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Molecular Spectroscopic studies of
metal(II) [Mn(II), Co(II) and Ni(II)]
halogen complexes with methylanilines
Part I
M. KUMRU, Fatih University, Faculty of Arts and
Sciences, Department of Physics, 34500 Büyükçekmece,
Istanbul, TURKEY
K. GOLCUK, Dept. of Chem., Univ. of Michigan, 930 N. University,
Ann Arbor, MI 48109-1055, USA
A. ALTUN, Max Planck Institute, Kaiser-Wilhelm-Platz 1, 45470
Mülheim an der Ruhr, GERMANY
Aniline and its derivatives are widely used for producing polyurethanes, rubbers, pesticides
and dyes and also found in the environment [1].
Recently, their toxicity effects to Daphnia magna were also studied [2].
Hence, understanding of their molecular properties and the reactions they experience is very
important. Besides, their metal(II)halide complexes have been interested for decades [3-9].
As a continuation of our previous works [10-16], we report thermogravimetric (TG) analysis,
magnetic moments, electronic spectra and vibrational spectra of the pMA metal(II) [Mn(II),
Co(II) or Ni(II)] bromide complexes in the present study.
A detailed vibrational band analysis of each metal complex is also given.
The spectroscopic investigations are used to obtain the local structure around each metal
atoms.
Our Related Some Publications :
M. Kumru, A. Aypar, Spectrochim. Acta, Vol. 4 7A, No. 12, pp.1789, 1991
M. Kumru, A. Aypar, Doğa- Tr. J. Physics, 16 (1992) 377 - 382.
M. Kumru, H. Yuksel, A. Aypar, Doğa- Tr. J. Physics, 17(1993)793-799.
M. Kumru, Fourier Transform Infrared Spectra and Assignment of Vibrations of Hg(3C7H9N)2Cl2 and Hg(3-C7H9N)2Cl2, DOĞA, Turkish Journal of Physics, 19(1995)662-668.
…………..
A. Altun, K. Golcuk, M. Kumru, " Vibrational and thermal studies of metal(II) [Ni(II), Zn(II) and
Cd(II)] iodide m-methylaniline complexes ", Vibrational Spectroscopy, 31(2003) 215-225
A. Altun, K. Golcuk, M. Kumru, " Theoretical and experimental studies of the vibrational spectra of
m-methylaniline", J. Mol. Struct. ( THEOCHEM ), 625(2003)17-24
A. Altun, K. Golcuk, M. Kumru, "Structure and vibrational spectra of p-methylaniline: HartreeFock, MP2 and density functional theory studies ", J. Mol. Struct. (THEOCHEM), 637(2003)155-169
A. Altun, K. Golcuk, M. Kumru, "Vibrational and thermal studies of p-methylaniline complexes with
Ni(II), Zn(II) and Cd(II) iodides", Vibrational Spectroscopy, 33 / 1-2 (2003) 63 –74
K. Golcuk, A. Altun, M. Kumru, "Thermal studies and vibrational analyses of m-methylaniline
complexes of Zn(II), Cd(II) and Hg (II) bromides", Spectrochimica Acta, 59A (2003) 1841-1847
K. Golcuk, A. Altun, M. Kumru, " Spectroscopic and thermal studies of Mn(II), Co(II) and Ni(II)
bromide m-methylaniline complexes ", Journal of Molecular Structure, 657 (2003) 385-393
K. Golcuk, A. Altun, S. Guner, M. Kumru and B. Aktas, "Thermal, Vibrational and ESR studies of
Cu(II) bromide bis(p-methylaniline) and bis(m-methylaniline) complexes" Spectrochimica Acta Part
A, 60 (2004) 303-309
K. Golcuk, A. Altun, M. Kumru, M. Somer " Vibrational and thermal studies of [MBr2(pmethylaniline)2] (M:Zn+2, Cd+2 and Hg+2) complexes", Vibrational Spectroscopy xxx(2005)xxx-xxx
BENZENAMİN-3-METHYL
m-toluidine
3-amino toluene
m-amino toluene
3-methyl aniline
m-methylaniline(mMA)
........
BENZENAMİN-4-METHYL
p-toluidine
4-amino toluene
p-amino toluene
4-methyl aniline
p-methylaniline (pMA)
........
molecular structures
H
N
C
H
H
C
m-methylaniline (mMA)
p-methylaniline (pMA)
Experimental
The ligand (L: pMA) and MBr2 (M: Mn, Co and Ni)
were used as received from Fluka and Aldrich Co.
