Synthesis, structure and luminescence properties of lanthanide complex with a new tetrapodal ligand featuring salicylamide arms

Article abstract of DOI:10.1016/j.jssc.2009.07.062

A new tetrapodal ligand 1,1,1-tetrakis{[(2′-(2-furfurylaminoformyl))phenoxyl]methyl}methane (L) has been prepared and their coordination chemistry with Ln^III ions has been investigated. The structure of {[Ln₄L₃(NO₃)₁₂]·H₂O}_∞ (Ln=Nd, Eu)] shows the binodal 4,3-connected three-dimensional interpenetration coordination polymers with topology of a (8⁶)₃(8³)₄ notation. [DyL(NO₃)₃(H₂O)₂]·0.5CH₃OH and [ErL(NO₃)₃(H₂O) (CH₃OH)]·CH₃COCH₃ is a 1:1 mononuclear complex with interesting supramolecular features. The structure of [NdL(H₂O)₆]·3ClO₄·3H₂O is a 2:1 mononuclear complex which further self-assembled through hydrogen bond to form a three-dimensional supramolecular structures. The result presented here indicates that both subtle variation of the terminal group and counter anions can be applied in the modulation of the overall molecular structures of lanthanide complex of salicylamide derivatives due to the structure specialties of this type of ligand. The luminescence properties of the Eu^III complex are also studied in detail.

Full text of DOI:10.1016/j.jssc.2009.07.062

ARTICLE IN PRESS
Journal of Solid State Chemistry 183 (2010) 1–9
Contents lists available at ScienceDirect
Journal of Solid State Chemistry
journal homepage: www.elsevier.com/locate/jssc
Synthesis, structure and luminescence properties of lanthanide complex with
a new tetrapodal ligand featuring salicylamide arms
Ã
Xue-Qin Song a,b, Xiao-Guang Wen b, Wei-Sheng Liu a, , Da-Qi Wang c
a College of Chemistry and Chemical Engineering and State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, China
b School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China
c Department of Chemistry, Liaocheng University, Liaocheng 252000, China
a r t i c l e i n f o
a b s t r a c t
A new tetrapodal ligand 1,1,1-tetrakis{[(20-(2-furfurylaminoformyl))phenoxyl]methyl}methane (L) has
been prepared and their coordination chemistry with LnIII ions has been investigated. The structure of
{[Ln4L3(NO3)12] ꢀ H2O}N (Ln=Nd, Eu)] shows the binodal 4,3-connected three-dimensional interpene-
tration coordination polymers with topology of a (86)3(83)4 notation. [DyL(NO3)3(H2O)2] ꢀ 0.5CH3OH and
[ErL(NO3)3(H2O) (CH3OH)] ꢀ CH3COCH3 is a 1:1 mononuclear complex with interesting supramolecular
features. The structure of [NdL(H2O)6] ꢀ 3ClO4 ꢀ 3H2O is a 2:1 mononuclear complex which further self-
assembled through hydrogen bond to form a three-dimensional supramolecular structures. The result
presented here indicates that both subtle variation of the terminal group and counter anions can be
applied in the modulation of the overall molecular structures of lanthanide complex of salicylamide
derivatives due to the structure specialties of this type of ligand. The luminescence properties of the EuIII
complex are also studied in detail.
Article history:
Received 29 March 2009
Received in revised form
1 July 2009
Accepted 12 July 2009
Available online 31 August 2009
Keywords:
Lanthanide coordination polymer
Salicylamide
Crystal structure
Hydrogen-bond
Luminescence properties
& 2009 Elsevier Inc. All rights reserved.
