An organically templated open-framework cobalt germanate

Article abstract of DOI:10.1016/S0022-4596(02)00048-8

An open-framework cobalt germanate of the formula, [Co₂(NH₂(CH₂)₂NH₂) ₃][Ge₉O₁₈(OH)₄] has been prepared under solvo/hydrothermal conditions in the presence of ethylenediamine. The germanate is constructed by Ge₉O₁₈ clusters and contains eight- and ten-membered channels. Besides connecting two Co sites, the amine also acts as a bis-chelating agent and protrudes into the eight-membered channel.

Full text of DOI:10.1016/S0022-4596(02)00048-8

Journal of Solid State Chemistry 170 (2003) 124–129
An organically templated open-framework cobalt germanate
Njapba Ngu Julius, Amitava Choudhury, and C.N.R. Rao*
Chemistry and Physics of Materials Unit, CSIR Center of Excellence in Chemistry, Jawaharlal Nehru Centre for Advanced Scientific Research,
Jakkur P.O., Bangalore 560 064, India
Received 20 May 2002; received in revised form 5 August 2002; accepted 27 August 2002
Abstract
An open-framework cobalt germanate of the formula, [Co
2
(NH
2
(CH
2
)
2
NH
2
)
3
][Ge
9
O
hydrothermal conditions in the presence of ethylenediamine. The germanate is constructed by Ge
18(OH)
4
] has been prepared under solvo/
18 clusters and contains eight-
9
O
and ten-membered channels. Besides connecting two Co sites, the amine also acts as a bis-chelating agent and protrudes into the
eight-membered channel.
r 2002 Elsevier Science (USA). All rights reserved.
1
. Introduction
NH ) ][Ge O (OH) ], I, under solvo/hydrothermal
2 3 9 18 4
conditions. While the structure of I is analogous to that
of the zinc germanate of Stucky et al. [12], it has certain
novel features, a noteworthy one being the presence of
the cobalt amine complex in the eight-membered
channel.
Germanate-based zeolite structures containing
Ge O have attracted much attention [1]. The Ge–O–
8
20
ꢀ
Ge angles in these compounds are around 130 in place
ꢀ
of the 145 Al–O–Si angle in the aluminosilicates.
Various zeolitic open germanates have been reported
by several workers including Xu et al. [2], Stucky et al.
[
3], Dadachov et al. [4], Zhao et al. [5], Yaghi et al. [6]
2. Experimental
and Puebla et al. [7]. Several layered open germanates
have also been reported, typical examples being a zinc
germanate by Parise et al. [8], a copper germanate by
The cobalt germanate, [Co (NH (CH ) NH ) ]
2 3
2
2
2 2
[
Ge O (OH) ], I, was synthesized by employing solvo/
9 18 4
Monge et al. [9], K ZrGe O by Clearfield et al. [10] and
2
2
7
hydrothermal route using ethylenediamine (en)/water
mixture. In a typical synthesis, 0.109 g of germanium
dioxide and 0.238 g of cobalt chloride were dissolved in
2.0 ml en and 1.0 ml water. 0.258 g of piperazine (PIP)
was then added and the mixture stirred continuously for
K Nb GeO ꢁ 2H O by Stucky et al. [11]. Stucky
3
5
16
2
et al. [12] have recently reported an open-framework
zinc germanate of the type [Ge O Zn (OH) ] ꢁ
9
18
2
4
3
while Yaghi et al. [13] have described a four-connected
(NH CH CH NH ) by molecular templating route
2 2 2 2
1
h. Finally, 0.1 ml of HF (48%, w/w aqueous solution)
6
microporous material of the composition ZrO F2
was added and the resulting dark brown solution
homogenized for 30 min. The final mixture with the
composition GeO :CoCl ꢁ 6H O:30en:55H O:3PIP:2.7
(
H DAB) ꢁ H O containing a high proportion of 3-rings.
2
2
Jacobson et al. [14,15] have synthesized organically
templated open-framework niobium germanates with
low framework density and ion-exchange properties.
