A Zipper-like Supramolecular Double-Chain based on 1 D p-p Stacking
Interactions: Synthesis and Crystal Structure
of [Cu(phen)(C
4
H
4
O
4
)(H
2
O)]
2
´C
4
H
6
O
4
(phen = 1,10-phenanthroline)
Yue-Qing Zheng*, Jie Sun and Jian-Li Lin
Ningbo/P. R. China, Institute for Solid State Chemistry, Chemistry Department of Ningbo University
Received December 20th, 1999
Abstract. [Cu(C
12
H
8
N
2
)(C
4
H
4
O
4
)(H
2
O)]
2
´C
4
H
6
O
4
was
prepared by the reaction of succinic acid, CuCl
2
´2H
2
O,
1,10-phenanthroline (phen = C
12
H
8
N
2
), and Na
2
CO
3
in a
CH
3
OH±H
2
O solution. The crystal structure (triclinic, P 1
(no. 2), a = 7.493(1), b = 9.758(1), c = 13.517(1) A
Ê
;
a
=
68.89(1)°, b = 88.89(1)°, c = 73.32(1)°, Z =1, R = 0.0308,
wR
2
= 0.0799 for 3530 observed reflections (F
2
o
³ 2r(F
2
o
) out
of 3946 unique reflections) consists of hydrogen bonded
succinic acid molecules and succinato bridged 1 D zipper-
like supramolecular
1
1
[Cu(phen)(C
4
H
4
O
4
)
2/2
(H
2
O)]
2
double
chains based on 1 D p-p stacking interactions between the
chelating phen systems at distances of 3.71 A
Ê
and 3.79 A
Ê
.
The Cu atoms are fivefold trigonal bipyramidally coordi-
nated by two N atoms of the bidentate chelating phen ligand
and three O atoms of one water molecule and two bidentate
bridging succinate ligands. The water O atom and one phen
N atom are at the apical positions (equatorial: d(Cu±O) =
1.945, 2.254(2) A
Ê
, d(Cu±N) = 2.034(2) A
Ê
; axial: d(Cu±O) =
1.971(2) A
Ê
, d(Cu±N) = 1.995 A
Ê
).
Keywords: Copper(II) complexes; Crystal structure; p -p
stacking interaction; Supramolecular double-chain
Recently, designing and tailor-making of infinite polymeric
configuration with 1 D to 3 D extended structure by using a
bifunctional ligand, e. g., 4,4'-bipyridine, to link metal ions
have become one of the most active areas of materials re-
search, because incorporation of some active groups into co-
ordination polymers offers an excellent path to develop
functional materials with interesting properties such as elec-
tronic, magnetic, second-order nonlinear optical, inclusion,
and catalytic properties [1±19]. On the other hand, it is well-
known that weak interactions are essential for molecular re-
cognition and self-organization of molecules in supramolecu-
lar chemistry [20±21]. In particular, the stacking interactions
between suitable aromatic moieties of the twofold coordinat-
ing ligands are fascinating [22±24], since p-p stacking interac-
tions have been recognized to be very important in proteins
and protein-DNA systems for protein stabilization and var-
ious regulatory processes [25±26]. Our previous research in-
dicates that
a
,x-dicarboxylate groups behave as good candi-
dates of bifunctional ligands linking metal ions to build 1 D,
2 D and 3 D polymeric frameworks [27±32], which stimulates
our further research interests to combine the bifunctional
features of
a
,x-dicarboxylate ligands with aromatic stacking
interactions to study supramolecular complexes. In this
work, we report a novel ternary Cu phen succinato complex
with zipper-like supramolecular double-chains based on 1 D
p-p stacking interactions.
The crystal structure consists of the hydrogen bonded suc-
cinic acid molecules and 1 D
1
1
[Cu(phen)(C
4
H
4
O
4
)
2/2
(H
2
O)]
2
supramolecular double chains. The Cu atoms are fivefold tri-
gonal bipyramidally coordinated by both N atoms of the bi-
dentate chelating phen ligand and by the O atoms of one
water molecule and two bidentate bridging succinate anions
(Fig. 1). The water O atom and one of the phen N atoms are
at the apical positions of the coordination polyhedron with
d
ap
(Cu±O) = 1.971(2) A
Ê
and d
ap
(Cu±N) = 1.995(2) A
Ê
.The
equatorial bond lengths are d
eq
(Cu±O) = 1.945(2) A
Ê
and
2.254(2) A
Ê
as well as d
eq
(Cu±N) = 2.034(2) A
Ê
. Evidently, the
coordination polyhedron of the Cu atom is actually distorted
(Table 1). The Cu atom is shifted by 0.124(1) A
Ê
from the
equatorial plane toward the apical water molecule. The phen
ligand is nearly perpendicular to the equatorial plane with
the dihedral angle of 88.4(1)°. The succinate ligands bridge
the Cu atoms to form primary neutral 1 D supramolecular
chains
1
1
[Cu(phen)(C
4
H
4
O
4
)
2/2
(H
2
O)] along [100] with par-
allel orientated phen ligands at the same side (Fig. 2). The
phen ligands of two adjacent supramolecular chains cover
each other with the quinoline fragments at the alternative
distances of 3.71 A
Ê
and 3.79 A
Ê
, forming zipper-like supra-
molecular double-chains
1
1
[Cu(phen)(C
4
H
4
O
4
)
2/2
(H
2
O)]
2
(Fig. 2). Apparently, the present spacings of 3.71 A
Ê
and
3.79 A
Ê
are comparable well with those for the p-p stacking
interactions reported in the literature [33±35]. In this sense,
the title compound represents an unprecedented supra-
molecular complex with zipper-like double-chains formed
by p-p stacking interactions throughout the whole
structure. The bridging succinate ligands are twisted with tor-
sion angle of about 71.3(3)° in the carbon chain. The term-
inal carboxyl groups orientate roughly perpendicular to each
other to meet the requirement of effective p-p stacking inter-
actions.
The additional free succinic acid molecules are imbedded
in voids (Fig. 3). Configuration and bond lengths of the acid
and the anion are different. The terminal carboxyl groups of
the bridging succinate ligands are rotated to form strong in-
trachain hydrogen bonds to water molecules with O±H ´ ´ ´ O
distances of 2.572 A
Ê
and 2.613 A
Ê
, and O±H ´ ´ ´ O angles of
Z. Anorg. Allg. Chem. 2000, 626, 1501±1504 Ó WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000 0044±2313/00/6261501±1504 $ 17.50+.50/0 1501
* Prof. Dr. Y.-Q. Zheng,
Institute for solid state chemistry,
Chemistry Department of Ningbo University,
Ningbo, Zhejiang, 315211 P. R. China,
Telefax: Int. + 5 74/7 60 07 47
e-mail: zhengcm@nbu.edu.cn