Organic-inorganic hybrid cyclic aggregate or 2D network assembled by silver(I) 3,5-dinitrobenzoate with 2-methylimidazole or 2-aminopyrimidine

Article abstract of DOI:10.1039/b008383f

Silver(I) 3,5-dinitrobenzoate (DNB) reacts with 2-methylimidazole (MeIm), producing a linearly coordinated [Ag(MeIm)₂]⁺ cation that is further assembled with 3,5-dinitrobenzoate anion via N-H···O hydrogen bonding to give the cyclic aggregate {([Ag(MeIm)₂](DNB)})₂ 1; whereas with 2-aminopyrimidine (APym) it affords the coordination polymer [Ag(Apym)(DNB)]_∞ 2, which is assembled into a two-dimensional network sustained by weak C-H···O hydrogen bonds.

Full text of DOI:10.1039/b008383f

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Organic–inorganic hybrid cyclic aggregate or 2D network assembled
by silver(I) 3,5-dinitrobenzoate with 2-methylimidazole or
2-aminopyrimidine
An-Wu Xu,a Cheng-Yong Su,*a Ze-Fu Zhang,b Yue-Peng Caia and Chun-Long Chena
a School of Chemistry and Chemical Engineering, Zhongshan University, Guangzhou 510275,
China. E-mail: cesscy=zsu.edu.cn
b L aboratory of Solid L ubrication, L anzhou Institute of Chemical Physics, Chinese Academy of
Sciences, L anzhou 730000, China
Received (in Montpellier, France) 2nd October 2000, Accepted 5th December 2000
First published as an Advance Article on the web 15th February 2001
Silver(I) 3,5-dinitrobenzoate (DNB) reacts with 2-methylimidazole (MeIm), producing a linearly coordinated
[Ag(MeIm) ]` cation that is further assembled with 3,5-dinitrobenzoate anion via NÈHÉ É ÉO hydrogen bonding to
2
give the cyclic aggregate M[Ag(MeIm) ](DNB)N 1; whereas with 2-aminopyrimidine (APym) it a†ords the
2
2
coordination polymer [Ag(Apym)(DNB)] 2, which is assembled into a two-dimensional network sustained by
weak CÈHÉ É ÉO hydrogen bonds.
=
The controlled design of solid-state architectures, so-called
crystal engineering, is currently recognized as one of the most
important research areas due to its close relation to bio-
mimetics, catalysis and materials science.1,2 It is also expected
to throw light upon the understanding of how molecules can
be organized and how functions can be revealed. Two main
synthetic branches have drawn much attention according to
their di†erent synthetic strategies, namely ““coordination
polymersÏÏ achieved primarily through the assembly of metal
complexes and ““organic solidsÏÏ formed from the assembly of
organic molecules or ions.3h5 The versatile metalÈligand
bonds promote quick growth of inorganic crystal engineer-
ing,6 while the variety of intermolecular forces, such as
halogenÉ É Éhalogen, NÉ É Éhalogen, SÉ É ÉS, pÉ É Ép contacts and
various types of weak hydrogen bonds (CÈHÉ É ÉO, CÈHÉ É ÉN,
OÈHÉ É Ép, CÈHÉ É Ép), in contrast to the traditional hydrogen
bonds (XÈHÉ É ÉY; X, Y \ F, O and N), play important roles in
the construction of ordered organic networks.7 Recently, a
combination of the two aforementioned strategies has become
increasingly prominent due to easier access to unique struc-
tures and properties not readily available in individual inorga-
nic or organic solids.
This new strategy often relies on the deliberate selection of
ligands that can simultaneously coordinate metal ions and
provide potential intermolecular interaction sites.8h10 The
angular disposition of N atoms in pyrimidine has led to the
formation of various supramolecular isomers in its metal
complexes11,12 in which discrete macrocycles, 1D, 2D and 3D
architectures have been generated. 2-Aminopyrimidine was
selected here because of its potential amino donor besides the
two exodentate imino nitrogen atoms.13 Similarly, the imid-
azolate anion, easily obtained by deprotonation of imidazole,
is capable of acting as a bridging ligand. The 1,3-arrangement
of the nitrogen atoms imposes geometrical constraints such
that only one imidazolate bridge is possible between two
metal centers. Accordingly, imidazolate-bridged transition
metal complexes show higher linearity14 and many oligomeric
and polymeric complexes have been fabricated,15h18 though
few of them are silver(I)-containing and only a handful of
single crystal structures determined.19h21 On the other hand,
non-deprotonated imidazole itself is monodentate and is
found to linearly coordinate to silver(I) ions in
bis(imidazole)silver(I) nitrate.22 Interestingly, a novel Ag
6
cluster has been obtained from reaction of silver(I) perchlorate
and imidazole in which no other bridging force but AgÉ É ÉAg
contacts contributes to clustering.23 We are interested in uti-
lizing the potential hydrogen bond donor NH group, and in
this paper, e†orts are focused on the assembly of organicÈ
inorganic hybrid aggregates following the above-mentioned
new strategy. A cyclic aggregate and a two-dimensional
network have been constructed from 2-methylimidazole and
2-aminopyrimidine ligands of somewhat similar donor
arrangements with silver(I) 3,5-dinitrobenzoate, suggesting dif-
ferent crystal engineering assembly pathways from di†erent
intermolecular interactions.
