Ini materi kuliah

1. 2017

2.  Definisi electronic spectra (spektra
elektronik)
 Teori transisi elektronik
 Teori yang menjelaskan electronic spectra :
warna senyawa kompleks
 DiagramTanabeTsugano
 Deret spektrokimia
 Kemagnetan seny. kompleks
 Moment magnetik seny. kompleks

3.  Bil. Oksidasi bervariasi
 Warna
 Kemagnetan
 Ikatan kovalen koordinasi
 Interaksi asam-basa lewis

4. Berbagai warna senyawa logam transisi periode 4
titanium oxide
sodium chromate
potassium
ferricyanide
nickel(II) nitrate
hexahydrate
zinc sulfate
heptahydrate
scandium oxide
vanadyl sulfate
dihydrate
manganese(II)
chloride
tetrahydrate cobalt(II)
chloride
hexahydrate
copper(II) sulfate
pentahydrate

5.  Gemstone owe their color from trace
transition-metal ions
 Corundum mineral, Al2O3: Colorless
 Cr  Al : Ruby
 Mn  Al: Amethyst
 Fe  Al: Topaz
 Ti &Co  Al: Sapphire
 Beryl mineral, Be3 Al2Si6O18: Colorless
 Cr  Al : Emerald
 Fe  Al : Aquamarine

6. 6
warna berbagai senyawa kompleks dalam
larutan air :
3+ 3+ 2+ 2+ 2+ 2+ 2+
Ti , Cr , Mn , Fe , Co , Ni , Cu .

7. Mn(II) Mn(VI) Mn(VII)
V(V)
Cr(VI)
Mn(VII)
Warna seny. Kompleks dgn biloks bervariasi

8. [V(H2O)6]2+ [V(H2O)6]3+
[Cr(NH3)6]3+
[Cr(NH3)5Cl]2+

9.  VBT : ikatan
 CFT : elektronik spektra : warna dan
kemagnetan (spektra UV danVisible)
 MOT : ikatan
 LFT : elektronik spektra : warna dan
kemagnetan

10.  Mempelajari tentang spektra senyawa
kompleks berdasarkan tingkat energi
elektron dari suatu orbital (spektra
elektronik)
-->Aplikasi : bonding dan structure

11.  Absorpsi energi cahaya berada dalam daerah
sinar tampak oleh suatu senyawa ---->>
spektrum visible ---->> warna
 Absorpsi mengakibatkan terjadinya transisi
antara tingkat energi elektronik (transisi
elektronik)
Energi cahaya yang diserap oleh molekul
mengakibatkan transisi elektron ke tingkat
energi yang lebih tinggi setara (sama dengan)
perbedaan energi pada tingkat energi orbital

12. Warna senyawa kompleks

15.  Teori yang menjelaskan tentang eksitasi yang
teramati pada sebuah senyawa kompleks
Theory to explain electronic
excitations/transitions observed for metal
complexes

17. Selection rules
(determine intensities)
Laporte rule
g  g forbidden (that is, d-d forbidden)
but g  u allowed (that is, d-p allowed)
Spin rule
Transitions between states of different multiplicities forbidden
Transitions between states of same multiplicities allowed

19. Since these selection rules must be strictly obeyed,
why do many d-block metal complexes exhibit ‘d–d’
bands in their electronic spectra?
These rules are relaxed by molecular vibrations, and spin-orbit coupling

20. Breakdown of selection rules

21.  Vibrounic Coupling
Spin-allowed ‘d–d’ transitions remain Laporte-forbidden
and their observation is explained by a mechanism called
‘vibronic coupling
An octahedral complex possesses a centre of symmetry,
but molecular vibrations result in its temporary loss. At an
instant when the molecule does not possess a centre of
symmetry, mixing of d and p orbitals can occur. Since the
lifetime of the vibration (1013 s) is longer than that of an
electronic transition (1018 s), a ‘d–d’ transition involving an
orbital of mixed pd character can occur although the
absorption is still relatively weak

22.  Spin Orbit Coupling :
A spin-forbidden transition becomes
‘allowed’ if, for example, a singlet state mixes
to some extent with a triplet state.
but for first row metals, the degree of mixing
is small and so bands associated with ‘spin-
forbidden’ transitions are very weak

23.  In a molecule which is noncentrosymmetric
(e.g. tetrahedral), p–d mixing can occur to
a greater extent and so the probability of ‘d–d’
transitions is greater than in a
centrosymmetric complex.This leads to
tetrahedral complexes being more intensely
coloured than octahedral complexes.

