Date: Mon, 8 May 2006 17:20:24 +0200 (CEST)

From: Pavel Hobza <pavel.hobza@uochb.cas.cz>

To: E. Arunan <arunan@ipc.iisc.ernet.in>

Subject: Re: IUPAC

Dear Arunan, I read materials you sent me with interest but I have some

problem with definition of H-bond. Definition of the X-H...Y H-bond should

include the fact that X-H length and X-H vibration frequency is modified

upon formation of the bond. If this is not considered we have London

interaction as defined in materials.

If the length of X-H is not changed upon formation of the complex we have

vdW or London interaction. If they are changed (bond length stretched or

contracted, vibration frequency red or blue shifted) we have H-bonding. I

am convinced that this feature is for H-bonding unique and essential...

Best wishes, Pavel