Indian Journal of Chemistry
Vol. 46A, September 2007, pp. 1406-1413
Spectral and structural studies of S-methyl and S-benzyl dithiocarbazate
azomethine complexes of lanthanum
Ritu Singha, S P Mittalb, Sachin Malika & R V Singha,*
aDeaprtment
of Chemistry, University of Rajasthan, Jaipur 302 004, India
of Chemistry, D.A.V. College, Dehra Dun, India
Email: rvsjpr@hotmail.com; singh-rv@uniraj.ernet.in
bDepartment
Received 30 March 2007; revised 2 August 2007
Synthesis and characterization of different types of lanthanum(III) complexes with azomethines are reported here.
Bibasic tridentate azomethine ligands namely S-methyl dithiocarbazate (DTCZ1H2) and S-benzyl dithiocarbazate
(DTCZ2H2) react with lanthanum isopropoxide in anhydrous benzene liberating different amounts of moles of isopropanol
depending on the stoichiometry (1:1, 2:3 and 1:2). The derivatives have been characterized by the elemental analyses,
magnetic susceptibility and spectral studies including IR, 1H NMR and electronic spectra. The X-ray diffraction studies of
these complexes have also been carried out to establish their molecular symmetry and lattice constants. The complexes are
highly hygroscopic and become sticky when exposed to the open atmosphere due to the presence of labile isopropoxy
groups. The X-ray studies reveal that these complexes crystallize in orthorhombic molecular symmetry.
IPC Code: Int. Cl.8 C07F17/00
Coordination complexes of metals are gaining
importance in recent years particularly in the design
of repository, slow release or long acting drugs in
nutrition and in the study of metabolism1. Metal ions
are known to accelerate the drug action2. Metal
complexes of the Schiff bases have also been widely
studied due to their unusual magnetic properties,
novel structural features and relevance to the
biological systems3. Lanthanide complexes have been
studied4 for their interesting and important properties,
for example, their reversibly ability to bind oxygen,
catalytic activity in hydrogenation of olefins,
structural probes in biological systems and the
development of shift reagents5. Lanthanides(III) with
ionic radii of 1.06-0.85 Å and a +3 charge fulfill the
optimum conditions for higher coordination6. The
metal complexes involving S-methyl dithiocarbazate
and S-benzyl dithiocarbazate with nitrogen and
sulphur donor atoms are of tremendous importance
due to their structural peculiarities and their
pharmacological applications7,8. It has been noted that
the replacement of aromatic group by the resorcenyl
group in the penicillin and cephalosphorine improves
their antibiotic activities9. A careful survey of
literature shows that systematic studies of
dithiocarbazate complexes of lanthanum is lacking.
Therefore, it was decided to synthesize and
characterize some lanthanum complexes of S-methyl