1. Introduction
some lanthanide complexes with intriguing structure as well as
interesting luminescence properties have been reported [11]. In
order to further understand the influence on the structure as well
as the regularity of luminescence properties of their complexes, it
is necessary to extend such a studying area for improving
desirable properties. At the same time, we have tried to merge
the role of anions in this self-assembly. As a part of our systematic
investigation of self-assembly based on salicylamide ligands, we
report herein the synthesis of a new tetrapodal ligand featuring
salicylamide arms, namely, 1,1,1,1-tetrakis{[(20-(2-furfurylamino-
formyl))phenoxyl]methyl}methane (L) and describe the synthesis
and crystal structure of the resulting complexes. Two three-
dimensional polymeric coordination complexes, namely,
[Nd4L3(NO3)12 ꢀ 6H2O]N, {[Eu4L3(NO3)12] ꢀ 6H2O}N, three mono-
nuclear complex with interesting supramolecular properties,
The design and construction of polymeric metal-organic hybrid
complexes are of considerable interest in recent years, due to their
appealing structural topologies and potential application in
catalysis, adsorption/separation, host-guest chemistry, and the
promising photo-, electro-, and magnetofunctional materials [1–
3]. Metal-organic frameworks containing lanthanide ions as
connectors is particularly attractive because of the magnetic and
electronic properties of 4f ions, which should result in the
application of lanthanide polymers in sensors, lighting devices,
and optical storage [4]. Lanthanide ions, with their high
coordination flexibility and their lack of preferential geometries,
are good candidates to provide unique opportunities for the
discovery of unusual network topologies [5–7], thus leading us to
this interesting and challenging field. So far, much work is focused
on using multicarboxylate ligands to prepare lanthanide-contain-
ing MOFs [8,9]. By contrast, based on a query to the Cambridge
Structural Database (CSD), we find that the synthesis of multi-
dimensional lanthanide-containing MOFs by using amide ligands
is less developed [10].
namely,
{[DyL(NO3)3(H2O)2] ꢀ 0.5CH3OH},
{[ErL(NO3)3(H2O)(-
CH3OH)] ꢀ CH3COCH3} and {[NdL2(H2O)6] ꢀ 3ClO4 ꢀ 3H2O}, were
structurally characterized by single-crystal X-ray diffraction
together with the luminescence properties of the EuIII complex.
Owing to the structural features of salicylamide derivatives
which afforded diverse types of lanthanide supramolecular
complexes upon variation of the backbone and terminal groups,
2. Experimental
2.1. Materials
The commercially available chemicals were used without
further purification. All of the solvents used were of analytical
reagent grade.
Ã
Corresponding author. Fax: +86 9318912582.
E-mail address: liuws@lzu.edu.cn (W.-S. Liu).
0022-4596/$ - see front matter & 2009 Elsevier Inc. All rights reserved.
doi:10.1016/j.jssc.2009.07.062

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2.2. Methods
displacement parameters of hydrogen were derived from their
parent atoms. The hydrogen atoms of the water molecules were
located by a difference Fourier map and refined with distance
The metal ions were determined by EDTA titration using
xylenol orange as indicator. C, N and H were determined using an
Elementar Vario EL. Melting points were determined on a Kofler
apparatus. IR spectra were recorded on Nicolet FT-170SX instru-
ment with pressed KBr pellets in the 400–4000 cmꢁ1 region. 1H
NMR spectra were measured on a Brucker DRX 300 spectrometer
in CDCl3 solution with TMS as internal standard. Fluorescence
measurements were made on FLS920 of Edinburgh Instrument
equipped with quartz curettes of 1 cm path length with a xenon
lamp as the excitation source. An excitation and emission slit of
2.5 nm were used for the measurements of luminescence in solid
state. The 77 K solution-state phosphorescence spectra were
recorded with solution samples loaded in a quartz tube inside a
quartz-walled optical Dewar flask filled with liquid nitrogen in the
phosphorescence mode. Quantum yields were determined by an
absolute method using an integrating sphere on FLS920 of
Edinburgh Instrument. The luminescence decays were recorded
using a pumped dye laser (Lambda Physics model FL2002) as the
excitation source. The nominal pulse width and the linewidth of
the dye laser output were 10 ns and 0.18 cmꢁ1, respectively. The
˚
restrains for O–H and H?H (0.90 and 1.50 A, respectively), and
one variable isotropic U for NdIII perchlorate complex. In the
structure of NdIII complex, the terminal furfurylamine group
exhibits disorder over two positions and the occupancy ratios
were found to 0.529/0.471. In all cases of refinements, structural
restraints were applied for solvent molecules, benzene or furan
rings of the ligand, the full details of which are given in the ESI CIF
files. Details of crystallographic parameters, data collection and
refinements are listed in Table 2. Representive bond distances and
angles for NdIII, EuIII, DyIII, ErIII nitrate and NdIII perchlorate
complexes are listed in Table S1, S2 and S3, respectively. Crystal-
lographic data for the structures reported in this paper have been
deposited with the Cambridge Crystallographic Data Centre as
CCDC 705664–705668.
