Visual synchronous exchange of metal nodes and counteranions constituting a cobalt(II) coordination polymer

Article abstract of DOI:10.1021/ic5013186

A solid-state simultaneous exchange of metal nodes and counteranions based on a cobalt(2+) coordination polymer is reported for the first time. The ion-exchange process is visual, and the structural integrity of the cobalt(2+) coordination polymer is maintained during the ion-exchange process.

Full text of DOI:10.1021/ic5013186

Communication
pubs.acs.org/IC
Visual Synchronous Exchange of Metal Nodes and Counteranions
Constituting a Cobalt(II) Coordination Polymer
Jian-Cheng Wang, Qi-Kui Liu, Jian-Ping Ma, Fang Huang, and Yu-Bin Dong*
College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for
Chemical Imaging, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Normal University, Jinan
250014, P. R. China
*
S Supporting Information
Scheme 1. Synthesis of 1
ABSTRACT: A solid-state simultaneous exchange of
metal nodes and counteranions based on a cobalt(2+)
coordination polymer is reported for the first time. The
ion-exchange process is visual, and the structural integrity
of the cobalt(2+) coordination polymer is maintained
during the ion-exchange process.
oordination polymers are the species that are constructed
from metal nodes and organic spacers. So far, the most
1
C
effective approach to the synthesis of coordination polymers is
self-assembly. In principle, a coordination polymer could be
considered as the metal salt of the conjugate base of a weak acid,
so the isomorphous replacement of metal nodes by other kinds of
Figure 1. ORTEP figure of 1 (displacement ellipsoids drawn at the 30%
probability level).
2
metal cations is possible. To date, metal node exchange is rare,
although it has been becoming a very useful postsynthetic
approach to accessing the coordination polymers that are not
easy to be prepare by direct synthesis. To our knowledge,
relatively few examples concerning metal node exchange have
pyridyl [dCo−N = 2.244(6) Å] donors. The axial positions are
−
occupied by two coordinated Cl anions [d
= 2.388(2) Å].
Co−Cl
Compound 1 is stable in air as well as in MeOH (Figure S1 in the
SI).
Metal node exchange based on 1 was simply realized by the
combination of 1 with Cu2+ in solution. As shown in Scheme 2,
when compound 1 was soaked in a MeOH solution of CuCl2
(0.02 mol/L) for 30 min, the crystals of 1 underwent a rapid
naked-eye-detectable color change. As illustrated in Scheme 2,
3
been reported. On the other hand, among various coordination
polymers, cationic coordination polymers often occur when
neutral organic ligands are used in construction of the
frameworks, so the net positive charge on the frameworks
necessitates charge-balancing of extraframework anions. Com-
pared to metal node exchange, anion exchange is much more
common. In particular, the simultaneous exchange of metal
nodes and counteranions without altering the structural integrity
of the framework is hitherto unknown in coordination polymers.
Ion exchange (including exchange of metal cations and/or
counteranions) based on metal−organic frameworks (MOFs) is
Scheme 2. Synthesis of 2−4 Based on Metal Nodes and
a
Counter Ions Exchange
4
of great interest, and such a postsynthetic approach might be
able to conveniently modify or improve MOF functions under
ambient conditions.
In this contribution, we report for the first time the
synchronous metathesis of both metal nodes and counterions
based on a 1D cobalt(2+) coordination polymer.
Co L Cl (1) was obtained as purple crystals by the
2
2
2
combination of L and CoCl in a mixed-solvent system of
2
CH Cl /methanol (MeOH) at ambient temperature (Scheme
2
2
1
). Single-crystal X-ray diffraction analysis revealed that the 1D
coordination polymer of 1 (Figure S1 in the Supporting
Information, SI) crystallizes in the triclinic space group P1. As
a
The photographs of 1−4 and their formation process are inset.