and S-benzyldithiocarbazates. The structures of the
ligands used are:
SR3
H3C
SR3
H3C
NH
S
N
N
SH
N
H
H
O
O
R4
R4
SR3
SR3
R2
R2
N
NH
N
SH
N
S
R1
R1
, R2 = H, R3 = CH3 (L1H2)
OH
R1 =
OH ,
R2 = H, R3 = CH3 (L2H2)
R1 =
OH
R2 = CH3, R3 = CH3 (L3H2)
,
R1 =
R2 = H, R3 = CH2C6H5 (L4H2)
OH ,
R1 =
OH
R1 =
,
R2 = H, R3 = CH2C6H5 (L5H2)
SINGH et al.: STUDIES ON DITHIOCARBAZATE AZOMETHINE COMPLEXES OF LANTHANUM
OH
,
R2 = CH3, R3 = CH2C6H5 (L6H2)
distillation and the resulting products were dried at
~50C/0.5 mm for ~2 h.
R1 =
R4 =
R4 =
R4 =
R4 =
1407
CH3, R3 = CH3 (L7H2)
CH3, R3 = CH2C6H5 (L8H2)
C6H5, R3 = CH3 (L9H2)
C6H5, R3 = CH2C6H5 (L10H2)
Synthesis of the complexes in 2:3 molar ratio
Materials and Methods
All the chemicals and solutions used were of
analytical grade and adequate precautions were taken
to exclude moisture from the glass apparatus as well
as chemicals used. Isopropoxide of lanthanum was
prepared by the sodium alkoxide method10. S-methyl
dithiocarbazate and S-benzyldithiocarbazate were
prepared by the method of Bahr and Schleitzer11.
All the ten ligands (L1H2 to L10H2) were prepared as
reported12,13. Their physical properties and analytical
data are given in Table 1.
Synthesis of the complexes in 1:1 molar ratio
Lanthanum(III) isopropoxide (1.24-1.42 g) was
mixed with the S-(methyl or benzyl) dithiocarbazate
azomethines (0.89-1.18 g) in 1:1 molar ratio in
presence of anhydrous benzene (50 mL). The reaction
mixture was then refluxed for about 4-5 h and the
liberated isopropanol was estimated azeotropically at
different time intervals. On complete removal of the
isopropanol, the excess of the solvent was removed by
Lanthanum(III) isopropoxide (1.09-1.26 g) was
dissolved in anhydrous benzene (60 mL) and the
required amount of S-(methyl or benzyl)dithiocarbazate azomethines (1.17-1.53 g) in the
molar ratio 2:3 was added. It was then refluxed for
9-10 h and the binary azeotrope of isopropanol with
benzene collected till the distillate attained a constant
temperature of 80C. The products were freed from
solvent and then dried at 40-60C/0.5 mm for ~3 h.
Synthesis of the complexes in 1:2 molar ratio
Lanthanum(III) isopropoxide (0.96-1.50 g) was
dissolved in anhydrous benzene (60 mL) and the
required amount of S-(methyl or benzyl)dithiocarbazate azomethines (1.37-1.92 g) in the
molar ratio 1:2 was added. It was then refluxed for
12-14 h and the binary azeotrope of isopropanol with
benzene collected. The products were separated from
solvent and then dried at 40-60C/0.5 mm for ~3 h.
The physical properties and analytical data of these
complexes are recorded in Table 2.
Analytical methods and physical measurements
Infrared spectra were recorded on a Nicolet Megna
FTIR-550 spectrophotometer on KBr pellets. 1H
Table 1 — Properties and analyses of the bibasic tridentate S-(methyl and benzyl) dithiocarbazate azomethines
Schiff base
