Coordination compounds of copper(II) with benzoylhydrazones of substituted salicylaldehydes

Article abstract of DOI:10.1023/B:RUGC.0000016032.80593.ec

Benzoylhydrazones of 5-nitro- (H₂L¹), 3-nitro- (H₂L²), 5-chloro- (H₂L³), 5-bromo- (H₂L⁴), and 3,5-dibromosalicylaldehydes (H ₂L⁵) react in ethanol with copper acetate to form complexes CuL^1-5. In the presence of amines (A = C₅H ₅N, 3-CH₃C₅H₄N), the above reactions give complexes CuL^1-5A·nH₂O (n = 0, 1). When cuprous bromide or nitrate and benzoylhydrazone H₂L³ were used as starting materials, complexes Cu(HL³)X (X = Br^-, NO₃^-) were isolated. The resulting complexes all are polynuclear structures in which azomethines H₂L^1-5 behave as tridentate O,N,O-ligands. Thermolysis of the complexes involves the stages of dehydration (70-90°C), deaquation (120-150°C) or deamination (150-180°C), and complete thermal decomposition (350-500°C).

Full text of DOI:10.1023/B:RUGC.0000016032.80593.ec

Russian Journal of General Chemistry, Vol. 73, No. 10, 2003, pp. 1611 1615. Translated from Zhurnal Obshchei Khimii, Vol. 73, No. 10, 2003,
pp. 1704 1708.
Original Russian Text Copyright
2003 by Samus’, Tsapkov, Kerner.
Coordination Compounds of Copper(II)
with Benzoylhydrazones of Substituted Salicylaldehydes
N. M. Samus’, V. I. Tsapkov, and A. V. Kerner
Moldova State University, Kishinev, Moldova
Received January 28, 2002
Abstract Benzoylhydrazones of 5-nitro- (H2L1), 3-nitro- (H2L2), 5-chloro- (H2L3), 5-bromo- (H2L4), and
3,5-dibromosalicylaldehydes (H2L5) react in ethanol with copper acetate to form complexes CuL1 5. In the
presence of amines (A = C5H5N, 3-CH3C5H4N), the above reactions give complexes CuL1 5A nH2O (n = 0,
1). When cuprous bromide or nitrate and benzoylhydrazone H2L3 were used as starting materials, complexes
Cu(HL3)X (X = Br , NO3) were isolated. The resulting complexes all are polynuclear structures in which
azomethines H2L1 5 behave as tridentate O,N,O-ligands. Thermolysis of the complexes involves the stages of
dehydration (70 90 C), deaquation (120 150 C) or deamination (150 180 C), and complete thermal de-
composition (350 500 C).
Hydrazine derivatives occupy a special place
among organic ligands because of the diversity of
their donor atoms and the ability to change dentacity
depending on given reaction conditions [1]. Many
hydrazine derivatives are known to be biologically
active [2], and their activity is enhanced many times
by coordination with biometals [3 5]. It is also known
[6 8] that the physiological activity of coordination
compounds is controlled by the properties both of the
biologically active ligand and of the complexing metal.
In this connection, accumulation of experimental data
on the synthesis of coordination compounds of bio-
metals with hydrazones is both of scientific and of
practical interest.
I V as fine crystals. According to the elemental
analyses (Table 1), the products have the composition
1 5
CuL1 5 [HL = H2L1 (I), H2L2 (II), H2L3 (III), H2L4
(IV), and H2L5 (V)]. Cupric bromide and nitrate under
the same conditions give with the azomethine H2L3
complexes Cu(HL)X [X = Br (VI), NO3 (VII)]. The
reactions between copper acetate and hydrazones
(H2L1 5), performed in the presence of pyridine or
3-picoline, yields complexes CuAL1 5 nH2O [A =
C5H5N (VIII X, XII, XIII), 3-CH3C5H4N (XI);
H2L1 5 = H2L1 (VIII), H2L2 (IX), H2L3 (X, XI), H2L4
(XII), H2L5 (XIII); n = 0 (VIII, IX, XI XIII), n = 1
(X)].
Complexes I XIII are insoluble in water, alcohols,
and ether and readily soluble in DMF and DMSO.
Their yields and physicochemical properties are given
in Table 1.
