Acidic 1,3-propanediaminetetraacetato lanthanides with luminescent and catalytic ester hydrolysis properties

Article abstract of DOI:10.1016/j.jssc.2014.07.037

In acidic solution, a serials of water-soluble coordination polymers (CPs) were isolated as zonal 1D-CPs 1,3-propanediaminetetraacetato lanthanides [Ln(1,3-H₃pdta)(H₂O)₅]_n· 2Cl_n·3nH₂O [Ln=La, 1; Ce, 2; Pr, 3; Nd, 4; Sm, 5] (1,3-H₄pdta=1,3-propanediaminetetraacetic acid, C₁₁H ₁₈N₂O₈) in high yields. When 1 eq. mol potassium hydroxide was added to the solutions of 1D-CPs, respectively, two 1D-CPs [Ln(1,3-H₂pdta)(H₂O)₃] _n·Cl_n·2nH₂O [Ln=Sm, 6; Gd, 7] were isolated at room temperature and seven 2D-CPs [Ln(1,3-H₂pdta) (H₂O)₂]_n·Cl_n·2nH ₂O [Ln=La, 8; Ce, 9; Pr, 10; Nd, 11; Sm, 12; Eu, 13; Gd, 14] were isolated at 70 °C. When the crystals of 1-4 were hydrothermally heated at 180 °C with 1-2 eq. mol potassium hydroxide, four 3D-CPs [Ln(1,3-Hpdta)]_n·nH₂O [Ln=La, 15; Ce, 16; Pr, 17; Nd, 18] were obtained. The two 2D-CPs [Ln(1,3-Hpdta)(H₂O)] _n·4nH₂O (Sm, 19; Eu, 20) were isolated in similar reaction conditions. With the increments of pH value in the solution and reaction temperature, the structure becomes more complicated. 1-5 are soluble in water and 1 was traced by solution ¹³C{¹H} NMR technique, the water-soluble lanthanides 1 and 5 show catalytic activity to ester hydrolysis reaction respectively, which indicate their important roles in the hydrolytic reaction. The europium complexes 13 and 20 show visible fluorescence at an excitation of 394 nm. The structure diversity is mainly caused by the variation of coordinated ligand in different pH values and lanthanide contraction effect. Acidic conditions are favorable for the isolations of lanthanide complexes in different structures and this may helpful to separate different lanthanides. The thermal stability investigations reveal that acidic condition is favorable to obtain the oxides at a lower temperature.

Full text of DOI:10.1016/j.jssc.2014.07.037

Author's Accepted Manuscript
Acidic
1,3-propanediaminetetraacetato
lanthanides with luminescent and catalytic
ester Hydrolysis properties
Mao-Long Chen, Yu-Chen Yang, Zhao-Hui Zhou
www.elsevier.com/locate/jssc
PII:
S0022-4596(14)00342-9
http://dx.doi.org/10.1016/j.jssc.2014.07.037
YJSSC18573
DOI:
Reference:
To appear in: Journal of Solid State Chemistry
Received date: 17 May 2014
Revised date: 17 July 2014
Accepted date: 27 July 2014
Cite this article as: Mao-Long Chen, Yu-Chen Yang, Zhao-Hui Zhou, Acidic 1,3-
propanediaminetetraacetato lanthanides with luminescent and catalytic ester
Hydrolysis properties, Journal of Solid State Chemistry, http://dx.doi.org/10.1016/j.
jssc.2014.07.037
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Acidic 1,3-propanediaminetetraacetato lanthanides with luminescent
and catalytic ester hydrolysis properties
Mao-Long Chen, Yu-Chen Yang, Zhao-Hui Zhou*
College of Chemistry and Chemical Engineering, State Key Laboratory of Physical Chemistry of Solid
Surfaces, Xiamen University, Xiamen 361005, China
Abstract
In acidic solution, a serials of water-soluble coordination polymers were isolated as zonal
1D-CPs 1,3-propanediaminetetraacetato lanthanides [Ln(1,3-H3pdta)(H2O)5]n·2Cln·3nH2O [Ln =
La,
C11H18N2O8) in high yields. When 1 eq. mole potassium hydroxide was added to the solutions of
1D-CPs respectively, two 1D-CPs [Ln(1,3-H2pdta)(H2O)3]n·Cln·2nH2O [Ln = Sm, ; Gd, ] were
isolated at room temperature and seven 2D-CPs [Ln(1,3-H2pdta)(H2O)2]n·Cln·2nH2O [Ln = La,
Ce, ; Pr, 10; Nd, 11; Sm, 12; Eu, 13; Gd, 14] were isolated at 70 °C. When the crystals of
1; Ce, 2; Pr, 3; Nd, 4; Sm, 5] (1,3-H4pdta = 1,3-propanediaminetetraacetatic acid,
6
7
8
;
9
1−4
were hydrothermally heated at 180 °C with 1-2 eq. mole potassium hydroxide, four 3D-CPs
[Ln(1,3-Hpdta)]n·nH2O [Ln = La, 15; Ce, 16; Pr, 17; Nd, 18] were obtained. The two 2D-CPs
[Ln(1,3-Hpdta)(H2O)]n·4nH2O (Sm, 19; Eu, 20) were isolated in similar reaction condition. With
the increments of pH value in the solution and reaction temperature, the structure becomes more
13
complicated.
1
−
5
are soluble in water and
and 5 show catalytic activity to ester hydrolysis reaction respectively,
1
was traced by solution C{1H} NMR technique, the
water-soluble lanthanides
1
which indicate their important roles in the hydrolytic reaction. The europium complexes 13 and
20 show visible fluorescence at an excitation of 394 nm. The structure diversity is mainly caused
by the variation of coordinated ligand in different pH values and lanthanide contraction effect.
1

