CHAPTER 4 SYNTHESIS AND SPECTRAL CHARACTERISATION...
Transcript of CHAPTER 4 SYNTHESIS AND SPECTRAL CHARACTERISATION...
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CHAPTER 4
SYNTHESIS AND SPECTRAL CHARACTERISATION OF
Ni (II) COMPLEXES DERIVED FROM PARENT AND N(4)
SUBSTITUTED 5–CHLORO-2–HYDROXYACETOPHENONE
METHYL THIOSEMICARBAZONES
4.1 INTRODUCTION
Nickel is divalent and exists as Ni (II) in most complexes.
Ni (II) complexes exhibit usually four coordinate square planer or
tetrahedral geometries. Six coordinate octahedral complexes of Ni (II) are
also reported [141, 142]. Ni (II) complexes are generally diamagnetic and
some paramagnetic complexes have also been reported [143], square
pyramidal complexes of Ni (II) are rather unusual and when encountered
exists as a result of particular circumstances in the complex rather than any
intrinsic tendency on the part of Ni (II) ion to attain the structure. It has
been shown that many metal complexes with sulphur containing schiff
bases exhibit anticancer activity [90]. Ni (II) complexes of
thiosemicarbazones of aromatic ortho–hydroxy aldehydes, in particular
salicylaldehyde are used as homogeneous catalysts. [144, 145]. In most of
the thiosemicarbazones NNS tridentate system is present with carcinostatic
potency [146]. This chapter describes the synthesis, spectral
characterization of four and five coordinate Ni (II) complexes derived from
parent and N(4) substituted 5–chloro-2–hydroxy acetophenone methyl
thiosemicarbazone.
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4.2 EXPERIMENTAL:
4.2.1 Chemicals and Methods:
5–Chloro-2–hydroxy acetopohenone thiosemicarbazone and
N(4) substituted methyl thiosemicarbazone, NiCl2.6H2O (Aldrich), ethanol
(A.R. Grade).
4.2.2 Synthesis of complexes and adducts:
Procedure for the synthesis of Ni (II) complexes of L :
The nickel chloride (NiCl2.6H2O 0.001 M) dissolved in
minimum quantity of ethanol was added to hot ethanoic solution of L
(0.001 M). The reaction mixture was heated on hot plate at 80–90 °C for 7–8
hours with constant stirring. The complex which separated overnight as
microcrystalline powder was thoroughly washed with hot water, cold
ethanol and finally with diethyl ether and dried in vacuum.
Reflux
OH
ClN
NH
NH2 Cl
O
NN NH2
SNi
OH2
NiCl2.6H2O
CH3CH3
S
Procedure for the synthesis of adducts :
Adducts of the type NiLB (B = pyridine, 2,2' bipyridine, 1,10
phenanthroline, a–picoline, b–picoline) were prepared by mixing 0.001
mole of heterocyclic base in ethanol with a hot solution of L (0.001 M) in
ethanol (20 ml) and adding a hot and filtered solution of NiCl2.6H2O (0.001
M) in ethanol with constant stirring. The mixture was heated under reflux
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for 7–8 hours. The adducts which separated overnight as microcrystalline
powders were thoroughly washed with hot water, cold ethanol and then
finally with diethyl ether and dried over P4O10 in vacuum.
Reflux
OH
Cl
CH3
N
NH
NH2
S
O
Cl
CH3
N
N NH2
SNi
B
O
Cl
CH3
N
N NH2
SNi
NN
B + NiCl2.6H2O
(Where B = pyridine,α/β-picoline, = bipyridine, 1,10 phenanthroline )
Procedure for the synthesis of Ni (II) complex of L’:
The nickel chloride (NiCl2.6H2O, 0.001 M) dissolved in
minimum quantity of ethanol was added to hot ethanolic solution of L’
(0.001 M). The reaction mixture was heated on hot plate at 80–90 °C for 7–8
hours with constant stirring. The complex which separated overnight as
microcrystalline powder was thoroughly washed with hot water, cold
ethanol and finally with diethyl ether and dried in vacuum.
