Topochemical conversion of a hydrogen-bonded three-dimensional network into a covalently bonded framework

Article abstract of DOI:10.1002/(SICI)1521-3773(19980504)37:8<1114::AID-ANIE1114>3.0.CO;2-E

Thermal dehydration promotes the topochemical conversion of the hydrogen-bonded dimeric complex [{Zn(sala)(H₂O)₂}₂]·2H₂O (H₂-(sala) = N-(2-hydroxybenzyl)-L-alanine) to generate covalent [{Zn(sala)}(n)

Full text of DOI:10.1002/(SICI)1521-3773(19980504)37:8<1114::AID-ANIE1114>3.0.CO;2-E

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Keywords: boron ´ N ligands ´ porphyrinoids
various intermolecular forces, from weak van der Waals
[2, 3]
forces, hydrogen and covalent bonding,
to ionic interac-
tions.[ Most of the reported three-dimensional architectures
4]
[
1] W. J. Belcher, P. D. W. Boyd, P. J. Brothers, M. J. Liddell, C. E. F.
Rickard, J. Am. Chem. Soc. 1994, 116, 8416 ± 8417.
[5]
are formed as a result of self-assembly from solution. An
exciting, yet little explored area of supramolecular chemistry,
is the reversible interconversion between monomers and
oligomers initiated by the input of external information (e.g.
protons, electrons, photons). Such materials may have func-
tional use due to their switching ability and the possibility to
sequester and release guest molecules. Recently a proton-
dependent monomer± oligomer interconversion in solution
was reported.[ Here we report the topochemical thermal
conversion of a novel, three-dimensional network held
together by strong hydrogen bonding into a covalent, supra-
molecular framework by dehydration of coordinated water.
This unexpected transformation of hydrogen-bonded to
covalent network appears to be assisted by strong NH ´´´ O
hydrogen bonds and irreversible.
[
[
2] C. Carrano, M. Tsutsui, J. Coord. Chem. 1977, 7, 125 ± 130.
3] Crystal structure analysis of 4 ´ 2CHCl
3
´ C
6
H
6
:
C
44
Å
H
24
B
4
Cl10
N
4
O
2
´
2
1
CHCl
3
´ C
6
H
6
: M
r
ˆ 1355.26, triclinic, space group P1, Tˆ 193 K, a ˆ
0.238(12), b ˆ 10.272(3), c ˆ 27.865(7) Š, a ˆ 97.33(2), b ˆ 97.64(5),
3
� 3
g ˆ 96.18(5)8, Vˆ 2857(3) Š , Z ˆ 2,
1
calcd ˆ 1.575 gcm
,
F(000) ˆ
1360. Suitable crystals were grown from a solution in CHCl
3
saturated
with BCl
3
´ MeCN. The crystals were small (0.20 Â 0.12 Â 0.12 mm), of
poor quality, and only weakly diffracting, which limited the data quality
and hence the final precision. Enraf-Nonius CAD-4 diffractometer
with MoKa radiation (l ˆ 0.71069 Š). Total of 9008 reflections to 2q ˆ
6]
�
1
5
A
08. Semi-empirical absorption correction (Y scans, m ˆ 0.81 mm
,
min/Amax ˆ 0.907/0.922). The structure was solved by direct methods
2
and refined by full-matrix least squares on F with all data. The unit cell
contains two independent half-molecules, each related through a center
of symmetry, as well as one benzene and two chloroform molecules per
porphyrin molecule. All atoms were allowed to refine anisotropically,
and hydrogen atoms were included with a riding model. Refinement
converged to R ˆ 0.0937 for the 4249 observed data (I > 2sI) and
[
{Zn(sala)(H O) } ] ´ 2H O (1) was prepared by the reac-
2
2 2 2 2
wR2 ˆ 0.2924 for all data. Goodness of fit on F ˆ 0.973. Programs
tion of Zn(ClO ) ´ 6H O with Li (sala) in aqueous solution
used: SHELXS (structure solution) and SHELXL (structure refine-
ment). Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Center as supplementary publication
no. CCDC-100798 Copies of the data can be obtained free of charge on
application to CCDC, 12 Union Road, Cambridge CB21EZ, UK (fax:
4
2
2
2
and characterized by single-crystal X-ray diffraction techni-
ques[ (H (sala) ˆ N-(2-hydroxybenzyl)-L-alanine). Figure 1
7]
2
shows the structure of the basic dimeric building block,
(
‡44)1223-336-033; e-mail: deposit@ccdc.cam.ac.uk).
[
4] M. O. Senge, C. J. Medforth, T. P. Forsyth, D. A. Lee, M. M. Olmstead,
W. Jentzen, R. K. Pandey, J. A. Shelnutt, K. M. Smith, Inorg. Chem.
1
997, 36, 1149 ± 1163, and references therein.
