Luminescent properties of heterotrinuclear 3d–4f complexes constructed from a naphthalenediol-based acyclic bis(salamo)-type ligand

Article abstract of DOI:10.1016/j.saa.2017.04.061

Heterotrinuclear 3d–4f complexes with a naphthalenediol-based acyclic bis(salamo)-type ligand have been synthesized and structurally characterized. Spectral titrations clearly show that the heterotrinuclear complexes [Zn₂(L)La(OAc)₃] (1), [Zn₂(L)Ce(OAc)₃] (2) and [Zn₂(L)Dy(OAc)₃(CH₃OH)]·CH₂Cl₂ (3) are acquired by the substitution reaction of the obtained homotrinuclear Zn(II) complex with 1 equiv. of Ln(NO₃)₃ (Ln^3?+?=?La^3?+, Ce^3?+ and Dy^3?+). Two Zn(II) ions are penta- and hexa-coordinated with geometries of distorted tetragonal pyramid and octahedron. La(III) ion is deca-coordinated, adopting a distorted bicapped square antiprism geometry. Ce(III) ion is nona-coordinated with geometry of distorted capped square antiprism as well as Dy(III) ion. The different coordination modes of acetate ions in complexes 1, 2 and 3 lead to different coordination numbers of the lanthanide(III) ions. Furthermore, the structures and fluorescence properties have been discussed.

Full text of DOI:10.1016/j.saa.2017.04.061

Accepted Manuscript
Luminescent properties of heterotrinuclear 3d–4f complexes
constructed from a naphthalenediol-based acyclic bis(salamo)-
type ligand
Wen-Kui Dong, Shan-Shan Zheng, Jin-Tong Zhang, Yang Zhang,
Yin-Xia Sun
PII:
DOI:
Reference:
S1386-1425(17)30315-3
doi: 10.1016/j.saa.2017.04.061
SAA 15114
Spectrochimica Acta Part A: Molecular and Biomolecular
Spectroscopy
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Revised date:
Accepted date:
10 January 2017
30 March 2017
18 April 2017
Please cite this article as: Wen-Kui Dong, Shan-Shan Zheng, Jin-Tong Zhang, Yang
Zhang, Yin-Xia Sun , Luminescent properties of heterotrinuclear 3d–4f complexes
constructed from a naphthalenediol-based acyclic bis(salamo)-type ligand. The address
for the corresponding author was captured as affiliation for all authors. Please check if
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ACCEPTED MANUSCRIPT
Luminescent properties of heterotrinuclear 3d-4f complexes
constructed
from
a
naphthalenediol-based acyclic
bis(salamo)-type ligand
Wen-Kui Dong,* Shan-Shan Zheng, Jin-Tong Zhang, Yang Zhang, Yin-Xia Sun
Abstract
Heterotrinuclear 3d-4f complexes with a naphthalenediol-based acyclic
bis(salamo)-type ligand have been synthesized and structurally characterized.
Spectral titrations clearly show that the heterotrinuclear complexes
[Zn2(L)La(OAc)3]
(
1
),
[Zn2(L)Ce(OAc)3]
(
2
)
and
[Zn2(L)Dy(OAc)3(CH3OH)]
·
CH2Cl2 (
3
) are acquired by the substitution reaction
of the obtained homotrinuclear Zn(II) complex with 1 equiv of Ln(NO3)3 (Ln3+ =
La3+, Ce3+ and Dy3+). Two Zn(II) ions are penta- and hexa-coordinated with
geometries of distorted tetragonal pyramid and octahedron. La(III) ion is
deca-coordinated, adopting a distorted bicapped square antiprism geometry. Ce(III) ion
is nona-coordinated with geometry of distorted capped square antiprism as well
as Dy(III) ion. The different coordination modes of acetate ions in complexes
and lead to different coordination numbers of the lanthanide(III) ions.
Furthermore, the structures and fluorescence properties have been discussed.
1, 2
3
Keywords: Heterotrinuclear complex; Bis(salamo)-type ligand; Synthesis; Luminescent
property
1. Introduction
Salen-type [1-7] and salamo-type [8-19] complexes are well known for their
potential applications in many areas, such as biological fields [20-25], nonlinear optical
materials [26], catalysis [27-28], magnetism [29-32]. As the superior functional
* 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 1520694-1520696

