A new carboxylic chelate ligand and its supramolecular complexes formed with sodium ions and alcohol molecules

Article abstract of DOI:10.1080/10610270902980648

The new hydrazone ligand 1, featuring a 2-carboxy group at the aromatic ring and a trifluoromethyl structural modification in the pentane-2,4-dione moiety, has been synthesised via the Japp-Klingemann route. The compound is shown to form binuclear multicomponent chelate complexes (2 and 3) composed of two sodium ions, two charge equalising carboxylates of the hydrazone molecule, two more carboxylic hydrazones and two alcohol solvent molecules, with the latter being either EtOH or n-BuOH. X-ray crystal structures of the free hydrazone ligand as well as of the complexes have been studied. They demonstrate for the free ligand a ribbon-type aggregation of carboxylic dimers, while the isomorphous complexes possess a remarkable binuclear structure with the two sodium ions in a distorted octahedral coordination geometry of six oxygen atoms coming, at the equatorial and apical sites, from the hydrazone carbonyl groups and the hydroxyl of the solvent molecules, respectively. The hydrogen bonds owing to the alcohol molecules give rise to the stack formation of the supramolecular cluster. Weak intermolecular contacts involving the fluorine atoms also contribute to the crystalline packing in the case of both the free ligand and the complexes.

Full text of DOI:10.1080/10610270902980648

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A new carboxylic chelate ligand and its supramolecular
complexes formed with sodium ions and alcohol
molecules
Jan Marten a , Wilhelm Seichter a & Edwin Weber a
a Institut für Organische Chemie , Technische Universität Bergakademie Freiberg , Leipziger
Straße 29, Freiberg/Sachsen, Germany
Published online: 18 Aug 2009.
To cite this article: Jan Marten , Wilhelm Seichter & Edwin Weber (2010) A new carboxylic chelate ligand and its
supramolecular complexes formed with sodium ions and alcohol molecules, Supramolecular Chemistry, 22:3, 163-171, DOI:
10.1080/10610270902980648
To link to this article: http://dx.doi.org/10.1080/10610270902980648
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Supramolecular Chemistry
Vol. 22, No. 3, March 2010, 163–171
A new carboxylic chelate ligand and its supramolecular complexes formed
with sodium ions and alcohol molecules
Jan Marten, Wilhelm Seichter and Edwin Weber*
¨ ¨
Institut fur Organische Chemie, Technische Universitat Bergakademie Freiberg, Leipziger Straße 29, Freiberg/Sachsen, Germany
(Received 25 February 2009; final version received 13 April 2009)
The new hydrazone ligand 1, featuring a 2-carboxy group at the aromatic ring and a trifluoromethyl structural modification
in the pentane-2,4-dione moiety, has been synthesised via the Japp–Klingemann route. The compound is shown to form
binuclear multicomponent chelate complexes (2 and 3) composed of two sodium ions, two charge equalising carboxylates of
the hydrazone molecule, two more carboxylic hydrazones and two alcohol solvent molecules, with the latter being either
EtOH or n-BuOH. X-ray crystal structures of the free hydrazone ligand as well as of the complexes have been studied. They
demonstrate for the free ligand a ribbon-type aggregation of carboxylic dimers, while the isomorphous complexes possess a
remarkable binuclear structure with the two sodium ions in a distorted octahedral coordination geometry of six oxygen
atoms coming, at the equatorial and apical sites, from the hydrazone carbonyl groups and the hydroxyl of the solvent
molecules, respectively. The hydrogen bonds owing to the alcohol molecules give rise to the stack formation of the
supramolecular cluster. Weak intermolecular contacts involving the fluorine atoms also contribute to the crystalline packing
in the case of both the free ligand and the complexes.
Keywords: chelate ligand; sodium coordination; alcohol supramolecular complexes; X-ray crystal structures; hydrogen
bonds
Introduction
aiming at the design of sorptive materials that may be used
for compound storage (19, 20) or chemical sensing (21).
Particular transition metal complexes, known as the MOF-
type coordination polymers (22, 23), are currently a very
active field of research in these respects, while correspond-
ing complexes formed of main group metal ions, especially
alkali and alkaline earth metal ions, are up for
development.
