Structurally characterized homo-trinuclear ZnII and hetero-pentanuclear [ZnII4LnIII] complexes constructed from an octadentate bis(Salamo)-based ligand: Hirshfeld surfaces, fluorescence and catalytic properties

Article abstract of DOI:10.1039/c9nj00014c

One homo-trinuclear 3d and five novel windmill-type hetero-pentanuclear 3d-4f complexes [Zn₃(L)(OAc)₂(H₂O)]·CH₂Cl₂ (1), [Zn₄(L)₂Sm(NO₃)₂(EtOH)₂]N

Full text of DOI:10.1039/c9nj00014c

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Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
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Structurally characterized homo-trinuclear ZnII and
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hetero-pentanuclear [ZnII LnIII] complexes constructed from
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a octadentate bis(Salamo)-based ligand: Hirshfeld surfaces,
fluorescent and catalytic properties
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Xiao-Yan Li, Quan-Peng Kang, Chang Liu, Yang Zhang, Wen-Kui Dong*
One homo-trinuclear 3d and five novel windmill-type hetero-pentanuclear 3d–4f
complexes
[Zn3(L)(OAc)2(H2O)]·CH2Cl2
(1),
(2),
(3),
(4),
and
[Zn4(L)2Sm(NO3)2(EtOH)2]NO3·H2O·2CHCl3
[Zn4(L)2Eu(NO3)2(EtOH)2]NO3·C2H5OH·2CHCl3
[Zn4(L)2Gd(NO3)2(EtOH)2]NO3·C2H5OH·2CHCl3
[Zn4(L)2Tb(NO3)2(EtOH)2]NO3·C2H5OH
(5)
[Zn4(L)2Dy(NO3)2(EtOH)2]NO3·C2H5OH·2CHCl3 (6) were synthesized by the
reactions of a new bis(Salamo)-based tetraoxime ligand (H4L) with Zn(OAc)2·2H2O
and Ln(NO3)3·6H2O (Ln = Sm, Eu, Gd, Tb and Dy), respectively. The structures of
complexes 1-6 were characterized via elemental analyses, FT-IR, UV-Vis
spectroscopy and single crystal X-ray crystallography, and their fluorescence
properties, catalytic activities and Hirshfeld surface analysis were studied.
Introduction
Salen-based ligands (R–CH=N–(CH2)n–N=CH–R) and their metal complexes have
been extensively investigated in modern coordination chemistry for several decades.1–
6 A number of homo- and heterometallic complexes have been derived from salen and
its analogous ligands.7–9 Their metal complexes are used as catalysts,10,11 non-linear
* School of Chemical and Biological Engineering, Lanzhou Jiaotong University,
Lanzhou 730070, P. R. China. E-mail: dongwk@126.com; Tel: +86 931 4938703
† CCDC: numbers 1875819-1875824 for complexes 1–6.

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optical materials,12,13 molecular recognitions,14–16 supramolecular architectures,
biological fields19,20 and so forth. Numerous studies on 3d-4f heterometallic
complexes have been conducted and extensively studied because some of them
exhibit interesting magnetic,21–23 luminescent24 and catalytic properties.25,26 In
particular, the zinc-lanthanide complexes are of interest because of the visible and
near-infrared luminescence resulting from lanthanide f-f transitions.27,28 The
luminescence applications of lanthanides are a consequence of their narrow emission
bands, negligible environmental influences, large Stokes shifts and relatively long
luminescence lifetimes.29,30 However, 3d-4f hetero-nuclear metal complexes with
Salamo-like ligands have rarely been reported.31,24
DOI: 10.1039/C9NJ00014C
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Herein, we designed and synthesized one homotrinuclear ZnII and five novel
windmill-type heteropentanuclear [ZnII LnIII] (Ln = Sm, Eu, Gd, Tb and Dy)
4
complexes of a new octadentate bis(Salamo)-based tetraoxime ligand (H4L). In order
to increase the fluorescence intensities of its corresponding complexes, two
naphthaldehyde groups are introduced into the ligand H4L. About the proportioning of
ligand : metal ion, it is mainly determined by the types of ligands, and different
ligands determined the ratio of ligand : metal. Compared with the 3-alkoxy Salamo
ligand reported previously, the structures of the 3d-4f complexes formed by the ligand
H4L are not 1:2 ((L)2- :Mn+ (n=2, 3)).8 Compared with the 3-alkoxy bis(Salamo)-based
ligand, the ligand H4L has no O6 recognition site. When a small radius 3d metal(II)
atom is introduced into the ligand H4L, the structure of the formed complex does not
change. However, when a 4f metal(III) atom having a larger radius is introduced,
since there is no 3-alkoxy group in the new ligand H4L, in order to satisfy the
coordination of the 4f metal(III) atom, novel 2 : 5 ((L)4- : Mn+ (n = 2, 3))
windmill-type hetero-pentanuclear 3d-4f metal complexes were formed (Chart 1),
instead of common 1 : 3 ((L)4- : Mn+ (n = 2, 3) )) complexes24. Fluorescence properties,
catalytic activities of these novel 2 : 5 ((L)4- : Mn+ (n = 2, 3)) 3d-4f metal complexes
were studied. Hirshfeld surface analysis of complex 1 was discussed.