2.4. Synthesis of the ligand
The ligand 1,1,1,1-tetrakis{[(20-(2-furfurylaminoformyl))phe-
noxyl]methyl}methane (L) (Scheme 1) was prepared similar to
the literature procedure [11f]. Yield 76%. m.p.: 161.7 1C. Analytical
data, Calc. for C53H48N4O12: C, 68.23; H, 5.19; N, 6.01; Found: C,
68.52, H, 5.21, N, 6.04; IR (KBr, u, cmꢁ1): 3417, 3314 (m, NH), 1648
(s, CQO), 1601 (m), 1537 (m), 1299 (m), 1224 (m), 750 (m). 1H
emission of
a sample was collected by two lenses into a
monochromator (WDG30), detected by a photomultiplier and
processed by a Boxcar Average (EGG model 162) in line with a
microcomputer. Reported luminescence lifetimes are averages of
at least three independent determinations.
NMR (CDCl3, 300 MHz): d: 4.16 (s, 8H, OCH2), 4.48 (d, J=5.4, 8H,
NHCH2), 6.11 (m, 8H, Ar), 6.82 (d, J=8.1, 4H, Ar), 6.98 (s, 4H, Ar),
2.3. Crystal structure determination
7.13 (t, 4H, Ar), 7.20 (t, 4H, NH), 7.44 (m, 4H), 8.0 (dd, 4H, Ar).
X-ray single-crystal diffraction of all complexes was performed
˚
on CCD area diffractometer with MoKa radiation (l=0.71073 A) at
2.5. Syntheses of the complexes
298 K. In each case, semiempirical absorption correction was
applied (SADABS) and the program SAINT was used for integration
of the diffraction profiles [12]. The structures were solved by
direct methods using SHELXS of the SHELXL package and refined
with SHELXL [13]. The non-H atoms were modeled with
anisotropic displacement parameters and refined by full-matrix
least-squares methods on F2. Generally, C-bound hydrogen atoms
were placed geometrically and refined as riding. Isotropic
One millimole of ligand and 1 equiv (1 mmol) of the lanthanide
nitrates or perchlorates were dissolved in a minimum methano-
l+acetone+ethyl acetate (v:v=1:1:8) solution under reflux. Then
the flask was cooled, and the mixture was filtered into a sealed
25–40 ml glass vial for crystallization at room temperature. After
about three weeks crystals suitable for analysis were obtained.
Elemental analysis data and IR spectra data characteristic of the
complexes are listed in Table 1.
3. Results and discussion
The tetrapodal ligand was prepared by the ether base coupling
of pentaerythritol benzenesulfonate and the furfurylsalicylamide
in a 1:4 ratio in dry DMF in the presence of an excess of anhydrate
K2CO3 (Scheme 1). Purification of L was accomplished by column
chromatography over silica, eluting with petroleum ether/ethyl
acetate (v:v=2:1) to give a pale white solid with the yield of 76%.
Scheme 1. The synthetic route of the ligand.
Table 1
Elemental analytical and IR spectral data for the complexes.
Compound
Elemental analysesa
C
IR (l )
max/cmꢁ1
H
N
Ln
u (CQO)
Nd4L3(NO3)12(H2O)6
45.38 (45.17)
44.69 (44.84)
48.38 (48.19)
49.29 (49.10)
51.41 (51.53)
3.70 (3.72)
3.68 (3.69)
4.10 (4.08)
4.37 (4.34)
4.67 (4.65)
7.93 (7.95)
7.90 (7.89)
7.37 (7.35)
7.05 (7.03)
4.52 (4.54)
13.59 (13.65)
14.34 (14.27)
12.12 (12.19)
11.96 (12.00)
5.81 (5.84)
1607
1606
1607
1604
1605
Eu4L3(NO3)12(H2O)6
DyL(NO3)3(H2O)2(CH3OH)0.5
ErL(NO3)3(CH3OH)(H2O)(C3H6O)
NdL2(H2O)9(ClO4)3
1644
1632
1638
a
Data in parentheses are calculated values.

