[Astrokel]

 Hey all,

I understand that colours in transition metal compounds is due to d-->d* transition. I remember the lecturer metioned that there are many coloured transition compounds are not due to d--->d* , but she was brief mentioning. I searched over the net and the only explanation is due to d--->d*, promote electron, absorb visible light and so on. Are you aware of any other reasons?

thank you.

[enahs]

Start here:
http://www.chemguide.co.uk/inorganic/complexions/colour.html#top

That is like a more detailed version of what your teacher said.

Then look up Crystal Field Theory for the more advanced explanation (it has a Wikipedia page, naturally).

[Astrokel]

hey enahs,

i think i did not state my question properly, my lecturer metioned, there are many situations where colour in transition metal compounds is not due to d ---> d* electron transition. She did not metion what are the other reasons for colours, so im wondering if anyone is aware of any other reasons?

I'm aware of chemguide and CFT, but they are talking about the d--->d* electron transition.

Thanks,

[KhemistKen]

There are other transitions, such as charge transfer transitions, which occur in some transition metal complexes.  For example, the intense purple color of permanganate is due to a charge transfer transition -- an electron jumps from one of the oxygen atom orbitals to a manganese atom orbital (unless I have it backwards and it's the other way around).   

[Astrokel]

There are other transitions, such as charge transfer transitions, which occur in some transition metal complexes.  For example, the intense purple color of permanganate is due to a charge transfer transition -- an electron jumps from one of the oxygen atom orbitals to a manganese atom orbital (unless I have it backwards and it's the other way around).  

Thank you!  That is what i was looking for! do you have any specific site for reference?

[Astrokel]

I have googled it and found some great sites, thanks once again!!