Synthesis and Characterization of Copper(II) and Zinc(II) Complexes Containing 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone

Article abstract of DOI:10.1515/znb-2003-1012

The synthesis, structure, and physical properties of a series of mononuclear complexes viz. [Cu(L)₂] 1, [CuL₂(CH ₃O)₂] 2 and [Zn(L)₂] 3 (where L = 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP)) are presented. The complexes were characterized by elemental analysis, IR and electronic spectroscopy (1 and 2), magnetic measurements at room temperature (1 and 2) and thermogravimetric analysis. The structures of all the three complexes were determined by single crystal X-ray diffraction studies. The coordination geometry around complexes CuL₂ (1) and ZnL₂ (3) is slightly distorted square planar while the geometry around Cu(II) of [Cu(L)₂(CH₃O) ₂] (2) is distorted octahedral with four oxygen atoms of two PMBP ligand occupying the equatorial positions and two methanol molecules occupying the two axial positions.

Full text of DOI:10.1515/znb-2003-1012

Synthesis and Characterization of Copper(II) and Zinc(II)
Complexes Containing 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone
Subrata Kumar Deya, Bappaditya Baga, Dilip Kumar Deyb, V. Gramlichc, Yadong Lid,
and Samiran Mitraa,∗
a Department of Chemistry, Jadavpur University, Kolkata – 700 032, India
b Department of Chemistry, Chandidas Mahavidyalaya, Khujutipara – 731215, District-Birbhum,
West Bengal, India
c Department of Chemistry, Laboratium fu¨r Kristallographie ETH,
Eidgeno¨ssische Technische Hochschule Zu¨rich, CH-8092 Zu¨rich, Switzerland
d Department of Chemistry, Tsnighua University, Beijing 100 084, P.R. China
Reprint requests to Prof. S. Mitra. Fax: 9133 2414 6266. E-mail: smitra 2002@yahoo.com
Z. Naturforsch. 58b, 1009 – 1014 (2003); received June 25, 2003
The synthesis, structure, and physical properties of a series of mononuclear complexes viz.
[Cu(L)2] 1, [CuL2(CH3O)2] 2 and [Zn(L)2] 3 (where L = 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone
(PMBP)) are presented. The complexes were characterized by elemental analysis, IR and electronic
spectroscopy (1 and 2), magnetic measurements at room temperature (1 and 2) and thermogravi-
metric analysis. The structures of all the three complexes were determined by single crystal X-ray
diffraction studies. The coordination geometry around complexes CuL2 (1) and ZnL2 (3) is slightly
distorted square planar while the geometry around Cu(II) of [Cu(L)2(CH3O)2] (2) is distorted oc-
tahedral with four oxygen atoms of two PMBP ligand occupying the equatorial positions and two
methanol molecules occupying the two axial positions.
Key words: PMBP Complex, Crystal Structure, Copper and Zinc Ions
Introduction
The coordination chemistry of zinc is of consider-
able interest [9]. The active binding sites of zinc could
be applied in highly efficient and catalytic reactions by
using a variety of coordination possibilities such as the
variability and flexibility of ligands in biologically rel-
evant coordination spheres [10]. Since changes in coor-
dination geometry due to the flexibility of the binding
ability of ligands can lead to an open position at the
metal ion site, these may be beneficial for catalytic re-
actions to occur [11]. The ligands containing imidazole
or substituted imidazole groups, similar to pyrazole or
substituted pyrazole groups are known to occur in met-
alloproteins [12].
It has been noticed that copper(II) complexes as
anti-inflammatory drugs are often more active than the
parent ligands themselves [1]. In recent years, several
works have appeared concerning models of copper en-
zymes [2 – 4]. This growing interest in mimicking the
active sites of metalloproteins has a major contribu-
tion to the development of new ideas and trends in
coordination chemistry. The coordination chemistry of
pyrazole derived ligands has received much attention,
primarily due to their biological implications. Sev-
eral studies have centered around synthesis and struc-
tural studies of metal complexes of pyrazole contain-
ing bidentate ligands (N, O donors) due to the reported
anticarcinogenic and antiviral activity of these donor
ligands and complexes obtained from them. It has
been reported that substituted pyrazolones, pyrazolines
and pyrazoles have potential biological activity [5, 6].
