A R T I C L E I N F O
A B S T R A C T
.
Keywords:
Homo-trinuclear [Zn
3
2
(L)(μ
2
-OAc)
2
2
(H
2
O)] CH
2
Cl
2
(1) and hetero-pentanuclear [Zn
4
(L)
2
Eu(NO
3
)
3
(H O)] (2) and
2
Bis(salamo) ligand
[Zn (L) Nd(NO ) (H O)]·CH CH OH (3) complexes containing a coumarin-skeleton bis(salamo) ligand H L,
4
2
3
3
3
4
II
III
Zn -Ln complex
Crystal structure
were successfully prepared and characterized via the means of elemental analyses, single crystal X-ray crys-
tallography, FT-IR, UV–Vis absorption spectroscopy and Hirshfeld surfaces analyses. Complex 1 is a 1:3
Hirshfeld surface analysis
Luminescence
4−
II
4−
II
III
II
(
(L) :Zn ) structure, and complexes 2 and 3 are 2:4:1 ((L) :Zn :Ln ) structure. All Zn atoms in complexes
1
–3 occupied the N
2
O sites are five-coordinated with geometries of slightly distorted tetragonal pyramid and
2
III III
trigonal bipyramid. Rare earth metal (Eu and Nd ) atoms are both coordinated with phenolic oxygen atoms,
and eight-coordinated with the square antiprism geometries in complexes 2 and 3. Water molecules as co-
…
ordinating solvents participate in the coordination. Supra-molecular structures are built by CeH π and hy-
drogen bonding interactions in complexes 1–3. Moreover, Hirshfeld surfaces analyses of complexes 1–3 were
also analysed in detail. Most important of all, luminescences of complexes 1–3 were discussed.
II
III
1
. Introduction
been devoted to the preparations of Zn -Ln complexes because of
their potential applications in magnetic [42–44] and supra-molecular
architectures [45–49]. Coumarin, as an important intermediate product
and raw materials of organic chemicals, has been widely used in
medicine, agriculture, photosensitive materials and other fields. It is
noteworthy that coumarin and its derivatives have good characteristics
of luminescences [33,50,51] and can be used as a good luminescent
material.
Recently, the extensive research on the metal complexes has been
received increase attention in the fields of coordination chemistry and
organometallic chemistry. Salen-like ligands having O, N-donor sites
are apt to coordinate to transition metal ions [1,2]. Consequently,
salen-like complexes also have been actively studied because of not
only their interesting crystal structures but also their widespread ap-
plications, such as catalysts for organic reactions [3–5], electrochemical
conducts [6,7], magnetic materials [8–13], luminescences [14–17],
ions recognitions [18–22], supra-molecular buildings [23,24], non-
linear optical materials [25] and biological systems [26–28].
Based on previous researches, in this paper, we designed a new
containing coumarin-skeleton bis(salamo)-like ligand H
4
L, and ob-
III
II
II
tained three homo-trinuclear Zn (1) and hetero-pentanuclear Zn -Ln
(Ln = Eu (2) and Nd(3)) complexes by the metalation of H
4
L. To our
4
−
n+
Noticeably, salamo-like ligands [29-33], as a salen-like derivative,
have been developed by Nabeshima’s group [34,35], mainly using to
synthesize transition and rare metal complexes. Compared with tran-
sition metal ions, lanthanide ions possess the characteristics of high
coordination numbers and electronic structure. Accordingly, the
structures of lanthanide complexes are interesting [36–38]. A great
quantity of studies on the lanthanide complexes arise from their ex-
tensive applications such as biomedical and optical technologies.
Salamo-like zinc(II) complexes have been widely researched due to
their interesting photophysical properties [39–41]. Many efforts have
best knowledge, these hetero-pentanuclear 2:5 ((L) :M
) bis
(salamo)-like complexes has rarely reported [6]. Most important of all,
the Hirshfeld surfaces analyses and spectroscopic properties of com-
plexes 1–3 were investigated in detail.
2. Experimental
2.1. Materials and methods
1,2-Dimethoxybenzene, n-butyllithium, TMEDA, boron tribromide
⁎
Corresponding author.
E-mail address: dongwk@126.com (W.-K. Dong).
https://doi.org/10.1016/j.ica.2019.02.040
Received 3 February 2019; Received in revised form 24 February 2019; Accepted 26 February 2019
Available online 27 February 2019
0020-1693/ © 2019 Elsevier B.V. All rights reserved.

Q. Zhao, et al.
Inorganica Chimica Acta 490 (2019) 6–15
Scheme 1. Synthetic route to H L.
4
Table 1
Crystal and refinement parameter data for complexes 1–3.