5] F. C. Hawthorne, P. C. Burns, J. D. Grice in Reviews in Mineralogy, Vol.
3, Boron. Mineralogy, Petrology and Geochemistry (Eds.: E. S. Grew,
L. M. Anovitz), Mineralogical Society of America, Washington DC,
996, chap. 2.
6] H. Borrmann, A. Simon, H. Vahrenkamp, Angew. Chem. 1989, 101,
82; Angew. Chem. Int. Ed. Engl. 1989, 28, 180 ± 181.
7] E. Hanecker, H. Nöth, U. Wietelmann, Chem. Ber. 1986, 119, 1904 ±
910.
8] L. G. Vorontsova, O. S. Chizhov, L. S. Vasilꢁev, V. V. Veselovskii, B. M.
Mikhailov, Izv. Akad. Nauk SSSR Ser. Khim. 1981, 353 ± 357.
9] S. J. Weghorn, J. L. Sessler, V. Lynch, T. F. Baumann, J. W. Sibert, Inorg.
Chem. 1996, 35, 1089 ± 1090.
[
3
1
[
[
[
[
1
1
Topochemical Conversion of a Hydrogen-
Bonded Three-Dimensional Network into a
Covalently Bonded Framework**
John D. Ranford,* Jagadese J. Vittal,* and Daqing Wu
The design and construction of supramolecular, three-
dimensional networks has been an area of increasing interest
over recent years with respect to engineering crystal packing
[
1]
at will. Strategies for crystal engineering include the use of
[
*] Dr. J. D. Ranford, Dr. J. J. Vittal, D. Wu
Department of Chemistry
Figure 1. Top: Structure of the binuclear complex 1. Hydrogen bonds are
drawn with dotted lines. The hydrogen atoms attached to carbon atoms are
omitted for clarity. Selected fragments of neighboring molecules involved
in hydrogen bonding are shown with open bonds. Selected bond dis-
tances[Š] and angles [8]: Zn1 ´´´ Zn1A 3.092(1), Zn1�O1 2.009(2),
Zn1�O1A 2.040(2), Zn1�O2 2.027(2), Zn1�O4 2.030(2), Zn1�N1
National University of Singapore
Lower Kent Ridge Road, Singapore 119260
Fax: (‡65)779-1691
E-mail: chmjdr@nus.edu.sg
chmjjv@nus.edu.sg
.140(2), C9�O2 1.270(4), C9�O3 1.246(4); Zn1-O1-Zn1A 99.58(7), O1-
2
[
**] This research was supported by grants RP950651 (J.D.R.) and
RP970618 (J.J.V.) from the National University of Singapore.
Zn1-N1 93.00(8), O1-Zn1-O1A 79.56(8), O2-C9-O3 124.1(3). Bottom: The
hydrogen bonds link the dimers together to form hexagonal rings.
1
114
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[
{Zn(sala)(H O) } ], along with the coordination around the
2 2 2
II
Zn centers and the hydrogen-bonding network. The zinc
center has distorted square pyramidal geometry with the base
comprised of the tridentate, dianionic sala ligand and the
bridging phenolate moiety. Water completes the coordination
sphere in the apical site. The crystallographically imposed
twofold symmetry results in the two water molecules being on
the same side of the dimeric unit. The dimer has two sets of
NH and OH hydrogen donors and two carboxylate anions as
2
acceptors. The presence of complementary molecular func-
[
8]
tionalities leads to efficient hydrogen bonding between the
neutral dimeric complexes (Figure 1, bottom). Six dimers link
to give a hexagonal ring containing ten zinc centers. The
carboxylate oxygen atoms (O3) that are not involved in
bonding in the ring act as acceptors for hydrogen bonds to
bound water molecules in other rings, thus linking together
the ten-membered hexagonal rings. The result is a honey-
combed, open-framework coordination polymer (Figure 2).
Figure 3. Top: Structure of the dimeric unit of 2. Hydrogen bonds are
drawn with dotted lines. Selected bond distances [Š] and angles [8]: Zn1 ´´´
Zn1A 3.152(1), Zn1�O1 2.072(1), Zn1�O1A 1.999(1), Zn1�O2 2.073(1),
Zn1�O3A 2.017(1), Zn1�N1 2.108(1), C9�O2 1.258(2), C9�O3 1.260(2);
Zn1-O1-Zn1A 101.48(4), O1-Zn1-N1 90.39(4), O1-Zn1-O1A 77.19(4), O2-
C9-O3 125.1(1). Bottom: A segment of the three-dimensional network of 2.
The close resemblance to
1 which results from the topochemical
dehydration and formation of the covalent Zn1�O2 bond can be seen.
(
Figure 3). The structure of this solid-state dehydration
[13]
product 2 bears a close relationship to that of the reactant
; they have the same crystal and point-group symmetry.