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Salen-based complexes have been widely used in catalytic fields, and functions in
a lot of important chemical reactions such as reduction, oxidation and
polymerization.31–33 However, there are few studies on the catalytic activities of
Salamo-based metal(II/III) complexes, only the catalytic activities of CuII 34 and CoII
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complexes have been studied untill now. The study on catalytic activity of
Salamo-based ZnII or [ZnIILnIII] complex has not been reported up to now, which
provide a new idea for the application of Salamo-based ZnII and [ZnIILnIII]
complexes.
Chart 1 The structural contrast of 3d-4f complexes based on 3-alkoxy Salamo,
3-alkoxy bis(Salamo) and above-mentioned bis(Salamo) ligand H4L.
Experimental Section
General details.
2-hydroxy-1-naphthaldehyde (99%), 1,2-dibromoethane, 1,2-dimethoxybenzene,
TMEDA, n-butyllithium and boron tribromide were purchased from Alfa Aesar and
used without further purification. Other reagents and solvents were analytical grade
reagents from Tianjin Chemical Reagent Factory. Elemental analyses for C, H and N
were detected with a GmbH VariuoEL V3.00 automatic elemental analysis instrument
(Berlin, Germany). ZnII, SmIII, EuIII, GdIII, TbIII and DyIII were obtained using an IRIS
ER/S-WP–1 ICP atomic emission spectrometer (Berlin, Germany). Melting points

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were obtained by a microscopic melting point apparatus made by Beijing Taike
Instrument Company Limited. IR spectra (400–4000 cm−1) were determined by a
Vertex 70 FT-IR spectrophotometer (Bruker, Billerica, MA, USA), with samples
prepared as KBr pellets. UV-vis absorption spectra were recorded on a Shimadzu
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UV-3900 spectrometer (Shimadzu, Japan). H NMR spectra were determined by
German Bruker AVANCE DRX-400/600 spectroscopy. MS spectrum was obtained
on a Bruker Daltonics APEX-II 47e spectrometer. The powder X-ray diffractions
(PXRD) were recorded by a RIGAKU-DMAX2500 X-ray diffractometer using Cu
Kα radiation (λ= 0.154 nm) at a scanning rate of 5º / min for 2θ ranging from 5º to 50º.
X-ray single crystal structure determinations for complexes 1-6 were carried out on a
Bruker APEX-II CCD. Fluorescence spectra were recorded on a F-7000 FL
spectrophotometer.
X-ray crystallographic analysis.
X-ray single crystal diffraction data of complexes 1-6 were recorded using a Bruker
APEX-II CCD diffractometer with a monochromatic Mo-Kα radiation (λ = 0.71073 Å)
source at 173(2), 153(2), 153(2), 153(2), 153(2) and 296(2) K, respectively. The LP
factor and semi-empirical absorption were using SADABS. The single crystal
structures were solved via the direct methods (SHELXS-2016),35 and all the hydrogen
atoms were included at the calculated positions and constrained to ride on their parent
atoms. All non-hydrogen atoms were refined anisotropically via a full-matrix
least-squares procedure on F2 with SHELXL-2016.36 Data collection and refinements
of these complexes were listed in Table 1.
Table 1 X-ray crystallographic data for complexes 1-6.
Complex
1
2
3
Empirical formula
Formula weight
T (K)
C39H36Zn3N4O13Cl2
1035.73
C74H68SmZn4N11O28Cl6 C76H72EuZn4N11O28Cl6
2183.92
153(2)
2213.58
153(2)
173(2)
Wavelength (Å)
0.71073
0.71073
0.71073