The polycrystalline complexes were prepared using
the method given in our previous studies[10-16].
Composition and purity (C, H, N, and M) were
determined by microanalysis.
Microanalysis data, listed in Table 1, suggest that the
complexes have 1:2 (MBr2:L) stoichiometry.
Therefore, [MBr2(pMA)2] form is obtained for all
the complexes.
Table 1. Analyses (%) of the metal complexes
Found (Calculated) %
Compound
Colour
M
C
N
H
[MnBr2(mMA)2]
Pale pink
12.88 (12.80)
38.90 (39.19)
6.49 (6.53)
4.18 (4.23)
[MnBr2(pMA)2]
Pale pink
12.93 (12.80)
38.72 (39.19)
6.58 (6.53)
4.11 (4.23)
[CoBr2(mMA)2]
Blue
13.49 (13.61)
38.69 (38.83)
6.45 (6.47)
4.26 (4.19)
[CoBr2(pMA)2]
Blue
13.53 (13,61)
38.90 (38.83)
6.49 (6,47)
4.22 (4.19)
[NiBr2(mMA)2]
Light yellow
13.23 (13,56)
39.29 (38.85)
6.89 (6.47)
4.15 (4.19)
[NiBr2(pMA)2]
Light yellow
13.40 (13,56)
39.60 (38.85)
6.61 (6.47)
4.17 (4.19)
Electronic spectra in EtOH were recorded on a Perkin
Elmer Lambda 9 UV-VIS-NIR spectrometer in the range
190–1100 nm.
Measurements of magnetic moments at room
temperature were made using the Evans method with a
Sherwood Sci. magnetic balance. *The molar
susceptibilities were corrected for the diamagnetism of
the constituent atoms using Pascal’s constants.
Thermal analyses were made on a Mettler Toledo TG50
thermobalance under N2 flow (flow rate, 30 cm3/min).
*The samples were heated in an Al2O3 crucible at a rate
of 10C/min.
The 4000-400 cm-1 region FT-IR spectra of the
complexes were recorded as KBr discs using a Perkin
Elmer Paragon 1000 FT-IR spectrometer. *500-200 cm-1
region IR spectra of the complexes were recorded on a
Mattson Instruments 2030 Galaxy Series as polyethylene
discs at room temperature.
The FT-Raman spectra were recorded on a Bruker RFS
100/S FT-Raman Spectrometer in the range 3600 – 70 cm1. *The 1064 nm line, provided by a 1.5 W Nd:YaG aircooled laser, was used as excitation line. *A liquid
nitrogen cooled Ge detector was used. *The FT-Raman
spectra of pMA and its complexes are shown together in
Fig. 2.
Vibrational Spectroscopy
The only coordination site for the ligand pMA is the
nitrogen atom of the amine group. *Hence, we pay
attention to –NH2 group vibrations upon complexation.
*The detailed structural and vibrational studies based
on ab initio and DFT for free pMA were already
discussed in our previous study [11]. *Considering that
pMA belongs to Cs symmetry point group, the
symmetry species (25A + 20A) of the observed pMA
vibrations are given in Table 2 and Table 3. *All
observed vibrational bands in the spectra of metal
complexes and their assignments are also given in
Table 2 and 3. *The FT-IR spectra of pMA and its
complexes are given together in Fig. 1.
As an evidence of complex formation between metal(II)bromide
and pMA, it is observed that some modes originating from pMA
vibrations show substantial shifts in the spectra of complexes.
The NH2 group vibrational frequencies of pMA are much affected
by complexation. *This suggests that coordination occur via lone
pair electrons of nitrogen. *The hybridization type around nitrogen
changes via electron donation from nitrogen orbitals to the metal
atom on complex formation [12-16]. *Hence, the N-H bond
strength weakens upon coordination and the NH asymmetric and
symmetric stretching bands shift toward lower wavenumbers (see
Table 1). *The change in HNH angle with coordination decreases
scissoring force constant [12-16]. *As a result, the scissoring
frequency of the amino group downshifts up to 52 cm-1 upon
coordination.
•We have assigned the bands observed at 1267 cm–1 (IR) and
1271 cm–1 (Raman) to the CN stretching for free pMA [11].
*The C-N stretching band in the complexes has two
components (asymmetric and symmetric stretching of C-N
bonds), each of them is observed at lower frequencies
compared with the free pMA. *Vibrations of this mode occur
at lower frequencies and have two components (asymmetric
and symmetric stretching of C-N bonds) in the spectra of
complexes, in line with the decrease in the C=N double bond
character.
