In-air structural transformation observed from the synthesis of a new mixed-ligand coordination polymer

Article abstract of DOI:10.1016/j.inoche.2003.09.023

A new mixed-ligand coordination polymer, {[Cu(BDC)(Phen)(H ₂O)]·(H₂O)(DMF)}_n 1 (BDC = 1,4-benzenedicarboxylate; Phen = 1,10-phenanthroline) has been synthesized and characterized. It was found that the complex 1, crystallized in orthorhombic crystal system, was transformed into a more stable compound due to the evaporation of inclusion solvents in air, {[Cu(BDC)(Phen)(H₂O)] 2, and the complex 2 was characterized in triclinic crystal system. Complex 1: space group Pnma with unit cell dimensions a = 23.378(2), b = 12.830(1) and c = 6.984(1) A?, Z = 4. Complex 2: space group P1? with unit cell dimensions a = 9.004(1), b = 10.527(1) and c = 10.577(1) A?, α = 114.779(1), β = 92.246(1), γ = 114.746(1), Z = 2.

Full text of DOI:10.1016/j.inoche.2003.09.023

Inorganic Chemistry Communications 7 (2004) 94–96
www.elsevier.com/locate/inoche
In-air structural transformation observed from the synthesis
of a new mixed-ligand coordination polymer
a,
a
b,
*
Long-Guan Zhu *, Hong-Ping Xiao , Jack Y. Lu
a
Department of Chemistry, Zhejiang University, Hangzhou 310027, China
b
Department of Chemistry, University of Houston-Clear Lake, 2700 Bay Area Blvd, Houston, TX 77058, USA
Received 30 June 2003; accepted 4 September 2003
Published online: 14 November 2003
Abstract
A new mixed-ligand coordination polymer, {[Cu(BDC)(Phen)(H2O)] ꢀ (H2O)(DMF)}n 1 (BDC ¼ 1,4-benzenedicarboxylate;
Phen ¼ 1,10-phenanthroline) has been synthesized and characterized. It was found that the complex 1, crystallized in orthorhombic
crystal system, was transformed into a more stable compound due to the evaporation of inclusion solvents in air,
{[Cu(BDC)(Phen)(H2O)] 2, and the complex 2 was characterized in triclinic crystal system. Complex 1: space group Pnma with unit
ꢀ
ꢁ
cell dimensions a ¼ 23:378(2), b ¼ 12:830(1) and c ¼ 6:984(1) A, Z ¼ 4. Complex 2: space group P1 with unit cell dimensions
ꢀ
a ¼ 9:004(1), b ¼ 10:527(1) and c ¼ 10:577(1) A, a ¼ 114:779(1), b ¼ 92:246(1), c ¼ 114:746(1), Z ¼ 2.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Coordination polymer; One-dimensional structure; Two-dimensional structure; Structural transformation; Copper coordination polymer;
Hydrogen bonds
1
The design of coordination polymers with functional
properties such as inclusion and reversible adsorption
has been of great interest in current chemical and ma-
terials research [1,2]. New coordination polymers may be
prepared to have open-frameworks either via inclusion
of removable solvents or exchangeable ions [3]. In most
cases, the removal of the inclusion solvents from the
open-channel structures does not change the original
structure and the symmetry of the open-framework co-
ordination compounds [1b]. However, in the preparation
and characterization of a new mixed-ligand coordination
orthorhombic crystal system , was transformed into a
new compound due to the evaporation of inclusion sol-
vents, {[Cu(BDC)(Phen)(H2O)] 2, and the complex 2 was
characterized in triclinic crystal system. While the spacer
ligands of 1,10-phenanthroline and BDC with versatile
1
Crystal data for 1: FW, 516.98; orthorhombic, space group, Pnma.
ꢀ
Unit cell dimensions: a ¼ 23:378(2), b ¼ 12:830(1) and c ¼ 6:984(1) A,
U ¼ 2258:0(4) A , Z ¼ 4, Dcalc ¼ 1:521 g cmꢁ3, l ¼ 1:018 mmꢁ1
,
3
ꢀ
T ¼ 293(2) K. Reflections collected: 13118; independent reflections:
2780 [Rint ¼ 0:0882]. Final
R
indices [I > 2r(I)]: R1 ¼ 0:0454,
wR2 ¼ 0:0848. Diffraction data were collected on a Bruker Smart
polymer, {[Cu(BDC)(Phen)(H2O)] ꢀ (H2O)(DMF)}n
1
CCD diffractometer equipped with graphite-monochromated Mo-Ka
(BDC ¼ 1,4-benzenedicarboxylate; Phen ¼ 1,10-phe-
nanthroline), we found that the complex 1, crystallized in
ꢀ
radiation (k ¼ 0:71073 A) at room temperature. All asymmetric unit of
intensity data was collected in the x–2h scan mode. The final full-
matrix least-squares refinement was on F2. Crystal data for 2: FW,
ꢁ
425.87; triclinic crystal system, space group, P1; unit cell dimensions:
ꢀ
a ¼ 9:004(1), b ¼ 10:527(1) and c ¼ 10:577(1) A, a ¼ 114:779(1),
3
ꢀ
b ¼ 92:246(1), c ¼ 114:746(1), U ¼ 873:57(7) A , Z ¼ 2, Dcalc ¼ 1:619
g cmꢁ3, l ¼ 1.287 mmꢁ1, T ¼ 223(2) K. Reflections collected: 4521;
independent reflections: 3003 [Rint ¼ 0:0210]. Final
R indices
* Corresponding authors. Tel.: +1-281-283-3780; fax: +1-281-283-
[I > 4r(I)]: R1 ¼ 0:0249, wR2 ¼ 0:0692. All measurements were made
with a Siemens Smart platform diffractometer equipped with a IK
CCD area detector. The Laue symmetry was determined to be )1, and
3709.
E-mail addresses: chezlg@zju.edu.cn (L.-G. Zhu), lu@cl.uh.edu
ꢁ
(J.Y. Lu).
the space group was shown to be either P1 or P1.
1387-7003/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2003.09.023

