Coordination compounds of copper(II) with new 1,4-benzothiazino-[2,3-b]phenothiazine derivatives

Article abstract of DOI:10.1081/SIM-120013142

New coordination compounds of copper(II) with 1,4-benzothiazino[2,3-b]phenothiazine derivatives (L) of the molecular formulas [Cu(L)^·+Cl₃^-] were synthesized and characterized by spectral (IR, UV-Vis, ESR) and thermal analy

Full text of DOI:10.1081/SIM-120013142

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COORDINATION COMPOUNDS OF COPPER(II) WITH
NEW 1,4-BENZOTHIAZINO[2,3-b] PHENOTHIAZINE
DERIVATIVES
Letiţia Ghizdavu a , Castelia Cristea b , I. A. Silberg a , Craˇiţa Baˇlan c & L. David c
a Department of Chemistry, “Babes-Bolyai” University, 3400 Cluj-Napoca, Romania
b Department of Chemistry, “Babes-Bolyai” University, 3400 Cluj-Napoca, Romania
c Department of Physics, “Babes-Bolyai” University, 3400 Cluj-Napoca, Romania
Version of record first published: 15 Feb 2007.
To cite this article: Letiţia Ghizdavu , Castelia Cristea , I. A. Silberg , Craˇiţa Baˇlan & L. David (2002): COORDINATION
COMPOUNDS OF COPPER(II) WITH NEW 1,4-BENZOTHIAZINO[2,3-b] PHENOTHIAZINE DERIVATIVES, Synthesis and Reactivity
in Inorganic and Metal-Organic Chemistry, 32:1, 1-7
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SYNTH. REACT. INORG. MET.-ORG. CHEM., 32(1), 1–7 (2002)
COORDINATION COMPOUNDS OF
COPPER(II) WITH NEW
1,4-BENZOTHIAZINO-
[2,3-b]PHENOTHIAZINE DERIVATIVES
Letit¸
ia Ghizdavu,1 Castelia Cristea,1,* I. A. Silberg,1
Crait
a Balan,2 and L. David2
¸
1Department of Chemistry and
2Department of Physics, ‘‘Babes-Bolyai’’ University,
3400 Cluj-Napoca, Romania
ABSTRACT
New coordination compounds of copper(II) with 1,4-ben-
zothiazino[2,3-b]phenothiazine derivatives (L) of the molecular
formulas [CuðLÞꢀþCl3À] were synthesized and characterized by
spectral (IR, UV-Vis, ESR) and thermal analysis methods.
INTRODUCTION
The primary interaction product of phenothiazine with CuCl2
was reported as the phenothiazinyl tetrachlorocuprate(II) salt1. Various
biologically active N(-alkylphenothiazines generated mononuclear cop-
per(II) complexes2. Other metals like cadmium(II), zinc(II), paladium(II)
were also coordinated by phenothiazine derivatives.
*Corresponding author. E-mail: castelia@chem.ubbcluj.ro
1
Copyright # 2002 by Marcel Dekker, Inc.
www.dekker.com

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GHIZDAVU ET AL.
We report here the coordination of copper(II) with new phenothiazine
derivatives, namely 1,4-benzothiazino[2,3-b]phenothiazine (L1), 12H,-
14H-3,9-dimethyl-5,7-dithia-12,14-diazapentacene (L2) and 16H,18H-di-
benzo[c,l]-7,9-dithia-16,18-diazapentacene (L3).
The structural formulas of these organic heterocyclic compounds are
presented in Fig. 1; we have obtained and characterized them as previously
reported374
.
EXPERIMENTAL
Thermal analyses were performed with an OD-103M.O.M. Deriva-
tograph using a sample weight of 100 Æ 1À2 mg, at a heating rate of
ꢁ
10 C=min, with Al2O3 as reference material in static air atmosphere. The
infrared spectra were recorded in KBr pellets with an FTIR JASCO 600
spectrometer and UV-Vis spectra were recorded with an UV-VIS Specord
spectrophotometer. EPR spectra were recorded at 9.4 GHz (X band), using
standard JEOL-JES-3B equipment.
General Procedure for the Preparation of Complexes
[CuðLÞꢀþClÀ3 Š ðL ¼ L1; L2; L3Þ
A quantity of 1.7 g CuCl2Á2H2O (0.01 mole) disolved in 2.5 mL water
and 5 mL acetone was added with stirring to a clear solution of the ligand,
obtained by dissolving 0.001 mol of ligand in 5 mL DMF and 10 mL
acetone. After 10 minutes of stirring at room temperature the resulting dark
precipitate was filtered, washed with acetone and dried in air. The yields and
the melting points of the complexes are presented in Table I.
Figure 1. Structural formulas of 1,4-benzothiazino[2,3-b]phenothiazine.

