Subject: Carbene calculations summary

From: James Pugh <[email-masked]>
Date: Tue, 6 Oct 1998 10:38:33 -0700 (PDT)

Dear CCL, 

Thank you for all the responses.  It will certainly help our progress
here.  Enclosed is the original message followed by all replies.

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> Dear CCL,                        
> 
> Our lab is heavily involved in the computational study of carbenes (both
> singlet and triplet) and related diradicals. Currently, we are using the
> b3lyp/6-311+g(3df,2p)//b3lyp/6-31g(d,p) method.  Our calculations show
> this to give nice agreement to experimental data for the singlet-triplet
> gap of methylene carbene.  In searching the literature there are several
> examples of other groups also using DFT methods for carbenes.  But there
> are probably just as many using a multiconfigurational self consistent
> field method (MCSCF or CASSCF in Gaussian).  My question is a follows:
> 
> Does anyone else have experience with similiar calculations and more   
> importantly - which method would be the preferred or more correct
> approach.
> 
> Any assistance would be greatly appreciated.  I will summarize all     
> responses.
> 
> Jim Pugh                        
> Freeman Research Group                             
> Department of Chemistry         
> Oregon State University
> e-mail: [email-masked]          

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From: "Christopher J. Cramer" <[email-masked]>
To: James Pugh <[email-masked]>  
Subject: Re: CCL:carbene calculations

We've done rather a lot in this area. Rather than recapitulate the whole
ouevre, I would just point you to our latest comprehensive work in this
area. See
                                                                         
Worthington, S. E.; Cramer, C. J. "Density Functional Calculations of the
Influence of Substitution on Singlet-Triplet Gaps in Carbenes and
Vinylidenes" J. Phys. Org. Chem. 1997, 10, 755.
                                                                         
which, in addition to being on topic vis a vis DFT for carbenes, contains
references to several papers we (and others) have published comparing DFT
to CASPT2 for carbenes and isoelectronic systems.
                                        
CJC

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From: [email-masked]               
To: "James Pugh <[email-masked]>" <[email-masked]>                     
Subject: Re: CCL:carbene calculations

Dear James,

We have been doing a LOT of carbene studies with various DFT
approaches, also comparing them to MRCI and CAS(SCF and MP2).
You can find the relevant articles in:

Carbenes: A Test Ground for Electronic Structure Methods. Holger F.Bettinger,
Peter R. Schreiner,* Paul von Rague Schleyer, and Henry F. Schaefer III;
in "The Encyclopedia of Computational Chemistry" Paul v. Ragu^N Schleyer,
Norman L. Allinger, Tim Clark, Johann Gasteiger, Peter A. Kollman, Henry F. 
Schaefer III, and Peter R. Schreiner (Eds.), John Wiley & Sons Inc.;
Chichester, 1998, in press.

(the encyclopedia was published this week)

And a full book chapter on the same topic:

Computational Analyses of Prototype Carbene Structures and Reactions.
Holger F. Bettinger, Paul von Rague Schleyer, Peter R. Schreiner,* and
Henry F. Schaefer III; in "Modern Electronic Structure Theory and
Applications to Organic Chemistry," Ernest L. Davidson (Ed.), World
Scientific Press Inc.; Singapore 1997, pp 89-171;  (ISBN: 981-02-3168-7)

And several papers with benchmarks and comparisons:

The Topomerization of Benzene. Holger F. Bettinger, Peter R. Schreiner,
Paul von Rague Schleyer,* and Henry F. Schaefer III J. Am. Chem. Soc.
1998, 120, 5741-5750.

Substituted Cyclopropylidenes and Cyclic Allenes. Holger F. Bettinger,
Paul von Rague Schleyer,* Peter R. Schreiner, and Henry F. Schaefer III J.
Org. Chem. 1997, 62, 9267-9275. 

The Naphthylcarbene Potential Energy Hypersurface. Yaoming Xie, Peter R.
Schreiner,* Paul von Rague Schleyer, and Henry F. Schaefer III J. Am.
Chem. Soc. 1997, 119, 1370-1377. 

The Ring Opening of Cycopropylidene and the Internal Rotation of Allene.
Holger F. Bettinger, Peter R. Schreiner, Paul von Rague Schleyer,* and
Henry F. Schaefer III* J. Phys. Chem. 1996, 100, 16147-16154.

And here you find a nice table for methylene and various levels:

Carbene Rearrangements Unsurpassed: The C7H6 Potential Energy Surface
Revealed. Peter R. Schreiner,* William L. Karney, Paul von Rague 
Schleyer,* Weston T. Borden,* Tracy P. Hamilton, and Henry F. Schaefer III
J. Org. Chem. 1996, 61, 7030-7039.