̅
2
+
shown in Figure 1, each Co node in 1 adopts a distorted
octahedral {CoN Cl } coordination sphere. The basal plane is
Received: June 7, 2014
4
2
composed of two N-pyrimidyl [dCo−N = 2.212(5) Å] and two N-
Published: September 26, 2014
©
2014 American Chemical Society
10791
dx.doi.org/10.1021/ic5013186 | Inorg. Chem. 2014, 53, 10791−10793

Inorganic Chemistry
Communication
the color of the resulting crystalline solids of Cu0.74Co0.26L2Cl2
framework structural integrity of 1 is maintained, which is well
demonstrated by the measured PXRD pattern (Figure 2).
For Cu(NO ) , as illustrated in Scheme 2, the color of 1
(2) gradually changed from purple to green, which is further
supported by the UV−vis spectrum (Figure S2 in the SI).
Unfortunately, the crystals of 1 did not diffract the X-ray beams
due to the loss of single crystallinity during the process. The
powder X-ray diffraction (PXRD) pattern based on 2, however, is
identical with that of 1, indicating that the structural integrity is
maintained (Figure 2), so the color change of 1 resulted from
3
2
changed from purple to sky blue after 1 was immersed in a
MeOH solution (0.02 mol/L) of Cu(NO ) for 12 h (Figure S5
3
2
6
in the SI). The Cu 2p3 (at 933.71 eV) and Cl 2p (at 197.78
/2
7
2+
2+
eV) peak positions are in accordance with the presence of Cu
and Cl ions (Figure 4), respectively. Similar to 3, no Co
−
Figure 4. (Left) XPS spectra of 4. No detectable Co2+ species was
observed. (Right) IR spectra recorded during the ion-exchange process
at 0−12 h.
Figure 2. (Left) PXRD patterns of 1−4. (Right) XPS spectra of 2.
metal node exchange. The coexistence of Co2+ and Cu2+ in 2 is
further demonstrated by X-ray photoelectron spectroscopy
species was detected in 4 based on XPS measurement, indicating
(
XPS) measurement, which is evidenced by the observation of
2+
2+
that the Co ion in 1 was completely replaced by Cu . On the
5
Co 2p3/2 (at 779.7 eV), Co 2p (at 794.24 eV), and Cu 2p
(
−
1/2
3/2
other hand, IR spectra show that the bands associated with NO3
6
at 934.62 eV) peaks in the XPS spectra of 2 (Figure 2). The
are significantly enhanced as time goes on, indicating that the Cl−
ion in 1 was exchanged by the incursive nitrate anions (Figure 4).
The ICP measurements (Table S3 and Figure S6 in the SI) reveal
metal-cation-exchange degree in 1 was determined by inductively
coupled plasma (ICP) measurement. The ICP-measured result
(
Table S1 and Figure S3 in the SI) indicates that the amount of
2+
2+
that ca. 100% of Co cations in 1 were replaced by Cu cations;
2+
Cu is up to ca. 75%, which is in accordance with the molecular
formula of Cu0.74Co0.26L Cl .
−
−
meanwhile, ca. 35% of Cl anions were exchanged by the NO
3
2
2
anions. So, the ion-exchange reaction yields compound 4 with a
To provide further insight into metal node exchange based on
, CuBr and Cu(NO ) were used instead of CuCl to perform
molecular formula of CuL Cl (NO ) . The PXRD pattern
2
1.3
3 0.7
1
2
3 2
2
based on the ion-exchanged sample of 4 is identical with that of 1
Figure 2), suggesting that the framework is intact upon ion
the ion-exchange reactions under the same conditions. By simply
immersion of the crystals of 1 in a MeOH solution (0.02 mol/L)
(
exchange.
of CuBr for 3 h, the color of 1 stepwise-changed from purple to
2
Notably, no ligand species were detected in mother liquors of
−4 based on the H NMR spectrum during the process (Figure
dark brown to generate Cu0.98Co0.02L2ClBr (3; Scheme 2 and
Figure S3 in the SI). Notably, XPS measurements (Figure 3)
1
2
S7 in the SI), indicating that the above visual synchronous
metathesis of metal nodes and counteranions based on 1 is a
solid-state ion exchange. To further confirm this, liquid
chromatography (LC) was used to monitor the mother liquors
of 2−4. For 2 and 3, no ligand was present in the mother liquors
based on LC analysis; for 4, only a tiny amount of ligand was
detected, indicating that compound 4 is slightly soluble in
MeOH (Figure S8 in the SI).