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3
3.1. Physical measurements
site with ꢁ4 crystallographic symmetry and the water oxygen
atom O7 lies on a twofold axis. Since the asymmetric building
block having C3 symmetry has a tripod-type shape, and the
adjacent blocks are linked by the coordination bonds of the
tetrahedrally arrayed salicylamide arms of the ligand, a three-
dimensional interpenetration coordination polymer formed. There
is one crystallographically independent Nd atom, three fourths L
ligand and three coordinated bidentate nitrate ions in each
asymmetric unit as shown in Fig. 1. The three carbonyl groups
from three different L ligands bridge a NdIII ion, each NdIII ion is
thus coordinated to three carbonyl and three nitrate ions in a
distorted [NdO9] monocapped square antiprismatic coordination
geometry, of which the coordination sphere for NdIII is defined by
The new ligand gave satisfactory 1H NMR, IR spectra and
elemental analyses. Treatment of Ln(NO3)3 ꢀ 6H2O with the ligand
in ethyl acetate- acetone-methanol solution yields a series of
complexes which, according to combustion analysis (Table 1),
correspond to the formula of Ln4L3(NO3)12 (H2O)6 (Ln=Nd and Eu),
DyL(NO3)3(H2O)2(CH3OH)0.5
, ErL(NO3)3(H2O)(CH3OH)(CH3OCH3)
and NdL2(H2O)9(ClO4)3, respectively. X-ray quality crystals of the
complexes were obtained after several weeks from vapor diffusion
from ethyl acetate/acetone/methanol solution. The complexes are
soluble in DMF, DMSO, methanol and ethanol, slightly soluble in
ethyl acetate, acetonitrile and acetone, but insoluble in CHCl3
and ether.
˚
three carbonyl oxygen (Nd–O=2.397(7) A) from three different
The characteristic band of carbonyl group of free ligand L is
shown at 1648 cmꢁ1. The absence of the band round 1648 cmꢁ1
which is instead of a new band at ca. 1606 cmꢁ1 in the NdIII and
EuIII nitrate complex compared to the free ligand indicates the
complete coordination of the ligand. However, the IR spectrum of
DyIII and ErIII nitrate complex as well as ErIII perchlorate complex
confirmed the presence of both the uncoordinated and coordi-
nated carbonyl group with a peak at ca. 1640 and 1606 cm–1. Weak
absorptions observed in the range of 2900–2950 cmꢁ1 can be
attributed to the uCH2 of the ligand. The strong broad bands at ca.
3402 cmꢁ1 are ascribed to the vibration of the water ligands in the
complexes.
3.2. Crystal structure descriptions
Structure I. Prismatic crystals of NdIII and EuIII complex were
obtained by reaction of Ln(NO3)3 ꢀ 6H2O and L in a 1:1 mol ratio in
methanol–acetone–ethyl acetate solution. They are air stable and
have a similar thermal decomposition behavior, which is reason-
able since they possess the same polymeric motif. Single-crystal
X-ray analyses reveal that NdIII and EuIII complex are isomorphous
(Table 2), therefore, details will only be provided for the Nd
analogue. The NdIII complex of the ligand crystallizes in the cubic
space group I-43d, which allows a 3-fold rotational axis passes
through the NdIII ion and thus to give a C3 molecular symmetry. It
is also important to note that the C1 atom of the ligand lies at a
Fig. 1. ORTEP plot of NdIII nitrate complex showing the local coordination
environment of NdIII with thermal ellipsoids at 30% probability (Hydrogen
molecules are omitted for clarity).
Table 2
Crystal data and structure refinement parameters for the complexes.
Compound
1
2
3
4
5
Empirical formula
Mr
C
53H52N8Nd1.33O26
C53H52Eu1.33N8O26
1419.64
C53.50H54DyN7O23.50
1333.54
C57H60ErN7O24
1394.38
C106H114Cl3N8NdO45
2486.64
1409.35
Cubic
Crystal system
Space group
Cubic
Monoclinic
P2(1)/n
Monoclinic
P2(1)/n
Triclinic
Iꢁ43d
Iꢁ43d
Pꢁ1
27.479(2)
27.520(3)
15.415(2)
16.156(4)
13.998(8)
˚
a (A)
27.479(2)
27.479(2)
27.520(3)
27.520(3)
21.437(3)
17.506(3)
20.630(5)
18.210(4)
18.871(10)
25.494(14)
˚
b (A)
˚
c (A)
a
b
g
(1)
(1)
(1)
90
90
90
90
90.609(8)
99.710(9)
102.620(8)
6469(6)
90
90
95.776(2)
90
91.847(4)
90
90
90
3
20 750(3)
20 841(4)
5755.4(14)
6066(2)
˚
V (A )
Z
12
12
4
4
2
Dc (kg mꢁ3
)
1.353
1.357
1.539
1.527
1.277
m
(mmꢁ1
)
1.074
1.277
1.387
1.471
0.545
F (000)
8568
8616
2712
2844
2570
Crystal size (mm)
0.38 ꢂ 0.32 ꢂ 0.21
3041/119/200