The aim of the present study was to find the best
conditions of synthesis, to determine the structure, and
to study the physicochemical properties of copper (II)
complexes with benzoylhydrazones H2L1 5 of 5-nitro-
(H2L1), 3-nitro- (H2L2), 5-chloro- (H2L3), 5-bromo-
(H2L4), and 3,5-dibromosalicylaldehydes (H2L5) .
Magnetochemical investigation of complexes I
XIII at room temperature showed (Table 1) that their
effective magnetic moments are lower than those
expected for the spin value for one unpaired electron.
As follows from these data, complexes I XIII have a
polynuclear structure in which there is spin spin
coupling between the paramagnetic copper ions.
R2
OH
O
N
.
|
R1
NH
H2L1 5
Ph
Thermal analysis of compounds I XIII (Table 2)
showed that their thermolysis involves three stages.
In the DTA curve of complex X in the range 70 90 C,
there is an endothermic peak which, as judged from
the relatively low temperature, corresponds to de-
hydration of the complex. At higher temperatures, one
more endothermic peak appears in the DTA curves of
compounds I V and VIII XIII (at 120 150 C for
R1 = NO2 (H2L1), H (H2L2), Cl (H2L3), Br (H2L4, H2L5);
R2 = H (H2L1, H2L3, H2L4), NO2 (H2L2), Br (H2L5).
It was experimentally shown that the reaction of
equimolar amounts of copper acetate and benzoyl-
hydrazones H2L1 5 in ethanol gives rise to compounds
1070-3632/03/7310-1611$25.00 2003 MAIK Nauka/Interperiodica

1612
SAMUS’ et al.
Table 1. Physicochemical characteristics of coordination compounds of copper(II) with benzoylhydrazones of substituted
salicylaldehydes
Found, %
Mb
Calculated, %
Mb
a
Comp. Yield,
,
app
Formula
no.
%
BM
Cl (Br)
N
Cl (Br)
N
I
II
82
89
65
62
76
73
72
75
67
86
79
89
81
1.41
1.49
1.59
1.58
1.65
1.52
1.64
1.57
1.58
1.54
1.61
1.52
1.60
17.05
17.21
17.65
16.24
13.09
14.94
15.74
14.57
14.66
14.52
14.66
13.77
11.62
11.68
11.79
6.67
7.25
5.64
C14H11CuN3O5
C14H11CuN3O5
17.43
17.43
17.95
15.95
13.31
15.24
15.92
14.93
14.93
14.67
14.81
13.83
11.80
11.43
11.43
7.91
7.03
5.87
III
IV
V
VI
VII
VIII
IX
X
10.25
19.84
33.26
27.56
8.62
C14H11ClCuN2O3
C14H11BrCuN2O3
C14H10Br2CuN2O3
C14H10BrClCuN2O2
C14H10ClCuN3O5
C19H14CuN4O4
10.00
20.05
33.48
27.68
8.90
6.95
6.72
10.81
13.46
13.18
9.99
7.89
9.42
10.53
13.16
13.16
9.70
9.79
9.14
C19H14CuN4O4
7.98
8.42
17.12
29.45
C19H16ClCuN3O3
C20H16ClCuN3O2
C19H14BrCuN3O2
C19H13Br2CuN3O2
8.20
8.27
17.39
29.68
XI
XII
XIII
8.09
7.80
a
b
At 293 H.
Metal.
Table 2. Results of thermal analysis of coordination compounds of copper (II) with benzoylhydrazones of substituted
salicylaldehydes
Number of
endothermic
peak in the
DTA curve
Weight loss
Kinetic parameters
Temperature
of complete
decomposition,
C
Comp.
no.