L.-G. Zhu et al. / Inorganic Chemistry Communications 7 (2004) 94–96
95
binding mode has been utilized in the preparation of
many polymeric structures such as one-, two- and three-
dimensional infinite frameworks, structural transforma-
tion in-air after the removal of inclusion solvents has
never been observed [3b,4]. Herein we report the syn-
thesis and X-ray single crystal characterization of coor-
dination polymers 1 and 2.
Fig. 1. View of the 1-D zig-zag chain in complex 1.
The compound
1 was synthesized by adding
CuCl2 ꢀ 2H2O (0.0852 g, 0.5 mmol) into a 20 mL DMF
solution containing 1,4-benzenedicarboxylic acid
(0.0833 g, 0.5 mmol) and 1,10-phenanthroline (0.0991 g,
0.5 mmol). The resulting solution was stirred for 30 min
and some green precipitate was formed. It was then
followed by a filtration. The filtrate was allowed to
stand at room temperature for about a month, blue
single crystals of compound 1 were obtained. The
compound 1 was also obtained by using Cu(ClO4)2 ꢀ
6H2O instead of CuCl2 ꢀ 2H2O as a starting material.
Elemental analysis: calcd. for C23H23N3O7Cu, C 53.43,
N 8.13, H 4.48; found: C 53.18, N 8.17, H 4.28. Com-
pound 1 is insoluble in water and all common organic
solvents such as methanol, ethanol, acetone, tetrahy-
drofuran, chloroform, and DMF. Thermal analysis in-
dicated that complex 1 lost one DMF and two water
molecules at 83.0–286 °C with losing weight of 23.5%
(calcd., 21.1%), which is equivalent to the removal of
two water molecules and one DMF molecule per for-
mula unit.
Complex 2 was obtained by allowing the crystals of
complex 1 standing in-air for another two months. The
blue crystals of complex 2 were then collected and
subjected to X-ray single crystal characterization.
The structure of complex 1 consists of one crystallo-
graphically distinct copper atom bonded to two nitrogen
atoms from one Phen, two oxygen atoms from two
unidentate carboxylate groups of the two bridging BDC
ligands, and one oxygen atom from a water molecule
Fig. 2. One section of the 2-D network in complex 1.
ygen atoms from two bridging BDC ligands, two ni-
trogen atoms from a phen group, and one oxygen atom
from a water molecule at the apical position (Fig. 3).
The weak Cu–O interaction water molecule in complex 1
has been lost in air in complex 2, which confirmed the
result obtained from single crystal structural data of
complex 1. The apical oxygen atom bonded to copper
center in the structure of complex 2 displayed much
ꢀ
shorter interaction, with Cu–O distance of 2.025(1) A.
The l2-bridging BDC ligands responsible for the 1-D
chain motif in complex 2 showed different Cu–O dis-
ꢀ
tances with the copper center of 1.928(1) and 2.116(1) A,
respectively. The 2-D network structure in complex 2
maintained the stable hydrogen bonding interactions
found in complex 1 (Fig. 4) with even shorter hydrogen
bonds (O(5)–H(5A). . .O(4), 2.599(2); O(5)–H(5B). . .
ꢀ
O(2), 2.6416(19) A).
In summary, we have reported that an unusual
structural transformation has been observed in the
synthesis and structural characterization of new coor-
ꢀ
occupied at the apical position (Cu–O, 2.456(4) A).
Another oxygen atom from a water molecule is also
in the coordination sphere but with a weak Cu–O in-
ꢀ
teraction (non-bonding Cu–O(4), 2,672(4) A) located at
an axial position. Each BDC ligand in complex 1 adopts
ꢀ
a l2-bridging mode with a Cu–O distance of 1.931(2) A.
The phen acts as a terminal ligand with a Cu–N distance
ꢀ
of 2.015(2) A. Each copper atom center was linked by
two BDC ligands. The [CuII(l2-BDC)] linkage propa-
gates into a one-dimensional (1-D) zig-zag chain net-
work (Fig. 1). The 1-D chains were then connected by
hydrogen bonds with O–H. . .O distances of 2.764(3) to
ꢀ
2.825(5) A to form a two-dimensional (2-D) network
structure (Fig. 2). The solvent molecules are located
between the layers with hydrogen bonding interactions
ꢀ
(O(4). . .O(3), 2.825(5); O(3). . .O(2), 2.764(3) A).
The covalent coordination sphere of the copper metal
center in complex 2 was maintained without dramatic
changes. The copper atom was coordinated by two ox-
Fig. 3. View of the complete coordination about Cu showing the atom
numbering scheme. Thermal ellipsoids are 40% equiprobability enve-
lopes, with hydrogens as spheres of arbitrary diameter.

96
L.-G. Zhu et al. / Inorganic Chemistry Communications 7 (2004) 94–96
perimental Facilities supported by the National Science
Foundation and the Texas Center for Superconductivity
at the University of Houston.
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