Solid-state structural transformations of two AgI supramolecular polymorphs to another polymer upon absorption of HNO3 vapors

Article abstract of DOI:10.1021/ic3008415

Solid-state structural transformation of two polymorphic forms of [Ag(8-HqH)(8-Hq)]_n (1α and 1β, where 8-HqH = 8-hydroxyquinoline and 8-Hq^- = 8-hydroxyquinolate) to {[Ag(8-HqH)₂]NO₃}_n (2) has been observed upon solid-gas reaction of compounds 1α and 1β with HNO₃ vapors. Solid-gas reaction of compound 2 with hydrated vapors of NH₃ results in the formation of only the 1β polymorph, while solid-solid reaction of compound 2 with KOH results in the formation of a 1α and 1β mixture with chiral and achiral space groups of P2₁2 ₁2₁ and Pbcn, respectively.

Full text of DOI:10.1021/ic3008415

Communication
pubs.acs.org/IC
I
Solid-State Structural Transformations of Two Ag Supramolecular
Polymorphs to Another Polymer upon Absorption of HNO Vapors
3
Kamran Akhbari and Ali Morsali*
Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Islamic Republic of Iran
*
S Supporting Information
9
2
006 and refined in space group Pbcn. Another form (1α) is
ABSTRACT: Solid-state structural transformation of two
reported by us (see the Supporting Information, SI). These
polymorphic forms of [Ag(8-HqH)(8-Hq)] (1α and 1β,
n
polymorphs convert to 2 upon absorption of HNO vapors
3
−
where 8-HqH = 8-hydroxyquinoline and 8-Hq = 8-
(
Figure 1). Figure S10 in the SI shows the structures of the basic
hydroxyquinolate) to {[Ag(8-HqH) ]NO } (2) has been
2
3
n
building blocks of compounds 1α, 1β, and 2.
observed upon solid−gas reaction of compounds 1α and
1
β with HNO vapors. Solid−gas reaction of compound 2
3
with hydrated vapors of NH results in the formation of
3
only the 1β polymorph, while solid−solid reaction of
compound 2 with KOH results in the formation of a 1α
and 1β mixture with chiral and achiral space groups of
P2 2 2 and Pbcn, respectively.
1
1 1
he utilization of intermolecular interactions that generate
specific supramolecular motifs has greatly enhanced the
T
systematic approach to both the understanding and design of
1
highly organized molecular arrays in solids. Intermolecular
hydrogen bonding and ionic or dipolar interactions have been
2
the most widely employed “directional forces” in this context. In
addition to the above-mentioned intermolecular interactions, in
silver(I) supramolecular chemistry, similar to thallium(I)
supramolecular chemistry, other secondary interactions such
Figure 1. Schematic diagram illustrating the dynamic structural
conversions of compounds 1α and 1β to a supramolecular network of
3
2
by solid−gas and solid−solid reactions. Color code: Ag, violet; O, red;
as Ag···C, Ag···Ag, and Ag···H also exist that distinguish silver(I)
N, blue; C, gray; H, white.
supramolecular polymers from other supramolecular com-
4
pounds. To develop further our understanding of supra-
molecular architecture, it is challenging to continue the
investigations on the solid-state structural transformations5
involving coordination polymers and supramolecular networks.
Single-crystal X-ray diffraction analysis (Tables S2 and S3 in
the SI) of compound 1α shows that the complex is a chiral one-
dimensional supramolecular network, as illustrated in Figure 1. 8-
Hydroxyquinoline acts as a bidentate chelating ligand with two
6
In a continuation of studies of supramolecular compounds, in
−
this report we isolated two polymorphs of [Ag(8-HqH)(8-Hq)]
forms of protonated (8-HqH) and deprotonated (8-Hq )
n
−
I
(1α and 1β, where 8-HqH = 8-hydroxyquinoline and 8-Hq = 8-
ligands. The Ag ions in 1α are coordinated by two N and two
−
hydroxyquinolate) that do novel solid-state structural trans-
O atoms of 8-HqH and 8-Hq ligands (Figure S10a in the SI).