Complex
1
2
3
Empirical formula
Formula weight
T (K)
C
39
H
36Cl
2
Zn
3
N
4
O
17
C
68
H
54Zn
4
EuN11
O
34
C
70
H
60Zn
4
NdN11O
35
1099.73
1982.66
2021.01
173.00(10)
1.54184
triclinic
P-1
294.21(11)
0.71073
monoclinic
P2/n
173.00(10)
0.71073
Wavelength (Å)
Crystal system
Space group
a (Å)
monoclinic
1
P2 /n
9.7720(5)
15.1890(7)
15.7665(5)
66.402(4)
79.564(4)
79.188(4)
2091.73(17)
2
11.8043(5)
18.7183(7)
21.9339(9)
90
12.0044(3)
33.8551(8)
22.8025(5)
90
b (Å)
c (Å)
α (°)
β (°)
91.662(4)
90
97.531(2)
90
γ (°)
3
V (Å )
4844.4(3)
2
9187.3(4)
4
Z
−
3
D
calc (g∙cm
)
1.746
1.359
1.461
Absorption coefficient (mm 1)
θ range for data collection (°)
F(0 0 0)
−
3.895
1.692
1.669
3.501–66.599
1116.0
3.370–26.022
1988.0
3.424–26.022
4068.0
h/k/l(minimum, maximum)
Crystal size (mm)
−11, 9/−18, 18/−18, 16
0.12 × 0.14 × 0.15
13757/7179
−14, 14/−20, 23/−16, 27
0.14 × 0.16 × 0.18
19845/9533
0.0394
−14, 13/−41, 39/−17, 28
0.14 × 0.15 × 0.21
35,539/18,052
0.0386
Reflections collected Rint
0
.0214
Independent reflection
6494
6621
12,757
Completeness to θ (%)
96.92
99.73
99.71
Data/restraints/parameters
Final R indices [I > 2σ (I)]
7179/27/616
9533/63/549
18052/126/1142
R
1
= 0.0542,
R
1
= 0.0472,
1
R = 0.0533,
wR
2
= 0.1452
= 0.1500
wR
2
= 0.1046
wR
2
= 0.1015
R indices (all data)
R
1
= 0.0589,
R
1
= 0.0743,
R = 0.0824,
1
wR
2
wR
2
= 0.1192
2
wR = 0.1161
2
Goodness-of-fit for (F )
1.038
1.031
1.032
Largest difference peak and hole (e Å−3)
1.705, −1.847
0.698, −0.570
0.830, −0.508
a
R
1
wR
= Σ‖F
o
| − |F
c
‖/Σ|F
o
|.
b
c
2
2
2
2
2
1/2
2
2
) + (0.0784P) + 1.3233P]−1, where P = (F 2
2
+ 2F 2
)/3.
2
= [Σw(F
o
− F
c
) /Σw(F
o
) ] , w = [σ (F
o
o
c
2
2
2
1/2
GOF = [Σw(F
o
− F
c
) /nobs − nparam)]
.
and 7-hydroxyl-4-methylcoumarin (98%) were purchased from Alfa
Aesar and used directly without purification. All other commercially
available solvents and chemicals were analytical reagent and bought
from Tianjin Chemical Reagent Factory. Elemental analyses (C, H and
N) were performed on a GmbH VarioEL V3.00 automatic elemental
analysis instrument. Elemental analyses for metals were carried out on
an IRIS ER/S-WP-1 ICP atomic emission spectrometer. Fourier trans-
Limited Company. Single crystal X-ray structure determinations were
determined by a SuperNova Dual, Cu at zero, Eos four-circle dif-
fractometer. Hirshfeld surface analyses and two-dimensional finger-
print plots of complexes 1–3 were calculated using Crystal Explorer
program.
−1
2.2. Synthesis of bis(salamo) ligand H4L
form Infrared spectra were conducted by using CsI (100–500 cm ) and
−
1
KBr (500–4000 cm
) pellets on a VERTEX70 FT-IR spectro-
1
,2-Bis(aminooxy)ethane and 8-formyl-7-hydroxy-4-methylcou-
marin were synthesized in accordance with the previously literatures
52,53]. Major synthetic route of H L is presented in Scheme 1.
-Formyl-7-hydroxy-4-methylcoumarin (408.3 mg, 2.0 mmol) dis-
solved in the methanol solution (30 mL) was slowly added to a colorless
photometer. UV–Vis absorption spectra were collected on a Shimadzu
UV-3900 spectrophotometer. Luminescent spectra were obtained on F-
[
4
7
000 spectrophotometer. Melting points were collected on a micro-
8
scopic melting point apparatus made by Beijing Taike Instrument
7

Q. Zhao, et al.
Inorganica Chimica Acta 490 (2019) 6–15
(
a) 1.0
0
0
0
.60
.55
.50
Complex 3
0
0
0
.8
.6
.4
Complex 2
Complex 1
0.45
0.40
0
.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
2
+
[
Zn ] / [H L]
4
H L
4
0.2
0.0
250
300
350
400
450
500
Wavelength(nm)
4
000
3500
3000
2500
2000 11500
1000
500
-
Wavenumber (cm )
0
.66
(b) 1.0
Fig. 1. FT-IR spectra of H
4
L and its complexes 1–3.