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properties in optoelectronic devices, medicine, separation, ions recognition, lanthanide
complexes have recently attracted much attention [33-39]. Meanwhile, trivalent
lanthanide ions possess large radius, high coordination numbers and flexible
coordination geometries [40]. Especially, lanthanide ions have variable coordination
environments and a special 4f electron configuration with large spin moments and
strong spin-orbit coupling, so that the lanthanide complexes display amazing optical and
magnetic properties [41-42]. Based on the sharp f-f transitions and high quantum yields,
it is often thought that lanthanide complexes are the most important components in
pursuit of new luminescence materials [43-46].
Herein, as an extension of our previous studies [47-49], a novel bis(salamo)-type
tetraoxime ligand H4L is synthesized by introducing a naphthalenediol ring on the
ligand, which has a greater conjugation system and coordination ability, can be expected
to form lanthanide complexes with better optical properties. It is well known that acetate
ions often play an important role in coordination chemistry which can adopt various
binding modes such as terminal monodentate, chelating to one metal centre, bridging
bidentate in a syn-syn, syn-anti and anti-anti, and bridging tridentate to two metal
centres [50]. In this paper, heterotrinuclear complexes [Zn2(L)La(OAc)3] (1),
[Zn2(L)Ce(OAc)3] (2) and [Zn2(L)Dy(OAc)3(CH3OH)]·CH2Cl2 (3), have been
synthesized and structurally characterized. In complex 1, two acetate ions bridge Zn2+
and La3+ ions in a common µ2-fashion, another acetate ion chelates La3+ ion as a
bidentate ligand. While in complex 2, all acetate ions bridge Zn2+ and Ce3+ ions via
µ2-fashion. It is unexpected that one acetate ion of complex 3 only coordinates with
Zn2+ ion as a monodentate ligand. Thus, these monodentate and chelating bidentate
configurations of the coordinated acetate ions rarely exist in the documented
salamo-type complexes to the best of our knowledge [17-19, 51].
2. Experimental
2.1. Materials and instrumentation
2-Hydroxy-3-methoxybenzaldehyde (99%) was purchased from Alfa Aesar.
The other reagents and solvents were purchased from Shanghai Darui Chemical

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Fine Chemicals Company. All chemicals were of analytical grade and used
without further purification. C, H, and N analyses were obtained using a GmbH
VarioEL V3.00 automatic elemental analysis instrument. Melting points were obtained
by the use of a microscopic melting point apparatus made in Beijing Taike Instrument
1
Limited Company, and the thermometer was uncorrected. H NMR spectra were
recorded using a Mercury-400BB spectrometer at 400 MHz. IR spectra were recorded
on a VERTEX70 FT-IR spectrophotometer, with samples prepared as KBr (4000-400
cm-1) pellets. UV–Vis absorption spectra were recorded on a Hitachi U-3900H
spectrometer. Luminescence spectra in solution were recorded on a Hitachi F-7000
spectrometer.
2.2. Synthesis of the ligand H4L
The reaction steps involved in the synthesis of the bis(salamo)-type
tetraoxime ligand (H4L) are shown in Scheme 1 [52-57].
Scheme 1 Synthesis route to bis(salamo)-type ligand H4L
The
mixture
ethanol
solution
of
2,3-dihydroxynaph-thalene-1,4-dicarbaldehyde (175.2 mg, 0.80 mmol) and
2-[O-(1-ethyloxyamide)]oxime-6-methoxyphenol (449.0 mg, 1.98 mmol) was
heated at 55 °C for 2h. After cooling to room temperature, the precipitate was
filtered off, obtained light yellow crystalline solid. Yield: 423.4 mg, 83.7%. m.p.:

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172-174 °C. Anal. calc. for C32H32N4O10 (%): C, 60.75; H, 5.10; N, 8,86. Found
(%): C, 60.64; H, 5.23; N, 8.94. 1H NMR (400MHz, CDCl3): δ 11.03 (s, 2H), 9.82
(s, 2H), 9.14 (s, 2H), 8.29 (s, 2H), 7.97 (q, J = 3.2 Hz, 2H), 7.41 (q, J = 6.0, 2.9
Hz, 2H), 7.06-6.68 (m, 6H), 4.58 (t, 8H), 3.89 (s, 6H). IR (KBr; cm1): 1607
[ν(C=N)], 1250 [ν(ArO)], 3172 [ν(OH)], UVVis [in chloroform/methanol (1:1)],
λmax (nm) (log ɛ) [3.0  105 M]: 269 (4.42), 342 (4.03), 360 (4.12), 378 (4.05).
2.3. Synthesis of homotrinuclear Zn(II) complex
A solution of Zn(OAc)2∙2H2O (6.58 mg, 0.030 mmol) in methanol (3 mL) was
added to a solution of the ligand H4L (6.32 mg, 0.010 mmol) in chloroform (3 mL) at
room temperature. The color of the solution immediately turned yellow. The mixture
was filtered and the filtrate was allowed to stand at room temperature for about four
weeks. The solvent was partially evaporated and several yellow prismatic single crystals
were obtained. Yield: 5.63 mg, 41.2 %; Anal. Calc. for C41H45Cl9N4O16Zn3 (%): C
36.07; H 3.32; N 4.10. Found (%): C 35.96; H 3.40; N 3.97. IR (KBr; cm1): 1604
[ν(C=N)], 1245 [ν(ArO)], 3392 [ν(OH)], UVVis [in chloroform/methanol (1:1)],
λmax (nm) (log ɛ) [3.3  105 M]: 280 (4.35), 370 (4.04), 396 (3.99), 416 (3.92).
2.4. Preparation of heterotrinuclear complexes 1, 2 and 3
A solution of Zn(OAc)2∙2H2O (6.58 mg, 0.030 mmol) in methanol (1 mL) and
La(OAc)3∙H2O (3.34 mg, 0.010 mmol) in water/methanol (1:3, 2 mL) were added to a
solution of H4L (6.32 mg, 0.010 mmol) in chloroform (3 mL), and the resulting solution
was concentrated to dryness. The solid was redissolved in chloroform/methanol/ethanol
(3:2:1, 6 mL). The mixture was filtered and the filtrate was allowed to stand at room
temperature for several weeks. Complexes 2 and 3 were prepared by a similar procedure
as complex 1.
Complex 1, yellow crystals. Yield: 7.0 mg, 65.2 %. Elemental analysis: Anal. calc.
for C38H37LaN4O16Zn2 (%): C 42.44; H 3.47; N 5.21. Found (%): C 42.39; H 3.51; N
5.15. IR (KBr; cm-1): 1610 [ν(C=N)], 1242 [ν(ArO)], UV-Vis [in chloroform/methanol
(1:1)], λmax (nm) (log ɛ) [3.3 × 10-5 M]: 280 (4.61), 370 (4.29), 396 (4.25), 416 (4.20).
Complex 2, yellow crystals. Yield: 7.3 mg, 67.4 %. Elemental analysis: Anal. calc.

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for C38H37CeN4O16Zn2 (%): C 42.39; H 3.46; N 5.20. Found (%): C 42.35; H 3.52; N
5.17. IR (KBr; cm-1): 1610 [ν(C=N)], 1237 [ν(ArO)], UV-Vis [in chloroform/methanol
(1:1)], λmax (nm) (log ɛ) [3.3 × 10-5 M]: 280 (4.60), 370 (4.29), 396 (4.25), 416 (4.20).
Complex 3, yellow crystals. Yield: 8.2 mg, 67.3 %. Elemntal analysis: Anal. calc.
for C40H43Cl2DyN4O17Zn2 (%): C, 39.51; H, 3.56; N, 4.61. Found (%): C 39.44; H 3.53;
N 4.65. IR (KBr; cm-1): 1610 [ν(C=N)], 1240 [ν(ArO)], 3434 [ν(OH)], UV-Vis [in
chloroform/methanol (1:1)], λmax (nm) (log ɛ) [3.3 × 10-5 M]: 280 (4.60), 370 (4.29),
396 (4.25), 416 (4.21).
2.5. X-ray Crystallographic Analysis
Intensity data for complex 1 were collected on a Bruker Smart 1000 CCD area
detector with Mo Kα radiation (k = 0.71073 Å) at 293.33(10) K. While intensity data
for complex 2 and 3 were collected on a SuperNova (Dual, Cu at zero, Eos)
diffractometer with Mo Kα radiation (k = 0.71073 Å) at 293.33(10) and 293.78(10) K,
respectively. Data collection and reduction were performed using CrysAlisPro and then
processed with Olex2. The structures were solved with ShelXS-2018 and refined with
ShelXL-2015.All hydrogen atoms were added in calculated positions. The
crystallographic data are summarized in Table 1.
Table 1 Crystallographic data and refinement parameters for complexes 1, 2 and 3
Complex
1
2
3
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C38H37LaN4O16Zn2
1075.36
C38H37CeN4O16Zn2
1076.57
C40H43Cl2DyN4O17Zn2
1215.92
293.33(10)
0.71073
293.33(10)
0.71073
293.78(10)
0.71073
triclinic
triclinic
monoclinic
P21/c
P1
P1
10.4562(4)
14.5979(7)
18.4521(7)
73.452(4)
75.215(3)
13.4231(12)
13.5379(12)
15.6521(13)
64.689(9)
78.336(8)
12.6510(3)
13.6894(3)
26.8174(7)
90
b (Å)
c (Å)
(o)
β(o)
103.515(3)

