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Lecture 19.1

# Lecture 19.1 - 25700/17800 = 1.44 The ratio of energy of...

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1 Chem 172 Advanced Inorganic Chemistry Lecture 20/May 17 th Continued from Lecture 19 Electronic Spectra of Coordination Compound Applications of Tanabe-Sugano Diagrams: Determining Δ o from spectra Δ o can be determined depend on the d electron configuration of the Metal d 1 , d 4 (high spin), d 6 (high spin), d 9 d 1 d 4 (high spin) d 6 (high spin) d 9 Determining Δ o for d 1 , d 4 (h.s.), d 6 (h.s.), and d 9 confg. d 2 (or d 7 confg.) d 3 (or d 8 confg.) Δ o = the energy difference between 3 A2g and 3 T2g Δ o= [Energy of transition 3 T1g 3 A2g] – [Energy of transition 3 T1g 3 T2g] ν 1 3 T1g(F) 3 T2g ν 2 3 T1g(F) 3 T1g(P) ν 3 3 T1g(F) 3 A2g Example: [V(H 2 O) 6 ] 3+ has absorption at 17800 and 25700 cm -1 . Using Tanabe-Sugano diagram for d 2 , estimate values of Δ o and B for this complex. From the Tanabe-Sugano diagram there are three possible spin- allowed transitios: ν 1 3 T1g(F) 3 T2g (lowest energy) ν 2 3 T1g(F) 3 T1g(P) ν 3 3 T1g(F) 3 A2g The ratio of energies of the absorption bands,
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Unformatted text preview: 25700/17800 = 1.44 The ratio of energy of the higher energy transition( ν 2 or ν 3 ) to the lowest energy transition ( ν ) must be approximately 1.44. FromT-S diagrams, we can see that the ratio of ν 3 to ν 1 is approximately 2,regardless of the srength of ligand field thereby eliminating ν 3 . This means that the 25700 band must be ν 2 for ν 2 3 T1g(F) → 3 T1g(P). 1.44 = ν 2 / ν 1 The ratio varies as a function of the strength of the ligand field.By taking values from Fig. And plotting the ratio ν 2 / ν 1 versus Δ o/B We find that ν 2 / ν 1 = 1.44 approximately Δ o/B= 31 ν 2 : E/B = 42(approximately): B= E/42 = 25700cm-1 /42 = 610 cm-1 ν 1 . E/B = 29 (approximately): B= E/29 = 17800 cm-1 /29= 610 cm-1 Since Δ o/B= 31, Δ o= 31xB = 31x 610 cm-1 = 19000cm-1...
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