Derivatives of 2-pyrazolines-5-ones have been studied
for their importance as antipyretics and analgetics [7].
2-Pyrazolones and their nitroso derivatives have been
found to be effective germicides and fungicides [8].
In this paper we describe the synthesis, physical
properties and crystal structures of three neutral com-
plexes of copper(II) and zinc(II) ions containing 1-
phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP).
Experimental Section
Materials
All chemicals were of reagent grade. Copper acetate, zinc
acetate and methanol were used as received. 1-Phenyl-3-
c
0932–0776 / 03 / 1000–1009 $ 06.00 ꢀ 2003 Verlag der Zeitschrift fu¨r Naturforschung, Tu¨bingen · http://znaturforsch.com
Brought to you by | University Paris-Sud
Authenticated
Download Date | 4/26/19 8:28 PM

1010
S. K. Dey et al. · Cu(II) and Zn(II) Complexes Containing 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone
Table 1. Crystal data and structure refinement for 1, 2 and 3.
1
2
C36 H32 N4 Cu O6
680.20
3
C34 H26 N4 Zn O4
619.96
Empirical formula
Formula weight
C34 H26 N4 Cu O4
618.13
Temperature
Wavelength
296(2) K
0.71073 A
293(2) K
1.54178 A
293(2) K
1.54178 A
˚
˚
˚
Crystal system, space group
Unit cell dimensions
monoclinic, P21/c
monoclinic, P21/c
monoclinic, P21/c
˚
˚
˚
a = 6.8347(6) A
a = 11.08(2) A
a = 6.843(6) A
b = 23.868(13) A
˚
˚
˚
b = 23.857(2) A
b = 15.91(2) A
˚
˚
˚
c = 9.1596(8) A
c = 9.438(8) A
c = 9.172(5) A
α = 90◦
α = 90◦
α = 90◦
β = 108.993(2)◦
β = 103.92(10)◦
β = 108.92(5)◦
γ = 90◦
γ = 90◦
γ = 90◦
3
3
3
˚
˚
˚
Z, Volume
2, 1412.2(2) A
2, 1615(3) A
2, 1417(2) A
Density (calculated)
Absorption coefficient
Crystal size
Theta range for data collection
Index ranges
1.454 g cm−3
0.821 mm−1
,
1.398 g cm−3
,
1.453 g cm−3
1.392 mm−1
1.591 mm−1
0.25×0.20×0.10 mm
0.10×0.08×0.06 mm
4.11 to 50.00◦
0.10×0.07×0.04 mm
◦
2.50 to 33.48
3.70 to 49.98◦
−10 ≤ h ≤ 10,
0 ≤ h ≤ 11,
−6 ≤ h ≤ 6,
−37 ≤ k ≤ 34, −9 ≤ l ≤ 13
13429 / 5238 [R(int) = 0.0621]
Full-matrix least-squares on F2
5238 / 248
−15 ≤ k ≤ 0, −9 ≤ l ≤ 9
1642 / 1642 [R(int) = 0.0000]
Full-matrix least-squares on F2
1642 / 217
0 ≤ k ≤ 23, 0 ≤ l ≤ 9
1455 / 1455 [R(int) = 0.0000]
Full-matrix least-squares on F2
1455 / 197
Reflections collected / unique
Refinement method
Data / parameters
Goodness-of-fit on F2
Final R indices
0.954
R1 = 0.0623,
1.057
R1 = 0.0486,
1.018
R1 = 0.0460,
[I > 2σ(I)]
R Indices (all data)
wR2 = 0.1230
R1 = 0.1365,
wR2 = 0.1293
R1 = 0.0569,
wR2 = 0.1190
R1 = 0.0618,
wR2 = 0.1505
0.399 and −0.256 e /A
wR2 = 0.1382
0.643 and −0.342 e /A
wR2 = 0.1309
0.401 and −0.408 e /A
3
3
3
˚
˚
˚
Largest diff. peak and hole
methyl-5-pyrazolone was received from Lancaster and used methods (SHELXS-97) [13] and refined on F2 by full-matrix
without any purification.