Puebla et al. [16] have obtained germanates containing
transitional metal complexes with potential uses in
catalysis. We have synthesized an organically templated
2
2
2
2
HF with an initial pH greater than 11, was sealed in a
ꢀ
teflon-lined Parr autoclave and heated at 180 for 10
days. The autoclave was then allowed to cool for a
period of 4 h. The pH of the supernatant solution was
around 9. The resulting product, containing pink-
coloured rod-shaped crystals suitable for single-crystal
X-ray diffraction (XRD), was filtered and washed
thoroughly with deionized water. The yield was B55%
with respect to Ge. The role of PIP is probably to fine
cobalt germanate of the formula [Co (NH (CH )
2 2
2
2
*Corresponding author. Fax: +0091-80-846-2766.
E-mail address: cnrrao@jncasr.ac.in (C.N.R. Rao).
0022-4596/03/$ - see front matter r 2002 Elsevier Science (USA). All rights reserved.
PII: S 0 0 2 2 - 4 5 9 6 ( 0 2 ) 0 0 0 4 8 - 8

N.N. Julius et al. / Journal of Solid State Chemistry 170 (2003) 124–129
125
tune the pH of the medium which helps to form
monophasic material. Without the addition of PIP in
the reaction mixture, a colourless impurity phase also
appears along with I. Qualitative analysis indicated the
absence of F in the product. Synthesis carried out
without HF also yields I in powder form. So the role of
HF could be just a mineralizer.
polarizing microscope and glued to a thin glass fiber
with cyanoacrylate (superglue) adhesive. Crystal struc-
ture determination by X-ray diffraction was performed
on a Siemens Smart-CCD diffractometer equipped with
a normal focus, 2.4 kW sealed tube X-ray source (MoKa
(
radiation, l ¼ 0:71073 A) operating at 50 kV and 40 mA.
A hemisphere of intensity data were collected at room
ꢀ
The powder XRD pattern of the powdered single
crystals of I indicated that the product was a new
material. The pattern was consistent with the structure
determined by single-crystal XRD. A least-squares
fit [17] of the powder XRD (CuKa) lines, using the
h k l indices garnered from single-crystal X-ray data,
gave the following cell: a ¼ 14:022ð3Þ; b ¼ 12:972ð3Þ;
temperature in 1321 frames with o scans (width of 0.30
and exposure time of 20 s per frame). The final unit cell
constants were determined by a least-squares fit of 1931
ꢀ
ꢀ
reflections in the range 3 o2yo46:5 : Pertinent experi-
mental details for the structure determinations are
presented in Table 2.
The structure was solved by direct methods using
SHELXS-86 [18] and difference Fourier syntheses. The
hydrogen positions for bridging hydroxide (O8) and
terminal hydroxyl (O11) were initially located in the
difference Fourier maps and for the final refinement, the
hydrogen atoms were placed geometrically and held in
the riding mode. The hydrogen atoms for the bonded
amine molecules were not put for the final refinement
because of disorder in one of the carbon, C1 (SOF of C1
and C1A are 0.30 and 0.70, respectively) and nitrogen,
N3 (SOF of N3 and N3A are 0.70 and 0.30, respectively)
sites. The last cycles of refinement included atomic
positions for all the atoms, anisotropic thermal para-
meters for all non-hydrogen atoms (except the
(
c ¼ 14:665ð1Þ A, which is in good agreement with that
determined by single-crystal XRD. Powder XRD data
for I, [Co (NH (CH ) NH ) ][Ge O (OH) ], are listed
2
2
2 2
2 3
9
18
4
in Table 1. EDAX analysis indicated that the ratio of
Co:Ge is 2:9. Thermogravimetric analysis (TGA) was
carried out under nitrogen atmosphere in the range from
ꢀ ꢀ
2
5 to 1000 C.