The binding and transport of the sodium and potassium
metal ions are of vital importance to life (1). Naturally
occurring substances, capable of performing these
processes, are given by the well-known ionophores such
as valinomycin and nonactin (2). The rapid development of
the crown compounds (3), as an exemplary synthetic
mimic, has presented us with an immense variety of
macrocyclic ligands (4) that form complexes with alkali
metal ions of different thermodynamics and kinetics (5),
corresponding to their degree of preorganisation (6). In this
connection, noncyclic analogues of the crown compounds,
designated as podands (7), that form complexes with main
group I metal ions, have also been prepared in a wide range
(8, 9). Besides these noncyclic ligands of aprotic nature,
the protic complexones are another important class of the
ligands providing neutral chelate complexes of inner salt
type with alkali and alkaline earth metal ions (7). Some of
them are traditional tools in analytical chemistry (10).
The others have been studied with regard to their biological
activity (11–13) or specific coordination geometry
(14, 15). Recent challenges arise from current topics of
supramolecular chemistry (6) involving crystal engineer-
ing (16) and molecular recognition behaviour (17, 18),
In a previous paper (24), we reported on the complexes
of 3-(arylhydrazono)pentane-2,4-diones with the tran-
sition metal ions copper(II) and nickel(II). Moreover, we
found that fluorine substitution in the pentane-2,4-dione
moiety of the hydrazone gave rise to a particular packing
mode in the crystal structure (25), which could also have a
favourable effect here. We now describe for the first time
complexes of a respective hydrazone 1 with sodium ions,
containing additional alcohol molecules in the coordi-
nation sphere, to yield an interesting new type of
supramolecular aggregate structure. In terms of facts, the
present complexes are composed of molecules of the
hydrazone 1, the carboxylate of 1, sodium ions and ethanol
(2) or n-butanol (3) solvent molecules in a stoichiometric
ratio 2:2:2:2, respectively, considering the formed cluster
unit (Scheme 1). The synthesis of the compounds (1–3) is
presented and their X-ray crystal structures are discussed.
*Corresponding author. Email: edwin.weber@chemie.tu-freiberg.de
ISSN 1061-0278 print/ISSN 1029-0478 online
q 2010 Taylor & Francis
DOI: 10.1080/10610270902980648
http://www.informaworld.com

164
J. Marten et al.
Structural study
The crystal data, experimental parameters and selected
details of the refinement calculations are summarised in
Table 1. The information regarding conformational
features and possible non-covalent interactions in the
crystal structures is presented in Tables 2–4.
The molecular structures are depicted in Figures 1, 3 and
4, while packing illustrations are presented in Figures 2
and 5.
Crystal structures of the free ligand (1)
The hydrazone 1 crystallises from toluene as yellow rods
of the triclinic space group P-1. The molecular structure
including the atom numbering scheme is presented in
Figure 1. Being in conformity with the crystal structure
analyses of the related compounds (24, 25, 29), the
molecular structure of 1 shows the presence of an
intramolecular six-membered hydrogen-bonded ring
formed between the N-bound hydrogen H(2) and one of
the oxygens of the pentane-2,4-dione fragment
˚
[N(2)ZH(2)· · ·O(1) 1.90 A, 131.28]. In addition, this
hydrogen atom is bonded to O(3) of the carboxy
˚
substituent [N(2)ZH(2)· · ·O(3) 2.00 A, 126.58], giving
rise to a bifurcated bonding situation for H(2). The fact
that the oxygen of the CH3CO moiety is used for strong
intramolecular hydrogen bonding indicates the higher
Scheme 1. Compounds discussed.
Results and discussion
Synthesis of compounds
The free arylhydrazone ligand 1 was synthesised via the
Japp–Klingemann reaction (26) between the diazonium
salt of 2-aminobenzoic acid and 1,1,1-trifluoropentane-
2,4-dione in a methanolic solution containing sodium
acetate (27). The diazonium salt was prepared by the usual
diazotation of 2-aminobenzoic acid (28). The complexes 2
and 3 were obtained by recrystallisation of crude 1 from
ethanol and n-butanol, respectively, in the presence of
sodium ions, coming from the reaction components.