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Crystal system
Space group
a (Å)
Triclinic
P-1
Monoclinic
C12/c1
Monoclinic
C12/c1
16.8834(9)
23.1409(12)
24.3047(12)
90
15.7572(9)
16.4079(9)
16.4852(9)
90.038(2)
104.887(2)
97.172(2)
4084.5(4)
4
16.8229(9)
23.2495(12)
24.2036(14)
90
b (Å)
c (Å)
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α (°)
β (°)
108.673(2)
90
108.679(2)
90
γ (°)
V (Å3)
Z
8968.3(9)
8995.6(8)
4
4
Dcalc (g∙cm–3)
1.684
1.617
1.634
Absorption coefficient (mm–1) 1.950
1.959
1.999
F (000)
2104
4388
4456
Crystal size (mm)
θ Range (°)
Index ranges
0.220 x 0.190 x 0.180
2.542 to 25.009
–18 h  14
0.260 × 0.250 × 0.220
2.604-27.582
–21  h  21
–30  k  30
–31  l  27
38065/10314
[Rint = 0.0445]
99.6% (θ = 25.242)
10314 / 149 / 671
1.066
0.260 × 0.220 × 0.190
2.020-27.691
–20  h  21
–19 k  19
–30  k  20
–19  l  19
–31  l  31
Reflections collected/unique
30142/14368
[Rint = 0.0402]
99.6% (θ = 25.010)
14368 / 25 / 1112
1.016
40357/10453
[Rint = 0.0646]
99.8% (θ = 25.242)
10453 / 101 / 675
1.053
Completeness to θ
Data/restraints/parameters
GOF
Final R1, wR2 indices
R1, wR2 indices (all data)
Largest diff. peak and hole
0.0483, 0.1233
0.0691, 0.1347
0.0501, 0.1291
0.0714, 0.1411
0.0528, 0.1213
0.0837, 0.1342
3
3
3
-
-
-
1.319 and -1.222 e.Å
1.453 and -0.872 e.Å
1.065 and -0.635 e.Å
Complex
Empirical formula
Formula weight
T (K)
4
5
6
C76H72GdZn4N11O28Cl6
2218.87
C74H70TbZn4N11O28
1981.81
153(2)
C76H72DyZn4N11O28Cl6
2224.12
153(2)
296(2)
Wavelength (Å)
Crystal system
Space group
a (Å)
0.71073
0.71073
Monoclinic
P121/c1
13.542(3)
28.886(7)
19.183(4)
90
0.71073
Monoclinic
C12/c1
Monoclinic
C12/c1
16.9752(18)
23.090(2)
24.837(3)
90
16.9466(9)
23.0127(12)
24.9394(15)
90
b (Å)
c (Å)
α (°)
β (°)
111.300(2)
90
96.675(4)
90
111.278(2)
90
γ (°)
V (Å3)
9069.8(16)
4
7453(3)
4
9063.0(9)
4
Z

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Dcalc (g∙cm–3)
1.625
2.022
4460
1.766
2.300
4000
1.630
2.116
4468
Absorption coefficient (mm–1)
F (000)
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7
8
9
Crystal size (mm)
θ Range (°)
0.220 × 0.190 × 0.180
2.492 to 27.642
–20  h  22
0.250 × 0.190 × 0.180
1.280-25.000
–16  h  16
0.260 × 0.220 × 0.190
2.491 to 27.656
–21  h  22
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Index ranges
–30  k  30
–24  k  34
–29  k  30
–32  l  20
–22  l  22
–32  l  27
Reflections collected/unique
34092/10510
33737/12830
[Rint = 0.0783]
97.8% (θ = 25.000)
12830 / 72 / 1090
1.059
40263/10506
[Rint = 0.0786]
99.8% (θ = 25.242)
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1.115
[Rint = 0.0564]
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1.049
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Data/restraints/parameters
GOF
Final R1, wR2 indices
R1, wR2 indices (all data)
Largest diff. peak and hole
0.0846, 0.1698
0.0877, 0.2247
0.0492, 0.1196
0.1328, 0.192
1.425 and -1.198 e.Å-3
0.1249, 0.2660
1.635 and -1.483 e.Å-3
0.0744, 0.1298
1.138 and -0.559 e.Å-3
Synthesis of the bis(Salamo) ligand (H4L).
The reaction steps of the bis(Salamo)-based tetraoxime ligand (H4L) can be seen from
Scheme 1. 2,3-Dihydroxybenzene-1,4-dicarbaldehyde, 1,2-bis(aminooxy)ethane and
2-[O-(1-ethyloxyamide)]oxime-2-naphthol were prepared according to a similar
method.37,38
Scheme 1 Synthetic route to the bis(salamo)-based tetraoxime ligand H4L.
To an ethanol solution (20 mL) of 2,3-dihydroxybenzene-1,4-dicarbaldehyde
(332.3 mg, 2.0 mmol) was added to an ethanol solution (30 mL) of
2-[O-(1-ethyloxyamide)]oxime-2-naphthol (985.1 mg, 4 mmol). The solution was
stirred at 55 °C for 8 h, cooling to room temperature, the precipitation was filtered and