27.  Macam-macam transisi elektronik :
a. transisi dalam tingkat energi orbital d ion
logam (d-d ‘ transition)
b.Transisi antara ion logam dengan ligan dalam
orbital molekul (charge transfer)
- LMCT (ligand to metal CT)
- MLCT (metal to ligandCT)
Intensitas absorbsi oleh transisi CT lebih tinggi
dibandingkan transisi d-d’

28. Absorption bands in electronic spectra are usually
broad; the absorption of a photon of light occurs in
10-18 s whereas molecular vibrations and rotations
occur more slowly
Therefore, an electronic transition is a ‘snapshot’ of
a molecule in a particular vibrational and rotational
state, and it follows that the electronic spectrum will
record a range of energies corresponding to
different vibrational and rotational states.

29.  Elektronic spectra :

31. 

35.  1T1g←1A1g and 1T2g←1A1g
 [Co(NH3)6]Cl3
 Absorbs violet/blue, ends up being orange-yellow
 2 absorption bands, symmetrical, Oh
 [CoCl(NH3)5]Cl2
 Absorbs green, ends up being magenta
 2 absorption bands, broadening on one
 C4v symmetry

36. Group theory analysis of term splitting

38. Free ion
term for d2
3F, 3P, 1G, 1D, 1S
Real complexes

39. Tanabe-Sugano diagrams
d2
• show correlation of
spectroscopic transitions
observed for ideal Oh complexes
with electronic states
• energy axes are parameterized
in terms of Δo and the Racah
parameter (B) which measures
repulsion between terms of the
same multiplicity

40. d2 complex: Electronic transitions and spectra
only 2 of 3 predicted transitions
observed

41. TS diagramsOther dn configurations
d1 d9
d3
d2 d8

42. d3
Other configurations
The limit between
high spin and low spin

44. The d5 case
All possible transitions forbidden
Very weak signals, faint color

45. symmetry labels

50. Charge transfer spectra
LMCT
MLCT
Ligand character
Metal character
Metal character
Ligand character
Much more intense bands

51. [Cr(NH3)6]3+

53. Determining Do from spectra
d1
d9
One transition allowed of energy Do

54. Lowest energy transition = Do
mixing
mixing
Determining Do from spectra

55. Ground state mixing
E (T1gA2g) - E (T1gT2g) = Do

56. 56
 Melibatkan serapan cahaya tampak.
 Warna yang tampak adalah warna komplemen
dari warna yang diserap.
Blue light
absorbed
Red light
transmitted

57.  Warna yang tampak adalah komplemen dari
Warna yang diserap
Warna yg
diserap
Warna
tampak

58. CFT
LFT : MOT dan CFT

59.  CFT : energi orbital d ion logam terpisah
(split) akibat adanya medan elektrostatik dari
ligan

60.  Model explaining bonding for transition metal
complexes
 • Originally developed to explain properties for
crystalline material
 • Basic idea:
 Electrostatic interaction between lone-pair electrons result in coordination.

61.  CFT - Electrostatic between metal ion and donor atom
i) Separate metal and ligand
high energy
ii) Coordinated Metal - ligand
stabilized
iii) Destabilization due to
ligand -d electron repulsion
iv) Splitting due to octahedral
field.
i
ii
iii
iv

62. Crystal FieldTheory - Describes bonding in Metal Complexes
 Basic Assumption in CFT:
 Electrostatic interaction between ligand and metal
d-orbitals align along the octahedral
axis will be affected the most.
More directly the ligand attacks the
metal orbital, the higher the the
energy of the d-orbital.
In an octahedral field the
degeneracy of the five d-orbitals is
lifted