1
Owing to the chiral ligand, the space group is also chiral. In 1
and 2 the channels are helical in nature and therefore orient in
the same direction. The intermolecular interactions stabilizing
the structure have changed from hydrogen bonding only in 1
to both covalent and hydrogen bonding in 2, as shown in
Figure 3 and Scheme 1. It is interesting to note that the
NH ´´´ O hydrogen bonding[ is preserved in 2. From the
proximity of the atoms Zn1 and O3 in 1 and the presence of
NH ´´´ O hydrogen bonding in both 1 and 2, it appears that the
Zn�O(carboxylate) bond formation is aided by the presence
of both hydrogen-donor N�H groups and hydrogen acceptors
14]
Figure 2. View of 1 along the crystallographic axis b illustrating the
channels of the open-framework coordination polymer.
The hydrogen-bonded network in 1 provides favorable
conditions for the topochemical reaction to take place. The
geometric proximity between the Zn centers and the carbox-
ylate oxygen atoms from adjacent molecules in 1 (e.g.
Zn1 ´´´ O3C 3.736(2) Š) is maintained by OH ´´´ O hydrogen
bonding. Thermal dehydration can remove ligated and non-
bonded water, which can then escape through the channels
in the binuclear complex. This appears to be the first example
of topochemical conversion of a hydrogen-bonded into a
[
9]
without disrupting the solid-state structure. Minimal atom
movements and conformational changes are anticipated
during dehydration.
[
10, 11]
On heating, all water molecules are lost from 1.
The X-
ray structure determination of the anhydrous compound,
{Zn(sala)} ] (2), reveals a number of unique features
Scheme 1. Coordination environments and hydrogen bonding in the
hydrated 1 and dehydrated 2, illustrating the transformation from hydrogen
bonding to covalent bonding.
[
12]
[
n
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1115

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covalent-bonded supramolecular network. Attempts to rehy-
drate 2 to give 1 have been unsuccessful; therefore, dehy-
dration appears to be irreversible.
and isotropic thermal parameters were refined for the H atoms in the
coordinated water molecules, and riding models were used for the rest.
2
In the final least-squares refinement cycles on j F j , the model
converged at R
1
ˆ 0.0333, wR
> 4s(F
ˆ 0.0662 for all 3385 data. The Flack parameter x was refined to
.003(15).
2
ˆ 0.0609, and GOF ˆ 1.090 for 2808
reflections with F
wR
o
o
) and 182 parameters, and R
1
ˆ 0.0504 and
2
Experimental Section
0
[
8] Close intermolecular hydrogen-bonding distances [Š] and angles [8]:
O2 ´´´ H1 2.050, O3 ´´´ H4B 1.857, O2 ´´´ N1 2.950, O3 ´´´ O4 2.645; O2-
H1-N1 169.6, O3-H4B-O4 174.0.
9] The channels are oval with approximate dimensions 7  10 Š (non-
hydrogen contacts). However, the alternating, stacked arrangement
means that the effective pore size is bigger than this. The channels are
occupied by (disordered) water molecules and held together by
hydrogen bonds. Selected hydrogen-bonded distances [Š]: O3 ´´´ O5
The synthesis of H
2
(sala) was adapted from reference [15]: Salicylaldehyde
(
134 mg, 1.10 mmol) in ethanol (10 mL) was added to a solution of l-
alanine (89 mg, 1.00 mmol) and KOH (56 mg, 1.00 mmol) in water (10 mL).
The yellow solution was stirred for 30 min at room temperature prior to
cooling in an ice bath. The pH was adjusted to 6 ± 7 with acetic acid, and
[
4
then NaBH (46 mg, 1.20 mmol) was added. After 15 min the yellow color
had discharged and the solution was acidified with acetic acid to pH 5.0 and
left for one hour. The product was filtered off, washed with ethanol and
diethyl ether, dried in vacuo, and recrystallized from water/ethanol (1/1).
2
.771, O3 ´´´ O5A 2.781, O3 ´´´ O5B 2.556.
[
10] Thermogravimetric analysis of 1 indicated a weight loss of 11.2% in
the temperature range 50 ± 1208C, corresponding to the loss of two
molecules of water (expected weight loss 12.2%) and the formation of
the anhydrous compound 2. The X-ray powder pattern of this
anhydrous material was the same as that of 2. Both 1 and 2 show
the same decomposition pattern, which starts at about 3408C.
3
0
Yield: 109 mg (56%), m.p. 241 ± 2428C, [a]
: H (sala) (195 mg, 1.00 mmol) was added to a solution containing LiOH
48 mg, 2.00 mmol) and CH CO Na ´ 3H O (136 mg, 1.00 mmol) in water
20 mL). A solution of Zn(ClO ´ 6H O (372 mg, 1.00 mmol) in water
10 mL) was gradually added to the above stirred solution. The mixture was
L
ˆ � 22.2 (c ˆ 0.5 in water).