1.023
0.44 ꢂ 0.42 ꢂ 0.39
2929/202/189
1.053
0.54 ꢂ 0.43 ꢂ 0.40
10 149/513/827
1.000
0.29 ꢂ 0.21 ꢂ 0.18
10 651/288/805
1.085
0.43 ꢂ 0.40 ꢂ 0.27
22 273/624/1481
1.054
Data/restraints/params
Goodness-of-fit on F2
Final R indices[I42
s(I)]
R1=0.0697
wR2=0.1707
R1=0.1197
wR2=0.2062
R1=0.0860
wR2=0.2102
R1=0.1684
wR2=0.2840
R1=0.0485
wR2=0.1374
R1=0.0825
wR2=0.1743
R1=0.0403
wR2=0.0806
R1=0.0894
wR2=0.1094
R1=0.0983
wR2=0.2090
R1=0.2462
wR2=0.2624
R indices (all data)

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˚
ligand L, six nitrate oxygen atom (Nd–O=2.519(9) and 2.543(8) A)
(Table S1, ESI). Each ligand was bonded to four nona-coordinated
NdIII ions, via complexation by carbonyl oxygen donors on
salicylamide arms. The NdIII ions in turn coordinated to three
salicylamide arms of three other adjacent ligands, meaning that
each ligand was linked by Nd coordination to four adjacent
ligands. The above three-dimensional structure can also be
explained by considering smaller building units. Thus, the Nd
polyhedron units are connected through ligand L in three-
the conformational freedom is apparently somewhat limited due
to the steric bulk and rigidity associated with the salicylamide
group.
Structure II. Even though the radius of DyIII is only 0.04 A
˚
smaller than that of EuIII, the introduction of DyIII during the
synthesis results a quite different product. The ligand coordinates
to a single metal centre in a monodentate mode, in contrast to
the tetradentate bridging coordination mode observed from the
NdIII to EuIII complex possibly for the cooperative effect of the
bulkier ligand, the intermolecular hydrogen bond and the smaller
ionic radius which is not favorable for the ligand to replace the
coordinated water molecules in this case. X-ray structural
analyses revealed that the DyIII and ErIII nitrate complex of ligand
L formed isomorphous crystal structures (Table 2). The only minor
differences are that one of the coordinated water molecule in the
DyIII complex is replaced by a coordinated methanol molecule in
ErIII complex; the methanol solvate molecule in the DyIII complex
is replaced by an acetone molecule in the ErIII complex. These two
complexes crystallized in the monoclinic space group P21/n with
three carbonyl O-atoms remaining uncoordinated which is quite
different from that of both benzyl and pyridyl terminal group
reported before [11f]. Representative bond lengths and angles are
listed in Table S2 (ESI). Therefore, the structure of ErIII complex
was described in detail to introduce the structure II. ErIII complex
dimensional
directions,
forming
the
three-dimensional
interpenetration coordination polymers which is quite different
from that reported recently [11f] showing an interesting terminal
effect on structures.
Better insight into the nature of this complicated framework
can also be achieved by the application of topological approach,
reducing multidimensional structures to simple node and con-
nection nets. As discussed above, in this framework, each nona-
coordinated Nd3+ ion is linked with three ligands through
carbonyl groups, which could be considered as an inorganic
trigonal node with short topological terms of 83. Each L ligand in
turn is connected with four Nd3+ ions through carbonyl groups, so
it could be regarded as an organic tetrahedron linker. There are six
eight-membered rings around the four-connected linker, while
three eight-membered rings around the three-connected metal
node, resulting in a ligand linker topology of 86 as well as a metal
node topology of 83. For the four-connected linkers and three-
connected nodes are arranged in a ratio of Nd/L=3:4, the short
Schla¨fli symbol of the topology can be expressed as (86)3(83)4
(Fig. 2) which is similar to literature [11f]. It is interesting to note
that the ligand L were also arranged in exactly the same
conformation as that of literature reported [11f], indicating that
shows
a mononuclear structure with the asymmetric unit
containing one crystallographically unique Er3+ ion, one neutral
ligand, three bidentate nitrates, one coordinated methanol, one
coordinated water molecule and one crystalline acetone molecule.