In m-methylaniline (mMA) and p-methylaniline (pMA),
the nitrogen atom is out of the ring plane for about 2-3
and the angle between the ring and amino planes reaches
to 40 [10,11,17]. *High-level ab initio and DFT
calculations, which confirm non-planar geometry of
pMA, show that amino group rocking, wagging and
twisting vibrations are expected around 1060 cm-1, 600
cm-1 and 250 cm-1, respectively [11,17]. *Hence, we
assign the IR band of the free pMA at 1074 cm-1 as the
rocking mode. *We could not determine the frequency of
the wagging and twisting modes from the experimental
IR and Raman spectra of the free pMA due to the
broadness or low intensity of the bands.
In the complexes, amino group rocking, wagging and twisting
vibrations shift towards upper frequencies. *The rocking vibration
has been observed in the complexes around 1080-1060 cm-1. *The
wagging mode shifts upon coordination to 1065-1040 cm-1 region
and appears as a strong and coordination sensitive band [18].
*A study of normal coordinate analysis on aniline was reported and
the band at 216 cm-1 in IR spectrum of aniline was assigned to
NH2 twisting mode. *On the other hand, this band was found at
605 cm-1 in aniline-Cd complex [9]. *Therefore, we assign the
635-566 cm-1 region bands of the complexes, as the NH2 twisting
vibrations, which are not observed in the spectra of free pMA.
*The explicit metal-sensitivity can be explained directly by
mechanical coupling of this mode with M–N vibrations [14-16].
The metal-ligand bands are helpful for determining the local
structure around metal ions. *It is considered that the metal-ligand
vibrations occur below 500 cm–1 [3-16]. *Assignments of the
(M-N) and (M-Br) vibrations, listed in Table 3, have been given
carefully by considering the internal modes of mMA and
comparing with literature reports [3-16]. *The 500-200 cm–1
region IR spectra of the complexes are shown together in Fig 3.
For the Co (II) complex, strong and medium IR bands at 420 cm–1
and 394 cm–1 were assigned to (Co-N) stretching vibrations. *We
observed terminal Co-Br bond stretching, i.e. (Co-Br)t bands at
217 cm–1 and 208 cm–1 [14]. *In Co(II) complex, the metal ion is
involved in a tetrahedral N2CoBr2 skeleton. *Assuming C2v
symmetry for this complex, both the asymmetric and symmetric
CoBr2 and CoN2 stretching vibrations are IR active [19]. *Then,
the (Co-Br)t and (Co-N) stretching vibrations can be described
with A1+B1 and A1+B2 representations, respectively. *Thus, the
metal-ligand vibrational bands are consistent with previously
reported tetrahedral Co(II) complexes [3-6,14,19].
The stretching vibrations of the bridging M-Br-M bonds, i.e. (MBr)b, should appear below 200 cm–1 [14,20]. *In Raman spectrum
of Mn(II) complex (see Fig.2(c)), we could not observe (Mn-Br)b,
bands due to broad strong Raman band around 100 cm–1 which is
ascribed as the lattice mode of the solid complexes [21] and couple
with torsional mode of CH3.
In FT-Raman spectrum of Ni(II) complex (see Fig.3(d)), the 155
cm–1 and 136 cm–1 bands are due to the stretching bands of
bridging Ni-Br-Ni bonds, i.e. (Ni-Br)b. *Hence, the appearance of
the (Ni-Br)b vibrations indicates a polymeric octahedral structure
around metal ions with exclusively bridging bromides for
[NiBr2(pMA)2] complex. *On the other hand, the nonappearance of
(Mn-Br)t bands can be concluded that the local environment of
Mn ion consists of polymeric octahedral structure, as also proposed
for [MnBr2(mMA)2] complex [14]. ****As a result, each of Mn and
Ni ions is surrounded by four bromine atoms and two nitrogen
atoms of the ligands, having a polymeric octahedral structure
[3,5,8,14,19].
The coordination number effect on metal-ligand
vibration frequencies is known to be a substantial one
[4,14]. *Substitution of Ni(II) by Co(II) causes to a
decrease in (M-N). Substitution of Co(II) by Mn(II) is
expected to lead to an increase in (M-N). *This result
arises from the bonding capacity of the metal ion being
distributed over more bands with consequently lower
metal-ligand force constants [4,14]. *If the coordination
number remains unchanged, (M-N) bands follow the
sequence Mn<Ni. *The difference between the
frequencies of corresponding (M-N) bands in each MnNi pair might be ascribed to the fact that the Ni(II)
complex is stabilized by crystal field splitting whereas the
Mn(II) complex is not [14].