least-squares using all unique data (SHELXL-97) [14]. For
1, 2 and 3, all non-hydrogen atoms were refined anisotrop-
ically and the hydrogen atoms were included in calculated
positions (riding model). The structures were finally refined
to the conventional R-values of 0.0623, 0.0486 and 0.0460
for 1, 2 and 3, respectively. The crystal data, the conditions
for the intensity data collection, and important features of
the structural refinements for the compounds are listed in Ta-
ble 1. Selected bond lengths and angles are presented in Ta-
ble 2. Crystallographic data have been deposited at the Cam-
bridge Crystallographic Data Center with deposition num-
bers 208954 – 208956. Copies of the information may be ob-
tained free of charge from The Director, CCDC, 12 Union
Road, Cambridge, CB2 1EZ, UK (Fax: +44 1233 336033;
E-mail: deposit@ccdc.cam.ac.uk).
Physical measurements
Elemental analyses were carried out using a Perkin-Elmer
2400 II elemental analyzer. Infrared spectra of the com-
plexes were recorded on a Perkin-Elmer 883-IR spectropho-
tometer using KBr pellets, the UV-vis spectra with a Perkin
Elmer λ-40 (UV-VIS) spectrophotometer in acetonitrile so-
lution and in solid state using nujol. The magnetic suscep-
tibility was measured for the solid samples at room tem-
perature using a vibrating sample magnetometer using mer-
cury (tetrathiocyanato) cobaltate as a standard. TGA analyses
were carried out on a Shimadzu TGA – 50 thermal analyzer
under a dynamic nitrogen environment.
X-ray crystallography
Synthesis of the ligand
X-ray intensity data for the complexes 1, 2 and 3 were col-
1-Phenyl-3-methyl-5-pyrazolone (7.5 g) was dissolved in
lected on a CAD 4 diffractometer using graphite - monochro- 80 ml of 1,4-dioxane by heating. Calcium hydroxide (12 g)
matized Mo-Kα radiation for 1 and Cu-Kα for 2 and 3 (λ = was added followed by addition of benzoyl chloride (5 ml)
˚
˚
0.71073 A for 1 and 1.54178 A for 2 and 3 respectively). dropwise within 1 min. The temperature increased during the
The lattice constants were determined by least squares re- first few minutes and the reaction mixture became a thick
finements of the setting angle for 25 reflections (33.48 ≥ θ ≥ paste. The reaction mixture was refluxed for 30 min. Cal-
2.50) for 1, (50.00 ≥ θ ≥ 4.11) for 2 and (49.98 ≥ θ ≥ 3.70) cium complex of the desired ligand formed in the flask was
for 3, respectively. The structures were solved by direct decomposed by pouring the mixture into dilute hydrochlo-
Brought to you by | University Paris-Sud
Authenticated
Download Date | 4/26/19 8:28 PM

S. K. Dey et al. · Cu(II) and Zn(II) Complexes Containing 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone
1011
˚
Table 2. Bond lengths [A] and angles [deg] for 1, 2 and 3.
1:
Cu(1)-O(1)
1.9068(17) Cu(1)-O(2)
1.9189(17)
O(1)-Cu(1)-O(1)#1 180.0
O(1)-Cu(1)-O(2)#1 86.53(7)
O(2)#1-Cu(1)-O(2) 180
O(1)-Cu(1)-O(2)
93.47(7)
2:
Cu(1)-O(1)
Cu(1)-O
2.033(3)
2.152(4)
Cu(1)-O(2)
2.108(4)
O(1)-Cu(1)-O(1)#1 180
O(1)-Cu(1)-O(2)#1 90.63(13)
89.37(13) O(2)#1-Cu(1)-O(2) 180
88.37(12) O(1)-Cu(1)-O 91.63(12)
O(2)#1-Cu(1)-O(1) 92.5(2)
O(1)-Cu(1)-O(2)
O(1)-Cu(1)-O#1
O(2)-Cu(1)-O
O#1-Cu(1)-O
87.5(2)
180
3
Zn(1)-O (1)
1.909(3)
Zn(1)-O(2)
O(1)-Zn(1)-O(2)#1 86.59(13)
93.41(13) O(2)#1-Zn(1)-O(2) 180
1.922(3)
O(1)-Zn(1)-O(1)#1 180
O(1)-Zn(1)-O(2)
ric acid (100 ml). An orange precipitate was formed slowly.