I
formations to {[Ag(8-HqH) ]NO } (2) by absorption HNO
Our search shows that the Ag ions in compound 1α may also be
2
3
n
3
involved in an η1 interaction with the phenyl group of
vapors. Because of amphoteric behavior, compounds 1α and 1β
are good candidates for studies of the acid/base transformations
in the solid state. Similar transformations were observed by Braga
neighboring [Ag(8-HqH)(8-Hq)] units (Figure S11a in the
I
SI). Thus, the Ag coordination sphere is completed, and rather
III
5
et al. in a zwitterionic sandwich complex of [Co (η -
than a AgN
considered to contain an O N
2 2
Ag···C distance of 3.199 Å. A π−π stacking interaction between
the parallel aromatic rings of adjacent units is also observed in 1α
2
O
2
coordination sphere, the complex could be
1
C H COOH)(η -C H COO)], which undergoes reversible
Ag···C coordination sphere with a
5
4
5
4
10
gas−solid reaction with the hydrated vapors of acids (e.g., HCl,
CF COOH, CCl COOH, CHF COOH, HBrF , and HCOOH)
3
3
2
4
(
Figure S12a in the SI). The mean molecular planes are close to
and bases (e.g., NH , NMe , and NH Me) as well as solid−solid
3
3
2
parallel and are separated by a distance of ∼3.7 Å, close to that of
the planes in graphite.
electrostatic hydrogen-bonding network between O3(8-Hq )
reactions with crystalline salts (e.g., KBr, RbBr, CsBr, NaI, and
1
0,11
7
The existence of a moderate
CsI). Compound [Ag(8-HqH)(8-Hq)] crystallized in at least
n
−
two different polymorphic forms. These forms have been
identified since 1962 by their different powder X-ray diffraction
8
patterns, yet there is no conclusive report on these forms. One
Received: April 24, 2012
form (1β) was crystallographically characterized by Ma et al. in
Published: February 25, 2013
©
2013 American Chemical Society
2787
dx.doi.org/10.1021/ic3008415 | Inorg. Chem. 2013, 52, 2787−2789

Inorganic Chemistry
Communication
2
and H2W(8-HqH) with bond distances of 1.681 Å (Figures 1
and S12a in the SI), η -Ag···C interactions (Figures 1 and S11a in
polymeric complexes containing weak Ag−C(sp ) bonds with a
1
13
mean Ag−arene distance of 2.82−3.37 Å have been reported.
the SI), and π−π stacking (Figure S12a in the SI) in 1α results in
With this level of data (Table S2 in the SI), it really is not possible
to conclude anything about the protonation state of the ligand
(i.e., to locate H atoms), but the charge balance of compound 2,
the formation of a one-dimensional supramolecular network. In
I
the other polymorphic form (1β), the Ag ion is located on a 2-
−
after entrance of a NO3− anion to the structures of 1α and 1β,
fold axis and chelated by two 8-HqH and 8-Hq molecules with
9
−
distorted tetrahedral geometry. This achiral polymorph (1β)
needs protonation of the 8-Hq ligand in [Ag(8-HqH)(8-Hq)] .
n
forms a three-dimensional supramolecular network, which could
On the other hand, the appearance of a very broad band at the
I
−1
be observed along the b axis in Figure 1. The Ag ions in 1α are
frequency range of 2200−3500 cm in the IR spectrum (Figure
−
−
coordinated by two N and two O atoms of 8-HqH and 8-Hq
S9 in the SI) indicates that protonation of the 8-Hq ligand in 2
I
ligands (Figure S10b in the SI). The Ag complexes in 1β were
has occurred and probably the hydrogen-bonding network exists
in 2. In this solid-state structural transformation, the
coordination bond rearrangement for the Ag−N and Ag−O
bonds occurs and any new bond is not formed (Tables S3 and S4
in the SI). Indeed a monohapto interaction in 1α and two
monohapto interactions in 1β were substituted with two weaker
dihapto interactions in compound 2 (Figure 2 and Table S5 in
linked to each other via hydrogen bonding to form a
9
supramolecular chain structure (Figure S12b in the SI). Our
I
search shows that the Ag ions in compound 1β may also be
1
involved in two η interactions with the phenyl group of
neighboring [Ag(8-HqH)(8-Hq)] units (Figure S11b in the SI).
