Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: rubymelia on 03/02/2019 12:28:33

Title: How do I identify bridging Mo-O and terminal Mo=O in FTIR spectrum?
Post by: rubymelia on 03/02/2019 12:28:33

I have produced some FTIR spectrum samples for the following compounds: [n-Bu₄N]₄[Mo₈O₂₆] , [n-Bu₄N]₂[Mo₆O₁₉], [n-Bu₄N]₂[Mo₂O₇]  and am trying to identify the bands and wavenumber values for (Mo-O) for various terminal and bridging Mo-O bonds in each of the anions.
I expect the bands to be around 500-1200 cm^-1 but I am unsure on how to assign them within the region.
Thanks

Title: Re: How do I identify bridging Mo-O and terminal Mo=O in FTIR spectrum?
Post by: chiralSPO on 04/02/2019 22:10:24

The terminal bonds will have higher stretching frequencies than the bridging ones. I don't know off the top of my head where these will all lie, but based on Co-O and Co-O-Co vibrations, which I am more familiar with, I would expect bridging Mo-O-Mo vibrations to be around 300 cm^–1, terminal Mo-O-H to be more like 600^–1, and Mo=O might be closer to 1000^–1...

I am certain this info can be looked up. You can also model it using DFT.