Synthesis and thermal properties of 4,4′-bipyridine adducts of Mn(II), Co(II), Ni(II) and Cu(II) monochloroacetate

Article abstract of DOI:10.1023/A:1010188325149

The complexes with the empirical formula M(4-bipy)(ClCH₂COO)₂·nH₂O (where: 4-bipy = 4,4′-bipyridine, L = ClCH₂COO^-, M(II) = Mn, Co, Ni, Cu) were prepared and characterized via the IR and electronic (V

Full text of DOI:10.1023/A:1010188325149

Journal of Thermal Analysis and Calorimetry, Vol. 63 (2001) 387–395
SYNTHESIS AND THERMAL PROPERTIES OF
4,4’-BIPYRIDINE ADDUCTS OF Mn(II), Co(II), Ni(II)
AND Cu(II) MONOCHLOROACETATE
D. Czakis-Sulikowska, A. Czylkowska and J. Radwañska-Doczekalska
Institute of General and Ecological Chemistry, Technical University, 90-924 £ód¿, Poland
(Received March 28, 2000; in revised form June 28, 2000)
Abstract
The complexes with the empirical formula M(4-bipy)(ClCH2COO)2×nH2O (where: 4-bipy=4,4’-bi-
pyridine, L=ClCH2COO–, M(II)=Mn, Co, Ni, Cu) were prepared and characterized via the IR and
electronic (VIS) spectra and conductivity measurements. Thermal decomposition of these com-
pounds was studied. During heating in air dehydration processes occur. The anhydrous compounds
decompose at high temperature to oxides. The principal volatile mass fragments correspond to: H2O,
CO2, CH3Cl, HCl, Cl2 and other.
Keywords: 4,4’-bipyridine complexes, mass spectrometry, monochloroacetate, thermal decompo-
sition, VIS-IR spectra
Introduction
Whereas the metal(II) compounds of halogenoacetate acid and its mixed complexes
containing organic ligands were described by many authors [1–15], the thermal prop-
erties of these complexes have not been extensively studied so far. The thermal de-
composition of some copper(II) halogenoacetates was carried out by Obier et al. [16]
and described in other papers [17, 18]. The first decomposition products of the
Cu(ClCH2COO)2 detected (MS) were: CO2, H2O, HCl, CH3Cl and ClCH2COOH [18].
Thermal properties of zinc(II) monochloroacetate and its complexes with nicotin-
amide and coffeine were reported by Zeleòák et al. [19].
In paper, we describe the synthesis of new mixed ligand complexes of Mn(II),
Co(II), Ni(II) and Cu(II) with 4,4’-bipyridine and monochloroacetic acid. The com-
pounds obtained were characterized by elemental analysis, and by IR-VIS spectro-
scopic and molar conductivity investigations. The thermal decomposition was stud-
ied in air. A coupled TG-MS system was used to analyse the principal gaseous prod-
ucts involved during pyrolysis of the synthesized complexes.
1418–2874/2001/ $ 5.00
Akadémiai Kiadó, Budapest
© 2001 Akadémiai Kiadó, Budapest
Kluwer Academic Publishers, Dordrecht

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CZAKIS-SULIKOWSKA et al.: 4,4’-BIPYRIDINE ADDUCTS
Experimental
Materials and analyses
4,4’-Bipyridine (m.p. 69.9oC), ClCH2COOH p.a. were obtained from Aldrich; metha-
nol (anhydroscan) from Lab-Scan; hydroxyloamine 50% v/v from Fluka; other chem-
icals were p.a. products from POCh-Gliwice. Solutions of M(ClCH2COO)2 were pre-
pared by adding 20 ml 2M ClCH2COOH to freshly precipitated carbonates of the
metal(II) in ca. equimolar ratio. The contents of M(II) ions in obtained solutions were
complexometrically determined.
Syntheses of the complexes
A solution of 4-bipy (12.8 mmol) in 96% v/v EtOH (31.3 ml) was added to a solution of
M(ClCH2COO)2 (4.3 mmol) in water (8.75 ml). During synthesis of manganese(II) com-
plex these mixture containing 1 ml of 10% v/v hydroxyloamine (to stop the oxidation
process of Mn(II)). The product was collected, washed with 40% v/v EtOH and then with
EtOH-Et2O (1:1) mixture and dried in open air. The dried complexes were analysed: C,
N, H – by elementary analysis with V2O5 as oxidizing agent; Mn(II), Cu(II), Co(II) and
Ni(II) in mineralized samples were complexometrically determined. The analytical re-
sults for obtained complexes are shown in Table 1, together with other characteristic data.
