A novel quaternary dinuclear luminescent terbium complex Tb 2(phth)2(Hphth)2(phen)2(H 2O)4: Hydrothermal synthesis, crystal structure and photophysics

Article abstract of DOI:10.1016/j.molstruc.2004.03.012

Assembling potassium acid phthalate (KHphth), 1,10-phenanthroline (phen) and terbium nitrate, a novel quaternary dinuclear terbium complex with formula Tb₂(phth)₂(Hphth)₂(phen)₂(H ₂O)₄ (H₂phth=phthalic acid, phen=1,10-phenanthroline) has been firstly synthesized by hydrothermal process. X-ray analysis reveals that it forms dimeric structure and the two central terbium ions have the same coordination environment. The title complex crystallizes in the triclinic system, space group P_-1, with lattice parameters a=10.149(5)?, b=10.730(5)?, c=11.906(5)?, α=90.427(6)°, β=99.474(6)°, γ=101.088(6)°, F(000)=696, GOF=0.931, R₁=0.0308, wR₂=0.0606 and Z=1. The photophysical properties have been studied with ultraviolet absorption spectrum, excitation and emission spectrum, which exhibit strong green emission.

Full text of DOI:10.1016/j.molstruc.2004.03.012

Journal of Molecular Structure 694 (2004) 115–120
www.elsevier.com/locate/molstruc
A novel quaternary dinuclear luminescent terbium complex
Tb2(phth)2(Hphth)2(phen)2(H2O)4: hydrothermal synthesis,
crystal structure and photophysics
a,
Bing Yan , Yi-Shan Song , Zhen-Xia Chen
a
b
*
aDepartment of Chemistry, Tongji University, Shanghai, China
bDepartment of Chemistry, Fudan University, Shanghai, China
Received 22 December 2003; revised 18 February 2004; accepted 4 March 2004
Abstract
Assembling potassium acid phthalate (KHphth), 1,10-phenanthroline (phen) and terbium nitrate, a novel quaternary dinuclear terbium
complex with formula Tb2(phth)2(Hphth)2(phen)2(H2O)4 (H2phth ¼ phthalic acid, phen ¼ 1,10-phenanthroline) has been firstly synthesized
by hydrothermal process. X-ray analysis reveals that it forms dimeric structure and the two central terbium ions have the same coordination
˚
environment. The title complex crystallizes in the triclinic system, space group P-1; with lattice parameters a ¼ 10:149ð5Þ A,
˚
˚
b ¼ 10:730ð5Þ A, c ¼ 11:906ð5Þ A, a ¼ 90:427ð6Þ8; b ¼ 99:474ð6Þ8; g ¼ 101:088ð6Þ8; Fð000Þ ¼ 696; GOF ¼ 0:931; R1 ¼ 0:0308; wR2 ¼
0:0606 and Z ¼ 1: The photophysical properties have been studied with ultraviolet absorption spectrum, excitation and emission spectrum,
which exhibit strong green emission.
q 2004 Elsevier B.V. All rights reserved.
Keywords: Terbium (III); Hydrothermal analysis; Dimeric complex; Molecular structure; Photophysical property
1. Introduction
capability of acting as bridging ligands in various
coordination modes [12].
In recent years, lanthanide complexes have received
much attention because of their interesting photophysical
properties which have potential application in the lumines-
cence probes for chemical or biological macromolecules
and the active center for luminescent materials [1–4]. And
considerable studies have been focused on the design and
assembly of lanthanide complexes with organic ligands
such as aromatic carboxylic acids, b-diketone, cryptands,
calixarenes and heterocyclic ligands, etc. Among the
lanthanide complexes with aromatic carboxylic acids
show higher thermal or luminescent stabilities for practical
application than other lanthanide complex systems
because they readily form the dimer or infinite chain
polymeric structures [5–11]. In all types of carboxylic
acids, benzenedicarboxylate dianions are widely used in
the construction of coordination polymers due to their
And much interest has been paid to the preparation of
lanthanides aromatic carboxylates under hydrothermal
conditions [13–17]. Many coordination polymers of
lanthanides with benzenedicarboxylate such as phthalate as
bridged groups between metal centers have been
reported [18–27]. In this paper, we describe the
hydrothermal synthesis, structure and luminescent
properties of a new lanthanide phthalate coordination
complex Tb2(phth)2(Hphth)2(phen)2(H2O)4.