t,
C
found,
%
calculated,
%
species
lost
E *,
log Z
1
kJ mol
I
II
1
1
1
1
1
140
4.9
5.0
5.0
4.8
4.0
4.9
4.9
5.1
4.5
3.8
H2O
H2O
H2O
H2O
H2O
99
90
92
89
88
9.2
8.4
8.6
8.3
8.2
360
350
440
440
435
450
395
375
365
480
130
120
135
150
III
IV
V
VI
VII
VIII
IX
X
1
1
1
2
1
1
1
170
150
80
155
185
160
180
18.8
18.6
4.0
18.0
21.5
17.0
15.0
18.5
18.5
4.2
18.2
21.7
17.2
14.7
C5H5N
C5H5N
H2O
C5H5N
C6H7N
C5H5N
C5H5N
125
115
46
127
132
130
131
11.9
11.0
3.9
12.1
12.5
12.3
12.4
XI
XII
XIII
500
460
440
I V and at 150 180 C for VIII XIII). Judging from
the weight loss, it corresponds to deaquation or
deamination of these complexes. The ensuing heat
effect in the DTA curves of the compounds under
study observed in the range 350 500 C is exothermic
and corresponds is thermooxidative decomposition of
the coordinated hydrazones H2L1 5. It was found that
this peak maximum temperature depends on the nature
of the substituent in the benzene ring of the salicylal-
dehyde moiety of the azomethine, and at the same
composition of the complex varies in the following
order: Br 5-Cl 5-NO2 3-NO2. The temperature
of complete decomposition is also dependent on the
nature of the other inner-sphere ligands: It increases
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COORDINATION COMPOUNDS OF COPPER(II) WITH BENZOYLHYDRAZONES
on replacement of water by amines or of the nitrate
1613
log Z
ion by chloride.
XIII
X
XI
XII
VIII
Using the Horowits Metzger method [9] with
supplements made by Topor [10], we estimated the
kinetic parameters of dehydration, deaquation, and
deamination of compounds I V and VIII XIII
(Table 2). As follows from Table 2, the resulting ac-
tivation energies E* and preexponential factors Z are
close to the E* and Z values for the similar topo-
chemical processes described in [11 13]. As shown
experimentally (Table 2), the kinetic parameters are
primarily controlled by the nature of the leaving
ligand: In going from aqua- to pyridine- or picoline-
containing complexes the E* and log Z values increase,
in parallel with the increasing -donor and -acceptor
power of these ligands. The calculated kinetic param-
eters fit well with the compensation effect (see figure).
According to [13, 14], its presence indicates that,
regardless of the nature of the substituent in the
benzene ring of the salicylaldehyde moiety of the
hydrazone and the leaving ligand (water or amine),
the coordination compounds studied undergo the
same thermolysis reactions.
12
11
IX
10
I
9
8
III
IV
II
V
1
85
95
105
115
125 E, kJ mol
Compensation effect for the deaquation and deamination
reactions of complexes I V and VIII XIII.
sorption bands appear in the same regions as in the
free benzoylhydrazones. The presence in the obtained
compounds of coordinated molecules of water or
amines (pyridine or 3-picoline) is confirmed by the
observation in their IR spectra of the corresponding
absorption bands [I V: (H2O) 3600 3585, (H2O)
To determine the mode of coordination of the
ligands with the central ions, we performed a com-
parative analysis of the IR spectra of complexes I
XIII, starting hydrazones H2L1 5, and the coor-
dination compounds of transition metals with similar
Schiff bases, described in [15 17]. It was found
(Table 3) that azomethines H2L1 5 in the com-
pounds studied behave as tridentate O,N,O-ligands
and add to the complexing ion via the phenol and
amide oxygen atoms, as well as via the azomethine
nitrogen to form five- and six-membered metal rings.
This suggestion is supported by the presence in the
IR spectra of complexes I XIII of (C=O), (C=N),
1595 1585, and
(H2O) 925 920; VIII XIII:
(CC) + (CN) + (CCH) 1640 1635 and 1530 1525,
(CN) 1310 1305, (CCH) 1230 1225, (CCH) +
(CC) + (CNC) 1065 1055 and 1030 1025, (CCC)
+ (CNC) 740 735, and (CH) 830 825 cm ]. The
IR spectrum of complex VII contains all bands
1
characteristic inner-sphere monodentate nitrate ions
[ (A1) 1290, 2(A2) 1025, 3(A3) 720, 4(B1) 1480,
1
1
5(B1) 710, and 6(B2) 800 cm ].
EXPERIMENTAL
The IR spectra were registered on a Perkin Elmer-
337 spectrophotometer (suspensions in Vaseline and
fluorinated oils). The effective magnetic moments of
compounds I XIII were determined by the Gouy
method. The calculation of the molar magnetic sus-
ceptibility corrected for diamagnetism was carried out
basing on the theoretical magnetic susceptibilities of
organic compounds. The thermoanalytical curves of
complexes I XIII were obtained on a Paulik Paulik
Erdey derivatograph at 20 1000 C in air (reference
Al2O3, corundum crucible). The starting benzoylhyd-
razones [H2L1 5, mp, C: H2L1, 97; H2L2, 95; H2L3,
130; H2L4, 135; H2L5, 141] were obtained by the
procedures described in [19].