L1H2
HOC6H4CH:NNHCSSCH3(C9H10N2OS2)
L2H2
HOC10H6CH:NNHCSSCH3(C13H12N2OS2)
L3H2
HOC6H4C(CH3):NNHCSSCH3(C10H12N2OS2)
L4H2
HOC6H4CH:NNHCSSCH2C6H5(C15H14N2OS2)
L5H2
HOC10H6CH:NNHCSSCH2C6H5(C19H16N2OS2)
L6H2
HOC6H4C(CH3):NNHCSSCH2C6H5(C16H16N2OS2)
L7H2
CH3C(OH)CHCCH3:NNHCSSCH3(C7H12N2OS2)
L8H2
CH3C(OH)CHCCH3:NNHCSCH2C6H5(C13H16N2OS2)
L9H2
C6H5C(OH)CHCCH3:NNHCSSCH3(C12H14N2OS2)
L10H2
C6H5C(OH)CHCCH3:NNHCSSCH2C6H5(C18N18N2OS2)
Colour
M.pt.
(C)
Creamish
202
Dark yellow
217
Creamish
169
Creamish
185
Dark yellow
205
Creamish
yellow
Yellow
132
Yellow
60
Yellow
145
Yellow
80
138
C
47.20
(47.61)
57.15
(56.52)
50.67
(50.00)
59.40
(59.60)
64.56
(64.77)
60.98
(60.75)
41.62
(41.17)
55.49
(55.71)
53.75
(54.13)
63.42
(63.15)
Found (Calc.) (%)
H
N
4.32
(4.41)
4.57
(4.34)
4.84
(5.00)
4.68
(4.63)
4.61
(4.54)
5.10
(5.06)
6.01
(5.88)
5.75
(5.71)
5.32
(5.26)
5.30
(5.26)
12.1
(12.30)
10.25
(10.14)
11.50
(11.66)
9.21
(9.27)
8.02
(7.95)
8.75
(8.86)
13.56
(13.72)
9.88
(10.00)
10.75
(10.52)
8.10
(8.18)
S
27.99
(28.31)
23.45
(23.18)
27.00
(26.66)
21.09
(21.19)
18.30
(18.18)
20.07
(20.25)
31.14
(31.37)
22.70
(22.85)
23.78
(24.06)
18.90
(18.71)
INDIAN J CHEM, SEC A, SEPTEMBER 2007
1408
Table 2Physical properties and analytical data of lanthanum(III) complexes of S-(methyl and benzyl) dithiocarbazate azomethines
Compound
Colour
La(OC3H7i)(C9H8N2OS2)
Lemon yellow
La2(C9H8N2OS2)3
M.Pt. (C)
Molecular weight
Found (Calc.)
>340d
886.87 (422.32)
Yellow
318 - 20d
1027.00 (950.75)
La(C9H8N2OS2)(C9H9N2OS2)
Yellow
260 - 62d
647.39 (588.54)
La(OC3H7i)(C13H10N2OS2)
Yellow brown
250 - 52d
971.85 (472.38)
La2(C13H10N2OS2)3
Yellowish brown
204 - 06d
1129.45 (1100.96)
La(C13H10N2OS2)(C13H11N2OS2)
Dirty yellow
186 - 88d
705.40 (688.68)
La(OC3H7i)(C10H10N2OS2)
Lemon yellow
308 - 10d
846.80 (436.35)
La2(C10H10N2OS2)3
Lemon yellow
275 - 77d
956.19 (992.85)
La(C10H10N2OS2)(C10H11N2OS2)
Yellow
230 - 32d
649.77 (616.61)
La(OC3H7i)(C7H10N2OS2)3
Yellow
282 - 84d
830.10 (400.32)
La2(C7H10N2OS2)3
Yellow
198 - 200d
907.53 (884.76)
La(C7H10N2OS2)(C7H11N2OS2)
Dark yellow
158 - 60d
521.89 (544.54)
La(OC3H7i)(C12H12N2OS2)
Dark yellow
255 - 57d
953.11 (462.38)
La2(C12H10N2OS2)3
Yellow brown
225 - 27d
1103.23 (1070.96)
La(C12H12N2OS2)(C12H13N2OS2)
Dark brown
120 - 22
641.33 (668.68)
La(OC3H7i) (C15H12N2OS2)
Yellow
254 - 55d
1052.00 (498.44)
La2(C15H12N2OS2)3
Yellow
225 - 26d
1095.56 (1179.14)
La(C15H12N2OS2)(C15H13N2OS2)
Yellow
184 - 85d
700.25 (740.80)
La(OC3H7i) (C19H14N2OS2)
Brown
258 - 60d
1059.45 (548.48)
La2(C19H14N2OS2)3
Brown
241 - 43d
1361.08 (1329.26)
La(C19H14N2OS2)(C19H15N2OS2)
Brown
221 - 23d
811.23 (840.88)
La (OC3H7i) (C16H14N2OS2)
Yellow
268 - 70d
978.97 (512.44)
La2(C16H14N2OS2)3
Yellow
240 - 42d
1252.75 (1221.14)
La(C16H14N2OS2)(C16H15N2OS2)
Dark yellow
195 - 97d
800.57 (768.80)
La(OC3H7i) (C13H14N2OS2)
Yellow
320 - 24d
979.36 (476.41)