Table 1. Crystal data, experimental parameters and selected details of the refinement calculations of compounds 1–3
(estimated standard deviations are in parentheses).
Compound
1
2
3
Formula unit
Formula weight
Crystal system
Space group
C12H9F3N2O4
302.21
Triclinic
P-1
C52H44F12N8Na2O18
1342.93
Monoclinic
P21/n
C56H54F12N8Na2O18
1401.06
Monoclinic
P21/n
Unit cell dimensions
˚
a (A)
˚
5.0637(2)
8.5278(4)
14.596(1)
95.317(3)
90.422(2)
106.144(2)
602.45(5)
2
13.3812(9)
8.0093(6)
27.829(2)
90
97.126(3)
90
2959.5(4)
2
1.507
13.350(3)
7.9930(2)
28.931(6)
90
93.25(3)
90
3082.2(12)
4
1.510
b (A)
˚
c (A)
a (8)
b (8)
g (8)
3
˚
V (A )
Z
Dc (m23
)
1.666
Data collection
Temperature (K)
No. of collected reflections within the u-limit (8)
No. of unique reflections
Rint
93(2)
17252
3865
153(2)
30380
6522
93(2)
30443
6553
0.0379
0.0669
0.0671
Refinement calculations full-matrix least-squares based on all F 2 values
No. of refined parameters
No. of values used [I . 2s(I)]
R( ¼ SjDFj/SjFoj)
196
2591
0.0432
0.1334
426
4243
0.0584
0.1933
449
3915
0.0494
0.1745
wR on F 2

Supramolecular Chemistry
165
˚
Table 2. Selected structural parameters [distances (A), angles (8)] involving the ligand molecules in compounds 1–3.
Atoms involved
1
2 (LH)
2 (L)
3 (LH)
3 (L)
Bond lengths
N(1)ZN(2)
N(1)ZC(3)
N(2)ZC(6)
C(2)ZC(3)
C(3)ZC(4)
C(2)ZO(1)
C(4)ZO(2)
C(7)ZC(12)
1.303(3)
1.322(3)
1.411(2)
1.484(2)
1.464(2)
1.230(2)
1.211(2)
1.479(2)
1.300(3)
1.324(3)
1.403(3)
1.478(4)
1.453(4)
1.217(3)
1.210(3)
1.479(4)
1.290(3)
1.327(3)
1.417(3)
1.467(4)
1.461(4)
1.461(4)
1.206(3)
1.519(3)
1.299(4)
1.324(4)
1.411(4)
1.487(5)
1.462(5)
1.225(4)
1.210(4)
1.499(4)
1.299(4)
1.338(4)
1.414(4)
1.472(4)
1.463(5)
1.223(4)
1.211(4)
1.508(4)
Bond angles
C(3)ZN(1)ZN(2)
N(1)ZN(2)ZC(6)
N(1)ZC(3)ZC(2)
N(1)ZC(3)ZC(4)
C(2)ZC(3)ZC(4)
C(3)ZC(2)ZO(1)
C(3)ZC(4)ZO(2)
121.6(1)
118.7(1)
124.8(1)
112.3(1)
122.9(1)
118.5(1)
125.6(1)
121.1(2)
119.8(2)
124.7(2)
112.8(2)
122.4(2)
119.2(2)
126.1(2)
121.7(2)
119.5(2)
124.7(2)
112.7(2)
122.6(2)
118.4(2)
125.9(3)
121.3(3)
119.4(3)
125.0(3)
112.8(3)
122.2(3)
118.5(3)
125.9(3)
121.0(3)
119.7(3)
124.1(3)
113.2(3)
122.7(3)
119.6(3)
125.2(3)
Torsion angles
O(1)ZC(2)ZC(3)ZN(1)
C(2)ZC(3)ZN(1)ZN(2)
C(3)ZN(1)ZN(2)ZC(6)
C(2)ZC(3)ZC(4)ZO(2)
24.6(2)
25.2(4)
1.1(3)
2180.0(2)
8.8(4)
20.17(4)
1.0(4)
2179.1(2)
2.7(5)
25.9(5)
23.4(5)
2.0(4)
2179.4(3)
2.6(5)
0.5(2)
2175.7(1)
13.8(2)
0.1(5)
2178.8.2(3)
5.4(6)
Dihedral angles
mpla(1)a· · ·mpla(2)b
7.24
4.98
11.37
3.00
7.51
ampla(1): mean plane through the atoms C(6)ZC(7)ZC(8)ZC(9)ZC(10).
