Subject: Re: CCL:M:MOPAC parameters for samarium

From: [email-masked] (Tom Cundari)
Date: Fri, 05 Sep 1997 13:26:30 -0600

>Does anyone know of a source for samarium MOPAC 6.00 parameters?
>
>  Thanks.
>
>Jim Gano

Jim,

You may want to check out the following by de Andrade and coworkers.  They
use MOPAC 'sparkles' to get what amounts to an essentially electrostatic
lanthanide-ligand bonding description.  Given the large degree of ionic
bonding in lanthanides, this method works very well when used in the
appropriate circumstances.  Their method is simple, but ingenious.

-  de Andrade, A. V. M.; Longo, R. L.; de Sa, G. F. Theoretical Model for
the Prediction of Electronic Spectra of Lanthanide Complexes.  J. Chem.
Soc., Faraday 1996, 92, 1835 - 1839.

-  de Andrade, A. V. M.; da Costa, N. B.; Simas, A. M.; de Sa, G. F.
Sparkle Model for the Quantum Chemical Calculation of Europium Complexes of
Coordination Number Nine.  J. Alloys & Compds. 1995, 225, 55 - 59.

-   de Andrade, A. V. M.; da Costa, N. B.; Simas, A. M.; de Sa, G. F.
Sparkle Model for the Quantum Chemical AM1 Calculation of Europium
Complexes.  Chem. Phys. Lett. 1994, 227, 349 - 353.

We have extended their technique in my lab to gadolinium.  The following
was just published & is a
combined theory-experiment study.

-  Benson, M. T.; Cundari, T. R.; Lutz, M. L.; Sommerer, S. O. Effective
Core Potential Approaches to Computational Inorganic Chemistry.  in
"Reviews in Computational Chemistry;" D. Boyd; K. Lipkowski (Eds.) 1996, 8,
145 - 202.

We're in the process of preparing a short note (which I would be more than
happy to send to you once it is submitted) discussing some of our
observations on the use of this technique.  The paper discusses when the
method works (typically, cationic complexes with hard donor ligands & large
coordination numbers) and when it does not (typically, anionic complexes
with soft donor ligands & small coordination numbers).   This work was done
primarily by one undergraduate in collaboration with a former Ph.D. student
Mike Benson who was doing experimental research on Gd(III) coordination
complexes as part of his dissertation.    Given the similarity in bonding
across the lanthanide series I would imagine the approach of de Andrade and
coworkers may very well be extendable to samarium.

Good luck with the calcs.  I'd be interested to know how they turn out
should you
decide to give 'em a try.

Sincerely,

Tom Cundari

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Tom Cundari                                           Department of Chemistry
Associate Professor                                The University of Memphis
e-mail:[email-masked]           Memphis, TN 38152-6060
phone: 901-678-2629
FAX: 901-678-3447
http://www.chem.memphis.edu/umchem.html

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