Thus, the complex could be considered to contain an
O N Ag···C coordination sphere with a Ag···C distance of
2
2
2
3
1
.358 Å. No π−π stacking interaction exists in 1β. The crystals of
α and 1β turned black (probably because of the surface
corrosive nature of HNO after conversion of both polymorphs
3
to compound 2 in the presence of extra HNO vapors) upon
3
exposure to diluted HNO fumes for 5 h and were not suitable for
3
single-crystal X-ray crystallography. Both of them have similar
PXRD patterns, with some differences in peak intensities, which
differed from those of 1α and 1β (Figure S3 in the SI). In this
solid−gas reaction, in addition to HNO vapors, various forms of
3
nitric oxides including NO formed from decomposition of
2
HNO . Thus, in addition to the reaction of HNO vapors with 1α
3
3
and 1β polymorphs, the reaction between water droplets that
formed on the surface of compounds 1α and 1β with NO gas,
2
which exists in the enclosed vessel of the reaction, results in the
formation of compound 2. It should be mentioned that similar
reactions of both polymorphs with HCl vapors result in theI
formation of AgCl, which is due to the strong affinity of the Ag
ion toward chloride ions in the presence of the 8-HqH
coordinating ligand (Figures S4 and S5 in the SI).
Single crystals of compound 2 were obtained from another
reaction (Figure S3 in the SI). The structure determination of 2
by X-ray crystallography (Tables S2 and S4 in the SI) showed
Figure 2. Schematic representation of the solid-state structural
transformations of compounds 1α and 1β to compound 2 by solid−
gas and solid−solid reactions, showing a coordination bond rearrange-
I
ment around Ag ions. Color code: Ag, violet; O, red; N, blue; C, gray; H,
white.
the SI). As could be observed from PXRD patterns (Figure S14
that one HNO molecule was added to each [Ag(8-HqH)(8-
in the SI), when we did the solid−gas reaction of compound 2
3
I
Hq)] unit. Two types of Ag ions exist in 2, Ag1 and Ag2. The
coordination number in 2 is 4, and each Ag ion is coordinated by
with hydrated vapors of NH , only the 1β polymorph was
3
I
obtained, while by solid−solid reaction of compound 2 crystals
with KOH, a mixture of 1α and 1β was formed (Figures 1 and 2).
Compound 1α was only observed in a mixture when refluxed
filtrate was evaporated (see the SI), and we could not obtain a
purified precipitate of the 1α polymorph in order to study of
nanostructural morphology during the mentioned transforma-
tions. The large amount of precipitate obtained during reflux
reaction was characterized to be the β form by matching PXRD
patterns (Figure S1 in the SI). In order to study the morphology
and size of compound 1β nanostructures during transformation
to compound 2, four samples were prepared by microwave-
two N and two O atoms of two 8-HqH ligands (Figure S10c in
the SI). The bond angles of 2 are different from the bond angles
of 1α and 1β. Compound 2 has O−Ag−O and N−Ag−N bond
I
angles of 180°, and the Ag ions have square-planar coordination
geometry, but these bond angles are 158.18 and 162.48° in
compound 1α and 93.6 and 157.2° in compound 1β. Thus,
HNO absorption of 1α and 1β results in the formation of 2 with
3
I
regular square-planner geometry around Ag ions. Again a search
for Ag···C approaches indicates that Ag atoms in compound 2
2
may also be involved in 2η interactions with the two phenyl
+
14
groups of neighboring [Ag(8-HqH) ] units (Table S5 in the SI).
assisted syntheses (see the SI). Figure 3a shows a SEM image of
2
I
Thus, each Ag ion has short interactions with four C atoms of
1β, which indicates the formation of a mixture from microrods
and nanoparticles. When sample 1βb undergoes a solid−gas
reaction with HNO3 vapors, compound 2 nanostructures
(sample 2b) were formed. Figure S6b in the SI shows the IR
spectrum of sample 2b, which is different from sample 1βb
(Figure S6a in the SI) and approved the formation of 2
nanostructures. This solid−gas reaction of compound 1β powder
was tested by three other samples with different morphologies
(Figures S16−S18a,b in the SI). In each case, different
two neighboring phenyl groups (Figure S13 in the SI), and rather
I
than an AgN O coordination sphere, the Ag ions could be
2
2
considered to contain a tetrahapto center with an O N Ag···C
2
2
4
2
coordination sphere. These 2η -Ag···C interactions result in the
formation of parallel chains in 2 (Figure 1). The distance of
Ag···C interactions observed in these three compounds (Table
S5 in the SI) is less than the sum of the van der Waals radii for Ag
12
and C atoms (3.42 Å). Some other silver(I) polycyclic aromatic
2
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Inorganic Chemistry
Communication
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Support of this investigation by Tarbiat Modares University is
gratefully acknowledged. We also sincerely thank Prof. Jagadese
J. Vittal at National University of Singapore for his very useful
guidance.