Experimental
Materials and methods
All starting materials were reagent grade obtained from com-
mercial sources and used without further puriÐcation. Silver(I)
3,5-dinitrobenzoate was prepared from reaction of silver(I)
nitrate with 3,5-dinitrobenzoic acid. The elemental analyses
for C, H and N were carried out with a Varian EL elemental
analyzer. 1H NMR spectra were measured on a Varian
INOAN 500 instrument using DMSO-d as solvent with TMS
6
as internal standard at room temperature.
Preparation
{ [Ag(MeIm) ](DNB)} Æ H O, 1 Æ H O.
A
solution of
2
2
2
2
silver(I) 3,5-dinitrobenzoate (0.32 g, 1 mmol) in MeCN (5 cm3)
was added to a stirred solution of 2-methylimdazole (0.16 g, 2
mmol) in MeOH (2 cm3). The resulting mixture was Ðltered
and slow di†usion of diethyl ether for 24 h produced pale
yellow prismatic crystals, which were collected by Ðltration,
washed with MeCN and MeOH and dried in a vacuum desic-
cator over silica gel. Yield: 60%. Elem. anal. found: C, 36.46;
H, 3.55; N, 17.22; calc. for C
3.28; N, 17.07%. 1H NMR (500 MHz, DMSO-d ): d 2.45 (6H,
H N Ag O : C, 36.60; H,
30 32 12
2 13
6
DOI: 10.1039/b008383f
New J. Chem., 2001, 25, 479È482
479
This journal is ( The Royal Society of Chemistry and the Centre National de la Recherche ScientiÐque 2001

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Table 1 Crystallographic data for complexes 1 and 2
by direct methods and reÐned by full-matrix least-squares
against F2 of all data using SHELXTL software.25 Aniso-
tropical thermal factors were assigned to all of the non-
hydrogen atoms while the hydrogen atoms were included in
the calculations isotropically but not reÐned. A summary of
parameters for the data collections and reÐnements is given in
Table 1. Selected bond distances and bond angles are listed in
Tables 2 and 3.
1
2
Formula
Formula weight
C
984.42
H
N
O
Ag
C H N O Ag
11
414.09
30 32 12 13
2
8 5 6
Crystal system
Space group
Triclinic
P1
Monoclinic
P2(1)/c
a/A
b/A
c/A
a/¡
8.9218(11)
11.9058(14)
18.795(2)
71.592(2)
76.372(2)
88.482(2)
1838.4(4)
2
9.038(6)
6.373(3)
23.946(16)
CCDC reference number 440/250. See http://www.rsc.org/
suppdata/nj/b0/b008383f/ for crystallographic Ðles in .cif
format.
b/¡
c/¡
100.79(2)
U/A
Ž
3
1354.9(14)
4
Z
k/mm~1
1.147
293(2)
9809
1.531
293(2)
2396
Results and discussion
T /K
Unique reÑections
Observed reÑections
Single-crystal X-ray analysis reveals that the complex 1 É H O
2
consists of two [Ag(MeIm) ]` cations, two 3,5-dinitro-
2
I [ 2p(I)
6621
0.0318
0.0784
1457
0.0494
0.0927
benzoate anions and one water molecule. Each silver(I) ion is
Ra
wRb
coordinated to two imino nitrogen atoms of two monodentate
2-methylimidazole ligands, showing four similar AgÈN bonds
[Ag1ÈN3 2.1139(18), Ag1ÈN1 2.1194(19), Ag2ÈN7 2.1211(19),
Ag2ÈN5 2.1239(18), average 2.1196 A], which are slightly
longer than those in the [Ag(imidazole) ](ClO ) complex
(2.082 A)23 but shorter than those in other heterocyclic
nitrogen coordination complexes (AgÈN 2.135,
a R \ &( o F o [ o F o )/& o F o. b wR \ [M&w(F2 [ F2)2/&w(F2)2N1@2.