1
and (C O) bands shifted by 50 15 cm to the long-
wave region relative to the corresponding absorption
bands of the starting hydrazones and similar Schiff
bases, as well as by the appearance of a series of new
1
bands in the range 530 340 cm due to absorption of
metal nitrogen and metal oxygen bonds. It should be
noted that in all the complexes, except for VI and VII,
the amide oxygen atom of hydrazones H2L1 5 is pre-
sent in the deprotonated enol form. It follows from
the lack in the IR spectra of these compounds of the
1
(C=H) band at 1650 1645 cm , as well as the
appearance of a new band (>C=N N=C<) in the
1
region of 1570 1565 cm . Furthermore, the spectra
of all the complexes, a new band appears at 703
1
725 cm , which, according to [3, 18], is indicative of
Di( -O)di[[N-(5-nitro-2-oxy-1-benzylidene)-N - -
oxybenzylidenehydrazine]aquacopper] (I). A solu-
tion of 10 mmol of 5-nitrosalicylaldehyde benzoyl-
hydrazone in 50 ml of ethanol was mixed with
bridging bonds. The other functional groups of ligands
H2L1 5 are definitely not involved in coordination
with the copper(II) ion, since their characteristic ab-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 10 2003

1614
SAMUS’ et al.
1
Table 3. IR spectra ( , cm ) of coordination compounds of copper with benzoylhydrazones of substituted salicylaldehydes
O
O
(M
M)b
Comp.
no.a
H2L1 3275 3210 1648
1630
1630
1630
1628
1628
1586
1588
1585
1586
1587
1585
1590
1587
1588
1586
1586
1585
1585
1520, 1276 970
1518, 1280 972
1520, 1280 970
1520, 1276 970
1520, 1276 970
1510, 1295 982
1506, 1290 980
1508, 1297 980
1509, 1295 980
1506, 1295 981
1506, 1295 983
1505, 1280 985
1506, 1285 985
1510, 1295 984
1508, 1295 980
1506, 1290 980
1505, 1292 983
1505, 1291 982
H2L2 3272 3212 1645
H2L3 3270 3210 1646
H2L4 3276 3208 1646
H2L5 3278 3208 1645
I
1570
1568
1568
1565
1567
725
727
725
725
730
728
730
730
727
725
728
727
727
448
445
445
447
446
445
440
440
442
447
445
448
448
340
340
342
340
343
343
345
345
340
340
342
344
345
510, 420
512, 425
515, 415
514, 417
520, 420
517, 415
525, 420
530, 422
515, 425
520, 415
520, 425
525, 418
520, 430
II
III
IV
V
VI
3278 3216 1608
3276 3215 1610
VII
VIII
IX
1565
1565
1566
1565
1570
1568
X
XI
XII
XIII
a
b
The complexes were heated at 105 C to constant weight.
M is metal.
10 mmol of Cu2(CH3COO)4 2H2O. The reaction
mixture was heated at 45 50 C with stirring for 30
40 min. After cooling, a dark green precipitate formed
and was filtered off on a glass filter, washed with
small amounts of ethanol and ether, and dried in air.
Complexes VIII XIII were obtained from the
above starting compounds in the presence of pyridine
or 3-picoline (pH 8). The yields and some physico-
chemical constants of the resulting compounds are
given in Tables 1 3.
Complexes II VII were obtained in a similar way
from benzoylhydrazones of H2L1 5 and copper acetate,
chloride, or nitrate hydrates.
The above physicochemical data allow the bond
distribution in complexes I XIII to be presented by
schemes B (I V, VIII XIII) and C (VI, VII).
R1
Cl
Z
A
N
N
R2
O
Cu
Ph
O
Cu
Ph
O
O
nH2O
O
O
Ph
R2
Cu
O
Ph
Cu
O
N
N
Z
A
R1
Cl
B
C
A = H2O (I V), C5H5N (VIII X, XII, XIII), 3-CH3C5H4N (XI); R1 = H (II, IX), Cl (III, X, XI), Br (IV, V, XII, XIII);
R2 = H (I, III V, VIII, X XIII), Br (V, XIII); n = 0 (I V, VIII, IX, XI XIII), 1 (X); Z = Br (VI), NO3 (VII).
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COORDINATION COMPOUNDS OF COPPER(II) WITH BENZOYLHYDRAZONES
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