A view of the molecular structure, together with its numbering
scheme, is depicted in Fig. 3. The ErIII atom is in a distorted [ErO9]
monocapped square antiprismatic coordination geometry. Among
them one oxygen atoms O2 is from carbonyl group of the ligand
˚
and the Er–O bond length is 2.244(4) A, six oxygen atoms (O13,
O14, O16, O17, O19 and O20) are from bidentate nitrate groups,
and the Er–O bond lengths are 2.474(4), 2.433(45), 2.400(4),
˚
2.427(4), 2.407(4) and 2.446(4) A, respectively, the other two
oxygen atoms O22 and O23 are from methanol and water
molecular, and the Er–O bond lengths are 2.345(4) and
˚
2.274(4) A, respectively. All of the bond lengths for Er–O fall into
normal ranges.
It is well-known that the most important driving forces in
crystal engineering are coordination-bonding and hydrogen-
Fig. 2. Topological representation of the binodal (4,3)-connected (86)3(83)4 net
built on the 4-connected organic space(a) and 3-connected metal centres(b) in
coordination polymer of L (the connectors of ligand L and Nd atoms are colored in
gray and purple, respectively). (For interpretation of the references to colour in this
figure legend, the reader is referred to the web version of this article.)
Fig. 3. ORTEP plot of ErIII nitrate complex showing the local coordination
environment of ErIII with thermal ellipsoids at 30% probability (Crystalline acetone
molecule and hydrogen molecules are omitted for clarity).

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5
bonding interactions. Extended networks assembled by both
coordination and hydrogen bonds are one of the important
strategies to construct supramolecular networks [14]. In principle,
high dimensionality networks can be obtained by the assembly of
small molecules via hydrogen bonding interactions. A series of
such compounds, was reported before [11a,11c,11d,11f,15].
Notably, significant intermolecular hydrogen bonding interac-
tions shown in Table 3 exist between the monomers which are the
most important factors preventing ErIII complex from assembling
into infinite coordination polymers. First, the monomer are held
together into
a dimer cage via hydrogen bonding between
uncoordinated carbonyl oxygen atoms and amide nitrogen
atoms (Fig. 4) with the other two uncoordinated arms as well as
ErIII coordination sphere dangling freely in the outside. This gives
˚
rise to a Er?Er distance of 19.077 A. There is only one inversion
Table 3
center (i) without any crystallographically imposed symmetry for
the ligands or the metal centers in the cage. The N1?O8 distance
and N1–H1?O8 angle are both within ranges of those reported
hydrogen bonds. Further, the supramolecular dimers are
connected by the hydrogen bonding between oxygen atoms of
coordinated methanol molecule and oxygen atoms of nitrate to
form a one-dimensional supramolecular chain (Fig. 5). The O22–
H5?O15 angle led to this series of hydrogen bonds being defined
as linear. Finally, the other uncoordinated carbonyl oxygen atoms
(O5 and O11) can interact with the oxygen atoms of the
coordinated water (O23) in two directions to form an interesting
Representative intermolecular hydrogen-bonding parameters in the {[ErL(NO3)3(-
CH3OH)(H2O)] ꢀ C3H6O} complex.a
D—H?A
D—H?A (1)
˚
˚
˚
D—H (A)
H?A (A)
D?A (A)
N1—H1?O8i
0.86
0.85
0.84
0.84
1.95
1.97
1.79
1.93
2.789(6)
2.807(5)
2.622(6)
2.712(6)
167
170
179
155
O22—H5?O15ii
O23—H6?O5iii
O23—H7?O11iv
a
Symmetry transformations used to generate equivalent atoms: (i) 1ꢁx, 1ꢁy,
2ꢁz; (ii) 1ꢁx, ꢁy, 2ꢁz; (iii) 1/2ꢁx, ꢁ1/2+y, 3/2ꢁz; (iv) ꢁ1/2+x, 1/2ꢁy, 1/2+z.
Fig. 4. The supramolecular dimer cage of ErIII nitrate complex constructed by hydrogen bonding between uncoordinated carbonyl oxygen atoms and amide nitrogen atoms
which are indicated with dashed orange lines (symmetry codes: 1ꢁx, ꢁy, 1ꢁz). (For interpretation of the references to colour in this figure legend, the reader is referred to
the web version of this article.)
Fig. 5. The 1D supramolecular chains of ErIII nitrate complex constructed by hydrogen bonding between coordinated water molecules and oxygen atoms of coordinated
nitrate which are indicated with dashed orange lines. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this
article.)

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2.357(7)–2.514(6) A and the NdIII coordination polyhedron
˚
is fairly distorted and best described as an anti-square prism.