Acidic conditions are favorable for the isolations of lanthanide complexes in different structures
and this may helpful to separate different lanthanides. The thermal stability investigations reveal
that acidic condition is favorable to obtain the oxides at a lower temperature.
Keywords: Lanthanide; 1,3-propanediaminetetraacetic acid; ester hydrolysis, luminescent
_________________________
* Corresponding author. Tel.: +86 592 2184531; fax: +86 592 2183047 (Z.-H. Zhou).
E-mail address: zhzhou@xmu.edu.cn (Z.-H. Zhou).
1. Introduction
The chemistry of the coordination polymers has in recent years advanced extensively [1-7],
where the lanthanides often show applications in many fields such as gas adsorption and
separation [8, 9], chemical sensors [10], catalysts [11, 12], magnetic and luminescent materials [1,
6, 13], and so on. However, less concerns are focused on the design and synthesis of water-
soluble lanthanide-based coordination polymers which may have special solution state and easy
for separations and conversions [14-17].
In general, 1,3-propanediaminetetraacetic acid, which is an edta-like ligand (edta =
[CH2N(CH2CO2H)2]2), is a tetrabasic acid with eight potential O-donor and two N-donor atoms
for the formations of mononuclear water-soluble complexes [18]. Usually it coordinates with
transition center ions through its four oxygen atoms and two nitrogen atoms, like
M’II(H2O)6][MII(1,3-pdta)]·2H2O (M = Ca [19], Co [20, 21], Ni [22, 23], Cu [22, 24, 25] and
Zn[26]), [M’II(H2O)6][MII(1,3-pdta)(H2O)]·2H2O (M = Mn [27] and Cd [26, 27]), M’[MIII(1,3-
pdta)]·xH2O (M = Fe [28], Ru [29-31], V [32], Cr and Rh [33]), (PPh4)4[(W3SO3)2(1,3-
2

pdta)3]·39H2O [34], and insoluble coordination polymer (NH4)8n[Mo10O32(1,3-pdta)]n·30nH2O.[35]
Comparing with transition metals, lanthanide ions have high coordination number (CN) and
coordination flexibility. Involving ethylenediaminetetraacetate lanthanide complexes, they often
form monomeric complexes as transition metal complexes [36]. Unlike most of the monomeric
propanediaminetetraacetato transition metal complexes, propanediaminetetraacetato lanthanides
form dimeric M[Ln2(pdta)2(H2O)4] or polymeric complexes M’[Ln(pdta)(H2O)]n [37-46]. This
may come from the coordination versatility and flexibility of pdta ligand. Combination of these
might be expected to isolate different sorts of lanthanide complexes, which are also important
precursors in sol-gel processing [47, 48].
Previously, we have reported some lanthanide pdta complexes used as the precursors of
catalysts for the oxidative coupling of methane [49]. Herein, in acidic solution, five types of 1,3-
propanediaminetetraacetato lanthanides were isolated and fully characterized with the increments
of pH value and reaction temperature: 1D-CPs [Ln(1,3-H3pdta)(H2O)5]n·Cl2n·3nH2O [Ln = La,
1
;
;
;
Ce,
Gd,
2
; Pr,
3
; Nd,
4
; Sm,
5
] for type
a
, 1D-CPs [Ln(1,3-H2pdta)(H2O)3]n·Cln·2nH2O [Ln = Sm,
6
7
] for type
b
, 2D-CPs [Ln(1,3-H2pdta)(H2O)2]n·Cln·2nH2O [Ln = La,
8
; Ce,
9
; Pr, 10; Nd, 11
Sm, 12; Eu, 13; Gd, 14] were isolated at 70 °C for type
c, 3D-CPs [Ln(1,3-Hpdta)]n·nH2O [Ln =
La, 15; Ce, 16; Pr, 17; Nd, 18] for type , and samarium and europium complexes were isolated
d
as 2D-CPs [Ln(1,3-Hpdta)(H2O)]n·4nH2O (Sm, 19; Eu, 20) for type e. The former is used as a
catalyst for the ester hydrolysis.
2. Experimental
2.1 Synthesis
2.1.1 Preparation of [La(1,3-H3pdta)(H2O)4]n·2Cln·3nH2O (1).
3