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Complex
1
2
3
γ(o)
Volume (Å3)
77.263(4)
2577.05(19)
2
70.323(8)
2415.4(4)
2
90
4515.77(19)
Z
4
Calculated density (g∙cm-3) 1.386
1.480
1.788
Absorption
(mm-1)
coefficient
1.799
1.977
2.887
θ range for data collection
3.298 to 26.021
1076.0
3.372 to 26.021
1078.0
3.312 to 26.022
2428.0
(°)
F(000)
-12, 13/-19, 18/-24, -16, 11/-16, 16/-18,
h/k/l(min, max)
-15, 15/-16, 16/-33, 32
22
19
Crystal size (mm)
Collected reflections
Unique reflections
Rint
0.35  0.36  0.38
19108
0.09  0.12  0.21
16682
0.34  0.35  0.36
33323
9912
9506
8876
0.035
0.090
0.048
parameters / restraints
R1(I > 2σ(I))a
wR2(I > 2σ(I))a
R1(all data)b
wR2(all data)b
Goodness-of-fit for (F2)c
Largest difference peak and
hole (e Å-3)
555 / 0
0.0353
0.0787
0.0470
0.0737
0.985
555 / 0
0.0717
0.1441
0.1625
0.1122
0.983
604 / 0
0.0402
0.1044
0.0525
0.0951
1.082
0.83, -0.70
0.77, -0.61
1.50, -0.85
2
2 2 1/2
2
a. R1 = Σ‖Fo| − |Fc‖/Σ|Fo|; b. wR2 = [Σw(Fo - Fc2)2/Σw(Fo ) ] , w = [σ2(Fo ) + (0.0784P)2 +
2
2
1.3233P]-1, where P = (Fo + 2Fc2)/3; c. GOF = [Σw(Fo - Fc2)2/nobs - nparam)]1/2;
3. Results and discussion
The substitution reaction of the Zn(II) complex with 1 equiv of La3+ has been used
to synthesize complex 1, meanwhile, complexes 2 and 3 are prepared by the same way.
The ligand H4L and its corresponding complexes 1, 2 and 3 are stable in air. The ligand
has remarkably soluble in chloroform, DMF and DMSO, but slightly soluble in
methanol, ethanol, acetone and ethyl acetate. Complex 1 could dissolve in the methanol,
chloroform and DMF, but slightly soluble in ethanol. The similar solubility of
complexes 2 and 3 is measured. Mixing solution of methanol and chloroform as a

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benign solvent is selected to accomplish spectral experiments.
3.1. IR spectra
IR spectra of the free ligand H4L and its corresponding complexes 1, 2 and 3
exhibit various bands in the region of 4000-400 cm-1. The most important bands
are given in Table 2 including the ligand H4L, Zn(II) complex and 3d-4f
complexes 1, 2 and 3. The O-H stretching band of the free ligand H4L has been
observed at 3172 cm-1. This band is disappeared in the spectra of complexes
and , which indicates that the phenolic OH groups of H4L have been completely
deprotonized and coordinated to the metal ions [58-59]. The characteristic band
1
2
of the OH group is found in complex
coordinated methanol molecule.
3
at 3419 cm-1, which belongs to the
The free ligand H4L exhibits characteristic band of C=N at 1607 cm-1, which
are shifted by 3 cm-1 in complexes
and , indicating that the metal ions are
coordinated by N2O2 donor atoms of (L)4- units, which is similar to previously
reported Zn(II) complexes [60-61]
The Ar-O stretching frequency appears at 1250 cm-1 for the ligand H4L, while
the Ar-O stretching frequencies in complexes and are observed at 1242,
1
,
2
3
.
1
,
2
3
1237 and 1240 cm-1, respectively, which are shifted to a lower frequencies,
implying that the M-O bonds are formed between the metal ions and oxygen
atoms of phenolic groups [62]. The above facts are in agreement with the results
determined by X-ray diffraction.
Table 2 The IR data for the free ligand H4L, Zn(II) complex and heterotrinuclear complexes
1, 2 and 3
Compound
H4L
ν(C=N)
1607
1604
1610
1610
1610
ν(Ar-O)
1250
1244
1242
1237
1240
ν(O-H)
3172
3387
-
Zn(II) complex
Complex 1
Complex 2
Complex 3
-
3419

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3.2. UV-Vis absorption spectra
It can be seen from the spectrum of the free ligand H4L, there are four
absorption peaks at ca. 269, 342, 360 and 378 nm (Fig. 1). The absorption peak at
269 nm can be assigned to the π-π* transition of the benzene rings. The other
three absorption peaks can be attributed to the π-π* transition of the oxime groups
[14-17]. The Zn(II) complex shows four absorption bands at 280, 370, 396 and
416 nm which can be observed in the heterotrinuclear complexes 1, 2 and 3 with
absorbance intensity changes. Compared with the absorption peaks of the free
ligand H4L, the corresponding absorption peaks of complexes 1, 2 and 3 are
bathochromically shifted by ca. 11, 28, 36 and 38 nm, respectively, indicating the
coordination of metal ions with the (L)4– unit.
Fig. 1 UV–Vis spectrum of the free ligand in CHCl3/CH3OH (1:1) ( 3.0 × 10-5 M)
In the UV-Vis titration experiments of complex 1, the colour of the solution of Zn(II)
complex in chloroform/methanol (1:1) changed inconspicuously when the solution of
La3+ was added. With the increasing concentration of La3+, the absorbance of the
solution from 320~407 nm enhanced, and from 407~500 nm reduced. The
absorbance of the solution hardly changed after La3+ was added up to 1 equiv. The

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spectroscopic titration clearly indicated that the ratio of the replacement reaction was
1:1 (Fig. 2). Similar changes also appeared in complexes 2 and 3, which gave the same
conclusions.