Previously, structures of lanthanide complexes
{[Ln2(phth)3(phen)(H2O)2]·3H2O}n (Ln ¼ Nd, Ho)
have been reported using o-phthalic acid (H2phth) as the
starting ligand [19]. While here KHphth was used as reaction
species instead of H2phth, and so the pH value of the reaction
solution need not be adjusted. It is interesting that the
resulting crystal forms an unexpected dimeric structure based
on each bridging phth molecules chelated to two Tb
atoms using carboxyl groups and Tb atom connects
two chelating-bridging phth molecules, which exhibits
*
Corresponding author. Tel.: þ86-21-65984663; fax: þ86-21-
65982287.
E-mail address: byan@tongji.edu.cn (B. Yan).
0022-2860/$ - see front matter q 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2004.03.012

116
B. Yan et al. / Journal of Molecular Structure 694 (2004) 115–120
obviously different from the reported {[Ln2(phth)3(phen)
(H2O)2]·3H2O}n.
graphite-monochromated Mo Ka radiation on a CCD
detector four-circle diffractometer, and data were collected
by the v-2u scan technique. The crystal structures were
solved by direct methods. All non-hydrogen atoms were
refined anisotropically by full-matrix least-squares methods
2
2. Experimental
P
2
2
on F2: The function minimized was wðlFol 2 lFcl Þ ;
2
21
where w ¼ ½s2ðFo2Þ þ ð0:0727PÞ þ 0:0000Pꢀ
and P ¼
2.1. Synthesis of Tb2(phth)2(Hphth)2(phen)2(H2O)4
ðFo2 þ 2Fc2Þ=3: Primary non-hydrogen atoms were solved by
directly method and secondary non-hydrogen atoms were
solved by difference maps. The hydrogen atoms were added
geometrically and not refined. All calculations
were performed using program SHELXS-97 and SHELXL-97
[28,29]. A summary of crystallographic data and refinement
parameters is given in Table 1.
Tb(NO3)3·6H2O were prepared by dissolving terbium oxide
in dense nitric acid and then dried. Other reagents were
commercially available and used without further purification.
Tb(NO3)3·6H2O (139 mg, 0.3 mmol), KHphth (92 mg,
0.45 mmol) and phen (59 mg, 0.3 mmol) were mixed in
10 ml deionized water. After stirring half an hour, the
mixture was placed in 25 ml Teflon-lined reactor and heated
at 160 8C in an oven for 3 d, cooling slowly to room
temperature and the pink column crystals of the title
complex suitable to X-ray diffraction analysis were obtained.
Tb2(phth)2(Hphth)2(phen)2(H2O)4 (1408.78) Anal. found: C,
47.96; H, 2.77; N, 4.09%. Calcd: C, 47.72; H, 2.98; N, 3.98%.
IR spectrum exhibits a complicated pattern of bands in the
Additional materials available from the Cambridge
Crystallographic Data Center comprise complete lists of
Table 2
Atomic coordinates (104) of equivalent isotropic displacement parameters
4
(10 A ) for the title complex
2
˚
Atom
x
y
z
UðeqÞ
range 4000–400 cm21
1543.2 cm21 (vasCOO–).
