DOI: 10.1002/chem.201003274
Redox-Responsive Photochromism and Fluorescence Modulation of Two 3D
Metal–Organic Hybrids Derived from a Triamine-Based Polycarboxylate
Ligand
[
a, b]
[a]
[a]
[a]
[a]
Qi-Long Zhu,
Tian-Lu Sheng, Rui-Biao Fu, Sheng-Min Hu, Ling Chen,
[a, b] [a, b] [a]
Chao-Jun Shen,
Xiao Ma,
and Xin-Tao Wu*
Photochromism is defined as the reversible transforma-
tion of a chemical species, induced by the absorption of
electromagnetic radiation, to a form with a different vibron-
N ACHTUNGTNERGUN( CH CO H) groups in MOCs may undergo a similar elec-
2 2 2
tron-transfer process. However, no coordination polymer
constructed from ligands containing ÀN
ACHTUNGTRNEN(UG CH CO H) groups
2 2 2
[1]
[8]
ic absorption spectra. Photochromic materials have attract-
ed considerable interest owing to prospective real or poten-
tial applications in many fields, including protection (in
spectacles, photobarriers, anti-fake, and camouflage), deco-
ration, information storage, displays, optical switches, photo-
shows photochromism so far. Guo and coworkers have re-
ported the only metal-assisted LLCT photochromic MOC,
[Cd (ic)(mc)(4,4’-bipy) ]·4H O (ic=itaconate, mc=mesaco-
2
3
2
nate, bipy=bipyridine), which undergoes an interesting pho-
tochromic transformation from yellow to blue upon UV ir-
[2]
[3b]
mechanics, and so forth. Although numerous photochro-
mic families have been reported to date, those based on an
electron-transfer (redox) chemical process, especially for
radiation.
Herein, we report two photochromic MOCs
(TTHA)(4,4’-
with adjustable fluorescent intensities, [Zn CAHTUNGTRENNNUG
3
bipy)1.5
ACHTUNGTRENNUN(G H O) ]·6H O (1a) and [Zn ACHTUNGTRUNNEGN( TTHA)(4,4’-bipy) -
2 2 2 3 1.5
[3]
metal–organic complexes (MOCs), are rare. One of the
biggest challenges in photochromic MOCs without photo-
chromic organic ligands is to design photoinduced bistable
ACHTUNGTRENNUNG
(H O) ]·3H O (2a), derived from a novel triamine-based
2
2
2
polycarboxylate ligand containing the ÀN
group, 1,3,5-triazine-2,4,6-triamine hexaacetic
(H TTHA), as electron donor, although the ligand H TTHA
ACHTUNGTRNENUG( CH CO H)
2 2 2
acid
[4]
systems based on different electron-transfer mechanisms,
such as metal-centered electron transition (MC), ligand-to-
6
6
itself does not exhibit photochromism, and 4,4’-bipy as elec-
tron capturer. The photochromic mechanisms based on elec-
tron-transfer chemical processes have been verified with
direct and powerful ESR and X-ray photoelectron spectros-
copy (XPS) measurements.
Yellow needlelike crystals of 1a and prismatic crystals of
2a were obtained by the hydrothermal reactions of Zn-
AHCTUNGTRNNEUG( NO ) , H TTHA, and 4,4’-bipy in a molar ratio of 3:1:2 at
3 2 6
[5]
metal charge transfer (LMCT), metal-to-metal charge
transfer (MMCT), intraligand charge transfer (ILCT), and
ligand-to-ligand charge transfer (LLCT).
A
C
T
N
T
E
N
U
G
A
H
T
N
T
R
N
U
G
[3b]
Structurally
well-defined hybrids will give us better insight into the struc-
ture–photochromism relationships; nevertheless, few hybrids
based on transition metals have been explored with simulta-
neous characterization of their structure and photochrom-
[3,6]
ism.
1408C and 1208C for 72 h, respectively. The single-crystal
X-ray diffraction data reveal that complexes 1a and 2a are
3D networks. As shown in Figure 1 and S3 in the Supporting
Information, the 3D frameworks can be described as 2D
Chopoorian and Loeffler have discovered the electron-at-
tractive ability of a porous glass matrix indicated by the
blue radical-ion species after the irradiation with UV light,
in which an aqueous solution of p-phenylenediaminetetra-
II
6À
layers constructed of Zn ions and TTHA pillared by the
coordinated 4,4’-bipy groups.
[7]
acetic acid (p-PTDA) is absorbed. Thus, in the presence of
electron-accepting components, organic ligands containing À
The biggest difference between the structures of com-
plexes 1a and 2a is the coordination modes of the ligands
(
Scheme 1). Due to the flexibility, six of the arms show sig-
[
a] Q.-L. Zhu, Prof. T.-L. Sheng, Dr. R.-B. Fu, S.-M. Hu, Prof. L. Chen,
C.-J. Shen, X. Ma, Prof. X.-T. Wu
State Key Lab of Structural Chemistry
Fujian Institute of Research on the Structure of Matter
Chinese Academy of Science, Fuzhou
Fujian 350002 (P.R. China)
Fax : (+86)591-8371-9238
E-mail: wxt@fjirsm.ac.cn
[
b] Q.-L. Zhu, C.-J. Shen, X. Ma
Graduate School of the Chinese Academy of Sciences
Beijing, 100049 (P.R. China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201003274.
Figure 1. 2D layer (left) and 3D framework along the c axis (right) in
complex 1a.
3358
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 3358 – 3362