Table 1 Analytical data, solubility S (mol dm–3) in water at 21°C and molar conductivity ΛM
(Ω–1 cm2 mol–1) in methanol (concentration 1·10–3 mol dm–3) at 25°C of the complexes,
where L=ClCH2COO–
Analysis: found (calculated)/%
Complex
(colour)
S·103
ΛM
M
C
N
H
Mn(4-bipy)L2·H2O
(white)
13.69
40.83
7.14
3.70
26.9
68.2
(13.20)
13.52
(40.41)
38.06
(6.73)
6.69
(3.39)
3.51
Co(4-bipy)L2·2H2O
(light-rose)
15.2
7.6
24.2
64.6
40.7
(13.45)
12.90
(38.38)
35.90
(6.39)
6.60
(3.68)
4.38
Ni(4-bipy)L2·4H2O
(green)
(12.38)
14.50
(35.48)
35.48
(5.91)
6.60
(4.25)
4.45
Cu(4-bipy)L2·4H2O
(blue)
2.2
(13.27)
(35.12)
(5.85)
(4.21)
Physical measurements
The thermal decomposition processes of the prepared complexes were studied by
thermogravimetry (TG, DTG, DTA) and TG/MS techniques. Samples were heated
from 25 up to 1000°C with a heating rate of 10°C min–1 in air atmosphere. TG, DTG
and DTA curves were recorded by using a derivatograph Q-1500, with the sample
mass of 100 mg and α-Al2O3 as reference material. Mass spectrometer was used for
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CZAKIS-SULIKOWSKA et al.: 4,4’-BIPYRIDINE ADDUCTS
389
the characterization of volatile thermal decomposition products of the compounds
studied. The TG-MS system: derivatograph TG/DTA-SETSYS-16/18, mass spec-
trometer ThermoStar from Balzers, crucible Pt 100 µl. The other apparatus and mea-
suring conditions were the same as those described in [20, 21].
Results and discussion
The reaction between 4-bipy and M(ClCH2COO)2 afforded compounds of general
formula M(4-bipy)(ClCH2COO)2·nH2O, where n=1 for Mn(II), n=2 for Co(II) and
n=4 for Ni(II) and Cu(II). Diffractogram analysis indicated that the compounds iso-
lated were small crystalline solids. They were air-stable at room temperature. All the
complexes dissolved fairly well in water and methanol, decomposed in acid and
alcali and were insoluble in most organic solvents (carbon tetrachloride, benzene,
aceton, chloroform). The molar conductivity in methanol proved that the
Co(4-bipy)(ClCH2COO)2·2H2O is a non-electrolyte. The other obtained complexes
displayed a behaviour intermediate between those of non-electrolytes and 1:1 electro-
lytes [22]. Values higher than anticipated ΛM values (vide infra IR) are usually due to
the displacement of monochloroacetate ligands by solvent molecules. Similar behav-
iour has previously been observed in metal complexes with bipyridine and other aro-
matic amines [23–25].
Electronic and IR spectra
The assignments of d-d transition bands in the electronic spectra (in Nujol mulls, in
the range 26000–12000 cm–1) of the solid Co(II), Ni(II) and Cu(II) complexes are
based on the works of Lever [26] and Hathaway [27]. The electronic spectra of these
complexes are all consistent with a pseudohedral configuration with tetragonal dis-
tortion. The cobalt(II) complexes exhibit band at 21500 cm–1 which correspond to the
transition 4T1g(F)→4T1g(P). This band is apparently asymmetrical and has a shoulder
in the region ca. 20500 cm–1. The ligand field spectra of nickel(II) complex exhibit
3
only one spin allowed band (ca. 16200 cm–1), it is assigned to the A2g(F)→3T1g(F)
transition. The band due to the 3A2g(F)→3T1g(P) transition (ca. 26000 cm–1) is super-
imposed to intense charge transfer band. The copper(II) complex exhibited single ab-
sorption band in the visible region at 15750 cm–1, can be associated with three transi-
2
2
tions lying within one broad envelope (2B1g→2Eg, B1g→2B2g, B1g→2A1g). The
position, as well as and shape, of this band revealed tetragonal distortion of the Cu(II)
complex from the one-electron orbital ground state d
[27, 28].