Reflux
OH
ClN
NH
NH
CH3
Cl
O
NN NH
SNi
OH2
NiCl2.6H2O
CH3CH3
CH3
S
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Procedure for the Synthesis of Adducts –
Adducts of the type NiL’B (B = pyridine, 2–2 bipyridine, 1,10
phenanthroline, a–picoline, b–picoline) were prepared by mixing 0.001
mole of heterocyclic base in ethanol with a hot solution of L’ (0.001 M) in
ethanol (20 ml). To this was added hot and filtered solution of NiCl2.6H2O
(0.001 M) in ethanol with constant stirring. The mixture was heated under
reflux for 5–8 hours. The adducts which separated overnight as
microcrystalline powders were thoroughly washed with hot water, cold
ethanol and then finally with diethyl ether and dried over P4O10 in vacuum.
Reflux
OH
Cl
CH3
N
NH
NH
S
O
Cl
CH3
N
N NH
SNi
B
O
Cl
CH3
N
N NH
SNi
NN
CH3
CH3
CH3
B + NiCl2.6H2O
(Where B = pyridine,α/β-picoline, = bipyridine, 1,10 phenanthroline )
4.2.3 Physical Measurements :
Colour yield, molar conductivity and magnetic behaviour of
metal complexes is presented in Table No.4.2.3.
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Table No. 4.2.3 : Colour yield, molar conductance and magnetic moments
of nickel complexes
Sr.
No.
Complex Colour Yield
%
Molar
conductance
Ώ-1cm2mole-1
Magnetic
moment in B.M.
1. [NiLH2O] Brown 50.63 41.6 Diamagnetic
2. [NiLpy] Reddish
Brown
56.04 83.6 Diamagnetic
3. [NiLbipy] Brown 71.98 52.6 3.08
4. [NiLphen] Brown 71.94 41.6 3.09
5. [NiLa–pico] Brown 67.02 93.6 Diamagnetic
6. [NiLb–pico] Brown 69.15 83.6 Diamagnetic
7. [NiL’H2O] Brown 52.08 31.2 Diamagnetic
8. [NiL’py] Brown 67.42 93.6 Diamagnetic
9. [NiL’bipy] Brown 69.31 62.4 3.08
10. [NiL’phen] Brown 83.80 72.8 3.06
11. [NiL’a–pico] Brown 65.79 52.0 Diamagnetic
12. [NiL’b–pico] Brown 67.98 62.4 Diamagnetic
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4.3 SPECTRAL DATA OF SYNTHESIZED COMPLEXES AND
ADDUCTS :
4.3.1 Analytical Data (Fig.No.4.3.1 A→L) :
1. Ni (II) Complex of L :
Anal. calcd. for C9H10N3O2SClNi . ESI–MS m/z, ion 319.01
M+, Ni, 18.43 %; C, 33.95 %; H, 3.17 %; N, 13.20 %; S, 10.07 %. Found: ESI–
MS, m/z, ion 319.79; Ni, 18.01 %; C, 34.02 %; H, 3.44 %; N, 13.25 %; S,
10.33 %.
2. Ni (II) Lpy adduct:
Anal. calcd. for C14H13N4OSClNi. ESI–MS m/z, ion 366.33,
M+, Ni, 16.06 %; C, 46.00 %; H, 3.59 %; N, 11.50 %; S, 8.77 %. Found: ESI–
MS, m/z, ion 366.96, M+, Ni, 15.69 %; C, 46.76 %; H, 3.31 %; N, 11.02 %; S,
8.33 %.
3. Ni (II) Lbipy adduct:
Anal. calcd. for C19H16N3OSClNi. ESI–MS m/z, ion 456.55,
M+, Ni, 12.85 %; C, 49.98 %; H, 3.53 %; N, 15.34 %; S, 7.02 %. Found: ESI–
MS, m/z, ion 457.00, M+, Ni, 12.78 %; C, 49.08 %; H, 3.10 %; N, 15.05 %; S,
8.33 %.
4. Ni (II) Lphen adduct:
Anal. calcd. for C21H16N5OSClNi. ESI–MS m/z, ion 481.51,
M+, Ni, 12.21 %; C, 52.48 %; H, 3.36 %; N, 14.57 %; S, 6.67 %. Found: ESI–
MS, m/z, ion 481.80, Ni, 12.20 %; C, 52.11 %; H, 3.12 %; N, 14.74 %; S,
6.34 %.
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5. Ni (II) La–pico adduct:
Anal. calcd. for C15H15N4OSClNi. ESI–MS m/z, ion 394.47,
M+, Ni, 14.91; C, 45.78 %; H, 3.84 %; N, 14.24 %; S, 8.15 %. Found: ESI–MS,
m/z, ion 395.00, M+, Ni, 15.10 %; C, 45.52 %; H, 3.37 %; N, 14.54 %; S,
8.71 %.