Table 2. Infrared and Raman frequencies of pMA and metal comlexes
(pMA)
[MnBr2(pMA)2]
[CoBr2(pMA)2]
IR
IR
Ra
IR
3416 s
3418 w
3293 s
3333 s
3337 w
3238 vs
3220 m
3224 w
3123 m
3056 w
3054 s
3054 vw
3054 s
3020m,
sh
3032 s
3031 m
3030 s
3008 m
3013 s
2912 m
2917 s
2920 m
2916 m
2859 m
2861m
2868 w
2863 m
2737 w
2738 w
2731 vw
1621 vs
1617 s
1573 s
1575 m,sh
1619 s
1621 s
1582
sh
IR
Raman
Sym
metry
Assignments
3311 m
3312 s
A
NH asym
3240 s
3232 vs
A
NH sym
3121 w
3120 w,br
3057 s
3065 vw
3057 vs
A
CH ring
3032 m
3032 w
3038 s,sh
A
CH ring
3012 m
3008 w
3014 s
A
CH ring
2925 m
2924 s
2911 m
2915 vs
A
CH3 sym
2864 vw
2860 w
2857 m
2864 vs
2 x 1458 overton
2722 w
2721 w
2735 w
2 x 1380 overton
1578 vs
1576 w
1569 vs
1612 w,sh
1612 s
1615 s
Raman
3276 s
3244 s
3226 vs
3227 m
3124 m
3054 vw
2 x 1621 overton
3031 m
s,
1581 m
1514 vs
3011 s
1596 s
1616 vs
1595 m
A
NH2 sciss.
A
CC ring
A
CC ring
1518 vs
1519 m
1512 vs
1516 vs
1518 w
A
CC ring
1458 w
1451 w
1455 w
1451 m,br
1449 w
A
CH3 asym
1440 w,br
1430 vw,br
A
CC ring
1380 vw
1441 s
1324 m
Raman
[NiBr2(pMA)2]
1379 m
1379 w
1377 m
A
CH3 sym
1324 m
1327 vw
1326 vw
1327 w
A
CH ring
1295 w
1292vw,
1296 w
1293 w
A
CC
1380 m
1374 w
1380 s
1324 w
1317 m
1281 m
1294 m
(4-MA)
IR
1176 s
[MnBr2(4-MA)2]
[CoBr2(4-MA)2]
[NiBr2(4-MA)2]
Ra
IR
Raman
IR
IR
Raman
Sim
Bant Tanımları
1281 m
1243 vs
1237 m
1238 m
1250 s
1242 s
A
CN
1216 s
1222 s
1215
1235 s
1222 vs
CN
1218 m
1205 m
1204 s
1217 w
1207 w,sh
1207 vs
A
CCH3
1179 m
1160 m
1183 s
1181 m
1180 m
1179 s
A
CH ring
1116 w,sh
1123 w,br
A
CH ring
1062 vs
1070 w,sh
A
NH2 rock.
1120 s
1074 m
Raman
1100 s, sh
1074 m
1070 vs
1080 vs
1065 vs
1065 s
1038
1046 vs
A
NH2 wag.
983 w
998 m
1016
998 s
1000 s
A
CCC ring
953 w
956 w
650 vw
A
CH3; CCH3; CCC
931 w
936 w
844 s
812 vs
720 m
645 s
504 vs
836 m
960 vw,sh
932 vw
837 s
938 s
830 vw
A
CH ring; CCC ring
835 m
830 vs
A
CCC ring; CN
810 m
A
CH ring; CCC ring
A
CH ring; CCC ring
841 s
837 s
812 vs
810 vs
813 s
806 vs
806 vs
809 m
810 vs
739 s
743 w
741 s
739 w
733 s
742 m
A
Breathing
702 s
702 vw
707 m
705 w
705 s
709 vw
A
CCC ring
661 s
660 s
649 s
645 m
647 s
650 vw
A
CCC ring
566 s
556 m
634 s
635 m
607 vs
610 m
A
NH2 twist.
