Studies on new strategies for the synthesis of oligomeric 1,2,3-triazoles

Article abstract of DOI:10.1016/j.inoche.2006.03.019

Conjugated tetra-1,2,3-triazoles were synthesized by the coupling reaction of terminal alkynes. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1016/j.inoche.2006.03.019

Inorganic Chemistry Communications 9 (2006) 645–648
www.elsevier.com/locate/inoche
Structural characterization and luminescence behavior of a 2D silver
(I) coordination polymer assembled from
pyridine-2,6-dicarboxylic acid N-oxide
*
Wei-Ping Wu, Yao-Yu Wang , Cui-Juan Wang, Ya-Pan Wu, Ping Liu, Qi-Zhen Shi
Department of Chemistry, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Northwest University, Xi’an, Shaanxi 710069, PR China
Received 20 February 2006; accepted 21 March 2006
Available online 25 April 2006
Abstract
A 2D network complex [Ag2(pydco)]n (1) (pydco = pyridine-2,6-dicarboxylic acid N-oxide) was synthesized and structurally charac-
terized. Fluorescence spectrum of complex 1 and the free ligand indicates that the cooperative association of Ag–Ag contacts and the
intraligand (p–p*) interactions lead to the unusual intense fluorescent emission upon photoexcitation.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: Coordination polymer; Ag–Ag contacts; Silver strings; Fluorescence spectrum; X-ray structure
Design and synthesis of inorganic-organic composite
coordination polymers exhibiting novel structures and
properties have provided exciting new prospects [1,2]. In
principle, some control over network topology can be
gained by judicious selection of reaction-influencing fac-
tors, such as the chemical structure of the organic spacers
(ligands), the coordination geometry preference of the
metal, the inorganic counterions, and the metal-to-ligand
ratio [3].
Pyridine-2,6-dicarboxylic acid N-oxide (pydco) (Chart
1)a has limited steric hindrance and weak stacking interac-
tions and can offer possibilities to form coordination poly-
mers through a carboxylate and N-oxide bridge, which is a
far better electron donor than the ring nitrogen atom of
pyridine-2,6-dicarboxylic acid [4,5]. Although recently
Meng and his co-workers have reported some d10 metal-
organic framework structures assembled from it [5], its
coordination chemistry has not been well explored [5–7].
Therefore, much more work is required to extend our
knowledge of the ligand’s coordination behavior and its
coordination polymers’ properties. On the other hand, sil-
ver(I). Salts are often used in forming supramolecular
architectures because silver(I) is a labile coordination cen-
ter and can easily form complexes with coordination num-
bers of 2, 3, or 4 and even more as needed to form many
different architectures [8]. Moreover, the potential Ag–Ag
interactions can affect the structures and properties of the
resulting coordination polymers [9]. Herein, we report the
synthesis, X-ray single crystal structure and luminescent
property of a strong fluorescent emission silver(I). Coordi-
nation polymeric complex [Ag2(pydco)]n (1), containing 1D
infinite silver strings constructed by Ag–Ag contacts in it.
Aqueous and CH3OH mixed solution of Na2(pydco)
layered upon an aqueous solution of AgAc (Ac =
CH3COOÀ) at room temperature yielded colorless crystals
[10]. The compound is stable in light and is insoluble in
common solvents except water. The crystallographic stud-
ies revealed that complex 1 exists in the solid state as a
2D polymer [11]. Fig. 1 depicts the coordination environ-
ment around Ag(I). There are two kinds of Ag(I) atoms
in 1. The first Ag(I) center (Ag2H) exhibits a distorted
tetrahedral coordination environment formed by two oxy-
gen atoms from two different pydco ligands’ carboxylate
and two oxygen donors from the third ligand that is a
*
Corresponding author. Tel.: +86 29 88303097; fax: +86 29 88303798.
E-mail address: wyaoyu@nwu.edu.cn (Y.-Y. Wang).
1387-7003/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2006.03.019