bmpla(2): mean plane through the atoms H(2)ZN(2)ZN(1)ZC(3)ZC(2)ZO(1).
acceptor ability compared to the CF3CO unit. The oxygen
of this latter fragment is involved only in weak
intermolecular hydrogen bonding. Two of the fluorine
atoms of each molecule take part in molecular cross-
linking by forming weak CZH· · ·F and CZF· · ·F contacts
As diplayed in Figure 2, in the crystal structure of 1,
molecules interact among each other by hydrogen bonding
˚
of their carboxylic acid groups [O(4)ZH(4)· · ·O(3) 1.81 A,
174.58], thus forming conventional centrosymmetric
dimers. They are further linked by bifurcated CZH· · ·O
˚
˚
˚
hydrogen bonds (32) [C(8)ZH(8)· · ·O(2) 2.58 A, 121.78,
˚
C(9)ZH(9)· · ·O(2) 2.53 A, 123.28], resulting in infinite
supramolecular ribbons. Generally, the packing structure
consists of 2D molecular sheets being linked among each
other through CZH· · ·F contacts.
(30, 31) [H· · ·F 2.69 A; F· · ·F 2.91(1) A]. This may explain
the distortion of the pentane-2,4-dione unit, which is
reflected by the torsion angles that deviate significantly
from the ideal values of 0 and 1808 (Table 2).
Table 3. Bond lengths (A) and angles (8) involving Naþ in the
complexes 2 and 3.
˚
Crystal structures of the sodium complexes 2 and 3
Crystallisation of the aryl hydrazone 1 from ethanol or
n-butanol in the presence of sodium ions from the
crude product yields complexes of the composition
[Na2L2(LH)2]·2 ROH as yellow rods. For each of the
two complexes, the asymmetric unit of the cell contains
one half of the molecule, i.e. the complexes exhibit
inversion symmetry. The structure of the Naþ(LH)L2 unit
and the molecular structures of the complexes with the
labelling of the relevant atoms are depicted in Figures 3
and 4, respectively. The space group symmetries (P21/n) as
well as the crystallographic parameters (Table 1) indicate
that the structures of 2 and 3 are isomorphous. Hence, a
detailed structural description can be confined to the
crystal structure of 2, being transferable to 3.
2
3
Bond lengths
Na(1)ZNa(10)
Na(1)ZO(1)
Na(1)ZO(1A)
Na(1)ZO(3)
Na(1)ZO(30)
Na(1)ZO(3A)
Na(1)ZO(1GA)
Na(1)ZO(1G)
3.402(2)
2.341(2)
2.382(2)
2.421(2)
2.368(2)
2.284(2)
2.463(2)
2.260(9)
3.346(2)
2.344(2)
2.423(2)
2.372(2)
2.393(2)
2.284(2)
2.291(2)
Bond angles
O(1GA)ZNa(1)ZO(30)
O(1)ZC(2)ZO(3A)
O(3)ZC(4)ZO(1A)
170.7(5)
163.6(1)
162.1(1)
166.3(1)
161.0(1)
163.3(1)

166
J. Marten et al.
˚
Table 4. Structural parameters [distances (A), angles (8)] of the non-covalent interactions in compounds 1–3.