3
A suitable single crystal (0.08 Â 0.08 Â 0.20 mm ) of
the title compound was carefully selected under a
Table 1
X-ray powder data for [Co
2
(NH
2
2
(CH )
2
NH
2
)
3
][Ge
9
O
18(OH)
4
]
a
b
c
h
k
l
2yobs
Dð2yÞ
dcal
DðdÞ
Irel
1
0
2
1
0
2
1
0
2
1
2
1
1
2
3
2
4
3
2
2
4
3
5
1
0
4
6
3
0
6
1
0
0
0
2
1
2
2
2
1
2
3
3
3
1
0
0
2
4
2
2
3
2
5
0
2
0
3
0
3
1
2
0
2
0
1
1
2
1
3
2
1
2
2
3
4
2
3
0
4
2
3
1
1
6
4
0
5
8
4
11.099
12.108
12.634
13.597
13.678
15.612
16.245
18.284
19.601
20.423
22.268
22.393
24.772
27.112
27.29
0.004
7.987
7.332
7.013
6.498
6.486
5.686
5.463
4.858
4.529
4.349
3.993
3.977
3.6
À0.003
À0.013
0.003
0.022
À0.005
À0.004
À0.001
À0.002
0.004
0.003
0.002
À0.004
À0.004
0.002
0
100.00
56.45
71.39
11.89
66.51
19.78
39.02
7.20
Table 2
0.021
À0.005
À0.047
0.009
2 2
Crystal data and structure refinement parameters for [Co (NH
(
CH
2
)
2
NH
2
)
3
][Ge
9
O
18(OH)
4
], I
Emperical formula
Space group
T (K)
2 9 22 6 6 28
Co Ge O N C H
0.011
0.004
0.006
Pbca
293
(
a (A)
(
b (A)
14.039(3)
12.987(2)
14.705(4)
90.0
À0.017
À0.015
À0.009
0.023
6.86
(
c (A)
12.30
46.50
22.21
17.24
19.75
23.78
28.28
13.71
9.74
a (deg)
b (deg)
g (deg)
Volume (A )
Z
90.0
90.0
0.023
(
3
À0.013
À0.002
0.025
3.289
3.27
2681.1(11)
8
27.493
28.246
29.816
30.376
30.801
31.476
33.662
35.387
35.732
36.816
38.142
38.56
3.249
3.163
2.996
2.943
2.905
2.843
2.662
2.536
2.513
2.444
2.36
À0.003
À0.002
0.002
0.001
À0.001
0.001
0.002
0.002
0.001
À0.002
0
Formula mass
À3
1307.52
3.239
0.019
rcalc (g cm
)
(
À0.017
À0.007
0.005
l (MoKa) A
0.71073
11.243
1.55–23.28
10451
À1
10.08
25.27
27.35
42.43
5.49
m (mm
)
y range (deg)
Total data collected
À0.006
À0.018
À0.026
À0.009
0.028
Index ranges
Unique data
À14php15,À11pkp14,À11plp16
1930
1557
18.04
18.77
15.40
10.37
5.96
Observed data (s42s(I))
Refinement method
R indices [I42sðIÞ]
R indices (all data)
Goodness of fit (S)
No. of variables
2
Full-matrix least-squares on |F |
R1¼ 0:0510; wR2 ¼ 0:1524
À0.002
0.031
0.001
a
2.338
2.154
1.833
1.793
À0.002
0
R1¼ 0:0666; wR2 ¼ 0:1640
41.955
49.731
50.955
1.039
204
À0.024
0.023
0.001
0
8.67
5.91
Largest difference mappeak
À3
1.060 and À2.652
(
and hole e A
a
b
c
2
y
obsÀ2ycalc
.
a
2
2
) +(0.0894P) +98.2020P] where P=[F
2
2
o
2
c
d
obsÀdcalc
.
W=1/[s (F
o
+2F
]/3.
1
00 Â I/Imax
.