Figure 3. XPS spectra of 3. No detectable Co2+ species was observed.
It is noteworthy that the copper(2+) coordination polymers
with the same structure of 1 cannot be obtained by the direct
−
−
combination of L and corresponding CuX (X = Cl , Br , and
−
NO ) salts in MeOH/CH Cl (Figure S9 in the SI) and other
3
2
2
2
+
show that compound 3 contains not only Cu (Cu 2p3/2 at
solvent systems such as EtOH/CH Cl , CH CN/CH Cl ,
2 2 3 2 2
6
−
7
9
33.38 eV) and Cl (Cl 2p at 197.55 eV) species but also the
MeOH/CHCl , EtOH/CHCl , MeOH/THF, and H O/
3 3 2
−
7
2+
Br (Br 3d at 67.51 eV) anion, which means that both Co
nodes and the Cl counteranions in 1 were simultaneously
replaced by Cu and Br . Interestingly, no obvious peaks related
to Co were observed based on XPS, indicating that almost all
MeOH. Notably, the metal node and counteranion exchanges
herein are irreversible under the experimental conditions. In
addition, ion exchange did not occur when CuSO , Cu(OAc) ,
−
2+
−
4
2
2+
and Cu(SO CF ) were used to perform the reactions under the
3 3 2
2+
2+
Co cations in 1 are exchanged by Cu . The ICP measurement
same conditions.
(
Table S2 and Figure S4 in the SI) shows that the amount of Cu2+
Notably, the ion-exchange reaction time of 1 based on the
−
−
−
is up to ca. 98%, and ion chromatography (IC) analysis of the
different CuX (X = Cl , Br , and NO ) salts was monitored by
2
3
−
amount of Cl ions is ca. 50% (see the SI). So, the structural
PXRD. The ion-exchange time exceeded 0.5 h (for 2), 3 h (for 3),
and 12 h (for 4); the solid-state structure of 1 could not be
formula of compound 3 should be Cu0.98Co0.02L2ClBr. Again, the
1
0792
dx.doi.org/10.1021/ic5013186 | Inorg. Chem. 2014, 53, 10791−10793

Inorganic Chemistry
Communication
maintained based on the PXRD measurement. As mentioned8
above, the ion-exchange rate of these reactions is quite different.
For example, the naked-eye-detectable color change from 1 to 2
was observed in ∼1 min, while the color changes from 1 to 3 and
from 1 to 4 were observed in 0.5 and 1 h, respectively. All of the
reaction conditions, including starting materials, solvents, and
temperature, are the same except anions, so the different ion-
exchange rates herein might be caused by the different anions.
For further understanding the different ion-exchange rates
caused by the different metal salts, DFT calculations were carried
out. The calculations were carried out using Gaussian 09 at the
M06 level. A 6-31G* basis set was employed for Cl, Br, N, and O
atoms. For Cu and Co atoms, the standard LanL2DZ was used.
CoCl , CuCl , CoBr , CuBr , Co(NO ) , and Cu(NO ) were
ACKNOWLEDGMENTS
We are grateful for financial support from the 973 Program
Grant 2012CB821705), NSFC (Grants 21271120 and
■
(
21101100), and “PCSIRT”.
REFERENCES
■
(
(1) Leong, W. L.; Vittal, J. J. Chem. Rev. 2011, 111, 688−764.
