Subject: Re: CCL:coordination compounds in MM3

From: Per-Ola Norrby <pon [] kemi.dtu.dk>
Date: Thu, 30 Jun 2005 16:35:51 +0200

Dear Jeny,

>I want carry out some calculation on a metal-porphyrin coordination
>compound using MM3 force field. From MM3 manual, there should be two
>modification (1,3-electron pair repulsion and bending parameter
>adjustment). However, I didn't find what special commands I should use to
>indicate those coordinate bonds (eg. in conjugated systems we have to
>specify those pi atoms). Would anyone who is familiar with MM3 tell me
>what kind of special treatment I should apply to the coordination
>compound?

	It depends on which implementation of MM3 you're using, they 
all differ.  If it's the original MM3 program from Allinger, then the 
atom type determines if it is a coordination center.  If it is, any 
bond to it counts as a coordination bond.

	In addition to the bending parameters, for optimal results 
you should also specifically parameterize the bond lengths, but if 
you're using MM3(96) (or later), I believe you'll get rough guesses 
> from the parameter estimator, that will serve for quick-and-dirty 
calculations.

	You didn't write your name, but I think I recognize the email 
address, haven't we been in contact before?

	Best regards,

	Per-Ola Norrby
-- 
Per-Ola Norrby, Assoc. Professor, http://organisk.kemi.dtu.dk/PON/
Technical University of Denmark, Department of Chemistry
Building 201, Kemitorvet, DK-2800 Kgs. Lyngby, Denmark
Email: pon [] kemi.dtu.dk  tel +45-45252123,  fax +45-45933968