Framework Assembly Engineering. Effects of Nitro Groups on Assemblies of Phenyldicarboxylates

Article abstract of DOI:10.1246/cl.2003.1010

A novel 2-D complex [Cu(nbdc)(phen)(H₂O)] (nbdc = 2-nitro-1,4-benzenedicarboxylate dianion and phen = 1,10-phenanthroline) has been synthesized and structurally characterized by single crystal X-ray analysis. It exhibits nice fluorescent property. The modifying group plays a key role in the assembly of the framework.

Full text of DOI:10.1246/cl.2003.1010

1010
Chemistry Letters Vol.32, No.11 (2003)
Framework Assembly Engineering. Effects of Nitro Groups on Assemblies of Phenyldicarboxylates
Ai-Qing Ma,y Zhan Shi,yy Ru-Ren Xu,y;yy Wen-Qin Pang,y;yy and Long-Guan ZhuÃy
yDepartment of Chemistry, Zhejiang University, Hangzhou 310027, P. R. China
yyState Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University,
Changchun 130023, P. R. China
(Received July 31, 2003; CL-030704)
A novel 2-D complex [Cu(nbdc)(phen)(H2O)] (nbdc = 2-ni-
tro-1,4-benzenedicarboxylate dianion and phen = 1,10-phenan-
throline) has been synthesized and structurally characterized by
single crystal X-ray analysis. It exhibits nice fluorescent proper-
ty. The modifying group plays a key role in the assembly of the
framework.
Design and construction of novel or given frameworks anal-
ogous to important minerals such as zeolite, clay, and quartz us-
ing phenyldicarboxylates are of much current interest.1 Recent-
Figure 1. ORTEP view of complex {[Cu(nbdc)(phen)](H2O)}n;
ly, much attention has been focused on the use of 1,4-
ꢀ
ꢀ
selected bond lengths and angles (A, ):Cu(1)–O(1) 2.390(3),
Cu(1)–O(1A) 1.964(2), Cu(1)–O(5) 1.957(3), Cu(1)–N(3)
2.012(3), Cu(1)–N(4) 2.014(3), O(1)–Cu(1)–O(5) 87.46(11),
O(1)–Cu(1)–O(1A) 76.58(11), O(1)–Cu(1)–N(3) 98.94(12),
O(1)–Cu(1)–N(4) 108.35(11), O(5)–Cu(1)–O(1A) 89.47(12),
N(3)–Cu(1)–N(4) 81.85(13).
benzenedicarboxylic acid (H2bdc) while limited researches were
devoted to substituted 1,4-benzenedicarboxylic acid (H2sbdc).2
Several reports have shown that the framework or functionality
could be tuned by pending groups of phenyldicarboxylates be-
cause the angle of two carboxylates of 1,4-benzenedicarboxylate
is directly related to the size and nature of substituents on the
phenyl ring.3 Moreover, the pending group of phenyldicarboxy-
lates may act as the third coordinate site and further form novel
networks. Therefore, H2sbdc may offer some novel structural
and functional interests, for example, the methane adsorption
ability of complex Zn4O(cbdc)3 (cyclobutyl-1,4-benzenedicar-
boxylic acid, H2cbdc) is significantly larger than that of
Zn4O(bdc)3 although the latter has larger porosity. The pending