REFERENCES
■
(
1) Hellmann, K. W.; Gade, L. H.; Fleischer, R.; Stalke, D. Chem.
Commun. 1997, 527.
(2) Zerowski, J. A.; Seto, C. T.; Whitesides, G. M. J. Am. Chem. Soc.
Figure 3. SEM images of (a) compound 1β (sample 1βb) prepared by a
microwave-assisted process, (b) compound 2 (sample 2b) prepared
1992, 114, 5473.
(3) Akhbari, K.; Morsali, A. Coord. Chem. Rev. 2010, 254, 1977.
(4) (a) Akhbari, K.; Morsali, A. Cryst. Growth Des. 2007, 7, 2024.
(b) Akhbari, K.; Morsali, A. CrystEngComm 2010, 12, 3394. (c) Zhang,
J.; Lin, Y.; Huang, X.; Chen, X. Inorg. Chem. 2005, 44, 3146. (d) Zheng,
S.; Tong, M.; Tan, S.; Wang, Y.; Shi, J.; Tong, Y.; Lee, H.; Chen, X.
Organometallics 2001, 20, 5319.
from gas−solid reaction of HNO vapors with sample 1βb, (c) a mixture
3
of compound 1α and 1β nanoparticles prepared from solid−solid
reaction of sample 2b with KOH, and (d) compound 1β nanoparticles
prepared from gas−solid reaction of NH hydrated vapors with sample
3
2b.
(
5) (a) Kitagawa, S.; Uemura, K. Chem. Soc. Rev. 2005, 34, 109.
b) Vittal, J. J. Coord. Chem. Rev. 2007, 251, 1781. (c) Nagarathinam, M.;
Peedikakkal, A. M. P.; Vittal, J. J. Chem. Commun. 2008, 5277.
d) Nagarathinam, M.; Chanthapally, A.; Lapidus, S. H.; Stephens, P.
W.; Vittal, J. J. Chem. Commun. 2012, 48, 2585. (e) Aslani, A.; Morsali, A.
Chem. Commun. 2008, 3402. (f) Sadeghzadeh, H.; Morsali, A. Inorg.
Chem. 2009, 48, 10871. (g) Akhbari, K.; Morsali, A. CrystEngComm
(
morphologies of compound 2 with comparison to samples 1βa,
(
1
βc, and 1βd were formed. Similar results were observed in our
6,15
recent work.
As we mentioned, this transformation was not
reversible by HNO desorption, but we could obtain compound
3
1
β nanostructures from sample 2b, 2c, and 2d by solid−gas
2
(
(
011, 13, 2047.
6) (a) Ranjbar, Z. R.; Morsali, A. J. Mol. Struct. 2009, 936, 206.
b) Morsali, A.; Mahjoub, A. R. Solid State Sci. 2005, 7, 1429.
7) (a) Braga, D.; Cojazzi, G.; Emiliani, D.; Maini, L.; Grepioni, F.
reaction of these samples with hydrated vapors of NH . Solid−
3
solid reaction of compound 2 nanostructures with KOH was also
performed. Parts c and d of Figure S6 in the SI show the IR
spectra of the resulting samples from solid−solid and gas−solid
reactions of sample 2b, which are similar to the IR spectrum of
sample 1βb (Figure S6a in the SI). Parts c and d of Figure 3 show
the SEM images of a mixture of compound 1α and 1β
nanoparticles and compound 1β nanoparticles, obtained from
(
Chem. Commun. 2001, 21, 2272. (b) Braga, D.; Cojazzi, G.; Emiliani, D.;
Maini, L.; Grepioni, F. Organometallics 2002, 21, 1315. (c) Braga, D.;
Maini, L.; Mazzotti, K.; Rubini, K.; Grepioni, F. CrystEngComm 2003,
2
9, 154. (d) Braga, D.; Maini, L.; Mazzotti, K.; Rubini, K.; Masic, A.;
Gobetto, R.; Grepioni, F. Chem. Commun. 2002, 20, 2296. (e) Braga, D.;
Maini, L.; Giaffreda, S.; Grepioni, F.; Chierotti, M. R.; Gobetto, R.