0.65
0
.64
0
0
0
.8
.6
.4
methanol solution (30 mL) of 1,2-bis(aminooxy)ethane (184.2 mg,
0.63
2
.0 mmol) and heated to reflux at 80 °C more than 4 h. Subsequently,
0
.62
the mixture solution was concentrated via vacuum distillation. The
mixture was separated by column chromatography using ethyl acetate:
chloroform = 1:5 and obtained 417.4 mg white intermediate product 2-
0.61
0
.5
1.0
1.53+
+
2.0
2.5
2
3
[LZn ] /[Eu ]
[
O-(1-ethyloxyamide)]oxime-4-methylcoumarinphenol.
A yellow ethanol solution (10 mL) of 2, 3-dihydroxybenzene-1,4-
dicarbaldehyde (83.1 mg, 0.5 mmol) was slowly added to
a di-
chloromethane solution (10 mL) of above-mentioned 2-[O-(1-ethylox-
yamide)]oxime-4-methylcoumarinphenol (278.3 mg, 1.0 mmol). The
mixture solution was heated and refluxed at 65 °C about 3 h before
being allowed to cool to room temperature. Subsequently, the solution
was filtered and washed with ethanol/hexane (1:4). Finally, the yellow
0.2
0.0
250
300
350
400
450
500
solid of H
for C34
.01%. IR (KBr; cm ): 1617 [v(C]N)], 1279 [v(Ar–O)], 1751 [v(C]
O)], 3444 [v(OeH)]. UV-Vis [in chloroform/ethanol (1:1)], λmax (nm)
4
L was collected. Yield, 42.5%. M.p. 181–182 °C. Anal. Calc.
Wavelength (nm)
H
30
N O12: C, 59.47; H 4.40; N, 8.16. Found: C, 59.69; H, 4.64; N,
4
−1
8
(
c) 1.0
0.74
0.72
−
5
[
2.5 × 10 M]: 285, 302, 316, 344.
0
.70
0
0
0
.8
.6
.4
2
.3. Synthesis of homotrinuclear complex 1
0.68
0.66
Zn(OAc) (6.59 mg, 0.03 mmol) dissolved in ethanol solution (2 mL)
2
0
.5
1.0
1.5
3+
2.0
2
+
of was added to dichloromethane solution (3 mL) of H
4
L (6.87 mg,
3
[LZn ] /[Nd ]
0
2
.01 mmol). The mixture solution was stirred at room temperature for
5 min, and the color of the solution turned yellow. Then, the mixture
was filtered and stood at room temperature approximately three weeks.
Several clear light colourless crystals were collected. Yield, 33.7%.
0.2
0.0
.
Anal. Calc. for [Zn
3
(L)(μ
2
-OAc)
(H
2 2
O)
2
] CH
2
Cl
2
(C39
H
36Cl
2
Zn
3
N
4
O
17):
C 42.59; H, 3.30; N, 5.09; Zn, 17.84. Found: C, 42.72; H, 3.48; N, 4.88;
−
1
Zn, 17.61%. IR (KBr; cm ): 1604 [v(C]N)], 1181 [v(Ar–O)], 1731 [v
−
3
250
300
350
400
450
500
(
C]O)]. UV-Vis [in ethanol], λmax (nm) [1.0 × 10 M]: 292, 312,
Wavelength (nm)
3
18, 356.
Fig. 2. UV-Vis spectra of the changes in the H
b) Eu(NO ; (c) Nd(NO
4
L upon addition of (a) Zn(OAc) ;
2
(
3
)
3
3
) .
3
2.4. Synthesis of heteropentanuclear complexes 2 and 3
Zn(OAc)
4.46 mg, 0.01 mmol) was dissolved in ethanol solution (2 mL), re-
spectively. The above solutions (4 mL) were added to the chloroform
2
(8.78 mg, 0.04 mmol) and Ln(NO
3
)
3
(Ln = Eu, Nd)
Yield,
(C
38.2%.
Anal.
Calc.
for
[Zn (L) Eu(NO ) (H O)]
4
2
3 3
2
(
H
Zn EuN O ): C, 41.19; H, 2.75; N, 7.77; Zn, 13.19; Eu, 7.66.
6
8
54
4
11 34
−1
Found: C, 41.30; H 2.88; N 7.64; Zn, 13.06; Eu, 7.51%. IR (KBr; cm ):
solution (2.0 mL) of H
4
L (13.74 mg, 0.02 mmol). Subsequently, the
1607 [v(C]N)], 1254 [v(Ar–O)], 1741 [v(C]O)]. UV–Vis [in ethanol],
−3
color of the mixed solution became yellow and was stirred for 40 min.
Then, the solution was filtered and stood undisturbed for about one
month at room temperature. Clear block-like yellow crystals for X-ray
crystallographic analysis were gained.
