Synthesis and study of copper(II), nickel(II), and cobalt(II) complex compounds with dihydrobenzoxazine derivatives

Article abstract of DOI:10.1134/S1070363206040244

Complex compounds ML₂ of copper(II), nickel(II), and cobalt(II) with 2-(2-hydroxy-5-nitrophenyl)-4,4-diphenyl-1,4-dihydro-2H-3,1-benzoxazine and 2-(2-hydroxyphenyl)-4,4-diphenyl-1,4-dihydro-2H-3,1-benzoxazine (HL) were prepared by electrochemical and chemical syntheses. The complex formation involves the azomethine form of the ligand and gives a six-membered chelate cycle comprising deprotonated phenol and azomethine groups. The coordination entity has a planar structure with trans arrangement of the nitrogen and oxygen atoms. Pleiades Publishing, Inc., 2006.

Full text of DOI:10.1134/S1070363206040244

ISSN 1070-3632, Russian Journal of General Chemistry, 2006, Vol. 76, No. 4, pp. 641 644.
Pleiades Publishing, Inc., 2006.
Original Russian Text T.E. Apenysheva, K.S. Pushkareva, S.N. Bolotin, V.Yu. Frolov, F.A. Kolokolov, E.V. Gromachevskaya, A.A. Borodavko,
T.P. Kosulina, 2006, published in Zhurnal Obshchei Khimii, 2006, Vol. 76, No. 4, pp. 675 679.
Synthesis and Study of Copper(II), Nickel(II), and Cobalt(II)
Complex Compounds with Dihydrobenzoxazine Derivatives
T. E. Apenysheva*, K. S. Pushkareva*, S. N. Bolotin*, V. Yu. Frolov*,
F. A. Kolokolov*, E. V. Gromachevskaya**, A. A. Borodavko**, and T. P. Kosulina**
* Kuban State University, ul. Stavropol’skaya 149, Krasnodar, 350040 Russia
e-mail: fed_1@mail.ru
** Kuban State Technological University, Krasnodar, Russia
Received December 21, 2004
Abstract Complex compounds ML2 of copper(II), nickel(II), and cobalt(II) with 2-(2-hydroxy-5-nitro-
phenyl)-4,4-diphenyl-1,4-dihydro-2H-3,1-benzoxazine and 2-(2-hydroxyphenyl)-4,4-diphenyl-1,4-dihydro-
2H-3,1-benzoxazine (HL) were prepared by electrochemical and chemical syntheses. The complex formation
involves the azomethine form of the ligand and gives a six-membered chelate cycle comprising deprotonated
phenol and azomethine groups. The coordination entity has a planar structure with trans arrangement of the
nitrogen and oxygen atoms.
DOI: 10.1134/S1070363206040244
1,4-Dihydro-2H-3,1-benzoxazines are original
chemical systems whose peculiar reactivity and struc-
ture result from the annelation of the 1,3-oxazine and
benzene rings [1]. Dihydrobenzoxazines bearing no
substituents in the 4 position can undergo tautomeric
transformation into a linear azomethine form (Schiff
bases) [2 4]. This tendency is the most clearly pro-
nounced in compounds with the alternative unsatur-
ated structure stabilized by an intramolecular hydro-
gen bond [5].
The purpose of the present work was to prepare
solid Co(II), Ni(II), and Cu(II) complexes with 1,4-di-
hydro-2H-3,1-benzoxazines and to study their com-
position and structure. As ligands we used 2-(2-hyd-
roxy-5-nitrophenyl)-4,4-diphenyl-1,4-dihydro-2H-3,1-
benzoxazine (HL1) and 2-(2-hydroxyphenyl)-4,4-di-
phenyl-1,4-dihydro-2H-3,1-benzoxazine (HL2), which
we synthesized previously [1].
According to the elemental analysis, the complex
formation yields compounds I VI of the ML12 and
ML22 types. Their physicochemical characteristics are
given in Table 1. The solvent and acetic acid formed
in the reaction do not enter into the compounds,
which is also proved by the IR spectra and points to
the fact that all possible coordination sites of the
metal ion are occupied by donor groups of the ligand.
2H-3,1-Benzoxazines and their 1,2-dihydro deriva-
tives in the form of free bases and salts have been
offered as herbicides and plant growth regulators
[6, 7]. These compounds combine low toxicity with
pharmacologic activity [8]. They can be used as
tranquilizers, analgetics, antispasmodics and exhibit
sedative, hypnosedative, and anticonvulsant effects
[9].
The dihydrobenzoxazines HL1 and HL2 can exist
in two tautomeric forms A and B [2, 3].
It is known [10] that complexes of transition metals
with biologically active ligands possess a higher
biological activity and lower toxicity that the starting
ligands. Therefore, synthesis and isolation of com-
plexes of 3d elements with benzoxazine derivatives is
a perspective area of coordination chemistry. 1,4-Di-
hydro-2H-3,1-benzoxazines with a 2-hydroxyphenyl
substituent are potentially tridentate ligands capable
of complex formation with transition metals. Com-
plexes of such ligands with d elements have not been
studied before.
Ph
Ph
OH
Ph
Ph
O
X
N
H
O
N
H
OH
X
A
B
X = NO2 (HL1), H (HL2).
641