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washed with n-hexane to obtained yellow powder. Yield: 1083.4 mg, 87%. m.p.: 198–
5
6
200 ºC. Anal. Calc. for C34H30N4O8: C, 65.59; H, 4.86; N, 9.00%. Found: C, 65.65; H,
7
8
1
4.94; N, 8.92%. H NMR (400 MHz, CDCl3) δ 10.82 (s, 2H), 9.70 (s, 2H), 9.17 (s,
9
2H), 8.25 (d, J = 2.5 Hz, 2H), 7.96 (d, J = 8.7 Hz, 2H), 7.80 – 7.72 (m, 4H), 7.50 (t, J
= 7.7 Hz, 2H), 7.35 (t, J = 7.5 Hz, 2H), 7.20 (d, J = 9.0 Hz, 2H), 6.75 (s, 2H), 4.56 (s,
8H). Mass Spectrometry (MS) m/z: 621.18 [H4L - H]-. (Fig. S1). IR (KBr, cm–1): 3435
(m), 2995 (m), 2833 (m), 1603 (m), 1239 (m), 1173 (m). UV-vis (CHCl3/CH3CH2OH
1:1 v/v): λmax (εmax): 302, 313, 341 and 355 nm.
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Preparation of complexes 1-6.
Complex 1 was synthesized by the reaction of H4L with Zn(OAc)2. Complexes 2-6
were synthesized by the reactions of H4L with Zn(OAc)2 and Ln(NO3)3 (LnIII = SmIII,
EuIII, GdIII, TbIII and DyIII), respectively (Scheme 2).
Scheme 2 Syntheses of complexes 1–6.
[Zn3(L)(OAc)2(H2O)]·CH2Cl2 (1) A solution of 6.58 mg (0.03 mmol) of
Zn(OAc)2·2H2O in CH3CH2OH (3.0 mL) was added to the solution of H4L (6.23 mg,
0.01 mmol) in CH2Cl2 (4 mL) and stirred for 15 min, then filtered the solution. Three

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weeks later, diffraction quality yellow acicular crystals were obtained on slow
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evaporation of the solution in open atmosphere.
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[Zn4(L)2Sm(NO3)2(EtOH)2]NO3·H2O·2CHCl3 (2) A solution of 8.77 mg (0.04
mmol) of Zn(OAc)2·2H2O in CH3CH2OH (2.0 mL) was added to a solution of 12.45
mg (0.02mmol) of H4L in CHCl3 (4 mL), The color of the mixed solution instantly
changes from light yellow to dark yellow, a solution of 4.44 mg (0.01 mmol)
Sm(NO3)3·6H2O in CH3CH2OH (2 mL) was then added. The mixture was stirred for
15 minutes and then filtered at room temperature. Two weeks later, some yellow
block crystals suitable for X-ray diffraction were formed and filtered carefully.
Complexes 3, 4, 5 and 6 were prepared by a similar procedure as for complex 2.
Complex 1, yellow acicular crystals. Yield: 5.70 mg, 55%. Anal. calc. for
C39H36Zn3N4O13Cl2: C, 45.22; H, 3.50; N, 5.41; Zn, 18.94%. Found: C, 45.28; H,
3.56; N, 5.32; Zn, 19.02%. IR (KBr, cm–1): 2996 (m), 2837 (m), 1600 (m), 1184 (m),
1247 (m), 1184 (m). UV-Vis (CHCl3/CH3CH2OH 1:1 v/v), λmax (nm) (εmax): 318 and
385 nm.
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Complex 2, yellow block crystals. Yield: 11.56 mg, 62%. Anal. calc. for
C74H68SmZn4N11O28Cl6: C, 40.70; H, 3.14; N, 7.05; Zn, 11.98; Sm, 6.88%. Found: C,
40.78; H, 3.21; N, 6.97; Zn, 12.02; Sm, 6.91%. IR (KBr, cm–1): 3341 (m), 2996 (m),
2836 (m), 1612 (m), 1393 (m), 1184 (m), 1244 (m), 1175 (m). UV-Vis
(CHCl3/CH3CH2OH 1:1 v/v), λmax (nm) (εmax): 326 and 381 nm.
Complex 3, yellow block crystals. Yield: 10.82 mg, 58%. Anal. calc. for
C76H72EuZn4N11O28Cl6: C, 41.24; H, 3.28; N, 6.96; Zn, 11.81; Eu, 6.86%. Found: C,
41.29; H, 3.32; N, 7.03; Zn, 11.86; Eu, 6.92%. IR (KBr, cm–1): 3442 (m), 2990 (m),
2834 (m), 1613 (m), 1394 (m), 1241 (m), 1179 (m). UV-Vis (CHCl3/CH3CH2OH
1:1v/v), λmax (nm) (εmax): 325 and 382 nm.
Complex 4, yellow block crystals. Yield: 9.17 mg, 49%. Anal. calc. for
C76H72GdZn4N11O28Cl6: C, 41.14; H, 3.27; N, 6.94; Zn, 11.78; Gd, 7.09%. Found: C,
41.21; H, 3.31; N, 6.87; Zn, 11.84; Gd, 7.12%. IR (KBr, cm–1): 3442 (m), 2994 (m),