6. Ni (II) Lb–pico adduct :
Anal. calcd. for C15H15N4OSClNi. ESI–MS m/z, ion 394.47,
M+, Ni, 14.92 %; C, 45.78 %; H, 3.84 %; N, 14.24 %; S, 8.15 %. Found: ESI–
MS, m/z, ion 394.64, M+, Ni, 15.11 %; C, 45.52 %; H, 3.62 %; N, 14.54 %; S,
8.37 %.
7. Ni (II) Complex of L’ :
Anal. calcd. for C10H12N3O2SClNi. ESI–MS m/z, ion 333.09,
M+, Ni, 17.65 %; C, 36.13 %; H, 3.64 %; N, 12.64 %; S, 9.64 %. Found: ESI–
MS, m/z, ion 333.54, M+, Ni, 17.43 %; C, 36.40 %; H, 3.87 %; N, 12.85 %; S,
9.98 %.
8. Ni (II)L’py adduct :
Anal. calcd. for C15H15N4OSClNi. ESI–MS m/z, ion 394.47,
M+, Ni, 14.91 %; C, 45.78 %; H, 3.84 %; N, 14.24 %; S, 8.15 %. Found: ESI–
MS, m/z, ion 395.00, M+, Ni, 14.53 %; C, 45.13 %; H, 3.41 %; N, 14.77 %; S,
8.47 %.
9. Ni (II) L’bipy adduct:
Anal. calcd. for C20H18N5OSClNi. ESI–MS m/z, ion 470.58,
M+, Ni, 12.47 %; C, 51.04 %; H, 3.86 %; N, 14.88 %; S, 6.81 %. Found: ESI–
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MS, m/z, ion 471.65, M+, Ni, 12.78 %; C, 51.32 %; H, 3.52 %; N, 14.64 %; S,
7.12 %.
10. Ni (II) L’phen adduct :
Anal. calcd. for C22H18N3OSClNi. ESI–MS m/z, ion 494.60,
M+, Ni, 11.86 %; C, 53.12 %; H, 3.67 %; N, 14.16 %; S, 6.48 %. Found: ESI–
MS, m/z, ion 495.00, M+, Ni, 11.62 %; C, 53.64 %; H, 3.97 %; N, 14.47 %; S,
6.05 %.
11. Ni (II) L’a–pico adduct :
Anal. calcd. for C16H17N4O4SClNi. ESI–MS m/z, ion 406.54,
M+, Ni, 14.47 %; C, 47.39 %; H, 3.73 %; N, 13.82 %; S, 7.91 %. Found : ESI–
MS, m/z, ion 406.05, M+, Ni, 14.11 %; C, 47.12 %; H, 3.32 %; N, 13.51 %; S,
7.32 %.
12. Ni (II) L’b–pico adduct:
Anal. calcd. for C16H17N4O4SCl Ni . ESI–MS m/z, ion 406.54,
M+, Ni, 14.47 %; C, 47.39 %; H, 3.73 %; N, 13.82 %; S, 7.91 %. Found: ESI–
Ms, M/z, ion 406.05, M+, Ni, 14.53 %; C, 46.99 %; H, 3.32 %; N, 13.67 %; S,
8.05 %.
4.3.2 Infrared Spectra :
The significant IR bands of Ni (II) complexes are :
1. NiLH2O : n (C = N) 1603; n (C = N – N = C) 1555, n (C–S) 750, 1304;
n (N–N) 1136; n (M–N) 423; n (M–O) 518; n (M–S) 312; n (C–O) 1226.
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2. NiLpy : n (C = N) 1598; n (C = N – N = C) 1555, n (C–S) 687, 1297;
n (N–N) 1072; n (M–N) Base 282; n (M–N) 425; n (M–O) 516; n (M–S)
311; n (C–O) 1229; Bands due to HB 619.
3. NiLbipy : n (C = N) 1597; n (C = N – N = C) 1545, n (C–S) 682, 1301;
n (N–N) 1110; n (M–N) Base 269; n (M–N) 425; n (M–O) 514; n (M–S)
324; n (C–O) 1226; Bands due to HB 1404 , 1013.
4. NiLphen : n (C = N) 1618; n (C = N – N = C) 1545, n (C–S) 685, 1301;
n (N–N) 1135; n (M–N) Base 284; n (M–N) 425; n (M–O) 511; n (M–S)
316; n (C–O) 1227; Bands due to HB 1466, 470, 613.