KOH (1.12 g, 20.0 mmol) and 1,3-propanediaminetetraacetic acid (6.2 g, 20.0 mmol) were
dissolved in water (75 mL) and stirred for several minutes. LaCl3·7H2O (7.4 g, 20.0 mmol) was
added. The pH value was 1.5-2.0. The solution was stirred for half an hour and then standing in
air. Colorless crystalline materials were separated after evaporation of the solution. The solids
were washed with cold water and ethanol, and dried in the air. The yield of
1 was 92% (12.1 g).
Anal. Found (calcd. for C11H33N2O16Cl2La): C, 19.7 (20.0); H, 5.1 (5.0); N, 4.0 (4.2). IR (KBr
disk, /cm-1): 3404s, 3019s,
1254m, 1197m, 1119w, 1067m, 971w, 907w, 883m, 851w, 700m, 533w, 477w. Solution 1H NMR (500
(ppm) 3.993 (8H, s), 3.446 (4H, t, J = 7.5 Hz), 2.242 (2H, m); 13C NMR (500 MHz,
ν
as(CO2H), 1739s, 1707s, νas(CO2), 1616s; νs(CO2), 1413s; 1342m,
MHz, D2O):
δ
D2O):
δ
(ppm) 172.7 (−
C
O2), 59.6 (−
C
H2CO2), 56.0 (−N
C
H2−), 22.4 (−
were similar to that of
).
KOH (0.11 g, 2.0 mmol) and crystal or powder of [La(1,3-H3pdta)(H2O)4]n·Cl2n·3nH2O (
CH2−). Solubility in
water at 25 °C (~ 0.6 g·mL-1). Preparations of
2
~
5
1.
2.1.2 Preparation of [La(1,3-H2pdta)(H2O)2]n·Cln·2nH2O (
8
1
)
(1.32 g, 2.0 mmol) were dissolved in water (15 mL) and stirred for half an hour and then standing
in 70 °C. The pH value was 2.6-3.1. Colorless crystalline materials were separated after
evaporation of the solution. The solids were washed with water and ethanol, and dried in the air.
The yield of
8 was 81% (0.89 g). Anal. Found (calcd. for C11H24N2O12ClLa): C, 23.8 (24.0); H,
4.5 (4.4); N, 5.0 (5.1). IR (KBr disk, /cm-1): 3590s, 3442vs, 3396vs, 3315vs, 3176vs, 3138vs, 3044vs,
3022vs, 2999vs,
1348s; 1270w, 1251m, 1233m, 1211m, 1113w, 1058m, 1035m, 996w, 958m, 904m, 867m, 847w, 727m,
693m, 660m, 593m, 565w, 517w, 498w. Preparations of complexes 12 were similar to that of 8.
νas(CO2), 1670s, 1643vs, 1617vs; νs(CO2), 1471w, 1444s, 1434s, 1412vs, 1397vs,
9
-
Owing to the unsuccessful isolation of type a complexes for europium and gadolinium, complexes
13 and 14 were isolated only through one pot synthesis process. KOH (0.22 g, 4.0 mmol) and 1,3-
propanediaminetetraacetic acid (0.62 g, 2.0 mmol) were added in water (15 mL) and stirred for
4

several minutes, then EuCl3·7H2O (0.74 g, 2.0 mmol) was added. The solution was stirred for half
an hour and then standing in 70 °C. Colorless crystalline materials were separated after
evaporation of the solution. The solids were washed with water and ethanol, and dried in the air.
The yield of 13 was 78% (0.88 g). Anal. Found (calcd. for C11H24N2O12ClEu): C, 23.5 (23.4); H,
4.5 (4.3); N, 5.1 (5.0). IR (KBr disk, /cm-1): 3583s, 3441vs, 3331vs, 3181vs, 3125vs, 3051vs,
ν
as(CO2), 1677s, 1618vs;
999w, 964m, 906m, 871m, 725m, 693m, 596m, 567w, 523w, 499w, 414w. Preparations of 14 were
similar to that of 13
νs(CO2), 1399vs, 1350s, 1309vs;, 1236m, 1212m, 1114w, 1059m, 1036m,
.
2.1.3 Synthesis of [La(1,3-Hpdta)]n·nH2O (15).
KOH (0.06-0.11 g, 1.0-2.0 mmol), water (15 mL) and crystal or powder of [La(1,3-
H3pdta)(H2O)4]n·Cl2n·3nH2O (1) (1.32 g, 2.0 mmol) were sealed into a 25 mL teflon-lined
stainless steel vessel, heated at 180 °C for 60 h, and then slowly (40 h) cooled to room
temperature. Colorless crystalline materials were separated. The solids were washed with water,
and dried in the air. The yield of 15 was 65% (0.30 g). Anal. Found (calcd. for C11H17N2O9La): C,
28.8 (28.7); H, 3.9 (3.7); N, 6.1 (6.1). IR (KBr disk, /cm-1): 3481m, 3447m, 3126m, 3019w, 3002w,
2969w, 2899w, 2883w, νas(CO2), 1665s, 1636vs, 1614vs, 1599vs; νs(CO2), 1480w, 1401vs, 1385vs,
1334s, 1321m; 1296w, 1271w, 1254w, 1232m, 1161w, 1125w, 1090w, 1066w, 1031w, 994w, 980w,
916w, 878m, 864m, 759w, 738m, 718m, 615m, 595m, 551w, 541w, 484w. Preparations of complexes
16
-19 were similar to that of 15.
2.1.4 One pot synthesis of [La(1,3-H2pdta)(H2O)2]n·Cln·2nH2O (
8
).
KOH (0.22 g, 4.0 mmol) and 1,3-propanediaminetetraacetic acid (0.62 g, 2.0 mmol) were
dissolved in water (15 mL). LaCl3·7H2O (0.74 g, 2.0 mmol) was added. The solution was stirred
for half an hour and then standing in 70 °C. Colorless crystalline materials were separated after
evaporation of the solution. The solids were washed with water and ethanol, and dried in the air.
5