510 vs
521 w
507 s
524 m
523 vs
518 vw
A
CCC ring
Table 2. (Continued)
4-MA
[MnBr2(4-MA)2]
[CoBr2(4-MA)2]
[NiBr2(4-MA)2]
IR
Ra
IR
Raman
IR
Raman
IR
Raman
Simetri
Bant Tanımları
470
466 s
466 s
474 s
472 m
472 vs
476 m
476 m
A
CCC ring
406 m
405 m
420 s
421 m
412 m
410 m
(M-N)
361 m
365
394 m
395 w
386 m
386 m
(M-N)
300 s
307s
303 s
299 vs
308 s
315 w
297 s
285 vs
335 m
278 w
260
255 s
217
277 vw
273 m,sh
227 m
234 m
A
CCH3; CCC; CN
A
CN; CCH3
NMN deformation
220
247 s
213 s
(M-Br)t
208 s
211 vs
(M-Br)t
155 vs
(M-Br)b
Key : , stretching; , in-plane deformation; , out-of-plane deformation; s, strong;
vs, very strong; m, medium; w, weak; vw, very weak; sh, shoulder; br, broad.
(a) FTIR and (b) FT-Raman Spectra of pMA
FT-IR spectra of (a) [MnBr2(4-MA)2], (b) [CoBr2(4-MA)2] and
(c) [NiBr2(4-MA)2] complexes
FT- Raman spectra of (a) [MnBr2(3-MA)2]
(b) [NiBr2(3-MA)2] complexes
and
FT-Raman spectra of (a) [MnBr2(4-MA)2]
(b) [NiBr2(4-MA)2] complexes
and
FT-Raman spectra of (a) [CoBr2(4-MA)2] and
[CoBr2(3-MA)2] complexes
(b)
IR spectra of (a) [NiBr2(3-MA)2], (b) [MnBr2(3-MA)2] and (c)
[CoBr2(3-MA)2] complexes in the range of 500–200 cm–1
IR spectra of (a) [NiBr2(4-MA)2], (b) [MnBr2(4-MA)2] and
(c) [CoBr2(4-MA)2] complexes in the range of 500–200 cm–1
Electronic (UV-VIS) Spectroscopy
The electronic spectral data and magnetic moment
values of the complexes are given in Table 4. *The UVvis spectrum of [MnBr2(pMA)2] complex gives only
one band around 23809 cm–1. *This band corresponds
to 6A1g(S) → 4A1g(G), 4Eg(G) spin forbidden d-d
transition. *The spectrum band and the value of
magnetic moment (eff = 5.56 B.M.) are consistent
with those predicted six coordinated polymeric
octahedral Mn(II) complexes [5,14,19]. *The magnetic
moment value of the complex is lower than spin-only
value of a Mn(II) ion, showing Mn-Mn interaction [22].
The electronic absorption spectrum of [CoBr2(pMA)2]
complex shows some overlapping bands at 14837 cm-1,
15625 cm-1, 16007 cm-1 and 16649 cm-1. *The band at
14837 cm-1 arises from spin allowed 4A2(F) → 4T1(P)
electronic transition. *The bands at 15625 cm-1, 16007
cm–1 and 16649 cm–1 are due to spin forbidden
transitions and assignable to 4A2(F) → 2E(G), 4A2(F) →
2T1(G) and 4A2(F) → 2T2(G), respectively, indicating
fine structures due to pseudo-tetrahedral structure.
Magnetic moment value was found as 4.72 B.M. and
consistent with high spin tetrahedral Co(II) complexes
[14,23,24]. *Therefore, the proposed tetrahedral structure
consists of N2CoBr2 coordination sphere.
In the UV-vis spectrum of [NiBr (pMA) ] complex,
two bands were observed at 12820 cm–1 and
23809 cm–1. The absorption band at 12820 cm–1
arises from 3A2g(F) → 3T1g(F) transition, while
the absorption band at 23809 cm–1 corresponds to
3A2g(F)→ 3T1g(P) transition. *The positions of
the d-d transitions indicate that the Ni ion is in a
polymeric octahedral environment with bridging
bromides [5]. *The magnetic moment value (eff
= 3.15 B.M.) of the complex, which shows the
presence of two unpaired electrons, lies in the
region expected for octahedral Ni complexes [3].
2
2
Electronic transitions
Transition
Mulliken
representation
 (nm)
  *
NV
<200
  *
NV
200–500
n  *
NQ
160–260
n  *
NQ
250–600
UV- VIS spectrum of pMA
291 nm de görülen bant n→ *,
237 nm de görülen bant  → *
207 nm de görülen bant ise n→ *
geçişlerine karşılık gelmektedir.
UV- VIS spectrum of mMA
287 nm de görülen bant n→ *,
237 nm de görülen bant  → * ve
203 nm de görülen bant ise n→ *
geçişlerini göstermektedir.