La2(C13H14N2OS2)3
Light brown
294 - 95d
1084.96 (1113.05)
La
32.80
(32.91)
29.35
(29.22)
23.74
(23.60)
29.75
(29.41)
25.02
(25.23)
20.55
(20.18)
31.61
(31.84)
28.32
(27.99)
22.74
(22.53)
34.17
(34.70)
31.64
(31.39)
25.15
(25.52)
30.51
(30.04)
26.35
(25.34)
20.39
(20.77)
27.69
(27.87)
23.71
(23.57)
18.87
(18.75)
25.72
(25.33)
21.25
(20.90)
16.29
(16.52)
27.30
(27.11)
22.92
(22.76)
18.32
(18.07)
29.64
(29.16)
25.17
(24.97)
Found (Calc.), %
N
6.71
(6.64)
8.96
(8.84)
9.67
(9.52)
6.03
(5.93)
7.47
(7.64)
8.30
(8.14)
6.61
(6.42)
8.29
(8.47)
9.23
(9.09)
7.16
(7.00)
9.57
(9.50)
10.43
(10.29)
6.19
(6.06)
8.01
(7.85)
8.54
(8.38)
5.77
(5.62)
7.01
(7.13)
7.64
(7.56)
5.18
(5.1)
6.41
(6.32)
6.81
(6.66)
5.39
(5.47)
6.99
(6.88)
7.36
(7.28)
5.69
(5.88)
7.77
(7.55)
S
15.25
(15.19)
20.12
(20.23)
21.62
(21.80)
13.75
(13.58)
17.75
(17.48)
18.37
(18.63)
14.95
(14.70)
19.55
(19.37)
21.01
(20.81)
15.75
(16.03)
21.38
(21.74)
24.10
(23.56)
14.10
(13.87)
18.25
(17.97)
18.89
(19.18)
12.98
(12.86)
16.49
(16.32)
17.19
(17.32)
11.50
(11.69)
14.28
(14.47)
15.58
(15.25)
12.42
(12.51)
15.54
(15.76)
16.89
(16.68)
13.59
(13.46)
17.07
(17.29)
Contd.
SINGH et al.: STUDIES ON DITHIOCARBAZATE AZOMETHINE COMPLEXES OF LANTHANUM
1409
Table 2Physical properties and analytical data of lanthanum(III) complexes of S-(methyl and benzyl) dithiocarbazate
azomethines(Contd.)
Compound
Colour
M.pt. (C)
Molecular weight
Found (Calc.)
La
Found (Calc.), %
N
S
La(C13H14N2OS2)(C13H15N2OS2)
Brown
208 - 10d
719.69 (696.74)
20.27
(19.95)
8.15
(8.04)
18.28
(18.42)
La(OC3H7i) (C18H16N2OS2)
Dark yellow
245 - 47d
1110.20 (538.48)
26.16
(25.80)
5.03
(5.20)
12.10
(11.91)
La2(C18H16N2OS2)3
Orange
132 - 34
1325.97 (1299.26)
21.02
(21.38)
6.31
(6.47)
15.07
(14.81)
La(C18H16N2OS2)(C18H17N2OS2)
Yellowish brown
125 - 27
789.52 (820.88)
17.09
(16.92)
6.91
(6.82)
15.45
(15.63)
NMR spectra were recorded on a JEOL-AL-300 FT
NMR spectrometer in DMSO-d6 using TMS as the
internal standard14. Electronic spectra of the
complexes were recorded in chloroform on a UV160A Shimadzu spectrophotometer in the range 200600 nm15. Molecular weight determinations were
carried out by the Rast Camphor Method. The metal
contents were estimated complexometrically with
EDTA using Erichrome Black T as an indicator.
Molar conductance measurements were made in
anhydrous DMF on a Systronics model 305
conductivity bridge16. The magnetic moments and
magnetic susceptibility were measured by Gouy’s
method at room temperature (37±1C). Sulphur and
nitrogen were estimated by the Messenger’s and
Kjeldahl’s method, respectively.
Results and Discussion
The reactions in different stoichiometric ratios, 1:1,
2:3 and 1:2, may be depicted by:
1:1
La(OC3H7i)3 + DTCZ1H2
La(OC3H7i)(DTCZ1)+2C3H7iOH
2:3
2La(OC3H7i)3 + 3DTCZ1H2
La2(DTCZ1)3 + 6C3H7iOH
1:2
La(OC3H7i)3 + 2DTCZ1H2
La(DTCZ1)(DTCZ1H) + 3C3H7iOH