The yield of
4.5 (4.4); N, 5.0 (5.1). One pot synthesis of complexes
[Ln(1,3-H2pdta)(H2O)3]n·Cln·2nH2O [Ln = Sm, ; Gd,
room temperature
2.1.5 One pot synthesis of [La(1,3-Hpdta)]n·nH2O (15).
8
was 75% (0.83 g). Anal. Found (calcd. for C11H24N2O12ClLa): C, 23.8 (24.0); H,
14 were similar to that of . Synthesis of
] were similar to that of , but standing in
9
-
8
6
7
8
.
KOH (0.11-0.17 g, 2.0-3.0 mmol), 1,3-propanediaminetetraacetic acid (0.31 g, 1.0 mmol),
water (15 mL) and LaCl3·7H2O (0.37 g, 1.0 mmol) were sealed into a 25 mL teflon-lined stainless
steel vessel, heated at 180 °C for 60 h, and then (40 h) cooled to room temperature. Colorless
crystalline materials were separated. The solids were washed with water, and dried in air. The
yield of 15 was 55% (0.25 g). Anal. Found (calcd. for C11H17N2O9La): C, 28.8 (28.7); H, 3.9 (3.7);
N, 6.1 (6.1). One pot synthesis of complexes 16-20 were similar to that of 15.
2.2 X-ray diffraction data
Suitable single crystals of
prevent the loss of water molecules. X-ray diffraction data were measured at 173 K on an Oxford
CCD diffractometer with Mo K radiation (λ = 0.71073 Å). Empirical adsorption was applied to
1-20 were selected and quickly mounted onto thin glass fibers to
α
all data using SADABS and CrysAlis (multi-scan) program. The initial model was obtained
through direct methods and the completion of the rest of the structure achieved by difference
Fourier strategies. The structures were refined by least squares on F2, with anisotropic
displacement parameters for non-H atoms. All calculations to solve and refine the structures and
to obtain the derived results were carried out with the computer programs SHELXS 97, and
SHELXL 97 programs.[50, 51] CCDC deposition numbers are 967707-967717 and 967719-
967727. Crystal data and structures refinements for 1-20 are summarized in Table S1-S3.
6

2.3 Physical measurements
All chemicals were of analytical or reagent-grade purity and used as received. The pH value
was measured by potentiometric method with a PHB-8 digital pH meter. Elemental analyses (C,
13
1
H, N) were performed by EA1110 elemental analyzer. Solution C and H NMR spectra were
recorded in D2O on a Bruker AV 500 M NMR spectrometer using DSS (sodium 2,2-dimethyl-2-
silapentane-5-sulfonate) as the internal reference. A Bruker esquire 3000plus instrument was used
to record the Electrospray ionization (ESI) mass spectra. Infrared spectra were recorded as KBr
disks and as mulls in Nujol with a Nicolet 330 FT-IR spectrophotometer. Thermogravimetric
analysis were recorded on SDT-Q600 thermal analyzer, under an air flow of 100 ml·min-1 at a
heating rate of 10 °C·min-1. Luminescent spectra were recorded on Hitachi F7000 spectrometer.
3. Results and discussion
3.1 Synthesis
Previously, it is reported that reactions of lanthanide salts with pdta result in the coordination
of nitrogen atoms and oxygens of pdta [37-46]. While isolation of water-soluble coordination
polymer shows that nitrogen atoms do not coordinate with lanthanide ions and could be
transformed to the other species in this report as shown in Scheme 1. The synthesis of [Ln(1,3-
H3pdta)(H2O)5]n·Cl2n·3nH2O (1-5) were carried out in strong acidic aqueous solutions.
Combinations of LnCl3/H4pdta/KOH in molar ratio of 1 : 1 : 1 resulted in the formation of soluble
1D-CPs (type a) with a high yield of 92% for lanthanum complex
hydroxide were added into their solution to adjust the pH value to 2.6-3.1, two new 1D-CPs
[Ln(1,3-H2pdta)(H2O)3]n·Cln·2nH2O [Ln = Sm, ; Gd, ] (type b) were isolated at room
temperature and seven 2D-CPs [Ln(1,3-H2pdta)(H2O)2]n·Cln·2nH2O ( 14) (type c) were isolated
1. When more potassium
6
7
8
-
at 70 °C. When crystals of
1
−
4
were heated at 180 °C with 1-2 eq. potassium hydroxide, four 3D
7