63. Ligands
approach
metal
d-orbitals not pointing directly at axis are least
affected (stabilized) by electrostatic interaction
d-orbitals pointing directly at axis are
affected most by electrostatic
interaction

64.  Octahedral field Splitting Pattern:

The energy gap is
referred to as
D(10 Dq) , the
crystal field
splitting energy.
The dz2 and dx2-y2 orbitals lie on the same axes as negative charges.
Therefore, there is a large, unfavorable interaction between ligand (-) orbitals.
These orbitals form the degenerate high energy pair of energy levels.
The dxy , dyx and dxz orbitals bisect the negative charges.
Therefore, there is a smaller repulsion between ligand & metal for these
orbitals.
These orbitals form the degenerate low energy set of energy levels.

65.  Color of the Complex depends on magnitude of D
 1. Metal: Larger metal  larger D
 Higher Oxidation State  larger D
 2. Ligand: Spectrochemical series
 Cl- < F- < H2O < NH3 < en < NO2
- < (N-bonded) < CN-
 Weak field Ligand: Low electrostatic interaction: small CF
splitting.
 High field Ligand: High electrostatic interaction: large CF
splitting.
Spectrochemical series: Increasing D

66.  Electron configuration of metal ion:
 s-electrons are lost first.
 Ti3+ is a d1, V3+ is d2 , and Cr3+ is
d3
 Hund's rule:
 First three electrons are in
separate d orbitals with their spins
parallel.
 Fourth e- has choice:
 Higher orbital if D is small; High
spin
 Lower orbital if D is large: Low
spin.
 Weak field ligands
 Small D , High spin complex
 Strong field Ligands
 Large D , Low spin complex

67. Electron Configuration for Octahedral complexes of metal ion having d1 to
d10 configuration [M(H2O)6]+n.
Only the d4 through d7 cases have both high-spin and low spin configuration.
Electron configurations
for octahedral
complexes of metal ions
having from d1 to d10
configurations. Only
the d4 through d7 cases
have both high-spin and
low-spin configurations.

68.  The Colors of Some Complexes of
the Co3+ Ion
The complex with fluoride ion, [CoF6]3+ , is high spin and has one absorption band.
The other complexes are low spin and have two absorption bands. In all but one
case, one of these absorptionsis in the visible region of the spectrum.The
wavelengths refer to the center of that absorption band.
Complex Ion Wavelength of Color of Light Color of Complex
light absorbed Absorbed
[CoF6] 3+ 700 (nm) Red Green
[Co(C2O4)3] 3+ 600, 420 Yellow, violet Dark green
[Co(H2O)6] 3+ 600, 400 Yellow, violet Blue-green
[Co(NH3)6] 3+ 475, 340 Blue, violet Yellow-orange
[Co(en)3] 3+ 470, 340 Blue, ultraviolet Yellow-orange
[Co(CN)6] 3+ 310 Ultraviolet PaleYellow

69.  Warna seny. kompleks berkaitan dengan
adanya transisi elektron antar sub level
orbital d yang terpisah (split)
 Panjang gelombang pada serapan maks seny.
komplek dapat digunakan untuk menghitung
energi pemisahan antar sub level orbital d
yang terpisah
Ephoton = hn = hc/l = D

70.  Absorpsi radiasi UV-visible radiation oleh
atom, ion, molekul:
 Terjadi jika radiasi memiliki energi yang sama yang
dibutuhkan oleh atom, ion, molekul untuk eksitasi
elektron dari ground state ke excited state.
white
light
red light
absorbed
green light
observed

71. 71
Quantum-mechanical
description
 Absorption of light may occur
when the frequency of the
incoming photon, multiplied by
the Plank constant, is equal to the
difference in energy between
these two levels.