642
APENYSHEVA et al.
Table 1. Yields, decomposition temperatures, and elemental analyses of complexes I VI
Found, %
Calculated, %
Comp.
no.
Yield,
%
Td,
C
M
L
Color
Formula
C
H
N
M
C
H
N
M
I
II
III
IV
V
Cu L1
Ni L1
Co L1
Cu L2
Ni L2
Co L2
53
58
63
45
51
48
182a Dark green 68.52 4.19 6.17 6.75 C52H38CuN4O8 68.60 4.21 6.15 6.98
>230
Orange
68.88 4.21 6.21 6.05 C52H38N4NiO8 68.97 4.23 6.19 6.48
>220
Dark red 68.90 4.21 6.20 6.28 C52H38CoN4O8 68.95 4.23 6.19 6.51
195a Dark green 76.11 4.89 3.43 7.48 C52H40CuN2O4 76.09 4.91 3.41 7.75
>240
>230
Light green 76.49 4.92 3.46 7.03 C52H40N2NiO4 76.58 4.94 3.43 7.20
Dark red 76.58 4.92 3.46 7.09 C52H40CoN2O4 76.56 4.94 3.43 7.22
VI
a
Melting point.
Table 2. IR spectra of ligands HL1 and HL2 and their complexes I VI
1
Compound
HL1
IR spectrum, cm
3314 [ (NH)], 3330 w [ (OH)], 1616 [ (C=N)], 1522 [ as(NO2)], 1336 [ ((NO2)], 1285 [ (COphenol)], 1071
s
[ (COcycl)]
HL2
3329 [ (NH)], 3350 w [ (OH)], 1624 [ (C=N)], 1250 [ (COphenol)], 1065 [ (COcycl)]
I
3530 w [ (OH)], 1543 [ (C=N)], 1540 [ as(NO2)], 1329 1280 [ ((NO2)], 1329 1280 [ (COphenol)], 1035
s
[ (COalcohol)], 569 m [ (M O)], 459 m [ (M N)]
II
3500 w [ (OH)], 1547 [ (C=N)], 1541 [ as(NO2)], 1326 1279 [ ((NO2)], 1326 1279 [ (COphenol)], 1045
s
[ (COalcohol)], 568 m [ (M O)], 461 m [ (M N)]
III
3480 w [ (OH)], 1548 [ (C=N)], 1540 [ as(NO2)], 1333 1277 [ ((NO2)], 1333 1277 [ (COphenol)], 1045
s
[ (COalcohol)], 567 m [ (M O)], 461 m [ (M N)]
IV
V
VI
3500 w [ (OH)], 1534 [ (C=N)], 1310 [ (COphenol)], 1015 [ (COalcohol)], 594 m [ (M O)], 456 m [ (M N)]
3480 w [ (OH)], 1544 [ (C=N)], 1297 [ (COphenol)], 1009 [ (COalcohol)], 597 m [ (M O)], 453 m [ (M N)]
3455 w [ (OH)], 1528 [ (C=N)], 1310 [ (COphenol)], 1005 [ (COalcohol)], 601 m [ (M O)], 453 m [ (M N)]
The IR spectra of solid HL1 and HL2 show N H
increase of the NO2 antisymmetric stretching vibration
frequency is also connected with the formation of the
coordination entity and with attenuation of the con-
jugation of the nitro group with the benzene ring.
stretching vibration bands at 3314 (HL1) and
1
3329 cm (HL2) (Table 2). Its presence provides
evidence to show that the ligands exist in the solid
state in the form of structure A.
The change in the stretching vibration frequency
of the C O bond in the C O C fragment of the benz-
oxazine ring is caused by ring opening and appearance
of the triphenylcarbinol group. The IR spectrum gives
no evidence to show whether this group takes part in
coordination. The involvement of the phenol oxygen
atom in coordination is proved by the presence of an
The N H stretching vibration band is absent from
the IR spectra of the complexes (Table 2). The O H
stretching vibration frequency increases to 3530
1
3450 cm , which is attributable to the appearance of
the triphenylcarbinol OH bond and the absence of the
phenol O-H bond. The reason for this phenomenon is
that the complex formation involves the azomethine
form of the ligand (structure B), which is confirmed
by the appearance of a strong C=N stretching vibra-
tion band in the region of 1620 1590 cm in the
spectra of the complexes.
1
absorption band in the region of 600 560 cm in the
IR spectra of compounds I VI. According to [11], we
assigned this band to M O stretching vibrations.
1
1
The absorption band in the region of 470 450 cm ,
which is absent from the spectra of the ligands, is
assignable to stretching vibrations of the M N bond.
Thus, we can suggest that the nitrogen atom takes part
in binding with the metal ion.
Stretching vibrations of the C Ophenol bond in the
complexes have a higher frequency than in the starting