x2 –y2
For consistency, only the fundamental vibration modes of 4-bipy and OCO-group
for obtained mixed complexes are reported in Table 2. The IR spectrum of free 4-bipy
owing to complex formation. The most characteristic ring vibration ν(CN) and ν(CC),
and pyridine breathing mode are observed in these compounds in the ranges (cm–1):
1600.0–1608.5, 1533.4–1541.0 and 1006.8–1015.0, respectively. These bands are shifted
towards higher frequencies in comparison to free 4-bipy [29]. IR spectra of these com-
plexes indicate that 4-bipy is coordinated to metal ion [21, 29]. The absorption bands
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CZAKIS-SULIKOWSKA et al.: 4,4’-BIPYRIDINE ADDUCTS
arising from asymmetric νas(OCO) and symmetric νs(OCO) vibration of OCO-groups ap-
pear at 1558.4–1590.0 and 1413.7–1425.3 cm–1, respectively. In the case of Mn(II),
Co(II) and Cu(II) complexes the νas(OCO) band is splitted into two. The values of the
separation of the bands νas and νs (∆ν=νas–νs) are smaller than those of the sodium salt
(∆ν=185 cm–1). On this basis one can suppose that the carboxylate groups in obtained
mixed-ligand complexes are bonded as bidentate chelating ligands [30–32].
Table 2 Principal IR bands (cm–1) for 4-bipy and OCO– groups in free ligands and their com-
plexes, where L=ClCH2COO–
b
Compound
ν(CN)
ν(CC)
γra
νas(OCO)
νs(OCO)
∆
Na(ClCH2COO) [30]
–
–
–
1603.0
1418.0
185.0
1590.0
1558.4
164.7
133.1
Mn(4-bipy)L2·H2O
1600.0
1533.4 1008.7
1425.3
1589.2
1569.9
173.5
154.2
Co(4-bipy)L2·2H2O
Ni(4-bipy)L2·4H2O
Cu(4-bipy)L2·4H2O
1606.6
1608.5
1608.5
1537.2 1006.8
1537.2 1008.7
1541.0 1015.0
1415.7
1413.7
1417.6
1589.2
175.5
1575.0
1558.4
157.4
140.8
aγr=ring ‘breathing’ mode; b∆=νas(OCO)–νs(OCO)
A strong, broad band in the water stretching region (ca. 3400–3500 cm–1) was
present in the IR spectra of all new complexes. The M–O stretching modes for coor-
Fig. 1 Thermoanalytical curves of Mn(4-bipy)(ClCH2COO)2·H2O (a),
Ni(4-bipy)(ClCH2COO)2 4H2O; (b)
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391
dinated water were observed at (cm–1): 489.0 (Cu), 478.3 (Co), 480.2 (Ni) and 472.5
(Mn).
Thermal decomposition
The decomposition solid products obtained during heating of M(4-bipy)(ClCH2COO)2·
nH2O complexes were established from thermoanalytical curves and confirmed by chem-
ical analysis together with the X-ray diffraction pattern investigation. The thermal analy-
sis curves of Ni(II) and Mn(II) complexes are presented, as an example, in Fig 1. The re-
sults are listed in Table 3. All the complexes decompose progressively.
Table 3 Thermal decomposition data of M(4-bipy)L2·nH2O (L=ClCH2COO–; sample mass 100 mg)
Mass loss/%
found calc.
Ranges of
decomposition/°C
Intermediates and
final solid products
Starting material
80–140
140–635
635–720
>900
4.8
68.2
9.0
4.3
Mn(4-bipy)L2
MnCl2 with ca. 3% Mn2O3
Mn2O3
Mn(4-bipy)L2·H2O
76.7
0.6
0.4
Mn3O4
100–120
160–880
>900
8.5
75.0
~0.8
8.2
73.5
1.2
Co(4-bipy)L2
Co3O4 with ca. 1.5% CoO
CoO
Co(4-bipy)L2·2H2O
Ni(4-bipy)L2·4H2O
100–140
140–700
15.0
69.0
15.2
69.0
Ni(4-bipy)L2
NiO
80–115
115–150
150–740
740–800
7.5
6.9
72.0
7.5
7.5
71.7
Cu(4-bipy)L2·2H2O
Cu(4-bipy)L2
Cu
Cu(4-bipy)L2·4H2O
mixture of Cu2O+CuO
The hydrated complexes M(4-bipy)(ClCH2COO)2·nH2O are stable up to
80–100°C and then lose all the water (inter or outer) molecules in one step (only
Cu(4-bipy)(ClCH2COO)2·4H2O in two steps). The TG curves exhibit sufficiently
clearly defined mass loss of these steps at the end of the dehydration process. The de-
hydration processes of Mn(II), Co(II), Ni(II) and Cu(II) complexes are connected
with endothermic effects at 100, 110, 118 and 100, 162°C, respectively. The TG
curves of M(4-bipy)(ClCH2COO)2 exhibited multiple mass loss steps, from which
only some can be defined (Table 3). Anhydrous complexes decompose to oxides with
intermediate formation of different products. Compounds of Mn(II), Co(II) and
Cu(II) decompose to final products via MnCl2, Mn2O3, Co3O4 and Cu. The DTA
curves are mixtures of several endo and exo peaks. Very strong and broad exothermic
effects originating from the oxidation of organic fragments are observed at ca. 440
(Mn), 460 (Co), 490 (Ni) and 350°C (Cu).