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W.-P. Wu et al. / Inorganic Chemistry Communications 9 (2006) 645–648
ond carboxlate adopting l1, 1, 1-O mode bridging three
Ag(I), the other two monodentates. So each ligand links
seven silver ions (Chart 1)b. To this end, there are tetranu-
clear units in 1 and each unit contains a 12-membered met-
allorganic cycle which is composed of two pydco and two
silver atoms, each cycle was linked through pyridyl
N-oxide groups to form 1D chain (Fig. 2). Furthermore,
bridging oxygen atoms of pydco extended adjacent chains
through coordinating to the silver(I) of the tetranuclear
units to generate a 2D coordination polymer (Fig. 2 and
3). However, the 3D supramolecular structure is formed
via p–p interactions of the pyridine rings of ligands
(edge-to-face distances of the adjacent pyridine rings are
˚
3.576 and 3.713 A and angles are the same as 79.26°).
It is worthwhile to point out that in this 2D coordina-
tion polymer, there are two kinds of short ligand-supported
˚
Ag–Ag contacts (Ag1H–Ag1H = 2.981 A, Ag1J–Ag2H =
˚
3.314 A) as they all below the van der Waals diameter of
˚
silver (3.44 A) [15]. Interestingly, silver ions are linked into
1D infinite silver strings (Ag1H–Ag2H–Ag1J–Ag2J) via
two kinds of alterative Ag–Ag interactions. These silver
strings probably intensify the links from 1D chain to 2D
network. Ag Á Á Á Ag distances of adjacent silver strings
Chart 1. (a) Pydco; (b) coordination mode of pydco ligand in complex 1.
˚
(3.597 and 3.625 A) are slightly longer than the van der
Waals diameter of silver, so they lack inter-string Ag–Ag
interactions.
2D fluorescence spectroscopy of complex 1 in the solid
state at room temperature was investigated as shown in
Fig. 4. There is a very strong emission band in range of
Fig. 1. View of Ag(I) coordination environment and 2D molecular
structure of complex 1, H atoms are omitted for clarity.
carboxylate oxygen atom and the N-oxide. The Ag–O
˚
bond lengths range from 2.287(3) to 2.552(4) A, and O–
Ag–O bond angles range from 78.25(10) to 147.26(11)°.
The second Ag(I) center (Ag1J) adopts a {AgO5} coordina-
tion sphere, which consists of four carboxylate O-donor
from four different ligands and one O-donor from a
N-oxide group. Although similar coordination spheres
{AgN5}, {AgN2O3} have been found in schiff-base com-
plexes and others such as {AgN4O},{AgN2S3} [3a,12,13],
to the best our knowledge, {AgO5} coordination fashion
based on organic aromatic polycarboxylate ligands has
not been reported, All the Ag–O bond lengths are close
to the first one, excepting one that is Ag(1J)–O(2AE)
Fig. 2. View of the 1D chain in 2D network of 1 in ab plane.
˚
(2.652(3) A) is longer than the others but resembles those
were found in other silver(I) complexes [3a,14], and
O–Ag–O bond angles range from 74.25(10) to 160.28(7)°.
The N-oxide group of all pydco exhibit bridging coordi-
nation mode, while carboxylate group is coordinated to Ag
atoms in an unprecedented coordination fashion, different
from the monodentate mode in previous reports [5–7]. That
is within a pydco ligand, an oxygen atom exhibiting l1, 1-O
mode bridging two Ag(I), while an oxygen atom of the sec-
Fig. 3. Packing view of 1 along the b-axis. Green = Ag, blue = N,
red = O, gray = C.

W.-P. Wu et al. / Inorganic Chemistry Communications 9 (2006) 645–648
647
Fig. 4. 2D fluorescence spectrum of complex 1 in the solid state at room temperature.
374–421 nm upon photoexcitation from about 230 to
255 nm. There are also relatively weak emission at about
454 and 473 nm (excitation wavelength: 211 nm). Accord-
ing to the literatures, complexes with Ag–Ag interactions
show emission in similar energy [3a,16–18]. Experimental
and theoretical results have proved that Ag–Ag interaction
is significant for the formation of luminescent species
[16,19]. Interestingly, similar emissions are observed for
the free pydco at 398 nm (kEx = 260 nm) (Fig. 5) and other
d10 metal-organic framework structures from pydco [5].
Complex 1 significantly intensifies the emission intensity
of the free pydco (almost decuple), and displays a very
strong fluorescent emission bands. The unusual strong
emission of 1 maybe indicate that the cooperative associa-
tion of the intraligand (p–p*) fluorescent emission and the
existence of Ag–Ag interactions.
In conclusion, we have demonstrated here a luminescent
silver(I) complexes with fluorescent pydco. Both pydco and
silver ions display an interesting coordination fashion, and
two kinds of alterative Ag–Ag interactions link Ag(I) ions
into 1D infinite silver strings in the 2D network.
Acknowledgements
This work was supported by the National Natural Sci-
ence Foundation of China (Grant No. 20471048) and
TRAPOYT.
Appendix A. Supplementary material
Crystallographic data for the complex 1 have been
deposited at the Cambridge Crystallographic Data Center
as supplementary publications (CCDC-294847). These
data can be obtained free of charge at www.ccdc.cam.a-
c.uk/conts/retrieving.html [or from the Cambridge Crystal-
lographic Data Center, 12, Union Road, Cambridge CB2
1EZ, UK; fax: (internet) +44 1223/336 033; e-mail: depos-
it@ccdc.cam.ac.uk]. Supplementary data associated with
this article can be found, in the online version, at
doi:10.1016/j.inoche.2006.03.019.
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