calculation of magnetic moments of col2x2 complexes
DESCRIPTION
Calculation of magnetic moments of CoL2X2 complexes. Objectives. * To explain how the mass susceptibility can be calculated.?. * To explain how the molar susceptibility can be calculated from the mass susceptibility.?. - PowerPoint PPT PresentationTRANSCRIPT
* To explain how the mass susceptibility can be calculated.?
* To explain how the molar susceptibility can be calculated from the mass susceptibility.?
* To explain how the diamagnetic correction is carried out on xM to calculate xpara..?
* To predict the geometries and the spin state of the Co(II) complexes using magnetic moments.?
* To explain how the magnetic moment can be calculated.?
1
2
3
4
5
4.2439
4.2825
6
7
Where m = tube filled with solid – empty
tube = empty tube field on – empty
tube field off = tube filled with solid, field on –
tube filled with solid, field offV = (tube filled with water –
empty tube) / density of waterg of standard = 16.44E-6 cgs
(m)- (0.029 10-6 )V = (- )
we calculate (calibration constant) by using m, and Xg (mass susceptiblity )of the standard :
(m)- (0.029 10-6 )V =
(- )
4
6
100655.2
)10029.0()(
Vm
X(g)= 16.44x10-6 cm3/g(emu/g)
By using the value of we calculate X(g) of the sample :
(m)- (0.029 10-6 )V = (- )
molemu
molggemu
massmolar
ysuscebilitMolar
gemu
m
M
gM
g
V
g
/01018.0
/362.361/)10819.2(
:)(
/10819.2
10029.0()(
5
5
)6
para = M - dia
atom A(10-6) cm3/mol
atom A(10-6) cm3/mol
H-2.93N-5.57
C( aliphatic)
-6.00N( aromatic)
-4.61
C( aromatic)
-6.24Co2+-12.00
S-15.0
Type of atom
# of atoms
xgTotal XDIA
Co2+1-12.8 x 10-
6
-12.8 x 10-6
H14-2.9310-6-4.102x10-5
C(aromatic)
10-6.24 10-
6
-6.24x10-5
C(aliphatic)
4-6.00 10-
6
-2.40x10-5
N(aromatic)
2-4.61 10-
6
-9.22x10-6
N (aliphatic)
2-5.57 10-
6
-1.114x10-5
S2-15.00 10-6
-3.00x10-5
Total=-1.9058x10-4
cm3/mol.AND
Remember that this unit =
emu/mol
BM
KBMK
XT
KBMmolemu
molemux
xxx
eff
eff
paraeff
para
DIAMpara
95.4
/01037.0295828.2
828.2
/(/01037.0
/109058.101018.0
2
2
4
From this value.How can you
determine the geometry and
the spin state of the complex?..
Co2+ (d7)
High Spin
Co2+ (d7)
Low Spin
eg
t2g
eg
t2g
19.5
14
112
87.3
14
3,2/3,3
2/1
2/1
LLSSu
BM
SSu
LSn
LS
s
BM
LLSSu
BM
SSu
LSn
LS
s
16.6
14
112
73.1
14
5,2/1,1
2/1
2/1
TetrahedralCo2+ (d7) only
High Spin
t2
e
19.5
14
112
87.3
14
3,2/3,3
2/1
2/1
LLSSu
BM
SSu
LSn
LS
s
Tetrahedral geometry
ComplexesComplexesColor (solid)Color (solid)μμeffeff (B.M) (B.M)
Co(py)Co(py)22ClCl22BlueBlue 4.424.42
Co(py)Co(py)22II22BlueBlue4.474.47
Co(Py)Co(Py)22BrBr22BlueBlue4.504.50
Co(2-Me-py)Co(2-Me-py)2 2 (Cl)(Cl)22BlueBlue4.474.47
Co(2-Me-py)Co(2-Me-py)2 2 (NCS)(NCS)22BlueBlue4.304.30
Co(3-Me-py)Co(3-Me-py)22ClCl22BlueBlue 4.494.49
Co(3-Me-py)Co(3-Me-py)22BrBr22BlueBlue 4.484.48
Co(3-Me-py)Co(3-Me-py)22(NCS)(NCS)22BlueBlue 4.304.30
ComplexesComplexesColor (solid)Color (solid)μμeffeff (B.M) (B.M)
Co(4-Me-py)Co(4-Me-py)22BrBr22BlueBlue 4.414.41
Co(4-Me-py)Co(4-Me-py)22(NCS)(NCS)22BlueBlue 4.304.30
Co(3-Et-py)Co(3-Et-py)22BrBr22BlueBlue4.704.70
Co(3-Et-py)Co(3-Et-py)22(NCS)(NCS)22BlueBlue 4.464.46
Co(4-Et-py)Co(4-Et-py)22BrBr22blueblue4.454.45
The magnetic moment of tetrahedral geometry is
in range(4.30 – 4.74 B.M.) and absorb light strongly
at range (580-780) nm .
Octahedral geometry
ComplexesComplexesColor (solid)Color (solid)μμeffeff (B.M) (B.M)
Co(py)Co(py)44ClCl22PinkPink 5.155.15
Co(Py)Co(Py)44(NCS)(NCS)22Purple-redPurple-red5.105.10
Co(3-Me-py)Co(3-Me-py)44ClCl22PinkPink 4.944.94
Co(3-Me-py)Co(3-Me-py)44BrBr22PinkPink 5.075.07
Co(3-Me-py)Co(3-Me-py)44(NCS)(NCS)22PinkPink 5.035.03
Co(4-Me-py)Co(4-Me-py)44(NCS)(NCS)22LilacLilac4.924.92
Co(3-Et-py)Co(3-Et-py)44BrBr22PinkPink 5.025.02
Co(3-Et-py)Co(3-Et-py)44(NCS)(NCS)22lilaclilac5.155.15
The magnetic moment of octahedral geometry is in range(4.90 – 5.40 B.M.) and absorb light
weakly in the range (640-600
nm)
High λLow ∆0
HS.ueff= 4.95 BM
Tetrahedral(4.30-4.74 ) BM
1.Magnetic moments are used to determine the spin state (high spin or low spin).
2.Octahdral complexes can be either high spin or low spin.
3.Tetrahedral complexes can only be high spin.
4.Experimental magnetic moments for Co(II) Complexes are always higher than the spin-only magnetic moments because of the significant
Orbital contribution.
5.The magnitude of the orbital contribution differ for tetrahedral and octahedral ,it is greater for octahedral than for tetrahedral. Therefore ,we can distinguish between tetrahedral and octahedral.
Tetrahedral; 4.30 – 4.72 B.M.
Octahedral; 4.90 – 5.40 B.M.