λ
(nm) [1.0 × 10 M]: 294, 313, 320, 361.
max
For [Zn Nd] complex 3, block-like transparent light yellow crystals.
4
Yield:
32.0%.
Analytical
calculation
for
[Zn (L) Nd
4
2
(NO ) (H O)]·CH CH OH (C
3
3
2
3
2
70 60
H
Zn NdN
4
11 35
O
): C, 41.60; H, 2.99; N,
For [Zn Eu] complex 2, block-like transparent dark yellow crystals.
4
8

Q. Zhao, et al.
Inorganica Chimica Acta 490 (2019) 6–15
Fig. 3. (a) Molecular structure of complex 1; (b) Coordination polyhedra for ZnII atoms of complex 1.
7
1
1
.62; Zn, 12.94; Nd, 7.14. Found (%): C, 41.72; H, 3.07; N 7.53; Zn,
3.1. FT-IR spectra
−
1
2.81; Nd, 7.02%. IR (KBr; cm ): 1605 [v(C]N)], 1240 [v(Ar–O)],
730 [v(C]O)], 3415 [v(OeH)]. UV–Vis [in ethanol], λmax (nm)
Infrared spectra of H
4
L and its complexes 1–3 showed various bands
−
3
−1
[
1.0 × 10 M]: 296, 315, 319, 358.
within the region 4000–400 cm
(Fig. 1).
−
1
Infrared spectra of H L exhibited a strong band at 3444 cm which
4
is connected with the phenolic OeH stretching vibration band.
2.5. X-ray crystallographic analysis
However, these bands were disappeared in complexes 1 and 2, in-
dicating that the phenolic OeH groups of H L are fully deprotonated. A
4
Suitable single crystals of complexes 1–3 were mounted on glass rod
new OeH stretching vibration band in complex 3 was observed at
−1
for determining crystal structures. X-ray diffraction data of complexes
around 3415 cm
corresponding to crystallizing ethanol molecule
−1
1
–3 were performed on a SuperNova (Dual, Cu at zero, Eos) dif-
[13]. The observed band in H
4
L at 1617 cm
was assigned to a
fractometer using the graphite monochromated Cu Kα (λ = 1.54184 Å)
and Mo Kα (λ = 0.71073 Å) radiation sources at 173.00(10),
characteristic C]N vibration. Meantime, these characteristic C]N vi-
bration bands of complexes 1–3 were found at 1604, 1607 and
−1
2
94.21(11), 173.00(10) K, respectively. Multi-scan absorption correc-
1605 cm , respectively [23]. Complexes 1–3 were shifted to lower
−1
tions were applied. Crystal structures were solved using direct methods
frequencies by 10–13 cm , demonstrating the coordination of the ni-
II
and refined anisotropically by the full-matrix least-squares techniques
trogen atoms with Zn atoms. The expected Ar-O vibration band of H L
4
2
−1
based on F with SHELX-2014 program. Contributions to scattering due
was seen at ca.1279 cm . Nevertheless, these bands in complexes 1–3
−1
to these very large solvent accessible VOID(S) in structure were re-
moved using the SQUEEZE routine of PLATON, the structures were then
refined again using the data generated. The non-hydrogen atoms were
refined anisotropically with displacement parameters. The positions for
hydrogen atoms were fixed on geometrically idealized positions and
refined via a riding model. Selected data of parameters and refinement
of complexes 1–3 are summarized in Table 1.
shifted to 1181, 1254 and 1240 cm , respectively, moving to low
frequencies [29]. In the IR spectrum of H L, the typical C]O vibration
4
−1
band emerged at 1751 cm , and those of complexes 1–3 were detected
−1
at approximately 1731, 1741 and 1730 cm , respectively. Most im-
portant of all, two new medium intensity bands for complexes 1–3
−1
appeared at approximately 523, 530 and 520 cm
corresponding to
−1
Zn-N bond, and two characteristic bands at 454, 464 and 457 cm
were attributed to the formation of Zn-O bonds [42]. The facts men-
tioned above are in accordance with the results of crystal X-ray dif-
fractions.
3
. Results and discussion
The H L and its corresponding complexes 1–3 were synthesized and
4
3
.2. UV-Vis absorption spectra
characterized by FT-IR, UV-Vis absorption spectra, single-crystal X-ray
crystallography, Hirshfeld surfaces analyses and luminescent spectra.
The UV-Vis titration spectra of H L
4
in chloroform:ethanol
−5
−1
(
v:v = 1:1) solution (2.5 × 10 mol L
) and its corresponding
9

Q. Zhao, et al.
Inorganica Chimica Acta 490 (2019) 6–15
Table 2
Hydrogen bonding and CeH…π interactions (Å,°) of complexes 1–3.
