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Topic: Point Groups  (Read 11247 times)

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Offline CopperSmurf

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Point Groups
« on: November 17, 2007, 05:17:52 PM »
Hey, this seems to be a simple concept, but it's hard to visualize.
What's the point group on Ni EDTA ? I'm thinking that it is C2 but I'm not too sure if there's any symmetry in that huge thing.
Also, what's a good way for determining point groups?

Thanks for reading this
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Offline hmx9123

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Re: Point Groups
« Reply #1 on: November 18, 2007, 01:50:46 AM »
Point groups can be hard to visualize sometimes.  If you're having a lot of trouble, build a model.  Your book should have an algorithm (a series of steps) for figuring out what symmetry the molecule is.  Take a look through it and walk through the book.

The other way to do it is to build a model on a molecular modeling program, minimize the structure, then look at the print out.  It will tell you what the point group is. :)  Kind of nice to check your work sometimes.

Oh, and if you could post a picture of the molecule you're after, that would be a big help.
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Offline CopperSmurf

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Re: Point Groups
« Reply #2 on: November 18, 2007, 10:28:17 AM »
I tried building a model with toothpicks and some dough, dunno if it's right haha.
I didn't know molecular modeling programs exist! Are there any free ones?
And uhm... I don't have a proper picture of this weird molecule but I think it's supposed to look like 4 rings (each ring would be  -N-C-C-O- ) and the end of the oxygen and the nitrogen would bond to the Nickel and then the Nitrogen would bond with another carbon onto another ring (since nitrogen can form 3 bonds)

Anyways, this is a crude picture that I could come up with.
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Offline CopperSmurf

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Re: Point Groups
« Reply #3 on: November 18, 2007, 10:29:19 AM »


Sorry can't seem to upload the pic properly.
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Offline CopperSmurf

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Re: Point Groups
« Reply #4 on: November 18, 2007, 10:40:22 PM »
Ok, it would look like this pic on the right side of the page, except replace the M with Ni.
http://en.wikipedia.org/wiki/Chelation
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Offline hmx9123

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Re: Point Groups
« Reply #5 on: November 19, 2007, 04:36:12 AM »
Casually looking at it, I'd guess Ci, but I've never been that great with point groups.  There are free molecular modeling programs out there.  Use Google.  You also need to get an inorganic chem textbook and find the section on point groups.
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Offline Yggdrasil

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Re: Point Groups
« Reply #6 on: November 23, 2007, 02:05:55 PM »
I don't know if there's a center of inversion in the molecule.  Based on the wikipedia picture, I'd say C2, with the 2-fold axis going through the metal and the middle of the N-N bond.
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Offline hmx9123

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Re: Point Groups
« Reply #7 on: November 25, 2007, 12:53:03 AM »
I was never great at point groups, and I didn't give this much thought.  I have trouble seeing the two-fold axis between the nitrogens, but perhaps I'm not visualizing that correctly.  It's been a long time since I did this stuff.
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