Question

Electronic absorption spectrum of copper ammine complexes

Visible absorption spectra of Cu(ll) complexes 1.2 Cu (H20)2(NH3)4 Cu (H2O)6 Cu (H20)3(NH3)3 0.8 0.6 Cu (H20)s(NH3) Cu (H20)4(NH3)2 0.4 0.2 850 500 550 600 650 700 750 800 900 450 nm Wavelength peak Absorbance 811.0 nnm 0.916 [Cu (H2O)6 [Cu (H2O)5(NH3)2 0.396 760.5 nm [Cu (H2O)4(NH3)212+ 688.0 nmm 0.340 [Cu (H20)3(NH3)32 645.0 nm 0.674 [Cu (H20)2(NHa)42 1.069 602.5 nm

1. (i) Draw the electron distribution in the d orbitals of an octahedral Cu(II) complex and show the electronic transition responsible for the absorptions observed.

2. (ii) Assign the transition you observe for each complex and give the value of Δ (in cm-1).

Answer 1

tDbbe 2. tohgruation 2Ta Thus, th tothis 2 igand held strugth t elrchonc Has elschouic

of ht abcobed 4 688X40= 27520

tDbbe 2. tohgruation 2Ta Thus, th tothis 2 igand held strugth t elrchonc Has elschouic

a) Cu (HD).121 Elecnic A value iu di er A5 406 6.6 tm