126
N.N. Julius et al. / Journal of Solid State Chemistry 170 (2003) 124–129
Table 3
Table 5
4
Atomic coordinates ( Â 10 ) and equivalent isotropic displacement
2 2 2 2 2 3 9 4
Selected bond angles in Co (NH (CH ) NH ) [Ge O18(OH) ]
(
2
3
parameters (A Â 10 ) for [Co
2 2 2 2 2 3 9 4
(NH (CH ) NH ) ][Ge O18(OH) ], I
Moiety
Angle (deg) Moiety
Angle (deg)
a
x
y
z
U (eq)
a
O(5) –Ge(4)–O(10)
O(2)–Ge(1)–O(1)
O(2)–Ge(1)–O(3)
O(1)–Ge(1)–O(3)
O(2)–Ge(1)–O(4)
O(1)–Ge(1)–O(4)
O(3)–Ge(1)–O(4)
O(5)–Ge(2)–O(6)
O(5)–Ge(2)–O(7)
O(6)–Ge(2)–O(7)
O(5)–Ge(2)–O(3)
O(6)–Ge(2)–O(3)
O(7)–Ge(2)–O(3)
O(7)–Ge(3)–O(8)
O(7)–Ge(3)–O(9)
O(8)–Ge(3)–O(9)
O(7)–Ge(3)–O(2)
O(8)–Ge(3)–O(2)
O(9)–Ge(3)–O(2)
106.6(4)
109.4(4)
109.9(4)
108.8(4)
113.2(4)
108.9(4)
105.7(4)
104.9(4)
111.5(4)
113.8(4)
108.1(4)
112.7(5)
119.4(5)
122.2(5)
117.3(5)
90.2(4)
170.5(4)
180
b
Ge(1)
Ge(2)
Ge(3)
Ge(4)
Ge(5)
Co(1)
O(1)
5236(1)
6668(1)
5049(1)
3706(1)
5000
1758(1)
1602(1)
2210(1)
2333(1)
0
6446(1)
4875(1)
3518(1)
4994(1)
5000
9(1)
9(1)
O(6)–Ge(5)–O(6)
O(6)–Ge(5)–O(1)
b
O(6) –Ge(5)–O(1)
b
89.4(4)
90.6(4)
90.6(4)
89.4(4)
179.999(1)
90.9(4)
89.1(4)
88.5(4)
91.5(4)
89.1(4)
90.9(4)
91.5(4)
88.5(4)
b
10(1)
10(1)
8(1)
O(6)–Ge(5)–O(1)
b
O(6) –Ge(5)–O(1)
b
O(1) –Ge(5)–O(1)
3703(2)
5031(6)
5341(7)
6311(6)
4302(6)
7900(6)
6293(6)
6231(6)
4724(7)
4113(7)
4693(6)
2778(7)
2950(13)
2233(18)
2670(9)
5378(15)
2476(14)
2127(13)
4951(15)
4425(10)
3931(2)
465(7)
6584(2)
6220(6)
7606(6)
5926(6)
6071(6)
4721(6)
4861(6)
3930(6)
2787(6)
3975(6)
4637(6)
5002(7)
45(1)
10(2)
14(2)
14(2)
12(2)
12(2)
11(2)
17(2)
16(2)
18(2)
9(2)
b
O(6)–Ge(5)–O(10)
b
O(6) –Ge(5)–O(10)
b
b
O(2)
O(3)
1868(7)
2155(7)
2569(7)
1567(7)
317(7)
b
O(1) –Ge(5)–O(10)
b
O(4)
O(5)
O(1)–Ge(5)–O(10)
O(6)–Ge(5)–O(10)
b
O(6) –Ge(5)–O(10)
O(6)
O(7)
b
O(1) –Ge(5)–O(10)
2286(8)
1184(7)
2972(7)
1365(6)
1424(8)
5409(12)
4231(19)
3359(10)
4736(18)
5197(16)
5204(13)
4777(15)
4980(14)
O(8)
O(9)
O(1)–Ge(5)–O(10)
b
O(10) –Ge(5)–O(10) 180
c
c
c
O(10)
O(11)
N(1)
C(2)
96.0(4)
94.5(4)
O(4)–Co(1)–N(2)
O(4)–Co(1)–N(3)
N(2)–Co(1)–N(3)
O(4)–Co(1)–N(1)
N(2)–Co(1)–N(1)
N(3)–Co(1)–N(1)
101.8(5)
19(2)
48(4)
66(7)
27(3)
61(6)
31(13)
49(7)
23(4)
36(12)
90.9(6)
155.0(6)
168.6(5)
82.3(6)
89.4(7)
88.4(3)
85.6(4)
73.2(6)
102.6(5)
70.2(3)
95.0(4)
109.7(6)
99.0(5)
158.3(4)
6853(11)
7949(15)
7484(9)
O(7)–Ge(3)–O(10)
O(8)–Ge(3)–O(10)
O(9)–Ge(3)–O(10)
89.1(4)
91.3(4)
79.2(4)
N(2)
C(3)
c
5240(18)
7863(14)
7396(11)
6223(13)
6233(14)
O(2) –Ge(3)–O(10) 172.1(4)
O(11)–Ge(4)–O(9) 123.3(5)
O(11)–Ge(4)–O(4) 116.7(4)
d
C(1)
O(4)–Co(1)–O(8)
N(2)–Co(1)–O(8)
N(3)–Co(1)–O(8)
N(1)–Co(1)–O(8)
d
d
d
C(1A)
N(3)
N(3A)
O(9)–Ge(4)–O(4)
O(11)–Ge(4)–O(5)
120.0(5)
93.7(4)
91.5(4)
87.4(4)
a
a
d
d
O(9)–Ge(4)–O(5)
O(4)–Co(1)–O(5)
a
U(eq) is defined as one-third of the trace of the orthogonalized Uij
a
O(4)–Ge(4)–O(5)
N(2)–Co(1)–O(5)
N(3)–Co(1)–O(5)
N(1)–Co(1)–O(5)
tensor.
