Calculation of magnetic moments of CoL2X2 complexes

* 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.