It was filtered under suction, washed with a little water
and 1,4-dioxane, and recrystallised from a slightly acidified
methanol-water mixture to destroy any undecomposed cal-
cium complex.
Fig. 1. Ortep plot of complex 1 with atom numbering
scheme.
to ν(NH) stretching and may also be due to the pres-
ence of methanol which is also confirmed by the crys-
tal structure analysis for the complex 2. For the other
two complexes several bands appeared in the range
2885, 2954, 2988, 3000 cm−1, assigned to aliphatic
C-H stretching vibrations. It is reasonable to assign the
two bands at 425 and 495 cm−1 as ν(Cu-O) stretching
mode [15].
Synthesis of the complexes
The complex [Cu(PMBP)2] 1 was prepared by the addi-
tion of the ligand (PMBP) to a methanolic solution of cop-
per acetate in 2:1 ratio. The resulting mixture was stirred for
25 min. and then it was kept at r.t. Green rectangular shaped
crystals appeared after 10 d, from which crystals suitable for
X-ray analysis were separated. Yield: 85%.
Analysis for [Cu(PMBP)2]: calcd. C 66.01, H 4.20,
N 9.05, Cu 10.27; found C 65.99, H 4.11, N 9.01, Cu 10.31.
The complex [Cu(PMBP)2(CH3O)2] 2 was prepared by
the addition of the ligand (PMBP) to an aqueous-methanolic
solution of copper acetate in 2:1 ratio. The resulting mixture
was kept at r.t. from which shiny green rectangular shaped
crystals appeared after 7 d. Yield: 77%.
Electronic studies
The electronic spectrum of complex 1 in dichloro-
methane exhibited the metal-to-ligand charge transfer
band at 460 nm, which is comparable to those of pre-
viously reported complexes [16]. The electronic spec-
Analysis for [Cu(PMBP)(CH3O)2]: calcd. C 66.51, trum of complex 2 in methanol showed a weak absorp-
H 4.70, N 8.23, Cu 9.34; found C 66.53, H 4.73, N 8.27,
Cu 9.36.
tion at 675 nm followed by several intense absorptions
in the range 600– 670 nm which for copper(II) com-
plexes of Schiff bases and related ligands are assigned
to d-d transitions [17– 19]. The intense absorptions are
most probably due to the ligand-to-metal charge trans-
fer and intraligand transitions.
The complex [Zn(PMBP)2] 3 was prepared by the addi-
tion of a methanolic solution of zinc acetate to a methanolic
solution of PMBP ligand in 2:1 ratio. Light yellow square
shaped crystals appeared after 8 d from which crystals suit-
able for X-ray analysis were separated. Yield: 75%.
Analysis for [Zn(PMBP)2]: calcd. C 65.82, H 4.20,
N 9.07, Zn 10.57; found C 65.81, H 4.19, N 9.03, Zn 10.55.
Thermal studies
It is observed from the TGA curve that on
heating under non-isothermal condition, complex 2
Result and Discussion
Infrared studies
loses two molecules of methanol in the temperature
◦
The IR spectra of the complexes show several strong range 75– 85 C. Then it underwent decomposition
bands in the range of 2844– 3345 cm−1, which are due at higher temperature resulting in the formation of
Brought to you by | University Paris-Sud
Authenticated
Download Date | 4/26/19 8:28 PM

1012
S. K. Dey et al. · Cu(II) and Zn(II) Complexes Containing 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone
Fig. 3. Ortep plot of complex 2 with atom numbering
scheme.
with intermolecular contacts through nitrogen atoms of
the pyrazole ring with copper is given in Fig. 2. The
bond lengths and angles for complex 1 are listed in
Table 2. In the discrete molecule the central copper
ion is attached to four oxygen atoms of deprotonated
1-phenyl-3-methyl-4-benzoyl-5-pyrazolone ligands at
the four equatorial positions. In the equatorial plane
the trans angles [O(1)-Cu(I)-O(3) and O(2)-Cu(I)-
O(4)] are exactly 180◦ while the bite angles deviate
slightly from 90◦ [O(1)-Cu(1)-O(2) = 93.47◦; O(2)-
Cu(1)-O(3) = 86.53◦]. Each ligand molecule forms a
six-membered ring with the metal ion. The distortion
of the structure from square planar to tetrahedral can
be evaluated through the parameter ∆ introduced by
Galy et al. [20] and applied by Ribas and Kahn [21].