72. 72
Example:
 Ion cupric hidrat menyerap foton pada frekuensi Hz or 600
nm.
 Energi yang melibatkan transisi elektron pada ion
adalah
 Dapat dikatakan bahwa ion (Cu(H2O)6)2+ berwarna biru maka
ini berarti ion menyerap foton pada panjang gelombang 600 nm
(oranye) sehingga memberikan warna biru pada mata kita
34 14 -1 -19
(6.63 10 J s)(5 10 s ) 3 10 JE hn 
D   
2+
2 6Cu[H O]
14
5 10
2+
2 6Cu[H O]

74. 74
Example
 Ti memiliki konfigurasi , sehingga ion menjadi
ion. Ini berarti pada groundstate, 1 elektron akan menempati level
energi terendah pada d orbitals, sedangkan level energi yang lebih
tinggi kosong, setelah menyerap foton dengan energi tertentu, level
energi terendah pada d orbitals akan kosong.
3+
2 6Ti[H O]
2 2
4s 3d
3+
Ti
1
d

75. 75
ion absorbs light in the visible region; the wavelenght corresponding
to maximum absorption is 498 nm.
Crystal field splitting :
Itu adalah energi yang dibutuhkan untuk mengeksitasisatu elektron pada
ion
-34 8
-19
-9
(6.63 10 Js)(3 10 m/s)
3.99 10 J=240 kJ/mol
498 10 m
hc
hn
l
D    
3+
2 6Ti[H O]
3+
2 6Ti[H O]

76. 76
Spliting d-orbital sebesar 240 kJ per mol sesuai dengan panjang
gelombang cahaya warna blue-green ; absorpsi cahaya ini
mempromosikan elektron ke level energi yang lebih tinggi pada d
orbitals, yang merepresentasikan keadaan tereksitasi dari kompleks
Apabila kita melewatkan cahaya pada larutan maka cahaya
warna blue-green akan diabsorb dan larutan akan menampakkan
warna violet .
3+
2 6Ti[H O]
3+
2 6Ti[H O]

77.  Spektra larutan [Ti(H2O)6 ]3+

78.  Serapan senyawa Co (III)
warna senyawa kompleks kobalt (III) dalam larutan air
dengan berbagai macam ligan
Kiri : weak-field ligand – serapan pada energi rendah -
λ warna merah - warna tampak : hijau
Kanan : strong-field ligan – serapan pada energi besar
- λ warna ungu - warna tampak : oranye/kuning

80.  Perbedaan warna disebabkan oleh perbedaan
besarnya D
▪ D besar = energy untuk menyerap cahaya besar
▪ Panjang gelombang pendek
▪ D kecil = energy untuk menyerap cahaya kecil
▪ Panjang gelombang panjang
 Besarnya D tergantung pada:
▪ ligand
▪ logam

81.  Logam
a. logam ukuran besar  D besar
[Fe(H2O)6]3+
[Co(H2O)6]2+
[Ni(H2O)6]2+
[Cu(H2O)6]2+
[Zn(H2O)6]2+

83. b. biloks logam tinggi  D besar
[V(H2O)6]2+ [V(H2O)6]3+
Mn(II) Mn(VI) Mn(VII)

84.  Deret yang menyatakan urutan kekuatan ligan
berdasarkan besarnya ∆ yang dihasilkan

85.  Deret kekuatan ligan berdasarkan besarnya
∆o

86.  Deret kekuatan logam berdasarkan besarnya
∆o

87.  Menggabungkan penjelasan tentang orbital
molekul dengan perbedaan tingkat energi
pemisahan orbital /splitting

97. N  C *
Splitting from  - bonding: Weak and Strong Field ligands
Contoh ligan Cl- (weak) danCN- (strong)
Cl
N  C
M
N  C
 - bonding as before
Now  - bonding between p & dxy, dxz, dyz
 - bonding as before
Now  - bonding between CN- * & dxy, dxz, dyz
No  - bonding with CN- 
M
sp hybridized for -bonding,
left over p orbitals make  and * orbitals

98.  Ligan dengan orbital p terisi

100. s*
p*
dxy, dxz, dyz
  
d* = eg
= t2g
6
4p
4s
3d
6 Ligands
Cl- sp orbitals
Metal LigandMolecule
12 Cl- p orbitals
E (Cl- p) < E (M d) !!!
Decrease Doct
 Weak Field Ligand
     
 - bonding: p orbitals give Weak Field Ligands (Cl- example)
Input d e-’s
Cl
-bonding orbitals
*-antibonding orbitals