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2835 (m), 1617 (m), 1396 (m), 1242(m), 1176 (m). UV-Vis (CHCl3/CH3CH2OH 1:1
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v/v), λmax (nm) (εmax): 324 and 381 nm.
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Complex 5, yellow block crystals. Yield: 12.68 mg, 66%. Anal. calc. for
C74H70TbZn4N11O28: C, 44.85; H, 3.56; N, 7.77; Zn, 13.20; Tb, 8.02%. Found: C,
44.92; H, 3.62; N, 7.71; Zn, 13.26; Tb, 8.08%. IR (KBr, cm–1): 3439 (m), 2996 (m),
2835 (m), 1609 (m), 1395 (m), 1244 (m), 1177 (m). UV-Vis (CHCl3/CH3CH2OH 1:1
v/v), λmax (nm) (εmax): 322 and 382 nm.
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Complex 6, yellow block crystals. Yield: 11.63 mg, 62%. Anal. calc. for
C76H72DyZn4N11O28Cl6: C, 41.04; H, 3.26; N, 6.93; Zn, 11.76; Dy, 7.31%. Found: C,
41.09; H, 3.32; N, 6.87; Zn, 11.81; Dy, 7.38%. IR (KBr, cm–1): 3439 (m), 2994 (m),
2834 (m), 1612 (m), 1399 (m), 1243 (m), 1179 (m). UV-Vis (CHCl3/CH3CH2OH 1:1
v/v), λmax (nm) (εmax): 319 and 382 nm.
Results and discussion
IR spectra.
The binding modes were determined by comparing several intense bands of the ligand
H4L and its complexes in the IR spectra (Fig. 1). The stretching band of the free
ligand H4L is observed at 1603 cm–1 correspond to the stretching vibrations of the
C=N bonds while complexes 1-6 are observed at 1609-1617 cm–1. The spectral
changes of complexes 1-6 shows that H4L has coordinated with ZnII atoms.39,40 In
addition, the band at 1239 cm-1 in the spectrum of the free ligand H4L can be assigned
to a typical Ar–O stretching band. In complexes 1-6, the bands shifted to lower
frequencies by ca. 5-10 cm−1, indicating that the M-O bonds are formed between the
metal(II/III) atoms and oxygen atoms of phenolic groups.41 The O–H stretching band
of the free ligand H4L was observed at ca. 3435 cm−1 that belongs to the phenolic
hydroxyl group, whereas complexes 2-6 shows a stretching band at ca. 3441, 3442,
3442, 3439 and 3439 cm−1 that belongs to coordinated methanol molecules or ethanol
molecules.42 Meanwhile, these bands at 1393, 1394, 1396, 1395 and 1399 cm-1 of
complexes 2-6 can be assigned to nitrate ions, indicating the nitrates are contained in

