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Topic: Naphthalene's pi SALCs  (Read 6186 times)

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Offline Vital Y

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Naphthalene's pi SALCs
« on: February 19, 2016, 04:51:30 AM »
I tried obtaining the pi SALCs of naphthalene. I got the reducible representation as 2A1u + 3B1u + 3B3g + 2B2g. I thought that if I considered the carbons (1,4,5,8) and (2,3,6,7) to belong to two D4h groups and the carbons (9,10) belong to a C2 group, I could find the SALCs without the projection operator (The link is an image of naphthalene with the carbons in it numbered). I tried using D4h point group's D2 sub group but the irreps do not have the same symmetry properties in the two point groups. Is there any way to obtain the SALCs of naphthalene without using the projection operator?

https://upload.wikimedia.org/wikipedia/commons/6/61/Naphthalene-numbering-2D-skeletal.png

Offline Corribus

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Re: Naphthalene's pi SALCs
« Reply #1 on: February 19, 2016, 09:20:53 AM »
Not that I'm aware of. What would be the point, anyway? The projection operator is easy to use, so why complicate your life by trying to use multiple symmetry groups?
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline Vital Y

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Re: Naphthalene's pi SALCs
« Reply #2 on: February 19, 2016, 09:26:56 AM »
I find using the sub group approach easier. When calculating benzene's SALCs you can use the C6 point group's character table and directly obtain them.

Offline mjc123

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Re: Naphthalene's pi SALCs
« Reply #3 on: February 19, 2016, 11:03:59 AM »
You are aware that naphthalene doesn't have D4h symmetry?

Offline Vital Y

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Re: Naphthalene's pi SALCs
« Reply #4 on: February 19, 2016, 12:10:43 PM »
Yes I am aware that it doesn't have D4h as its point group, but instead has D2h. My question is even if it possess D2h can we obtain its SALCs using the idea of dividing the molecule into regions and then finding those region's point groups.

Offline Corribus

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Re: Naphthalene's pi SALCs
« Reply #5 on: February 19, 2016, 01:42:54 PM »
Even if you could reduce the complexity of the problem in the way you are attempting to, the grouping {2,3,6,7} wouldn't belong to D4h anyway (they basically form a rectangle, not a square), so it's no surprise that your orbitals are not transforming properly.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline Vital Y

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Re: Naphthalene's pi SALCs
« Reply #6 on: February 19, 2016, 09:36:30 PM »
So does this mean that (1,4,5,8) and (2,3,6,7) belong to the D2 group? How will we relate A1u, B1g, B2g, B3g with D2's irreps? B2g and B3g can be related to B2 and B3 of the D2 point group, but I couldn't find a relation for A1u and B1u.
« Last Edit: February 19, 2016, 10:18:47 PM by Vital Y »

Offline Irlanur

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Re: Naphthalene's pi SALCs
« Reply #7 on: February 20, 2016, 06:16:10 AM »
What you could try is to obtain the MO's of cyclodecapentaene in the symmetry of naphtalene and then use a perturbation approach to get to the MO's of naphtalene. I doubt that this is easier than doing it directly for naphtalene.

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