Distances
Atoms involved
DZH· · ·A
Angle
DZH· · ·A
Symmetry
DZH
D· · ·A
H· · ·A
(1)
N(2)ZH(2)· · ·O(1)
N(2)ZH(2)· · ·O(3)
C(8)ZH(8)· · ·O(2)
C(9)ZH(9)· · ·O(2)
O(4)ZH(4)· · ·O(3)
C(9)ZH(9)· · ·F(2)
C(10)ZH(10)· · ·F(3)
C(5)ZF(1)· · ·F(1)
x, y, z
x, y, z
0.92
0.92
0.95
0.95
0.84
0.95
0.95
(CZF)
1.33
2.598(2)
2.655(2)
3.183(2)
3.153(3)
2.645(2)
3.381(3)
3.373(3)
(C· · ·F)
1.90
2.00
2.58
2.53
1.81
2.69
2.70
(F· · ·F)
2.91
131.2
126.5
121.7
123.2
174.5
130.3
128.7
(CZF· · ·F)
98.9
22 þ x 2 1 þ y, z
22 þ x, 21 þ y, z
21 2 x, 1 2 y, 1 2 z
21 þ x, 1 2 y, z
1 2 x, 1 2 y, 2z
1 2 x, 1 2 y, 2z
3.379(3)
(2)
N(2)ZH(2)· · ·O(1)
N(2)ZH(2)· · ·O(3)
C(9A)ZH(9A)· · ·O(2)
C(8)ZH(8)· · ·O(4)
N(2A)ZH(2A)· · ·O(1A)
N(2A)ZH(2A)· · ·O(3A)
O(1G)ZH(1G)· · ·O(4A)
O(1GA)ZH(1GA)· · ·O(4A)
O(4)ZH(4)· · ·O(4A)
C(1)ZH(1C)· · ·F(1A)
C(1G)ZH(1G2)· · ·F(1)
C(9)ZH(9)· · ·F(2)
x, y, z
x, y, z
0.89
0.89
0.95
0.89
0.89
0.89
0.85
0.84
0.84
0.98
0.99
0.95
0.98
2.591(3)
2.616(3)
3.580(3)
2.703(3)
2.588(3)
2.644(3)
2.802(3)
2.606(3)
2.536(3)
2.949(4)
3.204(4)
3.405(4)
3.389(4)
1.94
1.92
2.64
2.37
1.90
2.00
1.95
1.77
1.72
2.63
2.57
2.64
2.62
128.8
134.0
170.6
100.4
133.0
127.8
178.4
172.6
164.4
99.4
20.5 þ x, 1.5 þ y, 20.5 þ z
x, y, z
x, y, z
x, y, z
2x, 2 2 y, 2z
2x, 2 2 y, 2z
x, y, z
1 2 x, 1 2 y, 2z
0.5 2 x, 0.5 þ y, 0.5 2 z
20.5 2 x, 0.5 þ y, 0.5 2 z
0.5 2 x, 20.5 þ y, 0.5 2 z
121.6
138.3
135.2
C(1)ZH(1A)· · ·F(3)
(3)
N(2)ZH(2)· · ·O(1)
N(2)ZH(2)· · ·O(3)
C(9A)ZH(9A)· · ·O(2)
C(8)ZH(8)· · ·O(4)
N(2A)ZH(2A)· · ·O(1A)
N(2A)ZH(2A)· · ·O(3A)
O(1G)ZH(1G)· · ·O(4A)
O(4)ZH(4)· · ·O(4A)
C(1)ZH(1B)· · ·F(1A)
C(10)ZH(10)· · ·F(2A)
C(9)ZH(10)· · ·F(2A)
x, y, z
x, y, z
0.90
0.90
0.95
0.95
0.90
0.90
0.85
0.84
0.98
0.95
0.95
2.595(4)
2.612(4)
3.621(5)
2.701(4)
2.576(4)
2.635(4)
2.744(4)
2.544(4)
3.219(5)
3.165(5)
3.191(5)
1.92
1.93
2.69
2.36
1.89
1.96
1.90
1.73
2.61
2.61
2.55
130.3
130.9
168.3
100.8
131.2
130.7
177.6
163.9
120.6
118.0
125.2
0.5 þ x, 0.5 2 y, 0.5 þ z
x, y, z
x, y, z
x, y, z
2 2 x, 2y, 2 2 z
x, y, z
1 2 x, 1 2 y, 2 2 z
0.5 þ x, 0.5 2 y, 20.5 þ z
2 2 x, 2y, 2 2 z
In the binuclear complex of 2, which is constructed of
two anionic (L2) and two uncharged ligands (LH), the
sodium ions adopt a distorted octahedral coordination
environment [Figure 4(a)]. The equatorial positions within
the coordination polyhedron are occupied by the oxygens
of two ligands with the NaZO distances ranging between
coordinating behaviour of the fluorine atoms of the
respective CF3CO moiety. Only one fluorine atom of the
anionic ligand is involved in the intermolecular association
via CZH· · ·F hydrogen bonding (30, 31), whereas in the
protonated ligand, all the fluorine atoms take part in this
kind of interaction. Another striking difference between
the ligands is the inclination of the carboxylate group with
respect to the aromatic ring to which it is attached
[20.4(2)8], whereas the benzoic acid element of the
uncharged ligand hardly deviates from planarity. As in
the crystal structure of 1, the almost planar geometry of the
ligands is stabilised by a tight network of intramolecular
hydrogen bonds comprising bifurcated NZH· · ·O contacts
between the N-bound hydrogens H(2) [H(2A)] and the
carbonyl oxygens O(1) [O(1A)] as well as the carboxy and
carboxylate oxygens [O(3) and O(3A)]. Moreover, the
ortho-substituents of pairs of ligand molecules are
˚
2.284(2) and 2.382(2) A. The axial positions are occupied
by the oxygen of the disordered ethanol molecule (SOF:
0.67, 0.33) and the carboxylate oxygen which is
simultaneously bonded to both the sodium ions.