coordination polymers [Ln(1,3-Hpdta)]n·nH2O [Ln = La, 15; Ce, 16; Pr, 17; Nd, 18] (type d). Two
2D coordination polymer [Ln(1,3-Hpdta)(H2O)]n·4nH2O (Sm, 19; Eu, 20) (type e) were isolated
in similar condition. Moreover, as shown in Scheme 1, complexes type b and c can be directly
transformed to type d and e complexes. The yields are high (90-95 %) for type d and e complexes
in this method. We found that in moderate acidic solution, lanthanide complexes show little
lanthanide contraction effect at moderate temperature. But in strong acidic solution, there exist
obvious difference that makes the isolation of similar complexes of europium and gadolinium
difficult. In high temperature, there show lanthanide contraction effect that makes complexes 19
and 20 show different structure with complexes 15-18 in similar reaction conditions, which has
found in some systems like 3-aminopyrazine-2-carboxylic acid and isonicotinate-N-oxide
lanthanide system [13, 52-54].
[Scheme 1]
3.2 Crystal structures analysis
X-ray structure analysis revealed that [La(1,3-H3pdta)(H2O)5]n·Cl2n·3nH2O (1) is a zonal
coordination polymer with mononuclear subunit [La(1,3-H3pdta)(H2O)5] as shown in Figure 1. In
an asymmetric unit, La(III) cation exists in nonadentate coordination environment, which contains
four carboxy oxygen atoms and five water molecules. H3pdta uses its two carboxy oxygen atom
bonded to different nitrogen atoms to chelate one lanthanum ions, forming a twelve membered
ring, and still uses its other two carboxy oxygen atoms to coordinate with other two lanthanum
ions, forming a 1D-CP structure as shown in Figure 2. The 1D- CP structure was extended to a 3D
supramolecular structure through hydrogen bonds between water molecules and Cl−. It is
interesting to note that in
Å, + 1, + + 1]. The molecular structures of
Figures S1-S4.
1
there is a very strong intramolecular hydrogen bond [O4···O8 2.398(9)
x
y
,
z
2
-
5
are isomorphous with that of , as shown in
1
8

[Figures 1 and 2]
[Sm(1,3-H2pdta)(H2O)3]n·Cln·2nH2O (
6
) is also a 1D-CP. In an asymmetric unit, Sm(III)
cation exists in nonadentate coordination environment, which contains six carboxy oxygen atoms
from three different H2pdta and three water molecules as shown in Figure 3. H2pdta uses its two
carboxy groups bonded to different nitrogen atoms to chelate with one Sm(III) cation, one
forming a four membered chelated ring with Sm3+. It still uses its other two carboxy groups to
coordinate and chelate with other two Sm3+. This makes it form an infinite 1D-CP as shown in
Figure 4. The structure of
7
is similar to that of
[Figures 3 and 4]
[La(1,3-H2pdta)(H2O)2]n·Cln·2nH2O ( ) is a 2D-CP. In an asymmetric unit, La(III) cation
exists in octadentate coordination environment, which contains six carboxy oxygen atoms from
four different H2pdta and two water molecules as shown in Figure 5. Comparing the formula of
with , there is only one less coordination water molecule in , but there exist big difference in
6 as shown in Figure S5.
8
8
6
8
structures. H2pdta uses its two carboxy groups bonded to different nitrogen atoms to coordinate
with one La(III) cation, one still use its other carboxy oxygen atom to coordinate with another
La(III) cation. It still uses its other two carboxy groups to coordinate and chelate with other three
La3+. This makes it form an infinite 2D-CP as shown in Figure 6. The structures of 9-14 are
similar to that of
8
as shown in Figures S6-S11.
[Figures 5 and 6]
X-ray structure analysis revealed that [La(1,3-Hpdta)]n·nH2O (15) is a 3D-CP with neutral
mononuclear subunit [La(1,3-Hpdta)]n and one crystal water molecules, as shown in Figures 7
and 8. In an asymmetric unit, La(III) cation exists in nonadentate coordination environment,
which contains eight carboxy oxygen atoms from six different Hpdta ligands and one nitrogen
9

atom. These Hpdta ligands make the compound be a 3D-CP. The structures of 16-18 are similar to
that of 15 as shown in Figures S12-S14.
[Figures 7 and 8]
The crystal structure of 19 consists of a dimeric neutral unit [Sm2(Hpdta)2(H2O)2]n and eight
crystallized water molecules, as shown in Figure 9. Samarium ion is octa-coordinated, Sm1 is
surrounded by six oxygen atoms from four different trident acetates of Hpdta anion, one nitrogen
and one water molecule. Two chelated rings are formed by nitrogen and oxygen atoms of Hpdta,
which further couples with the other carboxy group of Hpdta into a dimeric unit. For the
structures of 19, the dimeric units further connected by the oxygen atoms of carboxy groups to
generate infinite 2D layered structures respectively as shown in Figure 9, and forms 3D
supramolecular structures by intermolecular hydrogen bonds. The molecular structure of 20 is
similar to 19, as shown in Figure S15.
[Figure 9]
10