group of cyclobutyl of cbdc may tune the framework so that nice
Each of the two carboxyl groups in ꢀ4-nbdc offers a mono-
atomic bridge by using one oxygen atom as the asymmetric
ꢀ-O bridge bound to two copperII ions in apical and basal posi-
tions. The oxygen bridging spacers form a four-membered ring,
[Cu2O2] second building unit (SBU), which is a basic unit, ex-
tend the structure into 1-D and 2-D networks (Figure 2). As ex-
pected, [Cu2(ꢀ4-nbdc)] units consist of a 1-D chain with SBUs
of [Cu2O2] and the separation of CuÁ Á ÁCu in SBU [Cu2O2] is
methane adsorption could be achieved.3c The system of Cu2þ
/
ꢀ
3.428 A. The separations of CuÁ Á ÁCu through ꢀ4-nbdc are
ꢀ
11.073 and 8.729 A, respectively. The short distance of CuÁ Á ÁCu
phenanthroline/H2bdc has been raised much interest due to
magnetic and fluorescent properties and at least five species have
been synthesized while the frameworks of complexes are only
limited in dimer or 1-D networks,4 in which bdc is a bis-mono-
dentate ligand and shows common coordination topology. Con-
sidering the functionality of the pending group of substituent
phenyldicarboxylates, we have chosen 2-nitro-1,4-benzenedi-
carboxylic acid (H2nbdc) to construct new frameworks. In this
paper we report the novel 2-D structure assembled by H2nbdc
with nitro substituent, {[Cu(nbdc)(phen)](H2O)}n (1).
separated by nbdc is extremely rare only found in mono-atomic
bridge cases and corresponding separations of CuÁ Á ÁCu in com-
7
ꢀ
plex Cu2(trans-oxen)(bdc)Á2H2O (2) are 10.987 and 9.672 A,
respectively. The bis-monodentate nbdc bridging linkers con-
nect one-dimensional chains of [Cu2(ꢀ4-nbdc)] via four-mem-
bered ring units of [Cu2O2] into 2-D framework. The separation
ꢀ
of CuÁ Á ÁCu by bis-monodentate nbdc is 10.989 A. It is obvious
The compound of 1 was synthesized by hydrothermal reac-
tion of copper chloride, 2-nitro-1,4-benzenedicarboxylic acid,
and 1,10-phenanthroline in water.5 The single crystal X-ray
analysis revealed that the complex consists of 2-D structure.6
The copper atom displays square pyramidal geometry, which
is completed by two nitrogen atoms from one 1,10-phenan-
throline, three carboxylate oxygen atoms from three nbdc li-
gands (Figure 1). The O(1) is sitting on the apical position
Ã
ꢀ
(Cu(1)–O(1) = 2.390(3) A) while O(5), O(1 ), N(3), and N(4)
occupy the basal plane. There are two kinds of nbdc coordination
modes in complex 1. One mode is bis-monodentate while anoth-
er is bis-mono-atomic bridge mode.
Figure 2. A view of 2-D network constructed by nbdc ligands.
The nitro groups are omitted for clarity.
The bis-mono-atomic bridge mode is extremely sparse.7
Copyright Ó 2003 The Chemical Society of Japan