5. NiLa–pico : n (C = N) 1609; n (C = N – N = C) 1528, n (C–S) 686,
1311; n (N–N) 1103; n (M–N) Base 278; n (M–N) 419; n (M–O) 500;
n (M–S) 300; n (C–O) 1238; Bands due to HB 1405, 762, 469.
6. NiLb–pico : n (C = N) 1589; n (C = N – N = C) 1545, n (C–S) 674,
1304; n (N–N) 1120; n (M–N) Base 278; n (M–N) 420; n (M–O) 507;
n (M–S) 309; n (C–O) 1228; Bands due to HB, 674, 420.
7. NiL’H2O : n (C = N) 1696; n (C = N – N = C) 1577, n (C–S) 671, 1276;
n (N–N) 1113; n (M–N) 423; n (M–O) 509; n (M–S) 309; n (C–O) 1235.
8. NiL’py : n (C = N) 1577; n (C = N – N = C) 1555, n (C–S) 665, 1296;
n (N–N) 1176; n (M–N) Base 263; n (M–N) 423; n (M–O) 509; n (M–S)
301; n (C–O) 1250; Bands due to HB 1296.
9. NiL’bipy : n (C = N) 1685; n (C = N – N = C) 1560, n (C–S) 665, 1309;
n (N–N) 1111; n (M–N) 269; n (M–N) 425; n (M–O) 514; n (M–S) 313;
n (C–O) 1219; Bands due to HB 1404, 763, 665.
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10. NiL’phen : n (C = N) 1590; n (C = N – N = C) 1579, n (C–S) 728, 1297;
n (N–N) 1107; n (M–N) Base 278; n (M–N) 414; n (M–O) 518; n (M–S)
309; n (C–O) 1227; Bands due to HB 1460, 665.
11. NiL’a–pico : n (C = N) 1590; n (C = N – N = C) 1530, n (C–S) 687,
1325; n (N–N) 1062; n (M–N) Base 288; n (M–N) 469; n (M–O) 521;
n (M–S) 311; n (C–O) 1234; Bands due to HB 618, 468.
12. NiL’b–pico : n (C = N) 1590; n (C = N – N = C) 1545, n (C–S) 688,
1319; n (N–N) 1125; n (M–N) Base 280; n (M–N) 432; n (M–O) 515;
n (M–S) 314; n (C–O) 1238.
4.3.3 Electronic Spectra (Fig.No.4.3.3 A→F)
The electronic spectral data in cm-1 of complexes in solution
are listed in Table No.4.3.3
Table No.4.3.3
Complex State d–d L → M n → p* p → p*
NiLH2O DMF 17,367 23,810 32,051 36,232
NiLpy DMF 17,094 26,247 27,548 38,023
NiLbipy DMF 17,543 23,810
27,778
30,030 34,014
NiLphen DMF 16,502 23,641
25,840
32,052 36,232
NiLa–pico DMF 16,502 23,364 30,960 38,911
NiLb–pico DMF 17,094 23,474
25,042
31,746 36,765
NiL’H2O DMF 16,807 23,697,
26,667
30,769 40,000
NiL’py DMF 16,807 24,691 32,787 40,161
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NiL’bipy DMF 17,007 24,096,
27,933
28,986,
32,788
39,682
NiL’phen DMF 17,123 23,529 30769 40,323
NiL’a–pico DMF 16,807 23,810 32,787 40,160
NiL’b–pico DMF 16,863 23,697 32,258 39,841
4.3.4 Differential Scanning Calorimetry (Fig.No.4.3.4 A,B)
The thermal stability, melting, crystallisation, decomposition,
desolvation, sublimation and glass transition temperature of complexes can
be studied by carrying out differential scanning calorimetry (DSC). This
technique also detects any reaction or transformation involving absorption
or release of heat. DSC thermograms gave thermal characteristic data,
melting point corresponding to endothermic peak and decomposition
temperature (exothermic peak). The results are summarised as –
NiLH2O : Endothermic; onset temperature 170.51 °C; peak, 171.81 °C,; End
set temperature, 175.75 °C, DH, – 71.57 J g–1; Tg, 248.75 °C, Exothermic;
onset temperature, 292.5 °C; Peak, 295.0 °C; End set temperature; 310 °C.