Table 1. Selected bond lengths (Å), coordination number (C.N.) of lanthanide and dentate
number (D.N.) of pdta ligands for 20
1
-
.
Entry
-La
-Ce
-Pr
-Nd
Ln-Ocarboxy(av)
2.562(5)
Ln–N
Ln–Ow (av)
2.566(5)
C.N.
9
D.N.
4
1
－
2.541(4)
2.528(4)
2.522(7)
2.493(3)
2.488(4)
2.461(3)
2.505(2)
2.478(2)
2.460(2)
2.447(2)
2.416(2)
2.407(2)
2.392(2)
2.571(4)
2.552(5)
2.553(6)
2.523(3)
2.537(4)
2.526(5)
2.513(7)
2.488(3)
2.445(4)
2.417(3)
2.553(2)
2.523(2)
2.505(2)
2.491(2)
2.464(2)
2.445(2)
2.432(2)
9
9
9
9
9
9
8
8
8
8
8
8
8
9
9
9
9
4
4
4
4
6
6
6
6
6
6
6
6
6
9
9
9
9
2
－
－
－
－
－
－
－
－
－
－
－
－
3
4
5
6
-Sm
-Sm
7
-Gd
-La
-Ce
8
9
10-Pr
11-Nd
12-Sm
13-Eu
14-Gd
15-La
16-Ce
17-Pr
－
2.858(3)
－
－
－
－
2.825(3)
2.798(4)
2.780(2)
18-Nd
19-Sm
20-Eu
2.481(5)
2.471(5)
2.711(5)
2.692(5)
2.450(6)
2.441(5)
8
8
7
7
Selected bond lengths (Å), coordination number (C.N.) of lanthanide and dentate number
(D.N.) of pdta ligands for 20 were shown in Table 1. From the table, we found obvious
1
-
lanthanide contraction effect. The bond distances decreases with the increases of lanthanide
number. The coordination number (C.N.) of lanthanide shows little relationship with lanthanide
11

number, but the temperature and pH values will affect the C.N. of lanthanide. The C.N. of
complexes 14 and 19 and 20 is eight, while the others are nine. Comparing the C.N. of 15 18
8
-
-
with 19 and 20, obviously, this C.N. differences come from the lanthanide contraction effects. We
also found out that the number of coordinate water molecules decreases and the dentate number of
pdta increases with the increases of pH values.
3.3 Solution analysis
Solution 13C NMR spectra of
1
and H4pdta are showed in Figure 10. Solution 1H NMR spectra
13
are listed in Figures S16 ~ S17. Comparing C NMR spectrum of
1 with that of H4pdta, there
exist small downfield shift. Moreover, it is the fact that two kinds of carboxy carbon in
1 give
13
only one set of C NMR signal at 172.7 ppm (∆δ = 0.8 ppm) and one −
C
H2CO2 signal at 59.6
is quite small, we cannot make sure the coordination state in
aqueous state. But these can indicate the less strongly bounded carboxy group get the same
chemical environment with the other carboxy groups that bounded to the same nitrogen in
There is also only one set signal of −CH2N− (56.0 ppm, ∆δ = 0.2 ppm) and −CH2N− (22.4 ppm,
δ = 0.2 ppm) in . For the better understanding of its solution state, the ion signals of the water
solution mass spectra for were measured in the positive ionization (negative mode show very
little signal) mode by ESI. As shown in Fig. S18, compound exhibited three strong peaks at
ppm (∆δ = 0.8 ppm). For the ∆
δ
1
.
∆
1
1
1
130.5, 253.1 and 446.7 m/z, the corresponding calculated unit is not very clear. But we can make
sure that the 446.7 m/z is bigger than that of [La(1,3-H2pdta)]+ (m/z = 443.2) and may correspond
to [La5(1,3-H2pdta)5H2O]5+ (m/z = 446.8). Then we detected the mass spectra in methanol and
water solution (CH3OH: H2O = 2:1). As shown in Fig. S19, the three strong peaks also existed,
but another peak at 575.4 m/z grown a lot. The new strong peak may correspond to the dimeric
unit. This indicate compound
1
in solution state may exist in aggregate state in a certain
12

percentage, and in water solution, the aggregate state is less than in a mixed methanol-water
solution. This is consistent with the solution 13C NMR analysis.
In 1H NMR spectrum of H4pdta (Fig. S16), the eight acetate protons are equivalent and result
in one signal at 4.061 ppm. The four –CH2N– protons are equivalent and result in a triple signal
centred at 3.433 ppm, and the two protons of –CH2– give a penta-signal centred at 2.249 ppm.
When we compare the 1H NMR spectra of H4pdta and lanthanum complex
1 (Fig. S17), we find
13
out that they give only one set of signal which is consistent with the C NMR spectra. Through
1
the H NMR spectrum of
1
, we can find a singlet at 3.993 ppm (8H, s, ∆δ = −0.068 ppm) for
acetate protons and a tri-signal centred at 3.446 ppm (4H, t, J = 7.5 Hz, ∆δ = 0.033 ppm) for the –
CH2N– protons and multiple peaks centred at 2.242 (2H, m, ∆δ = –0.007 ppm). There are small
∆
δ
for
1
. This is an indication for the weak coordination of propanediaminetetraacetate in
[Figure 10]
1.
3.4 IR spectra analysis
IR vibrational spectra of 1-20 are listed in Figures S20-S22. In the region between 1630 and
1540 cm-1 and between 1450 and 1320 cm-1, compounds 1-20 give two typical bands that
correspond to the bounded carboxy group
, there are protonated carboxy groups and give an absorption peak around 1709 cm-1. The value
(COO-)as − (COO-)s] is about 203 cm-1 in
1 suggests that the monodentate coordination of
ν ν
as(COO-) and s(COO-), respectively. In complexes 1-
5
of [
ν
ν
the carboxy groups. These changes confirm that the oxygen atoms from the carboxy groups of
pdta have coordinated with the centre ions.[55] A broad (OH) band near 3404 cm-1 indicates H2O
at 1067 cm-1 displays no obvious shift compared
with that of H4pdta (1068 cm-1), suggesting that nitrogen atoms of pdta are not coordinated to
ν
in the complex 1-5. The ν(C−N) of complexes 1
lanthanum. These are also observed for
2
-1
4
. The ν(C−N) of complexes 15-20 display two bands
13