:
1413.7 cm21 (vsCOO–),
Tb(1)
N(1)
2513(1)
1516(4)
3861(4)
4973(4)
3526(4)
3075(3)
3780(3)
4292(1)
2126(4)
3557(4)
1180(1)
1864(3)
3015(3)
2208(3)
931(3)
22(1)
28(1)
30(1)
56(1)
53(1)
48(1)
36(1)
29(1)
29(1)
31(1)
47(1)
39(1)
36(1)
36(1)
28(1)
39(1)
50(2)
54(2)
39(1)
26(1)
30(1)
24(1)
25(1)
34(1)
47(2)
46(2)
38(1)
28(1)
30(1)
38(1)
49(2)
54(2)
41(1)
31(1)
31(1)
40(1)
55(2)
56(2)
51(2)
N(2)
O(1)
21905(3)
21202(3)
780(3)
2.2. X-ray crystallography
X-ray diffraction data for
dimensions 0.15 £ 0.10 £ 0.05 mm3 was performed with
Table 1
O(2)
O(3)
228(3)
a
crystal with
O(4)
2815(3)
5484(3)
6480(3)
4464(3)
5456(4)
6287(4)
5725(4)
21030(5)
301(4)
666(3)
O(5)
22857(3)
2869(3)
339(3)
851(3)
O(6)
508(3)
O(7)
1699(3)
2867(3)
522(4)
Crystal data and structure refinement for the title complex
O(8)
2154(3)
1922(4)
4600(4)
4618(5)
5510(5)
6766(5)
7736(5)
7495(5)
6255(5)
5239(4)
3949(5)
21651(4)
21186(4)
21976(5)
21597(5)
2437(5)
373(5)
O(9)
Complex
Tb2(phth)2(Hphth)2(phen)2(H2O)4
O(10)
C(1)
1380(3)
1677(4)
1885(4)
2552(4)
2802(5)
2367(5)
1720(4)
1461(4)
732(4)
Formula
C56H42N4O20Tb2
1408.78
Pink
C(2)
Relative molecular weight M
Colour
C(3)
294(5)
C(4)
1377(5)
2495(5)
2534(5)
1460(4)
1706(5)
6050(4)
6277(4)
6885(5)
7182(5)
6884(5)
6293(5)
5973(4)
5248(5)
1392(5)
126(5)
Temperature (K)
˚
Wavelength (A)
293(2)
C(5)
0.71073
Mo Ka
P-1
C(6)
Radiation
C(7)
Crystal system
Space group
Unit dimensions
C(8)
Triclinic
C(9)
1195(4)
2460(4)
3037(4)
4190(5)
4776(4)
4215(4)
3055(4)
2508(4)
1281(4)
1522(5)
2425(5)
3088(5)
2766(4)
3384(4)
4348(4)
4685(5)
4089(5)
4945(4)
˚
a ¼ 10:149ð5Þ A, b ¼ 10:730ð5Þ
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
˚
˚
A, c ¼ 11:906ð5Þ A, b ¼ 99:474ð6Þ8
3
˚
Volume (A )
1253.9(10)
Z
1
Calculated density (Mg/m3)
Absorption coefficient (mm21
Fð000Þ
1.866
)
2.887
17(4)
696
890(5)
Crystal size (mm23
)
0.15 £ 0.10 £ 0.05
1.74–25.00
410(5)
Q range for data collection (8)
Reflections/collected/unique
Completeness to 2Q ¼ 26:00 (%)
Absorption correction
253(5)
636(6)
5268/4340 ½RðintÞ ¼ 0:0227ꢀ
98.6
2377(5)
363(5)
1772(5)
2205(5)
3435(5)
4139(5)
3618(6)
2522(6)
5310(6)
None
1604(4)
2385(5)
1892(5)
659(6)
Max. and min. transmission
Refinement method
0.8691 and 0.6713
Full-matrix least-squares on F2
4340/5/386
Data/restraints/parameters
Goodness-of-fit on F2
0.931
294(6)
2674(6)
Final R indices ½I . 2sðIÞꢀ
R1 ¼ 0:0308; wR2 ¼ 0:0606
0.973 and 21.068
23
˚
Largest diff. peak and hole (e A
)
UðeqÞ is defined as one third of the trace of the orthogonalized Uij tensor.

B. Yan et al. / Journal of Molecular Structure 694 (2004) 115–120
117
Fig. 1. The ORTEP drawing for Tb2(phth)2(Hphth)2(phen)2(H2O)4.