2) Lalonde, M.; Bury, W.; Karagiaridi, O.; Brown, Z.; Hupp, J. T.;
Farha, O. K. J. Mater. Chem. A 2013, 1, 5453−5468 and references cited
therein.
(
3) So far, some typical examples for metal node exchange based on
coordination polymers in the solid state have been reported. See:
(a) Dinca,
̆
M.; Long, J. R. J. Am. Chem. Soc. 2007, 129, 11172−11176.
(b) Brozek, C. K.; Dinca, M. Chem. Sci. 2012, 3, 2110−2113. (c) Li, J.;
Li, L.; Hou, H.; Fan, Y. Cryst. Growth Des. 2009, 9, 4504−4513.
2
2
2
2
3 2
3 2
(
́ ́
d) Botas, J. A.; Calleja, G.; Sanchez-Sanchez, M.; Orcajo, M. G.
fully optimized. Single-point calculation of CoCl2L2 was
performed based on its X-ray crystal structure. Because the
PXRD measurements gave the same structural information for
CuCl L , CuBr L , CoBr L , Cu(NO ) L , and Co(NO ) L ,
Langmuir 2010, 26, 5300−5303. (e) Denysenko, D.; Werner, T.;
Grzywa, M.; Puls, A.; Hagen, V.; Eickerlinbg, G.; Jelic, J.; Reuter, K.;
Volkmer, D. Chem. Commun. 2012, 48, 1236−1238. (f) Mi, L.; Hou, H.;
Song, Z.; Han, H.; Xu, H.; Fan, Y.; Ng, S.-W. Cryst. Growth Des. 2007, 7,
2553−2561. (g) Das, S.; Kim, H.; Kim, K. J. Am. Chem. Soc. 2009, 131,
814−3815. (h) Cairns, A. J.; Perman, J. A.; Wojtas, L.; Kravtsov, V. C.;
Alkordi, M. H.; Eddaoudi, M.; Zoworotko, M. J. J. Am. Chem. Soc. 2008,
30, 1560−1561. (i) Zhang, Z.-J.; Shi, W.; Niu, Z.; Li, H.-H.; Zhao, B.;
Cheng, P.; Liao, D.-Z.; Yan, S.-P. Chem. Commun. 2011, 47, 6425−6427.
(j) Kim, M.; Cahill, J. F.; Fei, H.; Prather, K. A.; Cohen, S. M. J. Am.
Chem. Soc. 2012, 134, 18082−18088. (k) Mukherjee, G.; Biradha, K.
Chem. Commun. 2012, 48, 4293−4295. (l) Prasad, T. K.; Hong, D. H.;
Suh, M. P. Chem.Eur. J. 2010, 16, 14043−14050. (m) Yao, Q.; Sun, J.;
Li, K.; Su, J.; Peskov, M. V.; Zou, X. Dalton Trans. 2012, 41, 3953−3955.
n) Wei, Z.; Lu, W.; Jiang, H.-L.; Zhou, H.-C. Inorg. Chem. 2013, 52,
164−1166. (o) Shultz, A. M.; Sarjeant, A. A.; Farha, O. K.; Hupp, J. T.;
Nguyen, S. B. T. J. Am. Chem. Soc. 2011, 133, 13252−13255. (p) Zhang,
Z.; Zhang, L.; Wojtas, L.; Nugent, P.; Eddaoudi, M.; Zaworotko, M. J. J.
Am. Chem. Soc. 2011, 134, 924−927. (q) Zhang, Z.; Gao, W.-Y.; Wojtas,
L.; Ma, S.; Eddaoudi, M.; Zaworotko, M. J. Angew. Chem., Int. Ed. 2012,
2
2
2
2
2
2
3 2
2
3 2 2
Co−Cl bonds in CoCl L were replaced by Cu−Cl, Cu−Br, Co−
2
2
3
Br, Cu−NO , and Co−NO bonds, giving the structures of
3
3
CuCl L , CuBr L , CoBr L , Cu(NO )L , and Co(NO )L .