D − H···A
d(D − H)
d(H···A)
d(D···A)
∠D − X···A
Symmetry code
Complex 1
O17-H17A···O3
C10-H10···O2
C11-H11B···O14
C22-H22A···O16
C23-H23···O10
C6-H6···O11
0.84
0.93
0.97
0.97
0.93
0.93
0.93
2.09
2.29
2.51
2.35
2.27
2.53
2.56
3.00
2.660(5)
2.681(6)
3.332(6)
3.197(7)
2.654(6)
3.423(8)
3.480(5)
3.758(5)
124
105
143
145
104
161
172
136
–
–
–
–
–
−x, 1−y, 1−z
−x, 1−y, −z
−x, 1−y, 1−z
C13-H13···O12
C12-H12A···Cg1
Complex 2
C11-H11···O2
C11-H11···O3
C24-H24···O10
C24-H24···O8
C27-H27···O14
C13-H13A···O13
C32-H32···O7
0.93
0.93
0.93
0.93
0.93
0.97
0.93
2.32
2.54
2.35
2.53
2.50
2.49
2.48
2.681(8)
2.938(8)
2.698(6)
2.940(6)
3.223(7)
3.017(10)
3.342(8)
102
106
102
107
135
114
155
3/2 − x, y, 3/2 − z
3/2 − x, y, 3/2 − z
3/2 − x, y, 3/2 − z
2 − x, 1-y, 1-z
1/2 + x,−y,1/2 + z
Complex 3
C2-H2···O26
0.93
0.93
0.97
0.93
0.93
0.93
0.97
0.93
0.93
0.97
0.97
0.93
0.93
2.43
2.33
2.52
2.32
2.49
2.33
2.50
2.44
2.57
2.45
2.50
2.39
2.59
2.73
3.142(7)
2.701(6)
3.443(9)
2.670(6)
2.854(7)
2.688(8)
3.419(7)
3.157(8)
3.457(9)
3.157(7)
3.163(8)
3.272(6)
3.496(8)
3.639(7)
133
103
160
102
104
102
158
134
160
130
125
158
164
159
C11-H11···O2
C22-H22A···O31
C24-H24···O10
C45-H45···O8
C45-H45···O13
C47-H47A···O25
C61-H61···O32
C21-H21···O32
C22-H22B···O3
C46-H46B···O27
C55-H55···O23
C65-H65···O19
C34-H34A···Cg2
1 − x, 1 − y, 2 − z
1/2 − x, −1/2 + y, 3/2 − z
1 − x, 1 − y, 1 − z
−1/2 + x, 3/2−y, −1/2 + z
1/2 + x, 3/2 − y, 1/2 + z
−1 + x, y, z
Symmetry codes: Cg1 for complex 1 are the centroids of atoms C24–C29; Cg2 for complex 3 are the centroids of atoms C35–C36–C37–C38–C42-C43.
complexes 1–3 in ethanol solution (1.0 × 10−3 mol L−1) were collected
Zn3 atoms locate into N
O cores of the ligand and are bound by four
2
2
with the range of 250–550 nm and are shown in Fig. 2.
donor atoms (Zn1-N1, 2.130(4) Å; Zn1-N2, 2.102(3) Å; Zn1-O3,
1.975(3) Å; Zn1-O6, 2.038(3) Å and Zn3-N3, 2.111(3) Å; Zn3-N4,
2.119(4) Å; Zn3-O7, 2.039(3) Å; Zn3-O12, 1.980(3) Å) from the sym-
Obviously, UV-Vis spectrum of H L possessed four absorption peaks
4
at approximately 285, 302, 316 and 344 nm, respectively. The first peak
at 285 nm is appointed to the π-π* transition and the second and third
peaks at 302 and 316 nm are assigned to π-π* transition of the C]N
bonds [33]. The fourth peak at 344 nm is assigned to the n-π* transi-
tions for carbonyl group. However, complex 1 exhibited four absorption
peaks at about 292, 312, 318 and 356 nm, which were bath-
ochromically shifted [46]. The phenomenon mentioned above man-
4
−
metrical completely deprotonated (L)
units and one oxygen (Zn1-
O14, 1.992(3) Å and Zn3-O16, 1.970(3) Å) atom from two μ-acetate
anion. Therefore, the Zn1 and Zn3 atoms form the slightly distorted
trigonal bipyramidal geometries, which being calculated by τ values are
estimated to be τ
1
= 0.766 and τ = 0.768, respectively. Meanwhile,
2
central Zn2 atom is also surrounded by oxygen atoms: two phenolic
oxygen (Zn2-O6, 2.087(3) Å and Zn2-O7, 2.041(3) Å) atoms arising
II
ifests the coordination of the H
4
L with the Zn atom.
4
−
from two fully deprotonated (L)
units, and two oxygen (Zn2-O13,
In the titration experiment of complex 1, the ethanol solution of Zn
1
.988(3) Å and Zn2-O15, 2.004(4) Å) atoms of two μ-acetate anions,
(
OAc)
2
were added gradually to solution of H L, and then the colour of
4
II
and one oxygen (Zn2-O17, 2.010(4) Å) atom of one coordinated water
molecule. Consequently, the central Zn2 atom possesses a geometry of
slightly distorted tetragonal pyramid which being calculated by τ value
above solution turned yellow. After Zn ions were added in excess of 3
equiv, the absorbance kept stable. Evidently, the titration curve showed
II
the formation of a 1:3 trinuclear Zn complex and is shown in Fig. 2(a).
