Tetra-μ-benzoato-κ 8O:O′-bis({1-[(3,4-dimethoxyphenyl)methyl]-6, 7-dimethoxyisoquinoline-κN}zinc(II)): The first crystal structure with papaverine as a ligand

Article abstract of DOI:10.1107/S010827010302883X

The title complex, [Zn₂(C₇H₅O ₂)₄(C₂₀H₂₁NO₄) ₂], forms dimers of the paddle-wheel cage type located at crystallographic inversion centres. The two Zn atoms [Zn...Zn = 3.0533 (4) A] are connected by four syn-syn benzoate ligands. The apical positions of the square-pyramidal zinc coordination polyhedra are occupied by the N atoms of the papaverine ligand. Upon coordination, the mutual orientation of the phenyl and isoquinoline rings in papaverine is changed compared with that in the uncoordinated ligand.

Full text of DOI:10.1107/S010827010302883X

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
The molecular structure of (I) (Fig. 1) consists of discrete
centrosymmetric [Zn2(C6H5COO)4(C20H21NO4)2] dimers of
the paddle-wheel cage type, with an inversion centre located at
the mid-point of the ZnÁ Á ÁZn vector. This structure type was
®rst described in 1953 for copper acetate monohydrate (van
Nieker & Schoening, 1953) and has since been observed for a
variety of transition metals (Mehrotra & Bohra, 1983). In the
structure of (I), the pair of ZnII atoms is bridged by four syn±
syn benzoate ligands. The O atoms of these ligands are posi-
tioned in the basal plane of a tetragonal pyramid around each
ZnII atom (ꢀ = 0.0; Addison et al., 1984), while the apical
position is occupied by the N atom of the papaverine mol-
ISSN 0108-2701
Tetra-l-benzoato-j8O:O0-bis({1-[(3,4-
dimethoxyphenyl)methyl]-6,7-di-
methoxyisoquinoline-jN}zinc(II)):
the first crystal structure with
papaverine as a ligand
Ê
ecule. The Zn atom is shifted 0.412 (1) A from the basal plane
toward the apical position. Among ZnII±carboxylate com-
plexes, a similar coordination type was found in some aliphatic
carboxylates, for example, acetate (Singh et al., 1997) and
crotonate (Clegg et al., 1986, 1995).
a
a
b
Ï
Â
Â
Vladimõr Zelenak, * Michal Sabo, Werner Massa and
a
Ï
Â
Juraj Cernak
a
Æ
Â
Institute of Chemical Science, Faculty of Science, P. J. Safarik University,
Moyzesova 11, SK-041 54 Kosice, Slovak Republic, and bFachbereich Chemie
Ï
der Philipps-Universitat, Hans-Meerwein-Straûe, D-35043 Marburg, Germany
È
Correspondence e-mail: zelenak@kosice.upjs.sk
Received 8 December 2003
Accepted 15 December 2003
Online 31 January 2004
The title complex, [Zn2(C7H5O2)4(C20H21NO4)2], forms
dimers of the paddle-wheel cage type located at crystal-
lographic inversion centres. The two Zn atoms
Ê
[ZnÁ Á ÁZn = 3.0533 (4) A] are connected by four syn±syn
benzoate ligands. The apical positions of the square-pyramidal
zinc coordination polyhedra are occupied by the N atoms of
the papaverine ligand. Upon coordination, the mutual
orientation of the phenyl and isoquinoline rings in papaverine
is changed compared with that in the uncoordinated ligand.
Ê
The average ZnÐO bond length [2.048 (8) A; Table 1] is
slightly longer than those observed for structurally char-
acterized paddle-wheel zinc(II) complexes of formula
Ê
[Zn2(RCOO)4L2], with average values of 2.043 A (where
RCOO is crotonate and L is quinoline; Clegg et al., 1986),
Ê
2.037 A (where RCOO is crotonate and L is 4-cyanopyridine;
Ê
Clegg et al., 1995), 2.038 and 2.041 A (where RCOO is acetate
and L is pyridine; Singh et al., 1997), and 2.034, 2.039 or
Ê
2.042 A (where RCOO is indomethacin and L is 1-methyl-
pyrrolidinone, pyridine or dimethylacetamide; Zhou et al.,
Comment
Papaverine, or 1-[(3,4-dimethoxyphenyl)methyl]-6,7-dimeth-
oxyisoquinoline, is an alkaloid that is used as a vasodilator in
cardiac and kidney surgery (Ali et al., 1997; Zacherl et al.,
2002). When applied to human organisms, it can interact with
a number of metal ions present in the body. One way to
understand these metal±drug interactions is to study struc-
tures of metal complexes containing the drug as a ligand.
There are a number of examples of such structural studies
(Cini, 2000), although reports dealing with properties of metal
complexes of papaverine are scarce (e.g. Sabirov et al., 1994;
2000). As
[3.0533 (4) A] in (I) is longer than those in the above-
a
consequence, the ZnÁ Á ÁZn separation
Ê
Â
È
Â
mentioned complexes, which exhibit ZnÁ Á ÁZn separations of
Melnõk et al., 1996; Gyoryova et al., 2002; Williams et al., 2003).
The crystal structures of papaverine and its hydrochloride salt
have already been described (Marek et al., 1996; Reynolds et
al., 1974). Moreover, the papaverinium cation as the counter-
ion in a cobalt-containing complex has been structurally
characterized (Sabirov et al., 1994). However, the Cambridge
Structural Database (Allen, 2002) does not contain an entry of
a crystal structure with papaverine as a ligand. The present
study ®lls this gap; we describe here the structure of a zinc(II)
benzoate complex, (I), of papaverine.
Ê
less than 3 A.
The geometric parameters in the papaverine ligand are
close to those observed for the free base (Marek et al., 1996).
The most remarkable differences were observed in the O5Ð
Ê
Ê
C31 [1.384 (3) A] and O6ÐC32 [1.381 (4) A] bond lengths,
which are shorter than the respective values in free papaverine
Ê
[1.415 (5) A (2Â); Marek et al., 1996]. This difference may be
due to the strongly anisotropic displacement parameters
within the peripheral groups. Moreover, as a result of the
Acta Cryst. (2004). C60, m85±m87
DOI: 10.1107/S010827010302883X
# 2004 International Union of Crystallography m85

