LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

GH 61

M.Sc. DEGREE EXAMINATION – CHEMISTRY

FOURTH SEMESTER – APRIL 2008

    CH 4953 – ADVANCED COORDINATION CHEMISTRY

 

 

 

Date : 06/05/2008            Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

PART-A

Answer all questions. Each question carries 2 marks                                  (10 x 2 = 20)

 

1. What are compartmental ligands? Give an example.
2. Electron transfer for Cr(II)/Co(III) system follows inner-sphere mechanism whereas the V(II)/Ru(III) system follows outer-sphere mechanism. Give reason.
3. What are optically transparent electrodes?
4. Explain photosubstitution reaction with an example.
5. ‘Contrary to the usual observation, the CN stretching vibration of coordinated cyanide appears at higher energy than that of the free cyanide’. Rationalize.
6. Octahedral complexes of high-spin d5metal ions are feebly colored whereas octahedral complexes of low-spin d5 metal ions are intensely colored. Explain.
7. Mention the purpose of using internal electrochemical standard. Cite two examples.
8. What is intensity stealing?
9. Lower oxidation states of transition metal ions are stabilized by p-acids. Offer a resonable explanation.
10. How does change in the angular orientation of the ligand with respect to the metal ions affect the magnitude of s- and p-bonding?

PART-B

Answer eight questions. Each question carries 5 marks                                        (8 x 5 = 40)

 

11. Illustrate with examples the study of fluxional isomerism by NMR spectroscopy with two examples.
12. Derive Marcus-Hush equation to compute the rate constant of electron transfer reactions.
13. Explain the mechanism of in vivo nitrogen fixation?
14. Write a short note on charge transfer photochemistry.
15. Explain Adamson’s rule in the photosubstitution of metal complexes with an example.
16. Explain template synthesis of macrocyclic complexes with two examples.
17. What is spin crossover? Explain the experimental methods of studying it.
18. Illustrate static-dynamic Jahn Teller effect with an illustrative example.
19. Explain the electronic absorption spectral features of high spin octahedral and tetrahedral complexes of transition metal ions.
20. Explain photoisomerization reaction with examples.
21. What are Orgel diagrams? Construct Orgel diagram for high-spin d3and d7 O_h and T_d complexes.
22. How do you differentiate thiocyanato- and isothiocyanato complexes by IR spectroscopy.

 

PART-C

Answer four questions. Each question carries 10 marks                                   (4 x 10 = 40)

 

23. According to MO theory, p-donation by ligands lowers the magnitudes of 10D_q values whereas p-back bonding increases its magnitude. Explain with a qualitative MO energy level diagrams.

24a.  Explain the structural features and biological role of Fe-S proteins.                 (6)

1. Write a note on synthetic oxygen carriers.                                                         (4)

25a.  Explain the structural features of cytochromes.                                                (5)

1. Explain the role of cytochromes as bio-redox agents.                                       (5)
2. A six-coordinate low-spin cobalt(III) complex of a quadridentate ligand with two thiocyanate ions exhibits electronic transitions at 660 nm (Î = 76.5 L mol-1cm-1), 525 nm (Î = 1260 L mol-1 cm-1), 415 nm (Î = 396 L mol-1 cm-1), and 290 nm (Î = 10658 L mol-1 cm-1). Assign these transitions, predict the geometry, and compute the field strength of the ligands.

27a.  Explain the principle of angular overlap model. How s- and p-bonding are quantified in this model?                                                                                                  (3)

1. Prove that 4/9D_o = D_t  with usual notations.                                          (7)
2. Explain the template synthesis of macrocyclic ligands and mono- and dinuclear complexes.

 

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