d
a
O(11)–Ge(4)–O(10) 95.5(4)
O(9)–Ge(4)–O(10)
O(4)–Ge(4)–O(10)
81.2(4)
90.9(4)
Table 4
d
a
O(8) –Co(1)–O(5)
Selected bond distances in [Co
2
(NH
2
(CH
Moiety
Ge(4)–O(5)
2
)
2
NH
2
)
3
][Ge
9
O
18(OH)
4
], I.
Symmetry transformations used to generate equivalent atoms:
a
(
Distance (A)
(
Distance (A)
Moiety
xÀ1/2, Ày+1/2, Àz+1.
b
a
Àx þ 1; Ày; Àz þ 1:
Ge(1)–O(2)
Ge(1)–O(1)
Ge(1)–O(3)
Ge(1)–O(4)
Ge(2)–O(5)
Ge(2)–O(6)
Ge(2)–O(7)
Ge(2)–O(3)
Ge(3)–O(7)
Ge(3)–O(8)
Ge(3)–O(9)
Ge(3)–O(2)
1.718(9)
1.735(9)
1.769(9)
1.771(8)
1.745(9)
1.750(9)
1.760(9)
1.775(9)
1.769(9)
1.771(9)
1.776(9)
1.845(9)
2.039(9)
1.758(10)
1.806(9)
1.817(9)
1.870(9)
1.944(8)
1.873(8)
1.873(8)
1.893(9)
1.893(9)
1.901(8)
1.901(8)
1.77(5)
c
x; Ày þ 1=2; zÀ1=2:
Ge(4)–O(10)
Ge(5)–O(6)
d
x; Ày þ 1=2; z þ 1=2:
b
Ge(5)–O(6)
b
Ge(5)–O(1)
Ge(5)–O(1)
Ge(5)–O(10)
Ge(5)–O(10)
b
disordered atoms) and isotropic thermal parameters for
all the hydrogen atoms. Full-matrix least-squares
2
refinement against |F | was carried out using the
SHELXTL-PLUS [19] suit of programs. Details of the
final refinements are given in Table 2. The final atomic
coordinates, selected bond distances and bond angles
are given for I in Tables 3–5.
Co(1)–N(3A)
Co(1)–O(4)
Co(1)–N(2)
Co(1)–N(3)
Co(1)–N(1)
2.099(9)
2.100(13)
2.13(2)
c
Ge(3)–O(10)
Ge(4)–O(11)
Ge(4)–O(9)
Ge(4)–O(4)
2.23(2)
2.282(9)
2.318(9)
d
Co(1)–O(8)
Co(1)–O(5)
a
Organic moiety
N(1)–C(1A)
N(1)–C(1)
3. Results and discussion
1.43(3)
1.65(6)
1.31(6)
1.46(3)
C(2)–C(1A)
e
C(3)–C(3)
C(3)–N(3)
1.51(4)
1.45(4)
1.57(3)
The structure of [Co (NH (CH ) NH ) ][Ge O (OH) ],
18
2
2
2 2
2 3
9
4
C(2)–C(1)
C(2)–N(2)
I, is constructed from hour-glass-like Ge clusters. The
9
clusters are connected in such a way as to form intersecting
three-dimensional channels. The Co–en complex is grafted
inside the channel and balances the charge, besides
stabilizing the channel. The structure is analogous to
[Zn Ge O (OH) ] ꢁ 3(NH (CH ) NH ) [12] but with cer-
Symmetry transformations used to generate equivalent atoms:
a
x À 1=2; Ày þ 1=2; Àz þ 1:
b
Àx þ 1; Ày; Àz þ 1:
c
x; Ày þ 1=2; z À 1=2:
d
x; Ày þ 1=2; z þ 1=2:
2
9
18
4
2
2 2
2
e
Àx þ 1; Ày þ 1; Àz þ 1:
tain differences discussed later.