metal-organic compounds
Figure 1
A view of the title centrosymmetric dimer, with the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms
are shown as spheres of arbitrary radii.
coordination of papaverine, a change in the orientation of the
phenyl and isochinoline rings is observed. The C25ÐC26Ð
C27 angle [112.2 (1)ꢁ] changes only slightly [115.2 (3)ꢁ in the
free base, 112.2ꢁ in the hydrochloride and 113.8 (8)ꢁ in the
cobalt complex containing the papaverinium cation]. More
important changes are observed in the torsion angles. The
C28ÐC27ÐC26ÐC25 torsion angle in (I) is 134.1 (2)ꢁ,
while the angles in free papaverine and papaverine hydro-
chloride are 117.9 (4) and 80.5ꢁ, respectively (Marek et al.,
1996; Reynolds et al., 1974). The value of this torsion angle in
the cobalt complex containing the papaverinium cation is
63 (1)ꢁ (Sabirov et al., 1994). Similarly, a difference was
observed in the C27ÐC26ÐC25ÐN1 torsion angle
[ 106.6 (2)ꢁ, c.f. 112.7 (3)ꢁ in the free base, 84.8ꢁ in the
hydrochloride salt and 112.8 (9)ꢁ in the cation in the cobalt
complex]. This change in the mutual orientation of the rings
may be a result of both steric hindrance of benzoate ligands
and non-bonding interactions.
From the composition of complex (I), it is obvious that no
conventional hydrogen bonds can be expected in the structure.
The molecules are held together only by CÐHÁ Á ÁO and van
der Waals interactions. The most important CÐHÁ Á ÁO inter-
Figure 2
A view along the a axis, showing the intermolecular CÐHÁ Á ÁO contacts
molecular contacts shorter than the sum of the van der Waals
(dashed lines) in the planes parallel to bc. One such plane is displayed
radii are shown in Fig. 2 and listed in Table 2. These CÐHÁ Á ÁO
fully. For the adjacent plane, only the dimeric cages (grey) are shown for
intermolecular interactions connect the dimers into sheets
the sake of clarity. Benzoate ligands not involved in the contacts have also
been omitted.
parallel to the bc plane.
ꢀ
Â
Ï Â
m86 Vladimõr Zelenak et al.
[Zn2(C7H5O2)4(C20H21NO4)2]
Acta Cryst. (2004). C60, m85±m87