Similar reactions were also carried out with
DTCZ2-10H2.
La(OC3H7i)
(DTCZ1)
and
i
2-10
La(OC3H7 )(DTCZ ) types of complexes are highly
hygroscopic and became sticky when exposed to the
open atmosphere due to the presence of labile
isopropoxy
groups.
The
complexes
were
characterized on the basis of the spectral studies.
IR spectra
IR spectra of all the ligands, show a strong and
broad absorption band in the region 3450-3150 cm-1
which may be assigned to the intramolecular
hydrogen bonded OH or NH streching vibrations.
This band disappears in the corresponding 1:1, 2:3
and 1:2 derivatives and thereby shows the
deprotonation of the phenolic or enolic protons
accompanied by the chelation of the lanthanide atom
to both the oxygen and nitrogen atoms of the ligand
moieties. The absence of any band in the region 26002500 cm-1 indicates that the ligands exist in the thione
form in the solid state. However, the solution IR
spectra of the ligands display a band at ~2570 cm-1 in
addition to the former due to SH vibrations and
therefore indicate an equilibrium with the tautomeric
form (thiolo) in solution. Both these bands of the
ligands disappear in 1:1 and 2:3 lanthanum complexes
suggesting that the deprotonation at the -nitrogen
atom on complexation takes place through the
thioenolization while in the case of 1:2 lanthanum
complexes, the presence of a band at ~3150 cm-1
indicates that at least one proton of one of the nitrogen atoms of the ligands moiety does not
undergo deprotonation. It is further supported by the
presence of a strong band at ~1050 cm-1 at almost the
same position as in the ligands due to C=S which
also does not appear in the 1:1 and 2:3 complexes.
All the ligands display a strong and sharp band at
~1620 cm-1, which may be assigned to the C=N
stretching vibrations. This band gets shifted to the
lower frequency by 20-30 cm-1 in the IR spectra of all
the lanthanum complexes along with its splitting due
1410
INDIAN J CHEM, SEC A, SEPTEMBER 2007
to the formation of >C=N-N=C< group in the
complexes. This may be due to the coordinate bond
formation from one of the unsaturated nitrogen of the
azomethine group to the lanthanum atom17. A strong
band at ~1280 cm-1 in the azomethines derived
from salicylaldehyde, 2-hyroxy-1-naphthaldehyde and
2-hydroxyacetophenone may be due to the phenolic
C-O stretching vibration, which shifts to the higher
frequency (~1300 cm-1) in the corresponding
complexes showing thereby the bonding of the
lanthanum atom through phenolic oxygen. In the case
of the azomethines derived from 2,4-pentanedione or
1-phenyl-1,3-butanedione, a sharp band at ~1700 cm-1
may be assigned to C=O stretching vibrations, thus
ensuring that the ligands exist in the keto form. The
absence of this band in the corresponding lanthanum
complexes shows the enolization of these ligands as
well as bonding through oxygen to the lanthanum