around 1100 cm-1, one displays obvious blue-shift compared with that of H4pdta, suggesting that
one nitrogen atom of pdta coordinate with the centre ions.
3.5 Thermogravimetric analysis
Thermal stability and decomposition patterns of the complexes were investigated by thermo-
gravimetric analyses. The TG-DTG curves are listed in Figures S23-S42. As shown in Figure 11,
the first part of big weight losses of
and one hydrogen chloride. Then some coordinated water molecules lose at 218 °C. The ligand
may decompose from 286 to 461 °C. The final residue of compound is LaOCl. Comparing the
TG curves of lanthanum compounds (type a), (type c) and 15 (type d), we found out that
1 at 110 °C corresponds to the loss of crystal water molecules
1
1
8
acidic condition is helpful to get oxides at a lower temperature. Similar results can be found in the
other lanthanide compounds of these three types of lanthanide compounds. The remainder four
compounds of type b and type e didn’t show this feature.
[Figure 11]
3.6 Luminescent spectra analysis
Figure 12 shows the luminescent spectra of the obtained europium polymers 13 and 20. Four
curves represent the spectra of excitation and emission spectra of 13 (blue and black curves) and
20 (red and violet curves), respectively. The excitation spectra are obtained by monitoring the
emission of europium polymers at 595 or 615 nm. For excitation spectra of these two polymers,
eight absorption bands are found in the range of 315–470 nm, suggesting the effective absorption
of the hybrid systems. And these two polymers show similar excitation spectra. Therefore, in
order to compare the emission spectra of these two hybrid materials under the same conditions,
they should be monitored using the same and the most appropriate excitation wavelength (394
5
nm). As a result, the emission lines of the polymeric hybrid materials are obtained from the D0–
14

7FJ (J = 0–4) transitions at about 580, 590, 595, 614, 618, 652 nm for 13 and 580, 587, 596, 615,
625 and 652 nm for 20. Among these emission peaks of 20, the most striking red fluorescence
signals (5D0–7F2) of the induced electric dipole transition at about 615 nm is stronger than the
5
orange emission intensities of the magnetic dipole transition D0–7F1 at about 596 nm, which
indicates an Eu3+ site in an environment without inversion symmetry.[56-58] While for polymer
13, they show different emission spectra with 20, the most striking fluorescence signals is the
5
magnetic dipole transition D0–7F1 at about 595 nm, and the induced electric dipole transition at
about (5D0–7F2) 618 nm is a little weaker than the orange emission intensities at 595 nm. As can
be seen from the spectra, these two polymers show a different ratio of red/orange, which indicated
that they have a different coordination environment. This is consistent with structure analysis.
Furthermore, we compared the relative luminescent intensities of these two europium polymers.
To ensure the accuracy of comparison and prevent insufficient absorption of the exciting radiation,
a powder layer around 2 mm was used and utmost care was taken in order to ensure that only the
sample was illuminated and the measurements were under the same conditions. Then we found
the relative intensity of 20 is stronger than that of 13
[Figure 12]
3.7 Catalytic activity for ester hydrolysis reaction
.
In a typical experiment, four test tubes with 4.0 mL water solution were tested for the
catalytic esterification. The solution contains 1.0 mmol catalysts of [La(1,3-
H3pdta)(H2O)5]n·2Cln·3nH2O (1), [Sm(1,3-H3pdta)(H2O)5]n·2Cln·3nH2O (5), KH3pdta and LaCl3,
respectively. Each tube was added with one drop of 0.1 mol·L-1 methyl orange for the clarity of
observation. Then 1.0 mL ethyl acetate (~10 mmol) was added to the above solution respectively,
o
and the catalytic reaction temperature was maintained at 70 C. The height of the upper solution
was measured every 15 minutes as shown in Table 2. Water-soluble coordination polymers 1 and
15