…
…
is estimated to be τ = 0.491. The Zn1 Zn2 and Zn2 Zn3 distance are
3
As the UV-Vis absorption spectra of complexes 1–3 are similar change
3
.456(4) and 3.402(4) Å, respectively (Table S1).
and could obtain the same conclusions. Clearly, the spectroscopic ti-
II
III
Supra-molecular interactions of complex 1 are built by extensive
tration displayed the formation of 2:4:1 (H L:Zn :Ln ) pentanuclear
4
…
hydrogen bonding and CeH π interactions, which play a significant
complexes 2 and 3 and presented in Fig. 2(b) and (c).
role in the crystal structure. Major hydrogen bonding data of complexes
1
–3 are presented in Table 2. Five pairs of intra-molecular O17-
… … … …
3.3. Crystal structure descriptions
H17A O3, C10-H10 O2, C11-H11B O14, C22-H22A O16 and C23-
…
H23 O10 hydrogen bonding interactions are shown in Fig. 4(a)
3
.3.1. Crystal structure of complex 1
[
54–57]. In addition, a 2D supra-molecular architecture is connected by
… …
Single crystal X-ray crystallography revealed complex 1 is a 1:3
one pair of CeH π (C12–H12A Cg1 (Cg1: C24-C25-C26-C27-C28-
4
−
II
(
(L) :Zn ) trinuclear structure. Complex 1 crystallizes in a triclinic
…
C29)) interaction (Fig. 4(b)). With the help of CeH π and hydrogen
II
system, space group of P-1 and is comprised of three Zn atoms, one
bonding interactions, an infinite 3D supra-molecular structure is built
in Fig. 4(c).
4
−
completely deprotonated (L) units, one coordinated water molecule,
two μ -acetate anions and one crystallizing dichloromethane molecule.
2
The molecular structure of complex 1 is presented in Fig. 3. Selected
bond lengths and angles of complexes 1–3 are listed in Table S1.
3.3.2. Crystal structure of complex 2
II
As depicted in Fig. 3, three Zn atoms are five-coordinated. Zn1 and
X-ray crystallography indicated the crystal structure of complex 2,
10

Q. Zhao, et al.
Inorganica Chimica Acta 490 (2019) 6–15
Fig. 5. (a) Molecular structure of complex 2; (b) Coordination polyhedra for
II
III
Zn and Eu atoms of complex 2.
#
1
#1
#1
4−
N1 , N2 , O1AA ) from the two fully deprotonated (L)
Zn1-N1, 2.044(4) Å; Zn1-N2, 2.130(4) Å; Zn1-O1AA, 2.095(3) Å and
Zn1-O5, 1.977(3) Å) and one oxygen (Zn1-O12, 1.995(5) Å) atom of the
units
(
–
II
#1
coordinated NO
five-coordinated and form slightly distorted trigonal bipyramidal geo-
metries with τ value is estimated to be τ = 0.622. Meantime, the other
3
anion. Therefore, the Zn atoms (Zn1 and Zn1 ) are
4
Fig. 4. (a) Intra-molecular hydrogen bonding interactions of complex 1; (b)
II
#1
Zn atoms (Zn2 and Zn2 ) are bonded by two nitrogen (Zn2-N3,
…
CeH π interactions of complex 1; (c) 3D supra-molecular structure of complex
2
1
.130(4) Å and Zn1-N4, 2.045(4) Å) atoms and two oxygen (Zn2-O6,
.978(3) Å and Zn2-O9, 2.064(3) Å) atoms of two completely depro-
1
.
4
−
tonated (L) units, and one oxygen (Zn2-O15, 1.985(4) Å) atom from
–
which is different from complex 1 mentioned above. Complex 2 crys-
tallizes in the monoclinic system, space group of P2/n, consisting of two
half coordinated water and half coordinated NO
3
molecule.
II
#1
Consequently, the Zn atom (Zn2 and Zn2 ) is five-coordinated pos-
4
−
II
III
fully deprotonated (L)
units, four Zn atoms, one Eu atom, one
sessing the geometry of slightly distorted trigonal bipyramid with τ
–
III
coordinated water molecule and three coordinated NO
3
anions.
value is estimated to be τ
5
= 0.622. The Eu atom is surrounded by
4
−
II
III
Therefore, complex 2 forms a rarely reported 2:4:1 ((L) :Zn :Eu
)
eight phenolic oxygen (Eu1-O1AA, 2.431(3) Å; Eu1-O5, 2.420(3) Å;
#1
hetero-pentannuclear structure [6] which is different from the pre-
viously reported structure of 1:1:1 [9,10,13,38], 1:2:1 [37]
Eu1-O6, 2.409(3) Å; Eu1-O9, 2.449(3) Å; Eu1-O1AA , 2.431(3) Å; Eu-
#1 #1 #1
O5 , 2.420(3) Å; Eu1-O6 , 2.409(3) Å and Eu1-O9 , 2.449(3) Å)
4
−
2
+
3+
(
Table S1) atoms from two fully deprotonated (L)
ligands, and the
(
L:M :Ln ) of salamo-like complexes. The structure of complex 2 is
III
Eu atom is eight-coordinated and possesses a distorted square anti-
prism geometry.
illustrated in Fig. 5.