Apart from the chemical and X-ray analysis of the several solid products of de-
composition, mass spectrometric analysis of the major gaseous products of decompo-
sition was also carried out. Since the complexes studied here had similar composi-
tion, the MS data of these substances are similar. Figure 2 (as an example) presents
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CZAKIS-SULIKOWSKA et al.: 4,4’-BIPYRIDINE ADDUCTS
the composition of the gaseous mixture above the decomposition sample
Co(4-bipy)(ClCH2COO)2·2H2O as a function of time (heating rate of 10°C min–1).
Mass spectrum detected several ions signal intensities. Generally, the first signals are
observed at ca.120°C, and the last strong maxima occur at around 440°C. These MS
peaks coincide with the mass decrease appeared on TG. In all cases, when the temper-
ature of the sample raised, the first decomposition products detected were: H2O
(m/z=18), CO2 (m/z=44, 45, 46, 47), and fragments with m/z=12, 15, 17, 26 and 31.
H2O is observed in range 100–160 and 370–490°C. The first strong maximum (for
ion current) in the elimination of H2O occurs at around 120°C, which coincides with
elimination of coordination (or crystalline) water. Next, the H2O was produced dur-
ing the decomposition of organic ligands. The profiles observed for m/z=44, 45, 46,
Fig. 2 Ion current for m/z detected in the mass spectrometer vs. time. Complex
Co(4-bipy)(ClCH2COO)2·2H2O mass sample 9.02 mg; heating rate 10°C min–1,
original record
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47 (CO2) are similar to several maxima. Very strong CO2 peaks appeared at ca.190
and 440°C. The MS line for m/z=36 (O2 from air atmosphere) exhibits a minimum at
440°C. CH3Cl (m/z=50) starts to be detected at ca. 190°C and reaches a maximum
forming rate of CH3Cl at 285°C. The maximum rate of forming of HCl is observed at
610°C. The MS measurement showed also the presence of a small amount of Cl2
Fig. 3 TG curve for Co(4-bipy)(ClCH2COO)2·2H2O and ion current detected by the
MS for mass fragments m/z: 1 – 18; 2 – 50; 3 – 36, original record
Fig. 4 TG curve for Co(4-bipy)(ClCH2COO)2·2H2O and ion current detected by the
MS for mass fragments m/z: 1 – 44; 2 – 30; 3 – 70, original record
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(m/z=70, 74) in gaseous products of the decomposition. The fragments with m/z=30
correspond probably to CH2O or NO. They start to be detected at around 360°C and
reach a maximum rate of elimination at 440°C. A very low intensivity ion current (on
measuring error) is observed for 4,4’-bipyridine in the range 200–500°C. CO was not
detected. Similar observations have been made for other obtained complexes. TG
coupled with MS data for major decomposition products are presented in Figs 3
and 4. According to Lin et al. [18] HCl, CH3Cl, CO2 and H2O have been identified in
the mass spectra of Cu(ClCH2COO)2 as major decomposition products, while H2O,
CO, CO2, CH2O and ClCH2CHO were found as the products of thermal decomposi-
tion of Zn(ClCH2COO)2·2H2O [19].
Conclusions
By means of VIS and IR spectra, thermoanalytical and mass spectrometric measure-
ments, the following information about the coordination of the ligands with Mn(II),
Co(II), Ni(II) and Cu(II) and the thermal behaviours have been obtained.
The electronic spectra indicated pseudooctahedral environment around the
Co(II), Ni(II) and Cu(II).
The IR spectra of compounds indicate interaction of the 4,4’-bipyridine nitrogen
with the metal(II). The values of ∆ν=νas–νs for complexes correspond to the chelating
character of carboxylate groups.
The thermal decomposition of all studied complexes begins by the release of
water, bonded as coordinated or crystalline water. Dehydration begins at 80–100°C.
The thermal stability of the anhydrous complexes increase in the order: Mn=
Ni<Cu<Co. The anhydrous complexes decompose to metal oxides: Mn3O4, CoO,
NiO and mixture of CuO+Cu2O.