The corresponding NaZO distances are 2.463(2)
˚
[2.260(2)] and 2.421(2) A, respectively; the Na· · ·Na
˚
distance is 3.402(2) A. A conformational analysis of the
complex ligands LH and L2 reveals less differences
regarding their bond lengths, but shows different degrees
of distortion of their pentane-2,4-dione fragments
(Table 2), which can be ascribed to an asymmetric

Supramolecular Chemistry
167
molecules and the carboxylate groups of the complex
˚
ligands [O(1GA)ZH(1GA)· · ·O4 1.77 A, 172.68]. An
inter-stack association is realised by the CZH· · ·F
˚
hydrogen bonding (H· · ·F 2.57–2.63 A).
The increased spatial demand of the alcohol
component (n-BuOH) of the complex 3 induces an
elongation of the crystallographic c-axis and lowers the
monoclinic angle. However, the molecular structure as
well as the packing behaviour of the complex 3 deviates
only insignificantly from 2, which is also evident from
Figure 4. Both the crystal structures show approximately
identical patterns of non-covalent interactions.
Comparative reflection and conclusions
The new carboxylic hydrazone ligand 1 and its uncharged
supramolecular complexes, containing besides sodium
ions EtOH (2) or n-BuOH (3) solvent molecules, were
studied by the X-ray crystal structure technique, giving
rise to the following statement.
Figure 1. A perspective view of the molecular structure of 1
(LH) including the atom numbering scheme of the non-hydrogen
atoms. Thermal ellipsoids are drawn at a 50% probability level.
The broken lines represent the hydrogen bonds.
connected by a strong OZH· · ·O2 hydrogen bond
˚
[O(4A)ZH(4A)· · ·O(4) 1.72 A, 164.48]. The distance of
˚
3.45 A between the aromatic rings and the six-membered
The molecular geometry of 1 is virtually the same as
found for the other previously studied fluorine-free and
fluorine-containing examples of this compound class,
showingtheintramolecularsix-memberedhydrogen-bonded
ring and the overall planar geometry due to the extensive
conjugation of the p-electron system (24, 25, 29). Also, the
fact that the acetyl unlike the trifluoroacetyl oxygen of the
pentane-2,4-dione moiety forms the intramolecular hydro-
gen bondisrevealedinthestructureofcompound1. Hence, a
constitutional modification by an ortho-substituted car-
boxylic group does not markedly affect the conformational
hydrogen-bonded rings suggests the presence of inter-
molecular p· · ·p interactions. The stacking interactions
between the aromatic building blocks are also evident in
the overall crystal structure of 2, being characteristic of a
columnar packing mode which shows an offset arrange-
ment between the consecutive molecules (Figure 5).
Within a given stack, the complex molecules are linked via
the OZH· · ·O hydrogen bonds between the alcohol
Figure 2. An excerpt of the packing structure of 1 (LH) showing the mode of intermolecular interactions. The heteroatoms are
distinguished by a different shading. The broken lines represent hydrogen-bond-type interactions.