o
c
o
o
c
o
2
4
methyl), 7.07 (4H, imidazole), 8.79 (1H, NDB ) and 8.91 (2H,
4H
NDB
).
pyridine
2.263È2.444 A).26h28 The
2, 6H
AgÈN
benzimidazole
2.184, AgÈN
quinoline
NÈAgÈN angles [N3ÈAg1ÈN1 161.37(8)¡, N7ÈAg2ÈN5
159.94(8)¡] deviate from linearity, indicating that the coordi-
nation geometry of the silver(I) ion may be best described as
bent.12 The 3,5-dinitrobenzoate anion does not directly bind
to silver(I) but is involved in the formation of intermolecular
interactions through its acetate group. As shown in Fig. 1,
each 3,5-dinitrobenzoate anion forms two NÈHÉ É ÉO acceptor
hydrogen bonds with the NH groups of 2-methylimidazole
[Ag(Apym)(DNB)] , 2. This was prepared in a similar
=
way using the procedure described for complex 1 with 2-
aminopyrimidine (0.19 g,
2
mmol) instead of 2-
methylimidazole. Yield: 65%. Elem. anal. found: C, 31.66; H,
1.87; N, 17.21; calc. for C H N AgO : C, 31.91; H, 1.95; N,
16.91%.
11
8
5
6
X-Ray crystallographic studies
belonging to two di†erent [Ag(MeIm) ]` cations, thus
assembling two [Ag(MeIm) ]` cations and two 3,5-dinitro-
benzoate anions into
2
The di†raction intensities of complex 1 É H O were collected
(hemisphere technique) on a Bruker SMART 1K di†ractome-
2
2
a
neutral four-component ring
ter with a CCD area detector. Absorption corrections were
performed using the SADABS program.24 Data collection for
2 was performed on a Siemens R3m four-circle di†ractometer.
An empirical absorption correction based on psi scans of
several reÑections was applied. All the structures were solved
structure29 in which four NÈHÉ É ÉO hydrogen bonds are
involved (N2ÈH2É É ÉO11, N6ÈH6É É ÉO5, N4ÈH4É É ÉO6 and
N8ÈH8É É ÉO12). In addition, the solvate water molecules form
weak OÈHÉ É ÉO donor hydrogen bonds with the O5 atom of
one 3,5-dinitrobenzoate anion [O1WÉ É ÉO5 2.956(3) A, O1WÈ
H1WÉ É ÉO5 174.0¡] and the O6a atom of another anion
belonging to the adjacent cyclic aggregate [O1WÉ É ÉO6a
2.880(3), A, O1WÈH2WÉ É ÉO6 174.2¡], linking two such cyclic
aggregates to form a hydrogen bonded dimer. The shortest
silver(I) ion separation between two molecules is 4.837 A, indi-
cating no AgÉ É ÉAg interaction.
As shown in Fig. 2, complex 2 is a one-dimensional stair-
case polymer linked by 1,3-bridging 2-aminopyrimidine mol-
ecules. The silver(I) ion is three coordinated by one oxygen
atom of the 3,5-dinitrobenzoate anion and two nitrogen atoms
belonging to two 2-aminopyrimidine ligands. The AgÈN
Table 2 Selected bond distances (A) and angles (¡) for complex 1.
Symmetry transformation used to generate equivalent atoms: (a)
2 [ x, 1 [ y, [z
Ag1ÈN3
2.1139(18)
2.1211(19)
2.742(3)
2.767(2)
2.956(3)
161.37(8)
165.9
Ag1ÈN1
2.1194(19)
2.1239(18)
2.768(3)
2.703(2)
2.880(3)
159.94(8)
171.7
Ag2ÈN7
Ag2ÈN5
N2É É ÉO11
N4É É ÉO6
O1WÉ É ÉO5
N3ÈAg1ÈN1
N2ÈH2É É ÉO11
N8ÈH8É É ÉO12
O1WÈH1WÉ É ÉO5
N6É É ÉO5
N8É É ÉO12
O1WÉ É ÉO6a
N7ÈAg2ÈN5
N4ÈH4É É ÉO6
N6ÈH6É É ÉO5
O1WÈH2WÉ É ÉO6a
173.3
174.0
167.5
174.2
Table 3 Selected bond distances (A) and angles (¡) for complex 2.
