Re: ORGLIST: Circular dichroism problem

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From: Jacob Zabicky (zabicky$##$bgumail.bgu.ac.il)
Date: Tue Aug 07 2001 - 07:35:22 EDT


Hello Ashis

This is only tentative, and I have to confirm it with more knowledgable
colleagues who are vacationing at present. It is possible to imagine a
crystalline complex where heavy element ions form a monoclinic lattice of
the type you mention, while the organic ligands occupy more general
positions in the crystal. Due to the lower electron density in the organic
regions, it is probably the heavy atoms that effectively determine the
space group of the crystal, despite the lack of strict symmetry of the
organic part.

All the best,

Jacob

At 14:15 6/8/1, J.Aires de Sousa wrote:
>-------- Original Message --------
>From: A De <ocad$##$mahendra.iacs.res.in>
>To: "Dr J.a.deSousa" <jas$##$mail.fct.unl.pt>
>
>
>
>Can any one suggest?
>
>Recently, I synthesized a water soluble
>polymeric coordination compound. X-ray
>crystallography has established this molecule
>to have a single stranded helical structure
>with centrosymmetric space group, P21/c
>(No. 14), Z = 4. In solution (water or
>methanol as solvent) the same compound
>shows circular dichroism (CD active).
> My question is whether a molecule
>with centrosymmetric space group in the
>crystalline state can be CD active in solution?
>It is expected that a centrosymmetric crystal
>will produce the right-handed and left-handed
>helicates in identical number and the solution
>of such crystal will be a recimic mixture.
> Thank you for your atention in advance.
>
> Sincerely,
> Ashis De

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Prof. Jacob Zabicky
Institutes for Applied Research
Ben-Gurion University of the Negev Private: POB 12366, Beer-Sheva 84863
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