168
J. Marten et al.
Figure 3. A perspective view of the equatorial coordination plane (open lines) around a sodium ion in the complexes 2 and 3. The broken
lines represent the hydrogen bonds.
solid-statestructureinherentofthehydrazoneframeworkbut
actually helps to stabilise the planar geometry of the
molecule by additional intramolecular hydrogen bonding.
A rather comparable situation with the involvement of an
additional oxygen atom in the intramolecular hydrogen
bonding was found for a related hydrazone featuring two
ortho-positioned nitro substituents (29). By contrast, the
carboxylic function of 1 has a strong bearing on the packing
structure in that hydrogen-bonded dimers are formed,
leading to the supramolecular ribbons which determine the
lattice structure.
complexes with the hard alkali metal ion Naþ. This gives
rise to an interesting supramolecular aggregate, compris-
ing in addition to the two metal ions and the two charge
equalising carboxylates of the hydrazone two more
carboxylic hydrazones and two alcohol solvent molecules
for the construction of the supramolecular cluster.
A challenging idea for a future structural design is to
exchange the simple alcohol molecules for multivalent
alcohols or more specific tectones (33) featuring other
coordinative functions. Investigations into this direction
are the aim of our group.
An almost planar geometry of the hydrazone mol-
ecule(s) stabilised by an analogous network of intramole-
cular hydrogen bonds, incorporating the carboxyl and
carboxylate oxygens, respectively, is also shown in the
isomorphous structures of the sodium complexes 2 and 3.
In other words, the conformational structure of the
hydrazone molecules is only little affected by the formation
of the carboxylate group and binding to the sodium ion,
unlike the packing in the crystal, leading to the specific
formation of a binuclear alcohol-containing cluster around
the sodium ions. That is, the carboxylic dimers in 1 are
broken at a single site of the hydrogen-bonded ring by the
deprotonation followed by an insertion of the sodium ion.
The binuclear complexes associate in a stack stabilised via
hydrogen bonding through the alcohol molecules, whereas
the contact between the neighbouring stacks is only of the
weak CZH· · ·F type of interaction. Therefore, the overall
supramolecular packing motif is ribbon-type for 1 and
stack-like for 2 and 3, in each case being involved in a weak
interconnection through the intermediary of fluorine atoms.
In summary, we have shown that this particular
compound class of arylhydrazones not only yields
complexes with soft transition metal ions such as Cu2þ
and Ni2þ, but also is capable of forming chelate-type
Experimental
General
Elemental analysis: Heraeus CHN rapid analyser; MS
(EI): Finnigan MAT 8200; FT-IR: KBr disc, Nicolet 510;
NMR (internal standard TMS): Bruker Avance DPX 400.
The starting compounds (2-aminobenzoic acid and 1,1,1-
trifluoropentane-2,4-dione) were purchased from Aldrich
(St Louis, MO, USA).
Synthesis
3-[(2-Carboxyphenyl)hydrazono]-1,1,1-trifluoropentane-
2,4-dione, LH (1)
A solution of the diazonium salt was prepared under
cooling (0–58C) from 2-aminobenzoic acid (2.6 g,
19 mmol) in hydrochloric acid (3 N, 40 ml) and a
concentrated aqueous solution of sodium nitrite (1.3 g,
19 mmol), according to the standard procedure (28).
The cold solution of the diazonium salt was added under
cooling (08C) and stirring to a mixture being composed of
1,1,1-trifluoropentane-2,4-dione (2.28 ml, 2.93 g,
19 mmol), NaOH (1.0 g, 25 mmol), sodium acetate (7.5 g,

Supramolecular Chemistry
169
Figure 4. A perspective view of the complexes (a) 2 and (b) 3. The heteroatoms are distinguished by a different shading. The thin lines
around the sodium ions represent the coordinative bonds; the broken lines represent the hydrogen bonds. Only one of the disordered
positions of the ethanol molecule in (a) is displayed for clarity.

170
J. Marten et al.
Figure 5. The packing motif of the complex 2. The heteroatoms are distinguished by a different shading; the non-relevant hydrogen
atoms are omitted. The thin lines around the sodium ions represent the coordinative bonds; the broken lines mean the hydrogen bonds.
Only one of the disordered positions of the ethanol molecule is displayed for clarity.