During the heating of M(4-bipy)(ClCH2COO)2 followed the decomposition of
organic ligands. H2O, CO2, CH2O (or NO), CH3Cl, HCl, Cl2 and other fragments were
found. As the first major decomposition products were detected H2O and CO2. Next,
on increase of the temperature the compounds containing chlorine are released. In air
atmosphere CO was not detected.
References
1 M. Melnik, Coord. Chem. Rev., 36 (1981) 1.
2 H. Kiriyama, M. Hashimoto and N. Okuno, Bull. Chem. Soc. Jpn., 60 (1987) 2983.
3 Y. Muto, T. Tokii, K. Chijiwa and M. Kato, Bull. Chem. Soc. Jpn., 57 (1984) 1008.
4 M. Nakashima, M. Mikuriya and Y. Muto, ibid., 58 (1985) 968.
5 M. Ahlgren, U. Turpeinen and R. Hämäläinen, Acta Chem. Scand., A 34 (1980) 67.
6 J. A. Moreland and R. J. Doedens, Inorg. Chem., 17 (1978) 674.
7 R. Tsuchida, S. Yamada and H. Nakamura, Nature, 181 (1958) 479.
8 S. Emori, K. Onishi, H. Kurichara and Y. Muto, Bull. Chem. Soc. Jpn., 61 (1988) 4439.
9 S. G. Shova, G. V. Novitsky, M. D. Mazus and A. P. Gulya, Dokl. Akad. Nauk SSSR, 337
(1994) 348.
J. Therm. Anal. Cal., 63, 2001

CZAKIS-SULIKOWSKA et al.: 4,4’-BIPYRIDINE ADDUCTS
395
10 S. G. Shova, L. G. Turyatke, G. V. Novitsky, M. D. Mazus and A. P. Gulya, Koord. Khim., 22
(1996) 517.
11 S. Sen, S. Mitra, P. Kundu, M. K. Saha, C. Krüger and J. Bruckmann, Polihedron, 16 (1997)
2475.
12 T. S. Kuntsevich, T. S. Tarkhova and A. V. Ablov, Dokl. Akad. Nauk SSSR, 243 (1978) 338;
ibid., 243 (1978) 649.
13 S. Garcia-Granda and F. Gómez-Beltrán, Acta Crystallogr., Sect. C (Cr. Str. Comm.), 40
(1984) 949.
14 X. Solans and C. Miravitlles, ibid., Sect. B. 37 (1981) 1407.
15 T. S. Kuntsevich, T. N. Turkhova and J. V. Khorushum, Zh. Strukt. Khim., 23 (1982) 111.
16 M. F. Obier, M. Dartiguenave and Y. Dartiguenave, Bull. Soc. Chim., (1971) 2520.
17 M. D. Judd, B. A. Plunkett and M. I. Pope, J. Thermal Anal., 9 (1976) 83.
18 D. C. K. Lin and J. B. Westmore, Canad. J. Chem., 51 (1973) 2999.
19 V. Zele×ak, K. Györyová and J. Simon, J. Thermal Anal., 46 (1996) 573.
20 D. Czakis-Sulikowska, J. RadwaÕska-Doczekalska, B. Kuünik and A. Malinowska, Trans. Met.
Chem., 21 (1996) 19; ibid., 20 (1995) 203.
21 D. Czakis-Sulikowska and J. Ka³uüna, J. Thermal Anal., 47 (1996) 1763.
22 W. J. Geary, Coord. Chem. Rev., 7 (1971) 81.
23 D. Czakis-Sulikowska and J. KaÓuüna, J. Therm. Anal. Cal., 58 (1999) 51; Polish J. Chem., 72
(1998) 2218.
24 D. Czakis-Sulikowska and A. Malinowska, J. Thermal Anal., 51 (1998) 575.
25 N. M. Karayannis, A. N. Speca, D. E. Chasen and L. L. Pytlevski., Coord. Chem. Rev., 20
(1976) 37.
26 A. B. P. Lever, Inorganic Electronic Spectroscopy, Elsevier, Amsterdam 1984.
27 B. J. Hathaway, J. Chem. Soc. Dalton, (1972) 1196.
28 M. Hvastijowa, J. Kohout, M. Okruhlica, J. MroziÕski and L. Jager, Trans. Met. Chem., 18
(1992) 175.
29 J. R. Ferraro and K. C. Davis, Inorg. Chim. Acta, 3 (1969) 685.
30 E. Spinner, J. Chem. Soc., (1964) 4217.
31 W. N. Alcock, V. M. Tracy and T. C. Waddington, J. Chem. Soc. Dalton Trans., 19 (1976) 2243.
32 K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, John
Wiley and Sons, New York 1997.
J. Therm. Anal. Cal., 63, 2001