˚
atomic coordinates, thermal parameters and bond lengths
and angles (No: CCDC-224013).
and 2.342(4) A for Tb(1)–O(10), respectively. One terminal
phen provides the two nitrogen atoms chelated to Tb ion
˚
whose bond distances are 2.546(4) and 2.593(4) A,
respectively. The bond angle consisting of Tb and the
oxygen atoms from bridging phth molecules ranges in
52.95(10)–53.38(10)8; the bond angle consisting of Tb and
two nitrogen atoms is 63.86(12)8. The Tb(III)–Tb(III)
2.3. Physical measurements
Elemental analyses (C, H, N) were determined on an
Elementar Cario EL elemental analyzer. Infrared
spectroscopy on KBr pellets was performed on a Nexus
912 AO446 FT-IR spectrophotometer in the range of
4000–400 cm21. Excitation and emission spectra for the
solid sample of the title complex were measured with
a Perkin–Elmer LS-55 model spectrophotometer at room
temperature and 77 K.
˚
distance in the dimeric unit is determined to be 4.587 A.
Table 3
˚
Selected bond distances (A) and bond angles (8) for the title complex
Tb(1)–O(4)
Tb(1)–O(6)#1
Tb(1)–O(7)
Tb(1)–O(8)
2.360(3) Tb(1)–O(9)
2.418(3) Tb(1)–O(5)#1
2.426(3) Tb(1)–N(1)
2.470(3) Tb(1)–N(2)
2.433(4)
2.507(3)
2.546(4)
2.593(4)
3. Results and discussion
O(10)–Tb(1)–O(4)
O(10)–Tb(1)–O(6)#l
O(4)–Tb(1)–O(6)#1
O(10)–Tb(1)–O(7)
O(4)–Tb(1)–O(7)
O(6)#1–Tb(1)–O(7)
O(10)–Tb(1)–O(9)
O(4)–Tb(1)–O(9)
O(6)#1–Tb(1)–O(9)
O(7)–Tb(1)–O(9)
O(10)–Tb(1)–O(8)
O(4)–Tb(1)–O(8)
O(6)#1–Tb(1)–O(8)
O(7)–Tb(1)–O(8)
O(9)–Tb(1)–O(8)
O(10)–Tb(1)–O(5)#l
O(4)–Tb(1)–O(5)#1
O(6)#1–Tb(1)–O(5)#1
O(7)–Tb(1)–O(5)#1
O(9)–Tb(1)–O(5)#1
O(8)–Tb(1)–O(5)#1
O(10)–Tb(1)–N(1)
O(4)–Tb(1)–N(1)
0(6)#1–Tb(1)–N(1)
83.97(14) O(7)–Tb(1)–N(1)
130.31(12) O(9)–Tb(1)–N(1)
86.74(11) O(8)–Tb(1)–N(1)
73.44(11)
142.82(13)
93.75(13)
3.1. Description of the crystal structures
131.99(13) O(5)#1–Tb(1)–N(1) 119.77(11)
142.98(11) O(10)–Tb(1)–N(2)
75.81(11) O(4)–Tb(1)–N(2)
77.79(13)
71.08(11)
Final atomic coordinates for non-hydrogen
atoms are listed in Table 2. The ORTEP drawing of
Tb2(phth)2(Hphth)2(phen)2(H2O)4 complex together with
some selected bond parameters, is shown in Fig. 1. The title
Complex crystallizes in the triclinic system, with space
group P-1: The two Tb ions are both equivalent in the same
coordination environment and so only one type of
metal configuration. Each central Tb ion belongs to be
nine-coordinated, whose coordination geometry can be
described as a distorted square monoantiprism geometry.