92 mmol), methanol (160 ml) and water (160 ml).
The mixture was allowed to warm to room temperature
and stirred for 1 h. The precipitate that had formed was
collected, washed with water, dried and recrystallised
from toluene to afford 5.3 g (92%) yellow crystals; mp
249–2518C (dec.). IR (KBr, cm21): 3336 (s, NZH), 1677
(s, CvO), 1639 (s, CvO), 1591 (s, CvN), 1380–1356 (s,
COvCH3), 758 (s, Ar-H); 1H NMR (400 MHz, CDCl3): d
storage out of the mother liquor and rapidly decompose on
heating to 86–888C with the release of the solvent.
Complex [Na2L2(LH)2]·2 n-BuOH (3)
The crude product 1, as provided from synthesis, was
recrystallised from n-butanol to yield on storage at 0–58C
during a period of 2 weeks compound 3 as yellow crystals
that are rather unstable out of the mother liquor and rapidly
decompose at 125–1278C with the release of the solvent.
3
2.49 (s, 3H, CH3), 7.32 (t, JHH ¼ 8.0 Hz, 1H, p-Ar-H),
3
7.67 (t, JHH ¼ 8.0 Hz, 1H, m-Ar-H), 7.83 (d,
3
3JHH ¼ 8.0 Hz, 1H, o-Ar-H), 8.03 (d, JHH ¼ 8.0 Hz, 1H,
m-Ar-H), 11.94 (s, 1H, COOH), 16.32 (s, 1H, NH); 13C
NMR (100.6 MHz, CDCl3): d 30.84 (C H3), 105.30 (CF3),
115.04 (o-Ar-C), 121.01 (CZCOOH), 125.74 ( p-Ar-C),
129.59 (CvN), 131.53 (m-Ar-C), 133.49 (m-Ar-C),
145.19 (CZN), 167.84 (COOH), 176.03 (CF3ZCvO),
193.45 (CvO); MS (EI): m/z calcd for C12H9F3N2O4:
302.05. Found: 302 ([Mþ], 100%). Anal. calcd for
C12H9F3N2O4: C, 56.26; H, 5.04; N, 8.75. Found: C,
56.38; H, 4.96; N, 8.75.
X-ray crystallography
The single crystals of the compounds 1–3, suitable for
X-ray diffraction study, were obtained on recrystallisation
from the solvents as given with the synthetic procedures.
The intensity data were collected on a Kappa APEX II
diffractometer (Bruker-AXS) with graphite monochro-
˚
mated CuKa-radiation (l ¼ 0.71073 A) using v- and
f-scans. The reflections were corrected for background,
Lorentz and polarisation effects. The preliminary structure
models were derived by the application of direct methods
(34) and were refined by the full-matrix least-squares
calculation based on F 2 for all the reflections (35). For the
metal complexes, an empirical absorption correction based
on multi-scans was applied by using the SADABS
Complex [Na2L2(LH)2]·2 EtOH (2)
The crude product 1 of the above synthetic procedure was
recrystallised from ethanol instead of toluene to yield
compound 2 as yellow crystals that become opaque on

Supramolecular Chemistry
171
(12) Browing, K.; Abboud, K.A.; Palenik, G.J. J. Chem.
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J.M. J. Chem. Soc., Dalton Trans. 2000, 3401–3410.
program (36). All non-hydrogen atoms were refined
anisotropically. With the exception of the amino hydrogen
atom H(2) in structures 1–3 and the hydroxy hydrogen
atom of the alcohol component in 2, all the hydrogen atoms
were included in the models in the calculated positions and
were refined as constrained to the bonding atoms. The
crystal data and experimental parameters are summarised
in Table 1. The crystallographic data for the structures in
this paper have been deposited with the Cambridge
Crystallographic Data Centre as the supplementary
publication numbers CCDC-720739 (1), CCDC-720740
(2) and CCDC-720738 (3). Copies of the data can be
obtained free of charge on application to the Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax:
þ44-1223-336033, Email: deposit@ccdc.cam.ac.uk).
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Acknowledgement
We gratefully acknowledge the financial support by the German
Federal Ministry of Science and Technology (BMBF) under
Grant No. 02110120 ‘Biomon’.
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