2
2
2
2
2
2
3
2
3
2
1
Then electronic energies of CuCl L , CuBr L , CoBr L ,
2
2
2
2
2 2
Cu(NO ) L , and Co(NO ) L were obtained from optimiza-
3
2
2
3 2 2
tion of the Cu−Cl, Cu−Br, Co−Br, Cu−NO , and Co−NO3
3
moieties with metal−L parts frozen. The electronic energies were
further improved by single-point calculation, with solvent effects
(
SCRF = IEFPCM and solvent = MeOH) taken into account.
According to the calculations, the electronic energy changes of
the three reactions [CuCl + CoCl L → CoCl + CuCl L (1);
(
1
2
2
2
2
2
2
CuBr + CoCl L → CoCl + CuBr L (2); Cu(NO ) +
2
2
2
2
2
2
3 2
CoCl L → CoCl + Cu(NO ) L (3)] are −2.4(1), 16.3(2), and
2
2
2
3 2 2
19.6(3) kcal/mol, which are in good agreement with the
5
́
1, 9330−9334. (r) Morris, W.; Volosskiy, B.; Demir, S.; Gandara, F.;
McGrier, P. L.; Furukawa, H.; Cascio, D.; Stoddart, J. F.; Yaghi, O. M.
observations of the above ion-exchange reactions.
In summary, we have successfully demonstrated, for the first
time, a simultaneous exchange of metal nodes and counteranions
on the coordination polymers in the solid state. The facile
exchange of metal nodes and counterions without loss of
structural integrity as described herein might provide an
alternative approach to constructing heterometallic and
heteroanionic coordination polymer materials with the same
framework structural feature under ambient conditions. On the
other hand, such interesting naked-eye-detectable ion-responsive
color changes might be useful in visual sensors for the detection
of metal cations and counteranions.
Inorg. Chem. 2012, 51, 6443−6445.
(
4) (a) Wang, Z.; Cohen, S. M. Chem. Soc. Rev. 2009, 38, 1315−1329.
(b) Song, Y.-F.; Cronin, L. Angew. Chem., Int. Ed. 2008, 47, 4635−4637.
(c) Tanabe, K. K.; Cohen, S. M. Chem. Soc. Rev. 2011, 40, 498−519.
(5) Jia, C.-J.; Schwick, M.; Weidenthaler, C.; Schmidt, W.; Korhonen,
S.; Weckhuysen, B. M.; Schu
1288.
6) (a) Balamurugan, B.; Mehta, B. R.; Shivaprasad, S. M. Appl. Phys.
̈
th, F. J. Am. Chem. Soc. 2011, 133, 11279−
1
(
Lett. 2001, 79, 3176−3178. (b) Huang, Y. G.; Mu, B.; Schoenecker, P.
M.; Carson, C. G.; Karra, J. R.; Cai, Y.; Walton, K. S. Angew. Chem., Int.
Ed. 2011, 50, 436−440.
(
7) Ma, J.-P.; Yu, Y.; Dong, Y.-B. Chem. Commun. 2012, 48, 2946−
948.
8) (a) Song, X.; Kim, T. K.; Kim, H.; Kim, D.; Jeong, S.; Moon, H. R.;
2
(
ASSOCIATED CONTENT
Lah, M. S. Chem. Mater. 2012, 24, 3065−3073. (b) Song, X.; Jeong, S.;
Kim, D.; Lah, M. S. CrystEngComm 2012, 14, 5753−5756.
■
*
S
Supporting Information
Synthesis and characterization data for the ligand and 1−4,
including figures and tables for ORTEP, crystal packing, ICP, IC
analysis, UV−vis spectra, LC analysis, a CIF file, and crystal data.
This material is available free of charge via the Internet at http://
pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: yubindong@sdnu.edu.cn.
Notes
The authors declare no competing financial interest.
1
0793
dx.doi.org/10.1021/ic5013186 | Inorg. Chem. 2014, 53, 10791−10793