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the crystal structures.43
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Fig. 1 IR spectra of H4L and its corresponding complexes 1–6.
UV–vis spectra.
The UV–Vis absorption spectra of H4L with its complexes 1-6 in chloroform/ethanol
solutions (v:v = 1:1) are shown in Fig. 2.
In the UV-vis titration experiment of complex 1, the color of a solution of H4L
(1.0 × 10-5 M) gradually changed from colorless to light yellow upon addition of a
solution of ZnII acetate (1.0 × 10-3 M). The absorption spectrum of H4L mainly shows
four relatively strong absorption peaks at ca. 302, 313, 341 and 355 nm. The
absorption peaks at ca. 302 and 313 nm can be assigned to the π-π* transitions of the
naphthalene rings.44 The other two absorption peaks at ca. 341 and 355 nm can be
assigned to the intra-ligand π-π* transition of the oxime group.45 Compared with the
free ligand H4L, the gradual addition of ZnII ions brought changes to the absorption
peaks, these peaks gradually disappeared with the emergence of new peaks at ca. 318
and 385 nm, which indicating the coordination of ZnII atoms with the (L)4- units.46
However, when the added amount of the ZnII ions reached 3.0 equiv, the absorbance
of the solution became stable, keep addition of the ZnII, the absorbance of the solution
was not changed, which indicates 1:3 reaction stoichiometry between ZnII and H4L.
In the UV–vis titration experiment of complex 2, the spectrum of complex 1
showed absorption peaks at 318 and 385 nm. However, upon addition of 1 equiv of

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SmIII ions, these peaks gradually disappeared with the emergence of new peaDkOsI:a10t.1c0a39./C9NJ00014C
326 and 381 nm, which indicating the coordination of SmIII atoms with the [Zn3(L)]2+
units.47 The titration curves also clearly indicated that the stoichiometry between SmIII
and [Zn3(L)]2+ was 1:2. As the UV–Vis absorption spectra of complexes 3–6 are alike,
which obtain the same results.
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Fig. 2 (a) UV−Vis spectra of the changes in the H4L upon addition of
Zn(OAc)2·2H2O; (b) UV−Vis spectra of the changes in complex 1 upon addition of
(b) Sm(NO3)3·6H2O; (c) Eu(NO3)3·6H2O; (d) Gd(NO3)3·6H2O; (e) Tb(NO3)3·6H2O;
(f) Dy(NO3)3·6H2O.
Description of the crystal structure.
The structures of complexes 1–6 were determined by single-crystal X-ray diffractions.
Selected bond lengths and angles are given in Tables S1–2.
Crystal structure description of complex 1.
Complex 1 crystallizes in the triclinic crystal system, space group P-1, and each unit
cell comprises two crystallographically independent and chemically equivalent
homo-trinuclear complexes (Fig. 3). Complex 1 consists of three ZnII atoms, one (L)4−
unit, two coordinated water molecules and two μ-acetato ions. Meanwhile, Zn1 and
Zn2 atoms are situated in the N2O2 coordination cavities, Zn3 is respectively bridged
by Zn1 and Zn2 through two deprotonated phenoxo donors O17 and O18 and two
syn−syn bridging acetate ions in a μ2-η1: η1 fashion.48 Zn1 and Zn2 atoms presenting a
ZnN2O3 coordination sphere, and assumed distorted trigonal bipyramidal coordination

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geometries (τ1 = 0.82 and τ2 = 0.74).49 However, Zn3 atom presenting a ZnO5
coordination sphere, and assumed distorted square-pyramidal geometry (τ3 = 0.046).49
In the crystal structure of complex 1, there are seven intramolecular hydrogen
bonds (O13–H13D···O4, O13–H13C···O10, O23–H23B···O24, O23–H23A···O14,
C12–H12B···O5, C23–H23C···O8 and C50–H50B···O20).50,51 In addition, complex
1 molecule formed a 2D supramolecular structure by intermolecular hydrogen bonds
(C16–H16···O16, C51–H51A···O10 and C54–H54···O12) and C22-H22B···π
interactions (C22-H22B···Cg1 (Cg1=C63-C64-C69-C70-C71-C72)) (Fig. 4).52
DOI: 10.1039/C9NJ00014C
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Fig. 3 (a) Molecule structure of complex 1 (hydrogen atoms and solvent molecules
are omitted for clarity). (b) Coordination polyhedrons for ZnII atoms of complex 1.

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Fig. 4 (a) View of the intramolecular hydrogen bonding interactions of complex 1. (b)
View of an infinite 2D supramolecular structure of complex 1.
Crystal structures description of windmill-type complexes 2, 3, 4 and 6.
As depicted in Fig. 5, the X-ray structure of complex 2 revealed a hetero-pentanuclear
structure, crystallizing in the monoclinic system, space group C12/c1. The
corresponding hydrogen bonds of complexes 1–6 are summarized in Table S2.