ligands and superimpose on symmetrical stretching
vibrations of the nitro group [11], implying binding of
the phenol oxygen atom with the metal ion. The
The ESR spectra of powdered compounds I and IV
(Fig. 1a), measured at room temperature, point to an
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SYNTHESIS AND STUDY OF COPPER(II), NICKEL(II), AND COBALT(II)
643
(a)
axial symmetry of the nearest surrounding of the
metal ion with the unpaired electron localized on the
2
y2
dx
orbital. According to [12, 13], the spin-
Hamiltonian parameters [compound I: g 2.0835
0.0002 and g|| 2.223 0.002; compound IV: g
2.0811 0.0002 and g|| 2.221 0.002] point to the
presence of two nitrogen and two oxygen atoms in
the equatorial plane of the complex. The g|| value of
2.22 is characteristic of trans-N2O2 surrounding of
the copper(II) ion [12] and points to trans arrangement
of the phenol and azomethine groups.
0.26
0.28
0.30
0.32
0.34
H, Tl
(b)
The ESR spectrum of compound IV in chloroform
(Fig. 1b) shows a copper hyperfine structure and, on
the upfield component of this hyperfine structure, an
additional hyperfine structure from 14N nuclei (I 1)
(Fig. 1c). The fact that the three well-defined com-
ponents of the additional hyperfine structure (A 1.44
3
1
10 cm ) have different intensities suggests that the
unpaired electron of copper(II) is coupled with two
paramagnetic nuclei of the ligands [14, 15]. In this
case, the intensity ratio of all the five components is
1:2:3:2:1, the extreme components being weak.
Were a single nitrogen atom present, the bands would
have equal intensities. The absence of the additional
nitrogen hyperfine splitting from the ESR spectrum of
compound I cannot be considered evidence for the
absence of Cu N coupling [16], and the closeness of
the g-factors and hyperfine coupling constants for
0.29
0.30
0.31
0.32
0.33
H, Tl
(c)
1
compounds I and IV [I: giso 2.1294, A 7.19 10 3 cm ;
3
1
and IV: giso 2.1264, A 7.19 10 cm ] suggests
analogous coordination modes in these two com-
pounds. The isotropic factors (giso) satisfy the rule
giso = (g|| + 2g )/3, implying that the structure of the
coordination entity is preserved on solution. Whether
alcohol groups coordinate with the copper(II) ion in
the axial position cannot be either confirmed or denied
on the basis of the ESR spectra.
0.322 0.324 0.326 0.328 0.330 0.332
H, Tl
ESR soectra (298 K) of compound IV in (a) powder and
(b) chloroform, and (c) the upfield component of the
hyperfine structure in the latter spectrum.
Thus, in our opinion, the following structure is the
most probable for the copper(II) complexes.
In the electrochemical synthesis, anodic dissolution
at specified electrode potentials results in the follow-
ing electrode processes.
Ph
Ph
OH
X
Cathode: 2H+ + 2e
Anode: 2L + M
H2 (HL + ne
2e
L + n/2H2),
ML2,
O
N
_
_
2+|
|
_| Cu
HL = HL1, HL2; M = Cu, Ni.
_
|
O
N
HO
According to the IR and ESR spectra, the com-
plexes obtained by the electrochemical method are
completely identical to compounds I, II, and IV
described above. The advantages of this method are
high yields (80 90%) of the reaction products and the
possibility of controlling kinetic parameters of the
process. Unlike the chemical synthesis, this method
does not involve the stage of crystal maturing.
X
Ph
Ph
X = NO2 (I), H (IV).
According to the IR spectra, the phenol and azo-
methine groups are also involved in coordination in
the nickel(II) and cobalt(II) compounds.
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644
APENYSHEVA et al.
EXPERIMENTAL
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