metal-organic compounds
Table 1
Selected geometric parameters (A, ).
Experimental
ꢁ
Ê
In a typical procedure, papaverine hydrochloride (5 g, 13.30 mmol)
was dissolved in water (150 ml). To this solution, an equimolar
amount of sodium hydroxide (0.532 g) dissolved in water (25 ml) was
added dropwise with vigorous stirring. The precipitated white papa-
verine powder was ®ltered off, washed with water and dried. Sodium
benzoate (0.5 g, 3.47 mmol) dissolved in absolute ethanol (25 ml) was
mixed with an ethanol solution (25 ml) of zinc chloride (0.236 g,
1.73 mmol). After the solution had been stirred for 30 min, it was
®ltered and an ethanol solution (30 ml) of papaverine (1.178 g,
3.47 mmol) was added to the ®ltrate. The reaction mixture was stirred
for 1 h, and then ®ltered and left to stand at room temperature.
Within a week, colourless crystals appeared. Recrystallization from
ethanol gave crystals suitable for X-ray diffraction.
ZnÐO2A
ZnÐO1A
ZnÐO1Bi
2.0404 (12)
2.0470 (13)
2.0494 (14)
ZnÐO2Bi
ZnÐN1
ZnÁ Á ÁZni
2.0562 (13)
2.0812 (16)
3.0533 (4)
O2AÐZnÐO1A
O2AÐZnÐO1Bi
O1AÐZnÐO1Bi
O2AÐZnÐO2Bi
O1AÐZnÐO2Bi
O2AÐZnÐN1
87.17 (6)
87.24 (6)
156.69 (6)
156.84 (6)
89.17 (7)
106.20 (6)
O1AÐZnÐN1
O1BiÐZnÐN1
O2BiÐZnÐN1
O1BÐC1ÐO1A
O2BÐC8ÐO2A
C25ÐC26ÐC27
93.79 (6)
109.50 (6)
96.86 (6)
125.01 (17)
125.90 (16)
112.22 (13)
Symmetry code: (i) x; y; z.
Table 2
Short intermolecular CÐHÁ Á ÁO contacts (A) and angles (ꢁ) for
Ê
Crystal data
compound (I).
[Zn2(C7H5O2)4(C20H21NO4)2]
Mr = 1293.98
Monoclinic, P21=n
Mo Kꢂ radiation
Cell parameters from 8002
re¯ections
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
ꢃ = 3.0±30.3ꢁ
Ê
a = 14.1780 (9) A
C3ÐH3Á Á ÁO3ii
C4ÐH4Á Á ÁO4ii
C5ÐH5Á Á ÁO6iii
0.95
0.95
0.95
2.53
2.68
2.70
3.364 (2)
3.312 (2)
3.454 (2)
147
125
137
1
Ê
b = 14.4118 (6) A
ꢄ = 0.84 mm
T = 193 (1) K
Ê
c = 15.5442 (11) A
ꢁ = 101.799 (8)ꢁ
Block, colourless
0.60 Â 0.45 Â 0.38 mm
3
Ê
V = 3109.0 (3) A
Symmetry codes: (ii) x; 1 y; z; (iii) x; y; z 1.
Z = 2
Dx = 1.382 Mg m
3
Data collection
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ꢀ
Â
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Acta Cryst. (2004). C60, m85±m87
Vladimõr Zelenak et al.
[Zn2(C7H5O2)4(C20H21NO4)2] m87