The CHARMM forums have plenty of posts on this topic, so I would advise you to look there; parameters should be available. A bit of Googling also turned up several references, for instance http://pubs.acs.org/doi/abs/10.1021/ct800342w.

1stly you may generate the molecule using molden (or any other software) and save it in mol2 format. Using this and swissparam (http://www.swissparam.ch/) web server u can finally get the charmm compatible parameter and topology files. Hope I could help.

Dear Ricardo,

You can use MCPB module of amber tools package for metal center parameters.it is free and accurate !!

more information in :

http://ambermd.org/doc12/AmberTools13.pdf

HAH

I appreciate you all taking the time to help me, thanks. I already have the molecule in pdb format since we generated it by x-ray crystallography, and therefore I have all the experimental values of bonds and angles, that should speed up the process, I hope!