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Factors affecting the magnitude of 10 Dq
- 1. Factors affecting the magnitude of 10 Dq. Dr. Mithil S. Fal Desai Assistant Professor in Chemistry SHREE MALLIKARJUN & Shri Chetan Manju Desai College Canacona Goa
- 2. Background and references 2 1. Concise Inorganic Chemistry, J. D. Lee, Chapman & Hall India, 4rth Edition, Year 1991 2. Inorganic Chemistry: Principle of structure and reactivity, J. E. Huheey, E. A. Keiter. R. L. Keiter, O. K. Medhi, Pearson Education India, 4rth Edition, Year 2006 • Crystal Field splitting • Crystal field stabilization energy • Degenerate orbitals • Spectrochemical series • 3d and 4d transition series • Octahedral and tetrahedral field
- 3. 10 Dq Five degenerate d orbitals in free metal ion Five d orbitals in octahedral field d orbitals are split into two groups dz 2 dx 2 -y 2 dxy dyz dxz eg t2g energy The difference in energy between the two d levels (eg and t2g) in a octahedral field is given either of the symbols Δo or 10 Dq. 10 Dq or Δo M +z -z -x -y +x +y L L L L L L The term Dq is derived from quantum mechanics and is product of two terms D (L=2) and q and is called Differential of quanta (implying the energy).
- 4. Δo and Δt Five degenerate d orbitals in free metal ion Five d orbitals in octahedral field dz 2 dx 2 -y 2 dxy dyz dxz eg t2g dz 2 dx 2 -y 2 dxy dyz dxz eg t2g Five d orbitals in tetrahedral field energy -0.4 Δo +0.6 Δo +0.4 Δt -0.6 Δt Δt Δo Bari centre (average energy level)
- 5. 1) The nature of the ligands Spectrochemical series I- < Br- < S2-< Cl- < NO3 - < F- < OH- < EtOH < oxalate < H2O < EDTA < (NH3 and pyridine) < ethylenediamine < dipyridyl < o-phenanthrolir:ie < NO2 - < CN- < CO Weak field ligand Strong field ligand eg t2g Δo eg t2g Δo Complex Absorption peak in cm-1 Energy in kJ mol-1 [CrCl6]3- 13640 163 [Cr(CN)6]3- 26280 314 Five degenerate d orbitals Five degenerate d orbitals The crystal field splitting produced by the strong field like CN- ions is about double that for weak field ligands like the halide ions.
- 6. 2)The charge on the metal ion. eg t2g Δo eg t2g Δo Complex Absorption peak in cm-1 Energy in kJ mol- 1 Electronic configuration [Co(H2O)6]2+ 9300 111 d7 [Co(H2O)6]3+ 18600 222 d6 Five degenerate d orbitals Five degenerate d orbitals In 3d transition metal ions, the values of 10 Dq for M3+ complexes are approximately 50% larger than the values for M2+ complexes
- 7. 3) Position of metal ion in 3d or 4d or 5d transition series. eg t2g Δo eg t2g Δo Complex Absorption peak in cm-1 Energy in kJ mol-1 [Co(NH3)6]3+ 24800 296 [Rh(NH3)6]3+ 34000 490 Five degenerate d orbitals Five degenerate d orbitals The value of 10 Dq also increases by about 30% between adjacent members down a group for the transition elements
- 8. 4) Number of Ligands • The magnitude of crystal field splitting(10 Dq) increases with the increase of the number of ligands. ∆O > ∆t