II
#1
The Zn atoms (Zn1 and Zn1 ) sited in N
2
O cores of the bis
2
Moreover, five pairs of intra-molecular C11-H11…O2, C11-
(
salamo)-like ligands are embraced by four atoms (N1, N2, O1AA, O5 or
11

Q. Zhao, et al.
Inorganica Chimica Acta 490 (2019) 6–15
Fig. 6. (a) Intra-molecular hydrogen bonding interactions of complex 2; (b) 3D
supram-olecular structure of complex 2.
…
…
…
…
H11 O3, C24-H24 O10, C24-H24 O8 and C27-H27 O14 hydrogen
bonding interactions are shown in Fig. 6(a). An infinite 3D supra-mo-
lecular structure is linked by two pairs of intermolecular C13-
Fig. 7. (a) Molecular structure of complex 3; (b) Coordination polyhedra for
II
III
Zn and Nd atoms of complex 3.
…
…
H13A O13 and C32-H32 O7 hydrogen bonding interactions in
Fig. 6(b) [58–60].
trigonal bipyramidal geometry, which being calculated by τ value is
II
estimated to be τ
6
= 0.637. Meanwhile, the other Zn atoms (Zn2, Zn3
and Zn4) are coordinated with several donor atoms (Zn2-N3, 2.133(5)
Å; Zn2-N4, 2.043(4) Å; Zn2-O6, 1.969(4) Å; Zn2-O9, 2.105(3) Å; and
Zn3-N5, 2.040(4) Å, Zn3-N6, 2.126(4) Å, Zn3-O12, 2.084(4) Å, Zn3-
O17, 1.968(3) Å; and Zn4-N7, 2.115(4) Å, Zn4-N8, 2.034(4) Å, Zn4-
3
.3.3. Crystal structure of complex 3
X-ray crystallography showed the crystal structure of complex 3 is a
4
−
II
III
2
:4:1 ((L) :Zn :Nd ) hetero-pentanuclear structure, which is similar
4
−
O18, 1.959(3) Å, Zn4-O21, 2.083(3) Å) from the two (L)
units and
to that of complex 2 mentioned above. Complex 3 crystallizes in the
II
three oxygen (Zn2–O31, 2.021(6) Å; Zn3-O25, 2.040(4) Å and Zn4-
monoclinic system, space group of P2
1
/n and is made up of four Zn
–
III
4−
O28, 2.031(9) Å) atoms of the two coordinated NO
3
anions (Table S1).
atoms, one Nd atom, two fully deprotonated (L)
units, three co-
–
Thus, the Zn2, Zn3 and Zn4 atoms have the slightly distorted trigonal
ordinated NO
3
anions, one coordinated water molecule and one crys-
bipyramidal geometries, which being calculated by τ values are esti-
tallizing ethanol molecule. The crystal structure of complex 3 is shown
mated to be τ
7
= 0.518, τ
8
= 0.606 and τ = 0.610, respectively. Fur-
9
in Fig. 7.
III
II
thermore, the Nd atom is also embraced by eight phenolic oxygen
As shown in Fig. 7, all Zn atoms are located into N
2
O cavities from
2
III
4
−
atoms from the two bis(salamo)-like ligands. Thus, the Nd atom is
the two deprotonated (L)
units and five-coordinated with the same
eight-coordinated and possesses a distorted square antiprism geometry.
geometries. Zn1 atom is surrounded by two nitrogen (Zn1-N1, 2.034(4)
Å and Zn1-N2, 2.111(4) Å) atoms and two oxygen (Zn1-O1, 2.067(3) Å
Supra-molecular interactons exist in complex 3. Eight pairs of intra-
…
…
…
4
−
molecular C2-H2 O26, C11-H11 O2, C22-H22A O31, C24-
… … … …
and Zn1-O24, 1.968(3) Å) atoms from the fully deprotonated (L)
H24 O10, C45-H45 O8, C45-H45 O13, C47-H47A O25 and C61-
units, and one oxygen (Zn1-O35, 2.013(5) Å) atom from the co-
ordinated water molecule. Therefore, Zn1 atom has a slightly distorted
…
H61 O32 hydrogen bonding interactions are shown in Fig. 8(a)
12

Q. Zhao, et al.
Inorganica Chimica Acta 490 (2019) 6–15
[
61,62]. In addition, a 2D supra-molecular architecture is built by
…
…
CeH π (C34-H34A Cg2 (Cg2: C35-C36-C37-C38-C42-C43)) interac-
tions in Fig. 8(b) [63,64]. A complicated 3D supra-molecular structure
is observed in Fig. 8(c).