atom.
Some new medium to weak intensity bands in the
regions, 680-660 cm-1 and 640-610 cm-1 have been
observed in the lanthanum complexes and these may
be assigned to the ring deformation, coupled
stretching vibrations of La-O and C-CH3 and C-H
out-of-plane deformation coupled with La-O
stretching modes, respectively while the weak
intensity bands at 380  10 and 305  10 cm-1 in the
far infrared region are due to La-N and La-S
vibrations. Thus, the foregoing infrared spectral
studies suggest that these ligands behave as bibasic
tridentate species with ONS donor system and
coordinate to the central lanthanum atom through the
phenolic oxygen, azomethine nitrogen and thiolic
sulphur (Fig. 1).
1H
NMR spectra
The proposed structures for the 1:1, 2:3 and 1:2
lanthanum complexes get further support by a
comparison of the 1H NMR spectrum of the ligand, S(benzyl)-β-N-2-hydroxyphenyl)methyldithiocarbazate
with its corresponding lanthanum complexes. Their
chemical
shift values (,Oppm) are given in Table 3.
O
O
The bonding of the phenolic oxygen of the ligand
in the complexes is substantiated by the disappearance
Ln
N phenolic
N signal, which
Ln
N
of the
OH proton
is observed
as a broad signal at  11.42 ppm in the ligand. This is
further
supported by the Sdownfield shift of
the
S
S
resonance signal of aromatic protons as shown in 2:3
Table 3 due to their deshielding on bonding through
phenolic oxygen and azomethine nitrogen to the
lanthanum atom.
The methyl azomethine proton signal [-C-CH3=N-)
in the ligand is observed at  2.40 ppm and it shifts
downfield ( 2.55-2.85 ppm) in the lanthanum
complexes due to its coordination to the lanthanum
atom, while in the case of 1:2 lanthanum complex,
two signals at  2.40 and 2.60 ppm appear showing
the coordination from different nitrogen atoms of the
two ligand moiety in the complex. Further, the NH
proton signal of the ligand is observed at  10.15 ppm
and the disappearance of this signal in all the
complexes
indicates
the
deprotonation
on
complexation. However, in 1:2 lanthanum complex, a
C3H7i
O
O
O
Ln
N
Ln
N
O
C3H7i
S
O
1:1
O
O
Ln
N
N
S
HS
1:2
O
O
Ln
N
N
Ln
S
S
O
O
N
N
S
S
2:3
2:3
O
O
N
S
Ln
O
N
Ln
S
N
S
Fig. 1Proposed structures of the metal complexes
Ln
SINGH et al.: STUDIES ON DITHIOCARBAZATE AZOMETHINE COMPLEXES OF LANTHANUM
1411
Table 31H-NMR spectral data of S-(benzyl)-β-N-(2-hydroxyphenyl)methyldithiocarbazate and its 1:1, 2:3 and 1:2 lanthanum(III)
complexes in (ppm) with TMS as internal reference
Compound
-OH
C6H4 and
C6H5
CH3
-NH or
–SH
CH2
H-C(Isopropoxy)
o-HOC6H4C(CH3):NNHCSSCH2C6H5
[(CH3)2HCOLa(o-OC6H4C(CH3):NNCSSCH2C6H5)]
La2(o-OC6H4C(CH3):NNCSSCH2C6H5)3
[(o-OC6H4C(CH3):NNCSSH2C6H5)La(o-C6H4C
(CH3)**:NNC(SH)SCH2C6H5]
11.42
7.29
7.35 - 7.80m
7.35 - 7.60m
7.35 - 7.75
2.40
2.50 - 2.85bs
2.55
2.45** - 2.60
10.15s
4.68
4.70
4.80
4.60