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Fig. 2 UV–Vis spectral changes of complexes by the addition of Ln(NO3)3 (CHCl3/CH3OH (1:1),
[complex 1] = 3.3 × 10-5 M): (a) Ln3+ = La3+, (b) Ln3+ = Ce3+, (c) Ln3+ = Dy3+
3.3. Fluorescence spectra
As can be seen from the spectra of the free ligand H4L and its corresponding
complexes 1, 2 and 3 (Fig. 3), the absorption peaks are bathochromically-shifted from
that of the ligand H4L at 397 nm, which is due to the intraligand π–π* transition [63-65].
It is obvious that the La(III) enhanced of the fluorescence intensity and Ce(III)
fluorescence quenching.
Fig. 3 Emission spectra of the free ligand H4L and complexes 1, 2 and 3 in CHCl3/CH3OH (1:1)

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The excitation spectra using chloroform and methanol as the solvent are
detected at the peak wavelength of the corresponding emission spectra at room
temperature. The emission spectrum of complex
temperature is shown in Fig. 4. The emission spectrum of complex
nm wavelength excitation exhibits broad visible photoluminescence at the range
of 450 to 600 nm. Furthermore, the fluorescence intensity of complex is much
1
in this solvent at room
1
from 431
1
stronger than the reported heterotrinuclear complexes with alkaline earth ions.
Two reasons lead to the enhancement of the fluorescence intensity, on one hand, the
naphthalene ring have larger conjugate system which is good for optical
properties, on the other hand, La(III) ion is usually used to synthesizing
luminescent complexes.
Fig. 4 (a) The excitation and emission spectra of complex 1. (b) Fluorescence spectral changes of
Zn(II) complex by the addition of La(NO3)3 (CHCl3/CH3OH (1:1), [Zn(II) complex] = 5.0 × 10-5
=M).
The emission spectrum of complex
2 in the same solvent at room temperature
is shown in Fig. 5. Complex shows fluorescence quenching with maximum
2
emission at ca. 502 nm upon excitation at 437 nm, which may result from Ce3+
ion itself and the fluorescence of Ce3+ ion is rarely reported in the literature. Both
the absorbance of the solutions hardly changed after La3+ or Ce3+ was added up to
1 equiv. The spectroscopic titration clearly indicated that the ratio of the
replacement reaction was 1:1, which obtained the same conclusion with UV-Vis

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titration.
Fig. 5 (a) The excitation and emission spectra of complex 2. (b) Fluorescence spectral changes of
Zn(II) complex by the addition of Ce(NO3)3 (CHCl3/CH3OH (1:1), [Zn(II) complex] = 5.0 × 10-5 M).
Complex
the emission spectra are shown in Fig. 6. Here, fluorescence enhancement of
complex is observed with obvious blue shift, which is just stronger than the
Zn(II) complex but far from complex . The emission spectrum of complex
3 having maximum emission at ca. 481 nm upon excitation at 420 nm,
3
1
3
from 420 nm wavelength excitation exhibits broad visible photoluminescence at
the range of 425 to 600 nm. Additionally, no characteristic emission peaks of
Dy3+ ion are existed in the spectrum, which may result from the ligand H4L
cannot be an antenna group to sensitize Dy3+ ion through an efficient
intramolecular energy transfer process [66].
Fluorescence titration experiments of the lanthanide ions with the crystal of
Zn(II) complex dissolved in the solvent show the same conclusion compared with
the UV-Vis titration experiments. The fluorescence intensity of the solution
hardly changed after lanthanide ion was added up to 1 equiv. With fluorescence
enhancement and quenching, the spectroscopic titration of complexes
clearly indicated that the ratio of the replacement reaction was 1:1.
1 and 2