3.4. Hirshfeld surfaces analyses
The Hirshfeld surface analyses and 2D fingerprint plots of complex 1
were carried out using Crystal Explorer program. Complexes 2 and 3
did not undergo Hirshfeld surfaces analyses due to the presence of rare
earth ions. For each point on the Hirshfeld isosurface, two distances, d
e
(
the distance from the point to the nearest nucleus external to the
surface) and d
i
(the distance to the nearest nucleus internal to the
surface), are defined. They have been mapped with dnorm (standard
high resolution), d
e
, d
i
, shape index and curvedness, and are illustrated
L produces spherical
in Fig. 9 [65].
When mapped with the dnorm, the surface of H
4
red depressions, indicating the presence of mainly of the type CeH···O
interactions and other visible depressions correspond to H···H and C···H
interactions. More intense red depressions in complex 1 are seen on the
Hirshfeld surfaces which marks the O···H/H···O interactions persisting.
The 2D fingerprint plots could explain the atom pair contacts of com-
plex 1, which could quantify the intermolecular interactions.
Meanwhile, it could be decomposed to highlight contributions from
different interactions. The 2D fingerprint plots of C···H/H···C, H···H and
O···H/H···O interactions of complex 1 are depicted in Fig. 10. The pro-
portion of C···H/H···C, interaction in complex 1 covers 8.4% of the
Hirshfield surfaces, and the proportions of H···H and O···H/H···O inter-
actions in complex 1 and cover 35.9 and 13.9%, respectively. As can be
seen from the above facts, the proportions of H···H is relatively stronger
than C···H/H···C and O···H/H···O interactions [66].
3.5. Luminescences
In view of the excellent luminescent properties of zinc(II) and
coumarin, the luminescent behaviors of H L and its corresponding
4
−3
complexes 1–3 were measured in ethanol solution (1.0 × 10 M)
within wavelength range of 330–650 nm and displayed in Fig. 11. Ac-
cording to the spectra, H L upon excitation at 315 nm exhibited a
4
strong emission peak at 386 nm and that could be attributed to intra-
ligand π-π* transitions [67,68]. Furthermore, the spectrum of com-
plexes 1–3 displayed relatively weak emission peaks at ca. 515, 508 and
5
13 nm upon excitation at 315 nm, respectively. Compared to H L,
4
three emission peaks of complexes 1–3 are bathochromically-shifted
and that could be assigned to L-M charge-transfer transitions (LMCT)
II
due to the coordination of nitrogen and oxygen atoms to metal (Zn ,
III
III
Eu and Nd ) atoms [13,36].
4
. Conclusions
Three homo-trinuclear Zn and hetero-pentanuclear Zn -Ln
II
II
III
(
(
Ln = Eu, Nd) complexes with a containing coumarin-skeleton bis
salamo)-like ligand H
4
L were synthesized and structurally character-
II
ized. In complexes 1–3, all Zn atoms are located in the N
2
O sites and
2
III
Eu/Nd atoms are embraced by eight phenolic oxygen atoms from the
4
…
−
two fully deprotonated (L)
units. All the complexes have abundant
hydrogen bonding and CeH π interactions. The Hirshfeld surfaces and
D fingerprint plots can explain the atom pair contacts of the crystal,
which can quantify the intermolecular interactions. Compared to H L,
the luminescences of complexes 1–3 show bathochromically-shifted
2
Fig. 8. (a) Intra-molecular hydrogen bonding interactions of complex 3; (b)
4
…
CeH π interactions of complex 3; (c) 3D supra-molecular structure of complex 3.
13

Q. Zhao, et al.
Inorganica Chimica Acta 490 (2019) 6–15
Fig. 9. Hirshfeld surfaces of complex 1 mapped with dnorm, d
e
, d , shape index and curvedness.
i
Fig. 10. 2D fingerprint plots of complex 1 with the major decomposition plots.
owing to the coordination of nitrogen and oxygen atoms from H
4
L with
Acknowledgements
metal atoms, which can be further investigated as a new type of lu-
minescent material.
This work was supported by the National Natural Science
Foundation of China (21761018) and the Program for Excellent Team
of Scientific Research in Lanzhou Jiaotong University (201706), which
is gratefully acknowledged.
14

Q. Zhao, et al.
Inorganica Chimica Acta 490 (2019) 6–15
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Appendix A. Supplementary data
4
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CCDC 1888874, 1888872 and 1888873 contain the supplementary
crystallographic data for complexes 1, 2 and 3. These data can be ob-
tained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.
html, or from the Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk. Supplementary data to this article can be
found online at https://doi.org/10.1016/j.ica.2019.02.040.
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