0.25





5.15s


Table 4X-ray powder diffraction data of La(OC3H7i) (C9H8N2OS2)
dobsd (Å)
Qobsd = 1/d2
Qcalcd
hkl
dobsd (Å)
Qobsd = 1/d2
Qcalcd
hkl
18.587m
15.628s
13.692s
12.017w
11.325m
9.983w
9.709m
8.036m
7.075m
6.804w
6.320vw
4.831w
3.897vw
3.798w
3.559vw

3.218vvw

0.0029
0.0041
0.0053
0.0069
0.0078
0.0100
0.0106
0.0155
0.0200
0.0216
0.0250
0.428
0.0659
0.0693
0.0790

0.0966

0.0029
0.0041
0.0050
0.0062
0.0079
0.0098
0.0108
0.0158
0.0200
0.0214
0.0248
0.0432
0.0656
0.0693
0.0788
0.0800
0.0967
0.0972
010
011
100
101
110
102
003
103
200
122
202
006
044
036
207
400
154
009
3.045m
2.869m
2.646m
2.601w
2.450w
2.369vvw

2.182w
1.992w
1.918vw
1.896vw
1.865vvw
1.816vw
1.758w
1.734vw
1.689w
1.625w
1.584w
0.1077
0.1214
0.1429
0.1478
0.1665
0.1781

0.2100
0.2520
0.2719
0.2781
0.2876
0.3033
0.3232
0.3327
0.3505
0.3786
0.3985
0.1075
0.1214
0.1421
0.1476
0.1666
0.1771
0.1800
0.2100
0.2521
0.279
0.2779
0.2882
0.3036
0.3233
0.3329
0.3506
0.3794
0.3979
155
345
070
066
525
175
600
605
475
572
715
706
664
671
673
761
765
773
Table 5X-ray powder diffraction data of La2(C9H8N2OS2)3
dobsd (Å)
Qobsd = 1/d2
Qcalcd
hkl
dobsd (Å)
Qobsd = 1/d2
Qcalcd
hkl
21.020m
15.768 m
13.083w
11.936w
10.974s
9.302m
8.581m
7.928w
7.525w
7.190m
6.505m
5.693m
5.483w
4.844w
4.754m
4.458m


0.0024
0.0040
0.0058
0.0070
0.0083
0.0116
0.0136
0.0159
0.0177
0.0194
0.0236
0.0308
0.0333
0.0426
0.0442
0.0503


0.0024
0.0045
0.0059
0.0068
0.0083
0.0112
0.0134
0.0160
0.0153
0.0175
0.0192
0.0236
0.0311
0.0332
0.0428
0.0443
0.0501


011
012
100
020
111
004
121
031
030
005
015
200
221
222
215
144
238


3.682m
3.477w
3.437vw
3.264vw
3.156vw
3.066m
2.773w
2.684vvw
2.466m
2.322vuw
2.169vw
2.120vw
1.994vw
1.879vvw
1.812vvw
1.796m
1.717w
1.664w
1.612w
0.0738
0.0827
0.0847
0.0939
0.1004
0.1064
0.1300
0.1388
0.1644
0.1855
0.2125
0.2225
0.2516
0.2832
0.3045
0.3098
0.3391
0.3589
0.3824
0.0736
0.0827
0.0848
0.0944
0.1004
0.1067
0.1299
0.1391
0.1650
0.1859
0.2124
0.2220
0.2508
0.2824
0.3044
0.3107
0.3392
0.3591
0.3824
156
157
260
406
174
175
357
445
505
544
600
622
644
6010
730
733
727
7010
6010
INDIAN J CHEM, SEC A, SEPTEMBER 2007
1412
singlet is observed at  5.15 ppm, which corresponds
to the presence of one mercapto (-SH) group showing
the non-participation in bond formation through one
(-SH) group of the two ligand moiety.
Electronic spectra
The ligands show bands at ~215 nm and ~250 nm
attributable to -* electronic transitions within the
benzenoid ring and the auxochrome (-OH group) and
chromophore (>C=N-group) attached to the benzene
ring are responsible for the shift of these bands to the
lower energy region. These bands shift to 245 nm and
260 nm in the corresponding compounds due to an
increase of electron density on the auxochromic
oxygen and chromophoric nitrogen. The ligands
further show two maxima at ~310 and ~410 nm,
which have been assigned to the -* and n-*
transitions of the >C=N-chromophore and which shift
to the lower frequency side in the lanthanum
complexes.
X-ray diffraction
X-ray diffraction studies of the powdered samples
were carried out as it could not be possible to grow
suitable crystals for complete X-ray analysis. The
interplanar spacings ‘d’ values have been measured
from the powdered diffractograms and these are
reported along with their reciprocal lattice values `Q’
in Tables 4 to 6 for three representative complexes,
La(OC3H7i)(C9H8N2OS2),
La2(C9H8N2OS2)3
and
La(C9H8N2OS2)(C9H9N2OS2). A comparative study of
the interplanar spacing values ‘d’ of the above
complexes of different compositions shows that these
are X-ray isomorphones, and thus further support the
idea of similar environment, i.e. bonding pattern
around the lanthanum atoms in these complexes. The
indexing of the Millar indices, h, k, l has been done
for each observed Q value and the process of indexing
reveals that these complexes crystallize in the same
type of orthorhombic molecular symmetry. The unit
cell dimensions for these complexes are given in
Table 7.
Magnetic measurements
To study the magnetic behaviour of the lanthanum
complexes, the magnetic susceptibility was measured
by Gouy’s method at room temperature (371C).
The lanthanum derivatives are diamagnetic since their
Table 6X-ray powder diffraction data of La(C9H8N2OS2)(C9H9N2OS2)
dobsd (Å)
Qobsd = 1/d2
Qcalcd
hkl
dobsd (Å)
17.144w
14.129m
12.353s
10.906vs
10.333w
7.893m
7.132w
6.343w
5.675vs
5.483w
4.924s
4.525w
4.120m
3.966w
3.863w
3.573vw