Fig. 2. The packing diagrams of complex 1.
copper oxide, which was confirmed by qualitative
test.
˚
Magnetic susceptibility
Cu-O bond lengths 1.9086(17) and 1.9189(17) A are
well comparable with the Cu-O bond lengths found
in other Cu(II) complexes. Comparable distances be-
tween Cu(1)-O(1) and Cu(1)-O(2) indicate that delo-
calization of the negative charge occurs between O(1)
and O(2) of the ligand.
The room temperature magnetic moments (1.72 µB
for 1 and 1.74 µB for 2) of the complexes are very close
to the spin only values for copper(II) systems.
Structural discussion
The crystals of complex [Cu(PMBP)2(CH3O)2]
The X-ray structural investigation of [Cu(PMBP)2] 2 contain discrete molecules. Here also four oxy-
1 shows that in this compound copper(II) ions have a gen atoms of two deprotonated 1-Phenyl-3-methyl-4-
four coordinate square planar structure with slight dis- benzoyl-5-pyrazolone ligand occupy the four equato-
tortion. An ORTEP plot along with the atom number- rial positions of a distorted octahedron around Cu(II)
ing scheme of [Cu(PMBP)2] is given in Fig. 1 and the like the square planar coordination in Cu(PMBP)2 1.
packing arrangement of the molecules in the unit cell The two CH3OH molecules are coordinated to cop-
Brought to you by | University Paris-Sud
Authenticated
Download Date | 4/26/19 8:28 PM

S. K. Dey et al. · Cu(II) and Zn(II) Complexes Containing 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone
1013
the square planar [Cu(PMBP)2] 1. The negative charge
of the ligand is also delocalized over the two oxy-
gen atoms as evidenced from the O-C bond distances
˚
˚
[O(2)-C(1”) = 1.258(5) A; O(1)-C(5) = 1.273(5) A].
The copper atom is located at a center of inversion.
In [Cu(PMBP)2(CH3O)2], the two independent Cu-O
bond lengths [Cu(1)-O(1) = 2.033(3), Cu(1)-O(2) =
˚
2.108(4) A] are comparable with the Cu-O distances of
other reported copper complexes but longer than those
found in square planar [Cu(PMBP)2] 1. A methanol
molecule is coordinated to Cu(II) from a more distant
˚
position [Cu(1)-O = 2.152(4) A].
X-ray structural investigation of [Zn(PMBP)2] 3 in-
dicates that the Zn(II) ion is surrounded by four oxy-
gen atoms of two deprotonated 1-Phenyl-3-methyl-
4-benzoyl-5-pyrazolone ligands in a square planar
geometry. An ORTEP plot along with the atom
numbering scheme is given in Fig. 4. The bond
lengths and angles are listed in Table 2. The dis-
crete molecule of [Zn(PMBP)2] 3 possesses a slightly
distorted square planar geometry. Here also trans
angles [O(1)#1-Zn(1)-O(1), O(2)-Zn(1)-O(2)#1] are
180◦ by symmetry and the cis angles (O(1)#1-Zn(1)-
O(2) = 86.59(13)◦; O(1)-Zn(1)-O(2) = 93.41(13)) de-
viate slightly from 90◦, but are similar to [Cu(PMBP)2]
1. The Zn-O bond distances [Zn(1)-O(1) = 1.909(3);
Fig. 4. Ortep plot of complex 3 with atom numbering
scheme.
per(II) by their oxygen atoms and occupy the trans ax-
ial positions.
