1
14
J. Fu et al. / Inorganica Chimica Acta 383 (2012) 112–117
occupied and the other six (O22, O23, O24, O22a, O23a, and
O24a) have the same occupied factors of 0.5. The average S–O bond
distance is 1.474 Å, which is comparable to those of similar bonds
reported earlier [11–19].
The structure of 2 can be described as two types of secondary
3
À
building units (SBUs). Two [La
each other by sharing La(1) to form the SBU-1 [La
adjacent SBU-1s are linked by bridging [SO ] tetrahedra to generate
an interesting 20MR structure (Fig. 5). SBU-2 is 10MR. Adjacent 10
3
(SO
4
)
6
]
fragments connect with
9À
5 4 12
(SO ) ] . Two
4
2
À
and 20MRs are connected by bridging SO
4
groups to form an open
framework with a 3D channel system (Fig. S2a). Both 10 and 20MR
channels are arranged in an ordered close packing structure. Each
2
0MR channel is surrounding by six 10MRs, and they are alternately
surroundedby three 20MRs and three 10MRs. The approximate win-
2
dow sizes for 20MR and 10MR are 5.3 Â 9.5 and 3.8 Â 3.8 Å , respec-
tively. Interestingly, there are other rectangular 20MR-r channels
along the crystallographic [101] direction (Fig. S2b). The pore size
Fig. 1. ORTEP view of the [(CH
labeling scheme.
3
2
) NH
2 3
] [Y(SO
4 3 2
) ]ÁH O structure showing the atom
2
of rectangular 20MR is about 2.9 Â 12.8 Å . We used the PLATON
software to calculate the percent void volume in the 3D network of
4
2, and the result is 48.5%. The appearance of disordered SO in both
types of 20MRs leads to different inorganic frameworks and pore
sizes. As shown in Fig. 6, protonated dimethylamine cations and free
water molecules are located in the 10MR and both types of 20MR
channels of the inorganic framework by strong hydrogen bonding
interactions between H atoms of organic amine molecules and O
atoms of the open-framework of 2. The protonated dimethylamine
cations cannot be removed without collapse of framework of 2 and
3. One hundred and twenty six free water molecules in 20MR chan-
nels are connected each other by strong hydrogen bonding to form
an interesting zigzag chain along c axis. The distances between
two adjacent water molecules are 2.86(2) and 2.94(2) Å respectively
(Fig. 6d). Hydrogen bonds for compound 2 are given in Table S3.
3.2. IR spectroscopy
The IR spectrum of compound 1 (Fig. S3) shows that the band at
À1
about 3420 cm
can be assigned to water. The typical sharp
À1
signals for dimethylamine are in the region 1380–1650 cm , and
the characteristic bands of SO
region. The bands at 3213 and 2984 cm are assigned to O–H
2À
À1
4
are in the 1129 and 662 cm
À1
bonding and N–H bonding vibrations, respectively. The band at
À1
6
09 cm can be attributed to the Y–O vibration. The IR spectrum
of compounds 2 and 3 are similar with compound 1 and the spec-
trum are in Figs. S4 and S5.
3
nÀ
Fig. 2. (a) Polyhedra structure of the [Y(SO
O–S–O–] chain; (c) an intertwined [–Y–O–S–O–] double helices of the same
handedness.
4
)
3
]
n
chain in 1; (b) single helical [–Y–
n
3.3. Thermogravimetric analysis
The thermogravimetric analyses (TGA) of complexes 1–3 were
3
.1.2. Crystal structure of 2 and 3
Compounds 2 and 3 are isostructural and crystallize in mono-
performed in a N
2
atmosphere when heated to 1000 °C at a rate
À1
of 10 °C min . For compound 1, total weight loss is 74.1%, which
is in agreement with the calculated value 74.2% (Fig. S6). The
weight loss of 28.3% in the range of 40–330 °C corresponds to the
removal of free water and three dimethylamine molecules (the cal-
culated value is 29.1%). The weight loss of 45.8% in the range of
330–1080 °C can be attributed to the loss of SO
lue is 45.0%). The final product is Y . For compound 2, the total
weight loss is 60.3%, which is in agreement with the calculated va-
lue 61.4% (Fig. S7). The weight loss of 1.9% in the range of 30–
100 °C corresponds to the removal of two free water molecules.
The second step loss of 34.7% in the range of 100–550 °C can be
clinic space group C2/c. We take compound 2 as an example to de-
scribe the structure. Although these two compounds are similar
with our previous work [34,37], it is vital to study their structures.
The asymmetric unit of 2 contains three lanthanum atoms, six sul-
fate groups and five protonated dimethylamine cations (Fig. S1).
The metal atoms La(1) and La(2) are eight-coordinated by O atoms,
while La(3) is nine-coordinated by O atoms. The average bond dis-
tance of La–O is 2.431 Å, whereas the angles of O–La–O are be-
tween 46.1(2) and 166.99(9)°. Six crystallographic independent S
atoms can be divided into four groups: S(3) is bonded by three
3
(the calculated va-
2 3
O
l
2
-O atoms and one Ot (terminal O atom) to generate three S–O–
La linkages; S(2) and S(5) are coordinated by four -O atoms to
form four S–O–La linkages; S(1) and S(4) are bonded by one
O, two -O atoms and one Ot to form four S–O–La linkages; while
S(6) is coordinated by seven O atoms, one of them (O21) is fully
attributed to all the dimethylamine and some of SO
loss of 23.7% in the range of 550–800 °C can be attributed to loss
of SO . The final product is La . The weight loss curve of com-
pound 3 is similar to compound 2 (Fig. S7). The final product is
CeO
3
. The weight
l
2
l
3
-
3
2 3
O
l
2
2
.