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COORDINATION COMPOUNDS OF COPPER(II)
3
Table I. Characterization Data of the Complexes [CuðLÞꢀþCl3]
Elemental Analysis Found
(Calcd.) [%]
Molecular Formula
Empirical Formula
Weight
Yield, % Decomp. [ꢁC]
C
H
N
Cl
[CuðL1ÞꢀþClÀ3 ]
C18H10Cl3CuN2S2
488
62.5
67.7
57.7
175
167
162
44.2
(44.17) (2.45) (5.72) (21.57)
2.5
5.6
21.7
[CuðL2ÞꢀþClÀ3 ]
C20H16Cl3CuN2S2
518
46.2
3.1
5.3
(46.42) (3.09) (5.42) (20.41)
20.5
½CuðL3ÞꢀþClÀ3 ]
C26H16Cl3CuN2S2
590
52.3
(52.89) (2.73) (4.74) (18.01)
2.8
4.6
18.2
RESULTS AND DISCUSSION
The reaction of excess copper(II) chloride with phenothiazine deriva-
tive ligands L ¼ L1, L2, or L3, in acetone/water solution at room tempera-
ture generated dark, microcrystalline, powdery complexes, which are higꢁhly
insoluble and which are characterized by high melting points (above 300 C,
with decomposition). The reaction equation is the following:
L þ 2CuCl2 ! ½CuðLÞꢀþCl3ÀŠ þ CuCl
where L ¼ L1; L2; or L3
The good electron donor phenothiazine derivatives L were easily oxi-
dized by Cu(II) to the corresponding substituted phenothiazine radical ca-
tions Lꢀþ. The initial 2þ oxidation state of the metal appears unchanged in
the resulting complex salts. The structure of the complex salts [CuðLÞꢀþCl3À]
is supported by thermal analysis, UV-Vis, IR and ESR spectroscopic data.
Thermal Analysis of the Metal Complexes
The thermal decomposition of the compounds was studied by means
of derivatography in air atmosphere. TG and DTA data are presented in
1
2
3
ꢁ
Table II. The ligands L , L , and L are very stable up to ꢂ 300 C (melting
ꢁ
ꢁ
ꢁ
points: 293 C; 257 C; 290 C), in contrast to the lowered thermal stabi-
lity of the synthesized Cu(II) complexes.
The decomposition of the complexes occurs in the 1627175 ꢁC tem-
perature range, when two chlorine atoms separate from each molecule. The

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GHIZDAVU ET AL.
Table II. Thermal Data of the Synthesized Copper(II) Complexes
DTA peak
[ꢁC]
TG Data%
Temp.
range [ꢁC] Endo Exo Calcd. Exp.
Assignment
[CuðL1ÞꢀþClÀ3 ]
[CuðL2ÞꢀþClÀ3 ]
[CuðL3ÞꢀþClÀ3 ]
207180
1807267
2677700
70071000
175
192
7
7
7
14.45 15.10 2 Cl
7.2327.31 Cl
395 62.09 61.50 pyrolysis of organic rest
7
775
16.22 16.08 CuO residue
207170
1707200
2007700
70071000
167
178
7
7
7
13.78 13.52 2 Cl
6.84
6.98 1 Cl
410 64.14 63.38 pyrolysis of organic rest
7
775
15.34 16.12 CuO residue
207170
1707200
2007700
70071000
162
171
7
7
7
11.04 11.46 2 Cl
5.58 1 Cl
5.52
415 71.06 70.01 pyrolysis of organic rest
12.38 12.85 CuO residue
775
7
loss of the third chlorine atom takes place between 1717192 ꢁC. This Cu-Cl
bond is stable up to a higher temperature due to the hydrogen bond created
(Fig. 2). For the threeꢁstudied complexes, the thermal decomposition of the
ligands starts at 200 C, indicating the destabilization of the heterocylic
ligand due to the weakening of the C-S bond, as a consequence of Cu-S
bond formation in the complexꢁes. An exothermic peak marks the pyrolysis
of the organic residue at ꢂ 400 C. In the 2007700 ꢁC temperature range the
formation of CuSO4 is observed, followed by the thermal decomposition
ꢁ
CuSO4 ! CuO þ SO3 at 775 C.
The thermal analysis results of the three investigated compounds
confirm the atom ratio Cu:L:Cl ¼ 1:1:3.
Electronic Spectra
The UV(-Vis spectrum of each of the three organic heterocyclic ligands
contains only one absorption band in the UV region at about 300 nm
(Table III). The bathochromic shift of about 25 nm for the dibenzo-deri-
vative L3 was assigned to the additional conjugation with the two adjacent
benzene rings.
The interaction of L (known as good electron donors) with either organic
electron acceptors [e.g. tetracyanoethylene (TCNE) or tetracyanoquino-