Among four oxygen atoms are from the two bridged phth
groups (for Tb(1) ion, O(5), O(6) for one bridged phth and
O(7), O(8) for the other bridged phth) with the bond
75.35(14) O(6)#1–Tb(1)–N(2) 142.89(11)
138.34(13) O(7)–Tb(1)–N(2)
80.13(13) O(9)–Tb(1)–N(2)
70.91(12) O(8)–Tb(1)–N(2)
104.21(12)
135.81(13)
70.02(12)
84.90(13) O(5)#1–Tb(1)–N(2) 135.09(11)
140.96(11) N(1)–Tb(1)–N(2)
127.77(11) C(17)–N(1)–Tb(1)
53.38(10) C(21)–N(1)–Tb(1)
73.21(14) C(28)–N(2)–Tb(1)
78.31(12) C(22)–N(2)–Tb(1)
69.05(11) C(8)–O(4)–Tb(1)
52.95(10) C(9)–O(5)–Tb(1)#1
120.02(10) C(9)–O(6)–Tb(1)#1
71.53(12) C(16)–O(7)–Tb(1)
143.73(12) C(16)–O(8)–Tb(1)
139.38(13) O(7)–C(16)–Tb(1)
71.79(12) 0(8)–C(16)–Tb(1)
63.86(12)
121.7(3)
120.7(3)
123.2(3)
119.1(3)
145.5(3)
90.7(3)
94.8(3)
92.7(3)
˚
distances of 2.418(3)–2.507(3) A between the Tb ion and
90.5(3)
oxygen atoms, and one oxygen atom is from the chelated
Hphth group (O(4) for Tb(1)), whose bond distance is
˚
shorter, 2.360(3) A. Besides this, there exist another two
coordinated oxygen atoms from the two water molecules
60.6(2)
62.6(2)
81.32(11) C(15)–C(16)–Tb(1) 168.4(3)
Symmetry transformations used to generate equivalent atoms: #1 2x þ
2; y; 2z þ 3=2; #2 2x þ 2; 2y; 2z þ 2; #3 x; 2y; z 2 1=2:
˚
(O(9) and O(10) for ion) with 2.433(4) A for Tb(1)–O(9)

118
B. Yan et al. / Journal of Molecular Structure 694 (2004) 115–120
of the coordinated water molecules in the adjacent molecular
unit, the other is the O· · ·H–O between the oxygen atom of
bridged phth group and the oxygen atom of coordinated
Hphth group in adjacent molecular unit. Such intermolecular
hydrogen bonding links up the complex units, which results
in a 3D network and leads the whole network structure
system stable.
Scheme 1. Coordination modes of phthalate groups in the title complex.
3.2. Photophysical properties
The ultraviolet absorption spectrum of Tb2(phth)2
(Hphth)2(phen)2(H2O)4 (1024 mol l21 water solution)
(Fig. 3) shows a broad band centered at around 242 nm
and a strong shoulder band at 267 nm in the short ultraviolet
region within the range of 200–280 nm, which can be
attributed to the characteristic absorption of phth group and
phen ligand, respectively. The solid-state excitation spec-
trum of the title complex show the effective energy
absorption mainly in ultraviolet region of 200–350 nm,
and five main excitation peaks appear under the emission of
545 nm: 222, 243, 258, 284 and 332 nm, respectively. We
further measured the corresponding emission spectra by
selectively excitation with the five different excitation
wavelengths, and they show the similar emission position
except for little distinction of luminescent intensities. Which
indicate that the four excitation bands are all the effective
energy excitation for the luminescence of Tb3þ ions.
Selected bond distances and bond angles for the dinuclear
terbium coordination polymer are listed in Table 3.
Two types of coordination modes of Hphth ligands exist
in the molecular structure of the dinuclear complex:
(1) bidentates bridging, the phth anions are completely
deprotonated and all the oxygen atoms take part in the
coordination to the two central metal ion and Tb ions are
connected into dinuclear structure by this coordination
mode (Scheme 1(a)); (2) monodentate chelation, the Hphth
anions merely lost one proton and the undeprotonated
carboxylic acid group provides one carbonyl oxygen atom
coordinated with Tb ion (Scheme 1(b)).
The unit cell (Fig. 2) packing consisting four dinulear
molecular units indicates that the bridged phth groups form
two types of intermolecular hydrogen bonds: one is the
O· · ·H–O intermolecular hydrogen bonding between the
oxygen atom of the bridged phth ligands and the oxygen atom
Fig. 2. Packing view of the unit cell for Tb2(phth)2(Hphth)2(phen)2(H2O)4.

B. Yan et al. / Journal of Molecular Structure 694 (2004) 115–120
119
Fig. 3. The excitation spectrum of Tb2(phth)2(Hphth)2(phen)2(H2O)4.
Fig. 5. The emission spectrum of Tb2(phth)2(Hphth)2(phen)2(H2O)4.