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Fig. 5 (a) Molecule structure of complex 2 (hydrogen atoms and solvent molecules
are omitted for clarity). (b) Coordination polyhedrons for ZnII and SmIII atoms of
complex 2. (c) View of the dihedral angles between the basal planes Zn1-O4-Sm1 and
Zn2-O8-Sm1 of complex 2.
Complex 2 consists of four ZnII atoms, one SmIII atom, two (L)4− units, two
coordinated ethanol molecules and two nitrate groups, one crystalling water molecule,
two trichloromethane molecules and one nitrate group. The ZnII atoms presenting
ZnN2O3 coordination sphere. The Zn1 and Zn2 (Zn1#1 and Zn2#1) atoms are all made
of the N2O2 sites of the salamo moieties and one coordinated nitrate group, which
assumed a distorted trigonal bipyramidal coordination geometry (τ1 = 0.66 and τ2 =
0.71).49 The SmIII atom exhibits a SmO8 coordination sphere, which is made of eight
phenoxo donors (O1, O4, O5, O8, O1#1, O4#1, O5#1 and O8#1) of two completely
deprotonated (L)4- units, while the central SmIII atom is octa-coordinated with a
distorted square antiprism geometry.53 Within complex 2, the distances between the
metallic centers are Zn1···Sm1 = 3.564 and Zn2···Sm1 = 3.578 Å. Meanwhile, the

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angle between the plane Zn1-O4-Sm1 and the plane Zn2-O8-Sm1 is 89.887(3)° (Fig.
5 (c)). Complex 2 forms a novel 2 : 5 ((L) : M) windmill-type hetero-pentanuclear
3d-4f complex, which is completely different from the structures of 1 : 2, 1 : 3 ((L) :
M) reported earlier in the Salamo-type 3d-4f complexes.8,24
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Fig. 6 (a) View of the intramolecular hydrogen bonding interactions of complex 2. (b)
View of an infinite 2D supramolecular structure of complex 2.

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In complex 2, there are four pairs of significant intramolecular hydrogen bonds
(C13–H13A···O11, C24–H24···O7, C33–H33···O10 and C36–H36C···O9) (Fig. 6
(a)).50,51 In addition, complex 2 molecules formed a 2D supramolecular structure by
intermolecular hydrogen bonds (Fig. 6 (b)).52
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Complexes 2, 3, 4 and 6 are isostructural, therefore only the crystal structure of
complex 2 was described. The crystal structures of complexes 3, 4 and 6 are shown in
Figs. 7, 9 and 11, respectively. As shown in Figs. 8, 10 and 12, there are some
intramolecular hydrogen bonds interactions, and the infinite 2D supramolecular
networks are formed by intermolecular C–H···O hydrogen bond interactions in
complexes 2, 3, 4 and 6.52

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Fig. 7 (a) Molecule structure of complex 3 (hydrogen atoms and solvent molecules
are omitted for clarity). (b) Coordination polyhedrons for ZnII and EuIII atoms of
complex 3.

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Fig. 8 (a) View of the intramolecular hydrogen bonding interactions of complex 3. (b)
View of an infinite 2D supramolecular structure of complex 3.

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Fig. 9 (a) Molecule structure of complex 4 (hydrogen atoms and solvent molecules
are omitted for clarity). (b) Coordination polyhedrons for ZnII and GdIII atoms of
complex 4.

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Fig. 10 (a) View of the intramolecular hydrogen bonding interactions of complex 4.
(b) View of an infinite 2D supramolecular structure of complex 4.

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Fig. 11 (a) Molecule structure of complex 6 (hydrogen atoms and solvent molecules
are omitted for clarity). (b) Coordination polyhedrons for ZnII and DyIII atoms of
complex 6.

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Fig. 12 (a) View of the intramolecular hydrogen bonding interactions of complex 6.
(b) View of an infinite 2D supramolecular structure of complex 6.
Crystal structure description of windmill-type complex 5.
Complex 5 crystallizes in the monoclinic crystal system, space group P121/c1. X-ray
crystallography clearly shows the formation of complex 5. Different from complexes
1, 2, 3, 4 and 6, it consists of four ZnII atoms, one TbIII atom, two (L)4- units, two
coordinated ethanol molecules, two nitrate groups and one crystalling ethanol
molecule, one nitrate group (Fig. 13).
The ZnII atoms are also located in the N2O2 sites, and four ZnII atoms are also
penta-coordinated. Zn1 and Zn2 atoms assumed distorted square-pyramidal
geometries (τ1 = 0.37 and τ2 = 0.44). Zn3 and Zn4 atoms assumed distorted trigonal
bipyramidal coordination geometries (τ3 = 0.62 and τ4 = 0.56). The TbIII atom is also
located in the O8 site that consists of eight phenoxy oxygen atoms, forming the
geometry of a distorted square antiprism.