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Fig. 6 (a) The excitation and emission spectra of complex 2. (b) Fluorescence spectral changes of
Zn(II) complex by the addition of Dy(NO3)3 (CHCl3/CH3OH (1:1), [Zn(II) complex] = 5.0 × 10-5
M).
The difference of heterotrinuclear complexes 1, 2 and 3 is great. It indicates that
the preparation of 3d-4f complexes by substitution reaction is effective. Through
the spectral titration, high transformation rate and high yield could be predicted.
3.4. Crystal structure descriptions
The heterotrinuclear complexes 1, 2 and 3 were synthesized by using La3+, Ce3+ and
Dy3+ ions to replace the central Zn2+ ion of homotrinuclear complex,
[Zn3(L)(OAc)2(CH3OH)2]∙3CHCl3, respectively. All the structures of complexes 1, 2
and 3 were determined by single-crystal X-ray diffraction. Selected bond lengths and
bond angles are listed in Table 3.
Table 3 Selected bond lengths (Å) and angles (o) of complexes
1, 2 and 3
Complex 1
La1-O1
2.828(2)
2.591(2)
2.615(3)
56.73(7)
124.56(7)
67.49(7)
125.90(7)
La1-O2
2.595(2)
2.886(2)
2.600(2)
99.91(7)
64.77(7)
59.18(7)
103.60(7)
La1-O5
2.591(2)
2.476(2)
La1-O6
2.578(2)
2.465(2)
La1-O9
La1-O10
La1-O11
La1-O13
La1-O15
La1-O16
O1-La1-O2
O1-La1-O10
O1-La1-O16
O2-La1-O10
O1-La1-O5
O1-La1-O11
O2-La1-O5
O2-La1-O11
O1-La1-O6
O1-La1-O13
O2-La1-O6
O2-La1-O13
128.70(7)
127.16(8)
117.31(7)
76.12(7)
O1-La1-O9
O1-La1-O15
O2-La1-O9
O2-La1-O15
123.54(7)
64.83(7)
177.18(7)
109.67(8)

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O2-La1-O16
O5-La1-O11
O6-La1-O9
O6-La1-O15
O9-La1-O13
O10-La1-O13
O11-La1-O15
O15-La1-O16
Complex 2
Ce1-O1
73.14(7)
90.45(8)
60.12(7)
128.96(8)
104.76(8)
64.70(7)
81.88(8)
49.86(8)
O5-La1-O6
58.75(7)
70.94(7)
100.34(7)
163.41(7)
72.36(7)
64.37(7)
122.85(8)
O5-La1-O9
118.43(7)
164.69(7)
69.14(8)
56.61(7)
109.64(7)
63.58(7)
118.59(8)
O5-La1-O10
O5-La1-O16
O6-La1-O13
O9-La1-O11
O10-La1-O11
O11-La1-O13
O13-La1-O16
130.10(7)
127.48(7)
91.83(8)
74.58(7)
126.36(7)
158.73(8)
77.82(8)
O5-La1-O13
O6-La1-O10
O6-La1-O16
O9-La1-O15
O10-La1-O15
O11-La1-O16
O5-La1-O15
O6-La1-O11
O9-La1-O10
O9-La1-O16
O10-La1-O16
O13-La1-O15
2.688(7)
2.485(7)
2.471(7)
60.6(2)
69.5(2)
74.0(2)
129.7(2)
110.1(2)
71.4(2)
102.2(2)
83.9(2)
Ce1-O2
2.458(7)
2.747(6)
Ce1-O5
2.437(6)
2.459(7)
Ce1-O6
2.481(7)
2.499(7)
Ce1-O9
Ce1-O10
Ce1-O11
Ce1-O13
Ce1-O15
O1-Ce1-O2
O1-Ce1-O10
O2-Ce1-O5
O2-Ce1-O11
O5-Ce1-O9
O5-Ce1-O15
O6-Ce1-O13
O9-Ce1-O13
O1-Ce1-O5
O1-Ce1-O11
O2-Ce1-O6
O2-Ce1-O13
O5-Ce1-O10
O6-Ce1-O9
O6-Ce1-O15
O9-Ce1-O15
130.5(2)
73.6(2)
134.8(2)
69.5(2)
139.3(2)
62.7(2)
83.3(2)
136.4(2)
O1-Ce1-O6
O1-Ce1-O13
O2-Ce1-O9
O2-Ce1-O15
O5-Ce1-O11
O6-Ce1-O10
O9-Ce1-O10
149.7(2)
108.1(2)
150.2(2)
73.4(2)
O1-Ce1-O9
O1-Ce1-O15
O2-Ce1-O10
O5-Ce1-O6
O5-Ce1-O13
O6-Ce1-O11
O9-Ce1-O11
119.0(2)
77.5(2)
97.7(2)
61.9(2)
70.1(2)
79.6(2)
70.4(2)
132.4(2)
121.8(2)
59.2(2)
O10-Ce1-O11 83.9(2)
O11-Ce1-O15 77.7(2)
O10-Ce1-O13 69.7(2)
O13-Ce1-O15 132.1(2)
O10-Ce1-O15 145.6(2)
O11-Ce1-O13 150.2(2)
Complex 3
Dy1-O1
2.595(3)
Dy1-O2
2.318(4)
2.643(3)
Dy1-O5
2.335(4)
2.407(4)
Dy1-O6
2.355(3)
2.375(4)
Dy1-O9
2.367(4)
Dy1-O10
Dy1-O11
Dy1-O13
Dy1-O17
2.472(4)
O1-Dy1-O5
O1-Dy1-O11
O2-Dy1-O6
O2-Dy1-O13
128.78(12)
117.53(13)
137.92(11)
125.99(13)
O1-Dy1-O6
O1-Dy1-O13
O2-Dy1-O9
O2-Dy1-O17
144.45(12)
69.18(13)
149.24(12)
73.98(14)
O1-Dy1-O9
O1-Dy1-O17
O2-Dy1-O10
O5-Dy1-O6
112.19(12)
72.87(14)
91.04(13)
65.34(10)
O1-Dy1-O10
O2-Dy1-O5
O2-Dy1-O11
O5-Dy1-O9
65.47(12)
73.24(12)
75.74(13)
119.03(12)