The [NdL(H2O)6]3+ units self-assemble via intermolecular
N3–H3?O11 and N6–H6?O21 hydrogen-bonding interactions
where amide act as a N–H hydrogen-bond donor to the carbonyl O
atoms to form a zigzag chain as shown in Fig. 8. These chains are
further threaded via O25–H25B?O7, O27–H27B?O19, O28–
H28A?O19 and O30–H30A?O23 interchain hydrogen-bonding
interactions leading to a three-dimensional (3D) supermolecular
structure (Fig. 9). The representative intermolecular hydrogen
bonding parameters are listed in Table 4. In addition, the
intramolecular N–H?O hydrogen bonds, forming among the
carbonyl oxygens, amide nitrogen atoms, aqua ligands, and
perchlorate anions play a vital role in determining the crystal
packing and in the construction of the extended 3D
supramolecular network of NdIII perchlorate complex.
Comparison of the Structures. Investigations of the self-assem-
bly between lanthanide nitrate salts and perchlorate salts with
the tetrapodal ligand, five novel crystal products were isolated
and three types of structures were obtained. In the nitrate
lanthanide complexes, the coordination number (CN) of the LnIII
ion is nine, and the LnIII ion is located in the distorted
monocapped square antiprism. In the nitrate complexes the Ln–
Fig. 6. The 3D supramolecular chains of ErIII nitrate complex constructed by
hydrogen bonding which are indicated with dashed orange lines. (For interpreta-
tion of the references to colour in this figure legend, the reader is referred to the
web version of this article.)
˚
O average bond lengths decreased from 2.486 to 2.383 A with an
increase in atomic number which should be ascribed to the
lanthanide contraction effect together with the structure trans-
formation from structures I to structure II. Furthermore, the
crystal system and space group for structure I were cubic and
I-43d as well as monoclinic and P21/n for structure II. Compared
with the structure constructed with the related ligands [11f], the
coordination behavior of L was dramatically changed due to the
presence of four furan rings which affect the coordination mode of
the resulting tetrapodal ligand. The formation of 3D interpene-
trating network for the larger lanthanide ions takes place in a
terminal group which has a weaker hydrogening bond acceptor,
allowing the coordination of larger LnIII simultaneously by the
four salicylamide arms of the ligands and thus the assembly of the
rare 3D nets with topology of a (86)3 (83)4 notation. The type of
counter anion-depending structural variation can be understood
taking into account the plastic coordinative behaviour of the
ligand, modulated by the introducing five-membered furan ring at
the salicylamide arms combined with the poor coordinated and
large perchlorate anion as compared to the nitrate complexes.
Clearly, these unusual structural variations are an indication of
cooperative effect of overall complexity of the coordination
chemistry involved with this class of ligand and the lanthanide
contraction as well as counter anions. The binding of lanthanide
ions to the carbonyl oxygen atoms of ligands rather than to etheric
oxygen groups appears largely as a consequence of cooperative
effect of strong intramolecular hydrogen bonds and steric
hinderance inhibiting the formation of a reasonable coordination
geometry that involves the participation of all four ether oxygen
donors of each ligand similar to the reported before [11]. Given the
important steric demand and rigidity that the salicylamide group
represents, this scenario seems rather unlikely.
Fig. 7. ORTEP plot of NdIII perchlorate complex showing the local coordination
environment of NdIII with thermal ellipsoids at 30% probability (Crystalline water
molecule, perchlorate anion and hydrogen molecules are omitted for clarity).
three-dimensional supramolecular structures (Fig. 6). It is
remarkable that the smaller ionic radii involved as well as the
furan terminal group may creates ligand congestion and thus
effectively hinders the complete coordination of the other three
carbonyl oxygen atoms of the tetrapodal ligand.
Structure III. To confirm the role of different counter anions in
the self-assembly process of this ligand, perchlorate anions were
used instead of nitrate anions to perform the reaction. In the case
of the reactions of Ln(ClO4)3 ꢀ 9H2O with L in ethyl acetate/
acetone/methanol solution, pale purple crystalline NdIII perchlo-
rate complex was obtained. A representative molecular structure
plot of NdIII perchlorate complex together with its numbering
scheme, is depicted in Fig. 7. Compared to NdIII nitrate complex,
the NdIII perchlorate complex crystallizes in the triclinic space
group Pꢁ1 and the coordination ratio of ligand to metal is 2:1.
Representative bond lengths and angles are listed in Table S3 (ESI).