Symmetry transformations used to generate equivalent atoms: (a) x,
y [ 1, z; (b) 1 [ x, 1 [ y, 2 [ z ; (c) 1 ] x, 1/2 [ y, 1/2 ] z; (d) 1 ] x,
3/2 [ y, 1/2 ] z
Ag1ÈN4a
2.215(5)
2.363(5)
3.379(6)
132.37(18)
98.79(18)
82.71(16)
146.5
Ag1ÈO1
2.274(4)
2.658(5)
3.363(6)
121.50(17)
117.03(18)
91.91(18),
147.7
Ag1ÈN3
Ag1ÈN5b
C8É É ÉO3
C10É É ÉO3
N4aÈAg1ÈO1
O1ÈAg1ÈN3
O1ÈAg1ÈN5b
C8ÈH8aÉ É ÉO3c
N4aÈAg1ÈN3
N4aÈAg1ÈN5b
N3ÈAg1ÈN5b
C10ÈH10aÈO3d
Fig. 1 The neutral cyclic aggregate M[Ag(MeIm) ](NDB)N in 1
2
2
linked via NÈHÉ É ÉO hydrogen bonding.
480
New J. Chem., 2001, 25, 479È482

View Article Online
anions by NÈHÉ É ÉO hydrogen bonds, while in 2 a one-
dimensional coordination polymer is formed via amino-
pyrimidine bridging. The 3,5-dinitrobenzoate anion behaves
as a versatile connector: in 1 É H O only the CO groups are
2
2
involved in intermolecular interactions, while in 2 one of the
NO groups is engaged in CÈHÉ É ÉO hydrogen bonding and
the CO group is weakly bonded to the silver(I) ion. This dif-
ference is obviously related to the di†erent donating behaviors
2
2
of methylimidazole and aminopyrimidine mentioned above:
in 1 the uncoordinated NH groups of the [Ag(MeIm) ]`
2
cation make it possible to form NÈHÉ É ÉO hydrogen bonds
with the acetate group of dinitrobenzoate anions, therefore
generating a ring structure. But in 2 aminopyrimidine acts as
a bridging ligand to connect two Ag(I) ions, so the dinitoben-
zoate anion prefers to interact with the Ag(I) ion via its acetate
group and to form intramolecular NÈHÉ É ÉO hydrogen bonds
with the NH group [N5É É ÉO1a 2.913(4), N5É É ÉO2 2.903(4)
A].
Fig. 2 Extended 1D coordination polymer [Ag(APym)(DNB)] in 2
2
=
bridged by 2-aminopyrimidine.
In summary, assembly of an organicÈinorganic hybrid
cyclic aggregate and a two-dimensional network have been
investigated by selecting the same silver(I) 3,5-dinitrobenzoate
moiety and comparable 2-methylimdazole and 2-
aminopyrimidine ligands. The di†erent intermolecular inter-
actions play an important role in the assembly process and
the Ðnal structures are controlled by the donating behaviors
of the ligands. This may be an example for the creation of
ordered solid materials by utilizing coordination bonds as well
as various intermolecular interactions, based on the strategy
incorporating both techniques used in organic and inorganic
systems.
bonds [Ag1ÈN4 2.215(5), Ag1ÈN3 2.363(5) A] are somewhat
longer than those in 1, while the AgÈO bond [Ag1ÈO1
2.274(4) A] is comparable with those in nitrate coordination
complexes.27,28 It is interesting that two of the ring pyrim-
idine hydrogen atoms are engaged in CÈHÉ É ÉO hydrogen
bonding with the O3 atom belonging to the neighboring co-
ordination polymer. The ordered two-dimensional network is
thus assembled as shown in Fig. 3. The topology of the
network can be simpliÐed to regard Apym as a four-
connecting node, with DNB and the Ag(I) as three-connecting
nodes. Therefore, two pyrimidine rings are connected by two
AgÈN coordination bonds and two CÈHÉ É ÉO hydrogen bonds
to compose a tetragon. Such tetragons share vertices to form
one-dimensional arrays that are further linked by 3,5-dinitro-
benzoate anions through the remaining vertices. So the
network is composed of equal numbers of tetragons sharing
Acknowledgements
This work was supported by National Natural Science
Foundation of China and Natural Science Foundation of
Guangdong Province.
vertices and hexagons sharing edges with tetragons. The NH
group of 2-aminopyrimidine in 2 is not involved in coordi-
2
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