N.N. Julius et al. / Journal of Solid State Chemistry 170 (2003) 124–129
127
Fig. 1. ORTEP plot of I. The asymmetric unit is labeled and thermal ellipsoids given at 50% probability: (a) ball and stick representation of the
hour-glass-like Ge 18 cluster and (b) the T atom (Ge sites) connectivity of the Ge hour-glass-like cluster.
9
O
9
The asymmetric unit of I contains 23 non-hydrogen
atoms, out of which 17 atoms (5 Ge, 1 Co, 11 O) belong
to the inorganic framework and six belongs to the
organic ligand (3 C and 3 N), which constitutes a full
fragment of bis-chelated en and half of end-to-end
connected en (Fig. 1(a)). There is disorder in one of the
C (C1) and N (N3) sites in the chelated and end-to-end
en, respectively. There are five crystallographically
distinct Ge atoms and one Co atom. Ge(1) and Ge(2)
have nearly regular tetrahedral coordination, while
Ge(3) and Ge(4) have slightly distorted trigonal
bipyramidal coordination of oxygen neighbors, one of
them being a terminal –OH group(O11). Ge(5), on the
other hand, is located at the inversion center and adopts
an octahedral coordination. The Ge–O distances in the
molecules. Out of the three Co–O distances, two are
rather long [Co(1)–O(8)=2.282(9), Co(1)–O(5)=
2.318(9)]. One of these (O8) belong to the bridging
hydroxide group. Co–N distances on the other hand are
regular, though one of the nitrogens bonded to Co is
disordered. Bond valence calculations [21] indicate that
all the Ge atoms are in the +4 state while Co is in
the +2 state, giving rise to the formula [Co (NH
2
2
(CH ) NH ) ][Ge O (OH) ].
4
2
2
2 3
9
18
The tetrahedral Ge sites [Ge(1) and Ge(2)] and the
trigonalbipyramidal (tbp) Ge sites [Ge(3) and Ge(4)] are
linked to each other to form a four-membered Ge unit.
4
In the four-membered ring, only the tbpGeO 4(OH)
units are edge-shared between themselves, while rest of
the connectivities are corner-shared. Two such Ge units
4
(
tetrahedral Ge sites are in the range 1.718(9)–1.775(9) A
are linked by the Ge(5)O octahedra and related by an
6
(
(Ge(1)–O) =1.748 and (Ge(2)–O) =1.757 A], for the
[
trigonal bipyramidal Ge sites the range is 1.758(10)–
inversion center, resulting in the hour-glass-like Ge9
cluster building unit as shown in Figs. 1(b) and (c). In
the cluster, the Ge units are connected to the center
av
av
(
.039(9) A [Ge(3/4)–O=1.84 A], and for the octahedral
(
2
site the range is 1.873(3)–1.9011(8) A [avg=1.889 A].
4
(
(
through the utilization of both bi- and tri-connected
oxygens, thereby creating six three-membered rings.
Three-membered rings are characteristic of open-frame-
So the Ge–O distances vary in the order (Ge–O) o
Td
(
Ge–O) o(Ge–O) , which is in general agreement
tbp
Oh
with those observed in similar compounds [6,20]. The
Co site on the other hand adopts a very distorted
octahedral coordination with three framework oxygen
atoms and three nitrogen atoms from two types of en
work germanates [3,13]. In each Ge cluster, excepting
9
the terminal –OH (O11–H) and the bridging –OH
(O8–H) groups, the remaining oxygen atoms at the
corners links to eight neighboring Ge9 cluster, thus

128
N.N. Julius et al. / Journal of Solid State Chemistry 170 (2003) 124–129
be seen from Fig. 3(a). Apart from this, the Co atom is
connected to the framework through O(4), O(5) and
O(8)(–H) oxygens, out of which O(4) and O(5) are
involved in inter- and intra-cluster binding. O(8)H is
only used to solely connect the Co-site. The distorted Co
octahedron partially blocks the channel along the b-axis
as can be seen form Fig. 2(a), while there is reasonable
free space along the [101] and [À101] directions
(Fig. 3(b)). Only Co–O(4) connectivity is strong, while
Co–O(5) and Co–O(8)H connectivities are weak. These
connections are different from those in the Zn-analog
[12]. In the Zn-analog, the O(8)H hydroxyl group
remains terminal to the Ge-site and does not form a
(
bond with Zn (Zn–OH=2.7 A). The presence of the
Co-complex grafted on to the channels of the frame-
Fig. 2. (a) Polyhedral arrangement of the structure of I along the b-
axis, showing the eight-membered channel. Partial blocking of the
eight-membered channel by Co-octahedra is also shown. Amine
molecules are omitted for clarity and (b) T atom (Ge sites) connectivity
showing the openings of the eight- and ten-membered intersecting
channels from different directions.