Chem.Eur. J. 2004, 10, 3261.
the reaction of sample 2b with KOH and NH , respectively.
3
Similar results observed from these solid−solid and solid−gas
reactions of other 2a, 2c, and 2d samples (Figures S16−S18c,d in
the SI).
(
(
8) Wendlandt, W. W.; Hoschke, J. Nature 1962, 193, 1174.
9) Wu, H.; Dong, X.-W.; Liu, H.-Y.; Ma, J.-F. Acta Crystallogr., Sect. E
2
(
006, E62, m281.
10) (a) Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements;
In summary, solid-state structural transformation of two
polymorphs, 1α and 1β, has been observed to 2, upon solid−gas
Pergamon Press: Oxford, U.K., 1986; pp 235−236. (b) Roesky, H. W.;
Andruh, M. Coord. Chem. Rev. 2003, 236, 91.
(11) Russell, V.; Scudder, M. L.; Dance, I. G. J. Chem. Soc., Dalton
Trans. 2001, 789.
reaction of compounds 1 with HNO vapors. Solid−gas reaction
3
of compound 2 with hydrated vapors of NH forms only the 1β
3
polymorph, while solid−solid reaction of compound 2 with
KOH forms a mixture of 1α and 1β with chiral and achiral space
groups P2 2 2 and Pbcn, respectively. Probably in the presence
(
(
12) Bondi, A. J. Phys. Chem. 1964, 68, 441.
13) (a) Munakata, M.; Wu, L. P.; Kuroda-Sowa, T.; Maekawa, M.;
1
1 1
Suenaga, Y.; Ning, G. L.; Kojima, T. J. Am. Chem. Soc. 1998, 120, 8610.
b) Sneider, R.; Hosseini, M. W.; Planeix, J.-M.; Cian, A. D.; Fischer, J.
of KOH, because of its higher base strength in comparison with
(
hydrated vapors of NH , a mixture of two thermodynamically
3
Chem. Commun. 1998, 1625. (c) Andrews, L. J.; Keefer, R. M. J. Am.
Chem. Soc. 1950, 72, 5034. (d) Blake, A. J.; Baum, G.; Champness, N. R.;
Chung, S. S. M.; Cooke, P. A.; Fenske, D.; Khlobystov, A. N.;
stable (1β) and unstable (1α) products were formed. The
morphology and size of compound 2 nanostructures are different
from those of compound 1β. This phenomenon could possibly
be related to a change in color, crystal system, and space group of
compound 1β during the solid-state structural transformation to
Lemenovskii, D. A.; Li, W. S.; Schro
2000, 4285. (e) Khlobystov, A. N.; Blake, A. J.; Champness, N. R.;
Lemenovskii, D. A.; Majouga, A. G.; Zyk, N. V.; Schroder, M. Coord.
Chem. Rev. 2001, 222, 155 and references cited therein.
̈
der, M. J. Chem. Soc., Dalton Trans.
̈
1
6
compound 2.
(14) Ni, Z.; Masel, R. I. J. Am. Chem. Soc. 2006, 128, 12394.
(
15) Khanjani, S.; Morsali, A.; Retailleau, P. CrystEngComm 2010, 12,
ASSOCIATED CONTENT
Supporting Information
X-ray crystallographic data in CIF format and full synthetic and
analytical details. This material is available free of charge via the
Internet at http://pubs.acs.org.
■
2
173.
*
S
(16) Masoomi, M. Y.; Morsali, A. Coord. Chem. Rev. 2012, 256, 2921.
AUTHOR INFORMATION
Corresponding Author
E-mail: morsali_a@modares.ac.ir.
■
*
2
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