Electronic Transitions of Transition metal complexes
Geçiş metal komplekslerinin soğurmaları genellikle dolu olmayan d
orbitallerine geçişlerden veya yük transferi geçişlerinden kaynaklanmaktadır.
Serbest iyondaki d orbitallerinin (a) oktahedral ve (b) tetrahedral alanda
yarılmalarıyla meydana gelen enerji-seviye diyagramları
UV-VIS spectrum of [MnBr2(4-MA)2]
420 nm de bir soğurma bandı
gözlenmiştir. Bu soğurma, elektronun
6A1g(S) → 4T2g(G) enerji seviyeleri
arasındaki spin yasaklı geçişinden
kaynaklanmaktadır.
UV-VIS spectrum of [MnBr2(3-MA)2]
412 nm görülen band 6A1g(S) → 4A1g(G),
spin yasaklı geçişine ve 546 nm görülen
band ise 6A1g(S) → 4T1g(G) spin yasaklı
geçişine karşılık gelmektedir.
UV-VIS spectra of (a) [CoBr2(4-MA)2] and (b) [CoBr2(3-MA)2]
complexes.
670 nm gözlenen bantlar 4A2(F) → 4T1(P) geçişine karşılık gelmektedir.
640 nm, 622 nm ve 590 nm de görülen omuzlar Co(II) metali etrafında meydana
gelen pseudo-tetrahedral (tetrahedralimsi) yapının bir sonucudur. Ayrıca ortaya
çıkan bu ince yapılar spin yasaklı geçişlerin de bir sonucu olup; 4A2(F) temel
seviyesinden 2E(G), 2T1(G) ve 2T2(G) seviyelerine olan geçişleri göstermektedir.
UV-VIS spectra of (a) [NiBr2(3-MA)2] and (b) [NiBr2(4-MA)2] complexes
780 nm de gözlenen band 3A2g(F) → 3T1g(F) elektronik geçişini,
420 nm deki bant ise 3A2g(F) → 3T1g(P) elektronik geçişini gösterir.
Electronic absorption spectrum results of complexes
Complexes
max (nm)
[MnBr2(4-MA)2]
420
6A (S)
1g
→ 4A1g(G)
[MnBr2(3-MA)2]
412
6A (S)
1g
→ 4A1g(G)
546
6A (S)
1g
→ 4T1g(G)
340
CT
590
4A (F)
2
→ 2T2(G)
622
4A (F)
2
→ 2T1(G)
640
4A (F)
2
→ 2E(G)
674
4A (F)
2
→ 4T1(P)
340
CT
590
4A (F)
2
→ 2T2(G)
620
4A (F)
2
→ 2T1(G)
640
4A (F)
2
→ 2E(G)
670
4A (F)
2
→ 4T1(P)
420
3A (F)
2g
→ 3T1g(F)
780
3A (F)→ 3T (P)
2g
1g
420
3A (F)
2g
780
3A (F)→ 3T (P)
2g
1g
[CoBr2(4-MA)2]
[CoBr2(3-MA)2]
[NiBr2(4-MA)2]
[NiBr2(3-MA)2]
Electronic Transitions
→ 3T1g(F)
Thermal analyses
Thermal decomposition data of the metal complexes are
listed in Table 5. *As an example, TG and DTG traces for
[MnBr2(pMA)2] complex are shown in Fig. 4. *In the
TG-DTG curves of Mn(II) complex no weight changes are
observed until 103C, where an initial weight loss is
observed. In the temperatures between 226C and 290C,
the rest of the pMA is removed immediately from the
complex, leaving the intermediate MnBr2. *The metal salt
starts to decompose at 295C. *The residual weight is in
good agreement with the value required for MnO.
The Co(II) and Ni(II) complexes decompose in a two-step
mass loss reaction. *The first step (140-273C range) for
the Co(II) complex corresponds to the loss of 2 moles of
pMA. *The second decomposition stage registered
between 275-750C matches the decomposition of CoBr2
finally to CoO. *The Ni(II) complex loses 2 moles of pMA
in 120-273C temperature. *The observed weight losses
for the decomposition processes in each of the compounds
compare favorably with the theoretical values listed in
Table 5.
