The document discusses electronic spectra and color of transition metal complexes. It explains that the color of complexes is due to electronic transitions between split d-orbital energy levels of the metal ion. Crystal field theory is used to describe the splitting of d-orbitals in an octahedral ligand field, which determines the color. Complexes with strong field ligands have large splitting and absorb at higher energies, appearing more intensely colored.
Teori orbital molekul didasarkan pada hasil eksperimen dengan metode resonansi spin elektron yang menunjukkan adanya pemakaian bersama pasangan elektron oleh atom pusat dengan ligan. Hal ini menunjukkan pada pembentukkan senyawa kompleks disamping terjadi interaksi elektrostatik atau interaksi ionic, juga terjadi interaksi kovalen
Teori orbital molekul merupakan teori yang paling lengkap karena menyangkut interaksi elektrostatik dan interaksi kovalen . Berdasarkan teori orbital molekul, pada pembentukkan senyawa kompleks, orbital-orbital pada atom pusat dengan orbital-orbital dari ligan saling berinteraksi membentuk orbital-orbital molekul baru. Berdasarkan pedekatan linier, orbital-orbital molekul senyawa kompleks dianggap merupakan kombinasi linier dari orbital-orbital atom pusat dan orbital-orbital ligan. Perbedaan energy antara orbital-orbital atom pusat dengan ligan dapat diabaikan oleh karena itu dalam menggambarkan orbital molekul senyawa kompleks cukup digambarkan dengan orbital-orbital valensinya
Teori orbital molekul didasarkan pada hasil eksperimen dengan metode resonansi spin elektron yang menunjukkan adanya pemakaian bersama pasangan elektron oleh atom pusat dengan ligan. Hal ini menunjukkan pada pembentukkan senyawa kompleks disamping terjadi interaksi elektrostatik atau interaksi ionic, juga terjadi interaksi kovalen
Teori orbital molekul merupakan teori yang paling lengkap karena menyangkut interaksi elektrostatik dan interaksi kovalen . Berdasarkan teori orbital molekul, pada pembentukkan senyawa kompleks, orbital-orbital pada atom pusat dengan orbital-orbital dari ligan saling berinteraksi membentuk orbital-orbital molekul baru. Berdasarkan pedekatan linier, orbital-orbital molekul senyawa kompleks dianggap merupakan kombinasi linier dari orbital-orbital atom pusat dan orbital-orbital ligan. Perbedaan energy antara orbital-orbital atom pusat dengan ligan dapat diabaikan oleh karena itu dalam menggambarkan orbital molekul senyawa kompleks cukup digambarkan dengan orbital-orbital valensinya
How do we describe the bonding between transition metal (ions) and their ligands (like water, ammonia, CO etc) ?
The Crystal Field Model gives a simple theory to explain electronic spectra.
How do we describe the bonding between transition metal (ions) and their ligands (like water, ammonia, CO etc) ?
The Crystal Field Model gives a simple theory to explain electronic spectra.
This Presentation describes about the evidence of metal ligand bonding in a molecule. In this presentation various evidences are explained. Learn and grow.
Introduction, position in periodic table, transition elements & inner transition elements, lanthanoids & actinoids, General trends in properties, atomic radii, atomic volume, melting points, boiling points, density, standard electrode potentials, oxidation states, Some practice questions.
Theories of coordination compounds, CFSE, Bonding in octahedral and tetrahedral complex, color of transition metal complex, magnetic properties, selection rules, Nephelxeuatic effect, angular overlap model
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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
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
15. Teori yang menjelaskan tentang eksitasi yang
teramati pada sebuah senyawa kompleks
Theory to explain electronic
excitations/transitions observed for metal
complexes
16.
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
18.
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
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.
24.
25.
26.
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.
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
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
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]
73.
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]
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
79.
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+
82.
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
87. Menggabungkan penjelasan tentang orbital
molekul dengan perbedaan tingkat energi
pemisahan orbital /splitting
88.
89.
90.
91.
92.
93.
94.
95.
96.
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
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
107.
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 !!!
109.
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
112.
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
114.
115.
116.
117. Kemagnetan senyawa kompleks
berhubungan dengan bagaimana elektron
terdistribusi pada orbital d.
Kemagnetan senyawa kompleks diukur pada
suatu medan magnet.
118.
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.
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
124.
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!
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