1
2
(
(
(
3
2
2
4
)
2
2
stirred for 30 min, filtered, and kept at room temperature for several days
to yield distorted, octahedral-shaped crystals. The crystals were separated
by decantation and dried in air. Yield: 191 mg (65%). C,H,N analysis: calcd
[
11] The structures of the bulk materials for 1 and 2 were confirmed by
matching their X-ray powder patterns with those generated from the
corresponding single crystals. Compound
2 was also prepared
for C10
KBr): nÄ ˆ 1588 (s, nas(CO
solution of (sala) (195 mg, 1.00 mmol) and LiOH (24 mg,
.00 mmol) in water (10 mL) was added to a solution of Zn(ClO
O (372 mg, 1.00 mmol) in water (10 mL). The solution was stirred for
0 min and left at room temperature to evaporate. Large, distorted
5
H15NO Zn: C 40.7, H 5.1, N 4.7; found: C 40.4, H 5.1, N 4.5; IR
independently. The crystal structure was carried out on the single
crystal grown from aqueous solution.
�
1
(
2 s 2
)), 1413 (s, n (CO )), 1282 cm (s, n(C-O)carb).
[
16]
2
:
A
H
2
[12] Crystal structure determination of 2:
Tetragonal, space group
3
1
4
)
2
´
P4
3
2
1
2, a ˆ 8.997(1), c ˆ 24.571(4) Š, Vˆ 1988.8(5) Š , Z ˆ 4, 1calcd
ˆ
�
3
6
3
H
2
1.727 gcm . All H atoms were located successfully and refined with
2
riding models. In the final least-squares refinement cycles on j F j , the
diamond-shaped, colorless crystals were separated by decantation and
dried in air. Yield: 176 mg (68%). C,H,N analysis: calcd for C10 Zn:
model converged at R
2525 reflections with F
and wR
to � 0.004(8).
1
ˆ 0.0152, wR
2
ˆ 0.0422, and GOF ˆ 1.031 for
H
11NO
3
o
> 4s(F
o
) and 138 parameters, and R
1
ˆ 0.0158
C 45.6, H 4.4, N 5.3; found: C 45.4, H 4.7, N 5.1; IR (KBr): nÄ ˆ 1598 (s,
2
ˆ 0.0425 for all 2571 data. The Flack parameter x was refined
�
1
n
as(CO
2
)); 1404 (s, n
s
(CO
2
)); 1284 cm (s, n(C-O)carb).
[
13] The single crystal of 1 became opaque and brittle on heating at 908C
Received: November 11, 1997 [Z11148IE]
for two hours.
German version: Angew. Chem. 1998, 110, 1159 ± 1162
[14] Distances [Š] and angles [8] of the hydrogen bonds: O2 ´´´ H1 2.161,
O2 ´´´ N1 2.944; N1-H1-O2 144.
[
15] L. L. Koh, J. D. Ranford, W. T. Robinson, J. O. Svensson, L. C. Tan, D.
Wu, Inorg. Chem. 1996, 35, 6466 ± 6472.
Keywords: coordination polymers ´ crystal engineering ´
supramolecular chemistry ´ topochemistry ´ zinc
[
16] General crystallographic details: Data were collected on a Siemens
SMART CCD system with graphite-monochromated MoKa radiation
and a sealed tube (2.4 kW) at 238C. Absorption corrections were
made with the program SADABS (G. M. Sheldrick, Göttingen, 1996),
and the crystallographic software package SHELXTL (SHELXTL
Reference Manual, Version 5.03, Wisconsin, 1996) was used for all
calculations. Crystallographic data (excluding structure factors) for
the structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Center as supplementary publica-
tion no. CCDC-100837. Copies of the data can be obtained free of
charge on application to CCDC, 12 Union Road, Cambridge
CB21EZ, UK (fax: (‡44)1223-336-033; e-mail: deposit@ccdc.cam.
ac.uk).
[
[
[
1] a) G. R. Desiraju, Chem. Commun. 1997, 1475 ± 1482; b) Crystal
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[
[
4] P. J. Fagan, M. D. Ward, The Crystal as a Supramolecular Entity.
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6] N. Matsumoto, Y. Mizuguchi, G. Mago, S. Eguchi, H. Miyasaka, T.
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[
7] Crystal structure determination of 1:[16] Tetragonal, space group
3
P4
3
2
1
2, a ˆ 10.7799(1), c ˆ 23.0372(1) Š, Vˆ 2677.07(4) Š , Z ˆ 4,
�
3
1
calcd ˆ 1.462 gcm . All H atoms were located successfully. Positional
1
116
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Angew. Chem. Int. Ed. 1998, 37, No. 8