The groups around Wentrup, McMahon, and Borden also have been doing a lot
of work along these lines. All published in JACS and JOC.

Hope this helps,
Peter

    ////
___|--00___________________________________________________________________
   C   ^     Dr. Peter R. Schreiner             http://www.gwdg.de/~pschrei
    \ ~/     Institut fuer Organische Chemie    
    <><>     Georg-August Universitaet Goettingen
             Tammannstr. 2                         Phone: +49-(0)551-393287
             D-37077 Goettingen, Germany           FAX:  +49-(0)551-399475
___________________________________________________________________________

From: "Wang, Lifeng" <[email-masked]>
To: "[email-masked]'" <[email-masked]>     
Cc: "[email-masked]'" <[email-masked]>
Subject: b3lyp method                        
                                          
Yes. b3lyp is a very good method. I choose it for my calculation.
a reference if you are interested:        
                                         
             J.Phys.Chem.B 1998,102,5152-5157
                           p 5153  
                           l 9-15 
                                   
Li-Feng Wang                       
[email-masked]               

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From: "Preston J. MacDougall" <[email-masked]>
To: [email-masked]                              
Subject: correlation in carbenes   
                                             
James,                                    
   While we did not use DFT, my colleagues and I explored the effect of
other standard correlation techniques on the local properties of carbenes,
especially the atomic properties (as defined by the quantum theoespecially
the atomic properties (as defined by the quantum theory of atoms
in molecules).  The reference is J. Chem. Phys., vol. 88, p. 3792 (1988).
                                   
Sincerely,                        
                                   
Preston J. MacDougall              
                                
Preston J. MacDougall                   
Assistant Professor               
Department of Chemistry, Box X101                    
Middle Tennessee State University 
Murfreesboro, TN 37132

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From: Ivan Rossi <[email-masked]>
To: James Pugh <[email-masked]>                 
Subject: Re: CCL:carbene calculations

Chris Cramer of University of Minnesota published some papers on the
subject in which he compares the performance of the methods too. 
Check his web page for a list of his publications.

http://pollux.chem.umn.edu/~cramer

--
Dr. Ivan Rossi - CIRB Biocomputing Unit
e-mail: [email-masked]  WWW: http://www.biocomp.unibo.it/ivan

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From: "Eric V. Patterson" <[email-masked]>
To: James Pugh <[email-masked]>                 
Subject: Re: CCL:carbene calculations
                                             
James,                                    
                                             
In my work with Bob McMahon at Wisconsin, and Chris Cramer at Minnesota, I
have used a large number of methods to study carbenes and relatehave used
a large number of methods to study carbenes and related systems.
These methods have included DFT, CCSD, CCSD(T), CAS and CASPT2.  My
conclusions might be summarized as follows:  For "well-behaved" systems
(i.e. mostly single-reference), all methods show good agreement.  For
modestly multi-reference systems, a gradient-corrected DFT functional with
NO HF exchange performs well when compared to CCSD(T) and the MC methods.
When things get significantly multi-reference, only CAS seems to be
trustworthy.  CCSD(T) does an okay job, but CASPT2 blows it,
sintrustworthy.  CCSD(T) does an okay job, but CASPT2 blows it, since it
is just perturbation theory.  Unfortunately, MRCI may the best option in
those cases, but it's soooo expensive.                     
                                  
I would be a little leary of relying on B3LYP.  The HF exchange could trip
you up if your system is even modestly multi-reference.  But, if you have
systems which are well described by a single reference, I see nothing
wrong with your approach.  It's certainly cheaper than the alternatives,
and the evidence is that the results hold up well versus both experiment
and higher-level calcs.

Regards,
Eric

From:                                                               
                   
Eric V. Patterson         voice:  (515) 269-4543                   
Assistant Professor       FAX:    (515) 269-4285
Grinnell College
Department of Chemistry   Room 2030, Science Bldg.
P.O. Box 805              [email-masked]
Grinnell, IA 50112        http://www.grinnell.edu/individuals/patterse

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From: [email-masked] 
To: [email-masked]                                                   
Subject: Re: CCL:carbene calculations
                                                                          
Jim:  I recommend that you send your message to a professor
at Univ. Wisconsin.  He will be happy to talk with you
regarding high level calcs. on carbenes.  He has done those
kind of calcs.  He reads his e-mail regularly and you
can mail him at [email-masked].  His name is
Robert McMahon and is a professor of organic chemistry.
                                  
I am not in the carbene field, but I happen to know Bob
McMahon personally and I know if he cant answer your
question, he can tell you exactly where to go to find out.
                                        
Kent Stewart                      
Abbott Laboratories                                                      

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