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O5-Dy1-O10
O6-Dy1-O9
O6-Dy1-O17
O9-Dy1-O17
142.53(11)
65.14(10)
85.56(12)
135.68(12)
O5-Dy1-O11
O6-Dy1-O10
O9-Dy1-O10
71.97(12)
126.71(11)
61.74(11)
O5-Dy1-O13
O6-Dy1-O11
O9-Dy1-O11
126.50(12)
97.56(12)
81.63(12)
O5-Dy1-O17
O6-Dy1-O13
O9-Dy1-O13
70.88(12)
77.01(11)
71.78(12)
O10-Dy1-O11 71.24(12)
O11-Dy1-O17 137.26(13)
O10-Dy1-O13 90.40(12)
O13-Dy1-O17 69.60(13)
O10-Dy1-O17 138.01(13)
O11-Dy1-O13 152.72(13)
3.4.1. Crystal structure of complex 1
The crystal structure of complex 1 and the coordination environment of La1 and Zn2
are shown in Fig. 7. Complex 1 crystallizes in the triclinic space group P1. X-ray
crystallography clearly showed the formation of complex 1, which was isolated as
yellow crystals. Interestingly, the formation process of complex 1 was highly
cooperative. In the crystal structure of complex 1, two acetate ions bridge Zn2+ and La3+
ions in a µ2-fashion. Meanwhile, two oxygen ions of another acetate ion coordinate to
La3+ synchronously, which probably contribute to the cooperative formation of complex
1. Zn1 and Zn2 are both penta-coordinated with geometries of distorted tetragonal
pyramid, which were deduced by calculating the value of τ1 = 0.3175, τ2 = 0.3778,
respectively [67]. La1 is located in the cavity that consists of six oxygen atoms, the four
are phenoxy oxygen atoms while the two others come from methoxy groups. Besides,
three acetate ions provide remaining four oxygen atoms, so La1 is ten-coordinated with
geometry of distorted bicapped square antiprism. The distances between La1 and the
coordination oxygen atoms are ranged from 2.578(2) to 2.886(2) Å. Such structure is
similar to the reported work earlier, in which La3+ is also ten-coordinated and no solvent
molecules coordinate to the metal ions [68]. The high coordination number of La3+ ion
is determined byits longer ionic radius and smaller winding angles.

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Fig. 7 X-ray crystal structure of complex 1 and the coordination environment of La1 and Zn2
Fig. 8 View of an infinite 1D chain motif of complex 1 units along the c axis.
In the crystal structure of complex 1, there are significant intermolecular hydrogen
bonds
(C7-H7∙∙∙O16)
and
C-H∙∙∙π
interactions
(C21-H21∙∙∙Cg6
(C11-C12-C17-C18-C19-C20), C14-H14∙∙∙Cg8 (C25-C30)), which link the units
together efficiently, especially, the units are interlinked by the intermolecular hydrogen
bonds into a 1D chain supra-molecular structure along the c axis (Fig. 8).
3.4.2. Crystal structure of complex
The crystal structure of complex
are shown in Fig. 9. Complex also crystallizes in the triclinic space group
2
2
and the coordination environment of Ce1
P1.
2

Ce1 is also located in the O6 cavity, differently, three acetate ions all bridge Zn2+
and Ce3+ ions in a µ2-fashion, which provide other three oxygen atoms. As the
three coordinated acetate ions, Zn1 is hexa-coordinated with geometry of

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distorted octahedron. Zn2 is peta-coordinated with geometry of distorted
tetragonal pyramid. Ce1 is nine-coordinated with geometry of distorted capped
square antiprism. The distances between Ce1 and the four phenoxy oxygen atoms
of the salamo moieties coordinate are ranged from 2.437(6) to 2.485(7) Å,
however, the distances of the oxygen atoms of acetates ions are all in this range.
The distances with methoxy groups (Ce1-O1 2.688(7) Å, Ce1-O10 2.747(6) Å)
are clearly longer than those of above oxygen atoms. Negative charge of the
oxygen atoms would be the main reason, which enhances the coordination ability
of the oxygen atoms.
Fig. 9 X-ray crystal structure of complex 2 and the coordination environment of Ce1 and Zn ions
Fig. 10 View of a dipolymer motif of two complex 2 units.