NiL’H2O : Endothermic; onset temperature 166.25 °C, peak, 175.0 °C; End
set temperature, 187.5 °C, Tg, 275 °C, Exothermic; onset temperature,
323.87 °C; Peak, 326.46 °C; End set temperature; 310 °C, DH, – 130.84 Jg–1.
4.3.5 Thermogravimetric Analysis (TGA) (Fig.No.4.3.4 A, B)
The TGA curves of NiLH2O and NiL’H2O complexes were
carried out within a temperature range 38 °C to 800 °C.
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NiLH2O : First step, 117.86 °C, mass loss %, 5.51; Second step, 225 °C; mass
loss %, 17.52.; Third step, 357.14 °C; mass loss %, 54.00; Residue, 732.14 °C;
% of NiO, 24.01 (calc. NiO % = 23.46).
NiL’H2O : First step, 125.0 °C, mass loss %, 5.02; Second step, 200 °C; mass
loss %, 7.52.; Third step, 378.0 °C; mass loss %, 56.5, Residue, 800.0 °C; % of
NiO, 23.02 (calc. NiO % = 22.47).
4.4 RESULTS AND DISCUSSION:
Elemental analyses for M:L, 1:1 complexes matched with
[NiLH2O] formula for both L and L’ ligands. Elemental analysis data are
consistent with 1:1:1 ratio of metal ion; thiosemicarbazone; heterocyclic
base for all complexes prepared. The complexes are insoluble in most of
common polar and non–polar solvents. They are soluble in DMF and
therefore conductivity measurements were made in DMF. All the
complexes showed non–electrolyte nature [119]. The most important
bands in the infrared spectra of the synthesized Ni (II) complexes of
thiosemicarbazones are well in agreement with their tentative assignments.
The position of these bands are helpful to detect the bonding sites of all
ligand molecules interacted with metal. The coordination of azomethine
nitrogen shifts n(7C = 1N) to lower wavenumbers by 15 to 25 cm–1. The
band in spectra of uncomplxed thiosemicarbazones at 1624 and 1638 cm–1
are found to shift to lower wavenumbers in spectra of complex. The n(NN)
shifting to higher wavenumber in spectra of complexes than that of
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thiosemicarbazones confirm the coordination of azomethine nitrogen [147].
The presence of new band at 400 – 470 cm–1 assignable to n(Ni – N) in the
complexes, confirms the coordination of azomethine nitrogen. There is a
loss of – 2NH proton on coordination via thiolate sulphur [148]. Decrease
in frequency (10–90 cm–1) of the n(C = S) bands found at 758, 1374 in L and
795, 1358 cm–1 in L’ and the presence of new band in the 300–325 cm–1
range assignable to n(NiS), confirm the coordination through sulphur. The
phenolic oxygen occupies the third coordination on the loss of OH proton.
This causes shifting of n(CO) to lower wavenumbers by 50–60 cm–1 from
1281 and 1288 cm–1 in the spectra of L and L’ respectively. The band at
500–521 cm–1 is assignable to nNiO. The coordination of heterocyclic
nitrogen atom (s) is confirmed by the presence of n NiN band in the range
260–285 cm–1. The characteristic bands of coordinated heterocyclic bases
are also observed in IR spectra of all the adducts.
The room temperature magnetic susceptibility of the
complexes showed that complexes No. 1, 2, 5, 6, 7, 8, 11, and 12 are
diamagnetic. Five coordinate high spin complexes have magnetic
moments in the range 3.20 – 3.40 B.M. [149]. The observed values of µeff
for complexes 3, 4, 9, 10 are slightly lower than those calculated for five
coordinate trigonal bipyramidal configuration [150]. Lower µeff values for
Ni (II) complexes [151] arise from quenching of the orbital contribution to
the magnetic moment due to distortion of D3h symmetry or due to strong
in plane p–bonding [152, 153].
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Typical planer Ni (II) spectra show a strong visible band in
the 15,000 – 25,000 cm–1 range and in many cases a second strong band
between 23,000 and 30,000 cm–1. These are referred to as n2 and n3 bands.
Lower energy n1 band has been observed in planer complexes containing
S–ligands [154]. The planer complexes can be readily distinguished from
octahedral and tetrahedral complexes by absence of transitions below
10,000 cm–1. The electronic spectra show band in 36,000-41,000 cm-1 range
and 27,000 – 33,000 cm-1 range, these can be assigned to p – p* (aromatic
ring) and n – p* (thiosemicarbazone moiety) transitions respectively. The
broad bands in 27548 – 32788 range are assigned for n – p* transitions [155].