102.  Ligan yang memiliki orbital π * kosong

104. Ligan Phi-akseptor

106. s*
p*
dxy, dxz, dyz
  
d* = eg
= t2g
6
4p
4s
3d
6 Ligands
CN- sp orbitals
Metal LigandMolecule
12 CN- * orbitals
E (CN- * ) > E (M d) !!!
Increase Doct
 Strong Field Ligand
 - bonding: * orbitals give Strong Field Ligands
Input d e-’s
N  C *
-bonding orbitals
*- antibonding orbitals

108. Molecular OrbitalTheory Explains Field Strength of Ligands
1) Ligand p orbitals cause  - bonding that raises t2g energies
Weak Field Ligands
2) Ligand * orbitals cause  - bonding that lowers t2g energies
Strong Field Ligands
3) sp3 hybridized ligands do not change t2g orbitals very much
Medium Field Ligands
dxy, dxz, dyz
d* = eg
= t2g
12 Cl- p orbitals
dxy, dxz, dyz
d* = eg
= t2g
12 CN- * orbitals
*

No p or * orbitals for -bonding !!!

110.  Metal to ligand : M---L
Phi akseptor/phi acid
 Ligan to metal : L---M
phi donor/phi base

111.  Ligan
a.Weak field ligan
interaksi elektrostatik ligan dengan
logam rendah - ∆ kecil
b. Strong field ligan
interaksi elektrostatik ligan dengan logam
tinggi - ∆ besar

113.  Ligan diklasifikasikan berdasarkan kemampuan
donor atau akseptor π
 Ligan dgn orbital p terisi ----- π donor
Ligan dgn orbital π * atau d kosong ---- π akseptor

117.  Kemagnetan senyawa kompleks
berhubungan dengan bagaimana elektron
terdistribusi pada orbital d.
 Kemagnetan senyawa kompleks diukur pada
suatu medan magnet.

119.  Senyawa kompleks dengan elektron tidak
berpasangan : menghasilkan medan magnet /
tertarik pada medan magnet.
 Senyawa kompleks dengan elektron
berpasangan : tidak menghasilkan medan
magnet / menolak medan magnet.

120.  Momen magnetik
Suatu ukuran yang berkaitan dengan jumlah
elektron tidak berpasangan.

121.  Moment magnetik :
Dimana :

122.  Dengan g = 2,0003 = 2 dalam Bohr magneton,
dan momentum orbital diabaikan, maka

123.  Dan S = n/2, maka momen magnetik :
 Satuan moment magnetik = BM (Bohr
Magneton)
1 BM = 9,27 x 10-24 Joule/Tesla

125. 1. Hitung moment magnetik komplek Cr(III) dan
Ti (III)
2. Moment magnetik Kompleks Co(II) adalah
4,0BM. Prediksikan konfigurasi elektron
orbital d pada kompleks tersebut!
3. Moment magnetik Kompleks Fe(III) adalah
5,3BM. Prediksikan konfigurasi elektron
orbital d pada kompleks tersebut!

126.  Jawab :
1. Cr3+
n = 3
μs = √3(3+2) BM
= 3,87 BM

127.  Jawab :
3. Fe 3+ , n = 5
a. dihitung μs untuk kompleks high spin dan low
spin.
b. kemudian tentukan mana yang nilainya paling
mendekati nilai sebenarnya/eksperimen (5,3 BM)
c.kemudian tulis konfigurasi elektron high spin
atau low spin sesuai hasil b. Misal : untuk
jawaban highspin, maka konf elektronny t2g3eg2

128. 4. PadaT = 298 K diketahui bahwa momen
magnetik kompleks [Cr(NH3)6]Cl2 adalah
4,85BM. Nyatakan apakah kompleks tersebut
high spin?

129.  TUGAS :
Baca buku Huhey, Douglas, dan buku teks
Anorganik lain yang menjelaskan tentang
spektra elektronik senyawa kompleks dan
kemagnetan
Silahkan berlatih menghitung momen
magnetik dari soal-soal yang ada di buku teks