5
can hydrolyze ethyl acetate with a certain speed. This is because that both of the lanthanides
have weak acid properties in solution. It seems that samarium propanediaminetetraacetate gives
little better catalytic activity than that of lanthanum propanediaminetetraacetate , which is
5
1
attributed to the lanthanide contraction and the decrease of basicity in samarium catalyst.
Moreover, ethyl acetate shows no hydrolysis by the independent ligand of KH3pdta or LaCl3 salt
as a blank sample. Synergistic effects of lanthanide and the ligand may play an important role in
the catalytic reaction of ester hydrolysis. In another word, the ester hydrolysis was catalyzed by
hydrogen 1,3-propanediaminetetraacetato lanthanide, which is interesting result for the ester
hydrolysis by water-soluble coordination polymer.
Table 2. The height of the ethyl acetate in every 15 minutes.a
0 min
15.0 min
7.0 mm
7.0 mm
9.0 mm
9.0 mm
30.0 min
5.9 mm
5.7 mm
9.0 mm
9.0 mm
1
5
9.0 mm
9.0 mm
9.0 mm
9.0 mm
KH3pdta
LaCl3
a
When ethyl acetate was hydrolyzed, the products of acetic acid and ethanol can be dissolved in aqueous phase
which contains methyl orange. Thus, the height of organic phase for ethyl acetate can be observed easily and
decreased with the hydrolyzed process
.
4. Conclusions
In summary, novel rare-earth coordination polymers possessing different types of structures
for 1,3-propanediaminetetraacetatic acid have been successfully isolated under acidic conditions,
which exhibit water-soluble 1D-CPs LnH3pdta (La, Ce, Pr, Nd, Sm) and 1D-CPs LnH2pdta (Sm,
Gd), 2D-CPs LnH2pdta (La, Ce, Pr, Nd, Sm, Eu, Gd) and LnHpdta (Sm, Eu), as well as 3D-CPs
LnHpdta (La, Ce, Pr, Nd). The structure diversity is mainly caused by the variation of coordinated
ligand and lanthanide contraction effect. The thermal stability investigations reveal that acidic
16

condition is helpful to get oxides at lower temperature. The successful synthesis of the twenty
complexes provides a valuable approach for the construction of rare-earth coordination polymers
tuned by pH value, temperature and lanthanide contraction effect. Moreover, the catalytic
activities of
1 and 5 to ester hydrolysis and the luminescent spectra of europium polymers 13 and
20 were also researched. Efforts to further systematic studies for these and other lanthanide
complexes are ongoing.
Acknowledgements
This work was financially supported by the National Science Foundation of China and the
Ministry of Science and Technology of China (2010CB732303) and PCSIRT (No. IRT1036).
Appendix A. Supplementary data
† ABBREVIATIONS: 1,3-H4pdta, 1,3-propanediaminetetraacetatic acid CH2[CH2N(CH2CO2H)2]2;
1D-CP, one dimensional coordination polymer; 2D-CP, two dimensional coordination polymer; 3D-
CP, three dimensional coordination polymer; eq., equivalent.
1
Electronic Supplementary Information (ESI) available: Ortep structures of the other complexes, H
NMR spectra, IR spectra, TG-DTG curves, and the X-ray crystallographic data of
format.
1-20 in CIF
17

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Figure legends
Scheme 1. Synthesis and conversions of five types of acidic lanthanide pdta coordination
polymers.
Figure 1. Ortep cation structure of [La(1,3-H3pdta)(H2O)5]n·2Cln·3nH2O (1) in 30% thermal
ellipsoids.
Figure
H3pdta)(H2O)5]n·Cl2n·3nH2O (
Figure Ortep structure
[Sm(H2pdta)(H2O)3]n·Cln·2nH2O ( ) in 30% thermal ellipsoids.
2
.
The infinite 1D acidic zonal coordination structure of [La(1,3-
1
).
3
.
of
dimeric
cation
[Sm2(H2pdta)2(H2O)6]2+
of
n
6
Figure 4. The infinite 1D structure of [Sm(H2pdta)(H2O)3]n·Cln·2nH2O (
6).
Figure 5. Structure of dimeric cation [La2(H2pdta)2(H2O)4]2+ of [La(H2pdta)(H2O)2]n·Cln·2nH2O
n
(
8
) in 30% thermal ellipsoids.
Figure 6. The infinite 2D structure of [La(H2pdta)(H2O)2]n·Cln·2nH2O (
8
).
Figure 7. Ortep neutral mononuclear subunit [La(1,3-Hpdta)]n of [La(1,3-Hpdta)]n·nH2O (15) in
30% thermal ellipsoids.
Figure 8. The infinite 3D structure of [La(1,3-Hpdta)]n·nH2O (15).
Fugure 9. Dimeric neutral unit [Sm2(Hpdta)2(H2O)2]n of [Sm(1,3-Hpdta)(H2O)]n·4nH2O (19) in
30% thermal ellipsoids and infinite 2D layered structure.
Figure 10. Solution 13C NMR spectra of
1 and 1,3-H4pdta.
Figure 11. TG curves of five types of lanthanide compounds.
Figure 12. Excitation and emission spectra of the europium coordination polymer 13 and 20
.
22

Scheme 1
23

Figure 1
24

Figure 2
25

Figure 3
26

Figure 4
27

Figure 5
28

Figure 6
29