Magnetic succeptibility results of complexes
Experimental
Parameters
[MnBr2(3MA)2]
[MnBr2(4MA)2]
[CoBr2 (3MA)2]
[CoBr2 (4MA) 2]
[NiBr2(3MA)2]
[NiBr2(4MA)2]
[CuBr2(3MA)2]
[CuBr2(4MA)2]
m (g)
0,0575
0,0985
0,0850
0,0788
0,1079
0,1390
0,0705
0,0601
L (cm)
2
2,5
2,3
2,5
2,4
2,5
2,3
2,2
Rd
942
1213
780
659
408
515
34
29
Rb
-32
-32
-33
-33
-31
-32
-33
-33
Mw (gmol–1)
429,05
429,05
433,05
433,05
432,81
432,81
437,66
437,66
cg x 10-6
32,1843
30,0431
20,8988
20,8566
9,2763
9,0297
1,9630
2,1570
cm x 10-3
13,8087
12,8899
9,0502
9,0319
4,0149
3,9081
0,8591
0,9443
cd x 10-6
-232,64
-232,64
-232,64
-232,64
-232,64
-232,64
-232,64
-232,64
cA x 10-3
14,0413
12,8901
9,2828
9,2645
4,2475
4,1407
1,0918
1,1769
T (K)
298
298
298
298
298
298
298
298
eff (BM)
5,80
5,56
4,73
4,72
3,20
3,15
1,62
1,68
n
5
5
3
3
2
2
1
1
Spin states
High
spin
High
spin
High
spin
High
spin
Termogravimetrik Analiz Sonuçları
Termal analizler Mettler Toledo TG50 termobalansı
kullanılarak, 35–900C aralığında, 30 cm3/dak. lık akış hızına
sahip N2 dinamik atmosfer gazı altında yapılmıştır.
Toz haldeki numunelerden yaklaşık 10 mg civarında alınarak,
70 l lik standart alüminyum oksit (Al2O3) kaplar içinde
10C/dak. lık ısıtılma oranına sahip termobalansa
yerleştirilmiştir.
Her bir numune için TG eğrilerinin yanında kısmen örtüşmüş
termal ayrışma reaksiyonlarını ortaya çıkarmak ve sonuçları
daha iyi yorumlayabilmek için DTG eğrileri de kaydedilmiştir.
Böylece bu sıcaklıklar arasında numunede meydana gelen
termal ayrışma reaksiyonları ortaya konularak her bir
numunenin termal karakterizasyonu yapılmıştır.
Thermal Speration reactions of Compomplexes
% mass loose
Complexes
Thermal Seperation Reactions
Temperature
Range
(C)
DTG
pics (C)
Experim
ent
al
Theoreti
cal
[MnBr2(4-MA)2]
[MnBr2(4-MA)2] → [MnBr2(4-MA)0,4]
[MnBr2(4-MA)0,4] → MnBr2
MnBr2→MnO
103–226
226–290
295-770
203
270
680
31,00
19,00
34,22
30,00
20,45
37,66
[MnBr2(3-MA)2]
[MnBr2(3-MA)2] → [MnBr2(3-MA)0,4]
[MnBr2(3-MA)0,4] → MnBr2
MnBr2→MnO
115–183
183–310
350–750
178
202
670
29,12
19,83
33,39
26.68
17.78
35.93
[CoBr2(4-MA)2]
[CoBr2(4-MA)2] → CoBr2
CoBr2→CoO
140–273
275-750
240
685
48,83
40,25
49,61
36,86
[CoBr2(3-MA)2]
[CoBr2(3-MA)2] → CoBr2
CoBr2 → Co
97–350
390–700
250
690
49,40
33,29
47.70
36.62
[NiBr2(4-MA)2]
[NiBr2(4-MA)2] → NiBr2
120–273
257
46,65
50,38
[NiBr2(3-MA)2]
[NiBr2(3-MA)2] → NiBr2
NiBr2 → NiO
90–380
400–720
235
685
50,33
33,08
49.31
34.88
[CuBr2(4-MA)2]
[CuBr2(4-MA)2] → [CuBr2(4-MA)]
[CuBr2(4-MA)2] → CuBr2
85–200
200-340
140
250
21,12
25,82
24.48
24.48
[CuBr2(3-MA)2]
[CuBr2(3-MA)2] → CuBr2
50–370
110
46,02
48.97
[ZnBr2(4-MA)2]
[ZnBr2(4-MA)2] → ZnBr2
112–305
222
47,32
48,92
[ZnBr2(3-MA)2]
[ZnBr2(3-MA)2] → ZnBr2
110–310
230
46,56
48,84
[CdBr2(4-MA)2]
[CdBr2(4-MA)2] → [CdBr2(4-MA)]
[CdBr2(4-MA)] → CdBr2
70–175
175–240
170
190
21,78
21,78
21,99
2199
[CdBr2(3-MA)2]
[CdBr2(3-MA)2] → CdBr2
80–200
170
43,29
44,10
[HgBr2(4-MA)2]
[HgBr2(4-MA)2] → [HgBr2(4-MA)]
[HgBr2(4-MA)] → HgBr2
56–118
118–170
107
133