An ORTEP plot of complex [Cu(PMBP)2(CH3O)2]
2 along with the atom numbering scheme is given
in Fig. 3. The bond distances and angles are
listed in Table 2. The central Cu(II) center in
[Cu(PMBP)2(CH3O)2] possesses a slightly distorted
octahedral geometry with trans angles at 180◦. The
cis angles [O(1)-Cu(1)-O(2), 89.37(13)◦; O(1)-Cu(1)-
O(2)#1, 90.63(13)◦] deviates slightly from 90◦. In the
compound [Cu(PMBP)2(CH3O)2] 2, the distortion of
˚
Zn(1)-O(2) = 1.922(3) A] are comparable with the Zn-
O bond distances found in similar compounds.
Acknowledgements
Financial assistance to Dr. S. K. Dey by CSIR, New Delhi,
cis angles from 90◦ are small in comparison to that of India is gratefully acknowledged.
[1] J. R. J. Sorenson, Prog. Med. Chem. 26, 437 (1989) and [11] R. P. Bonomo, E. Conte, R. Marchelli, A. M. Santoro,
refs. therein.
G. Tabbi, J. Inorg. Biochem. 53, 127 (1994).
[12] G. E. Morris, B. F. Anderson, E. N. Baker, J. Am.
Chem. Soc. 108, 2784 (1986).
[13] G. M. Sheldrick, Acta Crystallogr. Sect. A 46, 457
(1990).
[14] G. M. Sheldrick, SHELXL-97 Program for Crystal
Structure Refinement, University of Go¨ttingen, Ger-
many (1997).
[2] K. D. Karlin, Z. Tyeka´r, Bioinorganic Chemistry of
Copper, Chapman and Hall, New York (1993).
[3] T. N. Sorel, Tetrahedron 45, 3 (1989).
[4] P. Chaudhuri, Multi-copper Oxidases, World Scientific,
Singapore (1997).
[5] M. A. Metwally, M. Y. Youshif, A. M. Osmaiel, F. A.
Amo, J. Ind. Chem. Soc. 62, 54 (1988).
[6] T. C. Sharma, M. M. Bokadia, N. J. Reddy, Ind. J.
Chem. 19B, 228 (1980).
[15] L. K. Singh, S. Mitra, J. Chem. Soc., Dalton Trans.
2089 (1987).
[7] J. M. Sala, G. M. Puigmarti, P. Gomis, J. M. Caldero,
M. Izqueirodo, A. Gwards, Chim. Ther. 2, 272 (1967).
[8] S. K. Mohanty, R. Sridhar, S. Y. Padmanaran, S. Rao,
A. S. Mitra, Ind. J. Chem. 15B, 1146 (1977).
[9] T. G. Spiro, Zinc Enzymes, Wiley, New York (1983).
[10] R. J. P. Williams, Pure Appl. Chem. 54, 1889 (1982).
[16] (a) A. J. Pallenberg, K. S. Koenig, D. M. Barnhart, In-
org. Chem. 34, 2833 (1995); (b) D. J. Darensbourg,
M. W. Holteamp, B. Khandelwal, K. K. Klausmeyer,
J. H. Reibenspies, Inorg. Chem. 34, 2389 (1995).
[17] N. R. Sangeetha, K. Baradi, R. Gupta, C. K. Pal,
V. Manivannan, S. Pal, Polyhedron 18, 1425 (1999).
Brought to you by | University Paris-Sud
Authenticated
Download Date | 4/26/19 8:28 PM

1014
S. K. Dey et al. · Cu(II) and Zn(II) Complexes Containing 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone
[18] H. S. Masle, T. N. Waters, Coord. Chem. Rev. 17, 137
(1975).
[20] J. Galy, J. J. Bonnet, S. Anderson, Acta Chem. Scand.
A33, 383 (1979).
[19] S. Karunakaran, M. Kandaswamy, J. Chem. Soc., Dal-
ton Trans. 1851 (1995).
[21] J. Ribas, C. Diaz, R. Costa, Y. Journaux, C. Math-
oniere, O. Kahn, A. Gleizes, Inorg. Chem. 29, 2042
(1990).
Brought to you by | University Paris-Sud
Authenticated
Download Date | 4/26/19 8:28 PM