The shift of p – p* bands to the longer wavelength region is the result of the
C = S bond being weakened and conjugation system being enhanced after
the formation of the complex [156]. NiLpy, NiLH2O, NiLa–pico, NiLb–pico
(L = L or L’) show shoulder bands at 16000 – 17094 cm–1 range. These d–d
spectral transitions are assigned to 'A1g → 'Eg and 'A1g → 'A2g [157]. The
d–d bands appearing as weak shoulders centred around 17000 cm–1 region
are typically of square planer Ni (II) complexes [158]. The presence of
intense p – p* and n – p* transitions cause the lower energy d–d bands and
LMCT bands to appear as weak shoulders. The bands at 23000 – 27933
cm–1 range correspond to L → M. It is associated with 'A1g → 'Eg
transition. No band below 10000 cm–1 confirms the planer structure of
these complexes. This is because of large crystal field splitting in square
planer complex the energy separation between dx²–y² and lower orbital is
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greater than 10000 cm–1 [53]. NiLa–pico and NiLb–pico (L = L or L’) show
broad band at 23000 – 26050 cm–1 range. This band may be due to
tetrahedral complex in addition to square planer complexes. This indicates
the probability of tetrahedral º square planer equilibrium in the
complexes. The electronic spectra of NiLbipy and NiLphen do not
resemble the spectra of five coordinate [153, 159] but resemble to pseudo –
octahedral Ni (II) complexes [53, 160].
In DSC thermograms of the complexes, a sharp endothermic
process corresponds to melting points and exothermic corresponds to
decomposition of the complex.
Two sharp peaks were observed in DSC thermogram of
NiLH2O. One peak corresponds to endothermic and another for
exothermic (Fig. 4.3.4.1, 4.3.4.2). The sharp endothermic peak at 171.81 °C
corresponds to the melting point of the complex. The exothermic peak at
295.0 °C corresponds to the decomposition of the complex.
In case of NiL’H2O also two sharp peaks were observed in
DSC thermogram, one peak corresponds to endothermic and another for
exothermic (Fig. 4.3.4.3, 4.3.4.4). The sharp endothermic peak at 175.0 °C
corresponds to melting point of the complex. The exothermic peak at
326.46 °C corresponds to the decomposition of the complex.
The TGA data of NiLH2O complex indicated that the
decomposition of the complex proceed in several steps. In between the
temperature 30 °C – 100 °C molecules of water of hydration were lost. One
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coordinated water molecule was lost between the temperature 100 °C and
117.86 °C. There are two breaks in curves due to decomposition of organic
ligand at 225 °C and 357.14 °C. The decomposition was complete and NiO
was formed at 732.14 °C.
The TGA data of NiL’H2O complex indicated that the
hydration of water molecules was lost in between temperature 30 °C –
100 °C. One coordinated water molecule was lost between the temperature
100 °C – 125 °C. There are two breaks in curves at 200 °C and 378.57 °C
due to evaporation of organic ligand. NiO was formed and decomposition
completed at 800 °C.
All spectral characterisations confirm the NiLH2O, NiLpy, Ni
L a/b pico (L = L or L’) complexes have square planer and for NiL bipy,
NiL phen complexes five coordinate pseudo–octahedral geometry with
thiosemicarbazones acting as ONS tridentate ligand and N–atom (s) of
heterocyclic base occupying the fourth (and fifth) coordination site about
the Ni (II) atom. The TGA curves indicated coordinated water molecule in
NiLH2O and NiL’H2O.
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Expected structures :
(Where B=H2O, pyridine, α/β-picoline)
N
N
Cl
O
NN NH2
SNi
CH3
N
N
Cl
O
NN NH
SNi
CH3CH3
Cl
O
NN NH2
SNi
N
N
CH3
Cl
O
NN NH
SNi
N
N
CH3CH3
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105
106
107
108
109
110
111
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Fig. 4.3.3.A : UV-visible spectrum of NiLH2O in DMF
Fig. 4.3.3.B : UV-visible spectrum of NiLPy in DMF
Fig. 4.3.3.C : UV-visible spectrum of NiLbipy in DMF
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Fig. 4.3.3.D : UV-visible spectrum of NiLphen in DMF
Fig. 4.3.3.E : UV-visible spectrum of NiLa-pico in DMF
Fig. 4.3.3.F : UV-visible spectrum of NiLb-pico in DMF
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