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5
Figure 2. Proposed structure of the [CuðLÞꢀþCl3À] complex salts.
dimethane (TCNQ)] or concentrated sulfuric acid (when preparing solutions of
L in this medium) determined the formation of substituted phenothiazine ra-
dical cations, Lꢀþ, characterized in the UV-Vis spectrum by an absorption band
in the 300 nm region-due to the allowed intraligand p ! pà transitions- and an
additional band in the 700 nm region; the latter low-intensity band was assigned
to the n ! pà transition due to the ligand radical cation5.
Each of the [CuðLÞꢀþCl3À] solutions displayed in the UV-Vis spectrum
three absorption bands in the 300, 600 and 700 nm regions. The absorption
band near 600 nm may be assigned to the d ! d transition due to the axial
coordination of sulfur atoms (from the ligand) to copper(II)6.
IR Spectra
The stretching vibrations of the NH groups in the 335073480 cmÀ1
region, accompanied by a deformation vibration at about 1310 cmÀ1
Table III. Electronic Spectral Data (nm) of the Ligands and Their Copper(II)
Complexes in N,N0-Dimethylformamide Solution
Compound
l (nm) (e)
L1
290 (8000)
292 (8500)
295 (8600)
298 (8500)
320 (9600)
325 (10000)
[CuðL1ÞꢀþClÀ3 ]
605 (800)
607 (800)
615 (850)
695 (1200)
700 (1000)
745 (1500)
L2
[CuðL2ÞꢀþClÀ3 ]
L3
[CuðL3ÞꢀþClÀ3 ]

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GHIZDAVU ET AL.
Table IV. NH Groups Vibration Bands (cmÀ1) of the
Ligands and Their Corresponding Copper(II) Complexes
nðNHÞ
dðNHÞ
L1
3480 w; 3419 w
3441 w; 3357 w
3460 w; 3390 w
3445 w; 3330 w
3375 w; 3360 w
3334 w
1310 m
1321 m
1310 m
1346 m
1310 m
1320 m
[CuðL1ÞꢀþClÀ3 ]
L2
[CuðL2ÞꢀþClÀ3 ]
L3
[CuðL3ÞꢀþClÀ3 ]
(Table IV), of the heterocyclic compounds L1, L2, L3 are also present in
the corresponding [CuðLÞꢀþCl3À] complexes. From the IR data it can be
seen that the hydrogen bonding associations in the complexes have resulted
in a shift of the NH stretching vibration bands towards lower wave
numbers.
ESR Spectral Data
Powder ESR spectra of [CuðL1ÞꢀþCl3À] and [CuðL2ÞꢀþClÀ3 ] are quasi-
isotropic. The values of ESR parameters (g0 ¼ 2:051; A0 ¼ 17 G and
g0 ¼ 2:048; A0 ¼ 16 G for [CuðL1ÞꢀþCl3À] and [CuðL2ÞꢀþClÀ3 ], respectively)
are typical for monomeric species with a compressed tetrahedral stereo-
chemistry around the copper(II) ions. The paramagnetic electron is in a
dx2Ày2 ground state orbital.
The powder ESR spectrum of the [CuðL3ÞꢀþCl3À] complex is typical for
axial monomeric species with a rhombic distortion (g1 ¼ 2:187; g2 ¼
2:083; g3 ¼ 2:014). The value of the lowest g factor indicates that the
z
paramagnetic electron is in a dz orbital as ground state.
The neutral phenothiazinyl radical L13 is characterized by a g value of
2.0052, typical for an aminyl radical4.
Conclusions
On the basis of all of these analytical data we propose for the new
copper(II) complex salts a structure containing an axial coordination of a
sulfur atom from the ligand to the tetrahedral Cu(II) ion situated under the
N,S bridge of the bent phenothiazine radical cation part of the ligand

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7
structure and a hydrogen bond linking a chlorine atom with the spatially
neighboring NH group (Fig. 2).
REFERENCES
1. Diudea, M.; Silberg, I.A. Phenothiazinyl- and Diphenothiazine-Copper
Complexes as Intermediates and Products in the Interaction of Phe-
nothiazines with Copper(II) Halides. J. Prakt. Chem. 1982, 324 (5),
7697776.
2. Gowda, N.M.M.; Kim, D.-H.; Raju, B.; Sherigara, B.S. Coordination
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Synthesis and Characterization. Synth. React. Inorg. Met.-Org. Chem.
1996, 26 (8), 142171435.
3. Silberg, I.A.; Cristea, C. Free Radicals of Phenothiazine and Related
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zothiazino[2,3-b]phenothiazine and its Substituted Derivatives. Het-
erocycl. Commun. 1999, 5 (2), 1477150.
5. Cristea, C.; Silberg, I.A. Cation Radical Salts of 1,4-Benzothiazino-[2,3-
b]-phenothiazine. Studia Univ. Babes-Bolyai Chem. 1997, 42 (172),
1117115.
6. Kumagay, M.; Sakamoto, M.; Tsuchija, K.’ Sakujama, H.; Nishida, Y.
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106571077.
Received April 8, 2000
Accepted September 18, 2001
Referee I: S. Mathur
Referee II: M. Veith

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