Chemistry Letters Vol.32, No.11 (2003)
1011
References and Notes
1
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1415 (2000).
Prepartion of compound 1. A mixture of CuCl2Á2H2O
(0.0352 g, 0.2 mmol), 2-nitro-1,4-benzenedicarboxylic acid
(H2nbdc, 0.0452 g, 0.2 mmol), 1,10-phenanthroline (0.0301 g,
0.15 mmol) and H2O (8 mL) in the molar ratio ca.
1:1:0.74:2151 was sealed in a 25 mL stainless-steel reactor
with Teflon liner and was heated at 150 ꢀC for 3 h. After cool-
ing, deep blue crystals of 1 were collected by filtration. Yield:
87%. Anal. calcd. for C20H13CuN3O7: C, 51.02; H, 2.78; N,
8.92%; found: C, 51.22; H, 2.56; N, 8.84%. IR (KBr, cmÀ1):
1638 (s), 1609 (s), 1522 (m), 1489 (m), 1431 (m), 1364 (s),
1341 (s), 1250(m), 1151 (w), 854 (m), 722 (m), 649 (w),
513 (w). Thermogravimetric analysis of 1 shows that in the
range 100 to 180 ꢀC, weight loss is 4.1% (calcd: 3.8%), which
corresponds to the loss of one water molecule. The residue is
CuO at 655 ꢀC (found: 15.2%, calcd: 16.9%).
Figure 3. A view of 3-D hydrogen bonding network.
that the 2-D network consists of, in nature, [Cu2O2 + nbdc]4
building blocks. The basic unit in 2-D is a grid of [Cu4(ꢀ4-
ꢀ
nbdc)2(ꢀ2-nbdc)2] with dimensions ca. 9:4 Â 11:3 A. The as-
sembly of the novel 2-D coordination network is attributed to
the nitro group through steric and electric effects.
The 2-D network of [Cu2(ꢀ4-nbdc)(ꢀ2-nbdc)]n is created
without phenanthroline linking. It seems that the phenanthroline
is not necessary in the synthetic viewpoint. However, it could be
necessary in the construction of network because the phenan-
throline can complete the geometry of the copper atom. The wa-
ter molecules between the 2-D sheets form hydrogen bonds with
the uncoordinating carboxyl oxygen atoms of ꢀ4-nbdc and ꢀ2-
nbdc from neighboring 2-D layer to hold nets together and build
up the 3-D framework (Figure 3).
4
As mentioned in complexes of [Cu(bdc)(phen)] (3)4c and
Cu2(trans-oxen)(bdc)Á2H2O, bis-monodentate bdc ligands lead
to a 1-D zig-zag chain structure of 3 and ꢀ4-bdc ligands creat
1-D chain of 2 although oxen ligands further extend the structure
into 2-D framework. Obviously complex 1 combines the charac-
teristics in both 2 and 3 and creates a novel 2-D framework,
which is attributed to the effect of nitro group. The successful
syntheses of complexes 1 and 2 suggest that 2-D structure for
complex [Cu(bdc)(phen)] could be achieved at suitable micro
synthetic environment (equivalent to the effect of nitro group,
such as in 2) although many efforts have been done.
The UV–vis spectrum of 1 exhibits three high-energy ab-
sorptions at 191, 222, and 299 nm in the solid state; the latter
can be assigned to ligand-to-metal charge transfer. An intense
fluorescent emission of 1 at 453 nm (ꢁex ¼ 230 nm) was ob-
served in the solid state at room temperature and is assigned to
the ligand-to-metal charge transfer band and some ꢂ-donations
from the cooperation of 1,10-phenanthroline and nbdc ligands.
This information suggests that 1 might be an excellent candidate
for potential photoactive material.
5
6
X-ray crystal structure determination of 1: A deep blue crystal
having the size of 0:24 Â 0:32 Â 0:55 mm was mounted on a
glass fiber and data collection was done on a Bruker SMART
CCD diffractometer using graphite-monochromated Mo Kꢃ
In summary, we have successfully synthesized a novel 2-D
compound [Cu(nbdc)(phen)](H2O) constructed from 2-nitro-
1,4-benzendicarboxylic acid and 1,10-phenanthroline with nice
fluorescent property. Combination of ꢀ4-nbdc and ꢀ2-nbdc
leads to new assembly of benzenedicarboxylates, which may
be of great benefit for designing and controlling the frameworks
constructed from benzenedicarboxylates.
ꢀ
radiation (ꢁ ¼ 0:71073 A) at room temperature. The structure
was solved by direct methods and successive Fourier syntheses
using SHELXS-97. The structure was refined by full-matrix
least-squares techniques using SHELXL-97. Crystal data for
ꢁ
1: C20H13CuN3O7, M ¼ 470:87, triclinic, P1, a ¼ 9:3623ð4Þ,
ꢀ
b ¼ 10:7706ð5Þ, c ¼ 11:2802ð5Þ A, ꢃ ¼ 61:691ð2Þ, ꢄ ¼
ꢀ
ꢀ 3
88:440ð2Þ, ꢅ ¼ 70:695ð2Þ , V ¼ 933:56ð7Þ A , Z ¼ 2, Dc ¼
1:675 gÁcmÀ3, ꢀ ¼ 1:222 mmÀ1, R1 ¼ 0:0537 and wR2 ¼
This work was supported by the National Natural Science
Foundation of China under grant No. 50073019 and the State
Key Laboratory of Inorganic Synthesis and Preparative Chemis-
try, P. R. China.
0:1507. CCDC number is 211902.
7
H. X. Zhang, B. S. Kang, A. W. Xu, Z. N. Chen, Z. Y. Zhou, A.
S. C. Chan, K. B. Yu, and C. Ren, J. Chem. Soc., Dalton
Trans., 2001, 2559.
Published on the web (Advance View) October 6, 2003; DOI 10.1246/cl.2003.1010