0.0034
0.0050
0.006
0.0084
0.0094
0.0160
0.0197
0.0249
0.0310
0.0333
0.412
0.0488
0.0589
0.0636
0.0670
0.0783

0.0034
0.0049
0.0068
0.0083
0.0100
0.0153
0.0196
0.0247
0.0306
0.0332
0.0408
0.0425
0.0485
0.0593
0.0628
0.0661
0.0784

010
100
002
110
111
021
200
211
030
014
220
024
005
223
140
313
313
142
400
3.424vw
3.293w
2.837m
2.769w
2.669vw
2.594w
2.399w
2.307vvw
2.225w
2.060vvw
1.883w
1.802 m
1.743vvw
1.668 w
1.581 vvw




Qobsd = 1/d2
Qcalcd
hkl
0.0853
0.0922
0.1242
0.1304
0.1404
0.1486
0.1737
0.1878
0.2019
0.2354
0.2819
0.3079
0.3292
0.3594
0.3999




0.0850
0.0920
0.1242
0.1308
0.1410
0.1488
0.1733
0.1879
0.2015
0.2347
0.2826
0.3075
0.3289
0.3595
0.4003




050
420
501
351
327
262
362
271
273
518
705
194
803
815
851




Table 7Unit cell parameters of lanthanum(III)-S-(methyl)--N-(2-hydroxyphenyl) methylene dithiocarbazate complexes
Compound
a
(Å)
b
(Å)
c
(Å)



d
(g/c.c)
V10-24
(cm3)
%
La(OC3H7i) (C9H8N2OS2)
La2(C9H8N2OS2)3
La(C9H8N2OS2)(C9H9N2OS2)
13.692
13.084
14.264
18.587
23.872
17.144
29.129
37.207
24.705
90
90
90
90
90
90
90
90
90
1.23
1.15
0.98
7413
11610
6040
12
8
6
SINGH et al.: STUDIES ON DITHIOCARBAZATE AZOMETHINE COMPLEXES OF LANTHANUM
specific magnetic susceptibilities have been found to
range from –0.30  10-6 to –1.25  10-6 c.g.s. unit as
expected for La+3 ion with 4fo electronic
configuration.
5
Conclusions
The analytical data and spectral studies show that
the complexes are pentacoordinated. The complexes
are highly hygroscopic and become sticky when
exposed to open atmosphere. The X-ray studies reveal
that the complexes crystallize in orthorhombic
molecular symmetry.
8
6
7
9
10
11
12
13
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