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In the crystal structure of complex 2, just three intermolecular hydrogen bonds
(C8-H8B∙∙∙O14, C22-H22A∙∙∙O12, C24-H24∙∙∙O13) were observed. Here, complex 2
units are interlinked by one pair intermolecular hydrogen bonds into a dipolymer (Fig.
10). No supramolecular structures were observed in complex 2.
3.4.3. Crystal structure of complex
The crystal structure and atom numbering of complex
Complex crystallizes in the monoclinic space group P21/c which is different
from the former complexes. The Zn2+ ions of complex
have similar
coordination environments and coordination geometries with complex . Zn1 is
3
3
is shown in Fig. 11.
3

3
2
hexa-coordinated with geometry of distorted octahedron, and Zn2 is
peta-coordinated with geometry of distorted tetragonal pyramid. Unexpectedly,
the third acetate ion only coordinates with Zn1 as a monodentate ligand, and
another methanol molecule coordinates to Dy3+ ion instead of it. So Dy1 is
nine-coordinated consisting of six oxygen atoms from bis(salamo)-type ligand,
two oxygen atoms of two acetate ions and one oxygen atom of coordinated methanol
molecule, with geometry of distorted capped square antiprism. The same
phenomena were observed that the coordination bonds of Dy1 with negative charged
oxygen atoms have shorter distances.
In the crystal structure of complex 3, there are significant intermolecular hydrogen
bonds (C24-H24···O11, C15-H15···O16) and C-H∙∙∙π interactions (C8-H8A∙∙∙ Cg8
(C25-C30)), which link the units together efficiently, especially, complex 3 units are
interlinked by the intermolecular hydrogen bond and C-H∙∙∙π interactions into a 2D
supra-molecular structure along the ab plane (Fig. 12).

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Fig. 11 X-ray crystal structure of complex 3 and the coordination environment of Dy1.
Fig. 12 View of an infinite 2D supra-molecular network of complex 3 units on the ab plane.
As we see, the three lanthanide complexes have their own structure characteristics.
The three acetate ions coordinate to the metal ions result in two main effects, the one is
to make crystal structure stable, the other is to make the charge balance. With the
coordinated methanol molecules, complex 3 having similar structure with complex 2
owns more intermolecular interactions.
4. Conclusions
We had designed and synthesized a novel naphthalenediol-based acyclic

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bis(salamo)-type ligand and its corresponding homotrinuclear Zn(II) complex.
Here, the heterotrinuclear 3d-4f complexes were acquired by the substitution
reaction of the homotrinuclear Zn(II) complex with 1 equiv of Ln(NO3)3 (Ln3+ =
La3+, Ce3+ and Dy3+). Spectral titrations and X-ray crystallography clearly show
that the stoichiometry of the homotrinuclear Zn(II) complex is 1:3 (ligand/Zn2+)
and those of the heterotrinuclear complexes are all 1:2:1 (ligand/Zn2+/Ln3+),
respectively. The different optical properties and peak wavelength variation of the
heterotrinuclear complex clearly show the success of transformation from
homotrinuclear to heteronuclear complexes, which could be used in host–guest
systems. Furthermore, by analyzing the structures of these complexes, another
acetate ion coordinate to the metal ions compared with the alkaline earth ion that
we had reported, which makes the crystal structure more stable.
Acknowledgments
This work was supported by the National Natural Science Foundation of China
(21361015), which is gratefully acknowledged.

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Abstract: Heterotrinuclear 3d-4f metal complexes with an naphthalenediol-based acyclic
bis(salamo)-type ligand have been synthesized and structurally characterized. The
coordination modes of three acetate ions are different in the complexes
clearly shows that the heterotrinuclear complexes [Zn2(L)La(OAc)3] (
1
-
3
. Spectral titration
1
), [Zn2(L)Ce(OAc)3]
(2) and [Zn2(L)Dy(OAc)3(CH3OH)]·CH2Cl2 (3) were acquired by the substitution reaction of
the reported homotrinuclear Zn(II) complex with 1 equiv of Ln(NO3)3 (Ln3+ = La3+, Ce3+ and
Dy3+).

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Highlights
Novel naphthalenediol-based acyclic bis(salamo)-type ligand was synthesized.
Spectral titrations clearly show the success of transformation from homotrinuclear to
heterotrinuclear complexes.
The 3d-4f complexes have been synthesized and characterized structurally.
The different coordination modes of acetate ions in complexes 1, 2 and 3 have been
observed.
Fluorescence properties of complexes 1, 2 and 3 have been discussed.