16,38
16,38
18,65
18,65
[HgBr2(3-MA)2]
[HgBr2(3-MA)2] → HgBr2
55–162
150
37,26
37,33
[MnBr2(3-MA)2] için TG-DTG eğrileri
TG-DTG
curvers for
[CoBr2(3-MA)2]
TG-DTG
curves for
[CoBr2(4-MA)2]
TG-DTG curves
for [NiBr2(3MA)2]
TG-DTG curves
for [NiBr2(4MA)2]
TG-DTG curves
for [MnBr2(4MA)2]
TG-DTG curves
for [MnBr2(4MA)2]
TG-DTG curves
for 4-MA
TG-DTG curves
For 3-MA
Conclusion
The
spectroscopic
studies
of
[MnBr2(pMA)2],
[CoBr2(pMA)2] and [NiBr2(pMA)2] complexes show that
metal-ligand coordination occurs via nitrogen atom of the
pMA. *The vibrational spectra reveal the type of the
coordination around each metal ion. *The information
referring to the geometry of the studied complexes is also
obtained from the electronic spectra and from the values of
magnetic moments. *The spectroscopic and magnetic data
suggest that the Co(II) complex has a tetrahedral structure,
with the cobalt ion bonded to two bromide ions and two
nitrogen atoms from two different pMA ligand, while the
Mn(II) and Ni(II) complexes have the metal ions in a
polymeric octahedral environment with bridging bromides.
References
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Tetrahedral Co(II) kompleksleri metal
iyonu etrafında lokal olarak C2v
simetrisine sahiptir. CoBr2 ve CoN2
antisimetrik ve simetrik gerilmeleri IR
aktif ve Raman aktiftir. Co(II)
komplekslerinin 420–399 cm–1 deki IR
bantları (Co-N) gerilmelerinden, 230–
210 cm–1 de görülen bantları da terminal
Co–Br bağ gerilme titreşimlerinden
kaynaklanmaktadır.
+z
Br
N
Br
+z
Cu(II) komplekslerinin titreşim
spektrumlarında sırasıyla 237-251 cm–1
ve 202–207 cm–1 aralığında gözlenen
terminal Cu–Br antisimetrik ve simetrik
bağ gerilemeleri metal atomu etrafındaki
tetragonal yapıyı gösterir. 200 cm–1 in
altında gözlenen bantlar eksenel zayıf
Cu-Br etkileşimlerinden
kaynaklanmaktadır.
Cu(II) kompleksleri için metal atomu
etrafındaki muhtemel yapı yandaki
şekilde verilmektedir. (N: 3-MA veya 4MA nın azot atomu; noktalı çizgi zayıf
Cu-Br etkileşmesini temsil eder).
Cu
Br
N
N
Br
Cu
Br
N
Br
–z
–z
–z
Zn(II) kompleksleri için metal–ligand ve
terminal metal–bromür titreşimleri
tetrahedral bir çevre için öngörülen
değerlerde çıkmaktadır. Buna göre
Zn(II) kompleksleri, N2ZnBr2
koordinasyon küresiyle C2v simetrisine
sahip tetrahedral bir çevrede
bulunmaktadır.
N
Br’
Br
Cd(II) ve Hg(II) komplekslerinin
titreşim spektrumlarında (uzak-IR ve
Raman) 200 cm–1 in üzerinde görülen
bantlar terminal Cd–Br ve Hg–Br bağ
gerilmesine ve 200 cm–1 altında ortaya
çıkan bantlar (Hg-Br)b titreşimlerine
karşılık gelir. Buna göre kompleksler 5koordinatlı dinükleer yapılardan veya
bir tane terminal M–Br bağına sahip
brom köprülü 5-koordinatlı polimerik
yapılardan meydana gelmektedir.
Cd(II) ve Hg (II) kompleksleri için metal
atomu etrafındaki muhtemel yapı
yandaki şekilde verilmektedir. (M: Hg
veya Cd; Br’: köprü yapmış Br atomu;
N: 3-MA veya 4-MA nın azot atomu).
N
M
M
Br
Br’
N
N
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