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Fig. 13 (a) Molecule structure of complex 5 (hydrogen atoms and solvent molecules
are omitted for clarity). (b) Coordination polyhedrons for ZnII and TbIII atoms of
complex 5.

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Fig. 14 (a) View of the intramolecular hydrogen bonding interactions of complex 5.
(b) View of an infinite 2D supramolecular structure of complex 5.
The main interactions in complex 5 are listed in Table S2, some of intramolecular
hydrogen bonds (C2–H2···O13, C2–H2···O20, C22–H22A···O26, C33–H33···O12,
C33–H33···O17, C45–H45···O2, C47–H47A···O22, C56–H56A···O18, C56–

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H56A···N3, C57–H57A···N4, C58–H58···O7, C69–H69A···O8, O27–H27DAO·I·: 1·0O.102339/C9NJ00014C
and O26–H26B···O19) are formed.50,51 Besides, four intermolecular hydrogen bonds
(C55–H55···O25, C39–H39···O17, C46–H46B···O22 and C55–H55···O25) in
complex 5, which adopts a 2D supramolecular structure (Fig. 14).52
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Hirshfeld surface analysis.
The Hirshfeld surface analysis54 provides a three-dimensional picture of close
contacts in a crystal, and these contacts can be given in a fingerprint plot. The
Hirshfeld surface of complex 1 has been mapped over (a) dnorm, (b) shape index and (c)
curvedness in Fig. 15. Other complexes did not undergo Hirshfeld surfaces analyses
due to the presence of rare earth ions.
2D fingerprint plots are important intermolecular interactions appear as distinct
spikes.55 The O···H/H···O intermolecular interactions are distinct spikes in Fig. 16.
The O···H interactions are expressed by a spike in the bottom left (donor) area of the
fingerprint plot, the H···O interactions are expressed by a spike in the bottom right
(acceptor) region of the fingerprint plot. The contribution of different interactions to
the Hirshfeld surface has been given in Fig. 16. The proportion of C···H/H···C,
Cl···H/H···Cl, O···H/H···O, and H···H interactions comprises 16.0%, 11.7%, 19.2%
and 41.6% of the total Hirshfeld surfaces for each molecule of complex 1,
respectively. The main intermolecular interactions of total Hirshfeld surface is
belonged to H···H interaction.
Fig. 15 Hirshfeld surface mapped with (a) dnorm; (b) Shape index; (c) Curvedness for
complex 1.

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New Journal of Chemistry
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View Article Online
DOI: 10.1039/C9NJ00014C
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Fig. 16 Fingerprint plot of complex 1: full and resolved into full and resolved into
C···H, Cl···H, O···H and H···H contacts showing the percentages of contacts
contributed to the total Hirshfeld surface area of molecule.
Fluorescent properties.
The ligand (H4L) and its corresponding complexes 1-6 were excited at 385 nm (λex)
respectively (Fig. 17). The emission spectrum of the ligand exhibits a broad emission
band, and the emission maximum at 454 nm, which can be assigned to the π-π*
electronic transitions in the ligand.56 Compared with H4L, the absorption peaks of
complexes 1 and 3–6 are bathochromically-shifted, which is may originate from the
ligand-to-metal-charge transfer (LMCT) emission,57 The order of fluorescence
intensity is H4L > [ZnII] > [ZnII GdIII] > [ZnII DyIII] > [ZnII EuIII] > [ZnII TbIII]. The
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fluorescence intensity of ZnII complex is stronger than that of [ZnII LnIII] (Ln = Eu,
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Gd, Tb and Dy) complexes, which may be due to the decrease of conjugate plane due
to the coordination of Ln (Sm, Eu, Gd, Tb and Dy) atoms. In addition, one can
observe several visible emission bands from complex 2 containing SmIII as lanthanide
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ion at 562, 598 and 645 nm (Fig. 17). These peaks correspond to the G5/2–6H5/2,
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4G5/2–6H7/2 and G5/2–6H9/2 transitions, respectively. The transition at G5/2–6H7/2
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belongs to the magnetic dipole transition, and the much stronger intensity of G5/2–
6H9/2 is assigned to the electric dipole transition.58,59 Meanwhile, a broad band at 439
nm upon excitation at 385 nm, which is assigned to the π–π* transitions of the ligand
H4L. The SmIII ion emission was sensitized by the [Zn3(L)]2+ unit and ligand-to-metal
energy transfer (LMET) occurred efficiently in complex 2.60 In other words, the
appearance of the characteristic emission bands reveals that the ligand H4L could act
as an antenna group, sensitizing SmIII-based luminescence.61 Complexes 3-6 does not