Fig. 4 (A) and (B) give the emission spectrum of
Tb2(phth)2(Hphth)2(phen)2(H2O)4 under the excitation of
243 nm (A) and 284 nm (B), respectively. Both of the
strong green luminescence with four emission bands are at
490.5 (491.5), 545, 583 and 621 nm, respectively,
corresponding to the characteristic emission originated
7
is little stronger than that from 5D4 ! F5 transition for
terbium complex with DAPA, while the emission band to
7
the 5D4 ! F5 transition is much stronger than that to
7
5D4 ! F6 transition for the title dimeric terbium com-
plex. The reason may be due to that the emission to the
3þ
7
from the 5D4 ! Fj (j ¼ 6; 5, 4, 3) transitions of Tb
7
5D4 ! F6 is an electronic dipole transition, which is
7
ion. Among the 5D4 ! F5 transition exhibits the
greatly influenced by the ligand field, different from that
7
strongest green emission, and 5D4 ! F6 transition
7
the emission to the 5D4 ! F5 belonging to a magnetic
shows the second strongest blue emission. We further
measured the low temperature luminescence spectrum of
the terbium dimer at 77 K and it still showed the green
emission of terbium ions, at around 490.5 (491.5), 545.5
(551), 584 (586) and 621 nm, respectively (as shown in
Fig. 5). The splits observed in the emission bands
dipole transition, which is less influenced by the ligand
field [30].
The lowest triplet state energies of phth and phen have
been determined to be around 24,755 and 22,075 cm21
,
respectively [31,32]. The energy differences between the
lowest triplet state energy of them and the resonant emissive
energy level of Tb3þ (20,500 cm21) can be calculated to be
4255 and 1575 cm21, respectively. According to the energy
transfer and intramolecular energy transfer mechanism in
lanthanide complexes [32–35], intramolecular energy
transfer efficiency depends chiefly on two energy transfer
processes: the first one leads from the triplet level of ligands
to the emissive energy level of the Ln3þ ion by Dexter’s
resonant exchange interaction [36]; the second one is just an
inverse energy transfer by a thermal deactivation
mechanism [37]. Both energy transfer rate constants depend
on the energy differences between the triplet level of the
ligands and the resonant emissive energy of Ln3þ. Based on
this evidence, the conclusion can be drawn that energy
differences is of opposite influence on the two energy
transfer processes and an optimal value can be assumed to
exist. So, it can be predicted that the triplet state energy of
phth is more suitable for the luminescence of terbium ion
than phen and phth is the main energy donor for the
7
7
7
corresponded to 5D4 ! F6; 5D4 ! F5; 5D4 ! F4 are
2, 2, 2, separately, which is attributed to the crystal field
splitting. Compared with the luminescence for mono-
nuclear terbium complex with 6-diphenylamine
carbonyl 2-pyridine carboxylate (DPAP), the emission
7
from the 5D4 ! F6 transition for Tb dimer shows no
different split, which suggests that the two terbium ions
are in the same coordination environment in the dimer
5
7
[30]. Besides this, the emission from D4 ! F6 transition
luminescence of Tb3þ
.
4. Conclusions
In summary, assembling hybrid ligands of phth, phen and
H2O, a novel quaternary dinuclear terbium complex has
Fig. 4. The emission spectrum of Tb2(phth)2(Hphth)2(phen)2(H2O)4.

120
B. Yan et al. / Journal of Molecular Structure 694 (2004) 115–120
[14] S.S.Y. Chui, A. Siu, X. Feng, Z.Y. Zhang, T.C.W. Mak, I.D.
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[15] A. Fernandes, J. Jaud, G.J. Dexpert, C.C. Brouca, Polyhedron 20
(2001) 2385.
been synthesized by hydrothermal process. The terbium
complex shows a dimer through the bridged phth
and the Tb(III)–Tb(III) distance is determined to be
˚
4.587 A. The dimer exhibits strong green luminescence of
´
[16] J.C. Trombe, S. Romero, Solid. State. Sci. 2 (2002) 279.
Tb3þ and phth belongs to the effective sensitizer and
[17] H.T. Xu, N.W. Zheng, X.L. Jin, R.Y. Yang, Y.G. Wu, E.Y. Ye,
Z.Q. Li, J. Mol. Struct. 655 (2003) 339.
becomes the main energy donor for Tb3þ
.
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