The metal ion is 8-fold coordinated by two ligands, six water
molecules with the NdIII ion sitting on a crystallographic inversion
centre, the perchlorate anions uncoordinatedly exist in the lattice
to balance the charge. The distances Nd–O are in the range
3.3. Luminescence properties of the Eu(III) complex in the solid state
Upon UV irradiation, the free ligand emits a strong blue
luminescence (apparent lmax at ca. 450 nm) that can be easily
detected with the naked eyes. However, upon complexation with
EuIII this emission is replaced by the typical luminescence color
arising from EuIII cation. To examine the ability of the ligand to be
antenna groups for sensitized luminescence from lanthanides, we
measured the luminescence properties of EuIII complex with the

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7
Fig. 8. The 1D supramolecular chains of NdIII perchlorate complex constructed by hydrogen bonding between uncoordinated carbonyl oxygen atoms and amide nitrogen
atoms which are indicated with dashed orange lines. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this
article.)
Fig. 9. The 3D supramolecular chains of NdIII perchlorate complex constructed by hydrogen bonding which are indicated with dashed orange lines. (For interpretation of
the references to colour in this figure legend, the reader is referred to the web version of this article.)
Interestingly, The luminescence emission spectra of EuIII
complex only displays the metal-centred line emissions
as shown in Fig. 10 which is quite different from the EuIII
Table 4
Representative intermolecular hydrogen-bonding parameters in the {[NdL2
(H2O)6] ꢀ 3ClO4 ꢀ 3H2O} complex.a
complex of the similar tetrapodal ligands [11f] showing a distinct
terminal effect. The emission peaks of EuIII complex, at 579, 592,
619, 687 and 695 nm can be assigned to 5D0-7FJ (J=0, 1, 2, 4)
transitions of the EuIII ion, respectively. Notably, the 5D0-7F2
transition which is well resolved is much more intense than the
5D0-7F1 transition, the large intensity ratio of EuIII complex for
I(5D0-7F2)/I(5D0-7F1) indicates the absence of an inversion
center at the EuIII site which is in agreement with the result
of single-crystal X-ray analysis. The fluorescence quantum
D—H?A
D—H?A (1)
˚
˚
˚
D—H (A)
H?A (A)
D?A (A)
N3—H3?O11i
0.86
0.86
0.87
0.91
0.90
0.88
2.08
1.96
1.84
2.30
1.73
1.84
2.848(12)
2.743(14)
2.674(9)
149
151
161
123
179
158
N6—H6?O211ii
O25—H25B?O7iii
O27—H27B?O19iv
O28—H28A?O19v
O30—H30A?O23vi
2.897(14)
2.623(12)
2.675(13)
a
Symmetry transformations used to generate equivalent atoms: (i) 1ꢁx, -y,
1ꢁz; (ii) 1ꢁx, 1ꢁy, 1ꢁz; (iii) 1ꢁx, 2ꢁy, ꢁz; (iv) ꢁx, 1ꢁy, ꢁz; (v) ꢁx, 1ꢁy, ꢁz;
(vi) 1ꢁx, 1ꢁy, ꢁz.
yield
F of the europium nitrate complex in solid state was
found to be 4.370.1% using an integrating sphere. The EuIII
complex luminescence decay is best described by a single-
exponential process with significantly longer lifetimes of
ligand. The excitation spectrum of the europium complex of the
ligand monitoring at the emission wavelength of 579 nm exhibits
a series of sharp lines characteristic of the EuIII energy-level
structure, this is quite similar to the report by us before [11].
t1=1.05870.001 ms, indicating the formation of a single species
which is substantiated through X-ray single-crystal analysis
(Fig. S1, ESI).

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X.-Q. Song et al. / Journal of Solid State Chemistry 183 (2010) 1–9
S2 and S3, Figure S1 and Figure S2). Crystallographic data for the
structural analysis have been deposited with the Cambridge
Crystallographic Data Center, CCDC No. 705664–705668. Copies
of this information may be obtained free of charge from the
director, CCDC, 12 Union Road, Cambridge CB2 IEZ, UK (e-mail:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgment
The authors acknowledge support from the National Natural
Science Foundation of China Research (Grants 20771048,
20431010, 20621091 and J0630962).
Appendix A. Supplementary material
Supplementary data associated with this article can be found
in the online version at doi:10.1016/j.jssc.2009.07.062.
Fig. 10. Room-temperature emission spectra for EuIII nitrate complex of ligand L in
solid state (lex=397 nm, excitation and emission passes=2.5 nm).
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