Question

please answer

10. The UV-vis spectrum of [Cr(NCS)613- has a very weak band near 16,000 cm'', a band at 17,000 cm" with Emax = 160 M cm, a band at 23,800 cm' with &max = 130 M cm', and a very strong band at 32,400 cm!. Assign these transitions using the appropriate Tanabe-Sugano diagram and selection rule considerations (see Table 20.8 in the text). Assign each band as spin allowed or forbidden and Laporte allowed or forbidden. What is the wavelength of each band in nm?

Answer 1

17000 cm^-1: ⁴A_2g ---> ⁴T_2g

23800 cm^-1: ⁴A_2g ---> ⁴T_1g(F)

32400 cm^-1: ⁴A_2g ---> ⁴T_1g(P)

All the three transitions shown are spin allowed, but Laporte forbidden (d-d transitions).

16000 cm^-1: 1/$\lambda$ = 16000 cm^-1, i.e. $\lambda$ = 625 nm (Note: 1 nm = 10^-7 cm)

17000 cm^-1: 1/$\lambda$ = 17000 cm^-1, i.e. $\lambda$ = 588.24 nm (Note: 1 nm = 10^-7 cm)

23800 cm^-1: 1/$\lambda$ = 23800 cm^-1, i.e. $\lambda$ = 420.17 nm (Note: 1 nm = 10^-7 cm)

32400 cm^-1: 1/$\lambda$ = 32400 cm^-1, i.e. $\lambda$ = 308.64 nm (Note: 1 nm = 10^-7 cm)