forming an open-framework structure with intersecting
three-dimensional channels. The long axis of the Ge9
cluster is aligned with the b-axis and create an eight-
membered ring channel as shown in Fig. 2(a), while it
creates a ten-membered channel along [101] and [À101]
directions [Fig. 2(b)].
The Co atom does not participate in the construction
of the framework, but the amine plays a dual role.
Between the two types of en molecules, which bind to
the Co site, one acts as a bis-bidentate chelating agent
and protrudes into the eight-membered channel and the
other connects the two Co sites (one symmetrically
generated) in a end-to-end fashion (Co–N–C–C–N–Co),
acting as a pillar inside the ten-membered channel as can
Fig. 3. (a) The pillaring role of the end-to-end connected en molecule
in the ten-membered tunnel has been shown. Arrow indicates the
complex in the eight-membered channel and (b) T atom (Ge sites)
connectivity in the structure of I along the [101] direction showing the
ten-membered channel. The Co-amine complex has been removed for
clarity.

N.N. Julius et al. / Journal of Solid State Chemistry 170 (2003) 124–129
129
by the solvo/hydrothermal method. The germanate
formed by Ge O clusters has eight- and ten-membered
9
18
channels with the cobalt amine complex protruding in
the eight-membered channels. This germanate may be
considered to be an example of a metal complex-grafted
microporous solid.
Acknowledgments
One of the authors (NNJ) thanks the International
Union of Pure and Applied Chemistry for a travel grant
and the University of Buea, Cameroon for a leave of
absence.
Fig. 4. TGA curve of I.
work in I can be taken as an example of a metal
coordintaion complex-grafted microporous material.
There are other interesting features in I. The hour-
glass-like cluster unit is versatile and has been observed
previously in [Ge O (OH) ][(C N H ) ] ꢁ 2H O (2),
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8
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[
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9
18
4
4
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12 2
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À8
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9
A significant finding is the isolation of individual
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4
4
12
9
14
12
2
20] where all the terminal oxygens are dangling –OH
[
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(
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TGA carried out in flowing nitrogen (commercial
À1
[
[
ꢀ
ꢀ
ꢀ
grade) at a heating rate of 10 C min from 25–1000 C
indicates two major mass loses in the regions 300–400 C
and 720–950 C (Fig. 4). The first stepcorresponds to the
loss of three en molecules and two water molecules
1
ꢀ
’
[13] H. Li, M. Eddaoudi, J. Plevert, M. O Keeffe, O.M. Yaghi,
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[
[
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15] R.J. Francis, A.J. Jacobson, Angew. Chem., Int. Ed. Engl. 40
(
calc.=16.5%, obs.=16.6%), leading to the collapse of
the framework. The second huge mass loss (62%) can
be assigned to the removal of the volatile germanium
oxide phases. Pxrd of the remaining annealed sample
(
2001) 2879.
[
[
16] C. Cascales, E. G-Puebla, M. Iglesias, M.A. Monge, C. R-Valero,
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ꢀ
17] W. Lasocha, K. Luwinski, PROSZKI-A system of programs
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4–0545) and CoO (JCPDS file, card no.: 42–1300).
0
(
1994) 437.
EDAX analysis also showed the presence of Ge and Co
in the annealed product.
[
18] G.M. Sheldrick, ‘‘SHELXS-86 Program for crystal structure
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A 35 (1990) 467.
[
[
[
19] G.M. Sheldrick, SHELXTL-PLUS Program for crystal structure
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4
. Conclusions
The synthesis of an organically templated open-
framework cobalt germanate has been accomplished
21] I.D. Brown, D. Altermatt, Acta Crystallogr. B 41 (1984) 244.
[22] G. Ferey, J. Solid State Chem. 152 (2000) 37.